Residual Stress Measurements Research Articles

Micromechanical models and experiments for diffractive elastic constants of TATB-based polymer-bonded explosives

TATB-based polymer-bonded explosives (PBXs) exhibit intricate internal stress distributions due to crystal anisotropy. When diffraction techniques are employed to measure these internal residual stresses, it is critical to identify the discrepancy between the diffraction elastic constants (DEC) of particular crystal planes of a TATB-based PBX and the macroscopic elastic constant of the PBX. This study introduced various micromechanical models to describe the mechanical behavior of TATB-based PBXs, as well as assessing their accuracy in predicting the elastic properties of the PBXs and calculating the DECs of different crystal planes. Using in situ tensile experiments, this study obtained accurate DECs of the crystal plane of TATB-based PBXs and revised the residual stress measurements of the PBXs. The comparison between experimental results indicates that the two-phase and double-inclusion micromechanical models proposed in this study exhibit higher precision in predicting both the quasi-static mechanical properties of the PBXs and the DECs of the crystal plane. Furthermore, the DECs of the PBXs with high volume fractions of TATB are close to those of pure TATB crystals. Based on the established double-inclusion model, it can be inferred that the DECs of different crystal planes vary as a function of the TATB volume fraction. This study lays the foundation for profound analyses of the mechanical characteristics of TATB-based PBXs using diffraction techniques.

Effect of peening treatment on fatigue strength of welded joints of aged steel

This study experimentally investigates the effect of peening treatment on the fatigue strength of welded joints of aged steel. Fatigue tests were conducted on T-shaped fillet welded joints made from three different types of aged steel under three-point bending loading conditions. To reveal fatigue strength improvement mechanism, residual stress measurement, hardness measurement, and metallographic analysis were performed at the weld toe for both as-weld and peened specimens. Fractured surfaces were examined to identify crack initiation sites and propagation. The findings reveal that peening treatment introduces compressive residual stress on the peened surface of welded joints of aged steel equal to or higher than conventional steel welded joints. Higher improvement of hardness was observed in the near surface of the peened welded joints of aged steel, and the improvement continued up to around the zero crossing points of the residual stress distribution. Additionally, peening treatment might refine near-surface grains of aged steel welded toe similar to conventional steel. The fatigue strength improvement effect of the peening treatment was the same for aged steel as conventional one. Cracks were observed on the peened surface of the aged steel due to over-peening treatment. However, it doesn't affect the fatigue strength improvement of the welded joints of aged steel. In summary, it can be said that peening treatment can improve fatigue strength of welded joints of aged steel in the same manner of conventional steel.

Flexural behaviour of Q1100 ultra high strength steel welded I-sections

An experimental and numerical program investigating the in-plane flexural behaviour of Q1100 ultra high strength steel (UHSS) welded I-sections is presented in the current paper. The testing program comprised of material coupon tests, measurements of residual stresses, and in-plane 3-point bending tests. Subsequently, a numerical program was executed, involving the development of finite element (FE) models. The FE models validated against the experiments were subsequently employed for parametric studies, aiming at assessing the flexural behaviour of Q1100 welded I-sections across a broader spectrum of section geometries. The data obtained from the experiments and numerical simulations were used to assess the applicability of prevailing design provisions outlined in the European, Chinese and Australian codes for high-strength steel structures. These design provisions encompass classification limits for cross-sections and predicted methods for cross-sectional resistance in bending. Via reliability analyses, adjustments were made to the cross-section classification limits. Finally, a modified direct strength method was proposed to predict the in-plane bending resistance for Q1100 welded I-sections.

Influence of turning parameters on residual stresses and roughness of 42CrMo4 + QT

Residual stresses and surface roughness have been recognized to play a critical role in the fatigue strength of metal components. Machining processes can induce different roughness and residual stress conditions depending on the parameters used in the process. Therefore, it is essential to develop knowledge that helps to predict the residual stresses and roughness that would be obtained from different machining conditions. Due to the growing interest from the industry in the use of 42CrMo4 steel because of its excellent mechanical properties, the main objective of this work is to establish two phenomenological models to accurately predict the residual stress and roughness values in turned specimens of this material. The models are derived from data of four process variables: (a) insert tip radius; (b) feed rate; (c) cutting speed; and (d) depth of cut. For this purpose, a wide experimental campaign has been developed, which includes the machining of 68 specimens under various cutting scenarios, and their subsequent measurement of residual stresses and roughness. Once the experimental data were obtained, the response surface method based on the central composite design was used to fit the models, obtaining a correlation index R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document} higher than 0.9 in both cases. In this article, it is concluded that feed rate and insert radius have a greater effect on the residual stress and roughness obtained, while cutting speed and depth of cut have a lesser impact on the results. It is hoped that the findings will establish a groundwork for the machining of this material type, ensuring controlled conditions of residual stress and roughness.

