scholarly journals Experimental Investigation on the Fatigue Life of Ti-6Al-4V Treated by Vibratory Stress Relief

Metals ◽  
2017 ◽  
Vol 7 (5) ◽  
pp. 158 ◽  
Author(s):  
Han-Jun Gao ◽  
Yi-Du Zhang ◽  
Qiong Wu ◽  
Jing Song
Keyword(s):  
Experimental Investigation ◽  
Fatigue Life ◽  
Stress Relief

Applicability of Equivalent Constant Amplitude Loading for Assessing the Fatigue Life of Pipelines and Risers and the Influence of Compressive Stress Cycles

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri
Keyword(s):  
Experimental Investigation ◽  
Fatigue Life ◽  
Compressive Stress ◽  
Time History ◽  
Life Assessment ◽  
Constant Amplitude ◽  
Safety Factors ◽  
Variable Amplitude ◽  
Fatigue Life Assessment ◽  
Stress Cycles

Fatigue life assessment of pipelines and risers is a complex process, involving various uncertainties. The selection of an appropriate fatigue model is important for establishing the inspection intervals and maintenance criteria. In offshore structures, the vortex-induced vibration (VIV) could cause severe fatigue damage in risers and pipelines, resulting in leakage or even catastrophic failure. The industry has customarily used simple fatigue models for fatigue life assessment of pipelines and risers (such as the Paris or Walker models); however, these models were developed based on constant amplitude loading scenarios. In contrast, VIV-induced stress-time history has a variable amplitude nature. The use of the simplified approach (which is inherently non conservative), has necessitated the implementation of large safety factors for fatigue design of pipelines and risers. Moreover, most of the experimental investigations conducted to date with the aim of characterizing the fatigue response of pipelines and risers have been done based on incorporation of constant amplitude loading (CAL) scenarios (which is unrealistic), or converting the variable amplitude loading (VAL) scenarios to an equivalent CAL. This study demonstrates that the use of such approaches would not be lead to accurate assessment of the fatigue response of risers subject to VIV-induced VAL. The experimental investigation performed in this study will also clarify the underlying reasons for the use of large safety factors by the industry when assessing the fatigue life of pipelines and risers. In addition, an experimental investigation was also conducted to highlight the influence of the compressive portion of VIV stress-time history on the fatigue life of such components. It is shown that the compressive stress cycles significantly influence the fatigue crack growth response of risers, and their presence should not be ignored.

Stress Relief in Solder Joints Due to the Application of a Flex Circuit

1991 ◽  
Vol 113 (3) ◽  
pp. 240-243 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Fatigue Life ◽  
Stress Analysis ◽  
Solder Joints ◽  
Stress Relief ◽  
Physical Design ◽  
Thermal Contraction ◽  
Analysis Model ◽  
Rigid Substrate

A stress analysis model is developed to assess the stresses in solder joints caused by thermal contraction mismatch between a low expansion flex-circuit (FC) and a high expansion rigid substrate. It is shown that application of low expansion FCs can result in significant stress relief for solder joints. This is due to the fact that the force acting on a joint cannot exceed the buckling force for the adjacent portion of the FC. It is shown that the strains in solder joints interconnecting FCs to rigid substrates can be made very small, thereby resulting in a substantially longer fatigue life of the interconnection. In the executed example these strains are about two orders of magnitude smaller, than in the case of a rigid board. The obtained results can be utilized as guidance in physical design of assemblies with FCs.

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