Compressive Residual Stress Research Articles

Comparative analysis of geometric imperfections and residual stresses on the global stability behavior of cantilever composite alveolar beams

Few studies addressed the influence of geometric and structural imperfections of steel alveolar I-sections on the stability behavior of composite beams under hogging moment. Therefore, this paper aims to study the sensitivity to geometric imperfection amplitude and residual stress distribution on their global stability. The research primarily focuses on comparing numerical results with experimental data in detail, which addresses four tests involving cantilever composite beams with castellated and cellular I-sections. It includes applying various residual stress patterns and geometric imperfection values to advanced numerical analyses as documented in the literature. Linear buckling analyses (LBA) and geometrically and materially nonlinear analyses with imperfections (GMNIA) are carried out using the ABAQUS software. Regarding the first positive eigenvalue from LBA analyses, the eigenvectors presented Web-Post Buckling (WPB) with a slight compressed flange lateral curvature, inserted as the initial geometric imperfection in the GMNIA analyses. However, when the residual stresses were implemented in the GMNIA analyses, some finite element models had different failure modes regarding the deformed configurations from LBA analyses, in which the failure modes were characterized by Lateral-Distortional Buckling (LDB), which was in agreement with the test results. As the beams reached LDB in an inelastic regime, residual stresses significantly affected their resistant capacity. This way, the distribution of compressive residual stresses in the flanges had the most critical influence on the global stability behavior of the analyzed beams, as these residual stresses favor the LDB occurrence. Finally, higher geometric imperfection amplitudes did not provide only lower ultimate loads, as when the instability phenomena are reached in an inelastic regime, the effect of global geometric imperfections becomes highly complex.

A gradient strengthening method of wire-arc additive manufacturing coupling with surface rolling and its application

The gradient distribution of properties, which satisfies the service requirements of critical components operating in extreme environments, plays a significant role in enhancing the durability of these components. Here, a new method of wire-arc additive manufacturing (WAAM) coupling with surface rolling was proposed to construct the gradient distributed properties. The present study focuses on a typical application of this method, wherein the surface of an exhaust valve in a marine diesel engine is processed to achieve a gradient property. The gradient strengthening mechanisms were investigated through numerical simulation and physical experiments. Simulation results demonstrated that the residual tensile stress resulting from WAAM was significantly reduced and mostly converted to compressive stress after surface rolling. The initial maximum residual tensile stress of 208.6 MPa, located at the surface of the deposited valve, was reduced to −167.8 MPa after surface rolling. The depth of residual compressive stress was extended 6–7 mm from the rolled surface to the deposited zone. Analysis of microstructures revealed that three distinct zones with different microstructural characteristics were generated through the proposed method, thereby forming the gradient microstructures. Specifically, the surface rolled zone was characterized as nanocrystallines (<1 μm), refined grains (1–10 μm), and deformed grains (>10 μm), while the deposited zone and substrate corresponded to columnar grains and equiaxed grains, respectively. A wide gradient strengthening layer with an approximate thickness of 8 mm was achieved on the processed valve surface, exhibiting a hardness gradient from 314 MPa at the substrate to 566 MPa on the rolled surface. The gradient strengthening mechanisms were attributed to intrinsic material strengthening, grain boundary strengthening and dislocation strengthening.

Tensile direction dependent failure of laser pretextured TiN coating/stainless steel substrate

