ISSN   1004-0595

CN  62-1224/O4

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EA4T车轴钢径切复合微动磨损特性研究

Composite Fretting Wear Characteristics of EA4T Axle Steel Under Radial and Tangential Loads

  • 摘要: 针对车辆轮轴过盈配合部存在的多模式复合微动损伤,开展了柱/柱正交接触下的EA4T车轴钢径切复合微动磨损特性研究. 结果表明:摩擦力-位移-循环次数曲线(Ft-D-N曲线)表现为3种类型:准梯形型、梯形与椭圆交变型和直线型. 分别对应完全滑移区、混合区和部分滑移区. 径切复合微动的径向力与切向位移变化周期相同,径向力随切向位移的改变而改变. 径切复合微动磨损的磨痕形貌呈彗星状,径向载荷较小侧更容易产生相对滑移,导致磨痕较深. 完全滑移区与混合区的磨损机制主要为疲劳剥落、磨粒磨损及氧化磨损. 在完全滑移区,Ft-D-N曲线为非对称的准梯形型,单次循环平均磨损量先增加后降低. 在混合区,损伤程度降低,磨痕表面存在轻微的犁沟和剥落. 在部分滑移区,接触区中心存在黏着,接触边缘发生微滑,损伤最轻微,磨损机制主要为黏着磨损.

     

    Abstract: The continuous escalation in operational speed and service mileage of Chinese rail transit vehicles has induced fretting wear in the wheel and axle department, emerging as a pivotal factor restricting the secure railway operation. Focusing on the multi-mode composite fretting wear within the interference fit between the wheel and axle, this study investigated the composite fretting wear characteristics of EA4T axle steel under cylinder/cylinder orthogonal contact, utilizing a self-developed composite fretting wear tester. The study explored fretting wear behaviors, accumulated dissipated energy, and wear mechanisms under composite fretting wear. These findings established a foundation for damage failure analysis of the wheel and axle fit part of rail transit vehicles. The system employed a horizontally mounted voice coil motor to propel tangential reciprocating motion. A tangential grating displacement encoder captured real-time tangential displacement, enabling closed-loop control. Similarly, a vertically mounted voice coil motor applied radial alternating load, and a radial force sensor collected real-time radial load, facilitating closed-loop control. The variation period for radial force and tangential displacement remained identical, ensuring that the radial force reached its maximum amplitude when the tangential displacement reached its peak. Three fundamental types of Ft-D-N curves were identified: quasi-trapezoid cycle, trapezoid and elliptic alternating cycle, and linear cycle. These corresponded to the slip regime (SR), mixed fretting regime (MFR), and partial slip regime (PSR), respectively. Wear scars exhibited a cometary appearance, with the side under a smaller radial load displaying a greater potential for relative slip, causing deeper wear marks. In the SR, the friction coefficient experienced a brief decrease after a rising phase, followed by a smooth increase until stabilization. In the MFR, the friction coefficient underwent a more prolonged decreasing phase, briefly stabilizes, and then continued to increase. The primary wear mechanisms of SR and MFR included fatigue spalling, abrasive wear, and oxidation wear. In the SR, the Ft-D-N curves assumed an asymmetrical quasi-trapezoid cycle, with the wear volume per cycle initially increasing before decreasing with the growing number of cycles. The area where chemical friction occurred also gradually expanded, leading to a rise in oxygen content. The object’s cross-section revealed significant delamination, indicating severe wear. The wear mechanism progressed from slight plastic deformation to fatigue spalling in the early stages, later manifesting as fatigue spalling, abrasive wear, and oxidation wear. In the MFR, wear was mitigated by slight ploughing and delamination at wear scars, with visible cracks extending into the subsurface. In the PSR, an adhesive region existed in the center of the contact zone, and a microslip region was observed at the edge of the contact zone. Worn pits were evident in the cross-section, with adhesive wear been the primary wear mechanism.

     

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