Microstructural analysis and mechanical characterization of dissimilar welds between nickel-based and steel-based superalloys post-cryogenic treatment using hotwire GTAW

This study explores the dissimilar welding of nickel superalloy 59 with Fe-Ni superalloy 904 L using the Gas Tungsten Arc Welding with Hot Wire technique (HW-GTAW). The HW-GTAW process produced defect-free weldments with complete penetration, as confirmed by macroscopic analysis. Microstructural analysis using FESEM and EDS revealed fine equiaxed and columnar dendrites in the fusion zone and identified a secondary phase enriched with chromium. XRD analysis supported the presence of predominant austenitic phases and indicated the formation of Cr23C6-type carbide. The grain size of the weld joint, determined using the Gaussian method and Scherer formula, was 44.53 nm, slightly smaller than base metals. Microhardness tests revealed values ranging from 226 ± 5 HV 10 to 243 ± 5 HV 10, with the highest values observed in the deep cryogenic treatment (DCT). The Mo in the ERNiCrMo-13 filler and the effects of DCT, which promote grain refinement, are responsible for this increase in hardness. Residual stress measurements revealed a maximum tensile stress of 315 MPa along the longitudinal axis and a maximum compressive stress of 355 MPa along the transverse axis. DCT enhanced the weldment’s tensile strength by up to 12% compared to as-welded samples, with a 6% increase compared to shallow cryogenic-treated (SCT) samples. Charpy impact testing indicated a value of 88 J in the fusion zone, which is 1.2% less than alloy 59 and 9% higher than 904 L. Tensile fracture analysis revealed ductile dimples, while impact fractography showed a mix of ductile dimples and brittle, glassy cleavage facets.

Unraveling Changes of Brachial Artery Residual Stress and Its Relationship to Cardiovascular Disease Risk Factors.

Arterial pressure volume index (API) offers a non-invasive measurement of brachial artery residual stress. This study investigated API distribution characteristics and correlations with cardiovascular disease risk (CVD) factors in a large Chinese population sample. This cross-sectional study surveyed a total of 7620 participants. We analyzed the relationships between API and factors influencing CVD, using regression-based stepwise backward selection and restrictive cubic spline models to express relationships as standardized beta values. Multiple linear regression analysis identified many independent factors influencing API including age, sex, body mass index (BMI), pulse pressure (PP), heart rate (HR), hemoglobin, uric acid (UA), estimated glomerular filtration rate (eGFR), triglyceride (TC), and a history of hypertension. Notably, API values increased at 33 and escalated with advancing age. Increases in API were associated with rises in PP and UA increases, particularly when PP reached 60 mmHg and the UA reached 525 units. Conversely, API was found to decrease with elevated HR and eGFR. Furthermore, there was a significant inverted U-shaped relationship between API and BMI. This study was the first to describe API distribution characteristics in a large sample of the Chinese population, providing references for evaluating API changes in the assessment of residual stress variations in diverse diseases. Notably, API displayed a U-shaped relationship with age and was closely related to traditional CVD risk factors, underscoring its potential as a non-invasive tool for risk assessment in vascular health. This research was registered with the China Clinical Trial Registration Center (Registration Number: ChiCTR2000035937).

Eliminating eccentricity error in measuring residual stresses via hole-drilling method using strain gauge rosette with five measuring grids: For thin plates using through-holes

In the measurement of residual stresses (RSs) via the hole-drilling method, the error induced by the eccentricity of the drilled hole is inevitable and non-negligible in some cases. In this study, both the eccentricity coordinates and RS state (two principal stresses and one principal angle) are considered unknowns that must be solved. A set of five equations is required to determine these five unknowns. Therefore, two additional measuring grids are added to the strain gauge comprising three grids, which is typically used in measuring RSs. Consequently, a novel strain gauge rosette with five measuring grids (SGR-5MG) is created. Subsequently, an algorithm associated with the SGR-5MG is developed to solve the five unknowns based on the Newton–Raphson method. The algorithm is elasticity-based and derived according to the layout of the SGR-5MG. Finally, the proposed method is verified numerically and experimentally. The results show that (1) the eccentricity error is up to 35.1% when the eccentricity reaches 0.05 D, where D represents the diameter of the gauge circle; (2) Using the proposed method, the error can be significantly reduced to 7.2%; (3) The elasticity-based proposed method cannot make the predicted results exactly converge to the actual stresses in predicting high stresses because of the plasticity deformation around the hole. The eccentricity error can be reduced significantly by using the proposed method based on the SGR-5MG.

