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Inspection of defects of composite materials in inner cylindrical surfaces using endoscopic shearography
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Optics and Lasers in Engineering 000 (2017) 1–9
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Optics and Lasers in Engineering journal homepage: www.elsevier.com/locate/optlaseng
Review
Inspection of defects of composite materials in inner cylindrical surfaces using endoscopic shearography Fabiano Jorge Macedo a, Mauro Eduardo Benedet a,∗, Analucia Vieira Fantin a, Daniel Pedro Willemann b, Fábio Aparecido Alves da Silva a, Armando Albertazzi a a b
Laboratório de Metrologia e Automatização, Universidade Federal de Santa Catarina – UFSC, CEP 88040-970, Florianópolis, SC, Brazil Universidade do Estado de Santa Catarina – UDESC/CERES, CEP 88790-000, Laguna, SC, Brazil
a r t i c l e
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Keywords: Endoscopic shearography Composites materials inspection Radial sensitivity interferometer
a b s t r a c t This work presents the development of a special shearography system with radial sensitivity and explores its applicability for detecting adhesion flaws on internal surfaces of flanged joints of composite material pipes. The inspection is performed from the inner surface of the tube where the flange is adhered. The system uses two conical mirrors to achieve radial sensitivity. A primary 45° conical mirror is responsible for promoting the inspection of the internal tubular surface on its 360° A special Michelson interferometer is formed replacing one of the plane mirrors by a conical mirror. The image reflected by this conical mirror is shifted away from the image center in a radial way and a radial shear is produced on the images. The concept was developed and a prototype built and tested. First, two tubular steel specimens internally coated with composite material and having known artificial defects were analyzed to test the ability of the system to detect the flaws. After the principle validation, two flanged joints were then analyzed: (a) a reference one, without any artificial defects and (b) a test one with known artificial defects, simulating adhesion failures with different dimensions and locations. In all cases, thermal loading was applied through a hot air blower on the outer surface of the joint. The system presented very good results on all inspected specimens, being able to detect adhesion flaws present in the flanged joints. The experimental results obtained in this work are promising and open a new front for inspections of inner surfaces of pipes with shearography. © 2017 Elsevier Ltd. All rights reserved.
1. Introduction The advancement of new technologies has leveraged the development of composite materials and increases the demand for new materials with special characteristics and properties not found in ceramics, metal alloys and conventional polymeric materials. These new materials can combine properties such as high stiffness, low density and high impact and corrosion resistance [1] what have increased the interest of the oil and gas industry in the use of these materials, mainly in pipes manufacturing processes [2]. The most used materials for composite material pipes are glass fiber associated with a thermoset polymer resin. These composite tubes are used in the onshore and offshore petrochemical industry for the transportation of a wide variety of fluids with low and high pressure levels, including hydrocarbons [3,4]. These composite material pipes require special treatment with respect to their ends where others pipes, valves and equipment are connected. The most commonly used assembly types
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in composite pipes are bell and spigot joints, laminate and flanged which depends on the kind of service the pipeline will be exposed to. The use of these composite material pipes brings many benefits, but it is important to take some precautions since the bonded joints are subject to defects that can lead to premature failure. Failures can occur mainly due to the following defects: cracks, porosities, lack of adhesive and lack of adhesion [2,5]. Considering the previous mentioned defects, this work highlights the detection of lack of adhesion in flanged joints. Flanged joints are used in the connection between pipes and valves or other equipment where an easy disassembly is required. Unlike metallic pipes, where the flange is welded to the pipe end, in composite materials the flange is attached to the pipe by the application of adhesives which give the joint rigidity after its cure. In the literature, the only test cited for evaluating flanged joints is the pressure test (or hydrostatic test) [6] which mostly detects the presence of defects such as lack of adhesive, poor adhesive cure, manufacturing defects in the piping fittings and leakages.
Corresponding author. E-mail addresses: [email protected], [email protected] (M.E. Benedet).
http://dx.doi.org/10.1016/j.optlaseng.2017.06.005 Received 3 April 2017; Received in revised form 22 May 2017; Accepted 6 June 2017 Available online xxx 0143-8166/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article as: F.J. Macedo et al., Optics and Lasers in Engineering (2017), http://dx.doi.org/10.1016/j.optlaseng.2017.06.005
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In the last decades, shearography has become an important diagnostic tool, particularly in the field of nondestructive testing [7-10] and, this optical technique is particularly effective in revealing delaminations in composite structures [11,12]. Since its first demonstration [13], speckle shearing interferometry, or shearography [14], has offered some advantages in comparison to other interferometric techniques such as the well-known Electronic Speckle Pattern Interferometry (ESPI) [15,16]. Its main advantage concerns to the optical configuration that is more resilient to environmental disturbances and vibrations. The use of shearography with lateral sensitivity for inspections on internal surfaces is already a subject referenced by some authors. A good example is the internal inspection of retreaded tires [17]. In this configuration, the system is positioned inside the tire and the system rotates continuously acquiring a sequence of laterally displaced images. These images are combined after the process generating a panoramic view of the inner inspected surface of the tire. A significant feature of this configuration is the high cost of implementing this system and it is also not applicable to small diameters such as the inspection of flanged joints. Another approach uses a borescope adapted to a typical shearography interferometer for the inspection of internal surfaces of composite material pressure vessels. That strategy results in a simple system but faces instability due to the movement of rotation necessary for the complete inspection of the inner surface [18]. In addition, the shearography with radial sensitivity for inspection of internal surfaces is an even rarer subject in the literature. An interesting configuration utilizes two prisms of right angle and allows the radial displacement between the images [19]. However, this alternative generates a variable radial sensitivity which starts with zero shear at the image center and increases until a maximum at the image periphery. Others authors do not mention the radial shear for shearography applications but they present alternatives where combinations of plane and curved mirrors are used to generate the radial shear [20]. The internal inspection of flanged joints used in the oil and gas industry then motivated the development of the new endoscopic configuration of shearography by using conical mirrors. The mechanical structure of the flanged joints itself has a large wall thickness of composite material over the bonding zone. In this way, the optical inspection by the inner surface of the tube becomes more convenient and feasible, where the thickness up to the adhesion zone is much smaller. This paper proposes a new endoscopic configuration of shearography for inner inspection of tubes. Section 2 details the optical configuration and its peculiarities. Section 3 presents the results obtained with a well-known specimen, in order to validate the technique and the results obtained with two flanged joints. The last section presents the authors’s comments and conclusions about the new configuration, as well as expectations for future works.
