scholarly journals A Study of Residual Stress for Opening and Closing Behavior of Fatigue Cracks

1990 ◽  
Vol 33 (2) ◽  
pp. 227-234
Author(s):  
Yoshitaka NATUME ◽  
Susumu MIYAKAWA
Keyword(s):  
Residual Stress ◽  
Fatigue Cracks ◽  
Opening And Closing

The generation of dislocations during cleavage

1957 ◽  
Vol 242 (1230) ◽  
pp. 392-399 ◽  
Keyword(s):  
Plastic Deformation ◽  
Lithium Fluoride ◽  
Fatigue Cracks ◽  
Important Application ◽  
Cleavage Crack ◽  
Time Estimate ◽  
Moving Crack ◽  
Perfect Cleavage ◽  
Fluoride Crystals ◽  
Opening And Closing

A cleavage crack can generate plastic deformation in a crystal only if it is moving sufficiently slowly or can be brought to rest. This can be demonstrated very strikingly by the cleavage of rock salt or lithium fluoride crystals at a low rate of loading. The cleavage crack propagates discontinuously under these conditions, and thus provides a range of velocities at which deformation might occur. It is found that intense plastic deformation occurs only in narrow zones around the positions where the crack stops; elsewhere the crack runs freely producing a perfect cleavage. It is possible to detect and at the same time estimate the magnitude of this deformation by studying the interference pattern produced by light reflected from the two surfaces of the crack. Observations of this kind allow the deformation to be interpreted as the production of arrays of loops of dislocation by the slowly moving crack. The interference technique is also valuable for displaying the presence of the crack so that its mode of propagation can be studied. A number of observations of the opening and closing of cracks suggest that a study of this kind using a system of reversed stressing might have an important application to the problems of the propagation of fatigue cracks.

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

scholarly journals Residual Stresses in Ultrasonically Peened Fillet Welded Joints

2014 ◽  
Vol 996 ◽  
pp. 755-760 ◽  
Author(s):  
Bilal Ahmad ◽  
Michael E. Fitzpatrick
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Compressive Residual Stress ◽  
Fatigue Cracks ◽  
Steel Plates ◽  
Contour Method ◽  
Mechanical Method ◽  
Accelerated Corrosion ◽  
Accelerated Corrosion Testing ◽  
Measured Residual Stress

Fatigue cracks mostly initiate at areas subjected to high tensile residual stress and stress concentration. Ultrasonic peening is a mechanical method to increase fatigue life by imparting compressive residual stress. In this study residual stresses are characterized in fillet welded ship structural steel plates with longitudinal attachments. As-welded, ultrasonically peened, and specimens peened then subjected to accelerated corrosion testing were measured. Residual stress characterization was performed by the contour method and neutron diffraction.

Effect of Forging Force on Fatigue Behavior of Spot Welded Joints of Aluminum Alloy 5182

2006 ◽  
Vol 129 (1) ◽  
pp. 95-100 ◽  
Author(s):  
B. H. Chang ◽  
D. Du ◽  
B. Sui ◽  
Y. Zhou ◽  
Z. Wang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Welded Joints ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Element Analysis ◽  
Aluminum Alloy 5182 ◽  
Forging Force ◽  
Positive Effect ◽  
Spot Welded

Using experimental and finite element analysis methods, the effects of electrode forging force are investigated on fatigue behavior and residual stress of spot welded joints of aluminum alloy 5182. Results show that applying forging force significantly reduces the residual stresses in the heat affected zone and the fatigue cracks no longer initiate from there; instead, all cracks begin from the nugget edge. In addition, the mitigation of residual stress by forging force decreases the driving force for crack propagation and leads to longer fatigue life. It can be concluded that applying forging force appropriately has a positive effect on the fatigue strength of resistance spot welded joints.

