地铁扣件螺旋道钉断裂过程分析及改进措施

引入扩展有限元方法,结合现场调研与实测数据,建立均匀受力理想状态和偏载受力不利工况下螺旋道钉扩展有限元模型,通过预设横向、竖向微裂纹以及单条和多条微裂纹工况,分析研究了扣件螺旋道钉的裂纹发展过程.结果表明,由于螺旋道钉的道钉头部和螺杆结合部位存在较大的结构尺寸变化,导致了该处存在较大的应力集中,易萌生微裂纹,并在列车荷载长期作用下裂纹沿着横向扩展、贯通.对比看出,研究结果与实际扣件螺旋道钉的断裂形式相符,表明采用扩展有限元方法能很好地进行扣件螺旋道钉的断裂过程分析.此外,为避免和减少螺旋道钉的断裂发生,分13种工况研究了螺旋道钉肩胛过渡圆弧的设置.研究结果建议,对于T30×155型扣件螺旋道钉应设置1.6 mm半径的过渡圆弧,相对于不设置过渡圆弧,最大应力可减小40%.

Fracture Process Analysis and Improvement Approach of Subway Fastener Screw Spike

Based on field investigation and experimental data, extended finite element method was introduced to establish uniform stress model and non uniform stress model under adverse conditions. Horizontal, vertical micro cracks, single and multiple cracks were set up to study the crack development process of the fastener screw spike. The result shows that due to abrupt size change in the screw spike combining site of the head and screw, there is large stress concentration, easily generates micro cracks and then lateral extends, eventually breakdown under long term train load. Simulation resultswere in conformity with actual fastener screw spike fracture form, so the extended finite element method is very suitable for fastener spike fracture process analysis. In addition, in order to avoid and reduce the screw spike rupture occurring, 13 kinds of working condition were studied about fastener screw spike shoulder transition arc setting. The result shows that the ideal arc radius is 1.6 mm for T30×155 type fastener screw spike, and the maximum stress will be reduced by 40% relative to without transition arc.