Effect Of Residual Stress Research Articles

Analysis of the effect of deep-profile compressive residual stress induced by laser peening on fatigue strength of 7075 aluminum alloy

The effect of laser peening-induced compressive residual stress on the fatigue strength improvement of A7075 specimens was investigated. Rotary bending fatigue tests and residual stress distribution measurements using the sequential polishing method were conducted on untreated, shot-peened, and laser-peened specimens. The results revealed that laser peening provides a deeper compressive stress and a deeper fracture origin, resulting in higher fatigue strength. Furthermore, controlling the laser parameters could extend the depth of the compressive stress layer by approximately 5 mm, indicating the possibility of applying laser peening to thicker materials to improve the fatigue strength.

Study on predicting rolling contact fatigue of pitch bearing raceway in offshore wind turbine

Pitch bearing is the critical component that are widely used to ensure the operation of offshore wind turbine blades and enable efficient capture of wind energy. Uncertain environmental factors and extreme load conditions can induce early fatigue failure in pitch bearings, and lead to major accidents such as blade detachment. In this study, a damage coupling fatigue simulation model, considering residual stress (RS) and surface hardness effect, was constructed following the continuum damage mechanics (CDM) to investigate the rolling contact fatigue (RCF) of pitch bearing under ultimate loading conditions. Different ultimate loading conditions were calculated on an integrated load simulation platform established using Python script. The damage-coupled elastoplastic constitutive equation and damage-controlling equations considering RS and surface hardness were derived and programmed in the material user subroutine UMAT. The effects of ultimate loading conditions, RS, and surface hardness on RCF were studied. Results show that increasing the surface hardness or increasing the compressive RS enhances the anti-fatigue performance of pitch bearing.

Experimental characterization of residual deformations in human descending thoracic aortas

The effect of residual stresses on the deformation of human aortas under pulsatile pressure is relevant. Experimental measurements of residual deformations are necessary to characterize residual stresses in human aortas. For this reason, an experimental study is carried out. In the present study, longitudinal and circumferential strips from descending thoracic aortas obtained from 21 donors, harvested during organ donation explant, underwent residual deformation measurements. The intact wall and the three separated layers were tested in both directions, resulting in 8 tests per donor, which gives a relevant set of experimental data for further studies. Results show significant residual deformations both in circumferential and longitudinal directions, which are compatible with a significantly compressed intima in the unloaded aorta. In particular, the measured mean effective curvature was −0.193 ± 0.064 (1/mm) for the circumferential strips and −0.076 ± 0.030 (1/mm) for longitudinal strips of the full wall. The effects of age and gender were also investigated.

Effect of dented residual stress on the surface-defect-induced pitting under rolling contact loading of M50 bearing steel

Surface-defect-induced pitting gradually becomes the limitation of the rolling contact fatigue life of the M50 bearing steel as the subsurface initiation spalling probability decreases recently. Dent formation lives residual stress (RS). However, it was ignored in past studies on surface-initiated pitting. Therefore, this study established a continuous simulation model from particle compression to cycle rolling contact loading to study the dent-induced RS effects on damage evolution. The constitutive model of damage evolution incorporated continuum damage mechanics and cohesive mechanics. The results show that the depth-width ratio of the dent and RS increases as the load and hardness increase. RS makes both subsurface-initiation-damage and surface-initiation-damage advance, and affects the direction and speed of the surface damage evolution. Moreover, the size of the pitting in the rolling direction increases as hardness increases.

Residual Stress Prediction during TIG and MIG Welding Process of Steel - A Review

In this study, a forensic review of residual stress predictions and its impact on welded joints especially the steel pipes during the Tungsten inert gas welding and metal inert gas welding processes were reviewed. It was established that in the case of MIG welding, the effect of residual stress can be reduced after treatment. In the case of TIG welding process, increase in current will lead to deformation and residual stresses. Estimating the residual stress is a challenging task. It is common to predict residual stress using a notch stress intensity factor, a numerical simulation approach coupled with a thermal-mechanical finite element model. Thus, adequate design in welding parameters will help in the optimization of the process to achieve a safe and reliable welded joint during TIG and MIG welding process.

