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上海交通大学学报 2004年第Z2期38卷 38-41页

作者： liu xiequan Ni Xinhua Zhao Jianjun Shijiazhuang Mechanical Engineering College Shijiazhuang050003 China Shijiazhuang Mechanical Engineering College Shijiazhuang050003 China Shijiazhuang Mechanical Engineering College Shijiazhuang050003 China

The plane structure of bars jointed to a rigid-body is a complex and universal *** other structure of bars can be considered as its special cases. Many material have different stress-strain relation in tension and compression, generally the relation is nonlinear. In this paper,we use the constitutive model of linearly elastic and power hardening of strength difference to analyze plane structure of bars. The displacement method is used to derive the universal expression of calculating stress and strain. The nonlinear equations for computing displacements of the rigid-body has been given and general computing program has been worked out. This problem has been solved satisfactorily.

关键词： strength-difference linearly elastic power hardening the plane structure of bars stress strain

Damage and fracture model for eutectic composite ceramics

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Acta Mechanica Sinica 2019年第1期35卷 190-200,I0006页

作者： Jinfeng Yu Xinhua Ni xiequan liu Yunwei Fu Zhihong Du Department of Vehicle and Electric Engineering Army Engineering UniversityShijiazhuang 050003China Army Infantry College Nanchang 330000China Xichang Satellite Launch Center Xichang 615000China

Study of damage and fracture models to analyze the fracture mechanism of eutectic composite ceramics is of considerable importance because no accurate fracture models are available for these materials. Eutectic composite ceramics are composed of microcells with random direction. We present herein a model that predicts the damage and fracture of eutectic composite ceramics based on analysis of defect stability and the damage localization band. Firstly, given the microstructure of eutectic composite ceramics, a mesodomain and a microcell model are constructed. The local stress field in the mesodomain is then analyzed based on the interaction direct derivative estimate. Secondly, the stability of a defect around particles in a microcell is analyzed, and the stress intensity factor of an annular defect under the applied stress field and the residual stress field in the particle are calculated. The stress intensity factor of a defect is controlled by the residual stress when the defect extension is small. However, it is controlled by the applied stress when the defect extension is large. Finally, a model for the damage localization band at the crack tip is constructed based on the Dugdale-Barenblatt model. The residual intensity is the important factor affecting the length of the damage localization band. When the damage variables reach their largest value, the residual in ten sity and the length of the damage localization band attain their minimum value. This work provides the theoretical basis for further study of the damage mechanics of eutectic composite ceramics and guides the engineering applications of these materials.

关键词： Microcell Interaction direct derivative estimate Defect stability Damage localization band

Strength-Toughening Model of Eutectic Ceramic Composite with Inherent Defects

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Chinese Journal of Mechanical Engineering 2014年第4期27卷 754-760页

作者： FU Yunwei ZHANG Long NI Xinhua liu xiequan CHEN Cheng ZHAO Siyuan Department of Vehicle and Electric Engineering Ordnance Engineering College Department of Ground Artillery Wuhan Ordnance Non-commissioned Officers Academy

Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in theoretical models. This incompleteness in the parameter chosen fails to explain the mechanism of failure in composite ceramics. The exponential toughness function is used to represent the pull-out toughening mechanism, which dominates the crack growth resistance curve（R-curve）. The strengthening-toughening model is established based on the Mori-Tanaka method（M-T method）. The influence of inherent defects on toughness function and strength is analyzed by using this model. The theoretical result is compared with the experiment data. This model exactly reflects the change in strength. The theoretical result indicates that defects change the toughness function. Moreover, micro-cracks increase toughness size ac, and the strength of crack instable extensions acutely decreases as defect content increases. This presented model establishes the relationship among the important mechanical parameters of defect, strength, elastic modulus, and the R-curve.

关键词： inherent defects pull-out toughening toughness function strength

The Fracture Strength of Eutectic Composite Ceramic Containing lamellar inclusion

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The Fracture Strength of Eutectic Composite Ceramic Containi...

