Study on Weld Fatigue Evaluation Incorporating Welding Induced Residual Stress Effect

2016 ◽  
Author(s):  
Jeong K. Hong
Keyword(s):  
Residual Stress ◽  
Applied Load ◽  
Fatigue Behavior ◽  
Load Ratio ◽  
Stress Effect ◽  
Structural Stress ◽  
Applied Loading ◽  
Welded Structure ◽  
Residual Stress Effect ◽  
Weld Fatigue

For fatigue assessment of a welded structure, an important characteristic is the failure location. The fatigue crack begins from the pre-existing crack-like flaw which is an inherent feature of a weld toe or root. Residual stress in the welded joints is another important characteristic. It is also well known that tensile residual stress in welded structures can be as high as the material yield strength level and so the fatigue strength of the welded joint is governed by the applied stress range regardless of the applied load ratio. However, when the presumed conditions with high tensile residual stress in the weld regime are not satisfied, the fatigue behavior in welded structure deviates from the general weld fatigue behavior. In this paper, firstly the applied load ratio effect on fatigue behavior is investigated for two different residual stress levels of welds, i.e., as-welded and stress relieved. It has been observed that stress-relieving effect of welds is apparent when the applied loading introduces stress fluctuations in compressive loading. When the load ratio effect is considered in Battelle structural stress based fatigue parameter, the stress relieved weld fatigue data was consolidated within the master S-N curve. Based on this investigation, the Battelle structural stress based effective load ratio considering both applied loading and detailed residual stress is introduced for the weld fatigue behavior. The two-stage crack growth model is reformulated with the structural stress based effective load ratio, which is a function of crack length. Lastly, a fatigue life prediction procedure incorporating residual stress effect is proposed and validated using the existing fatigue test results. The proposed procedure clearly shows that the compressive residual stress distributions at the weld prone to crack provide great benefits for fatigue life improvement.

Micromechanical Modeling of Viscoplastic Behavior of Laminated Polymer Composites With Thermal Residual Stress Effect

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Qiang Chen ◽  
Xuefeng Chen ◽  
Zhi Zhai ◽  
Xiaojun Zhu ◽  
Zhibo Yang
Keyword(s):  
Residual Stress ◽  
Polymer Matrix Composites ◽  
Micromechanical Model ◽  
Thermal Residual Stress ◽  
Micromechanical Modeling ◽  
Multiscale Approach ◽  
Stress Effect ◽  
Accurate Analysis ◽  
Rate Dependent ◽  
Residual Stress Effect

In this paper, a multiscale approach has been developed for investigating the rate-dependent viscoplastic behavior of polymer matrix composites (PMCs) with thermal residual stress effect. The finite-volume direct averaging micromechanics (FVDAM), which effectively predicts nonlinear response of unidirectional fiber reinforced composites, is incorporated with improved Bodner–Partom model to describe the viscoplastic behavior of PMCs. The new micromechanical model is then implemented into the classical laminate theory, enabling efficient and accurate analysis of multidirectional PMCs. The proposed multiscale theory not only predicts effective thermomechanical viscoplastic response of PMCs but also provides local fluctuations of fields within composite microstructures. The deformation behaviors of several unidirectional and multidirectional PMCs with various fiber configurations are extensively simulated at different strain rates, which show a good agreement with the experimental data found from the literature. Influence of thermal residual stress on the viscoplastic behavior of PMCs is closely related to fiber orientation. In addition, the thermal residual stress effect cannot be neglected in order to accurately describe the rate-dependent viscoplastic behavior of PMCs.

scholarly journals Superlayer Residual Stress Effect on the Indentation Adhesion Measurements

1999 ◽  
Vol 594 ◽  
Author(s):  
Alex A. Volinsky ◽  
Neville R. Moody ◽  
William W. Gerberich
Keyword(s):  
Residual Stress ◽  
Sputter Deposition ◽  
Work Of Adhesion ◽  
Stress Effect ◽  
Aluminum Films ◽  
Nanoindentation Testing ◽  
Deposition Parameters ◽  
Thin Aluminum ◽  
Residual Stress Effect ◽  
Sputter Deposited

AbstractThe practical work of adhesion has been measured in thin aluminum films as a function of film thickness and residual stress. These films were sputter deposited onto thermally oxidized silicon wafers followed by sputter deposition of a one micron thick W superlayer. The superlayer deposition parameters were controlled to produce either a compressive residual stress of 1 GPa or a tensile residual stress of 100 MPa. Nanoindentation testing was then used to induce delamination and a mechanics based model for circular blister formation was used to determine practical works of adhesion. The resulting measured works of adhesion for all films between 100 nm and 1 μm thick was 30 J/m2 regardless of superlayer stress. However, films with the compressively stressed superlayers produced larger blisters than films with tensile stressed superlayers. In addition, these films were susceptible to radial cracking producing a high variability in average adhesion values.

