An interface shear damage model of chromium coating/steel substrate under thermal erosion load

The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.

Experimental study on the shear behavior of the interface between cushion materials and the concrete raft

Cushion is a layer of granular materials between the raft and the ground. The shear behavior of the interface between the cushion and the raft may influence the seismic performance of the superstructure. In order to quantify such influences, horizontal shear tests on the interfaces between different cushion materials and concrete raft under monotonic and cyclic loading were carried out. The vertical pressure P_v, material type and cushion thickness h_c were taken as variables. Conclusions include： 1） under monotonic loading, P_v is the most significant factor; the shear resistance P_（hmax） increases as P_v increases, but the normalized factor of resistance μ_n has an opposite tendency; 2） for the materials used in this study, μ_n varies from 0.40 to 0.70, the interface friction angle δ_s varies from 20° to 35°, while u_（max） varies from 3 mm to 15 mm; 3） under cyclic loading, the interface behavior can be abstracted as a ＂three-segment＂ back-bone curve, the main parameters include μ_n, the displacement u_1 and stiffness K_1 of the elastic stage, the displacement u_2 and stiffness K_2 of the plastic stage; 4） by observation and statistical analysis, the significance of different factors, together with values of K_1, K_2 and μ_n have been obtained.

Influence of Drilling Fluid Components on Shear Strength at Cement-aquifuge Interface in Coalbed Methane Wells

The hydraulic fracturing is still an effective technology for the exploitation of coalbed methane （CBM）. However, after the hydraulic fracturing operation, the high water cut or sudden water flooding of CBM well usually occurs due to upward migration of bottom water, which is called water channeling （water inrush）. This problem has been severely limiting the hydraulic fracturing effect of CBM wells. Some studies show that the aquifuge and cement paste themselves will not crush under hydraulic fracturing pressure. Water channeling often occurs at cement- aquifuge interface （CAI）.

Analysis of mode Ⅲ crack perpendicular to the interface between two dissimilar strips

The present work is concerned with the problem of mode Ⅲ crack perpendicular to the interface of a bi-strip composite. One of these strips is made of a functionally graded material and the other of an isotropic material, which contains an edge crack perpendicular to and terminating at the interface. Fourier transforms and asymptotic analysis are employed to reduce the problem to a singular integral equation which is numerically solved using Gauss-Chebyshev quadrature formulae. Furthermore, a parametric study is carried out to investigate the effects of elastic and geometric characteristics of the composite on the values of stress intensity factor.

锚泊线海床开槽与锚泊基础承载力研究进展综述

Mooring systems are usually adopted to position floating structures,including mooring lines and anchors,and directly determine the safety of floating structures.Seabed inspection reported that seabed trenches induced by mooring line-soil interaction appear in front of the anchor and reduce the anchor bearing capacity.This work first introduces the research progress of mooring line-soil interaction and seabed trenching simulation.Research about the suction anchor capacity in clay and sand is presented,and the seabed trench influence on anchor capacity is analyzed.For anchor analysis,this study gives a new perspective to analyze anchor installation and bearing capacity,i.e.,structure-soil interface characteristic.Some common anchor types are analyzed.Results showed that seabed trench simulation is still needed to acquire trench 3D profiles,in which the mooring line-soil dynamic interaction cannot be ignored.At present,the trench influence is not considered in suction anchor design,making the design dangerous.For the anchor,the interface shear characteristics control the most unfavorable loading conditions.Thus,accurate interface parameters should be obtained for anchor analysis.

The Solids Conveying Mechanism for Helically Grooved Single-screw Extruders

A novel particle-size conveying model was established to examine the effects of the dimension relationships of the groove depth and particle size on the solids conveying mechanism of the helically grooved feed section. In the model, one or two shear interfaces were proposed based on the dimension relationships of the groove depth and particle size, and the solid-plug embedded in the groove and screw channel were divided into two or three layers by the shear interfaces to consider the solids conveying mechanism of each layer by the boundary condition equation for positive conveying. By the particle-size model, the effects of different dimension relationships on the transformation of solids conveying mechanisms between the friction-drag conveying and the positive conveying were discussed and compared with the on-line measuring experimental data. The results showed that the shear interfaces among the solids existed indeed and the dimension relationships determined the conveying mechanism and the throughput of helically grooved extruders, which was well confirmed by the excellent consistence between the predicted and measured data.

