Estimation Of Residual Stresses Research Articles

Stress-induced warpage estimation of advanced semiconductor copper interconnect processes

The growth of the semiconductor industry is driven by the demand for electronic products and high transistor density. However, complex manufacturing processes generate residual stress and result in wafer warpage. Therefore, mastering wafer warpage has become a crucial challenge. This study proposes a process-oriented simulation methodology with simulation-based equivalent material method to overcome the difficulty of finite element modeling and the substantial amount of computation time. Three different methodologies, including volume percentage, representative volume element, and Timoshenko bi-material approach, are discussed due to the estimation of residual stress for equivalent material. In addition, each methodology is validated through process-oriented simulations and comparison with measurement data. The Timoshenko bi-material approach is efficient in predicting warpage in the back end of line (BEOL) interconnects and provides a comprehensive understanding of the warpage variation that occurs during different stages of BEOL.

An efficient and quantitative approach for fracture toughness measurement of Micron-Thick hard coatings based on crack spacing

Micron-thick hard coatings find widespread applications, with fracture toughness being a crucial property that ensures their usability. However, measuring the fracture toughness of hard coatings is time-consuming and costly due to the susceptibility to cracking and small sample size. Thus, developing a simple, effective and precise measurement method is necessary. This work presents an analytical model that calculates KC from crack spacing induced by uniaxial tension. By measuring the variation of crack spacing, this model determines the fracture toughness from the energy difference during the coating fracture, and residual stress can also be estimated. This simple method overcomes the limitations of uniaxial tension methods, does not require any in-situ observations, and offers low-cost and user-friendly testing. The KC of TiN coatings with 2 μm thickness were tested and found to match the micro-cantilever beam test results from the literature. This model used data from other literature to calculate the toughness of diamond and a-C:H thin coatings, showing its generality. Additionally, our model’s estimation of residual stress in coatings, as reported in the literature, is accurate to within 0.1 ∼ 1 GPa.

Residual Stress Estimation Using Hole Drilling and Contour Methods in Rail Welds Treated with and without Ultrasonic Impact Treatment

Residual Stress Estimation Using Hole Drilling and Contour Methods in Rail Welds Treated with and without Ultrasonic Impact Treatment

Ultrasonic immersion testing of residual stress in plates using collinear Lamb wave mixing technique

Nondestructive estimation of residual stresses has been a major challenge in engineering. Herein, the collinear Lamb wave mixing method is proposed for residual stress measurement in metal plates under immersion ultrasonic testing. Numerical simulations have been conducted to investigate the influences of excitation parameters on the performance of the wave mixing method. The results showed that the receiver position and cycle numbers of primary waves affect the amplitude of the method, and optimal excitation parameters recommended. Ultrasonic immersion experiments are conducted on two types of plate-like specimens using the collinear Lamb wave mixing method. Experimental results showed that the proposed method is effective for measuring the residual stress in metal plates. The immersion ultrasonic testing can significantly reduce the influence of inconsistent coupling conditions between the transmitters and the specimen on experimental results, therefore it is more reliable than conventional contact testing.

Estimation of residual stress in dissimilar metals welding using deep fuzzy neural networks with rule-dropout

Welding processes are used to connect several components in nuclear power plants. These welding processes can induce residual stress in welding joints, which has been identified as a significant factor in primary water stress corrosion cracking. Consequently, the assessment of welding residual stress plays a crucial role in determining the structural integrity of welded joints. In this study, a deep fuzzy neural networks (DFNN) with a rule-dropout method, which is an artificial intelligence (AI) method, was used to predict the residual stress of dissimilar metal welding. ABAQUS, a finite element analysis program, was used as the data collection tool to develop the AI model, and 6300 data instances were collected under 150 analysis conditions. A rule-dropout method and genetic algorithm were used to optimize the estimation performance of the DFNN model. DFNN with the rule-dropout model was compared to a deep neural network method, known as a general deep learning method, to evaluate the estimation performance of DFNN. In addition, a fuzzy neural network method and a cascaded support vector regression method conducted in previous studies were compared. Consequently, the estimation performance of the DFNN with the rule-dropout model was better than those of the comparison methods. The welding residual stress estimation results of this study are expected to contribute to the evaluation of the structural integrity of welded joints.

