Fracture toughness and evaluation of coating strength with an initial residual stress field

1994 ◽  
Vol 26 (1) ◽  
pp. 40-48 ◽  
Author(s):  
A. V. Byakova ◽  
V. G. Gorbach
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Stress Field ◽  
Residual Stress Field ◽  
Initial Residual Stress

Residual Stress Regenerated on Low Plasticity Burnished Inconel 718 Surface After Initial Turning Process

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yang Hua ◽  
Zhanqiang Liu ◽  
Bing Wang ◽  
Jiaming Jiang
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Analytical Model ◽  
Inconel 718 ◽  
Plastic Behavior ◽  
Residual Stress Field ◽  
Workpiece Material ◽  
Elastic Plastic ◽  
Initial Residual Stress ◽  
Low Plasticity Burnishing

Abstract Low plasticity burnishing (LPB) has been extensively employed in aero-industry to enhance fatigue performance of machined components by introducing compressive residual stress. Effects of various parameters on the residual stress field induced by low plasticity burnishing have been investigated by many researchers. However, initial residual stresses induced by machining are one of the important factors which affect the residual stress regenerated by the LPB process. The present work aims to develop an analytical model which takes into account the initial residual stress and burnishing parameters to predict residual stress field of workpiece material Inconel 718 based on Hertz contact theory and elastic–plastic theory. Initial residual stress fields were produced by turning of Inconel 718 and were measured by using X-ray diffraction technique. Two types of material constitutive models such as the linear hardening model and isotropic–kinematic model were employed to describe the elastic–plastic behavior of workpiece material Inconel 718. An analytical study was performed to analyze the effect of the initial residual stress field and burnishing parameters on residual stress induced by low plastic burnishing. The results of analytical model were verified by conducting the LPB experiments on initial turned Inconel 718. The results showed that the shape and magnitude of the residual stress field obtained with considering the effect of initial residual stress field was in good accordance with experimental measurements.

Modelling Fatigue Crack Growth in a Residual Stress Field

2006 ◽  
Author(s):  
A. J. Price ◽  
P. Tsakiropoulos ◽  
M. R. Wenman ◽  
P. R. Chard-Tuckey
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Distribution ◽  
Stress Field ◽  
Crack Growth ◽  
Nuclear Reactor ◽  
Element Model ◽  
Residual Stress Distribution ◽  
Residual Stress Field

Tensile residual stresses can have a detrimental affect on the safe operating limits of components. In most cases, these residual stress fields can be relieved through various treatments but in many cases it is not realistic to expect the complete elimination of these stresses. When considering the Reactor Pressure Vessel (RPV) located within a Nuclear Reactor Plant (NRP), knowledge of fatigue and fracture within a residual stress field is essential in support of safety cases. This research has investigated the behaviour of flaws that lie within a residual stress field with emphasis on fracture toughness through a series of fracture toughness tests. Alongside this experimental series, a finite element model has been created to predict the stress distributions prior to fracture. To enable an accurate simulation of the residual stress field distribution before loading to fracture it is important that the introduction of a fatigue crack is accurately modelled. This paper details several methods of introducing a fatigue crack into a simulation. During this research it has been shown that the introduction of a crack in progressive stages will lead to a better representation of the residual stress distribution prior to fracture. It has been shown that it is essential to use experimentally determined crack front shapes for the final stage of crack growth as this shape can significantly alter the residual stress distribution.

Finite Element Simulation and Analysis of Initial Residual Stress Field for Titanium Alloy Monolithic Component Blank

2012 ◽  
Vol 629 ◽  
pp. 203-208
Author(s):  
Yong Yang ◽  
Bing Liu ◽  
Yu Ling Wang
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Titanium Alloy ◽  
Stress Field ◽  
Residual Stress Field ◽  
Initial Residual Stress ◽  
Center Region ◽  
Mechanical Procedure ◽  
Control Equation ◽  
Monolithic Component

In this paper, the initial residual stress field for titanium alloy monolithic component blank is simulated and analyzed by applying a sequentially coupled thermal and mechanical procedure based on finite element method. The control equation of heat conduction of annealing process is studied, and the boundary condition and fundamental equations of simulation are given. The research results show that the initial residual stress field for titanium alloy monolithic component blank radiates from the center region to outside, the center region being the maximum value, then decreases gradually, until a minimum value is attained at the corner.

