X-ray Residual Stress Research Articles

Investigation into the cavitation erosion of rolled Ti6Al4V titanium alloy strengthened by the ultrasonic-assisted laser shock peening process

The novel process known as ultrasonic-assisted laser shock peening (ULSP) is conducted on hot rolled Ti6Al4V titanium alloy with polished surface to improve its cavitation erosion (CE) resistance. The microstructure and phase structure were investigated by transmission electron microscope and X-Ray diffractometer. The microhardness and residual stress were measured by microhardness tester and X-Ray residual stress analyzer. After that, the CE mass loss and morphology were analyzed through high-precision analytical balance and scanning electron microscope to reveal the CE resistance mechanism of ULSP. The results show that ULSP treatment causes plastic deformation at the surface layer, resulting in refined grains and complex dislocation structures. The aforementioned process produces a hardened layer and compressive residual stress (CRS) layer with notable amplitude and deep influence. The surface microhardness of the ULSP-9J specimen is 410 ± 4 HV, which is a 14.8 % increase compared to the LSP-9J specimen. The CRS of the ULSP-9J specimen is −329 ± 6 MPa. As a result, it is vital in preventing the formation and propagation of CE cracks, strengthening the material's resistance to CE damage, reducing mass loss, and enhancing the overall morphology of CE.

Driving force for enhancing the cold silver sinter joining using time domain-dependent Ag–Au epitaxy and interfacial stress

We reveal the mechanism of the cold silver sinter joining process using time-dependent characteristics of Ag–Au interactions grown in the highly (111) orientation. In the initial (∼15 min) state at 175 °C, the Ag–Au inter-diffusion layers developed strongly in the (001) direction, and with increasing time (∼60 min), they switched epitaxial growth in the (111) orientation. The die-bonding strength was significantly improved from 14.9 MPa to 37.8 MPa when the sintering time increased from 15 min to 60 min. The gradual Ag–Au epitaxial growth behavior with a higher stacking-fault energy (SFE) at 175 °C was the dominant factor linearly increasing the cold silver sinter joining strength and ultimately maximizing energy absorption leading to fracture. The surface finish of Au, which can contribute to the time-dependent growth of Ag–Au inter-diffusion layers, underwent a dramatic transformation from a Cube texture to a γ-fiber texture over time. This change was attributed to the micro/nanoscale shear deformation, and reduction of the twin boundary fraction. This study unveiled the in-depth fundamental mechanism for strengthening and pressureless cold sinter joining of Ag–Au epitaxial layers by comprehensively considering this texture behavior, changes in X-ray residual stress, and mechanical properties.

Experimental and numerical analysis of residual stresses induced by the manufacturing process of longitudinal welded tubes

In the present work, the process chain in tube production by roll forming of the steel 34MnB5 was examined in more detail. The process chain consisting of the steps (i) roll forming, (ii) HFI welding, and then (iii) straightening and final calibration was mapped using the finite element method. In addition to the pipe geometry, the residual stress distribution was considered as an essential target value for the assessment of the performance of the tubes under service conditions. The objective of the project is to describe the manufacturing process and thus the processing induced residual stress distributions as realistically as possible. For a more detailed characterization of the process and above all for the validation of the numerical simulations, experimental residual stress analyses were carried out for the final state of the tubes using complementary analysis methods. The contour method was used to determine the 2D-distribution of residual stresses across the transverse and longitudinal sections of the manufactured pipes. These measurements were supplemented by local residual stress analyses using the incremental hole drilling method and X-ray residual stress analyses. The work thus pursues both a methodical approach to the analysis of the internal stresses induced by the process using complementary methods and also a manufacturing approach to the analysis and evaluation of the production chain. In particular for the axial components of the residual stresses, it can be shown that experimentally determined residual stresses correlate well with the numerically calculated values. The contour method is excellently suited to monitor the uneven distribution of the internal stresses over the pipe cross-section. The results of the simulation show that the overall residual stress distribution that is determined using the contour method mainly results from the plastic strains introduced by the roll forming process. X-ray and hole drilling analyses are shown to be more suitable for measuring locally present residual stresses at defined positions on the outer tube surface. In this way it can be shown that the simulation approach described provides an accurate model of the process.

