Analysis Of Residual Stress Distribution Research Articles

A proposal of depth profile analysis method of strain distribution in surface layer using x-ray diffraction at small glancing angles of incidence

Diffracted x-rays at small glancing angle of incidence on surface materials were investigated as function of incidence angles for the studies of residual stresses of surface layers. The intensity of x-ray propagation in surface layer materials characterized by a complex refractive index that changes continuously with depth was derived, and with use of the result, an analyzing method for evaluating the depth profiles of the strain distribution in the surface layer was studied. The derived analyzing method can be applied to the residual stress distribution analysis of the surface layer materials of which densities change continuously in depth as multi thin films, compound plating layers. Now, the analyzing method for the depth profile of the strain distribution in the surface layer using x-ray diffraction at small glancing angles of incidence was discussed with correction on some errata of equations in the previous studies.

Design of Si3N4-based ceramic laminates by the residual stresses

Ceramic laminates with strong interfaces between layers are considered a very promising material for different engineering applications because of the potential for increasing fracture toughness by designing high residual compressive and low residual tensile stresses in separate layers. In this work, Si3N4/Si3N4-TiN ceramic laminates with strong interfaces were manufactured by rolling and hot pressing techniques. The investigation of their mechanical properties has shown that the increase in apparent fracture toughness can be achieved for the Si3N4/Si3N4-20 wt.%TiN composite, while further increase of TiN content in the layers with residual tensile stresses lead to a formation of multiple cracks, and as a result, a significant decrease in the mechanical performance of the composites. Micro-Raman spectroscopy was used to measure the frequency shift across the Si3N4/Si3N4-20 wt.%TiN laminate. These preliminary Raman results can be useful for further analysis of residual stress distribution in the laminate.

Finite Element Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction

This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of three-dimensional temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.

Depth profiling of the strain distribution in the surface layer using X-ray diffraction at small glancing angle of incidence

In the studies of residual stresses of surface materials by using X-ray, in-depth distribution of the strain in the surface layer is necessary to be analyzed. We, therefore, characterized the refractive index of the surface layer materials with complex refractive index, which changes continuously in depth, and derived the X-ray intensity propagating during the surface layer materials. We applied this analyzing method to the experimental results of X-ray diffraction at small glancing angle incidence, and obtained the depth profile of the strain in the surface layer. The derived analyzing method can be applied to the residual stress distribution analysis of the surface layer materials of which densities change continuously in depth as multi thin films, compound plating layers.

X-ray stress measurement and FEM analysis of residual stress distribution near interface in bonded ceramic/metal compounds

There are enormous heterogeneous interfaces in the interior of metal matrix composites (MMCs). Because of the significant difference between the coefficients of thermal expansion (CTEs) of the matrix and reinforcement, the complicated thermal residual stresses are believed to be induced into the matrix and reinforcement near the interfaces when composites are fabricated or annealed at a certain high temperature and cooled down to room temperature. In order to obtain a further understanding of the thermal residual stress distribution near the interfaces in such a material, the residual stress distribution along the depth in 6061 Al component of bonded SiC/6061 Al model material was determined by X-ray stress measurement. Meanwhile, FEM was performed to analyze the residual stress distribution in the two constituents and the results were discussed. In the bonded SiC/6061 Al model material, the residual stress distribution is nearly linear in SiC component, and non-linear in the 6061 Al part. The calculated results indicate that the residual stress state in the components depends on the ratio of the thickness of ceramic and metal. The measured and calculated residual stress distributions are in agreement in general trend, however the calculated values are higher than the measured ones.

FEM Analysis of Residual Stress Distribution in Ceramics/Metal Joints.

FEM Analysis of Residual Stress Distribution in Ceramics/Metal Joints.

傾斜組成コーティング部材の残留応力特性

The residual stresses of gradation coating components induced by a fabrication process were analyzed by comparison with two-layer composites prepared by a direct bonding.Firstly, the gradation coating components of stabilized zirconia/nickel based alloy composites were chosen for a finite element method analysis of residual stress distributions. It was verified that the residual stresses at the interface produced by a uniform heating process decreased by use of the gradation techniques. Especially, stress singularities at the edge of the interface of the direct bonding composites disappeared in case of the gradation coating components. However, the residual stresses at the surface of the gradation coating could not be decreased using the gradation techniques.Secondly, the effects of the gradation geometry and material constants, such as Young's modulus and thermal expansion coefficients on the residual stresses of the gradation coating components were investigated by the thermoelastic analysis using a finite element method. As a result, it was found that the residual stresses could be effectively analyzed by application of the dimensionless parameter, which is σ(1-μ2)/[E2(α1-α2)ΔT](σ; residual stress, μ1=μ2; Poisson's ratio, E2; Young's modulus of coating film 2, (α1-α2); difference of thermal expansion coefficients between substrate 1 and coating film 2, ΔT; temperature difference) in case of the gradation coating components. The analytical results indicated that the dimensionless residual stresses decreased with increasing the coating thickness ratio, t/T (t; coating thickness, T; substrate thickness) and Young's modulus ratio, E2/E1.

Residual Stress Characteristics of Functionally Gradient Materials

The residual stresses of functionally gradient materials induced during the fabrication process were analyzed by comparing with two-layer composites prepared by direct bonding. Functionally gradient materials can be grouped into three classes, structurally gradation plates from the surface to the back, gradation coatings formed on the substrate, and gradation joints formed between base metals. In this paper, firstly, these three types of functionally gradient materials of stabilized zirconia/nickel-based alloy composites were chosen for finite element method analysis of residual stress distributions. It was verified that the residual stresses induced by uniform heating process could be decreased by use of the gradation techniques. Especially, the stress singularities at the edge of the interface of direct bonding composites were eliminated in case of the functionally gradient materials. Secondly, the effects of gradation size and material constants, such as Young's modulus and thermal expansion coefficients on the residual stress of the functionally gradient materials were investigated by the thermo-elastic analysis using the finite element method. It was found that the residual stresses could be effectively analyzed by application of a dimensionless parameter, which is σ(1-μ1)/[E1(α1-α2)ΔT] (σ: residual stress, μ1=μ2: Poisson's ratio, E1: Young's modulus of material 1, (α1-α2): difference in thermal expansion coefficient between materials 1 and 2, ΔT: temperature difference) in case of the functionally gradient materials. Thus, the analytical results indicated that the fabrication of large functionally gradient materials was difficult because of the increasing of the residual stresses for the same gradation thickness.

On the layer removal analysis of residual stress

The layer removal analysis of residual stress distribution is examined for mouldings which contain depth-varying Young's modulus. The approach is to compute the stress distribution which would be derived from the layer removal procedure if the assumption is made that the Young's modulus is uniform, and to compare it with the actual stress distribution. For this analysis a parabolic stress distribution is assumed to be present, and computed distributions are obtained for two cases, (i) in which the modulus varies linearly from the surface to the centre of the moulding and (ii) in which the modulus has a constant value near to the surface (“skin”) then changes suddenly to another constant value in the interior (“core”). The general features of the computed profiles are compared with experimental layer removal analyses conducted on injection-moulded specimens and the extent to which non-uniform modulus influences the results of such studies is discussed.