X-ray Diffraction Residual Stress Measurements Research Articles

Research on the residual stress induced by square-spot laser shock peening on 2024-T351 specimens

Laser peen forming (LPF) is an appealing technique for forming metal sheets using high-energy, short-duration laser pulses. The deformation of the target metal plate is closely related to the magnitude and distribution of laser-induced residual stress. Consequently, the relationship between process parameters and residual stress is worth researching. In this research, two process parameters in LPF, laser energy and coverage ratio (spot distance essentially), and one workpiece parameter, plate thickness, were examined through an element method (FEM) of multiple square-spot laser shock peening (SSLSP). Corresponding experiments of SSLSP on aluminum alloy 2024-T351 test blocks were conducted, together with an X-ray diffraction (XRD) residual stress measurement and a surface morphology observation. The FEM simulation and experimental results show that congested laser spots had a significant influence on the magnitude of compressive residual stress; higher laser energy was beneficial to the depth of the compressive stress layer but could decrease its magnitude. Therefore, for better forming ability, higher laser energy and a higher coverage ratio are beneficial; for surface strengthening, laser energy should not be too large, and the coverage ratio should be larger than 100% to ensure that the residual stress on the treated surface is compressive, resulting in better surface integrity.

3-D FE modelling of residual stress distribution in 3003 aluminium alloy overlapped joints by ARM laser with beam oscillations

Adjustable Ring Mode (ARM) laser technology combined with Beam Oscillation optics module was introduced to effectively enhance weld quality in joining aluminium alloys. This study developed a three-dimensional (3-D) thermo-mechanical finite element (FE) model to analyze the distribution of thermally induced residual stresses in laser-welded 3003 aluminium alloy. The accuracy of model was validated through comparisons with experimental weld cross-sections and further reinforced by X-ray diffraction residual stress measurements. The transient temperature field and stress distribution during the welding process were investigated using the verified model. Additionally, the hardness and microstructure of the welded samples were examined through micro-hardness tests and scanning electron microscopy. Results showed that welding with beam oscillation resulted in less penetration but higher hardness and finer columnar grain size in the fusion zone. Additionally, the influence of varying standoff distances between two sequential weld beads on residual stress distribution was investigated. Numerical findings revealed that higher residual stress concentrations were located at the weld seam and dominated by tensile longitudinal residual stress and compressive transverse residual stress. As the distance between weld beads increased, transverse and equivalent residual stresses decreased, while longitudinal residual stress away from the bead increased.

Residual stresses of MAG-welded ultrahigh-strength steel rectangular hollow sections

Residual stresses are an important factor in the performance and stability of welded structures. This study investigates the characteristics and significance of residual stresses in MAG-welded ultrahigh-strength steel rectangular hollow sections. The research incorporates comprehensive X-ray diffraction residual stress measurements, electron backscatter diffraction analysis, statistical analyses, and finite element method simulations to provide valuable insights into the behaviour of welding residual stresses. The results reveal clear microstructural variations between the cold-formed corner and the flat side of the rectangular hollow section caused by welding heat input, emphasizing the need to consider these variations in residual stress assessments. Furthermore, the study examines the dependence of residual stresses on the steel grade, with higher strength steel exhibiting compressive stresses and lower strength materials experiencing tensile stresses in corner areas. Statistical analysis indicates that welding sequence and direction have negligible effects when applying the employed welding sequence. In any case, higher heat input leads to significantly larger residual stresses. Finally, the study presents a novel analytical model based on validated finite element simulations to predict the maximum variation of residual stresses depending on welding heat input. The findings provide valuable insights into the significance of welding residual stresses and their predictability. The comprehensive measurements, simulations and proposed models contributes to a better understanding of residual stress phenomena, facilitating the development of reliable design guidelines for welded structures in various engineering applications.

