Evaluation Of Residual Stresses Research Articles

In memory of V. F. Chekurin

The purpose of the research article is to study the contribution of V. F. Chekurin to the development of science through a comprehensive and objective analysis of the publications of the author, his colleagues and co-authors. In the creative heritage of V. F. Chekurin, it is proposed to single out three areas of his works: semiconductors, pipeline gas dynamics, and an elasticity problem. It is shown that set of works by V. F. Chekurin can be called Chekurin's theory of pipeline gas dynamics. It is recommended to be used for pipelines condition monitoring. Verification of numerical modeling results according to the RR criterion showed that among the tested models, the model is suitable if $RR<1$. This proves that the Chekurin–Khymko model can be registered in Data Base of Geospatial Objects. The variation method of homogeneous solutions is proposed for the evaluation of residual stresses formed in cylindrical bodies.

Sampling Moiré method for full-field deformation measurement: A brief review

The sampling Moiré (SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. In this review, the basic principle of the SM method for measuring the two-dimensional displacement and strain distributions is introduced. When the grid is not a standard orthogonal grating and cracks exist on the specimen surface, the measurement methods are also stated. Two of the most typical application examples are described in detail. One is the dynamic deflection measurement of a large-scale concrete bridge, and the other is the residual thermal strain measurement of small-scale flip chip packages. Several further development points of this method are pointed out. The SM method is expected to be used for deformation measurement of various structures and materials for residual stress evaluation, crack location prediction, and crack growth evaluation on broad scales.

Comparative Multi-Modal, Multi-Scale Residual Stress Evaluation in SLM 3D-Printed Al-Si-Mg Alloy (RS-300) Parts

SLM additive manufacturing has demonstrated great potential for aerospace applications when structural elements of individual design and/or complex shape need to be promptly supplied. 3D-printable AlSi10Mg (RS-300) alloy is widely used for the fabrication of different structures in the aerospace industry. The importance of the evaluation of residual stresses that arise as a result of the 3D-printing process’ complex thermal history is widely discussed in literature, but systematic assessment remains lacking for their magnitude, spatial distribution, and comparative analysis of different evaluation techniques. In this study, we report the results of a systematic study of residual stresses in 3D-printed double tower shaped samples using several approaches: the contour method, blind hole drilling laser speckle interferometry, X-ray diffraction, and Xe pFIB-DIC micro-ring-core milling analysis. We show that a high level of tensile and compressive residual stresses is inherited from SLM 3D-printing and retained for longer than 6 months. The stresses vary (from −80 to +180 MPa) over a significant proportion of the material yield stress (from −⅓ to ¾). All residual stress evaluation techniques considered returned comparable values of residual stresses, regardless of dramatically different dimensional scales, which ranged from millimeters for the contour method, laser speckle interferometry, and XRD down to small fractions of a mm (70 μm) for Xe pFIB-DIC ring-core drilling. The use of residual stress evaluation is discussed in the context of optimizing printing strategies to enhance mechanical performance and long-term durability.

Numerical simulation of laser-generated Rayleigh wave pulses propagation in the machined surface with residual stress using finite-difference method

Laser-excited broadband Rayleigh wave propagation behaviors can be used for characterizing material surface characteristics non-destructively. The present paper is concerned with the Rayleigh wave propagation in the machined surface with a damaged layer with residual stress. Biot’s theory of small deformations affected by initial stress forms the basis for this study. Taking ground silicon wafer as an example, we adopted a staggered finite-difference (FD) scheme for numerical simulation. By comparing the dispersion images with the theoretical dispersion curves of Rayleigh wave, the accuracy of the FD algorithm is verified. Then, some two-layer models without or with residual compressive stress are utilized to further analyze the dispersion energy characteristics of Rayleigh waves in the machined surface. The results indicate that damage layer thickness and damage degree determine the main Rayleigh wave high-order mode and the energy of the high-order mode, respectively. In addition, residual compressive stress can reduce the phase velocity of the Rayleigh wave to a small extent. Meanwhile it can significantly increase the total energy of the Rayleigh wave which excited by the same excitation source. This paper will provide a valuable reference for laser ultrasonic evaluation of residual stress on the machined surface.

