A Critical Analysis of Crack Growth in Creep

1980 ◽  
Vol 102 (2) ◽  
pp. 200-206 ◽  
Author(s):  
V. M. Radhakrishnan ◽  
A. J. McEvily
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Experimental Investigations ◽  
Critical Examination ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Reference Stress ◽  
Stress Energy ◽  
Crack Zone ◽  
6061 Al Alloy

Experimental investigations have been carried out to study the crack growth behavior in creep in a 6061 Al alloy. The crack growth rate is analyzed by the stress intensity factor, reference stress, energy rate line integral C* and modified J integral method and a critical examination is made of the applicability of different procedures. Based on the experimental observations near the crack zone, a new parameter in the form [Δ˙ / (P/P0)α], where Δ˙ is the deflection rate, P the applied load and the exponent α and P0 are constants, is proposed to describe the crack growth behavior in ductile materials.

scholarly journals Influence of Pre-Stress Magnitude on Fatigue Crack Growth Behavior of Al-Alloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1267
Author(s):  
Chunguo Zhang ◽  
Weizhen Song ◽  
Qitao Wang ◽  
Wen Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Shot Peening ◽  
Fatigue Property ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Fatigue Crack Growth Behavior

From tensile overload to shot peening, there have been many attempts to extend the fatigue properties of metals. A key challenge with the cold work processes is that it is hard to avoid generation of harmful effects (e.g., the increase of surface roughness caused by shot peening). Pre-stress has a positive effect on improving the fatigue property of metals, and it is expected to strength Al-alloy without introducing adverse factors. Four pre-stresses ranged from 120 to 183 MPa were incorporated in four cracked extended-compact tension specimens by application of different load based on the measured stress–strain curve. Fatigue crack growth behavior and fractured characteristic of the pre-stressed specimens were investigated systematically and were compared with those of an as-received specimen. The results show that the pre-stress ranged from 120 to 183 MPa significantly improved the fatigue resistance of Al-alloy by comparison with that of the as-received specimen. With increasing pre-stress, the fatigue life first increases, then decrease, and the specimen with pre-stress of 158 MPa has the longest fatigue life. For the manner of pre-stress, no adverse factor was observed for increasing fatigue property, and the induced pre-stress reduced gradually till to disappear during subsequent fatigue cycling.

Mode I Ductile Crack Growth of 1TCT Specimen Under Large Cyclic Loading: Part III

2019 ◽  
Author(s):  
Kiminobu Hojo
Keyword(s):  
Cyclic Loading ◽  
Crack Growth ◽  
Large Scale ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mode I ◽  
Piping System ◽  
Ductile Crack ◽  
Reference Stress ◽  
Ductile Crack Growth

Abstract Fitness for service rules and a calculation method for ductile crack growth under large scale plastic cyclic loading have not been established even for Mode I. In a paper presented at the PVP2018 conference the authors presented methods to establish how to determine the parameters of the combined hardening plasticity rule and applied it to simulate the ductile crack growth behavior of 1TCT specimens of the different load levels. Also, ΔJ calculations using the reference stress method, and a ΔJ-basis fatigue crack growth rate derived from that on ΔK-basis according to JSME rules for FFS were applied to estimate the crack growth under cyclic loading in excess of yield. Since in the 2018 paper identified some gaps were found between experiments and the predicted crack growth behavior, several equations of the reference stress method are evaluated in the present paper. Additionally, the prediction procedure using the ΔJ calculation by the reference stress method and the da/dN−ΔJ curve based on the JSME rules for FFS are applied to pipe fracture tests under cyclic loading. Their applicability is discussed for the case of an example piping system.

scholarly journals Crack Growth Behavior of Al Alloy 7075-T6 under Ultrasonic Fatigue

2008 ◽  
Vol 2 (11) ◽  
pp. 1399-1409 ◽  
Author(s):  
Qiang CHEN ◽  
Norio KAWAGOISHI ◽  
Masahiro OKI ◽  
Masahiro GOTO ◽  
Qingyuan WANG
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Ultrasonic Fatigue

107 Crack Growth Behavior of Al Alloy under Ultrasonic Fatigue

2005 ◽  
Vol 2005 (0) ◽  
pp. 13-14
Author(s):  
Norio KAWAGOISHI ◽  
Masahiro OKI ◽  
Masahiro GOTO ◽  
Qiang Chen ◽  
Qingyuan WANG
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Ultrasonic Fatigue

Crack Growth Behavior of Al Alloy under Ultrasonic Fatigue

2006 ◽  
Vol 324-325 ◽  
pp. 327-330
Author(s):  
Norio Kawagoishi ◽  
Q. Chen ◽  
M. Oki ◽  
Qing Yuan Wang
Keyword(s):  
Crack Growth ◽  
Tensile Axis ◽  
Crack Depth ◽  
Growth Direction ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Shear Mode ◽  
Al Alloy ◽  
Ultrasonic Fatigue ◽  
Rotating Bending

In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T6, and the results were compared with those in rotating bending fatigue. Fatigue strength in ultrasonic was higher than that in rotating bending. This was mainly caused by the retardation of crack initiation. Growth direction of a crack changed from a tensile mode to a shear one in ultrasonic fatigue, though fracture occurred by the growth of a tensile mode in rotating bending. The growth direction of a shear mode crack was inclined about 55 degrees to the tensile axis. The relation between an applied stress σa and a crack depth at transition of growth direction T was expressed by a nT=C, where C and n are constants. These results were discussed from the points of view of the time dependent environmental effect and the texture of material.

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