A new fractal model of elastic,elastoplastic and plastic normal contact stiffness for slow sliding interface considering dynamic friction and strain hardening

The deflection properties of elastic stage, elastoplastic stage and plastic stage of elastomer were analyzed. Taking account of the kinetic friction force in friction interface and strain hardening in slow sliding interface, the elastic, elastoplastic and plastic normal contact stiffness model for harsh surface was established, which revised the Majumdar-Bhushan fractal model and made it more perfect. In the combination of macro and micro perspective, the effects of coarse surface fractal variables, kinetic friction force in the friction interface, material characters of the friction couples on the contact status and contact property were discussed by the study of digital analysis. Results imply that the normal contact stiffness improves with the increasing real contact area and normal contact load, and reduces with the augment of kinetic friction coefficient. When the kinetic friction coefficient is smaller than 0.3, the normal contact stiffness comprises a linear decrease with the increment of kinetic friction coefficient. When the kinetic friction coefficient is bigger than 0.3, the normal contact stiffness has an exponential decrease with the increasing kinetic friction coefficient.     

Multi-scale simulation for the forming of a heavy vessel head considering the evolution of defects and microstructure

The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production, due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.     

考虑地域差异的柴油汽车排放清单建立方法研究

柴油汽车排放是目前城市大气污染的重要组成部分,如何结合区域差异建立柴油汽车排放清单是制定相关减排政策的基础工作.首先按照使用用途将柴油汽车划分为7种车型,选择国Ⅲ 、国Ⅳ、国Ⅴ共3种排放标准的车辆得到基础排放因子;具体分析不同区域的柴油汽车排放相关影响因素及修正权值,包含环境参数、车速分布、载重系数及劣化系数;结合修正参数建立柴油汽车综合排放因子计算公式及城市柴油汽车排放清单计算模型,以淄博市为例完成了城市柴油汽车排放清单的建立.研究结论表明,本文提出的柴油汽车排放清单建立方法,适用于结合不同城市的环境特征、车辆特征和道路特征定量评价柴油汽车污染排放状况,并为制定具体的柴油汽车污染物排放控制政策奠定基础.     

跨座式单轨交通预应力轨道梁的静载试验

针对重庆轻轨较新线二期工程和3号线,特进行新型跨度为25 m的直线预应力(PC)轨道梁1∶1模型静力抗弯试验研究.介绍试验梁的试验情况,如荷载布置、加载及测试设备、测试内容、测点布置、加载制度;得出静载试验结果,包括挠度试验结果、应力试验结果和结构校验系数;最后给出25 m直线PC轨道梁的静载试验结论.试验结果表明,该新型PC轨道梁可以应用到实际工程中去.     

基于船舶大数据的港口装卸效率值计算方法

集装箱港口的装卸效率是衡量港口竞争力和吸引船公司前来挂靠的关键指标之一.为准确估计港口的装卸效率值,基于船舶自动识别系统(AIS)数据,利用Greatmaps(GMap)可视化技术,提出一种计算港口装卸效率值的方法.利用该方法估算上海港、新加坡港、深圳港和宁波-舟山港的月度装卸效率值,4个港口2017年上半年的装卸效率...     

车辆行驶跑偏试验方法研究与分析

车辆保持直线行驶的能力是汽车行驶稳定性的一个重要评价项目,为测量车辆行驶跑偏量,国家颁布了相应法规,规定了相应的试验方法.文章详细介绍了车辆行驶跑偏试验方法,针对标准要求搭建检测系统并进行相关试验.由于标准要求定位精度过高,因此提出了一种简化的试验设备测试方法,通过试验结果比较,发现简化方法精度满足厘米级检测要求,适用...     

加强技术创新产品开发实现跨越式发展

２０００年７月３日，长春汽车研究所建成５０周年，５０年来，研究所始终坚持技术进步，不断创新，使产品开发实现了跨越式发展，为一汽产品一直保持高的市场竞争力奠定了坚实的技术基础，介绍了一汽产品的更新换代情况、ＣＡＤ／ＣＡＥ／ＣＡＭ一体化进程及产品试验手段、试制技术的扩展与提高情况。     

浏阳河浅埋大跨度隧道临时支护安全性分析

针对目前国内采用CRD法修建隧道施工过程中对临时中隔壁的安全性研究很少,结合武广客运专线浏阳河浅埋大跨度隧道对中隔壁采用现场监测和数值模拟两种手段进行了对比分析,两种方法所得结果吻合良好。结果表明,在CRD1,CRD3部超前的情况下,中隔壁上部的水平位移明显大于下部,但结构安全系数能够满足施工要求。     

车用柴油机微粒捕集器流场的数值模拟与分析

研究的柴油机微粒捕集器采用目前应用最为广泛的壁流式蜂窝陶瓷作为过滤体,根据其结构对称性和内部流动数学模型,建立了稳态层流的过滤体内部流动CFD仿真模型,并运用离散格式分离求解器进行求解。仿真计算与试验验证表明模型能准确反映过滤体内部流动特性。     

公路路面养护质量检测技术

在我国《公路技术状况评定标准》中,路面状况指数（PCI）、行驶质量指数（RQI）、路面结构强度指数（PSSI）、抗滑性能指数（SRI）、路面车辙（RDI）是公路养护质量指数（PQI）检查评比的重要指标。四项指标经汇总计算,由公式PQI=WPCIP们＋WRQIRQI＋WRDIRDI＋WSRISRI,而得出路面的养护质量指数PQ1。伴随着我国高速公路养护的现代化进程,对五项指标的检测也经历了从人工到自动化的巨大变革。