Estimation of Residual Compressive Stresses in Deformed U8 Steels with Coarse-Plate Perlite by Field Dependences of Magnetic Permeability

Estimation of Residual Compressive Stresses in Deformed U8 Steels with Coarse-Plate Perlite by Field Dependences of Magnetic Permeability

Flank fractures on spiral bevel gears—transfer of analytical methods for the estimation of residual stresses from cylindrical gears to bevel gears

The classic flank and root load capacity calculation on the component surface forms the basis for the design of power gears today. However, flank fractures also occur in practice, particularly with large-module gears and/or low case-hardening depths. It is a fatigue damage with crack initiation in the tooth interior, its prevention requires the calculation of the stresses below the surface. In addition to understanding the load stresses, the inhomogeneous load bearing capacity and the residual stress profile in case-hardened gears are also of great importance. There are various calculation approaches for this in the area of cylindrical gears, but these have not yet been transferred to the complex geometry of spiral bevel gears. The focus of this publication is on estimating the residual stresses in the tooth volume by generating a three-dimensional residual stress tensor field in the bevel gear tooth based on the two-dimensional calculation approaches used to date on cylindrical gears. In combination with the stress tensor-time curves from a tooth contact simulation with the LTCA tool BECAL, this can be fed into different failure hypotheses, which is illustrated using an example.

A method for rapid estimation of residual stresses in metal samples produced by additive manufacturing

The mechanical methods for measuring residual stresses typically rely on so-called destructive techniques where some stress components can be determined based on part deflection after material removal (cutting, etching, drilling, etc.). While these methods don't provide a comprehensive representation of residual stresses within the entire part, they can be readily applied in most manufacturing labs. In this study, we propose an efficient method for determining residual stress within additively manufactured cylindrical samples of stainless steel. The method is based on the assumption of a relation between the axial component of residual stress (normal to cross-section) and the cylinder radius. The general form of this relation is proposed based on data from numerical simulations using linear, parabolic or piecewise approximations. The parameters for the proposed relation are defined using equilibrium equations for total force and moment. The proposed method relies on an experiment with a mechanical cut along the cylinder. Consequently, the deflection of the cylinder halves after the cut allows for obtaining the equivalent bending moment.

In-Process Machining Distortion Prediction Method Based on Bulk Residual Stresses Estimation from Reduced Layer Removal

Manufacturing structural monolithic components for the aerospace market often involves machining distortion, which entails high costs and material and energy waste in industry. Despite the development of distortion calculation and avoidance tools, this issue remains unsolved due to the difficulties in accurately and economically measuring the residual stresses of the machining blanks. In the last years, the on-machine layer removal method has shown its potential for industrial implementation, offering the possibility to obtain final components from blanks with measured residual stresses. However, this measuring method requires too long an implementation time to be used in-process as part of the manufacturing chains. In this sense, the objective of this paper is to provide a machining distortion prediction method based on bulk residual stress estimation and hybrid modelling. The bulk residual stresses estimation is performed using reduced layer removal measurements. Considering bulk residual stress data and machining-induced residual stress data, as well as geometry and material data, real-part distortion calculations can be performed. For this, a hybrid model based on the combination of an analytical formulation and finite element modelling is employed, which enables us to perform fast and accurate calculations. With the developments here presented, the machining distortion can be predicted, and its uncertainty range can be calculated, in a simple and fast way. The accuracy and practicality of these developments are evaluated by comparison with the experimental results, showing the capability of the proposed solution in providing distortion predictions with errors lower than 10% in comparison with the experimental results.

