细观结构参数对功能梯度压电板的力场和挠度场的影响

假定功能梯度压电材料的物性参数沿着厚度方向,按照幂函数、e指数函数及正弦函数3种不同的梯度模型分布,从三维电弹性耦合的基本方程出发,采用层合模型并利用状态变量法对功能梯度压电板的应力场和挠度进行分析.分别考虑作用机械荷载和电荷载,并且在此基础上分析了不同的材料组份和几何尺寸对功能梯度压电材料的板得力场和挠度场的影响,并对数值结果进行了对比分析研究.为功能梯度压电结构设计及材料优化提供一定参考依据.     

稳态热传导下功能梯度材料实心圆板的热响应分析

利用推广后的Main和Spencer功能梯度板理论,研究了横观各向同性功能梯度实心圆板在非均布温度场作用下的热弹性问题。采用该理论中的位移展开公式,在板厚度方向上考虑热传导引起的稳态温度场,材料常数和热传导率沿板厚方向可以任意连续变化。基于三维弹性理论,最终得到了功能梯度实心圆板在温度场作用下的热响应解答。通过数值算例分析,验证了该方法的正确性,另外还讨论了边界条件、材料梯度变化程度和板厚径比对功能梯度实心圆板热弹性响应的影响。     

基于有限元法的汽车A柱内板成形缺陷研究和工艺优化

起皱和开裂是汽车内板面临的两大主要问题.以某系列带有缺陷的A柱内板为例,采用有限元法模拟分析其冲压成形全过程.通过与实际零件起皱和开裂位置的对比,验证了该数值模型的可靠性.采用该有限元模型研究冲压件成形过程中材料流动的方向,结果表明,成形过程中板料流动受阻是该A柱内板产生起皱和开裂的主要原因.为解决某车型A柱内板表面缺陷的问题,提出在板材受阻位置切割一个三角形缺口的优化方法.相应的模拟结果表明,通过切割板材,可缓解板材流动受阻现象,该车A柱内板起皱和开裂现象得以解决.     

高强度热成形钢板冷却速率-强度-硬度预测

基于高强度钢板热成形平板模具分区冷却试验获得了淬火过程阶段冷却速度对机械强度-硬度的影响规律。采用量纲分析法建立了热成形材料冷却速率-机械强度-硬度指数模型,并验证了该模型的有效性。通过编制用户子程序将该模型引入自主开发的KMAS_HF软件平台中,实现了对典型U形热成形产品淬火后强度硬度的数值仿真预测。结果表明:该模型对热成形高强度钢淬火后机械性能仿真预测具有较好的适用性,为实现梯度硬度复合热成形工艺优化及产品性能分析提供了一种新的仿真分析流程。     

热载荷作用下含裂纹功能梯度板的有限元分析

为深入理解功能梯度材料的热断裂行为,研究了热载荷作用下任意热机械属性功能梯度材料板的裂纹尖端特性.利用解析方法推导了不含裂纹功能梯度板的温度场和热应力场,根据叠加法,把热应力场转化为裂纹表面载荷,采用基于非均匀单元的有限元方法计算分析了稳态热载荷下功能梯度板的裂纹尖端特性,并针对不同材料热机械属性分布形式,考察了热应力...     

汽车B立柱热成形性能数值模拟

高强度钢板在车身上的应用需求越来越大,针对其在冷成形工艺下容易发生破裂、起皱、回弹等现象,采用热成形工艺的方法提高高强钢板的塑性,并保证其成形后的强度.以材料为22Mn B5的汽车B立柱为例,对其热成形过程进行数值模拟分析.采用设置板料成形温度、模具初始温度、压边力大小及冲压速度大小的方法,并最终确定汽车B立柱热成形条件下最优的工艺参数配比.将热成形工艺下模拟的结果与冷成形工艺进行对比,最终验证了热成形工艺的优越性.     

带压电层功能梯度悬臂板非线性动力学分析

分析了在热环境条件下受横向栽荷作用的、带压电功能梯度材料悬臂板的非线性动力学问题。基于vonKarman理论和Reddy一阶剪切变形理论,推导出了带压电功能梯度悬臂板的动力学方程。利用Galerkin法对偏微分方程进行离散,对离散后的方程进行数值模拟,分析中考虑了组分材料热物参数对温度变化的依赖性,讨论了材料组分指数、控制电压对系统非线性动力学行为的影响,结果表明正电压减小了板的振幅,负电压增大了板的振幅,而随着材料体积分数指数的增大,板的振幅也在变大。     

拼焊板成形过程控制参数优化设计

为解决拼焊板（TWB）成形数值模拟中的强非线性问题并消除计算噪声效应，提出了一种基于近似优化技术的最佳成形过程参数求解方法.采用响应面方法（RSM）构造每次优化迭代的目标和约束逼近曲面，逐次迭代收敛得到全局最优解.借助空间映射（SM）技术的代理模型求解响应面和相关优梯度，利用一个精细模型为下一优化迭代修正设计点.选取拉延筋成形阻力和压边力控制参数为设计变量，选取成形极限图（FLD）标准为约束条件，建立最小化焊缝偏移量为目标函数的优化模型.优化计算结果表明，该方法能有效求解拼焊板成形过程参数，使焊缝有害偏移量减少75%以上.     

