Characterization Of Residual Stresses Research Articles

Residual Stress Characterization in Additively Manufactured Titanium Alloy Rod-Type Specimens Prepared by Laser Powder Bed Fusion

Residual Stress Characterization in Additively Manufactured Titanium Alloy Rod-Type Specimens Prepared by Laser Powder Bed Fusion

Application of instrument indentation test for residual stress characterization of 5083 aluminium alloy

Abstract An abnormal cracking phenomenon occurred at the corner of a ventilation window on the 5083 aluminum alloy wallboard used in certain transportation equipment. The residual stresses of the wallboard were measured using an instrumented indentation test. Initially, stress loading was applied to the 5083 specimens using a residual stress loading device to verify the effectiveness of the instrument indentation test (IIT) for testing the residual stresses of 5083 aluminum alloy. Subsequently, IIT was conducted under static conditions at the serving site of the equipment, and the working stresses under dynamic conditions were detected using a strain monitor. The results indicate that the total tensile stress at the uncracked corner of the ventilation window has exceeded the 5083 yield strength, so excessive tensile stress is the main cause of the abnormal cracking of the wallboard.

Effect of shot peening on surface characteristics and high-temperature corrosion behaviour of super 13Cr martensitic stainless steel

Super 13Cr, as an economy stainless steel (SS) for oil country tubular goods, needs stable corrosion resistance in high-pressure and high-temperature (HPHT) downhole medium. Severe plastic deformation (SPD) are the surface modification technology to improve mechanical properties, fatigue behavior and corrosion resistance of metals, and shot peening (SP) has been the most widely used SPD process. However, there are quite limited studies about the microsutructure evolution, residual stress, and high-temperature corrosion behavior of SP-treated martensitic SS. In this study, super 13Cr martensitic SS was treated by SP with various air pressures and nozzle speeds. The surface characteristics and high-temperature corrosion behaviour in 3.17 mol/L K2HPO4 solution were investigated through finite element model analysis, characterization of residual stress and microstructure, as well as electrochemical and stress corrosion cracking (SCC) tests at 160 °C and 10 MPa. The results showed that SP-treated super 13Cr could generate high-level compressive residual stress and SPD microstucture, including nano-sized equiaxed grains, gradient lamellar structure and fragmented carbides. Increasing air pressure contributed to achieve uniform nanocrystalline, but tended to generate high dislocation density and surface defects. The improving effect of SP treatment at low air pressure of 0.15 MPa on passivation ability was limited, and high air pressure adversely impacted corrosion resistance. SP-treated specimens showed high SCC susceptibility, due to the introduction of more surface defects, high angle grain boundaries, and dislocations.

Three-Dimensional Characterization of Residual Stress in Aircraft Riveted Panel Structures

Three-Dimensional Characterization of Residual Stress in Aircraft Riveted Panel Structures

A FEM-guided data-driven machine learning model for residual stress characterization in ultrasonic surface rolling of lightweight alloys

A FEM-guided data-driven machine learning model for residual stress characterization in ultrasonic surface rolling of lightweight alloys

Residual Stress Characterization in Microelectronic Manufacturing: An Analysis Based on Raman Spectroscopy

AbstractIn the rapidly evolving era of information and intelligence,microelectronic devices are pivotal across various fields, such as mobile devices, big data computing, electric vehicles, and aerospace. However, the electrical performance of these devices often suffers due to residual stress from microelectronic manufacturing. This issue is compounded by the additional thermal stress that accumulates during device operation. Therefore, it is essential to understand, characterize, and control this residual stress to ensure the reliability and efficiency of microelectronic devices. Raman spectroscopy emerges as an invaluable tool for nondestructive, fast, noncontact, and precise testing of micro‐scale mechanics, significantly aiding in stress and strain analysis within microelectronic manufacturing. This article aims to provide a thorough overview of the theory and application beyond a mere compilation of recent advances. Theoretically, it critically evaluates existing models that describe the Raman‐stress relation. Practically, it explores the application of Raman spectroscopy in researching residual stress in various components, including substrate materials, epitaxial films, and packaging. Through a detailed examination of current applications, it highlights the significance of Raman spectroscopy in understanding micro‐scale mechanics. Finally, it offers both theoretical and practical insights into the future developments of Raman‐stress detection technology.