Laser pretexturing is widely used as an efficient way of modification to enhance the interfacial properties between coating-substrate pairs. The effect of the relative orientation between the laser texture and the loading direction on the mechanical properties of coating and interface is not yet known. To this end, the present work aims at investigating the effect of tensile direction on the failure of laser pretextured TiN coating/stainless steel substrate. Transverse and longitudinal textures were separately etched on the 304 stainless steel substrate using pulsed laser technology, followed by depositing TiN coating via magnetron sputtering technique. X-ray diffraction (XRD) and nanoindentation tests were conducted to measure the residual stress, elastic modulus and hardness of both substrate and coating. The stages of coating failure were examined through in-situ tensile experiments and comparative assessment was made on the properties such as interfacial shear strength (ISS) and critical energy release rate (CERR). Results showed that the CERR and ISS decreased by 21 % and 8 % respectively for the transversely pretextured (TP) specimen. In contrast, the ISS was increased by 36 % for the longitudinally pretextured (LP) specimen, for which the compressive residual stress on the surface of the substrate was transformed into tensile stress by laser pretexturing, and the texture morphology acted as a stress reliefer, alleviating the buckling and shear damage of coating. These findings are expected to offer insights into understanding the failure mechanism of laser pretextured TiN coating/304 stainless steel substrate and to provide a helpful reference for the effecient design of relevant laser textures.

Multiscale simulation combined with experimental investigation on residual stress and microstructure of TC6 titanium alloy treated by laser shock peening

The evolution behavior of residual stress and microstructure of TC6 titanium alloy under laser shock peening (LSP) were investigated using finite element (FE) and molecular dynamics (MD) simulations combined with experiments. The propagation process of laser-induced stress wave and plastic deformation behavior of TC6 titanium alloy model were studied using FE software with ABAQUS. The FE simulation results showed that increasing laser energy and impact time could increase the amplitude of compressive residual stress (CRS) to a certain extent, while a higher overlapping rate improved the CRS uniformity. The experimental results of residual stress testing based on XRD technology were consistent with the FE simulation results. Based on the piston shock method, the microstructural evolution process of α phase of titanium alloy under different shock velocities was simulated using MD software with LAMMPS. Laser shock wave promoted the transformation of hexagonal close-packed (HCP) structure to body-centered cubic (BCC) and face-centered cubic (FCC) structures in titanium alloy, and the generated dislocation density increased with increasing shock velocity. The severe plastic deformation caused by laser shock wave induced the formation of mechanical twin, subgrain and stacking fault, which was consistent with the (transmission electron microscope) TEM characterization results.

In situ HEXRD experimental study and prediction of microstructures and internal stresses during heat treatment of carburized and carbonitrided low-alloyed steels

Thermochemical surface treatments of steels, such as carburizing and carbonitriding are used to improve mechanical properties, especially resistance to fatigue. Carbonitriding can achieve excellent properties, but the origins remain to be understood, as it has been less studied than carburizing. Fundamental understanding has to be established regarding the formation of microstructures and internal stresses as well as their couplings, during the cooling which follows the enrichment treatment.For this purpose, an original experimental method is introduced to follow in situ by High-Energy X-Ray Diffraction the phase transformation kinetics as well as the evolutions of the internal stresses during cooling, inside laboratory scale, 3 mm-thick samples with C and/or N composition gradients. The usual trends are confirmed regarding carburizing: the carbon-enriched case is the last to transform and the surface ends up with compression residual stresses. Conversely, for carbonitriding, unusual evolutions of microstructure and internal stresses are observed. The presence of nitrogen reduces the hardenability in the enriched case. This modifies the chronology of the phase transformations and this leads to tensile residual stresses at the surface.A coupled thermal, mechanical and metallurgical model predicting the phase transformation kinetics and the evolutions of internal stresses is set up. It achieves quantitative predictions and it shows that, in the studied cases, the phase transformation plasticity strains are the main origin of the residual stresses.