Residual stress and microstructure control in welding of SA508 low alloy steel

Various types of solid-state phase transformation (SSPT) occur during the SA508 steel welding process, especially for multi-pass welding. The multiple thermal cycles lead to a more complex microstructure distribution and significantly influence the residual stress distribution. Therefore, to better control the microstructure and residual stress, it is necessary to optimize the process parameters which are closely related to the welding thermal cycles. This study established a thermo-mechanical-metallurgical multi-field coupling model and then validated it using X-ray and neutron diffraction residual stress measurement tests. Furthermore, the influence of welding heat input and preheating temperature on the formation of phase constituents and the ultimate residual stress field were analyzed in detail, concomitantly with a comprehensive discussion on their underlying mechanisms. The results showed that the increase of heat input expanded the domain occupied by the bainite phase, accompanied by the increase of compressive stress region. Moreover, the rise of preheating temperature promoted the bainite phase transformation, thus decreasing the longitudinal compressive stress and the stress gradient. The variation induced by welding parameters was closely related to the welding cooling rates. To obtain a full bainite and low residual stress condition of welded joint, it becomes imperative to exercise control over cooling rates, maintaining them at approximately 1.0 °C/s.

Residual stress determination by the layer removal and X-ray diffraction measurement – correction method

Very often a manufacturing process is followed by some surface treatment. Such a process induces residual stress into the manufactured component. Compressive residual stress is desirable for enhancing the fatigue properties of the component. The residual stress is often measured only at the surface, if at all. However, residual stress is equilibrating in the whole component. Therefore, compressive residual stress at the surface induces undesirable tensile stress inside in the component. Knowledge of the residual stress distribution in a body can be very useful in engineering applications. The authors found this knowledge necessary for a proper description of fatigue crack propagation in railway axles described in the original paper [1]. With the onset of modern surface treating technologies, e.g. induction hardening, which can affect the entire cross-section of the component, the residual stress determination is even more critical.The presented paper aims to describe a procedure developed for proper residual stress determination. The procedure can be easily used e.g. in R&D centers, where X-ray diffraction residual stress measurement is already in use. The procedure is suitable for the residual stress determination in sizable cylindrical bodies or components, e.g. railway axles. It uses X-ray diffraction residual stress surface measurement and layer removal by machining. Results experimentally obtained are corrected by a general procedure developed in MATLAB software in order to obtain the original residual stress state in the cylindrical body.•More accurate procedure for a residual stress determination in cylindrical bodies.

Improving the fatigue performance of vanadium and silicon alloyed medium carbon steels after nitriding through increased core fatigue strength and compressive residual stress

The fatigue performance of nitrided medium carbon steels, alloyed with V and Si, and heat treated to form martensite and bainite microstructures, was evaluated using cantilever bending fatigue testing. Hardness testing and X-ray diffraction residual stress measurements were used in conjunction with an analysis of the applied stress distributions to determine vulnerable regions of crack initiation. The analysis was correlated with experimental scanning electron microscopy observations of crack initiation location. Increases in V and Si content lead to higher core hardness and higher core fatigue strength which increase the applied stress needed to initiate fatigue failure originating subsurface below the case. Increases in V and Si content also increase the magnitude of compressive residual stress, which increases the applied stress needed for surface initiated failure. The combination of increased core fatigue strength and magnitude of compressive residual stress improve the fatigue performance after nitriding compared to other nitrided medium carbon steels reported in literature.

Effects of shot peening and artificial surface defects on fatigue properties of 50CrV4 steel

Shot peening processes are commonly used for improving the fatigue properties of steels. Shot peening introduces a compressive residual stress field in the near surface of steel, which can reduce or stop the growth of fatigue cracks and improve fatigue properties. This study experimentally investigated the effect of shot peening on the fatigue properties of 50CrV4 steel alloys with different artificial surface defects. Drilling tools were used to introduce different artificial defects with root radii of 0.585 mm and 0.895 mm on the surface of unpeened samples. The shot peening was applied to the drilled and undrilled samples. Scanning electron microscopy (SEM) observations, micro-hardness and X-ray diffraction residual stress measurements were conducted to analyse the characteristics of the shot-peened and unpeened samples. The results show that the shot peening leads to the transformation of the retained austenite to martensite in the near-surface microstructure. The hardness rates of the surface and near surface both increase by 8% after the shot peening. The peened samples exhibit compressive residual stresses with a high degree of isotropy in the near surface. The fatigue properties of samples were experimentally evaluated by conducting 3-point bending tests. The results indicate that the shot peening improves the fatigue life of drilled and undrilled samples. For the defects with the root radius of 0.895 mm, the shot peening leads to a 500% improvement in the fatigue life compared to unpeened samples regardless of defect depth. For the defects with the root radius of 0.585 mm, the improvement in fatigue life is 40% for the defect depth of 0.2 mm compared to unpeened samples. The improvement increases to 60% and 200% by increasing the defect depths to 0.4 mm and 0.6 mm. The fatigue properties are linked to the changes in the features of defects mainly caused by the deformation hardening and compressive residual stress after shot peening.