Influence of different wet-blasting pressure on the surface integrity and tool cutting performance of hybrid CVD-TiN/TiCN/α-Al2O3/TiN coated tools

This paper investigates the effect of wet-blasting pressure on the surface integrity and tool cutting performance of hybrid CVD-TiN/TiCN/α-Al2O3/TiN coated tools. The hybrid TiN/MT-TiCN/α-Al2O3/TiN multilayer coating was deposited on the surface of the cemented carbide inserts by chemical vapor deposition (CVD) technique. Then the coated inserts were subjected to wet-blasting by aluminum oxide with varying pressure. The coatings were characterized by scanning electron microscopy, white light surface profiler, and X-ray residual stress diffractometer. The results indicate that the average residual tensile stress of the α-Al2O3 layer on the rake face of CVD-coated inserts gradually decreased with the increase of wet-blasting pressure. When the wet-blasting pressure reached 0.24 MPa, the residual tensile stress was transformed into compressive stress. It was accompanied by increased cutting edge roughness and cutting edge radius, reduced cutting edge coating thickness, and a change in rake face surface roughness. To understand the effect of the surface integrity change on the cutting performance of CVD-coated inserts, a case study designed for AISI 4340 steel machining under continuous and intermittent cutting conditions is performed. When the Al2O3 layer on the cutting edge is not peeled off by wet-blasting, the change of residual stress from tensile to compressive in the rake face of CVD-coated inserts can effectively improve the fracture failure resistance of inserts in continuous and intermittent cutting processes. When the Al2O3 layer on the cutting edge is peeled off by wet-blasting, the fracture failure resistance during intermittent cutting will be significantly reduced.

Ambient formation of high pressure Ag2Si2O5 and non-stoichiometric Ag0.3Al0.7 alloy under confinement

We report results of Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Analysis of X-rays (EDAX), X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectivity (XRR), and X-ray Diffraction (XRD) and residual stress measurement studies of Ag-silica composite films on Al(001) co-deposited from precursors and spin-coated at different frequencies under ambient conditions. FESEM and EDAX show Ag nanoparticle formation, and XRD, XPS, and XRR show Ag0.3Al0.7 alloy and Ag-rich silicate Ag2Si2O5 formation in all samples. The alloy is non-stoichiometric and non-equilibrium, while the silicate forms at high oxygen pressure. XRR shows the presence of three layers, nanoparticles on top, silicate in the middle, and alloy at the bottom, on an Ag-doped Al substrate. Film thickness decreases exponentially with frequency. Individual layers increase in crystal domain size with a frequency of 3000 rpm when the silicate layer thins below unit cell thickness and the growth has a two-dimensional preference. Our results suggest total confinement by film thinning and local confinement from the Ag nanolayer. Residual stress measurements on the films deposited at 500 and 5000 rpms show a gradual increase in the tensile stress. The increase in spinning frequency reveals the formation of high pressure ambience.

Effect of contact stress and slip amplitude on fretting fatigue behaviour of ultrasonic surface nanocrystallized TC11 titanium alloy

In this paper, combined experimental and numerical methods are applied to investigate the effect of different contact stress and slip amplitude on the fretting fatigue (FF) behaviour of TC11 titanium alloy with gradient nanostructure introduced by ultrasonic surface rolling process (USRP). The properties of gradient nanostructure are characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray residual stress tester, microhardness tester. As evidenced by the FF experimental results, USRP can significantly improve the FF life of TC11 by introducing large compressive residual stress and work hardening layer. The dominant parameters in improving the FF resistance under different loading conditions are investigated. In addition, the simulated results from Abaqus show that contact stress plays a more important role in influencing FF life compared to fretting bridge span, which is attributed to the change in slip amplitude and stress concentration. Fretting fatigue life initially increases and then decreases with contact stress and there is a contact stress threshold that leads to minimum lifetime. This threshold of USRP specimens is greater than that of untreated specimens. The transition of fretting mode along with contact stress is observed and discussed.

