基于区域性等段数剖分方法的轮胎断面有限单元网格的自动生成

在已形成轮胎断面结构图的基础上 ,用有限单元法并依据轮胎断面结构特点 ,采用区域性等段数剖分方法实现了轮胎断面有限单元网格的自动生成 ,获得了单元信息。并对区域性等段数剖分方法及有限单元网格的生成过程及网格剖分结果进行了分析。     

基于八节点二次壳单元的等效结构应力法

基于八节点二次壳单元的节点力和节点力矩,导出了焊趾截面上的分布线力与分布线力矩,进而分别针对闭合焊缝和非闭合焊缝对线力和线力矩进行了单元集成.以T型焊接接头为研究对象,验证了基于八节点二次壳单元的焊趾结构应力对单元类型与网格尺寸的不敏感性,并根据已有结果验证了其有效性.对RHS管接头T型焊缝两条焊趾的结构应力进行了计算,发现若圆弧拐角处的网格过于稀疏将引起单元中间节点的结构应力产生较大波动,该问题可以通过网格加密得以解决;利用等效结构应力与主S-N曲线,对RHS管接头的疲劳失效位置与疲劳寿命进行了预测,数值结果与实验测试数据基本吻合.     

全级配混凝土随机骨料二维模型生成的块体切割方法

混凝土细观力学数值模拟分析所得到的结果与混凝土实际力学性能之间的差异大小,在很大程度上取决于所采用的混凝土骨料模型是否合理.目前,混凝土随机骨料的二维模型生成算法以生长法为主,所生成的骨料几何形态具有较大的局限性,且不便于推广应用至三维问题.研究并提出了一种新的随机骨料二维模型生成方法——块体切割法.首先,引入一组随机平面,并假定其方向及位置符合某种概率分布;然后,基于瓦拉文公式推导出随机平面的相关参数的概率密度函数;最后,通过随机平面切割初始块体,得到不同料径和形状的随机骨料.算例分析结果表明,本方法能够生成符合级配要求的随机骨料,可进一步推广至三维问题.     

基于Ansys的混凝土随机骨料模型及细观力学分析

基于Ansys平台,采用APDL命令流,对Ansys进行2次开发,实现了从二维随机骨料投放、有限元网格划分,到施加荷载、分析求解,再到结果输出全过程可视化研究,有效避免了建模软件与有限元数值分析软件之间参数传递关系复杂、接口程序编制困难、兼容性差等问题;提出了利用骨料面积参数和布尔运算判断骨料之间的相容性,使建模更为准确、高效和简便,同时也为建立三维随机骨料模型提供了新的思路;采用骨料偏移算法,生成骨料与砂浆基质之间的薄弱界面,方法可靠;采用所提出的方法生成混凝土随机骨料模型,基于损伤力学理论,开展混凝土细观力学研究.结果表明所提出的方法可行且高效.     

A new method of estimating the equivalent elastic modulus of RCCD

Based on the composite material mechanic theory,the analysis method for the equivalent elastic moduli which are parallel and vertical to the construction interface of RCCD is studied in this paper.The differences between the equivalent elastic moduli which are vertical to the construction interface of RCCD gotten from different methods are discussed in detail.The variation range of the equivalent elastic modulus which is vertical to the construction interface of RCCD is studied based on the principle of minimum complementary energy and the principle of minimum potential energy.The effect of the related influential factors on the equivalent elastic modulus is analyzed.The estimation formula of the equivalent modulus which is vertical to the construction interface of RCCD is proposed.The feasibility of the approach proposed in this paper is analyzed through an example.     

A new method of estimating the equivalent elastic modulus of RCCD

Based on the composite material mechanic theory, the analysis method for the equivalent elastic moduli which are parallel and vertical to the construction interface of RCCD is studied in this paper. The differences between the equivalent elastic moduli which are vertical to the construction interface of RCCD gotten from different methods are discussed in detail. The variation range of the equivalent elastic modulus which is vertical to the construction interface of RCCD is studied based on the principle of minimum complementary energy and the principle of minimum potential energy. The effect of the related influential factors on the equivalent elastic modulus is analyzed. The estimation formula of the equivalent modulus which is vertical to the construction interface of RCCD is proposed. The feasibility of the approach proposed in this paper is analyzed through an example.     