Investigating the residual stress in additive manufacturing of repair work by directed energy deposition process on SS316L hot rolled steel substrate

The aim of this research is to conduct a systematic investigation of the directed energy deposition of stainless steel 316L powder in order to evaluate and investigate residual stresses caused by the laser deposition process. In metal additive manufacturing, predicting residual stress is critical for ensuring the quality of the fabricated part. Stainless steel 316L cubes were prepared by directed energy deposition process on hot rolled steel substrate for the repair work purpose. To evaluate the effect of the residual stress of sandwich samples, which can be compressive or tensile. Also, to investigate the residual stresses developed on the interface region for between the directed energy deposition, and hot rolled steel sample. Finally, it is found that the residual stresses on the hot rolled steel surfaces in the compressive stress (-855 MPa), on other hand compressive stress has obtained in the directed energy deposition surface (-822 MPa). The residual stresses were determined experimentally using X-Ray Diffraction (XRD) residual stress measurements.

Surface Layer Characterization of Shot Peened Gear Specimens

Abstract The production of gear components includes numerous manufacturing operations, which are carried out to ensure proper surface characteristics. Shot peening is one of the surface finishing processes used for transmission components like gears to improve their fatigue behavior. Shot peening increases the compressive residual stresses on the surface, and the procedure also reduces the amount of retained austenite in the surface layer. In addition, shot peening has an influence on other mechanical properties, such as surface roughness and surface hardness. An experimental design was conducted with varying shot peening process parameters, like coverage density and intensity, to alter the surface layer of 13 transmission gear specimens. The correlation between shot peening parameters, Barkhausen noise (BN) features, and X-ray diffraction residual stress measurement was studied. Linear correlation was found between residual stress and shot peening parameters. The relationship between residual stress and BN root-mean-square was not evident but was revealed by taking the ratio of BN measurements at different frequencies. Additionally, BN features, such as peak position, coercivity, and integral area, were found to have a linear trend with the intensity. Along with the aforementioned measurements, other material characterization measurements were also taken. The shot peening coverage density was observed to have a linear relationship with surface roughness values, while an intensity of over 0.6 mm A was noticed to affect the surface hardness. The results obtained can be used in the determination of suitable shot peening parameters to achieve a surface with desired residual stress and other surface properties.

X-ray Diffraction Residual Stress Measurement at Room Temperature and 77 K in a Microelectronic Multi-layered Single-Crystal Structure Used for Infrared Detection

The electronic assembly considered in this study is an infrared (IR) detector consisting of different layers, including (111) CdHgTe and (100) silicon single crystals. The processing steps and the low working temperature (77 K) induce thermomechanical stresses that can affect the reliability of the thin and brittle CdHgTe detection circuit and lead to failure. These residual stresses have been quantified in both CdHgTe and silicon circuits at room temperature (293 K) and cryogenic temperature using x-ray diffraction. A specific experimental device has been developed for 77 K measurements and a method developed for single-crystal analysis has been adapted to such structures using a laboratory four-circle diffractometer. This paper describes the methodology to obtain the deformed lattice parameter and compute the strain/stress tensors. Whereas the stresses in the CdHgTe layer appear to be negative at room temperature (compressive values), cryogenic measurements show a tensile biaxial stress state of about 30 MPa and highlight the great impact of low temperature on the mechanical properties.