Residual Stress Mapping in Heat-Assisted Additive Manufacturing of IN 718: An X-Ray Diffraction Study

Laser powder bed fusion (LPBF) is a type of additive manufacturing (AM) technique characterized by multiple localized thermal processes that result in rapid heating and cooling. The thermal variations observed in the LPBF process can generate residual stress (RS) inside the fabricated part, impacting the surface integrity and geometric tolerances of the manufactured components. To reduce thermal variation during manufacturing, heat-assisted AM was employed, thereby minimizing RS and any thermal distortion that could occur during the fabrication of materials. The present research utilizes non-destructive x-ray diffraction to analyze the influence of an in-situ heated building plate and processing parameters on the RS distribution in Inconel 718 (IN718) fabricated by LPBF. This study examines the impact of two scanning procedures and three laser power levels and offers critical insights into both measurement techniques and RS characterization. By understanding the effect of the processing parameters on RS, we aim to enhance the quality of manufactured parts through process optimization. Post-processing heat treatment consistently reduced RS in all samples, regardless of laser power levels or scanning strategies. Combining a chess scanning strategy with 270 W laser power resulted in the most significant RS reduction in IN718.

Ultrasonic characterization of material anisotropy in additively manufactured AlSi10Mg

Metal additive manufacturing (AM) based on laser powder bed fusion (LPBF) generates components by melting metal powder on a layer-by-layer basis. The melting and cooling process often generates samples with a preferred material symmetry aligned with the build direction. This anisotropy affects mechanical performance and can be challenging to characterize nondestructively. Here, LPBF was used to create samples of AlSi10Mg with specific geometries to affect the overall anisotropy. In addition, the hybrid AM process of interlayer milling was used to impact the microstructure and residual stress of some samples. Ultrasonic measurements were used to characterize the samples using both coherent wave and diffuse wave experiments to capture the anisotropic nature of the wave speed and scattering. The material symmetry and morphology of the grains affect the wave speed, attenuation, and backscatter with respect to direction. Furthermore, spatially resolved acoustic spectroscopy was used to provide insight regarding the localized wave speeds with respect to sample location and propagation direction. The experimental data were used collectively to quantify differences between the AM processes used to create the samples. Such information can be used to guide AM process parameters to optimize sample performance. Finally, prospects for characterization of residual stresses will be discussed.

Investigation of Surface Residual Stress, Mechanical Properties, and Metallurgical Characterization of Inconel 625 Multilayer Thin-Wall Component Using Cold Metal Transfer Technique

Investigation of Surface Residual Stress, Mechanical Properties, and Metallurgical Characterization of Inconel 625 Multilayer Thin-Wall Component Using Cold Metal Transfer Technique

Initializing intragranular residual stresses within statistically equivalent microstructures for crystal plasticity simulations

We propose a mechanics framework to compute intragranular or type III residual stress within a polycrystalline aggregate for which experimental characterization of residual stress is unknown. The framework is built upon the inter-relationship between intragranular misorientation (IGM), geometrically necessary dislocation (GND), and long-range internal stress. Given a spatial distribution of IGM, we first calculate the spatial distribution of GND density; subsequently, we calculate the internal stress and strain fields due to the GND distribution. For demonstration, we consider a synthetic microstructure of a hexagonal close-packed material, namely Ti-7Al, wherein the grain size and orientation distributions are statistically equivalent to the distributions obtained via experimental characterization. We refer to this microstructure as a statistically equivalent microstructure (SEM). In an SEM, each grain is usually treated as a pristine crystal and therefore, the SEM contains no IGM. We propose a technique to introduce IGM within the SEM and, subsequently, calculate the GND density and residual stress distributions in a consistent manner. In the process, we ensure that statistical distributions of the IGM and residual strain within the SEM are statistically equivalent to the same obtained from the experimental characterization of Ti-7Al. While establishing statistically equivalent residual stress, the thermal effects during processing of Ti-7Al are implicitly taken into account. Next, we perform crystal plasticity finite element simulations to demonstrate the implications of the initialization of IGM and type III residual stress. Although the IGM and residual stress are related, the results suggest that the type III residual stress initialization has a much more pronounced effect on microplasticity-driven damage mechanisms, such as high cycle fatigue, even within a well-annealed material such as Ti-7Al, thereby emphasizing the need for its initialization for microstructure-sensitive fatigue analysis. Finally, we demonstrate that initializing thermally induced residual stress within Ti-7Al SEM through a cooling simulation, accounting for the anisotropic nature of the coefficient of thermal expansion, yields a grain-averaged residual stress distribution statistically similar to that obtained from our framework and is a special case of the type II residual stress implementation.

