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DEVELOPMENT OF FRASTA SIMULATION SOFTWARE
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DIRECT.
ACTA METALLURGICA SINICA (ENGLISH LETTERS)
Acts Metall. Sin. (Engl. Lett.)Vol. 19 No.3 pp 165-170 Jun. 2006
www.ams.org.cn
DEVELOPMENT OF FRASTA SIMULATION SOJTWARE Y.G. Cao* and K. Tanaka Department of Mechanical Systems Engineering, Toyama Prefectural University, Toyama 939-0398, Japan Manuscript received 21 November 2005
I
Fracture-surface topography analysis (FRASTA) was successjklly used to simulate the process of crack and calculate parameters of crack such as the crack opening angle (COA) and crack-tip opening angle (CTOA). But because the amount of calculation is large, errors are ofen made during the course of calculation. FRASTA simulation sojiware, namely frncture surface analyst (FSA) is developed and a series of center-cracked tension (CCT) and double edge notched (DEN) specimens of different materials with different sizes are tested, theirfracture surfaces are scanned by mn-contact 3 0 scanning qstem and the elevation data of the fracture surfaces is recor&d. FSA used the recorded elevation data offrcture surfaces to simulate the process of crack based on the prinsiple of FRASTA. Results show that FSA can accurately simulate the process and calculate the parameters of crack. m y WORDS FRASTA Vracture-surface topography analysis); COA (crack opening angle): CTOA (crack-tip opening angle); CCT (center-cracked tension); DEN (double edge notched)
1. Introduction A new method, using the principle of FRASTA (fracture-surface topography analysis)['], which matches the conjugate fracture surfaces of the broken component together, to the initial position (the position before crack extended) and considers the coincidence as the plastic deformation during the course of fracture, for determining the parameters of COA (crack opening angle) and CTOA (crack-tip opening angle) is provided in Ref.[2]. The fracture surfaces were scanned by a non-contact 3D measuring system and the elevation data was recorded. The cross-sectional plots were extracted to be analyzed. By comparing the crack extension, plastic rotation factor, and COA obtained by the method of double clip gauge and by this new method respectively, the validity of it was verified. It was then used to determine the CTOA, which is unavailable by the elastic compliance method. The critical CTOA was well determined in Ref.[2]. By the new method, it is very convenient to extract a pair of cross-sectional plots at any loca*Corresponding author. Tel.: +81 76 6567500; fax: +81 76 6566131 E-nail address : caoyuguangogrnail .corn ( Y . G. Cao)
. 166
tion through specimen thickness. The variation of crack opening deformation (COA and CTOA) through specimen thickness could be obtained easily, as it is very difficult to obtain it by the usual methods. It was found that COA was more stable than CTOA through specimen thickness and was more appropriate to be used as the parameter to direct the extension of crack when using this method. It was verified in Ref.[2] that the result of the new method could match the result of the elastic compliance method well. All in all, the method provides a new way to extract usehl information that is left on the fracture surface and could be applied easily. But, according to the experience, it is formidable work to process the fracture surface elevation data and deduce the results. At the same time, errors are often made during the course of calculation by hand. Both of them decreased the credibility and accuracy of the application of this method. Thus, it is necessary to develop FRASA simulation software that can do the work well to save time and improve precision.
2. Experimental The specimen type discussed in Ref.[2] is CT (cracked tension). The CT specimen is one of the most widely used in the field of crack research. Because the CCT (center-cracked tension) and DEN (double edge notched) specimens are also widely used, especially when creating a model to solve the practical problem, in this research, the software is developed to analyze the process of crack of these three types of specimens-CT, CCT and DEN. But because the experimental procedure and results for the CT specimen were discussed in Ref.[2], this paper will focus on the CCT and DEN specimens. In this paper, two kinds of alloy steel are used for testing. The chemical compositions of them are shown in Table 1. They are manufactured into CCT and DEN specimens as shown in Fig. 1. The sizes of specimens tested in this paper are shown in Table 2.