Fig. 1. Image generated by a conical mirror.
divides its wave amplitude by half and directs 50% of the light to a flat mirror. The remaining 50% are sent to the secondary conical mirror. The secondary conical mirror generates an image radially sheared from that reflected by the flat mirror and, after this, the reflected waves through both mirrors interfere on the camera sensor. This resulting interference is composed by two overlapping and radially sheared images. The laser used in this application is a 532 nm DPSS laser with 1 W power, model SAMBA manufactured by COBOLT. An USB3 camera with a 2 Megapixel CMOS sensor, model FLEA3 manufactured by PoinGrey, was used to grab the interference images. Fig. 3 shows another schematic representing how lines would be visualized by the system positioned inside the tube. Each point on the inspected internal cylindrical surface results in two separate points by a distance 𝛿r in the interference image. The red lines represent the image formed by the flat mirror which has no shear. In turn, the blue lines represent the image formed by the reflection of the secondary conical mirror which is the image radially sheared with the quantity 𝛿r. For this special configuration, the conicity of the secondary conical mirror was defined from simulations, in order to generate a radial displacement of about 10 mm. In conventional shearography, 10 mm is a typical lateral displacement value. Then it was the goal during the design of the optical arrangement. Besides, the optical distance between the system and the inner surface of the pipe (working distance) changes the amount of radial shearing. Bigger this working distance, bigger the radial displacement. In this work, the radial displacement ranged from 8 to 10 mm because the specimens used in the experiments have slightly different inner diameters. The tip of the conical mirror causes a great resolution reduction on the acquired image where no relevant information can be attained. In order to illustrate this difficult, the effective image area utilized by the camera sensor is illustrated in Fig. 4a and, in addition, Fig. 4b shows an actual image captured by the radial system where a sheet of graph paper has been positioned inside a tube. However, the image generated by the radial system results in concentric circles and radial lines with constant radial shear. Fig. 4b also shows three blind lines in the image reflected by the conical mirror. These dark lines are resulting from the three rods that compose the mechanical support of the primary conical mirror. The rods are positioned at 120° of each other and make the mirror fixation quite rigid. In the actual system the blind lines may disturb the measurement, since eventually they could hide some defects. However the next step of this work is build a more compact and portable system, and this system could be rotated inside the tube to measure in many angular positions. Thus, two overlapping measurements can be combined to avoid the blind regions.
2. Endoscopic shearography: a special shearography interferometer 360° vision systems are already widely studied and consist of a mirror with specific geometry where the camera is placed in front of it. This camera visualizes the 360° images of the environment in polar coordinates. When the image of an environment is visualized by a conical mirror vertical lines are seen as radial in the plane of the image, just as horizontal lines are seen as arcs. These characteristics are illustrated in Fig. 1. The proposed arrangement for the special shearography interferometer with radial sensitivity is based on the use of two conical mirrors: a 45° primary conical mirror to visualize the internal surface to be inspected, and a secondary 89° conical mirror responsible for the radial displacement on the sheared image. Both mirrors were custom made for this application. The proposed configuration is shown in Fig. 2. The laser light is scattered by the pipe inner wall and then directed to the primary conical mirror. The primary mirror reflects the light to a beam splitter which 2
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Fig. 2. Radial sensitivity interferometer setup.
3. Experimental results: discussion and analysis 3.1. Validation tests In order to evaluate the developed shearography system, two specimens with well-known characteristics have been tested. Both specimens made of a steel tube were internally coated with fiberglass composite material. 3.1.1. Specimen 1 The first specimen, named as CP1, measures 152 mm of external diameter and 148 mm of internal diameter. A composite coating of about 3 mm in thickness was applied to its inner surface. A 7 mm diameter hole has been drilled on the pipe wall and a micrometric screw was attached to allow the application of controlled mechanical loading from the outside directly into the composite material. The mechanical loading pushes the composite coating away from the steel inner surface to simulate an adhesion flaw. Fig. 6a shows the specimen CP1 and Fig. 6b
Fig. 3. Schematic drawing of an image generated by the radial shearography system. (For interpretation of the references to color in the text, the reader is referred to the web version of this article.)
Fig. 5a shows the 3D CAD models of the conical mirror and its three rods support. Fig. 5b shows the complete configuration design of the special shearography interferometer with radial sensitivity.
Fig. 4. Radial shearography system image: (a) Schematic of the effective image area utilized by the camera sensor; (b) Acquired image.
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Fig. 5. (a) Support of the primary conical mirror; (b) Optical configuration of the endoscopic shearography system.
Fig. 6. (a) Specimen 1 - CP1; (b) Threaded holes to attach the micrometric screw and through hole used to apply the mechanical loading.
details the two threaded blind holes for attaching the micrometric screw and the through hole for mechanical loading application. The mechanical loading produced by the micrometric screw resulted in very clear interference fringes, what allowed us to make some controlled inspections to analyze the system behavior. Two different sections of CP1 have been inspected: Section 1 at the upper specimen position and Section 2 at the lower specimen position. The micrometric screw applied a displacement of approximately 1 μm towards the center of the tube in both inspections. The Fig. 7 shows the difference phase maps of shearographic inspections for both sections. Besides the blind zones caused by the conical mirror support, the CP1 images still contains a fourth blind zone, highlighted on Fig. 7a. The external diameter of CP1 is smaller than the inner diameter of flange, so a new support has been built to adapt the CP1 to the test bench previously assembled to the flanged joints experiments. The new support imposed a barrier to the laser illumination, preventing the formation of speckles in this area and resulting in the blind zone on image. The Fig. 8 shows the stitching of the inspection results of Sections 1 and 2, after a mathematical transformation from polar to rectangular coordinates. The result is the complete defect map. The x-axis regards the angular position on tube, and y-axis regards the axial position on tube.
vious specimen, CP2 has a 3 mm thick inner layer of the same composite material. A 500 W halogen lamp was used to apply the thermal loading for CP2 inspection. The reference phase map with the specimen at room temperature was acquired, and then the second map was taken after heating the specimen for 10 s. In order to detect all inserted defects, four different positions in the axial direction of CP2 were measured. The measured sections were processed and overlapped to make easier the phase difference maps stitching. Fig. 10 shows the four original phase difference maps acquired during this experiment. Fig. 11 shows the overlap of the four measured sections after a transformation from polar to rectangular coordinates. The resulting map clearly shows six artificial defects inserted in CP2. Only the smallest defect, the through hole with 5 mm in diameter, was not detected. Its position is highlighted by an arrow and a white circle in the Fig. 11.
3.2. Flanged joints experiments In this section, two flanged unions made of composite material and 150 mm of nominal diameter were inspected: specimens 3 and 4. The specimen 3 (CP3) contains no defects and has been used as reference for the shearography images. In turn, specimen 4 (CP4) is the one that contains the artificially inserted defects. A thermal blower positioned about 50 mm from the upper face of the flange performed the loading for the radial shearography inspection. The hot gun was moved circularly to evenly heat the adhesion zone.