Estimation of residual stress in the rolled joint and its effect on its pull-out strength at different temperatures

The rolled joint between pressure tube and end-fitting in a pressurized heavy water type reactor is critical from integrity and performance point of view as significant magnitudes of residual stresses are generated during the rolling process. The distribution of residual stress in the rolled joint is required for assessment of operational performance and integrity of the same. The 3D FE simulation of the rolling process considering material, geometric and contact nonlinearities are very scarce in literature. Moreover, the discussion regarding development of residual stress in the joint during the rolling process and its subsequent relaxation at higher temperatures and corresponding data are not available in literature. The pull-out strength of the rolled join is an important operational parameter which ensures a leak tightness (due to presence of compressive contact stresses) and other functional requirements of the joint. The strength of the joint also changes significantly with temperature due to change in material properties and release of residual stresses. Especially at the severe accident regime, the strength may reduce to such as extent that the tube may get disassembled from the end-fitting due to joint pull-out. The objective of this work is to evaluate the residual stresses that are present in the joint during the rolling process and also estimate the pull-out strength of the joint at different temperatures using finite element analysis. These results shall be useful to the engineers involved in study of severe accident in Indian pressurized heavy water reactors.

A study on residual stress measurement by DIC approach in FSW welded AA6082 joints

Aluminum Alloy is extensively used in aerospace and automotive industry due to its light weight and high strength properties. It is generally joined using Friction Stir Welding, which is a solid-state process. During this process residual stresses are developed in the welded region. It is a critical factor affecting the performance and lifespan of welded parts. Accurate measurement of residual stress is very important for ensuring the structural integrity of welded components. The conventional blind hole drilling method for residual stress estimation using the strain rosette, results error in the strain data capturing and compensating it is a challenging task. The omission of strain rosette is possible using the recently developed Digital Image Correlation in conjunction with Blind Hole Drilling. This paper focuses on the feasibility study of DIC in residual stress measurement. To accomplish this, Aluminum alloy AA6082 friction stir welded butt-joints are prepared. The residual stresses were measured at the top side of the weld joint using the DIC-BHD approach. At the weld top position, the transverse residual stress of -100 MPa approx. and the longitudinal residual stress of 118 MPa approx. were estimated.

Estimation of Hardness and Residual Stress on End-Milled Surfaces Using Linear Regression Model

This study presents a novel method for estimating the surface integrity of end-milled workpieces. It is well known that the mechanical properties of machined surfaces in cutting affect the quality of the final product. In particular, hardness and residual stress often require strict control; however, nondestructive inspection remains a challenge. This study proposes a method to estimate the hardness and residual stress of end-milled surfaces by analyzing cutting forces and images of the tool during machining to obtain approximate temperature and stress distributions. These state quantities are highly correlated with the dislocation density and its distribution on the machined surface, which in turn is strongly correlated with residual stress and surface hardness. Despite this strong correlation, few research studies have been conducted on the topic. In the proposed method, cutting forces, measured by a dynamometer, are analyzed to estimate the specific cutting forces and edge force coefficients. Simultaneously, the flank wear width is recorded using an image-based on-machine measuring device installed in the machine tool. From this information, the average stresses at the primary and tertiary cutting zones are estimated, while the cutting temperature in the primary cutting zone is roughly estimated by considering the traditional shear-angle prediction theory. Using these estimations, hardness and residual stress are calculated based on a simple linear regression model. Parameter identification for the model is performed based on measured hardness and residual stress in end-milling experiments. The model was validated against experimental measurements, which showed that the proposed method can accurately estimate hardness and residual stress, although it was observed that the selection of explanatory variables has a significant effect on accuracy.

O054 What Measure of CPAP Treatment is most closely Associated with Reduced Risk of Future Major Cardiovascular Events (MACE)?