Material
C
1
0.1 0.045
2
Table 1 Chemical compositions (wt%) of materials Al P S Mn Si 0.03 0.02 0.004 0.01 1.3 0.03 0.02 0.01 0.01 0.2
C
0 (a)
Fig. 1 Specimens:(a) CCT specimen and (b) DEN specimen.
N 0.04
Ti 0.06
0.03
0
.
167 .
Table 2 Specimens being tested Number A
B C D
Material 1
Tvoe CCT
1
DEN
2
CCT
2
DEN
W. mm 60 60 70 I0
H , mm 300 300 300 300
B, mm 4.5 4.5 4.5 4.5
2aJW 0.5
0.6 0.62 0.56
Fig.2 Setups of measuring displacement for two specimen: (a) CCT specimen and (b) DEN specimen.
The setup for measuring the displacement for CCT and DEN specimens are shown in Figs. 2a and b. For the CCT specimen, as shown in Fig.2a, a clip gauge is used to measure the load-line displacement and for the DEN specimen, as shown in Fig.2b, a clip gauge and a ring gauge are used to measure the displacement at both crack mouths of the specimen.
3. Development of Program The new method introduced in Ref.[2] can accurately calculate the parameter of crack such as COA and CTOA. In order to make the calculation more accurate and make it possible for those who do not have much experience in this field to do this work, FSA (fracture surface analyst) was developed in this paper. The software is developed under the operating system of Microsoft Windows XP Professional with the platform of Microsoft Visual Basic 6.0. The procedure of functions that the software fulfilled is shown in Fig.3, where, the matching of conjugate fracture
Input elevabon data of upper a d Iwerfractue surfaces
I
I
Simulate the p m a of fracture and calculate the values of parameterS
Fig.3 Procedure of FSA.
I
168 . surfaces precisely and the selection of field for analysis are the most important and difficult. The effects of these two steps very much influence the results of the analysis. The process of fracture of the DEN specimen can be expressed by Fig.4. Because the process of fracture for the CCT specimen is very similar to that of the DEN specimen, it will not be discussed in this paper. After the fracture, the fracture surfaces are scanned by non-contact 3D measuring system and the elevation data is recorded so it can be analyzed by FSA. According to FRASTA, using the elevation data of the fracture surfaces to simulate the process of fracture, it can be expressed as shown in Fig.5, for the DEN specimen. In this paper, we developed FSA according to the procedure shown in Fig.3, step by step, to fulfill the functions necessary for fracture process simulation and parameter calculations.
E
b
recrack
Specimen upper half Upper fracture surface Pre-crack
,
Lower fracture surface Specimen l m r haii
Fig.4 Process of fracture for the DEN specimen.
Fig.5 Process of matching the conjugate fracture surfaces of the DEN specimen: (a) the upper fracture surface, which is inverted along specimen thickness direction; (b) the upper fracture surface is mirrored to correlate the lower fracture surface; (c) the position of the upper and lower surfaces are adjusted to make the pre-crack match each other precisely; (d) the upper and lower surfaces are moved according to the displacement recorded at both crack mouths and (e) final state when simulation finished.
. 169 .
4. Results Using FSA, after inputting the recorded elevation data of the fracture surfaces, the process of fiacture for each specimen was rebuilt and the variation of COA and CTOA with the crack extension was easily obtained. The results for specimens A, B, C and D are shown in Figs. 6-9 respectively. From the results shown above, it is very clear that, no matter whether it is for material 1 or material 2 or if it is for the CCT specimen or the DEN specimen, COA decreases with the extension of crack and CTOA becomes almost constant after the initial transient period. Also, from these graphs, it is clear that material 2 displays higher ductility than material 1, because at the transient period the values of COA and CTOA for material 2 are much higher than those of material 1. On the other hand, the critical CTOA 25 \
20-
B a- 15 8
i , I
- - Radical approximation . , (CTOA)
-
Radical approximation (COA)
10\
80
o
0 '
I-
5 -
- *.-- - -
-
0,
0
9-
0
-0,:
0
-"
I
I
CTOA Radical approximation (CTOA) Radical approximation (COA)
0 10-
--
a
-0 -
2
----a
6
4
lo
'd
12
Crack extension, mm
Fig.7 Variation of CTOA and COA with crack extension for specimen B. 45 40 . I
35
CTOA
--
'
Radical approximation (CTOA) Radical approximation (COA)
30. 25.
t) 2 0 .