A Comprehensive Study on Characterization of Residual Stress of Build-Up Layer and Prediction of Chip Warpage

Abstract Better understanding and control of residual stress in the chip build-up layer are becoming more and more important for the assembly process. To estimate the chip warpage and characterize the residual stress, different methods are proposed. However, most of them have high cost or some limitations for the upper build-up material. In this study, an innovative method is proposed to characterize the residual stress and predict the chip warpage behavior of different size chips at different temperatures. The method combines experimental inspection of chip warpage and finite element analysis. By reducing the silicon die thickness, the influence of residual stress in the build-up layer can be amplified. The residual stress can be obtained by inspecting the increased warpage when the silicon dies are reduced to different thicknesses. Correlating the thermal increase warpages of thinner chips can help characterize the effective modulus and coefficient of thermal expansion (CTE) of the build-up layer. This study can help better understand the commonly classified build-up layer information. The results show good agreements between two types of samples under the same upstream process flow.

Qualitative characterization of residual stress of injection molded polycarbonate goggles based on photoelasticity and digital image processing technique

Qualitative characterization of residual stress of injection molded polycarbonate goggles based on photoelasticity and digital image processing technique

On the three‐dimensional numerical analysis of residual stresses on two scales in hot bulk forming parts

AbstractCurrent research focuses on the induction of residual stresses in a component during its manufacturing process, which shows a significant impact on the final component's properties. During the manufacturing of a hot bulk forming component, the temperature evolution allows to influence the resulting residual stress state efficiently and purposefully. Following the characterization of residual stresses on different scales, single‐scale finite element simulations are carried out on macro‐ and microscale. In contrast to previous findings for two‐dimensional boundary value problems, the effects of the third dimension are demonstrated. Furthermore, it is shown that the residual stress distribution is effectively influenced by choosing different cooling routes in targeted manner. Eventually, the importance of microscopic residual stress investigations is discussed.

Residual Stress Characterization of an Additively Manufactured Titanium Alloy

Additive manufacturing (AM) has emerged as a revolutionary technology for producing complex and customized components, particularly in aerospace and medical industries, using materials like titanium alloys known for their exceptional strength-to-weight ratio. However, the inherent thermal gradients and rapid solidification processes during AM can introduce residual stresses in the manufactured parts, significantly affecting their mechanical properties and structural integrity. This study focuses on the comprehensive characterization of residual stresses in additively manufactured titanium alloy components, particularly on understanding the influence of various AM process parameters, post-processing techniques, and part geometries. We employ state-of-the-art semi-destructive techniques, incremental hole drilling and strain gauging to map and quantify the residual stress distribution within the fabricated parts. We elucidate the factors contributing to residual stress formation through carefully designed experiments and numerical simulations, including thermal history, cooling rates, and build orientation. The findings of this research not only advance our fundamental understanding of residual stress mechanisms in additively manufactured titanium alloys but also provide valuable insights for optimizing the AM process and post-processing steps to minimize residual stress-induced defects and enhance the reliability of components in critical applications. Ultimately, this work contributes to the broader goal of unlocking the full potential of additive manufacturing for high-performance engineering materials like titanium alloys.

The Coating Effect on Interconnect Materials After >10 Years of Furnace Exposures

One of the key components in the SOFC stack is the interconnect which requires versatile material properties for a proper functioning, e.g., high temperature corrosion stability, low ASR degradation and low chromium evaporation. At the same time, a high production capacity needs to be reached in order to fulfil the supply demand required for GW levels. The high production capacity is realized through Alleima AB’s production line with coil-coil physical vapor deposition of coated interconnects for SOFC and SOEC applications [1].More specifically, Sanergy HT 441 is the standard material intended to be used as an SOC interconnect. The substrate is a ferritic stainless steel (ASTM 441) which is coated with thin layers of Ce and Co (<1 µm). The material can be coated on both sides using the same coating or with a different coating. At elevated temperatures the Co coating forms a protective (CoMn)3O4 spinel layer which drastically reduces Cr evaporation while the Ce layer improves the corrosion resistance by reducing the chromia scale growth at the coating/substrate interface and thereby maintaining a low and stable ASR over time.Since long-term stability is a critical property for interconnects, Alleima has over the years gathered data from furnace samples and can thus present results where some samples have been exposed at elevated temperatures during >10 years. The main results include the effect of Ce thickness or choice of substrate on mass gain and subsequent chromia growth. Selected samples with coating elements different than Co have also been investigated. Samples have been further investigated using scanning electron microscopy for cross-sections, x-ray diffraction for characterization of phases and residual stresses as well as glow discharge optical emission spectroscopy for elemental analysis.