Abstract Introduction Obstructive sleep apnoea (OSA) is associated with future Major Adverse Cardiovascular Events (MACE). Continuous positive airway pressure (CPAP) is the standard treatment for OSA, but it is not known which measure of CPAP treatment is most closely associated with reduction in future MACE. We compared associations between a novel and a commonly used measure of CPAP treatment and future MACE. Materials and Methods Participants: 2717 adults with moderate-severe OSA attending a tertiary sleep clinic 2006-2010 completed baseline assessments and followed-up for 7years. CPAP treatment: Month-long CPAP trial and periodic review post-trial. Outcomes Time to cardiac death or non-fatal hospitalisations due to MACE, or end of follow-up, using Cox proportional hazards models. Predictors Average nightly CPAP use and the SARAH index (Sleep-Adjusted Residual AHI), using all available device downloads SARAH index=([AHITreatment×HoursTreatment]+[AHIUntreated×HoursUntreated])/HoursTotalSleepTime Covariates Demographics/comorbidities associated with MACE. Results MACE occurred in 18% participants. Average nightly use: Compared to zero use, each tertile of increasing use predicted reduction in risk of MACE (tertile-0:ref, tertile-I:HR 0.632, 95%CI 0.484-0.824, p<0.001, tertile-II:HR 0.772, 95%CI 0.602-0.990, p=0.042, tertile-III:HR 0.708, 95%CI 0.553-0.905, p=0.006). SARAH A dose-response decreasing risk of MACE with decreasing SARAH index tertiles (tertile-I:ref, tertile-II:HR 0.827, 95%CI 0.658-1.039, p= 0.102, tertile-III:HR 0.772, 95%CI 0.614-0.969, p=0.026). Conclusions Average nightly CPAP use and SARAH index were associated with a decreased risk of future MACE. The SARAH index showed a dose-response relationship with MACE; suggesting that it may be a better estimate of residual OSA-related cardiovascular stress.

Analysis of the geometrical influence of ring-opening samples on arterial circumferential residual stress reconstruction.

This work consists of analyzing the impact of geometrical features (thickness and curvature) on the estimation of circumferential residual stresses in arteries. For this purpose, a specific sample of lamb abdominal artery is chosen for analysis and, through computational tools based on Python libraries, the stress-free geometry is captured after the ring opening test. Numerical simulations are then used to reconstruct the sample in order to estimate the circumferential residual stresses. Then, four stress-free geometry models are analyzed: an ideal geometry, i.e., constant curvature and thickness; a constant curvature and variable thickness geometry; a variable curvature and constant thickness geometry; and a variable curvature and thickness geometry. The numerical results show that models perform well from a geometric point of view, where the most different feature was the closed outer perimeter that differs about 14% from the closed real sample. As far as residual stress is concerned, differences up to 198% were found in more realistic models taking a constant curvature and thickness model as reference. Thus, the analysis of a realistic geometry with highly variable curvature and thickness can introduce, compared to an idealized geometry, significant differences in the estimation of residual stresses. This could indicate that the characterization of arterial residual stresses is not sufficient when considering only the opening angle and, therefore, it is also necessary to incorporate more geometrical variables.

Application of spherical macro-indentation for determination of plastic anisotropy and residual stresses using indentation geometry and inverse analysis

The simultaneous determination of mechanical properties and residual stresses using the instrumented indentation technique is more challenging when the anisotropic behaviour of a material is considered. If ignored, it may lead to inaccurate estimation of residual stresses and mechanical properties of materials. In this paper, the existence of in-plane anisotropic plasticity and the equi-biaxial residual stresses were considered in materials simultaneously. These anisotropic plastic properties and residual stresses were extracted for two materials, an aluminium alloy and a stainless steel, using an inverse analysis method and macro-spherical indentation test. The considered anisotropic materials have different yield stresses in both the longitudinal and transverse directions of the part. The inverse analysis method was based on a wide range of finite element (FE) simulations, which included a large number of models covering the properties of different steel and aluminium materials. In this method, the parameters extracted from the load-displacement (P-h) curve for indentation, along with the pile-up around the indentation area after unloading, were considered as the input parameters of the inverse analysis method. The outputs were the mechanical properties of the anisotropic material and the equi-biaxial tensile and compressive residual stresses. The proposed inverse method was based on the analysis of the artificial neural network (ANN). The effectiveness of the inverse method was examined and verified using experimental data which were found to be reliable. The method employed the P-h curve parameters and unloading morphology and was successful to determine the anisotropic plastic properties and residual stresses.