; I-
u
15. 10' 5 .
01 0
1
2
3
4
5
I
6
Crack extension, mm
Fig.8 Variation of CTOA and COA with crack extension for specimen C.
. 170 35 30 ..
,I
CTOA
- - Radical approximation (CTOA)
-
Radical approximation (COA)
0
?
15-
2 10I-
-0.0
501 0
2
-K
%4
n-
---
-cI~
6
0
~
10
Crack extension. rnrn
Fig.9 Variation of CTOA and COA with crack extension for specimen D.
for material 2 is much higher than that for material 1. From the results, this paper finds that for the same material, the critical CTOA obtained from the CCT specimen equals that obtained from the DEN specimen.
6. Conclusions FRASTA simulation software-FSA was developed. The procedure and principle for software development was introduced. A series of CCT and DEN specimen experiments were performed. Elevation data of fracture surfaces was analyzed by FSA to verify the validity of it. From the results of the research, this paper reaches the following conclusions: (1 ) FSA can accurately simulate the process of fracture for three types of specimens- CT, CCT and DEN; FSA can accurately calculate the values of parameters of crack during the course of fracture process simulation. (2) COA decreases with the extension of crack, whereas CTOA becomes almost constant after the initial transient period. (3) The critical CTOA can be easily determined using the FRASTA technique. For the same material, the critical CTOA obtained from the CCT specimen equals that obtained from the DEN specimen.
REFERENCES
11 (1991)28. Sin. (Engl. Lett.) 18 (2005) 594.
1 T. Kobayashi and D.A. Shockey, Advanced Materials & Bocesses
2 Y.G.Cao and K. Tanaka, Acta Metdl.
@
DIRECT.
ACTA METALLURGICA SINICA (ENGLISH LETTERS)
Acts Metall. Sin. (Engl. Lett.)Vol. 19 No.3 pp 165-170 Jun. 2006
www.ams.org.cn
DEVELOPMENT OF FRASTA SIMULATION SOJTWARE Y.G. Cao* and K. Tanaka Department of Mechanical Systems Engineering, Toyama Prefectural University, Toyama 939-0398, Japan Manuscript received 21 November 2005
I
Fracture-surface topography analysis (FRASTA) was successjklly used to simulate the process of crack and calculate parameters of crack such as the crack opening angle (COA) and crack-tip opening angle (CTOA). But because the amount of calculation is large, errors are ofen made during the course of calculation. FRASTA simulation sojiware, namely frncture surface analyst (FSA) is developed and a series of center-cracked tension (CCT) and double edge notched (DEN) specimens of different materials with different sizes are tested, theirfracture surfaces are scanned by mn-contact 3 0 scanning qstem and the elevation data of the fracture surfaces is recor&d. FSA used the recorded elevation data offrcture surfaces to simulate the process of crack based on the prinsiple of FRASTA. Results show that FSA can accurately simulate the process and calculate the parameters of crack. m y WORDS FRASTA Vracture-surface topography analysis); COA (crack opening angle): CTOA (crack-tip opening angle); CCT (center-cracked tension); DEN (double edge notched)
1. Introduction A new method, using the principle of FRASTA (fracture-surface topography analysis)['], which matches the conjugate fracture surfaces of the broken component together, to the initial position (the position before crack extended) and considers the coincidence as the plastic deformation during the course of fracture, for determining the parameters of COA (crack opening angle) and CTOA (crack-tip opening angle) is provided in Ref.[2]. The fracture surfaces were scanned by a non-contact 3D measuring system and the elevation data was recorded. The cross-sectional plots were extracted to be analyzed. By comparing the crack extension, plastic rotation factor, and COA obtained by the method of double clip gauge and by this new method respectively, the validity of it was verified. It was then used to determine the CTOA, which is unavailable by the elastic compliance method. The critical CTOA was well determined in Ref.[2]. By the new method, it is very convenient to extract a pair of cross-sectional plots at any loca*Corresponding author. Tel.: +81 76 6567500; fax: +81 76 6566131 E-nail address : caoyuguangogrnail .corn ( Y . G. Cao)