3.1.2. Specimen 2 The second specimen, identified as CP2, measures 170 mm of external diameter and 7 mm in the steel wall thickness. This specimen contains five through holes and two through slits positioned around the entire perimeter to simulate real defects, as shown in Fig. 9. As the pre4
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Fig. 7. Phase difference maps of CP1 due to a displacement of 1 μm: (a) Section 1: upper tube position; (b) Section 2: lower tube position.
Fig. 8. Stitching of the inspection results of Sections 1 and 2 in rectangular coordinates.
The tests results showed that the heating time required for interference fringes start occurring in each section varies according to the depth of the adhesive zone in relation to the upper face of the flange. The heating time required for Section 1 is considerably less than the heating time required for inspection of Section 3 which is the furthest away from the tube end. The heating time interval of 15 to 20 seconds was used for Section 1 while a range of 40 to 50 seconds to Section 2. Section 3 was heated with range from 60 to 70 seconds.
3.2.1. Specimen 3: flanged union without defects CP3 is a flanged composite joint with no internal flaws which has been used as reference for comparison with CP4 that has several defects artificially inserted. Three axially displaced sections were inspected in the inner surface of CP3 and the radial shearography results are shown in Fig. 12. Analyzing the generated results, we can note that a set of uniform and relatively concentric fringes appear in each inspected section. The irregularities in the spacing between fringes can be explained by the applied thermal loading since the upper section of the flange undergoes more heating than the lower section. We can also observe in Fig. 12a that some discontinuous fringes appeared. These fringes correspond to a small area located a few millimeters after the end of the adhesion zone and some fringes arise quite irregularly because the expansion of the tube in this area is not anymore limited by the flange.
Fig. 9. 3D CAD model of Specimen 2 (CP2) with artificial defects.
Three sections in the axial direction of the joints were inspected in order to thoroughly examine the adhesion zone. Following the same inspection procedure used to CP2, we performed the measurements by acquiring the first phase map at room temperature. A new phase map was acquired after heating the specimen in order to obtain the final phase difference map. 5
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Fig. 10. Phase difference maps of CP2: (a) Section 1, (b) Section 2, (c) Section 3 and (d) Section 4.
Fig. 11. Defect maps in rectangular coordinates. X-axis regards the angular position on tube and Y-axis regards the axial position on tube.
We transformed the images into rectangular coordinates and then did the overlapping of the three sections in order to observe the uniformity of the fringes. The result in rectangular coordinates is shown in Fig. 13. After the coordinates transformation, it is possible to observe more clearly the uniformity of the fringes in the adhesive area. Fig. 13 shows fringes practically horizontal and regularly distributed. Consequently, this fringes pattern can be used as reference pattern for a flanged joint without flaws. Different patterns will be compared next.
ing, distance between the union and the blower and others. Fig. 16 shows the results in polar coordinates. Again, for a better analysis, the images were transformed into rectangular coordinates and the sections overlapped and Fig. 17 shows the results. The phase difference maps generated in the inspections of CP4 clearly show the presence of discontinuities (or anomalies) in the fringe patterns, indicating the presence of three defects in this specimen. The presence of defects in this specimen is even more evident by comparing Fig. 17 with the phase difference maps of the specimen without defects (Fig. 13). With the objective of giving even more highlight to the defects found, the phase difference maps of CP4 and CP3 have been subtracted from each other and the resulting images are shown in Fig. 18. The shearography maps subtraction allowed the partial removal of the sets of parallel horizontal fringes present in both images. In the resultant maps, defects 1 and 3 can be seen with greater clearness at Sections 2 and 3, and defect 2 is best noticed at Section 1.
3.2.2. Specimen 4: flanged union with artificial defects In the manufacture process of specimen 4 (CP4), the composite tube and its flange were joined using specific adhesive and following to the assembly specifications of the manufacturer. To simulate the lack of adhesion between the surfaces of the tube and the flange, three 0,5 mm thick Teflon® patches with different dimensions were inserted, as shown in Fig. 14. The variation of the patches dimensions helped to analyze the capacity of flaws detection of the radial shearography system. These artificial defects are located at 90° from each other, thus, there are also some adhesive zones with no defects. Fig. 15 shows CP4 after the flange union. In the inspection of this specimen, the same parameters of the previous inspection were used: heating times, analyzed sections, laser light-
4. Conclusions This work presented a proposal and the validation of a special shearography system with radial sensitivity and explored its applica6
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Fig. 12. Phase difference maps of specimen 3 (CP3): (a) Section 1, (b) Section 2 and (c) Section 3.
Fig. 13. Phase difference maps of specimen 3 in rectangular coordinates and overlapping of sections. Fig. 15. Specimen 4 after insertion of defects.
The optical system with conical irrors is capable to visualize all 360° of the inner section of the tube with just one image. However, it has just the radial sensitivity direction and the quantity of the radial displacement is not (or almost not) adjustable. The radial displacement of the proposed arrangement is given by the conicity of the secondary conical mirror. Besides, the optical distance between the system and the inner surface of the pipe (working distance) changes the amount of radial shearing. Bigger this working distance, bigger the radial displacement. The main advantage of this radial configuration, when compared to others in the literature, is that the radial displacement is constant through the image, so the sensitivity is unique for all regions of image. For this application the optical setup was designed to achieve a radial displacement of about 10 mm which is a typical lateral displacement value used to shearography inspections. In this work, the radial displacement ranged from 8 to 10 mm because the specimens used in the experiments have slightly different inner diameters. The fixed value for the radial displacement can be considered a limitation of this configuration, however there are other advantages that overcome it.
Fig. 14. Artificial defects inserted in CP4: 30 × 60 mm2 ; 15 × 15 mm2 ; 85 × 30 mm2 .
bility for detecting adhesion flaws on internal surfaces of flanged joints of composite material pipes. The new shearography system uses two conical mirrors to achieve radial sensitivity.
Fig. 16. Phase difference maps of CP4: (a) Section 1, (b) Section 2 and (c) Section 3.