Study on evaluation of through-thickness residual stresses and microstructure-mechanical property relation for dissimilar welded joint of modified 9Cr–1Mo and SS304H steel

Gas Tungsten Arc Welded dissimilar joint of modified 9Cr–1Mo (P91) and SS304H steel plate is prepared using Ni-based ERNiCrCoMo-1 super alloy filler and are post-weld heat treated (PWHT) at 760 °C for 2 h. In particular, joints are investigated for metallurgical and mechanical properties in different heat-affected zones. Furthermore, an attempt has been made to understand the following: (i) Is there any effect of mixing of Ni-based superalloy filler material on the joint? (ii) How does the PWHT process change the metallurgical and mechanical properties of joints and different sections? (iii) Does the PWHT process beneficial as compared to as-welded (AW) joint? Experimental results indicate that improper mixing of filler materials led to the formation of an unmixed zone near the weld metal and HAZ interface. The hardness, residual stress, and impact energy results confirmed the variation in mechanical properties along the weldments. The tensile strength varied from 539 MPa in as-joint to 516 MPa in PWHT, and impact energy varies from 165 J in as-joint to 40 J in PWHT condition. The maximum hardness of 375 H V is observed in P91 CGHAZ. The maximum longitudinal residual stress is estimated as 200 MPa at the top surface of the welded plate, i.e., about 2 mm depth, while the maximum magnitude of the transverse residual stresses is observed as 109 MPa at the same depth of 2 mm. In P91 HAZ, the longitudinal and transverse residual stress magnitudes are found to be in a range of 0 to ˗70 MPa. The SS304H HAZ shows the maximum value of longitudinal and transverse residual stress level at a depth of 3 mm, and it was 144 MPa and 92 MPa, respectively. The PWHT showed a drastic reduction in residual stress value in a different zone of the weldments.

An immersed boundary approach for residual stress evaluation in selective laser melting processes

In Selective Laser Melting (SLM) processes, residual stress formation can substantially affect mechanical properties and geometric accuracy of the produced part. The process parameters together with the adopted laser scan strategy should be optimized in order to reduce residual stresses in the solidified artifact. Employing traditional numerical methods, i.e., boundary-conforming mesh finite elements, can be computationally very expensive when complex geometrical features are involved, since the capability of capturing solidified part shapes depends on the element size. Immersed boundary methods present a valid alternative to effectively predict residual stresses employing a rather coarse discretization without loosing accuracy in the solidified geometry representation. In the present work, the finite cell method, an immersed boundary method, is employed to predict residual stresses using a high-fidelity thermo-mechanical model resolving the melt-pool length scale. The thermal model is first validated with respect to experimental measurements from the literature, while the mechanical results are compared to boundary-conforming mesh analysis for the same geometrical accuracy. Finally, the numerical method is applied to study the influence on residual stresses of two different laser scan strategies on a 10-layer SLM structure. The proposed immersed boundary approach can lead to a remarkable improvement in terms of computational time and memory usage when the mesh generation step is the main burden of a thermo-mechanical SLM process simulation.

Evaluation of equi-biaxial residual stress from spherical indentation imprint

A novel approach is proposed for evaluating equi-biaxial residual stresses (RS) from residual imprint displacement fields after spherical indentation. A unique region, where displacements are free from frictional effect, is first identified based on finite element analysis. Regression functions are proposed to relate imprint data with RS for a broad range of material properties. Digital image correlation (DIC) is employed for measuring the radial displacement fields. Experimental comparison of RS values from the present method and strain gauge showed the (maximum, mean) errors of only (10, 5) %. As the determined RS are accurate and reliable, the methodology can find more industrial applications compared with prior techniques.

Evaluation of residual stresses in isothermal friction stir welded 304L stainless steel plates

Friction stir welding was performed on 304L SS plates in order to heal simulated cracks created by electrical discharge machining. Two different tool temperatures (825 and 725 °C) were chosen for this study. Both neutron diffraction and X-ray diffraction techniques were employed to evaluate the residual stresses along two orthogonal reference directions, longitudinal (σyy) and transverse (σxx). The former technique was also used to measure residual stresses at various depths. It was found that, at 1 mm depth from the top surface inside the stir zone (SZ), the longitudinal component was tensile in nature while the transverse component was compressive. The nature and magnitude of the residual stress fields, and the position of the peak residual stresses were found to vary with the weld depth. The SZ of the 725 °C weld exhibited higher peak stress than 825 °C weld mainly due to a lack of stress relief at the lower temperature.