Biodegradation performance of ball burnished magnesium alloy in stimulated body fluids for bioresorbable implant applications

Magnesium alloys are found to be potential bioresorbable materials. However, the application range of these alloys as bioresorbable materials has been limited due to rapid degradation in physiological fluids. The current study deals with the enhancement of degradation behavior of Mg Ze41A alloy in SBF solution by ball burnishing. Further, the influence of burnishing parameters on biodegradation rate has been investigated by Tafel plots, polarization resistance, electrochemical impedance spectroscopy and surface morphology analysis of degraded samples. Additionally, the biodegradation rate has been estimated by ANFIS modeling. The biodegradation rate of Mg Ze41A has been reduced from 1.106 mm/yr to 0.367 mm/yr with an improvement of 68.82% at optimum burnishing condition of burnishing force 50 N, burnishing speed 1400 RPM, burnishing feed 125 mm/min and 2 passes. ANOVA analysis has revealed that burnishing force and feed have contributed the most for the enhancement. The shift in degradation potential towards noble direction and reduction in degradation current density in potentiodynamic polarization curves and the highest charge transfer resistance in electrochemical impedance spectroscopy of the burnished samples are observed for burnished samples. The results reveal that ball burnishing process is a potential surface modification method in reducing the biodegradation rate of Mg Ze41A alloy. The ball burnishing has resulted in lowest biodegradation rate at a degradation current density of 5.743 μA/cm2 and degradation potential of −1.513 V. The ANFIS model developed with 81 fuzzy rules and triangular membership function estimated the biodegradation rate with an accuracy of 95.03%. The decrease in biodegradation rate of ball burnished magnesium substrate in SBF is essentially due to cumulative effect of compressive residual stress, microhardness, surface finish, work hardening and grain refinement.

Effect of titanium interlayer configurations on residual stresses and performance of titanium/titanium nitride multilayer coatings

Multilayer coatings provide an effective measure to control and optimise of residual stresses, enhance coating adhesion, fracture toughness, wear and corrosion resistance of coating system. In this study, we designed and produced bi-layer and four-layer titanium/titanium nitride magnetron sputtered coating configurations by altering the position of the interlayer. The in-plane residual stresses in different coating configurations are measured by multiple peak grazing incidence X-ray diffraction techniques. Subsequently, the effect of different compressive residual stresses on adhesion, mechanical properties, wear and corrosion resistance of coatings are investigated. Results show that the position of interlayer in multilayer coating configuration has a great impact on relaxation of residual stresses. The residual stresses are relieved by 26% and 46% by lowering the position of titanium interlayer from 800 nm at the top to 1000 nm and 1200 nm, respectively. The nanoindentation hardness is decreased by 11% and 13%, respectively. The wear rate of multilayer coating having interlayer position at 800 and 1000 nm from the top is ≈ 23% lower compared to bilayer however it is increased by ≈ 50% when interlayer coatings position changed to 1200 nm from the top. The interposition of interlayer in multilayer coating configurations decreased the corrosion current density by ≈ 50%. All multilayer coatings including higher residual stresses show better adhesion to the substrate compared to bilayer coatings which shows severe delamination.

Numerical Analysis of Residual Stresses Effect in Multi-materials

Background: In this study, the effect of mechanical and physical properties of the metal and temperature is highlighted. The purpose of this study is to analyze the effect of these stresses on multi-materials. This work aimed to conduct a three-dimensional numerical study by the finite element method on the levels and distributions of the stresses in the Al2O3/NI/HAYNES multi-materials. These stresses of thermal and mechanical origin are generally detrimental to the service life of multi-material. Methods: The use of numerical resolution by finite element method is the most suitable for complex mechanical problems. It allows a more in-depth analysis of all points of the structure. In this study, a fundamental tool was constructed to resolve the mechanical behavior of materials subjected to complex solicitations. Therefore, the ABAQUS calculation code version 6.14 was used to analyze the residual stresses. Results: By interpreting the results in terms of stress variation, we identified the areas at risk; in particular, the nature of a joint effect plays a decisive role in the assembly of the right material in its mechanical resistance. This nature is defined in terms of stiffness (Young's modulus) and differential expansion (coefficient of thermal expansion). Conclusion: The presence of strong residual stresses can constitute a risk of damage to several materials. The difference between the coefficients of thermal expansion of the two materials (metal and ceramic) linked together induces, in these two constituents, normal internal stresses. This difference determines the level and distribution of these constraints. Moreover, the sign of this difference determines the state of the normal stresses.