Surface residual stress in H-section steel beams processed by quenching and self-tempering using instrumented indentation testing

Using instrumented indentation testing, we explore the measurement of surface residual stress in H-section steel beams produced through the quenching and self-tempering (QST) process. We establish a significant correlation between the plastic pile-up behavior observed during indentation and the magnitude of surface residual stress. We thoroughly clarify the distribution of plastic pile-up and residual stress, linking their variations to non-uniform phase transformation and changes in mechanical properties resulting from the QST process. Moreover, we employ an indentation curve analysis to evaluate surface residual stress, obviating the need for direct measurements of pile-up height. These findings facilitate the measurement of non-uniform surface residual stress in H-section beams, crucial for ensuring structural integrity, yet challenging to measure in situ.

Influence of Rebar Strength, Pre-treatment, and Measurement Method on Residual Stress Measurement using Portable X-ray Diffractometer

Influence of Rebar Strength, Pre-treatment, and Measurement Method on Residual Stress Measurement using Portable X-ray Diffractometer

Experimental study on the effect of reaming on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components

The split-sleeve cold expansion technique has been widely used in the aerospace industry to improve the fatigue life of metal components with holes. Due to the morphology change after the expansion, a reaming process is necessary to improve the machining accuracy of the hole surface. This final reaming process might change the residual stress distribution around the hole significantly but the effect of the reaming ratio has not been fully explored. This paper investigated the effect of reaming depth on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components using a series of experiments, including the residual stress measurements, uniaxial fatigue tests, and fracture morphology observations. The expectations of the fatigue cycles were estimated using the 2-parameter Weibull distribution and the S-N curves of different components were acquired. Residual stress measuring results and the fracture surface observations explained the effect of cold expansion and reaming on the components. The experimental results showed that the fatigue life of the components decreased with the increase of the reaming ratio, demonstrating that excessive reaming depth is harmful to the fatigue performance of the cold-expanded components.

Machine Learning Augmentation of the Failure Assessment Diagram Methodology for Enhanced Tubular Structures Integrity Evaluation

Failure assessment diagrams (FADs) are essential engineering tools for evaluating the structural integrity of components. However, their widespread application can be limited by complexity and computational expense. This study presents a novel machine learning-based approach to streamline FAD analysis, offering accuracy and efficiency while overcoming these limitations. The approach integrates numerical contour integral-based FADs with artificial neural networks (ANNs). To ensure reliable material modeling for the Finite Element Analysis (FEA) used to generate J-integral based FADs that train the ANNs, careful experimental and numerical procedures were employed. This involved uniaxial tensile tests, an iterative method for obtaining precise true stress–strain curves, and a Ramberg–Osgood material model for accurate material behavior representation. The ANNs themselves not only analyze large datasets to generate precise FAD envelopes but also predict limit loads and the Φ parameter, incorporating the effect of residual stress on the FAD methodology. To verify and test the proposed method, hypothetical fitness-for-service assessment cases were conducted, incorporating experimental residual stress measurements from split-ring tests on P110 and L80 pipes. These assessments were compared to both traditional FAD methods and computationally intensive FEA-based FADs. Results demonstrate a closer agreement with FEA-based calculations than traditional methods provided in engineering standards. Ultimately, this work provides a rather innovative and adaptable approach for structural integrity evaluations and critical engineering assessments through the proposal of an ANN enhanced FAD approach, simplifying these calculations while maintaining high fidelity.

Iterative Stress Reconstruction Algorithm to Estimate Three-Dimensional Residual Stress Fields in Manufactured Components

Abstract Residual stress (RS) significantly impacts the mechanical performance of components. Measurement of RS often provides incomplete data in terms of components of stress and spatial density. Employing such fields in finite element simulations results in significant modification of the field to achieve equilibrium and compatibility among strains. To overcome this, an iterative stress reconstruction algorithm (ISRA) is developed to estimate 3D RS fields that satisfy equilibrium, are stress component-wise complete, and represent the characterized data sampled. An Al 7075-T651 plate and an additively manufactured (AM) A36 steel wall are considered for RS reconstruction using measurement data from the literature. A maximum variation of ∼2.5 MPa in the Al plate, and ∼10 MPa in the steel wall are observed between the reconstructed and measured stresses. Furthermore, unknown stress components emerge and reach significant magnitudes (upto ∼2.3 MPa in the Al plate and ∼45 MPa in the AM wall) during ISRA. Indeed, it is found that minor errors in measurement or data processing are eliminated through the physical requirements during ISRA. Employing a reconstructed RS field is hence not just more accurate given its compatibility, but it additionally corrects for minor errors in measurement. Furthermore, it is found that spatially dense measurement data result in convergence with fewer iterations. Finally, although ISRA yields a nonunique solution dependent on boundary conditions, measurement errors, fitting errors, and mesh density, it accommodates for uncertainties and inaccuracies in measurement, as opposed to failing to reach a physically realistic converged solution.