The use of surface acoustic waves to evaluate of the near-surface layers of metal processed shot peening

1. Berezhnyts'ka MP, Kyrylenko SM, Paustovskii AV. Evaluation of residual stresses in bars subjected to surface hardening. Material Science. 1997;33(6): 851-861. https://doi.org/10.1007/BF0235.... CrossRef Google Scholar

Mechanism study of the residual stress evaluation of low-carbon steels using the eddy current magnetic signature method

The eddy current magnetic signature (EC-MS) method is a relatively new method used to evaluate the residual stresses of ferromagnetic steels with higher sensitivity than other magnetic techniques. In this study, the effects of mechanical polishing and the ferrite–pearlite structure on the shape of the EC-MS signal were investigated in two experiments to clarify the effect of compressive residual stress on the EC-MS signal shape. In the first experiment, the work-hardened layers of the specimens were removed by electrolytic polishing and the EC-MS signals of the specimens were investigated. The second experiment involved the EC-MS measurements of materials with different pearlite contents, i.e., low-carbon steel with 0.17% and 0.27% carbon and pure iron. Specimens with different residual strains were prepared using a tensile test apparatus and their EC-MS signals were compared. In both experiments, the residual stresses acting on the specimens were measured adopting X-ray diffraction. The results reveal that the non-anisotropic compressive residual stress acting on the specimen surface changed the EC-MS signal in an anti-clockwise manner while the unidirectional compressive residual stress inside the specimen changed the EC-MS signal in a clockwise manner.

Research on the influence of heat treatment on residual stress of TC4 alloy produced by laser additive manufacturing based on laser ultrasonic technique

During the laser additive manufacturing (LAM) process large temperature gradients can lead to high level of residual stress. The residual stress can have irreversible effects such as warping and cracking of parts during and post manufacturing. Heat treatment is an effective method to control and eliminate residual stress. In this paper, the TC4 parts are prepared by laser additive manufacturing, and the influence of heat treatment process on residual stress is researched. Laser ultrasonic technology, as an advanced nondestructive testing method, is applied to measure the residual stress under different heat treatment processes for the first time. The surface wave generated by laser is used to evaluate the residual stress. The results show that laser ultrasonic method can complete the in-situ evaluation of residual stress in additive manufacturing components. The residual stress in TC4 deposited specimen is large, the longitudinal stress is obviously greater than the transverse stress, and the maximum residual stress is about half of the yield strength. The residual stress increases gradually from the upper surface to the bottom layer near the substrate before heat treatment. After heat treatment, the residual stress is reduced to low stress level and a small compressive stress appears. The cooling rate and solution temperature are the main factors affecting the residual stress, and the residual stress increases with the increase of cooling rate and solution temperature. The effect of aging temperature and aging time on residual stress is not obvious. The study serves as useful guidelines for engineers to assessment and regulation of residual stress reasonably in LAM.

Evaluation of Residual Stress in Die Castings of Al-Si-Cu Alloy Considering Material Composition Change in Thickness Direction

This study investigated a method for accurately predicting the residual stress in die castings manufactured using aluminum alloy. To account for the mechanical properties caused by the material composition differences that occur in the thickness direction of the die castings, a model split in the thickness direction was used in the simulation model. Norton’s law was applied to the constitutive equation of the material, and the stress relaxation phenomenon was examined. The composition of Al-Si-Cu alloy (JIS-ADC12) die castings in the thickness direction were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), and differences in composition were confirmed. As a result of calculating the residual stress using the simulation, it was possible to calculate the residual stress that could not be reproduced by the simulation model of uniform composition. This suggested that the difference in mechanical properties of die castings in the micro-region influences the residual stress.