Subtractive processing and surface integrity of additive manufacturing materials

PurposeAs an advanced manufacturing method, additive manufacturing (AM) technology provides new possibilities for efficient production and design of parts. However, with the continuous expansion of the application of AM materials, subtractive processing has become one of the necessary steps to improve the accuracy and performance of parts. In this paper, the processing process of AM materials is discussed in depth, and the surface integrity problem caused by it is discussed.Design/methodology/approachFirstly, we listed and analyzed the characterization parameters of metal surface integrity and its influence on the performance of parts and then introduced the application of integrated processing of metal adding and subtracting materials and the influence of different processing forms on the surface integrity of parts. The surface of the trial-cut material is detected and analyzed, and the surface of the integrated processing of adding and subtracting materials is compared with that of the pure processing of reducing materials, so that the corresponding conclusions are obtained.FindingsIn this process, we also found some surface integrity problems, such as knife marks, residual stress and thermal effects. These problems may have a potential negative impact on the performance of the final parts. In processing, we can try to use other integrated processing technologies of adding and subtracting materials, try to combine various integrated processing technologies of adding and subtracting materials, or consider exploring more efficient AM technology to improve processing efficiency. We can also consider adopting production process optimization measures to reduce the processing cost of adding and subtracting materials.Originality/valueWith the gradual improvement of the requirements for the surface quality of parts in the production process and the in-depth implementation of sustainable manufacturing, the demand for integrated processing of metal addition and subtraction materials is likely to continue to grow in the future. By deeply understanding and studying the problems of material reduction and surface integrity of AM materials, we can better meet the challenges in the manufacturing process and improve the quality and performance of parts. This research is very important for promoting the development of manufacturing technology and achieving success in practical application.

Effect of Residual Stress on Hydrogen Embrittlement at Sheared Edge

Effect of Residual Stress on Hydrogen Embrittlement at Sheared Edge

Simulations of the effect of shot peening backstress on nanoindentation

Shot peening is a mechanical surface treatment that can introduce compressive residual stress and work hardening simultaneously. This work hardening, considered as a modification of the elastic region with plastic strain, can be modeled with two types of contributions: isotropic hardening and kinematic hardening. In order to characterize the mechanical properties of the treated surface using the instrumented indentation technique, the effect of the backstress associated with kinematic hardening should be studied, especially for works related to fatigue loading. In this paper, the distribution of three backstress components is obtained by shot peening simulations on a nickel-based alloy, Inconel 718, commonly used in the aerospace industry, and a series of indentation simulations are carried out using a spherical tip with different equivalent backstress levels. For Inconel 718, the third backstress component, which has the slowest evolution rate, is found to have the most significant influence on the response. However, compared to the effect of residual stress and cumulated plastic strain, the effect of backstress can be neglected.

Effect of surface coating on fatigue life and fatigue crack growth behavior of AISI D2 tool steel

To study the effect of the specimen surface coating on the fatigue life and fatigue crack growth behavior, rotating bending fatigue tests were performed with a specimen coated with a TiCN thin film on AISI D2 tool steel (JIS SKD11) and a bare specimen without coating. Fatigue cracks developed inside the specimen because compressive residual stress was present on the surface of the coated and bare materials. The fatigue crack growth behavior of the internal cracks was investigated with the two-stage double-stress experimental method proposed by the authors. The fatigue life estimated from the fatigue crack growth (FCG) behavior of the internal cracks and the experimental results agreed. Furthermore, a method was proposed that can easily evaluate the effect of residual stress on fatigue life and FCG behavior. The evaluation and experimental results are in good agreement. In addition, the effects of atmospheric and vacuum conditions on FCG behavior are discussed.