Residual Stress Measurement of Used Mining Dump Truck Frame for Remanufacturing Purposes

Remanufacturing the main frame of a mining dump truck can save cost, energy, and materials in heavy equipment industries. It also can reduce CO2 emissions for environmental preservation to achieve sustainability. However, since the mainframe received a dynamic load during operation, it presumably leaves accumulated residual stresses in the frame. The residual stress, particularly tensile residual stress, stands out as a primary contributing factor to the initiation of cracks, which may ultimately result in failures. In this paper, the residual stress of the used mining dump truck main frame was identified by modeling simulation using FEA (finite element analysis) and actual measurement using a portable x-ray residual stress analyzer with the cos α method. The results showed that the weld area subjected to dynamic loads exhibited the highest tensile residual stress, reaching approximately +772 MPa. This specific region emerges as a critical area demanding attention during the remanufacturing process. The application of PWHT (post-weld heat treatment) at 400 °C for 1 hour effectively reduced residual stress on the weld joint, predominantly tensile residual stress, by more than 80%.

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.

Surface topography assessment using chemical assisted ball end magnetorheological finishing

The generation of residual stresses by grinding process on the surface for a soft material result in poor performance and diminished life. Ball end magnetorheological finishing (BEMRF) process is a recently developed process that is effectively used for fine figuring and polishing of a variety of magnetic and non-magnetic materials. In this paper, grinding-induced residual stresses are addressed, and an attempt is made to relieve these residual stresses while achieving high surface finish using chemical assisted ball end magnetorheological finishing (CA-BEMRF) process. The chemical used in the present work is applied first time in BEMRF process and aluminium 7075 alloy workpiece has not been finished with this novel finishing process. The impact of various CA-BEMRF variables on percentage surface roughness reduction and percentage reduction in residual stresses are discussed statistically and graphically. Residual stresses of workpiece surfaces have been measured by using portable x-ray residual stress analyzer. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the finished workpiece before and after CA-BEMRF process is carried out to assess the effects of magnetizing current, tool rotation and working gap on surface topography of machined surface. It has been observed that reduction in residual stress is achieved along with high surface finish on aluminium workpiece surface using CA-BEMRF technique. Significant process parameters affecting the residual stresses and surface roughness during polishing of workpiece are obtained using Analysis of variance (ANOVA) and F-test. The optimization problem for maximum percentage reduction in surface roughness and maximum percentage reduction in residual stress is formulated as multi objective, multi variable, nonlinear optimization problem. Maximum percentage surface roughness reduction and minimum residual stress has been found at magnetizing current 2.3 A, rotational speed of tool 550 rpm and working gap of 0.5 mm. Confirmatory experimental tests have been conducted and results obtained were found very close to the predicted outcome.

Thermal relaxation of compressive residual stresses in surface gradient nanostructure of TC11 titanium alloy

The thermal relaxation behaviour of compressive residual stress (CRS) in the gradient nanostructure of TC11 titanium alloy treated with ultrasonic surface rolling process (USRP) was investigated by X-ray residual stress test, transmission electron microscope (TEM) and high-resolution TEM (HRTEM). The Zener-Wert-Avrami (ZWA) model was successfully used to simulate the CRS relaxation behaviour in nanocrystalline and non-nanocrystalline regions at different temperatures. The results show that the relaxation of CRS is thorough and fast at higher temperature (650 ºC). There are two distinct relaxation stages at lower temperatures, and the relaxation rate in the first stage is much faster, dominated by the annihilation of lattice defects through short-range diffusion. The relaxation in the second stage is slow and dominated by dislocation rearrangement. In contrast to the situation at low temperatures, the nanocrystals appear to be a negative factor in stabilizing the CRS at high temperatures, as the unstable sub-grain boundaries act as sources of stress relaxation and the multiple grain boundaries act as high-speed diffusion channels and accelerate the annihilation of dislocations.

