Numerical simulation: The dynamic behavior of reinforced concrete plates under normal impact

This investigation deals with the use of the finite element method on the reinforced concrete structural dynamic response and failure behavior when subjected to the projectile impacts of different velocities, using the test conducted in [S.J. Hanchak, M.J. Forrestal, E.R. Young, J.Q. Ehrgott, Perforation of concrete slabs with 48 MPa (7 ksi) and 140 MPa (20 ksi) unconfined compressive strengths, Int. J. Impact Eng. 12 (1992) 1–7]. The Johnson–Holmquist concrete material constitutive law model is employed to simulate the large strains, high strain states and high pressures to which the concrete is subjected. The projectile impact velocity ranges from 381 m/s to 1058 m/s. Numerical simulations demonstrate that the Johnson–Holmquist concrete material constitutive model can describe the different failure modes without any predefined defects in the element mesh, and normally obtain good agreement between the numerical simulations and test results.     

基于碳纤维复合材料的月基极紫外相机照准架结构设计

为了减少月基极紫外相机的质量并保证相机的二维转动机构在卫星发射、地月变轨及月表着陆过程中受到大量级振动冲击以及月表超大温差环境下能正常工作,设计并研制了基于碳纤维复合材料（CFRP）的照准架结构。首先,设计了基于金属材料和CFRP的不同照准架结构,通过有限元法对不同材料的照准架进行分析对比,证明了CFRP照准架的优越性。温度和力学验证试验表明：基于CFRP的照准架质量小于其它材料的照准架,其刚度和热稳定性能满足极紫外相机环境适应性的要求。     

A stochastic-structurally based three dimensional finite-strain damage model for fibrous soft tissue

A fully three dimensional finite-strain damage model for fibrous soft tissue is developed. The model assumes uncoupled contributions for the matrix and collagen fibers, and uncoupled bulk and deviatoric response over any range of deformations. A simple isotropic damage mechanism within the framework of continuum damage mechanics has been used to describe the softening behavior under deformation for the matrix. On the other hand, statistical aspects related to the length distribution of the reinforcing fibers lead to a damage model for the reinforcing material. As a result, a general theoretical framework for constitutive modeling of biological soft tissue with continuum damage is obtained. A theoretical example consisting of a biaxial test of a soft tissue reinforced with two families of collagen fibers has been considered to demonstrate the capabilities of the proposed model and to study the sensitivity to changes in the statistical parameters associated with the reinforcing material. Also, a preliminary numerical example is included to demonstrate the model on a inhomogeneous boundary value problem. Results show that the model is able to capture the typical stress-strain behavior observed in fibrous soft tissue and seems to confirm the soundness of the proposed formulation.     

钢筋混凝土连续梁结构非弹性内力分析

本文在试验研究的基础上分析了纲筋混凝土连续梁结构内力的非弹性特性,并指出目前国际上的两种极限设计法,即“部分极限设计法”和“完全极限设计法”所存在的问题。文中把纲筋混凝土连续梁内力发展的全过程归结为三个不同性质的阶段。第二个阶段,也即因裂矮而引起内力的非弹性重分布,是非弹性分析中的一个重要环节,可按建议的“虚梁法”进行简便计算,按照试验资料还分析了传统线弹性方法的误差。对完全非弹性分析所需的两个关键荷载——开裂荷载和塑性铰荷载的计算方法也进行了分析。     

Stress relaxation of large amplitudes and long timescales in soft thermoplastic and filled elastomers

We propose a model for describing mesoscale relaxation mechanisms in soft thermoplastic elastomers and also in the high-temperature regime of filled rubbers. The model consists of hard spheres embedded in an elastic matrix. It is solved by dissipative particle dynamics. We study the response of the model to deformations of various amplitudes. We show that it displays slow relaxation processes of large amplitudes that are related to irreversible reorganizations at a mesoscopic scale. We characterize these reorganizations as buckling of instabilities that change the local environment of the hard inclusions. Paper presented at the 3rd Annual Rheology Conference, AERC 2006, April 27–29, 2006, Crete, Greece.     

钢筋混凝土柱壳的非线性分析

混凝土受拉开裂及多向压力作用下混凝土的非线性应力－应变关系是产生钢筋混凝土结构非线性反应的两个主要原因，据此建立混凝土破坏的一般准则，用这些准则建立非线性有限元分析的应力－应变增量关系，对于钢筋混凝土构件的有限元分析，文中介绍的方法可以直接考虑钢筋的作用，钢筋和混凝土两种不同材料的应力－应变关系可以分别考虑，便于有限元计算程序的编制。     

若干无机缓蚀剂对混凝土中钢筋的阻锈作用

通过含NaCl介质溶液的浸泡实验,利用电化学实验检测技术,观测和比较了NaNO2等8种无机缓蚀剂添加于混凝土中对钢筋的阻锈作用,结果表明,在本实验条件下,NaNO2等缓蚀剂对钢筋明显的阻锈作用,在pH=9.50％,含10％NaCl的混凝土模拟液中,外加NaNO2后,混凝土中钢筋的腐蚀电位正移,腐蚀电流可下降至未加缓蚀剂的1／6,缓蚀剂的加入不同程度地提高了钢筋耐点蚀的性能。     

纤维增强塑料(FRP)在混凝土结构中的应用——FRP材料性能与发展

简要地介绍了纤维增强塑料（FRP）发展历史,生产过程及其优点,总结了常用类型的FRP在短期与长期荷载作用下的力学性能,并给出了作者在试验中得到的拉伸强度,弹性模量,松弛及徐变系数。此外,文中还提出了一个预测由芳纶纤维和环氧树脂组成的AFRP束长期徐变系数的方程。