Incompatible Deformations in Hyperelastic Plates

The design of thin-walled structures is commonly based on the solutions of linear boundary-value problems, formulated within well-developed theories for elastic plates and shells. However, in modern appliances, especially in MEMS design, it is necessary to take into account non-linear mechanical effects that become decisive for flexible elements. Among the substantial non-linear effects that significantly change the deformation properties of thin plates are the effects of residual stresses caused by the incompatibility of deformations, which inevitably arise during the manufacture of ultrathin elements. The development of new methods of mathematical modeling of residual stresses and incompatible finite deformations in plates is the subject of this paper. To this end, the local unloading hypothesis is used. This makes it possible to define smooth fields of local deformations (inverse implant field) for the mathematical formalization of incompatibility. The main outcomes are field equations, natural boundary conditions and conservation laws, derived from the least action principle and variational symmetries taking account of the implant field. The derivations are carried out in the framework of elasticity theory for simple materials and, in addition, within Cosserat’s theory of a two-dimensional continuum. As illustrative examples, the distributions of incompatible deformations in a circular plate are considered.

Residual stress effects on short crack propagation behavior in friction stir welded 7075-T6 aluminum alloy panel under biaxial loading: An experimental and numerical study

The effects of residual stress on short crack propagation behavior of friction stir welded (FSWed) 7075-T6 aluminum alloy panel was investigated under biaxial loading. The biaxial fatigue tests were carried out on three kinds of cruciform samples, including base material (BM) cruciform sample and FSWed cruciform sample with crack perpendicular or parallel to the weld. Scanning electron microscope (SEM) fractography was conducted to identify and relate fracture surface features to governing fatigue damage mechanisms. Finite element method combined with stress intensity factor (SIF) analysis was used to simulate the biaxial fatigue propagation. In a comparison of the crack path in BM and FSWed cruciform samples, experimental and numerical results showed that residual stress can change the nominal biaxiality ratio, leading to crack path changes in FSWed cruciform sample with crack parallel to the weld, and the curved fatigue crack front formed on the fracture surface due to the non-uniform distribution of the residual stress through the thickness. The fatigue damage mechanisms are different depending upon the biaxiality ratio as well as the weld direction.

Low cycle fatigue behavior of Incoloy 800H weld joint at 800 °C

The fatigue behavior of the 800H weld joint at the temperature of 800 °C was investigated, taking into account the effects of residual stress and microstructure. To model the residual stress in the welded joint, a finite element method was employed and its accuracy was verified using a hole drilling method, which was also used to study the evolution of residual stress during cutting and heating processes. Additionally, the weld region was characterized by measuring the distributions of elements and micro-hardness via energy dispersive X-ray spectroscopy and Vickers hardness tester. Fatigue lives, curves of displacement versus the number of cycles were obtained, and the fracture morphology was analyzed. The results reveal that the calculated residual stress in the weld region agrees well with the experimental results, and the transverse residual stress reduces in magnitude due to cutting and heating. Element distribution and micro-hardness exhibit obvious variations from the base metal to the weld metal. The micro-hardness has a minor effect on residual stress but a significant impact on local stress amplitudes at the weld toe. Furthermore, fatigue fractures primarily occur at the weld toe when the maximum cyclic stress exceeds 200 MPa, while the fracture location varies within the middle weld metal under smaller loads.

Multiphysics Study of Thermal Profiles and Residual Stress in Welding.

One of the effects of welding is residual stress. Welding involves complex tests concerning differences in values of the mechanical parameters of its regions as an effect of residual stress. Such multiphysics characteristics of welding pose a challenge in predicting residual stress. In the present study, a thermo-mechanical constitutive model considering phase transformation and transformation plasticity is implemented in the numerical model in ABAQUS user subroutines. In order to consider phase evolution in welding, the metallurgical parameters for Leblond's phase equation were obtained from the calibration of DH36 steel with a CCT diagram. In addition, the effects of welding speed on thermal profiles and residual stress generation were investigated. Analysis has suggested that the width of the heat-affected zone (HAZ) decreases with an increase in welding speed, and the phase fraction is significantly affected by this kind of parameter. Such phase transformation has led to the generation of a compressive stress in the fusion zone (FZ) and HAZ. The volume difference between coexisting phases produces a compressive stress in cooling, and its magnitude was increased with martensite increasing.