Effect of Scratching and Bending Degree on the Residual Stress of the 7055 Aluminum Alloy Plate

This study investigated the effects of scratches and bending on the surface stress of aluminum alloy plates with varying thicknesses. The purpose of this study was to provide guidance for surface stress testing of plates with different thicknesses. The “birth and death” element method was used to simulate the generation of surface scratches, while the stress field under the pre-stretched state was obtained through the displacement of one end of the board by 2.5%. The X-ray residual stress analyzer (μ-x360 s) was used to experimentally characterize the stress level on the surface of the plate. The research results showed that the residual stress level near the scratches decreases significantly, while the surface stress level of the plate decreases significantly after bending. The changes in stress values with increasing bending degree for plates of different thicknesses showed that the thicker the plate, the greater the tensile effect on the surface of the plate, resulting in smaller compressive stress. The longitudinal non-uniformity of the plates with different thicknesses was also analyzed, and it was found that the testing error of stress testing results was within ±5 MPa. In conclusion, this study provides useful guidance for the accurate measurement of surface stress on aluminum alloy plates of varying thicknesses, considering the effects of scratches, and bending.

Comparative study of the effects of conventional shot peening and ultrasonic shot peening on very high cycle fatigue properties of GH4169 superalloy

This study investigates the effects of two different shot peening techniques, conventional shot peening (CSP) and ultrasonic shot peening (USP), on the very high cycle fatigue (VHCF) properties of the GH4169 superalloy. The study evaluates and compares surface roughness, X-ray diffraction patterns, microhardness, and residual stress in specimens treated with CSP and USP. The VHCF tests reveal that both CSP and USP treatments improve the VHCF properties of the GH4169 superalloy. However, while the USP-treated specimens have deeper work hardening and compress residual stress layers, their VHCF lives are significantly shorter than those of the CSP-treated specimens. Additionally, the study finds that the stress triaxiality, which inhibits dislocations at the crack tip, is higher closer to the center of the specimen. The transmission electron microscopy (TEM) results further confirm that the reduced dislocation density and increased stress concentration in the plastic zone of the high stress triaxiality region promote fatigue short crack propagation and reduce the fatigue properties of the material.

Investigating the effect of laser shock peening on the wear behaviour of selective laser melted 316L stainless steel

Selective Laser Melting (SLM) is an emerging additive manufacturing technology that produces metallic parts with high customization. The applications of stainless steel 316L have been restricted owing to their poor tribological performance, especially in the as-printed condition. In this study, SLM-made SS 316L is subjected to laser shock peening (LSP), one of the surface modification techniques, to improve its characteristic microstructure, mechanical and wear behaviour. X-ray diffraction and residual stress analysis show that the laser shock peening promotes micro-level grain refinement and compressive residual stresses in the severely deformed layer, resulting in increased micro-hardness up to 22%. Pin on disk wear test is carried out, and the optimum condition is determined using the Taguchi method for the polished as-printed specimen. The wear rate of polished as-printed and laser shock peened specimens at optimized conditions were 2.4156 × 10−3 mm3 m−1 and 1.7871 × 10−3 mm3 m−1, respectively. The laser shock peened specimen showed higher wear resistance with a 26% reduction in wear rate compared to the polished as-printed specimens.

On the Oscillating Course of dhkl−sin2ψ Plots for Plastically Deformed, Cold-Rolled Ferritic and Duplex Stainless Steel Sheets

This work deals with non-linear dhkl−sin2ψ distributions, often observed in X-ray residual stress analysis of plastically deformed metals. Two different alloys were examined: duplex stainless steel EN 1.4362 with an austenite:ferrite volume ratio of 50:50 and ferritic stainless steel EN 1.4016. By means of an in situ experiment with high-energy synchrotron X-ray diffraction, the phase-specific lattice strain response under increasing tensile deformation was analysed continuously with a sampling rate of 0.5 Hz. From Debye–Scherrer rings of nine different lattice planes {hkl}, the dhkl−sin2ψ distributions were evaluated and the phase-specific stresses were calculated. For almost all lattice planes investigated, oscillating courses in the dhkl−sin2ψ distributions were observed, already occurring below the macro yield point and increasing in amplitude within the elasto-plastic region. By comparing the loaded and the unloaded state after deformation, the contribution of crystallographic texture and plastically induced intergranular strains to these oscillations could be separated. For the given material states, only a minor influence of crystallographic texture was observed. However, a strong dependence of the non-linearities on the respective lattice plane was found. In such cases, a stress evaluation according to the sin2ψ method leads to errors, which increase significantly if only a limited ψ range is considered.