梯度热障涂层服役条件下的蠕变响应分析

利用数值方法研究了陶瓷/金属梯度功能热障涂层在服役条件下的热-力响应,同时考虑了梯度功能热障涂层各层的蠕变现象,数值研究表明在对梯度功能热障涂层进行热-力响应分析过程中,材料的蠕变现象是不能够忽略的,即使该层材料是富陶瓷材料。     

DQM求解功能梯度圆板轴对称线性弯曲问题研究

基于一阶剪切变形板理论,研究了功能梯度圆板在均布机械载荷作用下的轴对称线性弯曲问题.假设功能梯度材料性质只沿板厚方向变化,且服从幂函数规律,推导了该问题的控制方程,考虑固支边界条件,用微分求积法对其进行数值求解.利用求解结果讨论了功能梯度材料的梯度参数、板厚半径比对圆板线性弯曲的影响.     

地下水除锰的生物作用试验

目的 研究微生物在锰砂滤层去除地下水中所含的铁、锰过程中所起的作用。为生物法用于地下水除铁除锰的初期启动和生产运行提供依据．方法 试验分为两个阶段，第一阶段。在相同外界条件下，对经过人工接种的滤柱与自然成熟的滤柱进行去除率对比；第二阶段，对成熟滤料进行高温高压灭菌，将灭菌后的滤柱与同期运行的未灭菌滤柱进行去除率试验对比．结果 在运行10dN，两个滤柱的除锰效果出现明显差异，25dN，两个滤柱的除锰效果基本相同．经过灭菌的滤柱重新投入运行，仍然保持原有的除锰能力．结论 滤料的成熟期是一个相对的概念，采用生物接种的手段可以有效地缩短锰砂滤料的成熟期．微生物在除锰过程中起到的是促进作用而非决定性作用，包括物理吸附、化学氧化和催化的非生物因素不容忽视．     

基于能量理论的深埋矿山矿柱尺寸设计方法

随着资源开发步入到深部开采阶段,深埋矿山开采过程中的动力灾害问题日益突出,传统静力稳定分析方法在应对这些问题时表现出一定的局限性,研究适用于深部矿山的矿柱尺寸设计方法意义重大。本文基于面积承载理论和金属矿山矿柱强度估算方法,以一种动态的视角从功能转换角度重点探讨了瞬间回采方式下的矿柱应变能积聚和转化特征,对地下矿体阶段性分层回采这一过程进行简化,提出了一种基于可释放能理论的适应不同分层钻爆开挖方式下的矿柱尺寸参数设计方法,通过依托某工程实例进行了能量法的应用并与传统强度理论方法进行了比较分析,据此建议了5组矿柱尺寸参数方案,进一步利用有限差分软件（FLAC3D）对其优化从而最终确定了合理矿柱尺寸设计值。研究成果表明：矿柱体受动态开挖作用将产生一定程度的动力响应,诱发产生的动应力和动态变形一度可达静力分析时的两倍,同时也会伴随大量能量的积聚;与传统强度计算理论相比,应用能量法可有效地避免快速回采情况下矿柱动力失稳的可能,设计得到的矿柱尺寸参数更偏保守,随着开挖分层数的增多,能量校核法逐渐趋于和强度静力法等价。经数值模拟优化比选,最终建议该工程矿体分三层回采,矿柱合理宽度22m,高度70m,基本上可以满足回采过程中安全稳定和经济效益的需求,与工程实际契合较好。     

Limitations and potential design risks when applying empirically derived coal pillar strength equations to real-life mine stability problems

The method of determining coal pillar strength equations from databases of stable and failed case histories is more than 50 years old and has been applied in different countries by different researchers in a range of mining situations. While common wisdom sensibly limits the use of the resultant pillar strength equations and methods to design scenarios that are consistent with the founding database, there are a number of examples where failures have occurred as a direct result of applying empirical design methods to coal pillar design problems that are inconsistent with the founding database. This paper explores the reasons why empirically derived coal pillar strength equations tend to be problem-specific and should be considered as providing no more than a pillar strength ‘‘index." These include the non-consideration of overburden horizontal stress within the mine stability problem, an inadequate definition of supercritical overburden behavior as it applies to standing coal pillars, and the non-consideration of overburden displacement and coal pillar strain limits. All of which combine to potentially complicate and confuse the back-analysis of coal pillar strength from failed cases. A modified coal pillar design representation and model are presented based on coal pillars acting to reinforce a horizontally stressed overburden, rather than suspend an otherwise unstable self-loaded overburden or section, the latter having been at the core of historical empirical studies into coal pillar strength and stability.     

