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Microstructure formation and fatigue performance of duplex stainless steel 2205 welded joints by electric resistance welding

Dong Zhilong, Xie Xue-fang, Li Jingwen, Wan Yu, Wang Chaolei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e180, 2023

EN

The electric resistance welding of thin-thickness duplex stainless steel (DSS) has an outstanding attraction in the plate-fin heat exchanger which is widely used in power machinery, diesel locomotive and other fields, but its structural integrity is threatened seriously by fatigue failure. Therefore, in this research, the formation of the heterogeneous microstructure of DSS electric resistance welding joints (ERWJ) was analyzed by the optical microscope (OM) and electron back-scattered diffraction (EBSD) observations, and the uniaxial tensile and fatigue tests were subsequently executed to disclose their mechanical properties. The intrinsic relevancy between phase-related characteristics and failure behavior was extensively analyzed. The results show that the ferrite was dominating at whole ERWJ, particularly at the energized area, accounting for up to 72%. More than 45% of high-angle boundaries (HABS) and the highest kernel average misorientation (KAM, 2.46° for austenite and 1.52° for ferrite), which indicates greater plastic deformation and residual stress, were observed at the weld edge. In addition, the failure occurred as a tear along the weld edge regardless of the monotonic and cyclic loadings under the deterioration of residual stress and island-like austenite. The distribution of fatigue life with cyclic amplitude performed an obvious turning point of 19.5 MPa due to the different failure mechanisms, providing a permissible range of the stress amplitudes and reinforcement strategies for the plate-shell heat exchanger ERWJ in the engineering.

2

Surface hardening effect on the fatigue behavior of isotropic beam

Nasser Sajad H., Bader Qasim H.

Diagnostyka

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2022

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Vol. 23, No. 3

art. no 2022312

EN

This paper is to present an experimental study of the impact of surface hardening on the high-cycle fatigue behavior of an isotropic beam. The beams made from low carbon steel (St 44-2). Surface treatments used are pack carburizing and carbonitriding. The experimental work included mechanical test, surface heat treatment, fatigue test and Microscopic inspection. The surface hardening was done by using pack-carburizing process at a temperature of 925°C holding time variation (2, 4, and 6hr) followed by quenching and tempering process, and using the carbonitriding process at a temperature of 800°C and for periods (0.5, 1 and 1.5hr) then quenching directly in water. The fatigue test was carried out by a cantilever rotating-bending system. The results of an experimental fatigue test indicate that various behaviors depend on surface heat treatment and time soaking. The findings indicate that carbonitriding has a greater impact on the fatigue strength and life than the specimen has been treated with pack carburizing. In addition, as the time soaking increase, the fatigue life will increase for both types of surface heat treatments. It was found that the specimens that were hardened using the carbonitriding process achieved a higher surface hardness as the hardness increased to 1644.62HV, while the untreated specimens were 293HV. Compared with the hardening using the pack carburizing process.

3

Analyzing mechanical behavior of ABS-SiO2 polymer-based nanocomposite based on ANOVA method

Afzali Mohammad, Asghari Vahid

Composites Theory and Practice

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2021

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R. 21, nr 3

61--69

EN

The fabrication of polymer-based nanocomposites by means of twin extruders is a typical method for manufacturing lightweight and high-strength structures. However, selection of the optimal parameters for this process to study the material characteristics is important. The primary aim of the present study was to ascertain the optimum extruder temperature and nanosilica content in an acrylonitrile-butadiene-styrene matrix composite. The response surface methodology was based on two factors and three levels. The identification of the effect of the parameters on the fatigue behavior of the fabricated composite was comprehensively analyzed. The results were analyzed using scanning electron microscopy (SEM). The obtained results revealed that up to 4% nano-SiO2 improves tensile strength and reduces the impact toughness. On the other hand, an increase in the extrusion temperature yields a higher impact toughness and lower tensile strength. The optimization results showed that 2.5% nanosilica and the extrusion temperature of 225°C result in the maximum tensile strength of 41 MPa, and impact toughness of 30 KJ/m2.

4

Tensile-tensile Fatigue Behavior of Multi-axial Warp-knitted Reinforced Composite

Gao X., Tao N., Chen S., Wang L., Wu W.

Fibres & Textiles in Eastern Europe

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2018

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Vol. 26, no. 1 (127)

73--80

EN

An experimental study was carried out on the fatigue behaviour of multi-axial warp-knitted fabric composites. Composite samples reinforced with multi-axial warp-knitted fabric/matrix were manufactured by the vacuum-assisted resin transfer moulding method. Tensile-tensile fatigue cycling was carried out at different load levels, and S-N curves, tensile stress-strain curve and stiffness degradation of the multi-axial composite samples were obtained. Finally post-fatigue tensile tests were done at a stress level of 75%, at the stages of 1/3N and 2/3N, and the equivalent residual strength and stiffness degradation were obtained.

PL

Dokonano oceny właściwości mechanicznych i zmęczeniowych kompozytowych dzianin wieloosiowych. Kompozyty wzmocnione dzianiną wieloosiową wytworzono przy zastosowaniu próżniowej metody formowania. Dokonano oceny zmęczenia materiału i właściwości wytrzymałościowych przy różnych poziomach obciążenia. Przedstawiono krzywe S-N, krzywą naprężenie-odkształcenie i degradację sztywności wieloosiowych próbek kompozytowych. Wykonano również testy zmęczenia materiału przy poziomie naprężenia 75%, w etapach 1/3N i 2/3N. Omówiono równoważną wytrzymałość szczątkową i degradację sztywności kompozytowych dzianin wieloosiowych.