Effect of Ultrasonic Shot Peening on Microstructure and Corrosion Properties of GTA-Welded 304L Stainless Steel

Austenitic stainless steels used in structural applications suffer from stress corrosion cracking due to residual stresses during welding. Much research is being conducted to prevent the stress corrosion cracking of austenitic steels by inducing compressive residual stresses. One method is ultrasonic shot peening (USP), which is used to apply compressive stress by modifying the mechanical properties of the material’s surface. In this study, 304L stainless steel was butt-welded by gas tungsten arc welding (GTAW) and subsequently subjected to compressive residual stress to a depth of 1 mm from the surface by a USP treatment. The influence of USP on microstructural changes in the base metal, the HAZ and weldment, and the corrosion properties was analyzed. A microstructural analysis was conducted using SEM-EDS, XRD, and EBSD methods alongside residual stress measurements. The surface and cross-sectional corrosion behavior was evaluated and analyzed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurements, a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and an ASTM A262 Pr. C test. The surface was deformed and roughened by the USP. The deformed areas formed crevices, and the inside of the crevices contained some cracks. The crevices and internal cracks caused pitting, which reduced the resistance of the passivation film. The cross-section was subjected to compressive residual stress to a depth of 1 mm from the surface, and the outermost area of the cross-section had fine grain refinement, forming a solid passivation film that improved the corrosion resistance.

Transient Nucleate Boiling and Its Use for Thermomechanical Technologies Development

In the paper high temperature and low temperature intensive thermomechanical treatment is discussed. It is based on recently discovered new three physical principles that belong to the transient nucleate boiling process taking place in cold fluids. Such processes are considered in conditions when any film boiling during quenching in cold fluids is completely absent. That makes nucleate boiling very intensive, i.e. . The discoveries are used for direct quenching articles after forgings. The first is intensive high-temperature thermo-mechanical treatment (HTTMT). It is used for low and middle-carbon alloy steels. Forged steel parts are intensively quenched with a cooling interruption at the proper time to form surface compression residual stresses and fine bainitic microstructure at the core that increases radically surface life of forgings. The second method includes high-temperature and low temperature intensive thermo - mechanical treatment (LTTMT) of high carbon alloy steels with delaying martensitic transformation to make low-temperature thermo - mechanical treatment (LTTMT) possible. Then, after high temperature and low-temperature thermomechanical treatment, the steel goes to immediate tempering to create highly strengthened fine bainitic microstructure throughout the section of the steel part. A modified method of cooling time calculation, suitable for any size and form of steel part, is widely discussed in this paper.

Prediction of residual stress depth profiles in case-carburized gears

Residual stresses have a significant influence on the load carrying capacity of gears. High near-surface compressive residual stresses can increase pitting strength and tooth root bending strength up to 50%. Tooth flank fracture (TFF) is a gear fatigue failure mode, which is in contrast to pitting or tooth root breakage not initiated at the surface or close to the surface but in larger material depths beneath the active gear flank. Therefore, the residual stresses in larger material depths are decisive for TFF. In these larger material depths, the residual stress conditions are almost unknown up to now. It is assumed that tensile residual stresses are present in these areas, which can negatively influence the TFF load carrying capacity. So far, no validated methods are known to estimate or predict these tensile residual stresses. As a result, the tensile residual stresses could not be considered in the calculation methods for the risk of TFF at all until recently.This paper presents a method to predict the residual stresses in case-carburized gears based on comprehensive numerical simulations of case-carburizing processes of different-sized gears. The calculated residual stress profiles also consider the tensile residual stresses in larger material depths.

Influence of double-side symmetric oblique laser shock peening on shape deviation, surface integrity, and fatigue properties of the blades in small-sized blisk

Double-sided symmetric oblique laser shock peening (DSOLSP) was adopted to experiment on a small-sized blisk with restricted space. The influences of different laser energies on the shape deviation, surface roughness, microhardness, and residual stress of the blades were studied. The optimum process parameters were selected based on the shape deviation results of the blades and the microstructural evolution of the surface layers was investigated. The strengthening effect of DSOLSP treatment on notched blades was evaluated by vibration fatigue tests. It was found that DSOLSP can effectively cover the fatigue vulnerable regions without interference. Two-way bending deformation was formed after DSOLSP, and the shape deviation of the blades could be controlled within ±0.02 mm. With the increase of laser energy, the surface roughness and the depth of work-hardened layer increased. The full-thickness compressive residual stress (CRS) field was induced. A gradient microstructure was generated on the surface of the blade, and the size of average nanograins on the topmost surface is approximately 36.5 nm. The fatigue strength of the DSOLSP treated blades with notches was increased by 25.9 %. The enhancement can be attributed to the synergistic strengthening of CRS and gradient microstructure.