Effect of ultrasonic surface rolling processing on wear properties of Cr12MoV steel

Ultrasonic surface rolling processing (USRP) with different rolling times (2, 6 and 10 times) was introduced to the Cr12MoV steel. The surface integrity and wear resistance after USRP were investigated. The microstructural features of the surface deformed layer were characterized by some microscopic analysis methods(scanning electron microscopy, X-ray diffraction, X-Ray residual stress analyzer and microhardness analysis). Multifunctional friction and wear testing machine was used to test the wear properties of different treated samples along the rolling direction. Results indicate that after two times of USRP, the grain of the plastic deformation layer of the material is significantly refined, moreover, the surface hardness, residual compressive stress and surface roughness were improved. However, the carbon pit produced by carbide exfoliation could not be filled in time, which becomes the source of the layered exfoliation crack and reduced the strengthening effect. With the increase of rolling times, the thickness of plastic deformation layer increased and the surface carbide decreased, which is helpful to inhibit the crack initiation and propagation, effectively improving the phenomenon of layered spalling and improve the wear resistance of material.

Cracking suppression in additive manufacturing of hard-to-weld nickel-based superalloy through layer-wise ultrasonic impact peening

Fusion-based additive manufacturing (AM) techniques that use high energy beams, such as laser and electron beam, to layer-wise fuse and form materials, are quickly becoming mainstream in the fabrication of performance-critical metal parts. However, the vast majority of alloys currently used in industry are not compatible with fusion-based AM. One major reason is the occurrence of high thermal stress and solidification cracking resulting from the far-from-equilibrium thermal history. In this research, a novel hybrid AM process that combines directed energy deposition (DED) and layer-wise ultrasonic impact peening (UIP) is used to mitigate residual stress formation and to suppress the occurrence of solidification cracking in a hard-to-weld Inconel 100 superalloy. A series of materials characterization techniques, including 3D topography, optical microscopy, electron backscattered diffraction, and X-ray residual stress analysis, is carried out to investigate the effect of layer-wise UIP on the additively manufactured products. Three levels of UIP force, i.e., 25 N, 50 N, and 75 N, are investigated. The results indicate that there is an inverse relationship between the crack density and applied UIP force. At the highest level of UIP force, the crack density reduces to near-zero with significantly improved surface quality. To successfully suppress detrimental residual stress, the depth of the peening-affected-zone (PAZ) must be larger than the heat-affect-zone (HAZ) of laser melting.

Experimental Investigation into Residual Stress in Ball End Magne-Torheological Finishing

Ball end magnetorheological finishing (BEMRF) is a novel finishing process used to finish variety of surfaces ranging from flat, curved, complex, two dimensional, three di-mensional and non linear. The residual stress and surface finish play an important role in overall efficiency and durability of the components. The present work is aimed to relieve the residual stress of work-piece surface with the improvement in surface finish using pulse DC power supply (PDCPS) in BEMRF process. The preliminary experiments have been conducted on flat EN-31 steel with and without pulse DC power supply (WPDCPS). The process parameters during experiments were considered as magnetiz-ing current (MC) of 2.5A, tool rotational speed (TRS) 500 rpm, and working gap (WG) 1.5 mm with finishing time 35 minutes and 55 mm/minute feed rate given to the work-piece. The responses such as residual stress and surface roughness have been measured before and after experimentation. Residual stress of EN-31 surface was measured with X-ray residual stress analyzer using Cosα method. It has been observed that the residual stress was found reduced from 130 to 66 MPa and surface roughness was reduced drastically wit h the use of pulse DC power supply in BEMRF process. After preliminary experi-mentation, the statistical analysis with design of experiment has been conducted with pulse DC power supply on EN-31 steel to visualize the effect of various process parame-ters on residual stress using RSM technique.

