- Email: [email protected]
Swedish NDT Society—annual meeting
CONFERENCE REPORTS Non-destructive
testing of concrete in Romania
London, 6 June 1968 Dr I. Facaoaru of Romania gave a talk to about sixty members of the Materials Technology Division of the Concrete Society on 6th June 1966 at University College, London. Dr Facaoaru, who is head of the Non-destructive Testing Section at the Building Research Institute, Bucharest, was welcomed by the chairman, Dr A. R. Collins. He first underlined the need which had been found in his country for non-destructive methods of testing concrete. In Romania about 60% of all building construction is in concrete, and some means is required for checking the quality of the in situ material, because use of test-specimens often overestimates true strength. Non-destructive methods offer the possibility of testing structural concrete to estimate its in situ strength and to locate voids and cracks; they were taken up in Romania about twelve years ago, and a great deal of time and effort has been spent in further development. Successful applications to building constructions have multiplied year by year, and the experience gained in practical testing has been backed by continued research at the Building Research Institute. The ultrasonic pulse method has been the main test used by Dr Facaoaru and his colleagues in the past. He discussed at length experimental technique, applications for defectoscopy and homogeneity surveys of structural concrete, estimation of in situ elastic properties, and estimation of in situ strength. Although some research has been started on the influence of changes in concrete composition on ultrasonic attenuation the main practical applications are based on the measurement of pulse transit times through measured distances in concrete. The ‘pulse velocity’ derived from these measurements has a limited empirical correlation with concrete strength, and Dr Facaoaru has taken great pains to derive correction coefficients for every factor which influences this correlation. Correction coefficients have been evaluated for changes in type of cement, aggregatecement ratio, aggregate grading, aggregate size, cement additives, and curing conditions, for the types of concrete commonly used in Romania, and they are tabulated in the Romanian Standard which covers the ultrasonic pulse testing of concrete.
Swedish NDT Society-annual huidaberg,
Dr Facaoaru dealt briefly with other non-destructive tests being used in Romania: resonance, radiography, radioscopy, magnetic and hardness methods. Radiography is used only rarely for testing structural concrete because the cost of x-ray film is high in Romania and more effort is being devoted to developing radioscopic techniques; these are now in use for locating the position of reinforcing bars, measuring variations in density, etc. Magnetic methods, such as those on which the covermeter operates, are used to provide the approximate location of steel reinforcing bars, and they are usually used in conjunction with the radioactive methods which give greater precision. Hardness and indentation methods have been mainly used in the past to provide a rough estimation of the in situ strength of concrete: a rebound hammer device has been studied in detail and correction coefficients have been evaluated for the various factors which influence the correlation between rebound number and concrete strength. Dr FaCaOaN ended his talk by discussing the recent use of combined methods of non-destructive testing to improve the estimate of in situ strength. Correlations between ultrasonic pulse velocity, rebound number and strength have been studied for a number of concretes and Dr Facaoaru was very enthusiastic about the future prospects of this work. Dr Facaoaru’s talk was mainly concerned with the research angle, and it was unfortunate that there was no time left for questions which may have brought out more information on the practical aspects of the work.
meeting
Sweden, 5-7 June 1968.
This is a report on the papers given at the snnual meeting of the Swedish Society for Non-Destructive Testing, held in Atvidaberg on %7 June 1966. S. Ingevald, of the Pressure Vessel Society (Angpsnnefareningen), in his talk on ‘How and why to use ndt’, gave an introduction to ndt for those members of the Society who are not actively concerned with testing techniques. He covered both the technical and the economic aspects, and used practical examples to illustrate his points. The work of Commission V of the IlW on the ndt of weldments was reviewed in the paper ‘International cooperation on the non-destructive testing of weldments’ by A. Ljunghem, of the Technical X-ray Centre (Tekniska Rllntgencentralen). The author pointed out that this work constitutes qualified technical cooperation on the international level, and that the documents accepted and published by the IIW are recommendations or information of some considerable status. 46
Dr Facaoaru said the ultrasonic pulse method was probably easier to apply in Romania than in Great Britain because building construction was carried out by a few large government building enterprises using concrete of fixed composition for which the properties of the constituent materials were checked at regular intervals. Furthermore, there is only one type of aggregate in use in those parts of Romania where most of the buildings are being constructed, so that one of the most important factors which changes the correlation between pulse velocity and strength is absent.