Hydrogen charging can relax compressive residual stresses caused by shot peening

Surface engineering to generate compressive stresses via processes such as shot peening is commonly employed to mitigate fracture or fatigue failures in metallic systems. Localized plastic deformation is used to generate the generally biaxial compressive elastic stresses. This study examined the residual stress conditions and local mechanical performance of medium carbon steel in a quenched and tempered state. Electrolytic hydrogen charging of peened samples led to a permanent reduction in the compressive surface stress while concurrently hardening the surface. Slight changes in elastic modulus when solute hydrogen was present could not explain the resulting change in the measured residual stress; a reduction in X-ray peak breadth suggests that the combined effects of elastic stresses and solute hydrogen caused local dislocation annihilation and re-organization of the dislocation structure in the severe plastically deformed layer, leading to a lower magnitude and shallower depth of compressive residual stress on the peened surface after hydrogen charging.

Cryogenic and conventional milling of AZ91 magnesium alloy

Use of magnesium is the need of the hour due to its low density as well as its high strength-to-weight and stiffness-to-weight ratio etc. This study focuses on the effectiveness of liquid nitrogen (LN2) assisted cryogenic machining on the surface integrity (SI) characteristics of AZ91 magnesium alloy. Face milling using uncoated carbide inserts have been performed under liquid nitrogen (LN2) assisted cryogenic condition and compared with conventional (dry) milling. Experiments are performed using machining parameters in terms of cutting speeds of 325, 475, 625 m/min, feed rates of 0.05, 0.1, 0.15 mm/teeth and depth of cuts of 0.5, 1, 1.5 mm respectively. Most significant surface integrity characteristics such as surface roughness, microhardness, microstructure, and residual stresses have been investigated. Behaviour of SI characteristics with respect to milling parameters have been identified using statistical technique such as ANOVA and signal-to-noise (S/N) ratio plots. Additionally, the multi criteria decision making (MCDM) techniques such as additive ratio assessment method (ARAS) and complex proportional assessment (COPRAS) have been utilized to identify the optimal conditions for milling AZ91 magnesium alloy under both dry and cryogenic conditions. Use of LN2 during machining, resulted in reduction in machining temperature by upto 29% with a temperature drop from 251.2 °C under dry condition to 178.5 °C in cryogenic condition. Results showed the advantage of performing cryogenic milling in improving the surface integrity to a significant extent. Cryogenic machining considerably minimized the roughness by upto 28% and maximised the microhardness by upto 23%, when compared to dry machining. Cutting speed has caused significant impact on surface roughness (95.33% – dry, 92.92% – cryogenic) and surface microhardness (80.33% – dry, 82.15% – cryogenic). Due to the reduction in machining temperature, cryogenic condition resulted in compressive residual stresses (maximum σ║ = -113 MPa) on the alloy surface. Results indicate no harm to alloy microstructure in both conditions, with no alterations to grain integrity and minimal reduction in the average grain sizes in the near machined area, when compared to before machined (base material) surface. The MCDM approach namely ARAS and COPRAS resulted in identical results, with the optimal condition being cutting speed of 625 m/min, a feed rate of 0.05 mm/teeth, and a depth of cut of 0.5 mm for both dry and cryogenic environments.

