The Finite Analysis of Deformation and Stress Triaxiality of a Mixed I + II Mode Elastic-Plastic Crack Tip

The deformation and distribution of stress triaxiality σ_{_m}/σ of mixed I + II mode elastic-plastic cracks under plane strain and plane stress conditions were analysed by the large strain finite element method and were compared with the HRR field. The results show that, (1) the model of crack-tip deformation under mixed I + II mode loading is sharpening-blunting, the sharpening and blunting deformation is acted on by compressive stress (σ_{_m}/σ > 0) and tensile stress (σ_{_m}/σ > 0), respectively; (2) in the plane strain case, the (σ_{_m}/σ)_{_max} of the real crack tip decreases with an increase of mode II component, but increases with an increasing strain hardening n for every mixed ratio. For the loading of K_{_I}/K_{_II} > 0.5, the (σ_{_m}/σ)_{_max} value of the real crack tip is less than that of the (σ_{_m}/σ)_{_max} given by the HRR field, but the opposite holds true cases where K_{_I}/K_{_II} > 0.5; (3) in the plane stress case, the (σ_{_m}/σ)_{_max} decreases a few values with an increasing mode II component, the values of (σ_{_m}/σ)_{_max} of every mixed ratio are far less than these of the corresponding loading condition in the plane strain case. In the plane stress case, the (σ_{_m}/σ)_{_max} values of every mixed ratio for any strain hardening exponent n are almost constant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Theoretical-Experimental Analysis of Structural Components Separation upon Local Impulse Loading

Separation of structural components is considered as a high-speed directed local destruction of an object in the area of a specially applied concentrator. Elements in the form of plates and shells of arbitrary curvature have been taken as destruction objects. Calculations have been made by explicit finite-element methods. Results of the investigation performed have found practical applications.     

人造板上下料机械手的动力学分析及仿真

目的 实现包装生产线上的自动化搬运作业,全面系统地了解人造板上下料机械手的动态特性,探究该机械手各关节所需驱动力大小及变化规律。方法 建立人造板上下料的三维结构模型,制定机械手一周期内的运动流程,通过拉格朗日方程法对机械手进行建模,通过系统动力学仿真软件(Adams)仿真出机械手的动态特性并验证动力学模型的准确性。结果 得到了机械手各关节(角)速度、(角)加速度、力与力矩变化曲线,(角)速度变化平缓无突变,(角)加速度、力与力矩曲线在6～9 s时变化剧烈,仿真曲线与动力学模型数据基本拟合。结论 动力学模型建立正确,后续应优化驱动或通过结构优化方式使整个运动过程更加平稳。     

Finite Element Analysis and Experimental Measurement of Deformation Behavior for NiTi Plate With Stress Concentration Part Under Uniaxial Tensile Loading

Abstract: The aim of this study is to verify the effectiveness of ordinary phenomenological constitutive relation of NiTi shape memory alloy under mechanical loading at a constant temperature, sufficiently. First, finite element analysis is performed by using ordinary phenomenological constitutive relation for rectangular plate with double notch under tensile loading at a constant temperature. Next, uniaxial tensile loading is carried out for 50.5Ni49.5Ti rectangular plate with double notch. At the same time, macroscopic stress–strain curve and local strain distribution are measured by using in‐house measurement system on the basis of digital image correlation. As a result, it is found that the stress–strain curve obtained from finite element analysis is much different from those obtained experimental measurement, especially during stress‐induced martensite transformation. The result can be derived from the phenomena of local strain band behavior arising in NiTi under mechanical loading. The phenomenological constitutive model used in present finite element analysis is constructed under assumptions that the material has isotropic characteristics and shows homogeneous deformation. However, this experimental result suggests that the material itself has anisotropy microscopically. Furthermore, material shows unique inhomogeneous deformation. Also, there is possibility that these anisotropic characteristic and inhomogeneous deformation behaviour may derive from its microstructure. In future, to sufficiently describe the macroscopic stress–strain curve of NiTi we should take into consideration the material microstructure.     

Static Analysis of Laminated Composite Plates Using n-Order Shear Deformation Theory and a Meshless Global Collocation Method

In this article, an n-order shear deformation theory is used to analyze the static characteristic of laminated composite plates. The third-order theory of Reddy can be considered as a special case of present n-order theory (n = 3). Governing equations and boundary conditions expressed in terms of strong form based on the present n-order theory are discretized by a meshless global collocation method. Maximum deflection and stress of the simply-supported laminated plate under sinusoidal load are compared with available published results, which demonstrate the accuracy and efficiency of present n-order theory.     

RZZY6000型装药机的常见故障分析与对策

文章介绍了RZZY6000型装药机的结构及工作原理，并针对灌装机过载、热合膜的安装与输送、药量的稳定性、药卷的封口质量、热合膜切刀故障、药卷破损等几个方面进行了分析与改进，有效地降低了设备的故障率，并使产能稳定在2t／h以上，装药精度控制在±40g以内，提高了设备的使用效率。实践表明该装药机是一种高效的塑膜装药机。     

Analysis of Boundary-Value Problems of the Theory of Small Elastoplastic Strains,which Allows for Hydrostatic Stress and Stress Deviator Type

The author considers some versions of the deformation theory of plasticity, which takes into account the influence of hydrostatic stress and stress deviator type on the mechanical properties of a medium for the case of proportional loading. The emphasis is on the generalized statement of a nonlinear boundary-value problem and investigation of its solvability. Conditions have been determined that ensure the existence, uniqueness, and continuous dependence of the generalized solution on the loads applied.__________Translated from Problemy Prochnosti, No. 2, pp. 107 – 135, March – April, 2005