Two-dimensional mapping of residual stresses in a thick dissimilar weld using contour method, deep hole drilling, and neutron diffraction

Residual stress variations were determined through the thickness of a 70-mm-thick ferritic–austenitic dissimilar steel weld using contour method, deep hole drilling, and neutron diffraction. The result shows that significant tensile stresses were distributed distinctly along the interface between ferritic and austenitic phases. The band of the large tensile stresses was about 8 mm wide and the magnitude reached 400 MPa, which is approaching 100 % of the yield strength of the base metal, near the top surface (about 15 % of the depth). It is attributed to the large difference (5.8 × 10−6 1/°C) of the thermal expansion coefficient between ferritic and austenitic steels of the interface. The microstructure analysis elucidates that the martensitic phase prevailed near the interface and results in microhardness increases

Experimental and Analytical Analysis of Mechanical Properties for Large-Size Lattice Truss Panel Structure Including Role of Connected Structure

The large-size lattice truss panel structure (LTPS) is continually increasing for higher upsizing, but the roles of its connected structures on the mechanical properties are always ignored during the previous structural integrity assessment. Thus, in this paper, a series of mechanical tests, including the fabricating of panel-to-panel LTPSs, monotonous tensile, and three- and four-point bending tests, were performed to comprehensively understand the mechanical behavior. Furthermore, a theoretical model including the role of connected structures was developed to predict both the elastic and plastic deformation behavior of panel-to-panel LTPS. Results show that the connected structure has a very significant effect on the mechanical properties of panel-to-panel LTPS during the three-bending tests, and I-beam element depresses its carrying capacity. The developed theoretical model was proved to accurately predict the experimental results, and the maximum error was limited within 20%. Finally, the dimensional effects of the connection components on mechanical properties were also analyzed by the theoretical model, and indicated that the panel-to-panel LTPS will present better mechanical performance than the intact structure when the width of I-beam element exceeds 12.2 mm or the its length downgrades to 39.1 mm, which provide a comprehensive guidance for the engineering design of large-size LTPS

A Comprehensive Numerical Approach for Analyzing the Residual Stresses in AISI 301LN Stainless Steel Induced by Shot Peening

Shot peening is one of the most famous mechanical surface treatments to improve fatigue performance of metallic components, which is attributed to high amplitude compressive residual stresses. A numerical approach is developed to analyze the residual stresses in 301LN metastable austenitic stainless steel by shot peening. The material behavior is described by a proposed constitutive model in which strain-induced martensitic transformation, isotropic hardening and kinematic hardening effects are taken into account properly. Both single shot and random multiple shots peening were simulated and analyzed. A numerical method is presented with the Python programming language to make the multiple shots follow a random probability distribution. Results demonstrate that the simulated equivalent plastic strains and martensitic volume fractions agree well with the experimental ones, which verify the validity of the constitutive model. Besides, the numerical method is effective at achieving a realistic surface coverage. The maximum compressive residual stress by the Johnson–Cook model is 12% higher than that of the proposed model. Additionally, each hardening effect has an effect on the simulated residual stress. The developed numerical approach can provide a feasible simulation of the shot-peening process and makes an accurate prediction of the residual stress field in 301LN steel

Understanding consumers’ behavior intention of recycling mobile phone through formal channels in China: The effect of privacy concern

The aim of this paper is to explore consumers’ intention of recycling obsolete mobile phone through formal channels in China. Taking Jiangsu Province as an example, the survey results revealed that although nearly half of consumers prefer to save their obsoleted mobile phones at residence, those who are willing to participate in recycling prefer formal recycling channels instead of informal ones. To explore the determinants of formal recycling intention from the perspective of consumers’ psychological characteristics, an integrative model based on the theory of planned behavior was established, in which the effect of consumers’ privacy concern was thoroughly explored. The results indicated that recycling attitude, subjective norm, perceived behavioral control, and moral norm are all positively influential factors. Inconsistent with prior studies, consumers’ privacy concern is found to have a direct positive rather than a negative effect on formal recycling intention. It also has a negative moderating effect on the relationship between subjective norm and formal recycling intention. Therefore, to promote consumers’ formal recycling behavior of obsolete mobile phones, a series of measures are proposed to influence these psychological factors in the model. First, a positive social atmosphere for participation in formal recycling should be vigorously created. Then, further efforts are required to increase the publicity and availability of formal recycling channels. Furthermore, joint efforts should be made for privacy information protection during formal recycling processes, including establishing certification standards for secure data erasure, further routinizing recycling processes and establishing a credible image to obtain consumers’ trust by formal recycling enterprises, etc

Creep damage and crack propagation behavior of printed circuit heat exchanger manufactured by diffusion welding: from material to structure

The printed circuit heat exchanger (PCHE) is extensively used in several applications due to exceptional compactness and heat transfer efficiency. However, the dominant failure mode of PCHE is creep fracture in its diffusion welding joints. Therefore, an accurate prediction of the creep crack propagation behavior for diffusion welding joints is essential for assessing the life of PCHE. In this paper, based on the research route from material to structure, the creep properties of 316L stainless steel base metal and its diffusion welding joint are firstly measured. On this basis, a constitutive model incorporating a time-hardening term for describing the creep damage is established. Furthermore, the creep damage and service life of the PCHE structure under working conditions (600 °C, 20 MPa) are analyzed, along with the effects of structure factors on the creep crack propagation behavior. The results show that the initial decelerating stage and the steady state stage play a dominate role in the creep curve of the diffusion welding joint, differing from the base metal's creep curve. Besides, the creep rate of the joint is approximately 30 times that of the base metal. The established creep damage constitutive model effectively characterizes the creep crack propagation behavior of diffusion welding joints. The maximum creep strain occurs at the weld metal and continuous operation for 100,000 h can be achieved at the designed working condition (600 °C, 20 MPa). For the purpose of lifetime extension by restraining the creep crack, it is recommended to increase the spacing and fillet radius while reducing the diameter during design process