Influence of Support Configurations on the Characteristics of Selective Laser-Melted Inconel 718

Samples fabricated using two different support configurations by following identical scan strategies during selective laser melting of superalloy Inconel 718 were characterized in this study. Characterization methods included optical microscopy, electron back-scattered diffraction and x-ray diffraction residual stress measurement. For the scan strategy considered, microstructure and residual stress development in the samples were influenced by the support structures. However, crystallographic texture intensity and the texture components formed within the core part of the samples were almost independent of the support. The formation of finer grains closer to the support as well as within the columnar grain boundaries resulted in randomization and texture intensity reduction by nearly half for the sample built on a lattice support. Heat transfer rates dictated by the support configurations in addition to the scan strategy influenced the microstructure and residual stress development in selective laser-melted Inconel 718 samples.

Experimental Comparison of In-Depth Residual Stresses Measured with Neutron and X-Ray Diffraction with a Numerical Stress Relaxation Correction Method

This study is an experimental comparison of in-depth X-ray diffraction residual stress measurements with neutron diffraction measurements. The goal is to evaluate the relevance of the Savaria-Bridier-Bocher [1] stress relaxation correction method. Neutron diffraction are performed on a bent notched specimen. Destructive X-ray diffraction is performed until 5.25mm below the surface by polishing the material. This polishing induces stress relaxation and X-ray diffraction results have to be corrected. For that purpose, a finite element analysis is realised and show good correlation with neutron measurements results. The application of the stress correction method improves the X-ray measurements especially after 2 mm below the surface. The differences between measured and corrected residual stresses from both diffraction techniques are analyzed and discussed.

High-Precision Determination of Residual Stress of As-Sprayed and Ground WC-10Co-4Cr Coating Using Optimized XRD-sin<sup>2</sup>ψ Technique

Thermally sprayed tungsten carbide-based coatings deposited by High Velocity Oxygen Fuel (HVOF) has been widely developed for its high corrosion and wear resistance. The finishing of the coated surface by grinding process is essential because of the high surface roughness of carbide coatings. Residual stresses existing in most hard coatings have significant influence on the adhesion, mechanical properties and tribological performance. The present study investigated the effect of grinding process on the residual stress of WC-10Co-4Cr coating by HVOF. The residual stress of coating was measured by the X-ray diffraction (XRD) technique using sin2ψ method. In addition, the effect of diffraction peak positioning method on the accuracy of residual stress of WC-10Co-4Cr coating was determined in the XRD technique. Four peak positioning methods and their effects on the accuracy of X-ray diffraction (XRD) residual stress measurement are considered. The results showed that the compressive residual stress of the WC-10Co-4Cr coating increase after grinding process. The parabolic method was selected for the peak positioning to measure the precise residual stress of HVOF-deposited WC-10Co-4Cr coating.

Service Loading of Rolling Bearings in Wind Turbine Gearboxes: X-ray Diffraction Material Response Analysis of White Etching Crack Premature Failures

ABSTRACTRolling bearings in wind turbine gearboxes occasionally fail prematurely due to white etching cracks. The appearance of preparatively opened fracture faces indicates damage initiation from the surface in most cases due to brittle spontaneous tensile stress–induced cracking. Under the influence of decomposition products of the penetrating lubricant, branching crack growth is subsequently driven by corrosion fatigue. The material response analysis of rolling bearings from all gearbox locations, based on X-ray diffraction residual stress measurements, reveals vibrations in service as the root cause of surface crack initiation. The occurrence of high local friction coefficients in the rolling contact is described by a tribological model. Depth profiles of the equivalent shear and normal stresses are respectively compared with the measured residual stress patterns and a relevant fracture strength. White etching crack failures are experimentally reproduced on a rolling contact fatigue test rig under increased mixed friction. Causative vibration loading is evident from material response analysis. The generation of compressive residual stresses by cold-working the surface is proven to be an effective countermeasure.

