INFLUENCE OF RESIDUAL STRESSES ON RANDOM FATIGUE LIFE, IN BENDING, OF NOTCHED 7075 ALUMINUM SPECIMENS

1962 ◽  
Author(s):  
R. A. Heller ◽  
M. Seki ◽  
A. M. Freudenthal
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Random Fatigue

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

Fatigue Life Improvement of Welded Elements and Structures by Ultrasonic Impact Treatment

2011 ◽  
Author(s):  
Yuriy Kudryavtsev ◽  
Jacob Kleiman
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Highway Bridges ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving ◽  
Life Improvement

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

The Effect of Several Finishing Processes on the Fatigue Resistance of Hole Surfaces

1989 ◽  
Vol 111 (1) ◽  
pp. 71-73 ◽  
Author(s):  
M. O. Lai ◽  
A. Y. C. Nee
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Radial Direction ◽  
Fatigue Loading ◽  
Steel Plates ◽  
Finishing Processes ◽  
Compressive Residual Stresses

This investigation examines the effects of different finishing processes on the fatigue life of premachined holes in Assab 760 steel plates. The finishing processes studied were reaming, ballizing, and emery polishing. A general decrease in fatigue life with increase in surface roughness is observed for all the processes employed. In comparing the different processes, for a constant surface roughness, polishing is generally found to give the longest fatigue life while ballizing, in spite of the greater compressive residual stresses induced on the surface of the finished hole, the shortest. The surprising phenomenon was found to be attributed to the amount of plastic deformation occurred before fatigue loading. For Assab 760 steel, a prestrain in the radial direction of less than about 2.5 percent appeared to reduce the fatigue resistance of the material.

scholarly journals Residual Stresses Distribution Posterior to Welding and Cutting Processes

2021 ◽  
Author(s):  
Asma Manai
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Weld Seam ◽  
Considerable Change ◽  
Cutting Process ◽  
Local Material ◽  
Weld Residual Stress ◽  
Exact Size ◽  
Cutting Processes ◽  
Welding Processes

Welding is a joining process that leads to considerable change in the local material and the formation of welding residual stresses (RS). Welding residual stresses can be compressive (beneficial for the fatigue life) or tensile (harmful for the fatigue life). In this chapter, a probabilistic analysis of residual stresses distribution posterior to welding processes is carried out. Several researchers stated that the type of the introduced stresses either compressive or tensile depends on several factors. Some of these factors are listed in this chapter. Welding of mega-structures is carried out in the workshops, then a cutting process takes place to construct the exact size of the structural components. This cutting process has a significant effect on the weld residual stresses re-distribution. A study of the re-distribution of the weld residual stress after cutting was performed. It was found that independent of the weld seam length, the residual stresses re-distributed up to 60 % of the weld seam length.

Sign in / Sign up

Export Citation Format

Share Document