2012年海峡两岸破坏科学/材料试验学术会议

作者： Xinhua Ni Cheng Chen xiequan liu Shuqin Zhang Department of Basic Course Mechanical Engineering College

Eutectic composite ceramic containing lamellar inclusion possessed good strengths at room temperature and high ***,under the conditions that the matrix,interphase and the lamellar inclusions are isotropic,the size dependent micromechanical stress field of the composites can be ***,stress concentration generated by the dislocation pile-up in interphase was analyzed,and the maximum stress in the matrix was *** the maximum stress is equal to the breaking strength of the matrix in molecular theory,the ultimate shear stress of the composites can be ***,the analytic expression of the eutectic composite ceramics can be obtained based on the relationship between shear stress and the *** result shows that the fracture strength of such composite ceramics had obvious size dependence.

关键词： Eutectic Composite Ceramic lamellar inclusion Micromechanical Stress Field Fracture Strength size dependence

Residual Stress Field and Toughening Mechanism for Composite Ceramic with Eutectic Interphases

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Residual Stress Field and Toughening Mechanism for Composite...

2012年海峡两岸破坏科学/材料试验学术会议

作者： xiequan liu Yunwei Fu Xinhua Ni Baohong Han Department of Basic Course Mechanical Engineering College

The four-phase-model method is used to study residual stress field of composite ceramic with eutectic *** matrix,Interphase and fiber inclusion are isotropy, the residual stress distribution of composite ceramic with eutectic interphase is *** size dependence of residual stresses is *** residual-stress-field in the eutectic ceramic rod relates to the stiffness,thermal expansion coefficients,shape and volume content of inclusions and interphases in the eutectic ceramic *** basis of the residual-stress-field in the eutectic ceramic rod,the frictional force on the boundary of the eutectic ceramic rod can be *** the frictional work is *** toughening mechanism of residual stresses is *** result shows that the toughening value is dependent on the size of fiber inclusion in the eutectic rod.

关键词： Eutectic Ceramic Rod Fiber Inclusion Residual Stress Field Toughening Mechanism Size Dependence

Study for the Parallel Degree Measure of the Rocket Gun’s Orientation Tubes

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Study for the Parallel Degree Measure of the Rocket Gun’s O...

ICEMI'2005第七届国际电子测量与仪器学术会议

作者： liu xiequan liu Jin Han Daizhao (Mechanical Engineering College Shijiazhuang 050003 China)

This article puts forwards the contents of measuring the parallel degree of rockets gun’s orientation tubes, formulates the general guiding idea of making use of the laser collimator technology to hav

关键词： Rocket gun orientation tube parallel degree measurement.

The Stress-Strain Analysis for Strength Difference Plane Structure of the Pin-jointed Bars

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The Stress-Strain Analysis for Strength Difference Plane Str...

The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational Mechanics

作者： Xinhua Ni , xiequan liu Mechanical Engineering College, Shijiazhuang, 050003, China

A plane structure of the pin-jointed bars is considered. For i-th bar, the length is li the cross-sectional area is Ai and the orented angle is aaaaaaaaaai. The applied forces are Px and Py. The constitutive relation can be written *** n1 and n2 are the hardening coefficients in tension and compression respectively. CL and CY are constants of material in tension and *** the horizontal and the vertical displacements of the joint are u and v respectively, deformations of i-th bar can be expressed out as: △ali = -u cos αi- v sin αiThus the strain, stress and axial force of the bar are obtained Equilibrium equations at the joint can be determined from staticWe know that the expressions are a group of nonlinear equations of u and v. u and v can be figured out, then the strain and axial force of i-th bar will be obtained Above equations may be transformed toThe nonlinear equations may be solved by descending method. Define the aim function:F(u,v)=f12(u,v)+f22(u,v)Evidently, if F(u ,v )≤ξ, u and v will be thought of as a group of solutions of the equations that are satisfied for precision .The constitutive relation of materials was referred to as strength difference and nonlinearly elastic formulation, it is the more general term. Exa mple, if CL=CY and n1=n2 it will be transformed to strength same and nonlinearly elastic. If n1=n2=1, it will be transformed to elastic modulus difference and linearly elastic model. If CL-CY and nl=n2=1, it will be transformed to strength same and linearly elastic model.

