Effects of process variables on fretting fatigue crack initiation in Ti-6A1-4V

2002 ◽  
Vol 37 (6) ◽  
pp. 535-547 ◽  
Author(s):  
S A Namjoshi ◽  
S Mall ◽  
V K Jain ◽  
O Jin
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Coefficient Of Friction ◽  
Fatigue Crack Initiation ◽  
Orientation Angle ◽  
Fretting Fatigue ◽  
Multiaxial Fatigue ◽  
Process Variables ◽  
Critical Plane ◽  
The Coefficient Of Friction

A fretting fatigue crack initiation mechanism (number of cycles, location and orientation angle) using critical plane based parameters has been addressed by several researchers. There are several process variables that can affect these parameters and thereby the prediction of fretting fatigue crack initiation behaviour. Effects of two such parameters, viz. process volume and the coefficient of friction, were investigated in this work. Fretting fatigue experiments with a titanium alloy were conducted with different contact pad geometries. Finite element analysis (FEA) was used to obtain a stress state in specimens for the experimental conditions used during fretting fatigue tests. Analysis was carried out for two values of the coefficient of friction, thereby providing a framework for calculation of several critical plane based multiaxial fatigue parameters for different process volumes. A program was developed to compute these multiaxial fatigue parameters from the FEA data for different values of process variables. It was observed that parameters for cylindrical pad geometries with no singularity-type behaviour were inversely proportional to the size of process volume and directly proportional to the coefficient of friction. There was no change in the predicted orientation of the primary crack for this geometry, due to variations in these process variables. Parameters for flat-pad geometries with behaviour approaching that of a singularity were also inversely proportional to the size of process volume, but the coefficient of friction had a minimal effect on their values. Predicted orientation of the primary crack for these geometries changed slightly when the process volume increased from that of a grain size of the tested material to a larger size, and then did not change with the increase of process volume size. Overall, the effect of these process variables on the critical plane based parameters was similar in all five contact geometries used in this study, when the scatter in fatigue data is kept in mind. Finally, the modified shear stress range parameter satisfactorily predicted the crack initiation location, orientation angle and number of cycles to fretting fatigue crack initiation independent of the contact geometry for a given process volume size and coefficient of friction.

Fatigue Life Evaluation of Press-Fitted Specimens by Using Multiaxial Fatigue Theory at Contact Edge

2005 ◽  
Vol 297-300 ◽  
pp. 108-114 ◽  
Author(s):  
Dong Hyung Lee ◽  
Byeong Choon Goo ◽  
Chan Woo Lee ◽  
Jae Boong Choi ◽  
Young Jin Kim
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Fretting Fatigue ◽  
Cyclic Stress ◽  
Multiaxial Fatigue ◽  
Critical Plane ◽  
Bending Load ◽  
The Press ◽  
Number Of Cycles

In the shrink or press-fitted shafts such as railway axles, fretting can occur by cyclic stress and micro-slippage due to local movement between shaft and boss. When the fretting occurs in the press-fitted shaft, the fatigue strength remarkably decreases compared with that of without fretting. In this paper fretting fatigue life of press-fitted specimens was evaluated using multiaxial fatigue criteria based on critical plane approaches. An elastic-plastic analysis of contact stresses in a press-fitted shaft in contact with a boss was conducted by finite element method and micro-slip due to the bending load was analyzed. The number of cycles of fretting fatigue and the crack orientation were compared with the experimental results obtained by rotating bending tests. It is found that the crack initiation of fretting fatigue between shaft and boss occurs at the contact edge and the normal stress on the critical plane of contact interface was an important parameter for fretting fatigue crack initiation. Furthermore, the results indicated that a critical plane parameter could predict the orientation of crack initiation in the press-fitted shaft.

scholarly journals A fatigue crack initiation and growth life estimation method in single-bolted connections

2019 ◽  
Vol 54 (2) ◽  
pp. 79-94 ◽  
Author(s):  
Arash P Jirandehi ◽  
TN Chakherlou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Estimation Accuracy ◽  
Life Estimation ◽  
Lower Error ◽  
Fatigue Life Estimation

Fatigue life estimation accuracy of mechanical parts and assemblies has always been the source of concern in different industries. The main contribution of this article lies in a study on the accuracy of different multiaxial fatigue criteria, proposing and investigating the accuracy of four optimized fatigue crack initiation life estimation methods—volume, weighted volume, surface and point, thereby improving the multiaxial fatigue life estimation accuracy. In order to achieve the goal, the fatigue lives of bolt clamped specimens, previously tested under defined experimental conditions, were estimated during fatigue crack initiation and fatigue crack growth and then summed together. In the fatigue crack initiation part, a code was written and used in the MATLAB software environment based on critical plane approach and the different multiaxial fatigue criteria. Besides the AFGROW software was utilized to estimate the crack growth share of fatigue life. Experimental and numerical results showed to be in agreement. Furthermore, detailed study and comparison of the results with the available experimental data showed that a combination of Smith–Watson–Topper approach and volume method results in lower error values, while a combination of Fatemi–Socie criterion and surface or point method presents estimated lives with lower error values. In addition, the numerical proposed procedure resulted in a good prediction of the location of fatigue crack initiation.

Assessment of Degrees of Cumulative Fatigue Crack Initiation Damage at Guyed Mast Earplate Joint

2011 ◽  
Vol 467-469 ◽  
pp. 776-781
Author(s):  
Wen Li Wang ◽  
Wei Lian Qu ◽  
Jie He
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Welding Residual Stress ◽  
Critical Plane ◽  
Multi Scale ◽  
Cumulative Strain ◽  
Critical Plane Approach ◽  
Guyed Mast

This paper proposes a new method for assessing the degree of the cumulative fatigue crack initiation damage of the joint welds at the guyed mast earplate. Based on the multi-scale wind-induced stress analysis of the guyed mast earplate joint, and considering the welding residual stress in earplate joint, the critical plane approach is used for the calculation of cumulative strain fatigue damage due to the combined actions of the welding residual stress and the wind load.

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