non-destructive
testing February 1969
Some of those documents continue to form the basis of IS0 standards. ‘Technical and economic aspects of ndt in modern ship building’ was the subject of the paper by J. Eri, of Det Norske Veritas, Oslo. Ships have been classified for a long time, and that classification is based on quality control. The development of new types of ship, larger vessels, and the introduction of new types of material and component have led to increased use of ndt methods in ship building. Mr Eri underlined the importance of avoiding defects, and the economic consequences of the loss of shipping. He described present procedures for non-destructive testing of ships’ hull, machinery, heat exchangers, containers, and tanks, and also described several examples of sea damage caused by defects that could have been avoided if ndt had been used when the ships were built. G. Gustaffson, of the Swedish Casting Society (Svenska Gjuterif6reningen), Stockholm, spoke on ‘Resonance testing of cast iron’. The resonance frequency of a cast-iron com-
ponent is determined mainly by the geometry of the object and the moduli of elasticity and density of the material. Properties which depend on the modulus of elasticity are also dependent on the resonance frequency, e.g. tensile strength, hardness and damping. The method is suitable for routine checking and sorting of objects cast in grey and nodular iron. Given proper calibration, tensile strength and graphite structure can be assessed for quite complicated shapes. However, the method is not so suitable for detecting internal defects such as cracks, shrinkage, pores and blisters. It has only been introduced recently for routine use in foundries. The most important application is to cast goods for the automotive industry. B. Hedlund, of Essem Metotest, Skultuna, reviewed the possibilities and limitations of ultrasonic testing for cast and welded products. He described the theoretical basis, and then gave some practical examples on the choice of probe type, evaluation of the indications obtained, the results that can be expected for different types of defect, and automatic and semi-automatic testing systems. A review of ndt methods for heavy castings was given by Y. BostrSm, of Al3 Motala Verkstad, Motala, in his paper ‘The non-destructive testing of steel castings in manufacture and maintenance’. Mr Bostram gave examples, e.g. crank shafts for marine engines, described the ndt of machine parts, and discussed ndt standards. Several different methods have been used for ndt of welded tubing, and these were described in the paper by A. Arnelo, of Essem Metotest, Slcultuna. Magnetic leakage has been used to check defects during the welding process. It is necessary to compensate for changes in welding speed and also for variations in the position of the weld. Eddy-current testing is used both for separate station and on-line testing. The tubes are magnetized to saturation to avoid interference from changes in magnetic permeability. Mr Arnelo gave details of some actual installations. Eddy-current testing is normally used for tubes up to 4in (100mm) outside diameter and with wall thicknesses up to about 3/1sin (4.8mm). Ultrasonic testing is also used,
especially for tubes with greater wall thicknesses; the semi-immersion and gap techniques are employed. The author emphasized the importance of calibration standards, normally tubes containing standard defects, in furthering the acceptance of non-destructive testing methods. A number of different standards are in use, and some of them are of little real value. It is essential that standards should be coordinated and improved. H. Bark, of AB J%rnfargdling, H%lleforsnPs, spoke on ‘Experience of non-destructive testing of nodular iron’. NDT is mainly used in the author’s company to check products of nodular and malleable iron, and is applied either directly after casting or after heat treatment. Surface defects, such as cracks, are detected by magnetic particle or penetrant methods. Ultrasonics and gamma radiography are used to detect internal defects, such as pores, blisters and inclusions. Certain properties, such as hardness and tensile strength, are checked either on the parts themselves or on testpieces cast during the casting programme. Spectroscopy is used for chemical analysis, and the metallurgical structure before and after heat treatment is checked by normal etching and microscopical examination of samples. Structure is also checked with electromagnetic equipment in which goods can be sorted into different hardness classes. ‘Critical evaluation of methods of ndt on welded structures’ was the subject of the paper by G. Klose of the Technical X-ray Centre. The type and amount of non-destructive testing applied to welded structures must be adapted to the risks to human life, the cost of material damage and stoppages in service that may be caused by a failure. When one is evaluating an ndt method one must distinguish between the reliability and limitation of the method and the lmowledge and reliability of the inspector who uses the test method. Mr Klose underlined the risks and weaknesses inherent in x-ray, ultrasonic, magnetic particle, dye penetrant and leak testing. He also pointed out that the different methods have different advantages and limitations, and specification writers know of these. A.von Heijne
Ultrasonics for Industry 1968 SI Ermin’s
Hotel, London, 15-l 6 October 1968
This was the fourth conference and exhibition sponsored by Non-Destructive Testing’s sister journal Ultrasonics. The variety of subject matter of the papers read served to demonstrate the wide range of the applications of ultrasonics technology.