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The Elastic and Plastic Analysis for the Linearly Elastic and Power Hardening Structure of the Pin-Jointed Bars

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The Elastic and Plastic Analysis for the Linearly Elastic an...

The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational Mechanics

作者： xiequan liu , Xinhua Ni Mechanical Engineering College, Shijiazhuang, 050003, China

A structure of pin-jointed bars is considered. For i-th bar, the length is li, the cross-sectional area is Ai. The oriented angles of the unit vector ri along i-th bar about three coordinate axes x, y, z are αi,βi,γi respectively. Applied forces acted on the joint are Px, Py, Pz. The constitutive relation can be assumedIf the displacements of the joint along three coordinate axes are u, v and w, deformation of i-th baris can be expressed out asThus the strain, stress and axial force of the bar can be *** equations of the joint can be determined from staticWe know that the expressions are a group of nonlinear equations of u, v, w. u, v, w can be figured out, then the strain, stress and axial force of i-th bar will be obtained. Above equations may be transformed toThe nonlinear equations may be solved by descending *** the aim function: F(u,v,w)=f12(u,v,w)+f22(u,v,w)+f32(u,v,w)Evidently, if F(u ,v ,w )≤ξ, (w , v , w) will be thought as a group of solutions that are satisfied for precision ξ.It is the more general term that constitutive relation of materials was referred to as linearly elastic and power hardening formulation. Example, if σs=∞, it will be transformed to linearly elastic model;If σs=0, it will be transformed to power hardening function. If n =1, it will be linearly hardening elastic-plastic model. If E2=0, it will be perfectly elastic-plastic model.

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颗粒增强镍基合金热膨胀系数预报

稀有金属材料与工程 2005年第Z1期34卷 273-274页

作者：刘协权倪新华路晓波军械工程学院河北石家庄050003 军械工程学院河北石家庄050003 军械工程学院河北石家庄050003

使用Eshebly-Mori-Tanaka方法研究了由陶瓷粒子引起的本征应变和扰动应变.研究结果表明,陶瓷粒子和镍基合金的热膨胀系数差异越大,则本征应变和扰动应变也越大,本征应变和扰动应变与陶瓷粒子和镍基合金的体积分数及弹性常数有关.

关键词：镍基合金陶瓷粒子 Eshebly-Mori-Tanaka方法热膨胀系数

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纳米共晶晶须复相陶瓷的刚度预报

稀有金属材料与工程 2005年第Z1期34卷 597-599页

作者：倪新华刘协权赵忠民军械工程学院河北石家庄050003 军械工程学院河北石家庄050003 军械工程学院河北石家庄050003

用SHS技术制备的纳米共晶晶须复相陶瓷具有较大的断裂韧性和较高的塑性形变行为,其组织结构以纳米共晶晶须为基体.运用Mori-Tanaka方法研究了复合共晶晶须的等效本征应变,并得到了复合共晶晶须的应力应变关系.通过应力应变关系计算出复... 详细信息

用SHS技术制备的纳米共晶晶须复相陶瓷具有较大的断裂韧性和较高的塑性形变行为,其组织结构以纳米共晶晶须为基体.运用Mori-Tanaka方法研究了复合共晶晶须的等效本征应变,并得到了复合共晶晶须的应力应变关系.通过应力应变关系计算出复合共晶晶须的刚度,复合共晶晶须为横观各向同性,具有5个独立的弹性常数.根据复相陶瓷的应变均值,考虑复合共晶晶须方位的随机性,计算出材料的有效弹性模量和泊松比,复相陶瓷材料为各向同性体.

关键词：纳米共晶晶须刚度预报 Mori-Tanaka方法横观各向同性各向同性