壳体和内芯的材料特性对PELE侵彻后效的影响

为确定PELE的壳体材料和内芯材料对侵彻后效的影响因素,在30 mm弹道炮上发射不同材料的钢壳体和惰性内芯材料组成的PELE对固定靶板进行撞击实验.实验结果表明:实验速度范围内,提高着速能够增大破片的数量和飞散角,破片飞散角比破片数量对着速更"敏感";钢壳体的屈服强度越大或剪切模量越小,PELE的侵彻后效越好;内芯材料的剪切模量是侵彻后效的主要影响因素之一,而不是密度;实验中的最佳匹配关系是壳体为D60、内芯为PE.这些结论为小口径PELE的设计和应用提供了重要依据.     

Ballistic limit and residual velocity of PELE penetrating against metal target

Based on analyzing the conservation of energy of penetrator with enhanced lateral efficiency (PELE) the penetrating against metal target, a theoretical expression predicting the residual velocity of PELE perforating the target is obtained. By modifying De Marre semi-experience formula,the ballistic limit velocities of PELE penetrating into 2024 aluminum alloy and 45# steel targets are also given. The theoretical predictions fit well with experimental or simulative results.     

Influence of structure parameters on terminal effect of small caliber PELE impacting metal target

By changing the length-diameter ratios and inner-to-outer diameter ratios, some numerical simulations were made on PELE normal penetrating metal target using AUTODYN-3D code. The influence rules of length-diameter ratio and inner-to-outer diameter ratio to the terminal effect of PELE are obtained. When the length-diameter ratio is in the range of 4-7, inner-to-outer diameter ratio is in the range of 0.54-0.72, the PELE can perform satisfactory double terminal effects embodied in armor-piercing and fragment killing. Based on simulation results, a test projectile is designed and an impact experiment of PELE is carried out, which demonstrate the efficiency of the simulation method.     

Strength optimization of ultralight corrugated-channel-core sandwich panels

Novel ultralight sandwich panels, which are comprised of corrugated channel cores and are faced with two identical solid sheets, subjected to generalized bending are optimally designed for minimum mass. A combined analytical and numerical (finite element) investigation is carried out. Relevant failure mechanisms such as face yielding, face buckling, core yielding and core buckling are identified, the load for each failure mode derived, and the corresponding failure mechanism maps constructed. The analytically predicted failure loads and failure modes are validated against direct finite element simulations, with good agreement achieved. The optimized corrugated channel core is compared with competing topologies for sandwich construction including corrugations, honeycombs and lattice trusses, and the superiority of the proposed structure is demonstrated. Corrugated- channel-core sandwich panels hold great potential for multifunctional applications, i.e., simultaneous load bearing and active cooling.

     

水稳碎石基层取芯临界强度与整体性质量评价时机

为了确定水稳碎石基层合理的整体性质量评价时机,消除养生条件、级配类型和设计强度(水泥剂量)的影响,弥补采用固定龄期法则评价施工质量的局限性,采用振动成型方法成型3种类型级配、3种水泥剂量的大型试件,并采用3种养生路径养生后进行钻芯和劈裂强度试验,建立成熟度与劈裂强度的关系.结果表明:水泥剂量(质量分数)对取出完整芯样的...     

Verification of Numerical Modeling in 2-D Wave Propagation in Rock

Compressional harmonic wave propagation from a cylindrical tunnel or borehole in an intact rock is the basis for investigation of the practical explosion waves in a fractured rock mass. The amplitudes of the radial stress wave obtained from the universal distinct element code （UDEC） were compared with the analytical solutions for two cases with different conditions. Good agreements between the UDEC results and the analytical solutions have been achieved. It indicates that UDEC can model 2-D dynamic problems at a high degree of accuracy.     

Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel

To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force, cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve (GRC) considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.

     

横观各向同性岩体位移解析解与数值解对比研究

在横观各向同性岩体中巷道的位移解析解的基础上,运用数值计算软件FLAC3D,得到了不同倾角下的数值解,并将初始状态下的位移解析懈同不同倾角下的数值解进行对比研究,通过误差分析得出了解析解的工程适用范围．     

室内成型试件与路面芯样的抗车辙差异性评价

为了评价室内成型试件与路面芯样抗车辙能力的差异,利用多轮车辙仪(RLWT)获取车辙变形量,从宏观角度研究室内成型试件与路面芯样的抗车辙能力;采用工业CT获取沥青混合料断面扫描图像,从细观角度探讨室内成型试件与路面芯样的粗集料颗粒与面空隙率沿深度方向的分布状况．结果表明:由于压实方式不同,两种试件的空隙率相差甚大,从而导致其抗车辙能力也有明显差异;路面芯样的粗集料颗粒与面空隙率在深度方向分布的均匀性较差;路面芯样的平均面空隙率及上端的面空隙率明显大于室内成型试件,从细观角度证明了宏观研究成果的准确性．     