. 166
tion through specimen thickness. The variation of crack opening deformation (COA and CTOA) through specimen thickness could be obtained easily, as it is very difficult to obtain it by the usual methods. It was found that COA was more stable than CTOA through specimen thickness and was more appropriate to be used as the parameter to direct the extension of crack when using this method. It was verified in Ref.[2] that the result of the new method could match the result of the elastic compliance method well. All in all, the method provides a new way to extract usehl information that is left on the fracture surface and could be applied easily. But, according to the experience, it is formidable work to process the fracture surface elevation data and deduce the results. At the same time, errors are often made during the course of calculation by hand. Both of them decreased the credibility and accuracy of the application of this method. Thus, it is necessary to develop FRASA simulation software that can do the work well to save time and improve precision.
2. Experimental The specimen type discussed in Ref.[2] is CT (cracked tension). The CT specimen is one of the most widely used in the field of crack research. Because the CCT (center-cracked tension) and DEN (double edge notched) specimens are also widely used, especially when creating a model to solve the practical problem, in this research, the software is developed to analyze the process of crack of these three types of specimens-CT, CCT and DEN. But because the experimental procedure and results for the CT specimen were discussed in Ref.[2], this paper will focus on the CCT and DEN specimens. In this paper, two kinds of alloy steel are used for testing. The chemical compositions of them are shown in Table 1. They are manufactured into CCT and DEN specimens as shown in Fig. 1. The sizes of specimens tested in this paper are shown in Table 2.
Material
C
1
0.1 0.045
2
Table 1 Chemical compositions (wt%) of materials Al P S Mn Si 0.03 0.02 0.004 0.01 1.3 0.03 0.02 0.01 0.01 0.2
C
0 (a)
Fig. 1 Specimens:(a) CCT specimen and (b) DEN specimen.
N 0.04
Ti 0.06
0.03
0
.
167 .
Table 2 Specimens being tested Number A
B C D
Material 1
Tvoe CCT
1
DEN
2
CCT
2
DEN
W. mm 60 60 70 I0
H , mm 300 300 300 300
B, mm 4.5 4.5 4.5 4.5
2aJW 0.5
0.6 0.62 0.56
Fig.2 Setups of measuring displacement for two specimen: (a) CCT specimen and (b) DEN specimen.
The setup for measuring the displacement for CCT and DEN specimens are shown in Figs. 2a and b. For the CCT specimen, as shown in Fig.2a, a clip gauge is used to measure the load-line displacement and for the DEN specimen, as shown in Fig.2b, a clip gauge and a ring gauge are used to measure the displacement at both crack mouths of the specimen.
3. Development of Program The new method introduced in Ref.[2] can accurately calculate the parameter of crack such as COA and CTOA. In order to make the calculation more accurate and make it possible for those who do not have much experience in this field to do this work, FSA (fracture surface analyst) was developed in this paper. The software is developed under the operating system of Microsoft Windows XP Professional with the platform of Microsoft Visual Basic 6.0. The procedure of functions that the software fulfilled is shown in Fig.3, where, the matching of conjugate fracture
Input elevabon data of upper a d Iwerfractue surfaces
I
I
Simulate the p m a of fracture and calculate the values of parameterS
Fig.3 Procedure of FSA.