粗骨料体积分数对混凝土弹模和抗压强度的影响

为了研究粗骨料体积分数对早龄期混凝土弹性模量和轴心抗压强度发展的影响,本文针对水胶比为0.62、0.43和0.3的三种混凝土分别设计了粗骨料体积分数逐渐增大的系列混凝土配合比．保持混凝土的砂浆各组分不变,粗骨料体积分数从零逐渐增大,同一水胶比的系列混凝土28 d静力抗压弹性模量随粗骨料体积分数增大而单调显著增大,而其轴心抗压强度则呈现“先减小、后增大”的变化规律且变化趋势相对平缓．环境干燥下混凝土内部可蒸发水散失将降低水泥水化程度,混凝土的弹性模量和轴心抗压强度均低于密封养护下的同期值;水胶比越大,环境干燥的影响越大．本研究建议的基于水泥水化度发展预测混凝土弹性模量和抗压强度的模型,对不同水胶比、不同粗骨料体积分数、不同养护条件均适用,试验值和模型值吻合良好．     

轻集料取代碎石对混凝土强度和弹性模量影响的研究

利用轻集料与碎石集料混合配制混凝土,可使混凝土的性能得到优化,该类混凝土已显示出较好的应用前景.通过研究轻集料取代碎石对混凝土强度和弹性模量影响规律,确定了轻集料取代率与混凝土密度、弹性模量之间的定量关系,探讨了轻集料取代碎石对混凝土极限应变的影响,提出通过集料混合调控混凝土弹性模量、提高混凝土极限应变和抗拉能力的技术思路,为新型轻质高性能混凝土的研究提供了有益的参考.     

轻集料取代碎石对混凝土强度和弹性模量影响的研究

利用轻集料与碎石集料混合配制混凝土,可使混凝土的性能得到优化,该类混凝土已显示出较好的应用前景.通过研究轻集料取代碎石对混凝土强度和弹性模量影响规律,确定了轻集料取代率与混凝土密度、弹性模量之间的定量关系,探讨了轻集料取代碎石对混凝土极限应变的影响,提出通过集料混合调控混凝土弹性模量、提高混凝土极限应变和抗拉能力的技术思路,为新型轻质高性能混凝土的研究提供了有益的参考.     

Design and preparation of high elastic modulus self-compacting concrete for pre-stressed mass concrete structures

Requirements of self-compacting concrete (SCC) applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be satisfied by ordinary SCC. In this study, in order to solve the problem, a few principles of SCC design were proposed and the effects of binder amount, fly ash (FA) substitution, aggregate content and gradation on the workability, temperature rise, drying shrinkage and elastic modulus of SCC were investigated. The results and analysis indicate that the primary factor influencing the fluidity was paste content, and the main methods improving the elastic modulusof SCC were a lower sand ratio and an optimized coarse aggregate gradation. Lower adiabatic temperature rise and drying shrinkage were beneficial for decreasing the cement content. Further, based on the optimization of mixture, a C50 grade SCC (with binder amount of only 480 kg/ m3, fly ash substitution of 40%, sand ratio of 51% and proper coarse aggregate gradation (V _{5-10 mm}: V _{10-16 mm}: V _{16-20 mm}= 30%: 30%:40%)) with superior workability was successfully prepared. The temperature rise and drying shrinkage of the prepared SCC were significantly reduced, and the elastic modulus reached 37.6 GPa at 28 d.     

硫酸盐环境混凝土动弹性模量及微观研究

针对西部重盐渍土地区混凝土的耐久性问题,以内掺复合掺合料制成的高性能细石混凝土和普通硅酸盐水泥以及抗硫酸盐水泥制成的高性能细石混凝土作为研究对象,在硫酸钠溶液中进行干湿循环后,通过对动弹性模量的测量以及对混凝土SEM形貌分析,结果表明,在干湿交替的恶劣环境中,抗硫酸盐水泥混凝土的抗侵蚀性能并不比普通水泥混凝土好;掺加复合掺和料的高性能细石混凝土对硫酸盐侵蚀有较好的抵抗性能;掺加矿物掺合料能够与混凝土内部的不利成分Ca(OH)2发生二次水化反应,生成有利的C-S-H凝胶,有效改善混凝土的微观结构;并给出了在盐渍土地区拌制混凝土的建议.     

细观力学能量等效模量方法与微极弹性力学

夹杂多相复合体的能量等效模量介质，是细观力学研究脆性材料损伤的主要方法之一．通过研究细观结构变化的物理和力学过程，引入某种平均化方法寻出材料的宏观性质．从宏观唯象角度引入各阶张量形式的连续场变量研究夹杂复合体的损伤，目前尚属空白．本文将夹杂多相复合体同引入内部结构的微极介质等效，通过微极弹性力学中的应力(σ)、力偶应力张量(m)和Helmholtz自由度密度φ，给出了描述夹杂多相复合体损伤的等效模量解析表达式．将取决于各相几何、物理性质和平均化方法的平均应变柔度张量用与连续分布场张量m相关的柔度张量代替．