Effect of impact angle on wear behavior of Mo2NiB2–Ni cermets with different Ni content

Herein, the influence of the impact angle and Ni content on the wear behavior of Mo₂NiB₂–Ni cermets was studied using an erodent-carrying slurry comprising artificial seawater and SiO₂ sands. The results reveal that the material loss may be attributed to the wear damage caused by SiO₂ sands because cermets are expected to exhibit good corrosion resistance in artificial seawater. The relative density of cermets markedly influences their resistance to wear damage, and the material loss experienced by cermets with poor relative density is 2–4 times higher than that of cermets with good relative density; this occurs because a higher relative density can markedly enhance the mechanical properties and reduce the defects in the cermets. Moreover, the results indicate that as the impact angle increases from 0° to 60°, the manifestation of the wear mechanism changes from damaging the Ni binder phase (caused by single cutting wear) to damaging both the Mo₂NiB₂ ceramic and Ni binder phases due to the combination of cutting wear and impact wear. The wear damage is dominated by the cutting wear and impact wear from SiO₂ sand at the low and high impact angles, respectively. Furthermore, the severe deterioration of the single ceramic skeleton at high impact angles indicates that the synergistic influence of the Mo₂NiB₂ ceramic and Ni binder phases on enhancing the wear resistance of the cermets intensifies at high impact angles.     

缓冲套对停止器挡杆防撞性能影响的测试与分析

对停止器挡杆的碰撞力进行了计算,在此基础上,对缓冲套对停止器挡杆防撞性能的影响进行测试与有限元分析。通过测试与分析确认,带聚氨酯缓冲套的停止器挡杆,碰撞力小,碰撞时间短,强度满足要求,且挡杆中铜套的变形小。在不考虑其它因素的前提下,优先选用带聚氨酯缓冲套的停止器挡杆。     

磷矿山开采系统对黄柏河东支的影响研究

从黄柏河东支流域磷矿山绿色开发要求出发，基于地表水环境系统和矿业开采的耦合影响作用，开展了磷矿山开采对黄柏河东支的水环境的影响研究。通过定量和定性分析，在磷矿山开采过程中对黄柏河东支的各种影响因素中，矿井涌水(占比为43.19%)、尾渣淋溶水(占比为15.51%)、矿废石淋溶水(占比为14.64%)和生产废水(占比为10.84%)为磷矿山开采对黄柏河东支水环境的主要影响因素，尤其是矿井涌水携带的总污染物量大，影响占比接近50%。该研究影响分析为黄柏河东支水环境的治理提供有力指引支撑。     

垂直冲击试验机的研制

为满足简便检测塑料产品抗冲击强度的需求,研制了垂直冲击试验机。对垂直冲击试验机的结构进行了设计,基于力学原理进行了受力计算,并对工作原理与相对基准设定问题进行了分析。介绍了垂直冲击试验机的操作方法,并进行了规格校验。     

Topology optimization for crashworthiness of thin-walled structures under axial crash considering nonlinear plastic buckling and locations of plastic hinges

Although topology optimization is established for linear static problems, more effort is required for solving nonlinear plastic problems. A new topology optimization approach with equivalent static loads (ESLs) is suggested to find the optimum topologies and locations of plastic hinges of thin-walled crash boxes by considering crash-induced deformation, the main crash energy-absorbing mechanism. Together with finite element method crashworthiness analyses, considering all nonlinearities with rate-dependent plasticity, the method was developed using an appropriate time-incremental scheme of ESLs without removing any high values of loads. Analyses show that the crash boxes with optimum topologies have energy-absorbing capabilities equivalent to the original structure. The proposed method is evaluated for two crashes: a crash box at low speed and a double cell subjected to high-speed collision. The results indicate that this method captures nonlinear crushing behaviours and accurate locations of plastic hinges where, if proper reinforcements are made, energy absorption can be enhanced.     

冲击载荷下TC18钛合金力学性能模拟研究

TC18钛合金在退火状态下的屈服强度非常高,进行动态力学性能测试存在一定困难,可优先考虑采用数值模拟方法对其动态力学性能进行研究,而数值模拟结果的精确性主要取决于合金本构方程的精确性。为了减少数值模拟与实验结果之间的差异,在Johnson-Cook模型的基础上做了调整,利用ABAQUS软件的子程序接口自定义了材料本构子程序UMAT,以代码的形式来扩展ABAQUS程序的功能。通过与ABAQUS/Standard软件分析结果以及实验结果的对比,验证了自定义材料本构子程序UMAT计算结果的精确性与可靠性。该研究可为TC18钛合金的结构设计提供参考。     

Ti对铬钼钒模具钢奥氏体化组织与性能的影响

??The microstructure and properties of die steels with Ti and without Ti at different austenitizing temperatures were studied through the combination of thermodynamic calculation and experiment. The results show that the total solution temperature of Cr23C6, Cr7C3, VC, V2C, V8C7, MoC, Mo2C and TiC is 748. 2, 952. 7, 977. 3, 632. 9, 1116. 0, 1131. 2, 645. 3 and 1044. 1??, respectively. Hardness and impact toughness both increase with the increase in temperature. When the austenitizing temperature is above 1200 ??, it has a greater influence on the hardness. Toughness of die steel with Ti is better than that without Ti. The grain becomes coarse and the amount of martensite increases with the increase of temperature. The average grain size of the die steel with Ti is 21. 4??m smaller than that without Ti, and the size of the undissolved phase of the former is about 0. 2??m smaller than that of the latter.     

The Territorial Impact Assessment of transport: the case of the Egnatia motorway system in the cohesion potential of Southeast Europe

Territorial Impact Assessment (TIA) is proposed as a critical tool in order to investigate the way policies affect spatial development and hence territorial cohesion. The paper introduces a TIA methodological model in relation to transport sector. The design of the methodological model is based on a quantitative evaluation framework that comprises a set of selected indicators applied in a cross-border area of southeast Europe, influenced by the operation of the Greek motorway system of Egnatia and its vertical axes. The indicators are grouped into three main fields of TIA, i.e. transport intermodality, polycentric spatial organization and cross-border territorial cooperation. The TIA’s indicators are approximated by quantitative analysis. The procedure concludes to an overall composite indicator measuring the ‘level of territorial cohesion’ along with some core results and the expected added value. It also highlights some key technical aspects about the routines used and proceeds to suggestions for further refinement.     

Environmental effects on the strength and impact damage resistance of alumina based oxide/oxide ceramic matrix composites

In this study the effects of high temperature and moisture on the impact damage resistance and mechanical strength of Nextel 610/alumina silicate ceramic matrix composites were experimentally evaluated. Composite laminates were exposed to either a 1050°C isothermal furnace-based environment for 30 consecutive days at 6 h a day, or 95% relative humidity environment for 13 consecutive days at 67°C. Low velocity impact, tensile and short beam strength tests were performed on both ambient and environmentally conditioned laminates and damage was characterized using a combination of non-destructive and destructive techniques. High temperature and humidity environmental exposure adversely affected the impact resistance of the composite laminates. For all the environments, planar internal damage area was greater than the back side dent area, which in turn was greater than the impactor side dent area. Evidence of environmental embrittlement through a stiffer tensile response was noted for the high temperature exposed laminates while the short beam strength tests showed greater propensity for interlaminar shear failure in the moisture exposed laminates. Destructive evaluations exposed larger, more pronounced delaminations in the environmentally conditioned laminates in comparison to the ambient ones. External damage metrics of the impactor side dent depth and area directly influenced the post-impact tensile strength of the laminates while no such trend between internal damage area and residual strength could be ascertained.