The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC pha...The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300°, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300°due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200°, then delamination wear and oxidative wear at 300°and became oxidative above 300°. Moreover, the adhesive wear existed concomitantly below 300°.展开更多
Understanding three-dimensional (3D) slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mecha-nisms of progressi...Understanding three-dimensional (3D) slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mecha-nisms of progressive failure with thrust-type and pull-type landslides are described in detail. It is considered that the post-failure stress state and the pre-peak stress state may occur at different regions of a landslide body with deformation development, and a critical stress state element (or the soil slice block) exists between the post-failure stress state and the pre-peak stress state regions. In this regard, two sorts of failure modes are suggested for the thrust-type and three sorts for pull-type landslides, based on the characteristics of shear stress and strain (or tensile stress and strain). Accordingly, a new joint constitutive model (JCM) is proposed based on the current stability analytical theories, and it can be used to describe the mechanical behaviors of geo-materials with softening properties. Five methods, i.e. CSRM (comprehensive sliding resistance method), MTM (main thrust method), CDM (comprehensive displacement method), SDM (surplus displacement method), and MPM (main pull method), for slope stability calculation are proposed. The S-shaped curve of monitored displacement vs. time is presented for different points on the sliding surface during progressive failure process of landslide, and the rela-tionship between the displacement of different points on the sliding surface and height of landslide body is regarded as the parabolic curve. The comparisons between the predicted and observed loadedis-placement and displacementetime relations of the points on the sliding surface are conducted. The classification of stable/unstable displacementetime curves is proposed. The definition of the main sliding direction of a landslide is also suggested in such a way that the failure body of landslide (simplified as“collapse body”) is only involved in the main sliding direction, and the strike and the di展开更多
基金the opening project from National Key Laboratory for Remanufacturing (No. 61420050204)the Department of Energy (DOE), Office of Fossil Energy, National Energy Technology Laboratory (DE-FE-0011194), with Mr. V. Cedro, Mr. R. Dunst, and Dr. J. Mullen as program managers+1 种基金the support of the U.S. Army Research Office project (W911NF-13-1-0438) with the program manager, Dr. M. P. Bakas and Dr. D. M. Steppsupport from the National Science Foundation (DMR-1611180) with the program directors, Dr. G. J. Shiflet and D. Farkas
文摘The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300°, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300°due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200°, then delamination wear and oxidative wear at 300°and became oxidative above 300°. Moreover, the adhesive wear existed concomitantly below 300°.
基金supports from the National Natural Science Foundation of China (Grant No. 41372363)National Important Research of China (Grant No. E0907-90815018)
文摘Understanding three-dimensional (3D) slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mecha-nisms of progressive failure with thrust-type and pull-type landslides are described in detail. It is considered that the post-failure stress state and the pre-peak stress state may occur at different regions of a landslide body with deformation development, and a critical stress state element (or the soil slice block) exists between the post-failure stress state and the pre-peak stress state regions. In this regard, two sorts of failure modes are suggested for the thrust-type and three sorts for pull-type landslides, based on the characteristics of shear stress and strain (or tensile stress and strain). Accordingly, a new joint constitutive model (JCM) is proposed based on the current stability analytical theories, and it can be used to describe the mechanical behaviors of geo-materials with softening properties. Five methods, i.e. CSRM (comprehensive sliding resistance method), MTM (main thrust method), CDM (comprehensive displacement method), SDM (surplus displacement method), and MPM (main pull method), for slope stability calculation are proposed. The S-shaped curve of monitored displacement vs. time is presented for different points on the sliding surface during progressive failure process of landslide, and the rela-tionship between the displacement of different points on the sliding surface and height of landslide body is regarded as the parabolic curve. The comparisons between the predicted and observed loadedis-placement and displacementetime relations of the points on the sliding surface are conducted. The classification of stable/unstable displacementetime curves is proposed. The definition of the main sliding direction of a landslide is also suggested in such a way that the failure body of landslide (simplified as“collapse body”) is only involved in the main sliding direction, and the strike and the di
