Characterization Of Residual Stresses Research Articles

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

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

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

AbstractLaser 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.

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.

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.

3D fatigue crack path deflection and residual stresses in 17-4PH stainless steel rod

Damage tolerant structures require accurate fatigue crack growth rate models for life prediction. Central to these models are fracture mechanics similitude and empirically gathered growth rates. In this work, standard test methods failed to achieve similitude for 17-4PH stainless steel round-rod but succeeded for plate. Material product form differences are interrogated through constant ΔK tests, crack path analysis, residual stress (RS) characterization, and growth rate simulation. Analyses revealed that quench-induced RS in the round-rod promoted a non-planar, 3D crack path with closure effects. Strategies to mitigate the RS/path effects are evaluated by controlling constraint, closure, environment, and heat treatment.

Electromagnetic (EM) sensor measurement for residual stress characterisation in welded steel plates

ABSTRACT Residual stresses can cause compromise in structural integrity; it is desirable to assess residual stresses using non-destructive testing so that effects on structural properties can be predicted. Electromagnetic (EM) sensors can be used to characterise residual stresses in steels accounting for, microstructure and geometry effects. Residual stress characterisation in welded EN S275 steel plates using EM sensors is reported. Low-frequency, low-magnetic field EM sensors were used to assess residual stresses in the plates. A finite element model for the sensor and sample was generated in COMSOL software so the influence of weld bead geometry and microstructure could be predicted and accounted for. This allowed residual stresses to be determined from EM sensor measurements, excluding the geometry and microstructure effects, XRD was used to verify EM sensor measurements. The highest residual stresses were found adjacent to the weld fusion zone, with magnitudes of, 170±5MPa, 120±20MPa and 42±10MPa for X-ray diffraction (XRD), a small EM sensor (U-12.7) and a big EM sensor (U-31) types, respectively. The differences are due to the volume of the material measured by each measurement type. It was shown that EM sensors are capable of measuring residual stress in welded plates to a good level of accuracy.

Sputter-Deposited Mo Thin Films: Multimodal Characterization of Structure, Surface Morphology, Density, Residual Stress, Electrical Resistivity, and Mechanical Response

Sputter-Deposited Mo Thin Films: Multimodal Characterization of Structure, Surface Morphology, Density, Residual Stress, Electrical Resistivity, and Mechanical Response

Characterization of microstructure and residual stress following the friction stir welding of dissimilar aluminum alloys

Characterization of microstructure and residual stress following the friction stir welding of dissimilar aluminum alloys

Characterisation of residual stresses and oxides in titanium, nickel, and aluminium alloy additive manufacturing powders via synchrotron X-ray diffraction

The strength and fracture toughness of Additively Manufactured (AM) components are significantly influenced by the concentration and size of oxides and precipitate inclusions within the build powders. These features are highly sensitive to powder production parameters, as well as the number of times a powder has been reused. In this study synchrotron X-ray powder diffraction was performed in an inert atmosphere at room temperature and during in-situ heating, providing crucial insights into growth rates and distribution of oxides and precipitates as a function of temperature. From the high angular resolution data collected, the structural refinement showed that plasma wire arc atomisation shows lower residual strain than gas atomised powder samples at room temperature after atomisation likely due to lower temperatures achieved during the production process. Additionally, the results from the diffraction patterns collected during in-situ heating provide key insights to the four metal powders considered in this study, Ti-6Al-4 V, Ni718, AlSi10Mg, and Scalmalloy. This paper also highlights the potential that using synchrotron X-ray diffraction to study AM parts and constituent AM powder has to gain crucial insight into material properties and the build reliability of end use production quality parts from AM.

Characterization and Control of Residual Stress in Plasma-Sprayed Silicon Coatings on SiC/SiC Composites

In order to reveal the relationship between residual stress in Si layers of SiC/SiC composites and the different parameters used in their preparation, the residual stress of the coating surface was tested using X-ray sin2ψ technology and laser Raman spectroscopy. Then, the Raman shift–stress coefficient (P) and the Raman shift with free stress (ω0) were calculated as −201.41 MPa/cm−1 and 520.591 cm−1 via linear fitting with the least squares method. The results showed that all the as-sprayed Si coatings exhibited tensile stress on the surface, ranging from 53.5 to 65.9 MPa. The parameters of the spraying distance and second gas (H2) flow rate were considered to be the most important for controlling the residual stress on the coating surface. Additionally, the surface tensile stress of the Si layers could be eliminated and even changed into compressive stress by annealing above 800 °C. Furthermore, the residual stress distribution in the cross-section of the Si layers was evaluated using laser Raman spectroscopy. Additionally, the particle characteristics, such as in-flight velocity and temperature, were investigated using a diagnostic system. The results of this research contribute to increasing the understanding and control of residual stress in APS Si bond layers.