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.

Characterization of Residual Stress in SOI Wafers by Using MEMS Cantilever Beams.

Silicon-on-insulator (SOI) wafers are crucial raw materials in the manufacturing process of microelectromechanical systems (MEMS). Residual stresses generated inside the wafers during the fabrication process can seriously affect the performance, reliability, and yield of MEMS devices. In this paper, a low-cost method based on mechanical modeling is proposed to characterize the residual stresses in SOI wafers in order to calculate the residual stress values based on the deformation of the beams. Based on this method, the residual strain of the MEMS beam, and thus the residual stress in the SOI wafer, were experimentally determined. The results were also compared with the residual stress results calculated from the deflection of the rotating beam to demonstrate the validity of the results obtained by this method. This method provides valuable theoretical reference and data support for the design and optimization of devices based on SOI-MEMS technology. It provides a lower-cost solution for the residual stress measurement technique, making it available for a wide range of applications.

Residual stress assessment for dissimilar metal welds in nuclear power plant

The European Network on Neutron Techniques Standardization for Structural Integrity (NeT) aims to develop experimental and numerical techniques and standards for the reliable characterization of residual stresses in structural welds. NeT has developed over 20 years and involves over 30 organizations including industrial, academic, and research facilities around the world. The network tackled each specific problem by creating a dedicated Task Group (TG), which undertakes both measurement and modelling studies. NeT TG8 follows on from the successful TG1 and TG4 benchmarks, which studied the dissimilar metal welds (DMW) between 18MnD5 and Alloy 52. The material properties characterization, residual stress measurements and modelling have been conducted for NeT TG8. This paper only presents the NeT TG8 benchmark residual stress measurement in the as welded condition and preliminary simulation results.

Residual stresses in austenitic thin-walled pipe girth welds: Manufacture and measurements

Determining residual stresses in thin-walled pipes is challenging. They are potentially difficult targets for simulation, because they may not behave as simple axisymmetric structures during welding. Thin-walled pipes are more sensitive to changes in the welding heat input than thick-walled pipes. They are also under-represented in the existing population of residual stress measurements used to generate upper bound residual stress profiles for structural integrity assessments. In this paper, residual stress characterisation of two thin-walled austenitic girth welded pipes is presented. The overall geometries of the two mock-up designs were the same; they differed in the linear heat input per pass and the total number of weld passes. The residual stress characterisation was carried out using two independent measurement techniques; the contour method and neutron diffraction. The multiple-cut contour strategy was implemented to measure the cross-sectional maps of hoop and axial stresses on axial-radial and hoop-radial planes respectively. The contour method results are compared with stresses measured using neutron diffraction and specific residual stress distribution signatures observed are discussed.

Examining the change of half-period voltage in longitudinal electro-optic modulation and residual stress of potassium dihydrogen phosphate crystal.

In this paper, the voltage-transmittance curvesKDP crystals were measured accurately between two crossed or parallel polarizers using longitudinal electro-optic effect. The end faces of rectangular KDP samples were coated with ring-shaped electrodes using conductive silver paint (CSP). The change of half period voltage U i has been investigated. A method for quantitative characterization of residual stress has been proposed, based on deviation voltage U d. The results demonstrate that loading voltage is close to the integration of electric field intensity in crystal along the optical path when the CSP ring electrodes have a large outer radius R, small inner radius r, and long-distance d. The half-period voltage U i is also close to longitudinal half-wave voltage U π in these circumstances. The unclamped electro-optic coefficient γ63σ of KDP crystal at room temperature was measured as 10.24±0.05p m/V at the wavelength of 632.8nm.