3
P. N. T. Wells (Bristol General Hospital) Engineering aspects of a scanner for examination of the human breast
4
F. D. Fielder and F. R. Baker (Sonicaid An ultrasonic foetal heart monitor
5
J. D. Lavender (Steel Castings Research and Trade Association, Sheffield) The certification of ultrasonics operators: l-for castings
6
C. J. Abrahams (Consultant) The certification of ultrasonics operators: 2-for welds
7
J. D. Redman (AWRE Aldewnaston) J. E. E. Fleming and A. J. Hall (Queen Mother’s Hospital, Glasgord Holographic visual displays
8
G. M. L. Gladwell (University impedance meter
9
J. Coulthard (Constantine College of Technology, Middlesbroughl The performance of ultrasonic air sensors
10
R. L. Loosemore meter
1 D. Young (Rocket Propulsion Establishment,Aylesbury) Collection and analysis of data from automatic inspection
11
2 K. R. Whittington and B. D. Cox (Tube Investments Research Laboraton’es, Saffron Walden) Steering and focussing of ultrasonic beams in tube inspection
D. M. J. P. Manley (Crispine E&.neering Gas bubble detection in blood
12
G. R. Halford (Vacuum Reflex Ltd, New ,tlalden) Two acoustic equipments for the diver
There were five papers of direct interest. The papers by J. D. Lavender and C. J. Abrahams on ‘The certification of ultrasonics operators’ are published in this issue as a joint paper (p 34). The papers by D. Young, K. R. Whittington and B. D. Cox, and J. D. Redman et al were all published in the January issue of Ultrasonics, and a shortened version of the last of these was published in the November 1968 issue of Non-Destructive Testing (p 360) Although there was no new ndt equipment on show in the exhibition, there was plenty of interest shown, and the general feeling among the exhibitors was one of satisfaction with the event. Next year’s Ultrasonics for Industry conference and exhibiy;;gwill be held at St Ermin’s Hotel on October 7th and 8th L. J. I. Browne Conference papers
of Southampton/
(AERE Harwettl
non-destructive
Ltd, Bognor Regis)
The contact
A new ultrasonic flow-
Ltd. Camberley)
testing February 1969
49
testing of concrete in Romania
London, 6 June 1968 Dr I. Facaoaru of Romania gave a talk to about sixty members of the Materials Technology Division of the Concrete Society on 6th June 1966 at University College, London. Dr Facaoaru, who is head of the Non-destructive Testing Section at the Building Research Institute, Bucharest, was welcomed by the chairman, Dr A. R. Collins. He first underlined the need which had been found in his country for non-destructive methods of testing concrete. In Romania about 60% of all building construction is in concrete, and some means is required for checking the quality of the in situ material, because use of test-specimens often overestimates true strength. Non-destructive methods offer the possibility of testing structural concrete to estimate its in situ strength and to locate voids and cracks; they were taken up in Romania about twelve years ago, and a great deal of time and effort has been spent in further development. Successful applications to building constructions have multiplied year by year, and the experience gained in practical testing has been backed by continued research at the Building Research Institute. The ultrasonic pulse method has been the main test used by Dr Facaoaru and his colleagues in the past. He discussed at length experimental technique, applications for defectoscopy and homogeneity surveys of structural concrete, estimation of in situ elastic properties, and estimation of in situ strength. Although some research has been started on the influence of changes in concrete composition on ultrasonic attenuation the main practical applications are based on the measurement of pulse transit times through measured distances in concrete. The ‘pulse velocity’ derived from these measurements has a limited empirical correlation with concrete strength, and Dr Facaoaru has taken great pains to derive correction coefficients for every factor which influences this correlation. Correction coefficients have been evaluated for changes in type of cement, aggregatecement ratio, aggregate grading, aggregate size, cement additives, and curing conditions, for the types of concrete commonly used in Romania, and they are tabulated in the Romanian Standard which covers the ultrasonic pulse testing of concrete.