Ultrasonic peening-waterjet composite surface modification of 7075-T6 aluminum alloy for residual stress release and transformation mechanism

The release and transformation mechanism of residual stress contributes to the improvement of metal materials' processing and performance, enhancing their structural stability, surface integrity, and fracture resistance. This paper focuses on the Ultrasonic Impact Treatment-Solid Particle Entrainment by Waterjet (UIT-SPEWJ) composite surface modification of 7075-T6 aluminum alloy, investigating the effects of UIT-SPEWJ process parameters (jet pressure and target distance) on the alloy's surface quality, roughness, microhardness, residual stress, and the evolution mechanism of microstructure. The results indicate that the 7075-T6 aluminum alloy modified by UIT-SPEWJ mainly exhibits a "meteorite crater" effect, accompanied by significant smearing and ploughing phenomena. Surface roughness shows a trend of first decreasing and then increasing with the rise of jet pressure and target distance. The minimum surface roughness, 0.852 μm, is achieved at a jet pressure of 25 MPa and a target distance of 7.5 mm. The microhardness of the samples modified by UIT-SPEWJ gradually decreases from the surface to the substrate with increasing depth. The hardened layer depths of the samples UIT-SPEWJ-1–6 after modification are approximately 174 μm, 226 μm, 200 μm, 196 μm, 176 μm, and 172 μm, respectively. After UIT, SPEWJ, and UIT-SPEWJ surface modifications, the surface of 7075-T6 aluminum alloy mainly exhibits compressive residual stress (CRS). The surface residual stress σ_srs of samples modified by UIT and SPEWJ are approximately 195.161 and 215.752 MPa, respectively. The surface residual stresses of UIT-SPEWJ-1–6 samples are significantly improved to 277.089, 529.499, 393.615, 459.261, 368.084, and 220.635 MPa, respectively, with UIT-SPEWJ-2 sample having the highest surface residual stress, which is 2.7 and 2.4 times that of UIT and SPEWJ modified surfaces. Samples modified by UIT-SPEWJ present significant dislocation phenomena, and the precipitated phases mainly include the needle-like metastable phase η', as well as the equilibrium phase η (MgZn2) with a rod-like structure. At lower jet pressures and larger target distances, the 7075-T6 aluminum alloy exhibits a continuous PFZ with a size of approximately 12–23 nm. As jet pressure increases and target distance decreases, discontinuous grain boundary precipitate bands appear, sized around 8–17 nm. Moreover, when the jet pressure is 25 MPa and the target distance is 7.5 mm, the grain boundary precipitated phases are more dispersed.

Cryogenics performance enhancement of epoxy resin composites through negative expansion nanomaterials: Mechanism and predictive modeling

AbstractThe matrix cracking of carbon fiber reinforced epoxy resin based composites (CFRPs) at cryogenics (such as liquid nitrogen temperature) is a major issue affecting the normal operation of deep space and deep‐sea detectors, as microcracks caused by the thermal residual stress of both can reduce the structural integrity of the devices. In this work, we report an epoxy (EP) nanofiller CuO nanorods (CuO NRs) with negative thermal expansion properties at cryogenics. Experiments showed that CuO NRs can effectively inhibit the shrinkage of EP at cryogenics and improve the mechanical properties of EP at cryogenics. A temperature dependent prediction model for the tensile strength of EP/CuO NRs was proposed, and the predicted results were in good agreement with experimental results. Finally, through a combination of experiments and theory, it was demonstrated that the tensile strength of EP/CuO NRs at cryogenics is jointly enhanced by the enhancement effect of the nanomaterials and the axial compressive thermal residual stress between EP and CuO NRs.Highlights Successfully prepared CuO nanorods with negative expansion properties at low temperatures, and found that they can effectively inhibit the shrinkage of epoxy resin at cryogenics. At cryogenics, the expansion of CuO nanorods enhances their interface effect with epoxy resin and improves the tensile strength of epoxy resin composites. The theory of tensile strength of epoxy resin at cryogenics was proposed for the first time. Theoretical analysis shows that the low temperature residual thermal stress between CuO nanorods and epoxy resin is the main factor to improve its tensile strength.