Thin films residual stress profile evaluation using test microstructures: Illustrated on an example of AlN film

In this study, we investigate the residual stress gradient of aluminum nitride thin film deposited by reactive pulse DC magnetron sputtering technique on a 200 mm diameter silicon wafer with a 1 μm layer of plasma enhanced chemical vapor deposition tetraethylorthosilicate. Stress measurements are obtained using in situ fabricated rotational beam microstructures. The rotating beam moves in response to relief of the residual stress on the connecting arms that experience lengthening or shortening due to compressive or tensile residual stresses, respectively. Various arm-beam connecting joints, separation gaps between the arms, and arm lengths are considered to determine the optimum microstructure for localized residual stress evaluation of the sputtered aluminum nitride. The displacement of the rotating beams with four different arm-beam connecting-joint designs is analytically modeled using COMSOL multiphysics finite element method simulation. The results of the analytical model were found to be in agreement with the results observed through experiments. The stress gradient measurements obtained using the microstructures are compared to the Stoney stress evaluated using a wafer bow technique. Although the predicted Stoney stress shows a 220 MPa tensile residual stress, the observed trend in localized stress values shows that the maximum stress is 280 MPa at the center of the wafer and reduces to about 100 MPa at the edge of the wafer.

Evaluation of residual stress of c oriented AlN/Si (111) and its impact on mushroom-shaped piezoelectric resonator

Aluminium nitride-based MEMS resonators are one of the interesting recent research topics for its tremendous potential in a wide variety of applications. This paper focuses on the detrimental effect of residual stress on the AlN-based MEMS resonator design for acoustic applications. The residual stress in the sputtered c-axis (< 001 >) preferred oriented AlN layers on Si (111) substrates are studied as a function of layer thickness. The films exhibited compressive residual stresses at different thickness values: − 1050 MPa (700 nm), − 500 MPa (900 nm), and − 230 MPa (1200 nm) with ± 25 MPa accuracy. A mushroom-shaped AlN-based piezoelectric MEMS resonator structure has been designed for the different AlN layer thicknesses. The effect of the residual stresses on the mode shapes, resonant frequencies, and quality factor (Q) of the resonator structures are studied. The resonant frequency of the structures are altered from 235 kHz, 280 kHz, and 344 kHz to 65 kHz, 75 kHz and 371 kHz due to the residual stress of − 1050 MPa (thickness: 700 nm), − 500 MPa (thickness: 900 nm) and − 230 MPa (thickness: 1200 nm), respectively. At no residual stress, the quality factors of the resonator structures are 248, 227, 241 corresponding to the 700 nm, 900 nm, and 1200-nm-thick AlN layers, respectively. The presence of the residual stress reduced the Q values from 248 (thickness: 700 nm), 227 (thickness: 900 nm), 241 (thickness: 1200 nm) to 28, 53, and 261, respectively.

Evaluation of fracture toughness and residual stress in AISI 316L electron beam welds

AbstractWeld residual stress and fracture behavior of 316L electron beam weldments, which are of particular interest in power generation industry, were investigated in this work. Two butt‐weld joints were manufactured in stainless steel 316L plates of 6 mm and 25.4 mm thicknesses. Three complementary methods were used to measure the three orthogonal components of the residual stress in the weld coupons, and fracture tests were conducted on single edge notched bending specimens extracted from different regions of the welds and parent metals.The residual stress measurements showed a maximum value of 450 MPa in longitudinal direction, while it was less than 150 MPa in the other two orthogonal directions, revealing that in our material, and with the chosen weld parameters, the residual stresses were biaxial. The fracture resistance of the weldment and parent material was similar, with material microstructure differences being more significant than the measured residual stresses.The study suggests that 316L electron beam weldments are not susceptible to fracture failure due to their high ductility and ability to relieve residual stresses through gross plasticity. Electron beam welding may therefore be suggested as a reliable manufacturing technology for safety critical 316L components.

Prediction of surface residual stress in end milling with Gaussian process regression

The residual stress has an important influence on the performance of parts such as fatigue life, and many researches have been carried out for the quantitative evaluation or prediction of residual stress. However, the quantitative evaluation of residual stress achieved by the instrument will cause damage to the parts or consume a long time. Moreover, some analytical models for machining-induced residual stress prediction are quite complex with poor universality. In this research, surface residual stress under different cutting parameters and machining features were investigated. The optimal feature set and feature importance were analyzed by random forest algorithm. A new method for predicting machining-induced surface residual stress was proposed based on Gaussian process regression and other machine learning algorithms were also utilized to verify the performance of the proposed approach. The values of quantitative evaluation indicators showed that the prediction model provides a robust framework for surface residual stress prediction.