Swedish NDT Society-annual huidaberg,
Dr Facaoaru dealt briefly with other non-destructive tests being used in Romania: resonance, radiography, radioscopy, magnetic and hardness methods. Radiography is used only rarely for testing structural concrete because the cost of x-ray film is high in Romania and more effort is being devoted to developing radioscopic techniques; these are now in use for locating the position of reinforcing bars, measuring variations in density, etc. Magnetic methods, such as those on which the covermeter operates, are used to provide the approximate location of steel reinforcing bars, and they are usually used in conjunction with the radioactive methods which give greater precision. Hardness and indentation methods have been mainly used in the past to provide a rough estimation of the in situ strength of concrete: a rebound hammer device has been studied in detail and correction coefficients have been evaluated for the various factors which influence the correlation between rebound number and concrete strength. Dr FaCaOaN ended his talk by discussing the recent use of combined methods of non-destructive testing to improve the estimate of in situ strength. Correlations between ultrasonic pulse velocity, rebound number and strength have been studied for a number of concretes and Dr Facaoaru was very enthusiastic about the future prospects of this work. Dr Facaoaru’s talk was mainly concerned with the research angle, and it was unfortunate that there was no time left for questions which may have brought out more information on the practical aspects of the work.
meeting
Sweden, 5-7 June 1968.
This is a report on the papers given at the snnual meeting of the Swedish Society for Non-Destructive Testing, held in Atvidaberg on %7 June 1966. S. Ingevald, of the Pressure Vessel Society (Angpsnnefareningen), in his talk on ‘How and why to use ndt’, gave an introduction to ndt for those members of the Society who are not actively concerned with testing techniques. He covered both the technical and the economic aspects, and used practical examples to illustrate his points. The work of Commission V of the IlW on the ndt of weldments was reviewed in the paper ‘International cooperation on the non-destructive testing of weldments’ by A. Ljunghem, of the Technical X-ray Centre (Tekniska Rllntgencentralen). The author pointed out that this work constitutes qualified technical cooperation on the international level, and that the documents accepted and published by the IIW are recommendations or information of some considerable status. 46
Dr Facaoaru said the ultrasonic pulse method was probably easier to apply in Romania than in Great Britain because building construction was carried out by a few large government building enterprises using concrete of fixed composition for which the properties of the constituent materials were checked at regular intervals. Furthermore, there is only one type of aggregate in use in those parts of Romania where most of the buildings are being constructed, so that one of the most important factors which changes the correlation between pulse velocity and strength is absent.
non-destructive
testing February 1969
Some of those documents continue to form the basis of IS0 standards. ‘Technical and economic aspects of ndt in modern ship building’ was the subject of the paper by J. Eri, of Det Norske Veritas, Oslo. Ships have been classified for a long time, and that classification is based on quality control. The development of new types of ship, larger vessels, and the introduction of new types of material and component have led to increased use of ndt methods in ship building. Mr Eri underlined the importance of avoiding defects, and the economic consequences of the loss of shipping. He described present procedures for non-destructive testing of ships’ hull, machinery, heat exchangers, containers, and tanks, and also described several examples of sea damage caused by defects that could have been avoided if ndt had been used when the ships were built. G. Gustaffson, of the Swedish Casting Society (Svenska Gjuterif6reningen), Stockholm, spoke on ‘Resonance testing of cast iron’. The resonance frequency of a cast-iron com-
ponent is determined mainly by the geometry of the object and the moduli of elasticity and density of the material. Properties which depend on the modulus of elasticity are also dependent on the resonance frequency, e.g. tensile strength, hardness and damping. The method is suitable for routine checking and sorting of objects cast in grey and nodular iron. Given proper calibration, tensile strength and graphite structure can be assessed for quite complicated shapes. However, the method is not so suitable for detecting internal defects such as cracks, shrinkage, pores and blisters. It has only been introduced recently for routine use in foundries. The most important application is to cast goods for the automotive industry. B. Hedlund, of Essem Metotest, Skultuna, reviewed the possibilities and limitations of ultrasonic testing for cast and welded products. He described the theoretical basis, and then gave some practical examples on the choice of probe type, evaluation of the indications obtained, the results that can be expected for different types of defect, and automatic and semi-automatic testing systems. A review of ndt methods for heavy castings was given by Y. BostrSm, of Al3 Motala Verkstad, Motala, in his paper ‘The non-destructive