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Fig. 17. Phase difference maps of CP4 in rectangular coordinates and sections overlapping.
be developed with the purpose of compacting and toughing the radial shearography system in order to be applied in pipe shops and other sectors of the oil and gas industry. Acknowledgments Authors would like to express thanks to Petrobras and CNPq - National Council for Scientific and Technological Development for the financial support for the development of this research. References [1] Callister WDJ, Rethwisch DG. Materials science and engineering: an introduction. 8th ed. USA: John Wiley and Sons; 2009. ISBN 978-0470419977. [2] Ameron. Corrosion-resistant fiberglass piping systems; 1998. Texas. [3] Associação Brasileira de Normas Técnicas. NBR ISO 15921: Indústrias de Petróleo e Gás Natural — tubulação de compósito - Parte 1: vocabulário, símbolos, aplicações e materiais, Rio de Janeiro, 2011. [4] Gibson AG. The cost effective use of fibre reinforced composites offshore. United Kingdom: HSE Books; 2003. [5] Adams RD, Cawley P. A review of defect types and nondestructive testing techniques for composites and bonded joints. NDT Int 1988;21(August):208–22. [6] Associação Brasileira de Normas Técnicas. NBR 15921-4: Indústrias de Petróleo e Gás Natural - tubulação de Compósito - Parte 4: fabricação, montagem e operação, Rio de Janeiro, 2011. [7] Hung YY. Shearography for non-destructive evaluation of composite structures. Opt Laser Eng 1996;24:161–82. [8] Hung YY. Applications of digital shearography for testing of composite structures. Composites B 1999;30:765–73. [9] Anisimov, A.G., Serikova, M.G., Groves, R.M. Development of the 3D shape shearography technique for strain inspection of curved objects. Imag Appl Opt, 2016. [10] Xie X, Yang L, Xu N, Chen X. Michelson interferometer based spatial phase shift shearography. Appl Opt 2013;52(17):4063–71 v. [11] Hung YY. Shearography: a novel and practical approach for nondestructive testing. J Nondestruct Test 1989;8(2):55–67. [12] Hung, Y.Y. Apparatus and method for electronic analysis of test object, US Patent 4,887,899. 1989. [13] Leendertz JA, Butters JN. An image-shearing speckle-pattern interferometer for measuring bending moments. J Phys E 1973;6:1107–10. [14] Hung YY. Shearography: a new optical method for strain measurement and non-destructive testing. Opt Eng 1982;21:391–5. [15] Hung YY. Digital shearography versus TV-holography for non-destructive evaluation. Opt Laser Eng 1997;26:421–36. [16] Pagliarulo V, Rocco A, Langella A, Riccio A, Ferraro P, Antonucci V, et al. Impact damage investigation on composite laminates: comparison among different NDT methods and numerical simulation. Measure Sci Technol 2015;26:085603. [17] Huber R, Berger R. Shearography in quality assurance and infield service. In: ECNDT - 9th European NDT Conference - Proceedings Mo .2.1.1, September 25-29, Berlin Germany; 2006. [18] Russell SS, Lansing MD. Endoscopic Shearography and Thermography Methods for Non Destructive Evaluation of Lined Pressure Vessels 1997. [19] Ganesan AR, Sharma DK, Kothiyal MP. Universal digital speckle shearing interferometer. Appl Opt 1988;27(Novembro):4731–4 v. [20] Murty MVRK, Shukla RP. Radial shearing interferometers using a laser source. Appl Opt 1973;12(Novembro):2765–7.
Fig. 18. Phase difference maps resulting from maps subtraction (CP3 – CP4).
The ability of the system to detect defects was assessed from tests performed with a steel tube internally coated with composite material and containing a micrometric screw coupled to its outer surface (CP1), allowing the application of a known and static mechanical loading. The results obtained with this specimen showed a good performance of the system in the detection of small deformations imposed to the surface and validated the radial configuration of the shearography system. The specimen CP2 was a steel tube containing five through holes and two through slits distributed along the specimen perimeter to simulate defects. CP2 was also internally coated with composite material. This specimen has been used to evaluate the thermal loading with the endoscopic shearography system. The proposed endoscopic system also inspected two flanged specimens, one without defects (CP3) and another with artificial defects (CP4), both exposed to thermal loading. The radial shearography system was able to detect the three artificially inserted defects of the specimen 4. The results obtained with CP3 were used as reference fringe pattern and helped the identification of the defects of the CP4 and the elimination of fringes not associated to the internal flaws. Since the experiments started in laboratory resulted in very good outcomes, validating the great potential of the system, future works will
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Fabiano Macedo is graduated in mechanical engineering at Federal University of Rio Grande (2014) and master in mechanical engineering with emphasis in metrology and instrumentation (2017) in Federal University of Santa Catarina. Currently works in the Laboratory of Metrology of the School of Engineering at Federal University of Rio Grande. Has experience in the areas of manufacturing and metrology.
Mauro Eduardo Benedet is graduated in control and automation engineering at the Federal University of Santa Catarina (2005), did master in mechanical engineering with emphasis in scientific and industrial metrology (2008) and PhD in mechanical engineering at the same university (2013). Actually works at the LABMETRO (Laboratory of Metrology and Automatization) of the Mechanical Engineering Department of the Federal University of Santa Catarina with research projects in the oil, gas and energy industry. Has experience in the areas of Automation, Instrumentation and Metrology.
Analucia Vieira Fantin finished her studies in applied mathematics by Federal University of Rio Grande do Sul in 1996. She received the MSc in mechanical engineering from the University of Santa Catarina in 1999, and the PhD degree in optical metrology at the same university in 2003. She is researcher in Federal University of Santa Catarina since 2003, acting on subjects like optical metrology and scientific programming. Her research areas include holography, shearography, defectometry, and shape measurement for non-destructive testing.
Daniel Pedro Willemann received the BSc in mechanical engineering from the Federal University of Santa Catarina – UFSC – Florianópolis – Brazil (1999), the master’s degree in scientific and industrial metrology at the same University (2002) and the PhD degree in mechanical engineering from the Università Politecnica delle Marche – Ancona – Italy (2006). From 2006 is a researcher at the Laboratory of Metrology at UFSC. In 2012, he also became a professor at State University of Santa Catarina – UDESC – SC – Brazil. His research is concerned with activities of for the development of shearography as a non-destructive test technique for composite materials inspections.
Fabio A. A. Silva received his BSc in mechanical engineering from the Federal University of Santa Catarina – UFSC – Florianópolis – Brazil (2010) and his MSc at the same University (2016). Actually is a researcher at the LABMETRO (Laboratory of Metrology and Automatization) at UFSC. His research interests include optical metrology, speckle metrology and optical system designs for non-destructive inspection.
Armando Albertazzi received the BSc in mechanical engineering from the Federal University of Bahia – Brazil in 1982, received the master’s degree in scientific and industrial metrology at the Federal University of Santa Catarina in 1984 and the PhD degree in mechanical engineering from the same University in 1989. Since 1987, he is professor at the Federal University of Santa Catarina. His research refers to new optical techniques for non-destructive inspection, combining the principles of optical metrology and image processing.