DETERMINATION OF RESIDUAL STRESSES IN PIPES

During production, operation, transportation, and aging of finished products, stresses occur in the pipe metal. As a rule, these residual stresses affect the quality of pipes. The presence of residual stresses in products can cause brittle fracture, cracking due to corrosion, reduced elasticity, warping, etc. The development of methods for managing residual stresses in metals and products is the realization of a powerful reserve for improving the quality of metal products, which means increasing the reliability of machinery. The question arises as to which method, convenient in production conditions, should be used to assess residual stresses. A simple and affordable method for estimating residual stresses is needed in production conditions. This paper presents a simplified method for estimating residual stresses in pipes. The purpose of the work is to improve and present a methodology for estimating tangential and axial residual stresses in cold-formed pipes and tubes after heat treatment according to the method of M.M. Davydenko. Research methods: M.M. Davydenko's method for cutting rings and cutting strips from pipes. Calculation of residual stresses. Results. The method for estimation of tangential and axial residual stresses in pipes after cold deformation and after heat treatment is improved and presented. The formulas for calculating residual stresses are given. Practical value. Pipe plants need to estimate residual stresses to develop technological processes for the manufacture of new types of pipes and to meet pipe standards. The improved and presented methodology will help manufacturers in assessing residual stresses. Conclusions. Modern methods for assessing residual stresses have been considered. A methodology for calculating tangential and axial residual stresses according to M.M. Davydenko by cutting rings and cutting strips from the metal of the studied pipes is presented. The methodology is officially registered, which allows it to be used for official assessment of pipe quality.

Methods to reduce residual welding stresses in mining excavator metal structures

Residual stresses in metal structures of mining machinery caused by welding occur due to simultaneous uneven heating and cooling of local sections of structures, variable cooling rates in the different areas of the weld and deformations caused by metallurgical phase transformations. Residual stress in the welded joint can significantly increase the external load that can lead to structural failure. Research on the calculation, measurement and relief of residual stresses under welding is an important issue when predicting the service life of metal structure units of mining machinery and equipment. An accurate quantitative estimation of residual stresses in welded products, repair welds included, as well as the search for the fundamental principles of the elimination methods of residual deformations are of considerable practical interest, which is relevant for the authors of this paper. The study involved a general review of the latest researches in the field of estimation and measurement of residual stresses caused by electrogas welding. It has been proposed to use various techniques and analytical methods for quantitative estimation of welded joint residual stresses on the basis of fracture mechanics, which enabled to take preventative measures at early stages to reduce the cost of repair and maintenance of welded metal structures of mining excavators. The conducted study resulted in formulating the proposals on relief of residual welding stresses in the metal structures of mining excavators.

Estimation of Residual Stresses in Pipe-Ring Specimens by Incremental Hole Drilling and X-Ray Diffraction Method

Estimation of Residual Stresses in Pipe-Ring Specimens by Incremental Hole Drilling and X-Ray Diffraction Method

Experimental and numerical study on residual stress distributions in welded H-sections of High-strength steel

High-strength steel (HSS) has been increasingly applied in structural engineering, while the work on residual stress of HSS sections is still insufficient. Limited research is available for welded H-sections above 690 MPa while with a plate thickness of more than 10 mm. This paper deals with the residual stress distributions of welded H-sections with flame-cut edges, which are fabricated from HSS plates with yield strength of 690 MPa and 960 MPa and thickness of 10 mm–20 mm, using both experimental and numerical method. The experiments showed that the welded tensile residual stresses in the weld region are not significantly affected by sectional dimensions and steel grade. Verified by comparing with the experimental results, three-dimensional (3D) finite element (FE) models using sequentially coupled thermal-stress analysis was adopted for parametric study of compressive residual stress of welded H-sections made of 690 MPa HSS. The results showed that the compressive tensile stress is negatively correlated with plate thickness as well as width-thickness ratio. Through regression analysis, formulae were proposed for estimation of compressive residual stress in the flange and web, respectively. Finally, residual stress distribution model was developed, which was proved effective by comparing with the experimental and FE results.

Estimation of Residual Stresses in Coatings of “Hard” Topocomposites by Repeated Microindentation

Estimation of Residual Stresses in Coatings of “Hard” Topocomposites by Repeated Microindentation