Residual Stress and Strain Responses of Welded Piping Joints Under Low-Cycle Fatigue Loading

2009 ◽  
Author(s):  
Pei-Yuan Cheng ◽  
Tasnim Hassan
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Stress And Strain ◽  
Weld Toe ◽  
Strain Responses

It is well known that residual stress of welded joints influence their fatigue lives. This influence of residual stress is manifested through strain ratcheting response at the weld toe. Among many other reasons, strain ratcheting at the weld toe is anticipated to be a reason of many premature fatigue failure of welded joints. Hence, accurate simulations of weld toe residual stress and strain responses are essential for fatigue life simulation of welded joints. This paper presents results form an ongoing study on fatigue failure of welded piping joints. A modeling scheme for simulating weld toe residual stress and strain response is developed. Uncoupled, thermo-mechanical, finite element analyses are employed for imitating the welding procedure, and thereby simulating the temperature history during welding and initial residual stresses. Simulated residual stresses are validated by comparing against the measured residual stresses. Finite element simulations indicate that both residual stress and resulting strain responses near the weld toe are the key factors in inducing fatigue cracks at the weld toe. Research needs in revealing the fatigue failure mechanisms at the weld toe are discussed.

scholarly journals Effect of Machined Surface Integrity on Fatigue Performance of Metal Workpiece: A Review

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Guoliang Liu ◽  
Chuanzhen Huang ◽  
Bin Zhao ◽  
Wei Wang ◽  
Shufeng Sun
Keyword(s):  
Residual Stress ◽  
Surface Topography ◽  
Surface Integrity ◽  
Work Hardening ◽  
Fatigue Cracks ◽  
Fatigue Performance ◽  
Effective Control ◽  
Published Data ◽  
Machined Surface ◽  
Machined Surface Integrity

AbstractFatigue performance is a serious concern for mechanical components subject to cyclical stresses, particularly where safety is paramount. The fatigue performance of components relies closely on their surface integrity because the fatigue cracks generally initiate from free surfaces. This paper reviewed the published data, which addressed the effects of machined surface integrity on the fatigue performance of metal workpieces. Limitations in existing studies and the future directions in anti-fatigue manufacturing field were proposed. The remarkable surface topography (e.g., low roughness and few local defects and inclusions) and large compressive residual stress are beneficial to fatigue performance. However, the indicators that describe the effects of surface topography and residual stress accurately need further study and exploration. The effect of residual stress relaxation under cycle loadings needs to be precisely modeled precisely. The effect of work hardening on fatigue performance had two aspects. Work hardening could increase the material yield strength, thereby delaying crack nucleation. However, increased brittleness could accelerate crack propagation. Thus, finding the effective control mechanism and method of work hardening is urgently needed to enhance the fatigue performance of machined components. The machining-induced metallurgical structure changes, such as white layer, grain refinement, dislocation, and martensitic transformation affect the fatigue performance of a workpiece significantly. However, the unified and exact conclusion needs to be investigated deeply. Finally, different surface integrity factors had complicated reciprocal effects on fatigue performance. As such, studying the comprehensive influence of surface integrity further and establishing the reliable prediction model of workpiece fatigue performance are meaningful for improving reliability of components and reducing test cost.

Residual Stresses around an Expanded Hole in an Aluminum Clad Sheet

2005 ◽  
Vol 490-491 ◽  
pp. 41-46 ◽  
Author(s):  
P. Matos ◽  
Pedro Miguel Guimarães Pires Moreira ◽  
J.C.P. Pina ◽  
A. Morão Dias ◽  
Paulo Manuel Salgado Tavares de Castro
Keyword(s):  
Residual Stress ◽  
Fatigue Cracks ◽  
Numerical Data ◽  
Stress Profile ◽  
Detailed Knowledge ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
Residual Stress Profile ◽  
Clad Sheet ◽  
Numerical Tools

Cold working introduces a compressive stress field around rivet holes, reducing the tendency for fatigue cracks to initiate and grow under cyclic mechanical loading. As it is well known, for the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Powerful experimental and numerical tools are nowadays available for that purpose. In the present work both types of tools, X-ray diffraction and 3D Finite Element Analysis (FEA), were used in order to evaluate the residual stress profile. A comparison of experimental and numerical data is presented and discussed.

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