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Optics and Lasers in Engineering journal homepage: www.elsevier.com/locate/optlaseng
Review
Inspection of defects of composite materials in inner cylindrical surfaces using endoscopic shearography Fabiano Jorge Macedo a, Mauro Eduardo Benedet a,∗, Analucia Vieira Fantin a, Daniel Pedro Willemann b, Fábio Aparecido Alves da Silva a, Armando Albertazzi a a b
Laboratório de Metrologia e Automatização, Universidade Federal de Santa Catarina – UFSC, CEP 88040-970, Florianópolis, SC, Brazil Universidade do Estado de Santa Catarina – UDESC/CERES, CEP 88790-000, Laguna, SC, Brazil
a r t i c l e
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Keywords: Endoscopic shearography Composites materials inspection Radial sensitivity interferometer
a b s t r a c t This work presents the development of a special shearography system with radial sensitivity and explores its applicability for detecting adhesion flaws on internal surfaces of flanged joints of composite material pipes. The inspection is performed from the inner surface of the tube where the flange is adhered. The system uses two conical mirrors to achieve radial sensitivity. A primary 45° conical mirror is responsible for promoting the inspection of the internal tubular surface on its 360° A special Michelson interferometer is formed replacing one of the plane mirrors by a conical mirror. The image reflected by this conical mirror is shifted away from the image center in a radial way and a radial shear is produced on the images. The concept was developed and a prototype built and tested. First, two tubular steel specimens internally coated with composite material and having known artificial defects were analyzed to test the ability of the system to detect the flaws. After the principle validation, two flanged joints were then analyzed: (a) a reference one, without any artificial defects and (b) a test one with known artificial defects, simulating adhesion failures with different dimensions and locations. In all cases, thermal loading was applied through a hot air blower on the outer surface of the joint. The system presented very good results on all inspected specimens, being able to detect adhesion flaws present in the flanged joints. The experimental results obtained in this work are promising and open a new front for inspections of inner surfaces of pipes with shearography. © 2017 Elsevier Ltd. All rights reserved.
1. Introduction The advancement of new technologies has leveraged the development of composite materials and increases the demand for new materials with special characteristics and properties not found in ceramics, metal alloys and conventional polymeric materials. These new materials can combine properties such as high stiffness, low density and high impact and corrosion resistance [1] what have increased the interest of the oil and gas industry in the use of these materials, mainly in pipes manufacturing processes [2]. The most used materials for composite material pipes are glass fiber associated with a thermoset polymer resin. These composite tubes are used in the onshore and offshore petrochemical industry for the transportation of a wide variety of fluids with low and high pressure levels, including hydrocarbons [3,4]. These composite material pipes require special treatment with respect to their ends where others pipes, valves and equipment are connected. The most commonly used assembly types
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in composite pipes are bell and spigot joints, laminate and flanged which depends on the kind of service the pipeline will be exposed to. The use of these composite material pipes brings many benefits, but it is important to take some precautions since the bonded joints are subject to defects that can lead to premature failure. Failures can occur mainly due to the following defects: cracks, porosities, lack of adhesive and lack of adhesion [2,5]. Considering the previous mentioned defects, this work highlights the detection of lack of adhesion in flanged joints. Flanged joints are used in the connection between pipes and valves or other equipment where an easy disassembly is required. Unlike metallic pipes, where the flange is welded to the pipe end, in composite materials the flange is attached to the pipe by the application of adhesives which give the joint rigidity after its cure. In the literature, the only test cited for evaluating flanged joints is the pressure test (or hydrostatic test) [6] which mostly detects the presence of defects such as lack of adhesive, poor adhesive cure, manufacturing defects in the piping fittings and leakages.
Corresponding author. E-mail addresses: [email protected], [email protected] (M.E. Benedet).
http://dx.doi.org/10.1016/j.optlaseng.2017.06.005 Received 3 April 2017; Received in revised form 22 May 2017; Accepted 6 June 2017 Available online xxx 0143-8166/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article as: F.J. Macedo et al., Optics and Lasers in Engineering (2017), http://dx.doi.org/10.1016/j.optlaseng.2017.06.005
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In the last decades, shearography has become an important diagnostic tool, particularly in the field of nondestructive testing [7-10] and, this optical technique is particularly effective in revealing delaminations in composite structures [11,12]. Since its first demonstration [13], speckle shearing interferometry, or shearography [14], has offered some advantages in comparison to other interferometric techniques such as the well-known Electronic Speckle Pattern Interferometry (ESPI) [15,16]. Its main advantage concerns to the optical configuration that is more resilient to environmental disturbances and vibrations. The use of shearography with lateral sensitivity for inspections on internal surfaces is already a subject referenced by some authors. A good example is the internal inspection of retreaded tires [17]. In this configuration, the system is positioned inside the tire and the system rotates continuously acquiring a sequence of laterally displaced images. These images are combined after the process generating a panoramic view of the inner inspected surface of the tire. A significant feature of this configuration is the high cost of implementing this system and it is also not applicable to small diameters such as the inspection of flanged joints. Another approach uses a borescope adapted to a typical shearography interferometer for the inspection of internal surfaces of composite material pressure vessels. That strategy results in a simple system but faces instability due to the movement of rotation necessary for the complete inspection of the inner surface [18]. In addition, the shearography with radial sensitivity for inspection of internal surfaces is an even rarer subject in the literature. An interesting configuration utilizes two prisms of right angle and allows the radial displacement between the images [19]. However, this alternative generates a variable radial sensitivity which starts with zero shear at the image center and increases until a maximum at the image periphery. Others authors do not mention the radial shear for shearography applications but they present alternatives where combinations of plane and curved mirrors are used to generate the radial shear [20]. The internal inspection of flanged joints used in the oil and gas industry then motivated the development of the new endoscopic configuration of shearography by using conical mirrors. The mechanical structure of the flanged joints itself has a large wall thickness of composite material over the bonding zone. In this way, the optical inspection by the inner surface of the tube becomes more convenient and feasible, where the thickness up to the adhesion zone is much smaller. This paper proposes a new endoscopic configuration of shearography for inner inspection of tubes. Section 2 details the optical configuration and its peculiarities. Section 3 presents the results obtained with a well-known specimen, in order to validate the technique and the results obtained with two flanged joints. The last section presents the authors’s comments and conclusions about the new configuration, as well as expectations for future works.
