顶管爆破中地表质点振动的数值模拟研究

为有效地预测地下顶管爆破所产生的爆破振动对地表结构的影响,基于ANSYS/LS-DYNA软件,采用分步数值模拟技术并结合实际装药对顶管爆破进行了数值模拟。在控制爆破振动速度为1.0cm/s的情况下,爆破振动危害影响范围为15m,并与现场实测结果进行了对比分析。数值模拟结果与现场所测数据较为吻合,可为同类顶管爆破方案设计中振动效应的控制和计算提供一种新的途径。     

一种伺服机构模拟负载台多弹簧钢板统一设计方法

弹簧钢板是航天伺服机构负载台的重要组成部分,决定了负载台的负载特性。提出了一种伺服机构模拟负载台多弹簧钢板统一设计方法。相较传统方法,该方法可用于多钢板设计并拓展了其设计域。首先,以弹性力学矩形截面杆扭转的解析解为基础,定义了钢板扭转模型并提出修正系数的指数衰减函数形式的近似表达式;其次,提出多弹簧钢板设计的优化模型并给出确定优化初值的方法,该优化模型使目标函数和约束函数在全设计域二阶连续可微;最后,提出简化的钢板负载特性有限元校核方法,该方法可对不同宽厚比钢板扭转进行有限元建模和分析。分析结果表明:用工程案例对伺服机构模拟负载台多弹簧钢板统一设计方法进行检验,有效性得以验证。     

伺服机构负载台弹簧钢板设计优化

弹簧钢板是航天伺服机构负载台的重要组成部分,决定了航天伺服机构负载台的负载特性.提出弹簧钢板设计的优化方法,以材料力学公式为基础,应用集成优化平台ModelCenter,建立弹簧钢板设计优化模型;应用有限元方法对钢板负载特性进行建模和校核;用工程案例检验弹簧钢板设计优化方法的有效性,并讨论优化方法应用中应注意的问题.     

Reliable estimation of performance of explosives without considering their heat contents

In this paper, a new approach is introduced to calculate detonation pressure of large class of explosives based elemental composition and specific structural groups rather than using their heats of formation. It is shown here how the loading density, atomic composition and some structural parameters can be integrated into an empirical formula for predicting the detonation pressure of pure and explosive formulations over a wide range of loading densities. The results show good agreement with experimental values so that the deviations are within about experimental errors. The calculated values of new method are also compared with the computed results obtained by complex computer code using BKWR and BKWS equations of state. Predicted detonation pressures have root-mean-square (rms) deviation for new method, BKWR and BKWS equations of state are 6.5, 11.7 and 7.4kbar, respectively.     

胶结充填体与矿柱相互作用双轴加载试验研究

矿柱与充填体之间的相互作用是矿柱和充填体优化和安全设计的重要问题。通过双轴加载试验研究了侧向应力和采场充填率等因素对矿柱与充填体相互作用的影响。结果表明：充填体接顶时，充填体能充分发挥自身强度并直接参与顶板支撑，此时矿柱-充填体支承系统可以充分发挥承载力；充填体不接顶时，在一定侧向应力作用下矿柱-充填体支撑力提高主要是两者界面摩擦力的提高，而充填体横向约束效应对于矿柱强度提高效应不明显；较高的充填率意味着在矿柱-充填体界面处产生更大接触面积，在一定侧向应力作用下会在界面产生更大的摩擦力，进而产生更大的系统承载能力。试验结果与新城金矿测试结果的对比证实了该项研究对于新城金矿二步采场的稳定性分析具有一定的指导意义。     

计算机优化物流环节在船舶配载上的应用

针对目前国内船舶配载的现状 ,根据船舶配载的特殊性 ,以及对平衡性、强度、装载量和装载顺序等方面的要求 ,设计了船舶配载模型 ,经实践证明 ,优化了物流环节 ,加快了物流速度 ,提高了码头利用率     

Reduction of global effects on vehicles after IED detonations

Global effects caused by the detonation of an IED near a military vehicle induce subsequent severe acceleration effects on the vehicle occupants. Two concepts to minimize these global effects were developed, with the help of a combined method based on a scaled experimental technology and numerical simulations. The first concept consists in the optimization of the vehicle shape to reduce the momentum transfer and thus the occupant loading. Three scaled V-shaped vehicles with different ground clearances were built and compared to a reference vehicle equipped with a flat floor. The second concept, called dynamic impulse compensation （DIC）, is based on a momentum compensation technique. The principal possibility of this concept was demonstrated on a scaled vehicle. In addition, the numerical simulations have been performed with generic full size vehicles including dummy models, proving the capability of the DIC technoloey to reduce the occuoant loading.     

Plane strain evaluation of stress paths for supported excavations under lateral loading and unloading

Excavations are generally analyzed as plane strain problems. The shear strength parameters determined from the triaxial conditions are not representative of the real field conditions. Therefore, plane strain tests on reconstructed silty clay were performed using a modified apparatus to measure the stress-strain curves directly. Three stress paths were tested, where the lower shear strength and the failure strain were measured for tests with unloading in the minor principal stress direction and compared to tests with loading. A set of hyperbolic constitutive models was developed to fit the experimental data at different stress paths. The stress-strain-strength characteristics and the deformation parameters were determined for these tests. A displacement-dependent earth pressure model was then proposed for retaining walls due to excavations, and then it was calibrated against the measured soil response. In the end, a case history of bored pile walls subjected to excavations was illustrated. Calculations using the proposed approach and the standard Mohr-Coulomb model were compared. The analysis using the standard Mohr-Coulomb model was found to underestimate the maximum wall deflection by 15%.     

新柴495B增压柴油机活塞热强度分析

对柴油机增压强化后活塞的热负荷、热强度进行了有限元计算预测，为活塞的结构改进提供了依据。     

EPS材料的力学性能试验研究

通过室内试验,在有无侧限、不同加载速率、不同控制方式和不同围压的条件下,研究了具有密闭空腔结构的成型聚苯乙烯泡沫塑料(EPS)的力学性能.结果表明:EPS材料的应力-应变曲线可分为线弹性、塑性和硬化三个阶段;应变相同时,有侧限时应力值比无侧限时略有提高,并且随着材料密度的增大,应力值不断增大,硬化点也不断提前;相同应变下的应力值会随着加载速率的增加而不断增加;另外,在同一压应力条件下,应变控制式所获曲线的应变较应力控制式时大;在同一应变条件下,材料的应力随着围压的增大而不断减小,当材料进人硬化阶段后,材料的应力却随着围压的增大而不断增大.