Interpass temperature strategies for compressive residual stresses in cladding low-transformation-temperature material 16Cr8Ni via wire arc additive manufacturing

Low-transformation-temperature (LTT) materials induce compressive residual stresses within an effective depth in wire arc additive manufacturing (WAAM), which is well suited for cladding applications. However, this role was found to be sensitive to the phase transformation sequence. We developed an LTT material—16Cr8Ni (16Cr8Ni-LTT)—and to explore its potential, it was clad onto a KA36 substrate via WAAM. Three different interpass temperature strategies were designed as follows: (1) no interpass temperature control; (2) interpass temperature controlled at approximately 270 °C above the martensite transformation start temperature (Ms = 200 °C) for simultaneous phase transformation; and (3) interpass temperature controlled at approximately 50 °C below the martensite transformation finish temperature (Mf = 60 °C) for sequential phase transformation. A thermal elastic-plastic numerical model considering the phase transformation-induced plasticity (TRIP) was developed using in-house software, JWRAIN-Hybrid, to reproduce the temperature field and residual stresses of 16Cr8Ni-LTT cladding. X-ray diffraction (XRD) and contour methods were employed for residual stress measurements. The high accuracy of the model was validated in terms of the temperature, deformation, and residual stress. The reproduced maximum historical temperature distributions were combined with hardness tests to identify the depths and temperatures of the heat-affected zone (HAZ). The measured maximum compressive residual stresses induced by the three interpass temperature strategies for cladding 16Cr8Ni-LTT were −503, −420, and −720 MPa. Moreover, irrespective of the adopted interpass temperature strategy, both longitudinal and transverse residual stresses were compressive in the 16Cr8Ni-LTT cladding. This study provides scientific insights into LLT-induced compressive residual stresses and highlights the superiority and flexibility of cladding LTT materials via WAAM for improving the resistance of large metal components to fatigue and corrosion.

Non-Destructive Hardness Indentation Measurement of Residual Stress on Large Aerospace Forged Components at the Engineering Site Based on Impact Hardness Tester.

Large forgings are crucial in aerospace applications; however, the residual stresses generated during their forming and heat treatment seriously affect their serviceability. Therefore, the non-destructive detection of residual stresses in large forgings is of far-reaching significance for ensuring the quality of forgings and realising precision machining. Although a variety of detection methods are available, there is still a lack of a programme that can comprehensively, accurately and non-destructively measure the residual stresses in large forgings. This study is dedicated to exploring the application of the bouncing impact indentation method in the non-destructive testing of residual stresses in large forgings. Through in-depth finite element simulations and orthogonal scheme analyses, we found that the elastic modulus, yield strength and work hardening indexes have significant effects on the impact indentation process. Further, we establish the dimensionless function of residual stress and indentation parameters, and successfully obtain the inversion algorithm of residual stress. The relative error of the calculated values of the indentation curves hm and hr in the simulation with reference values is not more than 3%, and the relative error of the corrected Pm inversion values for most virtual materials is not more than 5%. The folding elastic modulus and apparent elastic modulus obtained by inversion are controlled within 10%, which demonstrates a high value for engineering applications. In addition, we innovatively express the research results in the form of 3D stress diagrams, realising the digital expression of 3D residual stresses in large forgings based on feature point measurements and contour surface configurations, which provides intuitive and comprehensive data support for engineering practice.

Effect of micromorphology on measurement of residual stress of ground silicon wafers using Raman spectroscopy

Effect of micromorphology on measurement of residual stress of ground silicon wafers using Raman spectroscopy

Development of accurate contour residual stress measurement technique for sustainable structural integrity assessment in additive manufacturing

Abstract Accurate analysis of residual stress present within an engineering component plays a fundamental role to its sustainable structural integrity assessment. This is particularly important for a safety critical component within the power generation sectors, aerospace, and oil and gas industries. The accurate stress analysis not only allows operators to determine the life remaining in a component but also avoid over-conservative estimates and thereby contribute to life extension of engineering plants and components. By utilizing and unifying multiple residual stress analysis tools of different nature a robust and more accurate method of stress analysis is achieved. The main aim of the current study focusses on the development and optimization of a robust residual stress tool based on the contour technique to accurately analyse inherent stress in an engineering component.