Provisional Results for an Experimental Investigation Into the Effect of Combined Primary and Secondary Stresses When Considering the Approaches of R6 and the Recently Developed g() Method

2011 ◽  
Author(s):  
Peter James ◽  
Paul Hutchinson ◽  
Colin Madew
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Experimental Investigation ◽  
Stress Field ◽  
Driving Force ◽  
Residual Stress Field ◽  
Crack Driving Force ◽  
Material Characterisation ◽  
Point Bend ◽  
Initial Results

Engineering components, particularly those containing weldments, may contain small crack-like defects that experience combinations of primary and secondary stresses during service. A new function, g(), has been introduced previously to quantify the influence of plasticity interaction under combined primary and secondary loading on a components crack driving force. This paper compares g() with experiments performed to consider g() over a range of plasticity values. This experimental programme was performed on scalloped notch three point bend specimens that had experienced a pre-compression to induce a residual stress field before being tested to failure over a range of temperatures (−150, −90 and −50 °C). Samples which did not undergo a pre-compression were also tested to provide an estimate of the materials fracture toughness at the temperature in question. Through analysing the experimental results it is clear that further material characterisation is required. This paper, therefore, only presents the initial results at this stage. However, as a pessimistic interpretation of the results has been made, and since both the existing R6 and the g() plasticity interaction parameters are acceptable, the experiments provide useful validation to both methods.

Numerical and experimental investigations of effects of residual stresses on crack behavior in Aluminum 6082-T6

2012 ◽  
Vol 226 (9) ◽  
pp. 2178-2191 ◽  
Author(s):  
Mohammadreza Farahani ◽  
Iradj Sattari-Far ◽  
Davood Akbari ◽  
Rene Alderliesten
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Growth ◽  
Crack Tip ◽  
Residual Stress Field ◽  
Integrity Assessment ◽  
Crack Tip Constraint

In the structural integrity assessment, residual stresses play an important role. The residual stresses affect both the crack driving forces and the crack-tip constraint. To investigate the interaction of residual stresses with mechanical loading during the onset of crack growth in Aluminum 6082-T6, modified single edge-notched bending specimens were used. Aluminum 6082 has the highest strength of the 6000 series alloys with excellent corrosion resistance. A residual stress field was created in the specimens by pre-loading. To accurately quantify the residual stress field created during this test procedure, the strains were measured during loading and unloading and compared with finite element results. After the introduction of the residual stress field, the specimens were tested under three-point bending to determine the load versus displacement behavior and fracture toughness. Also, a post-processor for finite element calculation was developed to enable determination of the J-integral values for the specimens having residual stresses. The constraint parameters Q and R were calculated at the crack-tip to describe the stress field in this region. The parameter Q is used to characterize the loading and geometry constraint, and the parameter R is used for characterizing the crack-tip constraint due to residual stresses. It is observed that tensile residual stresses around the crack-tip increase the crack-tip constraint and decrease the fracture toughness of the bodies. By increasing the external load, the constraint parameter R goes toward zero and the effects of residual stresses on the crack growth resistance become negligible.

scholarly journals Residual stresses in thermite welded rails: significance of additional forging

2020 ◽  
Vol 64 (7) ◽  
pp. 1195-1212
Author(s):  
B. Lennart Josefson ◽  
R. Bisschop ◽  
M. Messaadi ◽  
J. Hantusch
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Metal ◽  
Welding Process ◽  
Surface Zone ◽  
Fe Model ◽  
Uneven Surface ◽  
Residual Stress Field ◽  
High Dynamic

Abstract The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

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