Residual stress tuned magnetic properties of thick CoMnP/Cu multilayers

Electrodeposited hard magnetic thick films have vast applications in the microelectromechanical systems (MEMS). Yet the very large residual stresses (σr) built-up in monolayered thick magnetic films leads to cracks, dimensional changes and deteriorated magnetic properties. Here, we explored quantitatively magnetic properties of CoMnP/Cu multilayers tuned by σr, which in turn are varied by the inserted soft Cu interlayer and thickness of single CoMnP magnetic layers. The configuration of the multilayers is an alternating CoMnP/Cu on Cu-substrate. The thickness of Cu interlayer was 1.4 μm. We kept a sum of all magnetic layers in the multilayers at ∼20 μm to benchmark with a 19.4 μm monolayered CoMnP. The magnetic layers are 94 wt.% Co and possess highly textured (002) hexagonal close packed microstructures. We characterized the apparent crystallite stresses through sin2ψ method by X-ray diffractometer (XRD) and residual film stress by curvature method. The insertion of Cu interlayers effectively reduces σr by 23% through stacking with six single-layered CoMnP. The out-of-plane (OP) anisotropy is slightly reduced. While the maximum energy product in the in-plane (IP) direction can be significantly enhanced by 430% ∼ 690% with increasing the number of the CoMnP single layer in the multilayers. The magneto-elastic behaviors well explain the evolution of the total anisotropy energy of the mono- and multi-layers. By CoMnP/Cu configurations we successfully worked out a strategy to preserve prestigious OP performance while to enhance IP properties by 4 to 6 times to meet ever increasing challenges in MEMS applications.

Depth-resolved X-ray residual stress analysis in PVD (Ti, Cr) N hard coatings

Abstract Physical vapour deposition (PVD) of thin hard coatings on TiN basis is usually performed at rather low temperatures (T D < 500 °C) far from thermal equilibrium, which leads to high intrinsic residual stresses in the growing film. In contrast to the extrinsic thermal residual stresses which can easily be estimated from the difference of the coefficients of thermal expansion between the substrate and the coating, a theoretical prediction of the intrinsic residual stresses is difficult, because their amount as well as their distribution within the film depend in a very complex way on the deposition kinetics. By the example of strongly fibre-textured PVD (Ti, Cr)N coatings which have been prepared under defined variation of the deposition parameters in order to adjust the residual stress distribution within the coatings, the paper compares different X-ray diffraction techniques with respect to their applicability for detecting residual stresses which are non-uniform over the coating thickness.

Finite element simulation on residual stress during immersion quenching and pre-stretching of Al7055 thick plates

During the immersion quenching process, severe temperature changes and significant temperature differences between the core and superficial area can give rise to high residual stresses within the aluminum alloy thick plate to cause subsequent machining distortion of the thin-walled part. Reducing the residual stress within the thick plate can effectively minimize the distortion in part. In this research, ABAQUS software was adopted to simulate the internal temperature and stress fields of thick plates of Al7055 alloy during the quenching and pre-stretching processes, sequentially and respectively. In addition, the x-ray residual stress measurement method was used to measure and characterize the surface residual stress of the plates. The results indicate that the medium temperature affects residual stress inside the thick plate significantly during the immersion quenching process. The level of which inside the plate gradually increases as the medium temperature decreases. Further, the pre-stretching treatment can effectively reduce residual stresses within the thick plate, and the residual stress level gradually decreases with the pre-stretching ratio increasing. The experimental results verify the feasibility of numerical simulation to predict the status of quenching stress in thick plates. Subsequently, a simulation study for material removal processes was carried out based on the above studies. The results reveal that the thin-walled part’s machining distortion degree improves as the raw thick plate’s initial quench residual stress level decreases.