Theoretical prediction of proteins network-induced nonlocal response in molecules-resonator biosensor with hydrogen bonds including van der waals interactions

The present study investigates the adsorption-induced resonance frequency shift of a biomolecule-resonator system, considering the shear distortion effect, distributed adatoms, and small-scale effects using nonlocal elasticity theory. The adsorption-induced energy is modeled using a distributional approach for both the bio-receptor and spike protein. The dynamic behavior model for a microbeam resonator is derived, incorporating surface stress. The functional microbeam approach and the localized biomolecule approach are employed, along with van der Waals (vdW) interactions using the Lennard-Jones (6–12) potential to calculate the influence of all applied conditions. Explicit inertia moment and shear force are determined based on the nonlocal Timoshenko beam equations, with residual stress applied as an additive axial load. Numerical results demonstrate that the computed frequency shift depends on the active surface parameters, adsorbed adatoms, as well as the localized receptor and spike. The evaluation of results indicates that interatomic phenomena make the microsystem softer, emphasizing the importance of considering it in computations. Thus, the derived model is suitable for investigating the dynamic behavior of the biomolecule-resonator, applicable for determining both mass and density of spike and virus in the presence of adatom bonds.

Effect of residual stress on pore formation in multi-materials deposited via directed energy deposition

A multi-layered deposit consisting of a surface layer, buffer layer, and substrate was created using directed energy deposition. The study aimed to determine how residual stress influences pore formation in the surface layer. The size of the pores in the surface layer varied based on the defects present in the buffer layer. When the buffer layer had cracks, the surface layer did not exhibit any large pores. Conversely, in the deposits where the buffer layer was free of cracks, the surface layer had numerous larger pores. Factors such as elevated carbon content and residual stress led to both hot and cold cracks in the buffer layer. The residual stress that wasn't alleviated by cracks in the buffer layer propagated to the surface layer across the buffer/surface layer boundaries. This resulted in an increase in tensile residual stress in the surface layer, amplifying the equilibrium pressure inside gas pores and prompting the expansion of these pores as a means of stress relief.

Effect of Al2O3 on Microstructure and Corrosion Characteristics of Al/Al2O3 Composite Coatings Prepared by Cold Spraying

Cold spraying was used to prepare Al/Al2O3 composite coatings. The Al2O3 content was controlled to increase the mechanical property and corrosion resistance of the composite coating. The inclusion of Al2O3 particles results in considerable plastic deformation of Al particles and grain size refinement in the coating. Additionally, the coating’s surface roughness decreased from 24.63 μm to 9.02 μm, and the porosity decreased from 6.34% to 2.07%. The increase in microhardness of the composite coatings was attributed to the combined effect of residual compressive stress, second phase strengthening of Al2O3, and plastic hardening of Al particles. The electrochemical test results indicate that the mass fractions of Al2O3 significantly affected the corrosion resistance of the Al/Al2O3 composite coating. Compared to the Al coating, the composite coating exhibited improved corrosion resistance, with a reduction in corrosion current density from 1.09 × 10−3 A/cm2 to 2.67 × 10−6 A/cm2 and an increase in corrosion potential from −1.57 V to −1.14 V. However, when the alumina particle content exceeded 17.7%, it led to more Al2O3 particle breakage, increasing the weak bonding interfaces in the composite coating, and consequently reducing its corrosion resistance.

A fractographic study of fatigue crack growth from a cold expanded fastener hole at an engineering “crack initiation” scale

AbstractThe effects of cold expansion on fatigue crack growth from fastener holes in aircraft structure are a well‐studied problem, with many contributions focusing on both residual stresses and “long crack” experimental data. In this study, the authors have used quantitative fractography techniques to measure fatigue crack growth from naturally occurring discontinuities on an engineering “crack initiation” scale. Fatigue crack growth rates were measured through the full range of crack depths, allowing the effects of beneficial residual stresses to be directly observed. The almost identical early crack growth rates in cold expanded and non‐cold expanded specimens were demonstrated up to crack depths of approximately 0.1–0.2 mm. Beyond this depth, fatigue crack growth in cold expanded specimens was markedly slowed to the point at which failure ultimately arose from cracks away from, or growing into, the fastener hole. The available life improvement factor for cold expansion is therefore maximized through a crack growth‐based lifing approach.