Field Effects in Fatigue Crack Initiation: Long Life Fatigue Strength

1991 ◽  
Vol 113 (2) ◽  
pp. 188-194 ◽  
Author(s):  
S. D. Sheppard
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Notch Root ◽  
Fatigue Crack Initiation ◽  
Stress Fields ◽  
Complex Geometries ◽  
The Finite Element Method ◽  
Long Life

This work is focused on explaining observed fatigue crack initiation behavior in notched members in terms of the stress state in a finite volume at the notch root. In principle, this is no different than the work of several other researchers. What is different is the manner in which the stress fields were predicted; namely using the finite element method. By using this approach, no approximations were necessary as to the form of the stress field at the notch root. This implies that this approach is extendable to complex geometries and to the finite life regime where plastic flow is expected at the notch root.

Fatigue Crack Initiation in Solder Joints

1996 ◽  
Vol 118 (2) ◽  
pp. 41-44 ◽  
Author(s):  
Z. Zhang ◽  
Daping Yao ◽  
J. K. Shang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Solder Joints ◽  
Fatigue Crack Initiation ◽  
Lap Joints ◽  
Stress Cycle ◽  
Fatigue Lifetime ◽  
Peak Value

A backface strain technique is introduced to examine fatigue crack initiation in solder lap joints. The technique detects the fatigue crack initiation by monitoring the backface strain at the end of the overlap. Variation of the backface strain with the development of a crack was simulated by finite element method. The simulation indicated that the backface strain at the end of the overlap reached a peak value when a fatigue crack initiated. Experimental verification was carried out in 63Sn-37Pb solder joints. The backface strain was recorded as a function of stress cycle to demonstrate the applicability of this technique. Experimental results showed that fatigue crack initiation took about half of the fatigue lifetime of the solder joints.

scholarly journals Study of fatigue crack initiation location of wheel and rail under rolling contact using finite element method

2018 ◽  
Vol 192 ◽  
pp. 02012 ◽  
Author(s):  
Apichai Jaifu ◽  
Suthep Raeon ◽  
Monsak Pimsarn
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Rolling Contact ◽  
Lateral Direction ◽  
Transit System ◽  
Element Method

The rail transit system is widely used for freight and passenger transportation. Due to the fact that its economic worthiness and high safety mode. Maintenance and damage prevention of wheel and rail are important factors affecting the safety of the system. The previous studies show that the most damage of wheel and rail is fatigue cracking, which is caused by the contact stress resulting from wheel and rail interaction. This article presents the study of the fatigue crack initiation location of wheel and rail under rolling contact at the wheel speed of 80 km/h using Finite Element Method (FEM). The three dimensional finite element models were created using the UIC60E1 wheel profile and BS100 rail profile. The Dang Van criteria was applied to analyse the fatigue crack initiation location in case of the wheel's position was changed along the rail lateral direction while the rail inclination angle was also varied at 0, 1/40, 1/30 and 1/20, respectively. The analysing results show that the fatigue crack initiation, determined by the Dang Van stress ratio, tends to increase when the wheel is moved from gauge side to field side. Additionally, the fatigue crack damage is likely to decrease when the rail inclination increases up to the inclination of 1/30 and the fatigue crack initiation locations were found underneath the wheel and rail surfaces. The obtained result can be a primary guideline for maintenance planning.

Simulation of Fatigue Crack Initiation in Heat Affected Zone Microstructure Using Crystal-Plasticity Finite Element Method

2017 ◽  
Author(s):  
Takashi Hiraide ◽  
Satoshi Igi ◽  
Tetsuya Tagawa ◽  
Rinsei Ikeda ◽  
Seiichiro Tsutsumi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Crystal Plasticity ◽  
Heat Affected Zone ◽  
Fatigue Crack Initiation ◽  
Crystal Plasticity Finite Element ◽  
Microstructural Effects ◽  
Inhomogeneous Microstructure

It is well known that fatigue fracture of welded joints can depend on many factors such as residual stress, stress concentration and an inhomogeneous microstructure in the HAZ (Heat Affected Zone). Some solutions to improve fatigue properties, for example, hammer peening (1), have been developed to mitigate effects related to stress. Improvement from mechanical view point is not only applied, but optimized microstructure design of the base metal and HAZ should be also considered. However, microstructural effects on fatigue crack initiation behavior have not been fully understood because systematic experimental evaluation of them takes much efforts with difficulty. An analytical method is a useful idea to specify the optimum microstructure against fatigue crack initiation before experimental examinations. CP-FEM (Crystal-Plasticity Finite Element Method) is expected to describe fatigue crack initiation behavior, because it can express strain localizations caused by an inhomogeneous microstructure. In the present study, a simulation model using CP-FEM is developed to describe strain localizations under cyclic loading. Microstructural effects on plastic strain localization and accumulation were investigated by changing microstructural factors.

Calculation of Fatigue Crack Initiation Life by Coupled Finite Element Method

2013 ◽  
Vol 275-277 ◽  
pp. 189-192
Author(s):  
Wen Feng Tan ◽  
Tao Chen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Stiffness Matrix ◽  
Damage Evolution ◽  
Fatigue Crack Initiation ◽  
Critical Element ◽  
Crack Initiation Life ◽  
Element Method

Applied damage mechanics and coupled finite element method, to study the fatigue crack initiation life problem. Application of coupling finite element method, the damage coupling effect can be modified through the global stiffness matrix to achieve. The step length of the damage evolution is divided by the damage variable of the critical element, and then the damage evolution is analysised. The corresponding stiffness matrix and loading matrix can be obtained continually under the condition of increasing the damage evolution step of the critical element,then the equivalent stress can be calculated. The corresponding fatigue crack initiation life can be calculated by using the damage evolution equation, the progress will not stop until the damage degree of the critical element reaches to one. The fatigue crack initiation life is obtained by adding the fatigue crack initiation lives with different damage variable.

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