The contradictory feather of Cr thin film compressive residual stress generation under energetic depositions

Ion bombardment is an important approach to generate thin film compressive residual stress independent of film growth through energetic deposition. In this study, a series of Cr/Si(100) thin films were energetically deposited using Modulated Pulsed Power Magnetron Sputtering (MPPMS) to learn the residual stress variation. The steady residual stress of Cr/Si(100) thin films, ex-situ characterized based on Stoney’s equation, exhibited a compressive nature with the maximum stress observed at approximately 100–150°C as the substrate temperature increased to 220°C. The steady residual stress variation was inconsistent with calculated thermal stress and intrinsic growth stress, and the calculated compressive stress for the adatom insertion and ion bombardment are contradictory under varied temperatures. The ability of adatom movement and insertion to grain boundaries promote the formation of compressive stress, while the defect annihilation and atom rearrangement inhibit the ion bombardment-induced residual stress.

Study on the corrosion fatigue properties of ultrasonic surface strengthened axle steel

Owing to fatigue damage and environmental erosion, locomotive axles are prone to premature failure during service. It is therefore very important to improve the corrosion fatigue properties of axles. In this paper, the fatigue behavior of ultrasonic surface strengthened axle steel under corrosive environment was studied. The surface integrity of ultrasonic strengthened axle steel was characterized by microscopic analysis and hardness test. The fatigue data and fatigue fracture of axle steel under corrosion environment were compared. Also, the mechanism of the corrosion environment on fatigue crack initiation and propagation was analyzed. Results show that serious plastic deformation is generated in the surface of axle steel after ultrasonic strengthening. The grains in surface layer are obviously refined and get coarse gradually as deep into the matrix. The hardness of surface layer is greatly improved as well. The maximum value is located on the outermost surface, about 2 times of the matrix. Under the same fatigue load, the fatigue cycle number for ultrasonic strengthened axle steel is more than that of original sample. This is due to grain refinement, work hardening, and residual compressive stress induced by ultrasonic strengthening, which inhibits fatigue crack initiation in corrosion environment.

Investigating the effects of steel strength and tensile overload level on fatigue crack growth performance

Individual overloads (OLs) might significantly relax tensile residual stresses (RS) besides generating compressive RS in welded components and, thus, influence the fatigue performance of these components. This study seeks to investigate the effects of steel strength and OL level on the fatigue life performance of welded components. Welding calculations were first performed for different steel grades to predict welding RS (WRS). A series of numerical fatigue calculations were conducted using the elastic–plastic fracture mechanics approach based on FEM to comprehend the fatigue performance under various OL levels. The fatigue calculations were performed in the absence and presence of the WRS effect. The results showed that the higher-level OLs improved the fatigue performance of components made of higher-strength steel when the WRS effect was considered. In contrast, in the absence of the WRS effect, an improvement in fatigue performance was achieved from the higher-level OLs by lower-strength steel. Also, a remarkable RS relaxation with varying degrees was induced from the higher-level OLs for the applied steel grades. This variation in the degree of RS relaxation could be attributed to the difference in WRS distributions over the crack surface. The crack driving force and retardation effect were also used to support the study.

Effect of laser shock peening on tribological properties of WC-Ni under seawater conditions: Anomalous behavior and solutions

This research investigated the effect of laser shock peening (LSP) on the tribological properties of WC-Ni under seawater lubrication. The experimental findings revealed an anomalous behavior, contrary to the existing literature, indicating that the LSP treatment actually deteriorated the tribological properties of WC-Ni. The mechanism and solutions for anomalous behavior were also examined, and the results indicated that the enhancement of material properties through LSP treatment cannot counterbalance the detrimental effects of increased surface roughness. For improved processes, the sample treated with LSP + Polish exhibits the highest residual compressive stress and the lowest surface roughness, thereby yielding the best comprehensive performance. Therefore, the experimental results demonstrate that LSP + Polish treatment can improve material performance and hydrodynamic effect, leading to reductions in friction and wear.

