Browsing by Author "Lu, ML"

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Effect of temperature on fracture toughness of PC/ABS based on J-integral and hysteresis energy methods
(1996-11-07)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The critical fracture toughness J(1c) of the polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend at different temperatures was obtained from ASTM E813-81, E813-87, and the recently developed hysteresis energy methods, respectively. The J(1c) value increases with increase of the test temperature ranging from -60 to 70 degrees C. The hysteresis energy method and the ASTM E813-81 method result in comparable J(1c) values, while the ASTM E813-87 results in about 80-110% higher values. The critical initiation displacements determined from the plots of hysteresis energy and the true crack growth length vs. crosshead displacement are very close. This indicates that the critical initiation displacement deter mined by the hysteresis method is indeed the displacement at the onset of true crack initiation and the corresponding J(1c) represents a physical event of crack initiation. The fracture toughness, K-1c value, based on linear elastic fracture mechanics (LEFM), was determined by using K-Q analysis (ASTM E399-78), and the obtained K-Q value decreases with the increase of the test temperature. The K-Q value is not the real LEFM K-1c value because the criterion of P-max/P-Q < 1.1 has not been satisfied. However, the corresponding J(Q) obtained from the K-Q analysis is comparable to the J(1c) obtained from the E813-81 method at lower temperature (-45 or -60 degrees C), an indication of LEFM behavior at lower temperature. The various schemes and size criterion based on LEFM and the J-method are explored for the validity of J(1c) and K-1c values. (C) 1996 John Wiley & Sons, Inc.
Effect of temperature on fracture toughness of PC/ABS based on J-integral and hysteresis energy methods
(1996-11-07)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The critical fracture toughness J(1c) of the polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend at different temperatures was obtained from ASTM E813-81, E813-87, and the recently developed hysteresis energy methods, respectively. The J(1c) value increases with increase of the test temperature ranging from -60 to 70 degrees C. The hysteresis energy method and the ASTM E813-81 method result in comparable J(1c) values, while the ASTM E813-87 results in about 80-110% higher values. The critical initiation displacements determined from the plots of hysteresis energy and the true crack growth length vs. crosshead displacement are very close. This indicates that the critical initiation displacement deter mined by the hysteresis method is indeed the displacement at the onset of true crack initiation and the corresponding J(1c) represents a physical event of crack initiation. The fracture toughness, K-1c value, based on linear elastic fracture mechanics (LEFM), was determined by using K-Q analysis (ASTM E399-78), and the obtained K-Q value decreases with the increase of the test temperature. The K-Q value is not the real LEFM K-1c value because the criterion of P-max/P-Q < 1.1 has not been satisfied. However, the corresponding J(Q) obtained from the K-Q analysis is comparable to the J(1c) obtained from the E813-81 method at lower temperature (-45 or -60 degrees C), an indication of LEFM behavior at lower temperature. The various schemes and size criterion based on LEFM and the J-method are explored for the validity of J(1c) and K-1c values. (C) 1996 John Wiley & Sons, Inc.
Elastic-plastic fracture toughness of PC/ABS blend based on CTOD and J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The elastic-plastic fracture toughness of a PC/ABS blend has been investigated simultaneously by the conventional J-integral and the crack tip opening displacement (CTOD) methods for specimen thickness varying from 4 to 15 mm. The critical J (J(c)) and the critical CTOD (delta(c)) are-based on crack initiation. Another new method to determine J(c) based on the close relationship between the J-integral and CTOD has also been developed. Those three critical J(c) values, J(c-81), J(c-NEW), and J(c-BS) Obtained from the ASTM E813-81, the new J method, and the equation J(c) = m sigma(y) delta(c) (1-nu(2)) of the CTOD method, are comparable and are independent of the specimen thickness. The constraint factor m evaluated from the linear elastic fracture mechanics (LEFM) approach using the Dugdale model is about 1.5. A rotation factor r(g) of approximately 2 g was obtained which is also independent of the specimen thickness. The crack propagation resistance, J-curve (dJ/da) or delta-curve (d delta/da), decreases with increasing specimen thickness. A close relationship between CTOD and J-integral has been demonstrated in this study. Copyright (C) 1996 Elsevier Science Ltd.
Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A published, nonconventional J-integral method, based on the hysteresis energy and the ASTM E813 methods, has been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The critical J values (J(Ic)) at crosshead speeds ranging from 0.5 to 20 mm/min obtained from the hysteresis energy method are similar to 10 to 20% higher than those obtained from the E813-81 method and similar to 50 to 70% lower than those obtained from the E813-87 method. However, the hysteresis energy method results in comparable J(Ic) values with a modified ASTM E813-87 method when the 0.2 mm offset line is replaced with a 0.1 mm offset line. The critical displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vs. displacement, hysteresis ratio vs. displacement, and the true crack growth length vs. displacement, are fairly close in value. This indicates the critical crack initiation and the corresponding J(Ic) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.
Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods
(1996-09-01)
Lu, ML
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A published, nonconventional J-integral method, based on the hysteresis energy and the ASTM E813 methods, has been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The critical J values (J(Ic)) at crosshead speeds ranging from 0.5 to 20 mm/min obtained from the hysteresis energy method are similar to 10 to 20% higher than those obtained from the E813-81 method and similar to 50 to 70% lower than those obtained from the E813-87 method. However, the hysteresis energy method results in comparable J(Ic) values with a modified ASTM E813-87 method when the 0.2 mm offset line is replaced with a 0.1 mm offset line. The critical displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vs. displacement, hysteresis ratio vs. displacement, and the true crack growth length vs. displacement, are fairly close in value. This indicates the critical crack initiation and the corresponding J(Ic) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.