Fig. 1. Image generated by a conical mirror.
divides its wave amplitude by half and directs 50% of the light to a flat mirror. The remaining 50% are sent to the secondary conical mirror. The secondary conical mirror generates an image radially sheared from that reflected by the flat mirror and, after this, the reflected waves through both mirrors interfere on the camera sensor. This resulting interference is composed by two overlapping and radially sheared images. The laser used in this application is a 532 nm DPSS laser with 1 W power, model SAMBA manufactured by COBOLT. An USB3 camera with a 2 Megapixel CMOS sensor, model FLEA3 manufactured by PoinGrey, was used to grab the interference images. Fig. 3 shows another schematic representing how lines would be visualized by the system positioned inside the tube. Each point on the inspected internal cylindrical surface results in two separate points by a distance 𝛿r in the interference image. The red lines represent the image formed by the flat mirror which has no shear. In turn, the blue lines represent the image formed by the reflection of the secondary conical mirror which is the image radially sheared with the quantity 𝛿r. For this special configuration, the conicity of the secondary conical mirror was defined from simulations, in order to generate a radial displacement of about 10 mm. In conventional shearography, 10 mm is a typical lateral displacement value. Then it was the goal during the design of the optical arrangement. Besides, the optical distance between the system and the inner surface of the pipe (working distance) changes the amount of radial shearing. Bigger this working distance, bigger the radial displacement. In this work, the radial displacement ranged from 8 to 10 mm because the specimens used in the experiments have slightly different inner diameters. The tip of the conical mirror causes a great resolution reduction on the acquired image where no relevant information can be attained. In order to illustrate this difficult, the effective image area utilized by the camera sensor is illustrated in Fig. 4a and, in addition, Fig. 4b shows an actual image captured by the radial system where a sheet of graph paper has been positioned inside a tube. However, the image generated by the radial system results in concentric circles and radial lines with constant radial shear. Fig. 4b also shows three blind lines in the image reflected by the conical mirror. These dark lines are resulting from the three rods that compose the mechanical support of the primary conical mirror. The rods are positioned at 120° of each other and make the mirror fixation quite rigid. In the actual system the blind lines may disturb the measurement, since eventually they could hide some defects. However the next step of this work is build a more compact and portable system, and this system could be rotated inside the tube to measure in many angular positions. Thus, two overlapping measurements can be combined to avoid the blind regions.
2. Endoscopic shearography: a special shearography interferometer 360° vision systems are already widely studied and consist of a mirror with specific geometry where the camera is placed in front of it. This camera visualizes the 360° images of the environment in polar coordinates. When the image of an environment is visualized by a conical mirror vertical lines are seen as radial in the plane of the image, just as horizontal lines are seen as arcs. These characteristics are illustrated in Fig. 1. The proposed arrangement for the special shearography interferometer with radial sensitivity is based on the use of two conical mirrors: a 45° primary conical mirror to visualize the internal surface to be inspected, and a secondary 89° conical mirror responsible for the radial displacement on the sheared image. Both mirrors were custom made for this application. The proposed configuration is shown in Fig. 2. The laser light is scattered by the pipe inner wall and then directed to the primary conical mirror. The primary mirror reflects the light to a beam splitter which 2
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Fig. 2. Radial sensitivity interferometer setup.
3. Experimental results: discussion and analysis 3.1. Validation tests In order to evaluate the developed shearography system, two specimens with well-known characteristics have been tested. Both specimens made of a steel tube were internally coated with fiberglass composite material. 3.1.1. Specimen 1 The first specimen, named as CP1, measures 152 mm of external diameter and 148 mm of internal diameter. A composite coating of about 3 mm in thickness was applied to its inner surface. A 7 mm diameter hole has been drilled on the pipe wall and a micrometric screw was attached to allow the application of controlled mechanical loading from the outside directly into the composite material. The mechanical loading pushes the composite coating away from the steel inner surface to simulate an adhesion flaw. Fig. 6a shows the specimen CP1 and Fig. 6b
Fig. 3. Schematic drawing of an image generated by the radial shearography system. (For interpretation of the references to color in the text, the reader is referred to the web version of this article.)
Fig. 5a shows the 3D CAD models of the conical mirror and its three rods support. Fig. 5b shows the complete configuration design of the special shearography interferometer with radial sensitivity.
Fig. 4. Radial shearography system image: (a) Schematic of the effective image area utilized by the camera sensor; (b) Acquired image.
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Fig. 5. (a) Support of the primary conical mirror; (b) Optical configuration of the endoscopic shearography system.
Fig. 6. (a) Specimen 1 - CP1; (b) Threaded holes to attach the micrometric screw and through hole used to apply the mechanical loading.
details the two threaded blind holes for attaching the micrometric screw and the through hole for mechanical loading application. The mechanical loading produced by the micrometric screw resulted in very clear interference fringes, what allowed us to make some controlled inspections to analyze the system behavior. Two different sections of CP1 have been inspected: Section 1 at the upper specimen position and Section 2 at the lower specimen position. The micrometric screw applied a displacement of approximately 1 μm towards the center of the tube in both inspections. The Fig. 7 shows the difference phase maps of shearographic inspections for both sections. Besides the blind zones caused by the conical mirror support, the CP1 images still contains a fourth blind zone, highlighted on Fig. 7a. The external diameter of CP1 is smaller than the inner diameter of flange, so a new support has been built to adapt the CP1 to the test bench previously assembled to the flanged joints experiments. The new support imposed a barrier to the laser illumination, preventing the formation of speckles in this area and resulting in the blind zone on image. The Fig. 8 shows the stitching of the inspection results of Sections 1 and 2, after a mathematical transformation from polar to rectangular coordinates. The result is the complete defect map. The x-axis regards the angular position on tube, and y-axis regards the axial position on tube.
vious specimen, CP2 has a 3 mm thick inner layer of the same composite material. A 500 W halogen lamp was used to apply the thermal loading for CP2 inspection. The reference phase map with the specimen at room temperature was acquired, and then the second map was taken after heating the specimen for 10 s. In order to detect all inserted defects, four different positions in the axial direction of CP2 were measured. The measured sections were processed and overlapped to make easier the phase difference maps stitching. Fig. 10 shows the four original phase difference maps acquired during this experiment. Fig. 11 shows the overlap of the four measured sections after a transformation from polar to rectangular coordinates. The resulting map clearly shows six artificial defects inserted in CP2. Only the smallest defect, the through hole with 5 mm in diameter, was not detected. Its position is highlighted by an arrow and a white circle in the Fig. 11.
3.2. Flanged joints experiments In this section, two flanged unions made of composite material and 150 mm of nominal diameter were inspected: specimens 3 and 4. The specimen 3 (CP3) contains no defects and has been used as reference for the shearography images. In turn, specimen 4 (CP4) is the one that contains the artificially inserted defects. A thermal blower positioned about 50 mm from the upper face of the flange performed the loading for the radial shearography inspection. The hot gun was moved circularly to evenly heat the adhesion zone.
