该东风EQ2102型汽车封存后为何难启动

故障现象：一辆东风EQ2102型汽车,停驶6个月后,发动机在启封时难以启动,排除高压油路中的空气时,空气一直排除不干净。故障检查：检查低压油路,拧松放气螺钉后用手油泵泵油,排气孔出油良好,且无气泡排出,说明低压油路正常。检查高压油路,     

Multi-Objective Optimization of Rail Pre-Grinding Profile in Straight Line for High Speed Railway

In order to modify the rail pre-grinding profile smoothly, non-uniform rational B-spline (NURBS) curve with weight factors is used to establish a parameterized model of the profile. A wheel-rail contact stochastic finite element model (FEM) is constructed by the Latin hypercube sampling method and 3D elasto-plastic FEM, in which the wheelset’s lateral displacement quantity is regarded as a random variable. The maximum values of nodal accumulated contact stress (NACS) and nodal mean contact stress (NMCS) in different pre-grinding profiles with differential weight factors are calculated and taken as the training samples to establish two Kriging models. A multi-objective optimization model of pre-grinding profile is established, in which the objective functions are the NACS and NMCS Kriging models. The optimum weight factors are sought using a non-dominated sorting genetic algorithm II (NSGA-II), and the corresponding optimum pre-grinding profile is obtained. The contact stress calculation before and after optimization indicates that the maximum values of NACS and NMCS decline significantly.     

Initial pre-stress finding and structural behaviors analysis of cable net based on linear adjustment theory

The tensile cable-strut structure is a self-equilibrate pre-stressed system. The initial pre-stress calculation is the fundamental structural analysis. A new numerical procedure was developed. The force density method is the cornerstone of analytical formula, and then introduced into linear adjustment theory;the least square least norm solution, the optimized initial pre-stress, is yielded. The initial pre-stress and structural performances of a particular single-layer saddle-shaped cable-net structure were analyzed with the developed method, which is proved to be efficient and correct. The modal analyses were performed with respect to various pre-stress levels. Finally, the structural performances were investigated comprehensively.     

沥青路面抗滑性能影响因素识别研究进展

沥青路面作为公路建设的重要内容,其抗滑性能是道路安全问题的核心,探究其影响因素可以为提高路面抗滑性能提供依据。国内外学者对此做了大量研究,也取得了相应的进展。本文对国内外的研究成果进行了系统的归纳总结,将公路沥青路面抗滑性能影响因素分为了沥青混合料的材料特性、环境因素、车辆特性3个主要方面,其中在沥青混合料的材料特性方面,研究认为集料的结构特性与混合料配合比对抗滑性的影响较大;环境因素方面,研究认为温度对于抗滑性的影响较大;车辆特性对抗滑性的影响方面,研究认为主要体现在轮胎特性与荷载方面。此外随着行车速度的增加,路面的抗滑性能呈现降低趋势。     

海上风电机组预应力钢管混凝土格构式塔架动力特性分析

为避免风电结构发生共振,影响发电效率和结构安全,了解掌握风电机组支撑结构动力特性至关重要。预应力钢管混凝土格构式塔架是一种新型的风电机组支撑结构,在海上风电机组大型化过程中将扮演重要角色,本文采用有限元建模的方式对该塔架固有频率进行分析,分析在不同底部跟开、不同角柱直径和壁厚、不同斜杆壁厚下的固有频率的变化特征,并提出设计建议,以期对设计人员提供思路。     

盾构配件的使用与管理

针对海瑞克S-282盾构配件的使用与管理在以往施工中所暴露出的问题,根据制定的配件计划,提出了某些盾构配件(例如传感器、电磁阀、盾尾刷)在使用和维护上的一些方法。目的是为了实现盾构安全、经济的运行。     

这辆延安SX2150K型汽车离合器踏板为何不易回位

故障现象：一辆延安SX2150K型汽车,封存了3个月,重新启封时,发现踩下离合器踏板后抬起时,踏板回位缓慢,甚至不能完全回位。