Evaluation of residual stresses in a pipe-to-plate welded joint by means of uncoupled thermal-structural simulation and experimental tests

A deep knowledge of the production process is needed, in order to achieve quality and safety requirements in a component. In this context, residual stresses play an important role, especially in welded structures. The present work deals with the assessment of residual stresses in a S355JR carbon steel pipe-to-plate welded joint. Both numerical simulations and experimental tests were employed in order to gain wide-ranging knowledge. Numerical simulations were performed with the software Ansys© through an uncoupled (one-way coupling) thermal-structural simulation in order to evaluate the stress, strain and temperature at each node of the finite element model for each phase of the simulation. Temperature-dependent elastic-plastic material properties were adopted in combination with the element birth & death method, necessary to simulate the welding process. Two numerical weld seam solidification methods were employed and discussed, in terms of expected results and simulation performances. The obtained numerical results were compared with experimental data of relaxed radial strains measured nearby the weld seam.

In Situ Monitoring of Additive Manufacturing Using Digital Image Correlation: A Review.

This paper is a critical review of in situ full-field measurements provided by digital image correlation (DIC) for inspecting and enhancing additive manufacturing (AM) processes. The principle of DIC is firstly recalled and its applicability during different AM processes systematically addressed. Relevant customisations of DIC in AM processes are highlighted regarding optical system, lighting and speckled pattern procedures. A perspective is given in view of the impact of in situ monitoring regarding AM processes based on target subjects concerning defect characterisation, evaluation of residual stresses, geometric distortions, strain measurements, numerical modelling validation and material characterisation. Finally, a case study on in situ measurements with DIC for wire and arc additive manufacturing (WAAM) is presented emphasizing opportunities, challenges and solutions.

Coupled Eulerian–Lagrangian prediction of thermal and residual stress environments in dissimilar friction stir welding of aluminum alloys

The evaluation of residual stresses (RS) induced by the friction stir welding (FSW) process is crucial in anticipating the performance of the welded structure. The existence of such residual stresses within a friction stir welded structure may lead to excessive distortion and weakness to afford the applied external loads. To assess quantitatively the effect of these residual stresses generated by FSW process, the current paper implements a Coupled Eulerian–Lagrangian (CEL) finite element simulation to analyze both thermal and subsequent resulted remaining stress environments in dissimilar friction stir welding of AA6061-T6 and AA2024-T3 alloys. The thermal analysis step was conducted first and followed by a mechanical analysis step in which the residual stresses distribution throughout the whole dissimilar FSWed alloys were captured. To validate the simulation results, K-type thermocouples, in addition to A-type rosette strain gauges, were planted to measure both temperature history and residual stress field generated as a consequence of the thermal environment. The effect of changing FSW working variables like rotation and traverse speeds on both the thermal and residual stress environments was investigated. The obtained results demonstrated that the temperature, as well as the residual stress, was higher in the sample retreating side rather than the proposed advancing side, and a fair correlation between the experimental and simulation results was attained. Quantitatively, the longitudinal residual stress was higher in contrast to the transverse value, and it varied from being tensile in the zone beneath the tool shoulder to compressive away from the welding tool. Furthermore, the plastic strain produced owing to the surface contact between the welding tool and the dissimilar aluminum sample was higher on the retreating side.

The Effects of Shot Distance and Impact Sequence on the Residual Stress Field in Shot Peening Finite Element Model

In order to investigate the effect of shot distance and impact sequence on the residual stress distribution of 42CrMo steel in shot peening (SP) finite element (FE) simulation, 3D dynamic models with order dimple pattern and stochastic dimple pattern were established via ABAQUS/Explicit 6.14, and the simulation results were compared with experiments. The results show that shot overlap has a significant effect on the residual stress distribution of peened parts. Meanwhile, there is a threshold (related to SP parameter) for shot distance in the vertical and horizontal directions. When the shot distance is greater than the threshold in this direction, the residual stress distribution after SP tends to be stable. The impact sequence has almost no effect on the impact of a small number of shots, but this effect will appear when the number of shots increases. It is necessary to avoid shot overlap and continuous impact of adjacent dimples when the FE model is established; on this basis, the distance between shots and the number of layers of the shots can be reduced as much as possible without affecting the residual stress distribution. In addition, the comparison of simulation and experimental results shows that the residual stress evaluation area consistent with the experimental measurement is essential to obtain accurate residual stress distribution in the FE simulation process.