为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立...为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.展开更多
An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in ...An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in this article.The proposed sandwich structure consists of skins of FGM layers and an FGCNTRC core.This structure possesses all the advantages of FGM and FGCNTRC,including high electrical or thermal insulating properties,high fatigue resistance,good corrosion resistance,high stiffness,low density,high strength,and high aspect ratios.Such sandwich structures can be used to replace conventional FGM structures.The present formulation has been established by using an improved meshfree MK method and the first-order shear deformation shell theory(FSDT).The effective material characteristics of the FGM-skin layers and the FGCNTRC core were calculated using the rule of mixture.Key parameters and factors such as the thickness-to-radius ratio,the length-to-radius ratio,layer-thickness ratios,CNT distributions,the volume fraction of CNTs,the power-law index,and various boundary conditions were rigorously investigated.A nonlinear CNT distribution that we term FG-nX is first proposed in this work,and many new results of FGM-FGCNTRC sandwich shells have been provided.展开更多
本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of se...本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of second-order statistics from dependent random samples with FGM Copula. Sufficient conditions are established on the usual stochastic order, the increasing convex order and the increasing concave order for the second-order statistic. And some numerical examples are provided to illustrate the theoretical results.展开更多
The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte C...The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte Carlo simulation(MCS), so-called refined stochastic finite element method to investigate the random vibration of functionally graded material(FGM) plates subjected to the moving load.The advantage of the proposed method is to use r-FSDT to improve the accuracy of classical FSDT, satisfy the stress-free condition at the plate boundaries, and combine with MCS to analyze the vibration of the FGM plate when the parameter inputs are random quantities following a normal distribution. The obtained results show that the distribution characteristics of the vibration response of the FGM plate depend on the standard deviation of the input parameters and the velocity of the moving load.Furthermore, the numerical results in this study are expected to contribute to improving the understanding of FGM plates subjected to moving loads with uncertain input parameters.展开更多
文摘为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.
文摘An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in this article.The proposed sandwich structure consists of skins of FGM layers and an FGCNTRC core.This structure possesses all the advantages of FGM and FGCNTRC,including high electrical or thermal insulating properties,high fatigue resistance,good corrosion resistance,high stiffness,low density,high strength,and high aspect ratios.Such sandwich structures can be used to replace conventional FGM structures.The present formulation has been established by using an improved meshfree MK method and the first-order shear deformation shell theory(FSDT).The effective material characteristics of the FGM-skin layers and the FGCNTRC core were calculated using the rule of mixture.Key parameters and factors such as the thickness-to-radius ratio,the length-to-radius ratio,layer-thickness ratios,CNT distributions,the volume fraction of CNTs,the power-law index,and various boundary conditions were rigorously investigated.A nonlinear CNT distribution that we term FG-nX is first proposed in this work,and many new results of FGM-FGCNTRC sandwich shells have been provided.
文摘本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of second-order statistics from dependent random samples with FGM Copula. Sufficient conditions are established on the usual stochastic order, the increasing convex order and the increasing concave order for the second-order statistic. And some numerical examples are provided to illustrate the theoretical results.
文摘The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte Carlo simulation(MCS), so-called refined stochastic finite element method to investigate the random vibration of functionally graded material(FGM) plates subjected to the moving load.The advantage of the proposed method is to use r-FSDT to improve the accuracy of classical FSDT, satisfy the stress-free condition at the plate boundaries, and combine with MCS to analyze the vibration of the FGM plate when the parameter inputs are random quantities following a normal distribution. The obtained results show that the distribution characteristics of the vibration response of the FGM plate depend on the standard deviation of the input parameters and the velocity of the moving load.Furthermore, the numerical results in this study are expected to contribute to improving the understanding of FGM plates subjected to moving loads with uncertain input parameters.