Residual Stress Measurement of Laser Powder Bed Fusion Additively Manufactured Hastelloy-X Through Crystal Plasticity Simulations and Neutron Diffraction Experiments

Residual Stress Measurement of Laser Powder Bed Fusion Additively Manufactured Hastelloy-X Through Crystal Plasticity Simulations and Neutron Diffraction Experiments

Tensile Coupon Testing and Residual Stress Measurements of High-Strength Steel Built-Up I-Shaped Sections

High strength structural steels (with yield stresses greater than 65 ksi) may have notably different material characteristics when compared to structural steels conventionally used in building construction [i.e., ASTM A992/A992M (2022) or A572/A572M Gr. 50 (2021)]. This paper presents findings from an experimental program that investigated the material characterization of ASTM A656/A656M Gr. 80 (2024) plate steel. The results obtained were compared to conventional ASTM A572/A572M Gr. 50 steel. Two types of testing were performed for this work: tensile coupon testing and residual stress testing. The tensile coupon testing was carried out for both the A656/A656M Gr. 80 and A572/A572M Gr. 50 plate material. The A656/A656M Gr. 80 plate material showed more variation between the two different plate thicknesses in both mechanical behavior and microstructure due to differences in steel production. The 0.375 in. thick plate exhibited a clear yield plateau with an ultimate/yield stress ratio similar to the Gr. 50 material. In contrast, the 0.5 in. plate did not have a yield plateau and reached lower ultimate strain. The residual stress testing was performed using a sectioning technique for one A572/A572M Gr. 50 and five A656/A656M Gr. 80 built-up sections that were fabricated from 0.5 in. and 0.375 in. plate material. Residual stresses obtained from measurements were compared to previously published predictive models. The ECCS model and BSK99 models were found to be reasonable predictors of residual stresses for all specimens except the one section fabricated from 0.5 in. thick Gr. 80 plate. When comparing the Gr. 50 and Gr. 80 specimens of the same cross-sectional geometry, the residual stresses were similar, implying that cross-sectional geometry is more prevalent than the nominal yield stress in determining residual stresses in built-up I-sections.

Experimental study on compressive capacity of stainless steel S35657 columns with welded box section and I-section under axial compression

Compared with conventional stainless steel, a new type of stainless steel, S35657, has broad application prospects owing to its advantages of high strength and low production costs. In this study, the compressive capacity of stainless steel S35657 columns was investigated. A total of 13 specimens were designed and tested, including 4 box section specimens and 9 I-section specimens (4 buckling around the major axis and 5 buckling around the minor axis). Complementary chemical composition analyses, material tensile tests, residual stress measurements, and initial geometric imperfection measurements were also conducted. The mechanical properties of the material, as well as its residual stress distribution model, failure mode, load-displacement curve, and compressive capacity, were reported and analyzed. For box section columns, when the slenderness ratio increased from 29 to 55.2, the compressive capacity of the column decreased by 27.6 %. The accuracy and safety of design methods specified in European standard EN 1993–1–4, American specification ASCE-8–02, and Chinese specification CECS 410 were assessed based on the test results. The result shows that EN 1993–1–4 is overly conservative in its compressive capacity calculations, whereas ASCE-8–02 overestimates the compressive capacity with a higher level of scatter exhibited. The methods of CECS 410 for predicting the compressive capacity of welded stainless steel S35657 columns are more accurate compared with the methods of EN 1993–1–4 and ASCE-8–02.

Fatigue Strength Assessment of Friction Welds under Consideration of Residual Stress.

A reliable local-fatigue assessment approach for rotary friction-welded components does not yet exist. The scope of this paper is to present test results for the fatigue behaviour of rotary friction-welded solid shafts made of structural steel S355J2G3 (1.0570) and an approach to fatigue assessment considering residual stress. In contrast to fusion-welded joints, components made by rotary friction welding usually contain compressive residual stress near the weld, which can significantly affect the fatigue strength. For this purpose, specimens were welded and characterised, including metallographic micrographs, hardness measurements, and residual stress measurements. The fatigue tests were performed with a constant amplitude loading in tension/compression or torsion with R = -1. All specimens were investigated without machining of the weld flash, either in the as-welded state or after a post-weld stress-relief heat treatment. In addition, the friction welding process and the residual stress formation were analysed using numerical simulation. The characterisation results are integrated into a fatigue assessment approach. Overall, the specimens perform comparatively well in the fatigue tests and the experimentally observed fatigue behaviour is well described using the proposed local approaches.