Residual stress depth profiles self-developed in cathodic arc deposited Ti-Al-N coatings prepared at different constant substrate bias values

Ti-Al-N coatings were prepared by cathodic arc deposition on Inconel 718 substrates at different values of constant substrate bias voltage, aiming to produce samples with different self-developed residual stress (RS) depth profiles through the thickness of the coatings. RS profile measurements and structural characterization were performed on a laboratory-scale x-ray diffraction system (x-ray energy of 8 keV) and in a synchrotron x-ray radiation facility (x-ray energy of 15 keV). Mechanical testing to obtain hardness and Young’s modulus values was performed by instrumented nanoindentation. The results indicate higher compressive RS at the film/substrate interface that decays to lower compressive stress or mild tensile stress at the film surface. Surface hardness and the compressive RS value of the coating increase with larger values of the substrate bias voltage. By comparing the stress characterization done on a laboratory scale and at the synchrotron facility, one observes a generally good agreement, indicating that these analyses may be conducted at a smaller scale and with less costly equipment, and still maintain a reliable precision. The work presents and reviews in detail the methodology of the RS depth-profile analysis. The highest hardness of 31.1 GPa and near-substrate compressive RS around −10 GPa were obtained for a bias of −100 V. Transmission electron microscopy results indicate that regions with higher compressive stresses are found to have smaller columns and denser structure, while portions of the same sample with mild compressive or tensile stresses present larger column size and are richer in hexagonal phases. The findings demonstrate the complex interplay between stress, microstructure, and ultimately mechanical properties in industrially produced Ti-Al-N coatings and indicate that any successful strategy to mitigate stress development should consider the inhomogeneous self-developed stress gradients present even in coatings deposited under constant and controlled conditions.

The effect of fine particle peening on aviation gear performance, Part I: Surface integrity

AbstractAs a fundamental component of aviation equipment, the gear has an essential effect on the service performance of the whole machine. Fine particle peening (FPP) technology is a good choice for the precision requirements of aviation gears. Therefore, a FPP model of aviation gears was constructed based on the discrete element‐finite element coupling method (DEM‐FEM) to simulate the evolution of surface roughness and residual compressive stress, and its results were verified by experiments. The effects of FPP intensity, coverage rate, and particle diameter on surface integrity were investigated. In addition, the importance degree of the intensity, coverage rate, and particle diameter of FPP on surface integrity was carried out by the random forest decision method. It demonstrates that the surface roughness Sa was mainly influenced by the FPP intensity and particle diameter. And the distribution state of the residual compressive stress was mainly affected by the particle diameter.

Effect of Thickness on the Residual Stress Profile of an Aluminum Cold Spray Coating by Finite Element Analysis

This research investigates the influence of thickness on residual stress profiles in aluminum cold spray coatings using finite element analysis (FEA). Residual stress is a critical factor that impacts coating adhesion, fatigue life, and susceptibility to delamination in thermal spray processes. Despite its acknowledged importance, predictive analysis of these stresses on a layer-by-layer basis remains relatively unexplored. This study introduces an innovative numerical methodology to analyze the progression of residual stresses across various deposition efficiencies (10%, 40%, 60%, and 100%) and layer thicknesses, thereby enhancing predictive accuracy for cold spray coatings. The findings demonstrate that the number of deposited layers significantly affects residual stress profiles in both coatings and the substrate, with compressive residual stress predominating in the coatings and deeper tensile stress predominating in the substrate. Residual stress behavior near the last deposited layer aligns with the expected peening effect. Discrepancies in substrate stress distributions may arise from variations in deposition parameters and unconsidered temperature effects. While the model generally aligns with theoretical and some empirical data, observed discrepancies underscore the need for further validation. This study lays the groundwork for informed decision-making for cold spray processes by providing insights into stress management, thereby contributing to enhancing coating integrity and performance.