Austenite phase transformation of SKD11 by surface heat treatment with a focused electron beam

Recently, many studies have been actively conducted to improve the mechanical properties of metallic materials through surface heat treatment with an electron beam. Thermionic focused electron beam equipment is mainly used in industrial manufacturing machines such as e-beam welders. However, such equipment is expensive, and the filament lifetime is limited. In this study, the austenite transformation in an iron matrix was investigated after surface heat treatment of SKD11 with plasma diode focused electron beam equipment, which is a recently developed alternative based on a plasma diode cold cathode. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the iron matrix transformed to an austenite structure without Cr-rich carbide formation. After the surface heat treatment using the plasma diode focused electron beam equipment, a positive residual stress was confirmed by XRD residual stress measurements. This result was obtained because impurities in the iron matrix such as carbon existed in alloy form rather than composite form. The average hardness at a depth of 300μm from the surface was measured to be approximately 480Hv.

Effect of Peak Positioning Method on Accuracy of X-Ray Diffraction Residual Stress Measurement

Effect of Peak Positioning Method on Accuracy of X-Ray Diffraction Residual Stress Measurement

Fatigue behavior of cold spray coatings: The effect of conventional and severe shot peening as pre-/post-treatment

Abstract Cold spray coating is gaining increasing attention as a solid state additive technique for repairing structural components. The fatigue behavior of Al 6082 cold spray coating with the same material as substrate is studied. Furthermore, the possibility of improving the load bearing capacity of the cold spray coated specimens by shot peening process is explored. Conventional and severe shot peening were applied before and after cold spray depositions. The coated, coated-peened and peened-coated specimens were characterized by optical microscopy observation, surface roughness and X-ray diffraction residual stress measurements. The specimens were subjected to rotating bending fatigue tests in order to determine the fatigue strength. Unlike the fixed-cantilever, constant-deflection thin specimens, often used to measure fatigue strength of cold spray coatings, the present approach does not considerably reduce the applied stress at the interface compared to the nominal stress and thus represents a more critical and realistic response of the coatings to fatigue loading conditions. The fractured surfaces were examined by scanning electron microscopy. Cold spray coating increased the fatigue strength by 15% compared to the as-received specimens. Further improvement was achieved by the hybrid peening and coating treatment. It was found that shot peening is more efficient if it is performed prior to cold spray deposition. A 26% improvement in the fatigue strength was obtained by performing severe shot peening prior to cold spray deposition. This improvement was attributed to the integrity of coating/substrate interface without any signs of delamination, crack initiation from the surface instead of the interface, crack propagation mainly by transcrystalline mechanism and not through particle boundaries and finally high depth of compressive residual stresses.

Neutron and X-Ray Diffraction Residual Stress Measurements in Aluminium Alloys MIG Welded T-Joints after Friction Stir Processing

Friction Stir Processing (FSP) is a relatively new post-processing technique. Fatigue strength of MIG fillet welds of aluminium alloys can be substantially improved using FSP. Beyond other properties intrinsically tied to fatigue life, especially attention should be paid to the effect of the final residual stress state. In this study the residual stress distribution in T-joints of two aluminium alloys was determined by Neutron and X-ray diffraction. FSP effect on the residual stress state and fatigue life was analysed.

X-Ray Diffraction Residual Stress Measurements for Assessment of Rolling Contact Fatigue Behaviour of Railway Steels

Rolling contact fatigue twin-disc tests were performed on rail/wheel steels from Spanish high velocity trains (AVE). Residual stress profiles were determined using X-ray diffraction before and after cyclic loading. The evolution of residual stress profiles, due to cyclic loading, was analysed in order to study how they affect the rolling contact fatigue behaviour of these materials. This study is included in a major project where other related phenomena and materials’ properties have been studied.

The Use of Renka Cline Algorithm in X-Ray Diffraction Residual Stress Measurement

Using the Renka Cline algorithm provided by OriginPro8.6 to fit the longitudinal residual stress through parts of the measurement value on the A7N01-T5 aluminum alloy butt welded joints compared with the whole measurement value. The result shows that the fitting value approximates the measurement value. The fitting value is reliable. So, Renka Cline algorithm is a reliable method to analyze the longitudinal residual stress on a plate region.