Studying the performance of fully encapsulated rock bolts with modified structural elements

Numerical simulation is a useful tool in investigating the loading performance of rock bolts.The cable structural elements(cableSELs)in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues.In this study,the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model.Furthermore,the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs.Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts.Based on the modified cableSELs,the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied.The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently.With the bolt diameter increasing,the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour.Moreover,after the rock bolt was loaded,the position where the maximum shear stress occurred was variable.Specifically,with the continuous loading,it shifted from the rock bolt loaded end to the other end.

Stability analysis of shallow tunnels subjected to eccentric loads by a boundary element method

This paper presents the results of the shear strength（frictional strength） of cemented paste backfillcemented paste backfill（CPB-CPB） and cemented paste backfillerock wall（CPB-rock） interfaces. The frictional behaviors of these interfaces were assessed for the short-term curing times（3 d and 7 d） using a direct shear apparatus RDS-200 from GCTS（Geotechnical Consulting ＆ Testing Systems）. The shear（friction） tests were performed at three different constant normal stress levels on flat and smooth interfaces. These tests aimed at understanding the mobilized shear strength at the CPB-rock and CPB-CPB interfaces during and/or after open stope filling（no exposed face）. The applied normal stress levels were varied in a range corresponding to the usually measured in-situ horizontal pressures（longitudinal or transverse） developed within paste-filled stopes（uniaxial compressive strength, s c 150 k Pa）. Results show that the mobilized shear strength is higher at the CPB-CPB interface than that at the CPB-rock interface. Also, the perfect elastoplastic behaviors observed for the CPB-rock interfaces were not observed for the CPB-CPB interfaces with low cement content which exhibits a strain-hardening behavior. These results are useful to estimate or validate numerical model for pressures determination in cemented backfill stope at short term. The tests were performed on real backfill and granite. The results may help understanding the mechanical behavior of the cemented paste backfill in general and, in particular, analyzing the shear strength at backfillebackfill and backfill-rock interfaces.

Brazed joints of CBN grains and AISI 1045 steel with AgCuTi-TiC mixed powder as filler materials

The brazing process of cubic boron nitride （CBN） grains and AISI 1045 steel with AgCuTi-TiC mixed powder as a filler material was carried out.The joining strength and the interfacial microstructure were investigated.The experimental results indicate that the spreading of the molten filler material on AISI 1045 steel is decreased with the increase of TiC content.A good interface is formed between the TiC particulates and AgCuTi alloy through the wetting behavior.In the case of AgCuTi＋16wt% TiC,the strength of the brazed steel-to-steel joints reached the highest value of 95MPa dependent upon the reinforcement effect of TiC particles within the filler layer.Brazing resultants of TiB2,TiB,and TiN are produced at the interface of the CBN grains and the AgCuTi-TiC filler layer by virtue of the interdiffusion of B,N,and Ti atoms.

Effects of Materials of Cementless Femoral Stem on the Functional Adaptation of Bone

The objective of this paper is to identify the effects of materials of cementless femoral stem on the functional adaptive behaviors of bone. The remodeling behaviors of a two-dimensional simplified model of cementless hip prosthesis with stiff stem, flexible ＇iso-elastic＇ stem, one-dimensional Functionally Graded Material （FGM） stern and two-dimensional FGM stem for the period of four years after prosthesis replacement were quantified by incorporating the bone remodeling algorithm with finite element analysis. The distributions of bone density, von Mises stress, and interface shear stress were obtained. The results show that two-dimensional FGM stem may produce more mechanical stimuli and more uniform interface shear stress compared with the stems made of other materials, thus the host bone is well preserved. Accordingly, the two-dimensional FGM stem is an appropriate femoral implant from a biomechanical point of view. The numerical simulation in this paper can provide a quantitative computational paradigm for the changes of bone morphology caused by implants, which can help to improve the design of implant to reduce stress shielding and the risk of bone-prosthesis interface failure.