运用虚拟仪器技术的汽车真空助力器性能检测系统设计

真空助力器是汽车制动系统的一个重要总成部件,其性能好坏直接影响行车安全,故在出厂前或维修时,必须检测其性能是否达到设计指标和相关标准的要求,以消除对行车安全的隐患。以GB12676-1999汽车制动系统结构、性能和试验方法国家标准,QC/T 307-1999真空助力器技术条件国家标准,QC/T 308-1999真空助力器试验方法国家标准等为设计依据,通过计算机技术、机电一体化技术和液压控制技术等的有效集成,利用虚拟仪器LabVIEW的编程、分析功能,实现模拟真实制动环境和制动行为时真空助力器基本性能参数的测定。试验结果表明,系统运行可靠,数据准确,灵敏度高,特别是能够获得汽车连续制动或频繁制动时的输出参数,并能真实反映助力器在使用过程中的技术参数和工作特性。     

Formation of tangential pre-stress as a residual stress and its influence on the tribological performance of nodular cast irons

Since any state of residual stress influences the service behavior of a material, it is of particular interest for engineers and designers to know its benefits to machine parts, and where it can be utilized successfully. From this point of view, mechanical tangential pre-stress as circumferential compressive residual stress has been investigated for wear performance. For this purpose, a thick walled cylinder specimen model was established as a tribo-element, and the force, which will form the desired tangential pre-stress representing residual stress, has been calculated by the rules of elasticity theory. In order to compare the effect of residual stress on the wear performance under dry and lubricated conditions, 0.8 R_e (R_e: unidirectional yield strength) were applied to the nodular cast iron (DDK-40, DDK-60) specimens. Wear test results have been evaluated in terms of two different stress levels, 0 R_e and 0.8 R_e, formed on the specimen.