铁道车辆疲劳可靠性设计Goodman-Smith图的绘制与应用

Drawing and Application of Goodman-Smith Diagram for the Design of Railway Vehicle Fatigue Reliability

研究铁道车辆疲劳可靠性设计Goodman-Smith图的绘制及其应用方法。提出基于中短与长寿命概率疲劳S—N曲线,确定任意可靠性水平的疲劳强度,以及计算疲劳可靠性设计Goodman-Smith图中转折点坐标的全概率方法。研究表明:以车轮旋转一周、疲劳主应力交变一次为基本循环特征,疲劳寿命用行驶里程表示,以万km为基本单位来绘制铁道车辆的疲劳可靠性设计Goodman-Smith图较为合理。当结构的设计寿命和循环特征与Goodman-Smith图存在差异时,引入换算系数进行修正;当结构部件的疲劳载荷模式与绘制Goodman-Smith图试样的试验载荷模式存在差异时,引入折算系数进行修正;当结构部件的结构形状与尺寸、表面质量、环境条件等可能与绘制Goodman-Smith图的试样存在差异时,引入相应修正系数进行修正;分别给出了上述3种修正系数的表达式。并以LZ50钢疲劳可靠性设计Goodman-Smith图的绘制、修正及其在铁道车辆车轴设计中的应用为例,验证了方法的可行性。

Methods of drawing and applying the Goodman-Smith diagram are investigated for the railway vehicle fatigue reliability design. The fatigue strength at arbitrary given reliability level is evaluated by the probabilistic fatigue S-N curves covering the mid-and-short and long life regimes. The transition point coordinates of the diagram are determined on an entire probabilistic sense. The diagram is drawn by a structural fatigue life concept of driving mileage in terms of ten kilometers with a characteristic of vehicle wheel circling number equal to fatigue stress cycling number. In addition, for the production application of the diagram three modification factors are suggested and formulated to consider the differences of the numbers between fatigue stress cycling and the wheel circling, the differences of loading modes between the specimens and the production structures, and the differences of geometries, surface quality, and environments between the vehicle structures and the diagram established specimen. Feasibility of the present methods is indicated by the drawing of LZSO carbon steel basic design diagram and the modification of the diagram for railway vehicle axle design.