testing of steel castings in manufacture and maintenance’. Mr Bostram gave examples, e.g. crank shafts for marine engines, described the ndt of machine parts, and discussed ndt standards. Several different methods have been used for ndt of welded tubing, and these were described in the paper by A. Arnelo, of Essem Metotest, Slcultuna. Magnetic leakage has been used to check defects during the welding process. It is necessary to compensate for changes in welding speed and also for variations in the position of the weld. Eddy-current testing is used both for separate station and on-line testing. The tubes are magnetized to saturation to avoid interference from changes in magnetic permeability. Mr Arnelo gave details of some actual installations. Eddy-current testing is normally used for tubes up to 4in (100mm) outside diameter and with wall thicknesses up to about 3/1sin (4.8mm). Ultrasonic testing is also used,
especially for tubes with greater wall thicknesses; the semi-immersion and gap techniques are employed. The author emphasized the importance of calibration standards, normally tubes containing standard defects, in furthering the acceptance of non-destructive testing methods. A number of different standards are in use, and some of them are of little real value. It is essential that standards should be coordinated and improved. H. Bark, of AB J%rnfargdling, H%lleforsnPs, spoke on ‘Experience of non-destructive testing of nodular iron’. NDT is mainly used in the author’s company to check products of nodular and malleable iron, and is applied either directly after casting or after heat treatment. Surface defects, such as cracks, are detected by magnetic particle or penetrant methods. Ultrasonics and gamma radiography are used to detect internal defects, such as pores, blisters and inclusions. Certain properties, such as hardness and tensile strength, are checked either on the parts themselves or on testpieces cast during the casting programme. Spectroscopy is used for chemical analysis, and the metallurgical structure before and after heat treatment is checked by normal etching and microscopical examination of samples. Structure is also checked with electromagnetic equipment in which goods can be sorted into different hardness classes. ‘Critical evaluation of methods of ndt on welded structures’ was the subject of the paper by G. Klose of the Technical X-ray Centre. The type and amount of non-destructive testing applied to welded structures must be adapted to the risks to human life, the cost of material damage and stoppages in service that may be caused by a failure. When one is evaluating an ndt method one must distinguish between the reliability and limitation of the method and the lmowledge and reliability of the inspector who uses the test method. Mr Klose underlined the risks and weaknesses inherent in x-ray, ultrasonic, magnetic particle, dye penetrant and leak testing. He also pointed out that the different methods have different advantages and limitations, and specification writers know of these. A.von Heijne
Ultrasonics for Industry 1968 SI Ermin’s
Hotel, London, 15-l 6 October 1968
This was the fourth conference and exhibition sponsored by Non-Destructive Testing’s sister journal Ultrasonics. The variety of subject matter of the papers read served to demonstrate the wide range of the applications of ultrasonics technology.
3
P. N. T. Wells (Bristol General Hospital) Engineering aspects of a scanner for examination of the human breast
4
F. D. Fielder and F. R. Baker (Sonicaid An ultrasonic foetal heart monitor
5
J. D. Lavender (Steel Castings Research and Trade Association, Sheffield) The certification of ultrasonics operators: l-for castings
6
C. J. Abrahams (Consultant) The certification of ultrasonics operators: 2-for welds
7
J. D. Redman (AWRE Aldewnaston) J. E. E. Fleming and A. J. Hall (Queen Mother’s Hospital, Glasgord Holographic visual displays
8
G. M. L. Gladwell (University impedance meter
9
J. Coulthard (Constantine College of Technology, Middlesbroughl The performance of ultrasonic air sensors
10
R. L. Loosemore meter
1 D. Young (Rocket Propulsion Establishment,Aylesbury) Collection and analysis of data from automatic inspection
11
2 K. R. Whittington and B. D. Cox (Tube Investments Research Laboraton’es, Saffron Walden) Steering and focussing of ultrasonic beams in tube inspection
D. M. J. P. Manley (Crispine E&.neering Gas bubble detection in blood
12
G. R. Halford (Vacuum Reflex Ltd, New ,tlalden) Two acoustic equipments for the diver
There were five papers of direct interest. The papers by J. D. Lavender and C. J. Abrahams on ‘The certification of ultrasonics operators’ are published in this issue as a joint paper (p 34). The papers by D. Young, K. R. Whittington and B. D. Cox, and J. D. Redman et al were all published in the January issue of Ultrasonics, and a shortened version of the last of these was published in the November 1968 issue of Non-Destructive Testing (p 360) Although there was no new ndt equipment on show in the exhibition, there was plenty of interest shown, and the general feeling among the exhibitors was one of satisfaction with the event. Next year’s Ultrasonics for Industry conference and exhibiy;;gwill be held at St Ermin’s Hotel on October 7th and 8th L. J. I. Browne Conference papers
of Southampton/
(AERE Harwettl
non-destructive
Ltd, Bognor Regis)
The contact
A new ultrasonic flow-
Ltd. Camberley)
testing February 1969
49