3.1.2. Specimen 2 The second specimen, identified as CP2, measures 170 mm of external diameter and 7 mm in the steel wall thickness. This specimen contains five through holes and two through slits positioned around the entire perimeter to simulate real defects, as shown in Fig. 9. As the pre4
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Fig. 7. Phase difference maps of CP1 due to a displacement of 1 μm: (a) Section 1: upper tube position; (b) Section 2: lower tube position.
Fig. 8. Stitching of the inspection results of Sections 1 and 2 in rectangular coordinates.
The tests results showed that the heating time required for interference fringes start occurring in each section varies according to the depth of the adhesive zone in relation to the upper face of the flange. The heating time required for Section 1 is considerably less than the heating time required for inspection of Section 3 which is the furthest away from the tube end. The heating time interval of 15 to 20 seconds was used for Section 1 while a range of 40 to 50 seconds to Section 2. Section 3 was heated with range from 60 to 70 seconds.
3.2.1. Specimen 3: flanged union without defects CP3 is a flanged composite joint with no internal flaws which has been used as reference for comparison with CP4 that has several defects artificially inserted. Three axially displaced sections were inspected in the inner surface of CP3 and the radial shearography results are shown in Fig. 12. Analyzing the generated results, we can note that a set of uniform and relatively concentric fringes appear in each inspected section. The irregularities in the spacing between fringes can be explained by the applied thermal loading since the upper section of the flange undergoes more heating than the lower section. We can also observe in Fig. 12a that some discontinuous fringes appeared. These fringes correspond to a small area located a few millimeters after the end of the adhesion zone and some fringes arise quite irregularly because the expansion of the tube in this area is not anymore limited by the flange.
Fig. 9. 3D CAD model of Specimen 2 (CP2) with artificial defects.
Three sections in the axial direction of the joints were inspected in order to thoroughly examine the adhesion zone. Following the same inspection procedure used to CP2, we performed the measurements by acquiring the first phase map at room temperature. A new phase map was acquired after heating the specimen in order to obtain the final phase difference map. 5
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Fig. 10. Phase difference maps of CP2: (a) Section 1, (b) Section 2, (c) Section 3 and (d) Section 4.
Fig. 11. Defect maps in rectangular coordinates. X-axis regards the angular position on tube and Y-axis regards the axial position on tube.
We transformed the images into rectangular coordinates and then did the overlapping of the three sections in order to observe the uniformity of the fringes. The result in rectangular coordinates is shown in Fig. 13. After the coordinates transformation, it is possible to observe more clearly the uniformity of the fringes in the adhesive area. Fig. 13 shows fringes practically horizontal and regularly distributed. Consequently, this fringes pattern can be used as reference pattern for a flanged joint without flaws. Different patterns will be compared next.
ing, distance between the union and the blower and others. Fig. 16 shows the results in polar coordinates. Again, for a better analysis, the images were transformed into rectangular coordinates and the sections overlapped and Fig. 17 shows the results. The phase difference maps generated in the inspections of CP4 clearly show the presence of discontinuities (or anomalies) in the fringe patterns, indicating the presence of three defects in this specimen. The presence of defects in this specimen is even more evident by comparing Fig. 17 with the phase difference maps of the specimen without defects (Fig. 13). With the objective of giving even more highlight to the defects found, the phase difference maps of CP4 and CP3 have been subtracted from each other and the resulting images are shown in Fig. 18. The shearography maps subtraction allowed the partial removal of the sets of parallel horizontal fringes present in both images. In the resultant maps, defects 1 and 3 can be seen with greater clearness at Sections 2 and 3, and defect 2 is best noticed at Section 1.
3.2.2. Specimen 4: flanged union with artificial defects In the manufacture process of specimen 4 (CP4), the composite tube and its flange were joined using specific adhesive and following to the assembly specifications of the manufacturer. To simulate the lack of adhesion between the surfaces of the tube and the flange, three 0,5 mm thick Teflon® patches with different dimensions were inserted, as shown in Fig. 14. The variation of the patches dimensions helped to analyze the capacity of flaws detection of the radial shearography system. These artificial defects are located at 90° from each other, thus, there are also some adhesive zones with no defects. Fig. 15 shows CP4 after the flange union. In the inspection of this specimen, the same parameters of the previous inspection were used: heating times, analyzed sections, laser light-
4. Conclusions This work presented a proposal and the validation of a special shearography system with radial sensitivity and explored its applica6
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Fig. 12. Phase difference maps of specimen 3 (CP3): (a) Section 1, (b) Section 2 and (c) Section 3.
Fig. 13. Phase difference maps of specimen 3 in rectangular coordinates and overlapping of sections. Fig. 15. Specimen 4 after insertion of defects.
The optical system with conical irrors is capable to visualize all 360° of the inner section of the tube with just one image. However, it has just the radial sensitivity direction and the quantity of the radial displacement is not (or almost not) adjustable. The radial displacement of the proposed arrangement is given by the conicity of the secondary conical mirror. Besides, the optical distance between the system and the inner surface of the pipe (working distance) changes the amount of radial shearing. Bigger this working distance, bigger the radial displacement. The main advantage of this radial configuration, when compared to others in the literature, is that the radial displacement is constant through the image, so the sensitivity is unique for all regions of image. For this application the optical setup was designed to achieve a radial displacement of about 10 mm which is a typical lateral displacement value used to shearography inspections. In this work, the radial displacement ranged from 8 to 10 mm because the specimens used in the experiments have slightly different inner diameters. The fixed value for the radial displacement can be considered a limitation of this configuration, however there are other advantages that overcome it.
Fig. 14. Artificial defects inserted in CP4: 30 × 60 mm2 ; 15 × 15 mm2 ; 85 × 30 mm2 .
bility for detecting adhesion flaws on internal surfaces of flanged joints of composite material pipes. The new shearography system uses two conical mirrors to achieve radial sensitivity.
Fig. 16. Phase difference maps of CP4: (a) Section 1, (b) Section 2 and (c) Section 3.
