Papers by Keyword: Residual Strains

Abstract: In order to quantitatively understand the residual strain distributions and benefits of engineering components following special technique treatment, such as Autofrettaging, Hot Isostatic Pressing (HIP) and Dissimilar Material Welding (DMW), the Neutron Diffraction Technique (NDT) has been employed recently to measure residual strain and stress distributions on following three cases of (a) Autofrettaged Aluminum 7075 high pressure vessels; (b) Hot Isostatic Pressed (HIPPED) heavy metals of tungsten clad in tantalum plate and (c) Dissimilar Material Welding (DMW) of 316L austenitic stainless steel and ferritic steel AS508 with Alloy 52 weld filler. This paper reports the recent research findings, including (a) NDT can identify optimal Autofrettage pressure level, by which load bearing capacity of the Autofrettaged pressure vessel increased by 215MPa; (b) NDT is able to reveal residual strains within heavy metals of Tungsten clad in Tantalum plate HIPPED and (c) NDT revealed a maximum residual tensile hoop stress value of about 494MPa in the interface between parent material SA508 and the weld seam. This is vital information for the post weld process and subsequent safe use of the dissimilar materials weld. Other researchers’ successful examples of working with NDT are also briefly reviewed. Future prospective of Engineering Materials Diffractometer (EMD) at CSNS is described too with a view to demonstrating the application and importance of NDT in revealing residual strain-stresses that are inevitable within engineering materials and engineering components following any manufacturing process.

Abstract: This paper considers a deformation process of an incompressible elastoviscoplastic material placed between two coaxial rigid cylinders. The material is deformed when the internal cylinder rotates around its axis while the external one is fixed. The adhesion conditions are set on both boundary surfaces. The theory of large elastoviscoplastic deformations is used to solve the problem. The mathematical model is constructed in cylindrical coordinates.

Abstract: The dimensional problem of a formation of the residual stresses in the thin circular elastoplastic plate under the given thermal action was analytically solved. The generalized Prandtl-Reuss thermoelastoplastic model was used. The effect of the non-stationary temperature gradient on the residual stresses field formation was investigated under the condition that the yield stress depends on a temperature. The borders of the irreversible deformation domain and unloading domain were computed. The level of residual stresses was calculated.

Abstract: An analytical method suitable for modelling the creep-age forming (CAF) of doubly curved aluminium plates is presented. This new mechanics model combines an efficient numerical integration method with a robust set of CAF constitutive equations that has been experimentally validated with AA7055 at a CAF condition. Corresponding finite element simulations show good agreement with the analytical results. Using the validated analytical model to investigate a three-stage CAF process (loading, creep-ageing, and unloading), through-thickness strain distributions are studied for aluminium plates that have been subjected to different creep-ageing time. A creep activation point (CAP) is revealed and a correlation is found between the two parameters introduced in this work – the normalised location of CAP, zCAP and normalised bend ratio, β. More specifically, a linear relationship is found between β and zCAP, which indicates that the onset of creep strain, and hence the sizes of the pure elastic core and the outer creep region, can be readily predictable within the limits of study. It is now possible to simulate two-dimensional bending CAF processes for aluminium alloys that have non-spherical precipitates.

Abstract: W is a promising material to use as protection for thermal shields in future nuclear fusion reactors, however the joining to other metals is really challenging. For realizing such joints plasma spraying (PS) has been used for its simplicity, the possibility to cover complex and extended surfaces and the relatively low cost. An appropriate interlayer must be optimized to increase the adhesion of W on the substrates and to provide a soft interface for better thermo-mechanical compatibility.The present work demonstrates that high-temperature X-ray diffraction (HT-XRD) permits to quickly assess the reliability and quality of the coating-interlayer-substrate system by measuring the strain of coating. This is very useful to orientate the work for optimizing the structure and composition of the interlayer and the parameters of deposition process.

Abstract: In this paper, the residual deformation induced in laser welding processing was studied by using the moiré interferometry and a novel high-temperature specimen grating technology. The experimental results indicate that the heat-affected zone of laser welding is a narrow strip. There exists great residual strain gradient in the heat-affected zone, especially great residual shear strain gradient. It implies that great residual stress and stress gradient exist near the welded seam. The relationship between the size of the heat-affected zone and the changes of the technology parameters were discussed in the experiments, which can supply some reliable experimental data for optimizing processing technology.

Abstract: The performance of an unconventional high-resolution neutron diffractometer using Bragg diffraction optics that can be efficiently employed in strain/stress diffractometers are reported. Presented results demonstrate their experimental abilities for powder diffraction, namely for residual strain/stress measurements. In addition to the macrostrain scanning capability, the device can also be used for microstrain/stress studies by suitable analysis of the diffraction profiles. Two examples of the strain measurements are presented.