含断续节理脆性岩体灌浆效果研究

本文针对含断续节理天然岩体灌浆前后不同节理接触度,运用断裂力学理论建立相应的岩体抗剪强度分析模型。并用有限单元法研究了节理面不同接触度条件下岩体沿节理面方向综合抗剪强度参数的变化,从而定量地给出了灌浆效果与岩体强度的相互关系。     

Solidification structures of high niobium containing TiAl alloys

To understand the effect of alloy stoichiometry on the microstructural development and mechanical behavior of γ-TiAlbased materials, it is necessary to have a determination of the phase relationships for the TiAl alloy system near the γ phase field.Cast structures and phases of Ti-(43-47)Al-8Nb-(1-2)Mn (at%) alloys have been studied by using scanning electron microscope and X-ray diffraction. Their solidification path and microstructure development during the solidification were analyzed. The experimental results show that the alloys with different Al contents form different macrostructures and microstructural morphologies. This indicates that the solidification paths are different with different Al contents. The alloy with 43Al forms equiaxed grain structure, and the solidification path is as follows: L → L β→β→α β→α β cores →α2 γ B2 cores. Whereas the alloy with 47Al forms columnar grain structure, and the solidification path is as follows: L → L β→α β L →α γ β cores →α2 γ B2 cores. The β phase is their primary solid phase and can be retained to ambient temperature. The alloy with 43Al solidifies completely into β phase. The peritectic reactions L β→α and L α→γ appear when the Al content increases to 47Al.     

Dynamic response of ultralight all-metallic sandwich panel with 3D tube cellular core to shallow-buried explosives

The underbody of a vehicle system, either military or civil, is typically made of a relatively thin metallic plate, thus vulnerable to mine blast attacks. To improve the blast resistance, a multitude of protective structures have been proposed as attachments to the thin plate. In the present study, a novel ultralight all-metallic sandwich panel with three-dimensional(3D) tube cellular cores mounted to the vehicle underbody was envisioned as such a protective system. A metallic substrate(mimicking vehicle bottom)was placed above the proposed sandwich panel to construct a sandwich-substrate combinative structure. A series of sandwich panels having 3D tube cellular cores were fabricated via argon protected welding and laser welding. Mechanical responses of the combinative structure subjected to the denotation of 6 kg TNT explosives shallow-buried in dry sand were experimentally measured. Full numerical simulations with the method of finite elements(FE) were subsequently carried out to explore the physical mechanisms underlying the observed dynamic performance and quantify the effects of key geometrical parameters and connection conditions of the protective system. The performance of the proposed sandwich panel under shallow-buried explosives was also compared with competing sandwich constructions having equal mass. Finally, a preliminary optimal design of the 3D tube cellular core was carried out.     

负载自适应的异构MPSoC任务调度算法研究

在异构MPSoC中,并行任务通过调度算法被分配到各个处理器核上运行,因而任务调度算法的优劣将直接影响异构MPSoC的应用性能。根据处理器核类型和任务间依赖关系,以减小任务间通信开销为目标,提出一种具备负载自适应能力的异构MPSoC任务调度算法。首先,将待调度任务集划分为多个并行任务子集;其次,在考虑处理器核负载的基础上,根据并行任务子集集合、处理器核集合及任务子集在各个核上的执行效率生成赋权二部图;最后,利用赋权二部图最大权匹配方法,将并行任务子集合理地调度到负载适应的处理器核上运行,以降低任务集的平均调度长度,并提高处理器核利用率,从而实现异构MPSoC应用性能的提升。仿真实验在不同的任务总数、任务最大前驱数、核类型、核数量的应用场景下,通过任务集平均调度长度、处理器核利用率两项指标对提出算法进行了定量分析。结果表明,提出算法能有效降低任务集平均调度长度,在实现负载自适应的同时提高异构MPSoC处理器核的利用率。     

锥头弹体贯穿铝合金靶板的过载分析

研究了刚性圆锥头弹体贯穿延性金属靶板的冲击力学特性,将侵彻过程分为3个阶段,利用圆柱形空腔膨胀理论建立了侵彻方程,得到了各阶段弹体的过载和能耗的表达式.对4种不同厚度的铝合金靶板的锥形钢弹贯穿试验算例进行了理论和仿真计算,对所得结果与试验数据作了对比,结果显示三者一致性较好.分析了弹体在不同阶段的过载特性和影响因素,为尖形弹体及小型装药的侵彻过载特性评估提供了理论参考和分析方法.     