A Fundamental Study of the Interaction of Residual Stress and Applied Loading on Fracture

2010 ◽  
Author(s):  
C. J. Aird ◽  
M. J. Pavier ◽  
D. J. Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Crack Closure ◽  
Applied Load ◽  
Element Model ◽  
Residual Stress Field ◽  
Fundamental Study ◽  
Analytical Expression ◽  
Applied Loading

This paper presents the results of a fundamental finite-element based study of the crack-closure effects associated with combined residual and applied loading. First, an analytical expression for a representative two-dimensional residual stress field is derived. This residual stress field contains a central compressive region surrounded by an equilibrating tensile region. The analytical expression allows the size and shape of the field to be varied along with the magnitude of the residual stress. The residual stress field is then used as a prescribed initial stress field in a finite element model, in addition to a far field applied load. By introducing cracks of increasing length into these models, charts of stress-intensity-factor versus crack length are produced for different relative magnitudes of residual stress and applied load and for different sizes and shape of the residual stress field. These charts provide insight into the way in which crack-tip conditions evolve with crack growth under conditions of combined residual and applied loading and also enable conditions of crack closure and partial closure to be identified.

Residual Stress Effect on Performance of Diaphragm-Based MEMS Pressure Transducers

2000 ◽  
Author(s):  
Meng-Nian Niu ◽  
Eun Sok Kim
Keyword(s):  
Residual Stress ◽  
Theoretical Analysis ◽  
Layer Thickness ◽  
Compressive Residual Stress ◽  
Stress Effect ◽  
Layer By Layer ◽  
Pressure Transducers ◽  
Before And After ◽  
Supporting Layer ◽  
Residual Stress Effect

Abstract We experimentally and theoretically confirm that residual stress within a diaphragm is critical in limiting the performance of diaphragm-based piezoelectric microphones even if the stress is low (around 50 MPa). We have fabricated and studied microphones with Al/parylene/ZnO/SiN2/poly-Si/SiN1 (from top to bottom) diaphragm. As the SiN1 supporting layer is removed layer by layer from the backside with CF4 plasma (in an RIE system), we measure both the sensitivity and center displacement of the microphone before and after each RIE etching of the SiN1 from the microphone diaphragm, and find the sensitivity increasing about 5–16 times with the best sensitivity reaching 11 μV/μbar from a mere 0.6 μV/μbar. The center displacement increases very moderately as the SiN1 layer thickness decreases from 0.8 to 0.2 μm. However, the center displacement starts to increase greatly as the SiN1 layer thickness goes below 0.2 μm, which compares with our theoretical analysis well. In the case of the SiN1 layer having compressive residual stress, the compressive stress can enhance the microphone sensitivity and center displacement to a certain extent.

Numerical Calculation of Residual Stress Corrected J-Integral Using ABAQUS

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Stress Effect ◽  
J Integral ◽  
Residual Stress Field ◽  
Path Independence ◽  
Residual Stress Effect ◽  
Senb Specimen

Residual stresses exist in welded structures due to thermal stresses. Without temperature change, large plastic deformation can result in “cold” residual stresses in a wrinkle or dent in a metallic pipe. For a crack in residual stress field, residual stresses might have strong effect on fracture parameter, the J-integral. In order to ensure its path-independence, different correction methods have been developed in consideration of residual stress effect. Recently, the finite element commercial software ABAQUS adopted one of the correction methods, and is able to calculate the residual stress corrected J-integral. A brief review is first given to the J-integral definition, the conditions of path-independence or path-dependence, and the modifications to consider the residual stress effect. A modified single edge-notched bend (SENB) specimen is then used, and a numerical procedure is developed for ABAQUS to evaluate the path-independence of the residual stress corrected J-integral. Detailed elastic-plastic finite element analyses are performed for the SENB specimen in three-point bending. The residual stress field, crack-tip stress field, and J-integral with and without consideration of residual stresses are discussed.

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