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Fig. 17. Phase difference maps of CP4 in rectangular coordinates and sections overlapping.
be developed with the purpose of compacting and toughing the radial shearography system in order to be applied in pipe shops and other sectors of the oil and gas industry. Acknowledgments Authors would like to express thanks to Petrobras and CNPq - National Council for Scientific and Technological Development for the financial support for the development of this research. References [1] Callister WDJ, Rethwisch DG. Materials science and engineering: an introduction. 8th ed. USA: John Wiley and Sons; 2009. ISBN 978-0470419977. [2] Ameron. Corrosion-resistant fiberglass piping systems; 1998. Texas. [3] Associação Brasileira de Normas Técnicas. NBR ISO 15921: Indústrias de Petróleo e Gás Natural — tubulação de compósito - Parte 1: vocabulário, símbolos, aplicações e materiais, Rio de Janeiro, 2011. [4] Gibson AG. The cost effective use of fibre reinforced composites offshore. United Kingdom: HSE Books; 2003. [5] Adams RD, Cawley P. A review of defect types and nondestructive testing techniques for composites and bonded joints. NDT Int 1988;21(August):208–22. [6] Associação Brasileira de Normas Técnicas. NBR 15921-4: Indústrias de Petróleo e Gás Natural - tubulação de Compósito - Parte 4: fabricação, montagem e operação, Rio de Janeiro, 2011. [7] Hung YY. Shearography for non-destructive evaluation of composite structures. Opt Laser Eng 1996;24:161–82. [8] Hung YY. Applications of digital shearography for testing of composite structures. Composites B 1999;30:765–73. [9] Anisimov, A.G., Serikova, M.G., Groves, R.M. Development of the 3D shape shearography technique for strain inspection of curved objects. Imag Appl Opt, 2016. [10] Xie X, Yang L, Xu N, Chen X. Michelson interferometer based spatial phase shift shearography. Appl Opt 2013;52(17):4063–71 v. [11] Hung YY. Shearography: a novel and practical approach for nondestructive testing. J Nondestruct Test 1989;8(2):55–67. [12] Hung, Y.Y. Apparatus and method for electronic analysis of test object, US Patent 4,887,899. 1989. [13] Leendertz JA, Butters JN. An image-shearing speckle-pattern interferometer for measuring bending moments. J Phys E 1973;6:1107–10. [14] Hung YY. Shearography: a new optical method for strain measurement and non-destructive testing. Opt Eng 1982;21:391–5. [15] Hung YY. Digital shearography versus TV-holography for non-destructive evaluation. Opt Laser Eng 1997;26:421–36. [16] Pagliarulo V, Rocco A, Langella A, Riccio A, Ferraro P, Antonucci V, et al. Impact damage investigation on composite laminates: comparison among different NDT methods and numerical simulation. Measure Sci Technol 2015;26:085603. [17] Huber R, Berger R. Shearography in quality assurance and infield service. In: ECNDT - 9th European NDT Conference - Proceedings Mo .2.1.1, September 25-29, Berlin Germany; 2006. [18] Russell SS, Lansing MD. Endoscopic Shearography and Thermography Methods for Non Destructive Evaluation of Lined Pressure Vessels 1997. [19] Ganesan AR, Sharma DK, Kothiyal MP. Universal digital speckle shearing interferometer. Appl Opt 1988;27(Novembro):4731–4 v. [20] Murty MVRK, Shukla RP. Radial shearing interferometers using a laser source. Appl Opt 1973;12(Novembro):2765–7.
Fig. 18. Phase difference maps resulting from maps subtraction (CP3 – CP4).
The ability of the system to detect defects was assessed from tests performed with a steel tube internally coated with composite material and containing a micrometric screw coupled to its outer surface (CP1), allowing the application of a known and static mechanical loading. The results obtained with this specimen showed a good performance of the system in the detection of small deformations imposed to the surface and validated the radial configuration of the shearography system. The specimen CP2 was a steel tube containing five through holes and two through slits distributed along the specimen perimeter to simulate defects. CP2 was also internally coated with composite material. This specimen has been used to evaluate the thermal loading with the endoscopic shearography system. The proposed endoscopic system also inspected two flanged specimens, one without defects (CP3) and another with artificial defects (CP4), both exposed to thermal loading. The radial shearography system was able to detect the three artificially inserted defects of the specimen 4. The results obtained with CP3 were used as reference fringe pattern and helped the identification of the defects of the CP4 and the elimination of fringes not associated to the internal flaws. Since the experiments started in laboratory resulted in very good outcomes, validating the great potential of the system, future works will
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Fabiano Macedo is graduated in mechanical engineering at Federal University of Rio Grande (2014) and master in mechanical engineering with emphasis in metrology and instrumentation (2017) in Federal University of Santa Catarina. Currently works in the Laboratory of Metrology of the School of Engineering at Federal University of Rio Grande. Has experience in the areas of manufacturing and metrology.
Mauro Eduardo Benedet is graduated in control and automation engineering at the Federal University of Santa Catarina (2005), did master in mechanical engineering with emphasis in scientific and industrial metrology (2008) and PhD in mechanical engineering at the same university (2013). Actually works at the LABMETRO (Laboratory of Metrology and Automatization) of the Mechanical Engineering Department of the Federal University of Santa Catarina with research projects in the oil, gas and energy industry. Has experience in the areas of Automation, Instrumentation and Metrology.
Analucia Vieira Fantin finished her studies in applied mathematics by Federal University of Rio Grande do Sul in 1996. She received the MSc in mechanical engineering from the University of Santa Catarina in 1999, and the PhD degree in optical metrology at the same university in 2003. She is researcher in Federal University of Santa Catarina since 2003, acting on subjects like optical metrology and scientific programming. Her research areas include holography, shearography, defectometry, and shape measurement for non-destructive testing.
Daniel Pedro Willemann received the BSc in mechanical engineering from the Federal University of Santa Catarina – UFSC – Florianópolis – Brazil (1999), the master’s degree in scientific and industrial metrology at the same University (2002) and the PhD degree in mechanical engineering from the Università Politecnica delle Marche – Ancona – Italy (2006). From 2006 is a researcher at the Laboratory of Metrology at UFSC. In 2012, he also became a professor at State University of Santa Catarina – UDESC – SC – Brazil. His research is concerned with activities of for the development of shearography as a non-destructive test technique for composite materials inspections.
Fabio A. A. Silva received his BSc in mechanical engineering from the Federal University of Santa Catarina – UFSC – Florianópolis – Brazil (2010) and his MSc at the same University (2016). Actually is a researcher at the LABMETRO (Laboratory of Metrology and Automatization) at UFSC. His research interests include optical metrology, speckle metrology and optical system designs for non-destructive inspection.
Armando Albertazzi received the BSc in mechanical engineering from the Federal University of Bahia – Brazil in 1982, received the master’s degree in scientific and industrial metrology at the Federal University of Santa Catarina in 1984 and the PhD degree in mechanical engineering from the same University in 1989. Since 1987, he is professor at the Federal University of Santa Catarina. His research refers to new optical techniques for non-destructive inspection, combining the principles of optical metrology and image processing.
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