二元冰蓄冷系统中的纳米添加剂成核特性研究

为了获得蓄冰溶液中纳米成核添加剂的选择标准,选择在纯净水和乙二醇溶液两种不同的基体溶液中添加两类不同的纳米微粒（SiO₂和α-Al₂O₃）进行实验,观察得到了不同的成核效果.以相关润湿机理为基础,对实验结果进行初步分析后表明:不同质量分数的添加剂具有不同的成核效果;当纳米微粒添加到乙二醇溶液中时,由于两者润湿效果较差,从而导致微粒成核效果下降,混合溶液过冷解除温度下降,增加制冰能耗,因此添加剂颗粒与基体溶液的润湿性将严重影响其结冰成核效果,润湿性能越好,成核效果越好．     

选择性烧结覆膜砂铸型(芯)的试验研究

采用特殊配制的覆膜砂作为选择性烧结材料,试验研究了各烧结参数（扫描速度、激光功率、烧结层厚等）对烧结试样强度的影响,分析了激光束作用下覆膜砂硬化的特征,烧结了铸造用型（芯）,用该铸型（芯）浇注了金属铸件。     

Analytical models for evaluating buoyancy-driven ventilation due to stack effect in a shaft considering heat transfer from shaft interior boundaries

Stack effect is a dominant driving force for building natural ventilation. Analytical models were developed for the evaluation of stack effect in a shaft, accounting for the heat transfer from shaft interior boundaries. Both the conditions with constant heat flux from boundaries to the airflow and the ones with constant boundary temperature were considered. The prediction capabilities of these analytical models were evaluated by using large eddy simulation (LES) for a hypothetical shaft. The results show that there are fairly good agreements between the predictions of the analytical models and the LES predictions in mass flow rate, vertical temperatures profile and pressure difference as well. Both the results of analytical models and LES show that the neutral plane could locate higher than one half of the shaft height when the upper opening area is identical with the lower opening area. Further, it is also shown that the analytical models perform better than KLOTE’s model does in the mass flow rate prediction.     

氮气在水饱和岩心中的渗流规律

用带有刻度的气液分离装置研究了氮气在不同含水饱和度岩心中的流动特性及突破规律。实验结果表明,当气体注入压力一定时,液体流出量缓慢增加,气体突破之前伴随液量的突然增大;在所研究的时间范围内,各阶段气体平均流速呈幂指数增加。随着注入压力的增加,气体在岩心中的突破时间变短,排出液量增大,表明气体在岩心中的流动速度增加,波及体积增加,且各阶段的流速仍呈幂指数变化,这说明气体的流动特性随其侵入量的变化而变化。随着压力的增加,岩心气体视渗透率先快速增加,然后趋于平缓,这是压缩引起的气体滑脱效应减弱所致;而完全饱和水的岩心随着残余水饱和度的降低,气体视渗透率先缓慢增加,当含水饱和度降到一临界值时,视渗透率迅速增大,这是空间增大引起气体的滑脱效应增加所致。     

共享资源约束下多核实时任务分配算法

为了提高多核实时系统任务分配效率,研究分组固定优先级调度策略下的任务分配算法.通过分析核间任务阻塞对任务最坏情况响应时间产生的影响,提出由于任务间共享资源冲突而引发了任务分配故障问题;指出负载非均衡算法,如First-fit算法、Best-fit算法容易引发任务分配故障.为了避免该问题,提出基于分组与负载均衡的任务分配算法.该算法将存在访问共享资源冲突的任务分配到同一核上,以避免核间任务阻塞;当这些任务无法分配到同一核上时,将这些任务依次分配到当前负载最轻的核上以避免任务分配故障.可调度性分析实验表明,采用该算法可以避免任务分配故障,减少分配任务所需的处理器核数(比Worst-fit算法少10%～40%).     

Analysis of asphalt pavement structural response from an accelerated loading test

This study was to compare theoretical calculation and practical measurement structure response of asphalt pavement. Analysis of the pavement layer moduli was determined from a Back-calculation of Falling Weight Deflectometer (FWD) data and the measured stiffness moduli of asphalt layer cores. The pavement response was calculated using a theoretical model and the measured strain response at the bottom different layers. Layered elastic theory was used to back-calculate the layer moduli and three different theory models were used to forward calculate the strain and deflection. The models were: Layered Elastic Theory (LET), the Method of Equivalent Thicknesses (MET) with linear elastic and the Finite Element Method (FEM) where asphalt layer may be viscoelastic. The results showed that the calculation structure response from FEM was consistent with measured results.