I
168 . surfaces precisely and the selection of field for analysis are the most important and difficult. The effects of these two steps very much influence the results of the analysis. The process of fracture of the DEN specimen can be expressed by Fig.4. Because the process of fracture for the CCT specimen is very similar to that of the DEN specimen, it will not be discussed in this paper. After the fracture, the fracture surfaces are scanned by non-contact 3D measuring system and the elevation data is recorded so it can be analyzed by FSA. According to FRASTA, using the elevation data of the fracture surfaces to simulate the process of fracture, it can be expressed as shown in Fig.5, for the DEN specimen. In this paper, we developed FSA according to the procedure shown in Fig.3, step by step, to fulfill the functions necessary for fracture process simulation and parameter calculations.
E
b
recrack
Specimen upper half Upper fracture surface Pre-crack
,
Lower fracture surface Specimen l m r haii
Fig.4 Process of fracture for the DEN specimen.
Fig.5 Process of matching the conjugate fracture surfaces of the DEN specimen: (a) the upper fracture surface, which is inverted along specimen thickness direction; (b) the upper fracture surface is mirrored to correlate the lower fracture surface; (c) the position of the upper and lower surfaces are adjusted to make the pre-crack match each other precisely; (d) the upper and lower surfaces are moved according to the displacement recorded at both crack mouths and (e) final state when simulation finished.
. 169 .
4. Results Using FSA, after inputting the recorded elevation data of the fracture surfaces, the process of fiacture for each specimen was rebuilt and the variation of COA and CTOA with the crack extension was easily obtained. The results for specimens A, B, C and D are shown in Figs. 6-9 respectively. From the results shown above, it is very clear that, no matter whether it is for material 1 or material 2 or if it is for the CCT specimen or the DEN specimen, COA decreases with the extension of crack and CTOA becomes almost constant after the initial transient period. Also, from these graphs, it is clear that material 2 displays higher ductility than material 1, because at the transient period the values of COA and CTOA for material 2 are much higher than those of material 1. On the other hand, the critical CTOA 25 \
20-
B a- 15 8
i , I
- - Radical approximation . , (CTOA)
-
Radical approximation (COA)
10\
80
o
0 '
I-
5 -
- *.-- - -
-
0,
0
9-
0
-0,:
0
-"
I
I
CTOA Radical approximation (CTOA) Radical approximation (COA)
0 10-
--
a
-0 -
2
----a
6
4
lo
'd
12
Crack extension, mm
Fig.7 Variation of CTOA and COA with crack extension for specimen B. 45 40 . I
35
CTOA
--
'
Radical approximation (CTOA) Radical approximation (COA)
30. 25.
t) 2 0 .
; I-
u
15. 10' 5 .
01 0
1
2
3
4
5
I
6
Crack extension, mm
Fig.8 Variation of CTOA and COA with crack extension for specimen C.
. 170 35 30 ..
,I
CTOA
- - Radical approximation (CTOA)
-
Radical approximation (COA)
0
?
15-
2 10I-
-0.0
501 0
2
-K
%4
n-
---
-cI~
6
0
~
10
Crack extension. rnrn
Fig.9 Variation of CTOA and COA with crack extension for specimen D.
for material 2 is much higher than that for material 1. From the results, this paper finds that for the same material, the critical CTOA obtained from the CCT specimen equals that obtained from the DEN specimen.
6. Conclusions FRASTA simulation software-FSA was developed. The procedure and principle for software development was introduced. A series of CCT and DEN specimen experiments were performed. Elevation data of fracture surfaces was analyzed by FSA to verify the validity of it. From the results of the research, this paper reaches the following conclusions: (1 ) FSA can accurately simulate the process of fracture for three types of specimens- CT, CCT and DEN; FSA can accurately calculate the values of parameters of crack during the course of fracture process simulation. (2) COA decreases with the extension of crack, whereas CTOA becomes almost constant after the initial transient period. (3) The critical CTOA can be easily determined using the FRASTA technique. For the same material, the critical CTOA obtained from the CCT specimen equals that obtained from the DEN specimen.
REFERENCES
11 (1991)28. Sin. (Engl. Lett.) 18 (2005) 594.
1 T. Kobayashi and D.A. Shockey, Advanced Materials & Bocesses
2 Y.G.Cao and K. Tanaka, Acta Metdl.