Fluid–solid coupling analysis of rock pillar stability for concealed karst cave ahead of a roadway based on catastrophic theory

In order to study the mechanism of water inrush from a concealed, confined karst cave, we established a fluid–solid coupling model of water inrush from a concealed karst cave ahead of a roadway and a strength reduction method in a rock pillar for preventing water inrush based on catastrophic theory. Fluid–solid coupling effects and safety margins in a rock pillar were studied. Analysis shows that rock pillar instability, exerted by disturbance stress and seepage stress, is the process of rock pillar catastrophic destabilization induced by nonlinear extension of plastic zones in the rock pillar. Seepage flow emerges in the rock pillar for preventing water inrush, accompanied by mechanical instability of the rock pillar. Taking the accident of a confined karst cave water-inrush of Qiyi Mine as an example, by studying the safety factor of the rock pillar and the relationship between karst cave water pressure and thickness of the rock pillar, it is proposed that rock pillar thickness with a safety factor equal to 1.5 is regarded as the calculated safety thickness of the rock pillar, which should be equal to the sum of the blasthole depth, blasting disturbance depth and the calculated safety thickness of the rock pillar. The cause of the karst water inrush at Qiyi Mine is that the rock pillar was so small that it did not possess a safety margin. Combining fluid–solid coupling theory, catastrophic theory and strength reduction method to study the nonlinear mechanical response of complicated rock engineering, new avenues for quantitative analysis of rock engineering stability evaluation should be forthcoming.     

Performance of inclined pillars with a major discontinuity

Discontinuities are an inherent part of the rock mass and majorly affect the stability of the excavation skin and pillars. The dip of the discontinuities and their properties also have a significant effect on the strength of the pillars. Empirical approaches are commonly used to determine the pillar strength but can overestimate the strength and don't consider the inclination of the pillars and the strength reduction caused by discontinuities. Numerical modeling is a powerful tool and if calibrated can be used to evaluate the strength of the pillars with discontinuities having a range of properties. The effect of a discontinuity on inclined pillars was conducted which has been seldom considered in evaluating the pillar strength.Three-dimensional vertical pillars were simulated, and the pillar strength was calibrated to accepted theoretical results and then the discontinuities were introduced in different pillar inclinations with distinct width to height ratios to gain an insight into the effective pillar strength reduction. Based upon the results, it was found that the discontinuities have a significant effect with the increase in the inclination of the pillars even at a higher width to height ratios.     

轿车乘员舱内供热负荷计算及影响因素分析

为研究冬季轿车乘员舱热负荷随各影响因素的变化规律,针对桑塔纳2000轿车,采用稳态热负荷计算方法,分多工况计算乘员舱热负荷值,并对外界气温、车速及车身结构对热负荷的影响进行了分析.计算结果表明:车身散热量由大到小依次为玻璃、车底、车顶、车门、后隔板及立柱,散热量最大的玻璃约占车身结构的46.7%.对于玻璃结构应设法改变其热导率才能明显降低热负荷,在车身结构中优化隔热层、气隙也能显著提高车体的隔热能力.研究结果可为合理设计乘员舱供暖设备提供依据.     

Subsidence over room and pillar retreat mining in a low coal seam

The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.     

冲压工艺对车身构件强度的影响

采用成形模拟、试验测试和结构分析相结合的方法对车身构件在冲压成形过程中产生的板料厚度减薄、冷作硬化问题进行了研究。得出成形过程中,板料屈服极限的提高对车身构件强度的强化作用要远大于板料厚度减薄对强度的削弱作用。本文研究结果可以为车身结构优化及轻量化设计提供更加精确的参考数据。     

条带开采尺寸设计的弹塑性方法

本文将条带开采的采出条带视为椭圆孔，以弹塑性理论为基础，利用复变函数和保角映射，导出了条带开来时矿柱上的应力分布。由于存在着“尺寸效应”，介绍了由岩块试样的强度来估算岩体强度的计算公式。首次提出了根据屈服带宽度和条带煤柱宽度来确定条带开采安全系数的方法，同时给出了设计条带开采尺寸的步聚。国内外条带开采的经验表明，条带开采的安全系数一般为１．２～１．８。     

热风炉冷风分布的计算机模拟研究(Ⅲ)

应用紊流三维模型模拟内燃式热风炉内冷风在格子砖柱中的分布,寻求改善其分布的途径,讨论了不同布置的水平导流板和竖直导流板的结合使用对气流分布的影响,模拟结果表明,在支柱空腔内加设水平导流板改变了原有大回旋流场,使回旋流变成大面积的单向流,发展了边缘气流;支柱空腔内加设竖直导流板抑制了边缘气流的发展,加强了中心气流。通过水平导流板和竖直导流板的适当结合,可以实现冷风在格子砖内的均匀分布。