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首页> 外文会议>AMD-vol.257; American Society of Mechanical Engineers(ASME) International Mechanical Engineering Congress and Exposition; 20061105-10; Chicago,IL(US) >DYNAMIC SLIP RESISTANCE AT METAL-ON-METAL INTERFACES
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DYNAMIC SLIP RESISTANCE AT METAL-ON-METAL INTERFACES

机译：金属对金属界面的动态滑移阻力

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In the present study plate-impact pressure-shear friction experiments were employed to investigate dynamic slip resistance and time-resolved growth of molten metal films during dry metal-on-metal slip under extreme interfacial conditions. By employing tribo-pairs comprising hard tool-steel against relatively low melt-point metals such as 7075-T6 aluminum alloy, interfacial friction stress of up to 300 Mpa and slip speeds of approximately 250 m/s have been achieved. These relatively extreme interfacial conditions are conducive to the development of molten metal films at the tribo-pair interface. A Lagrangian finite element code is developed to understand the evolution of the thermo-mechanical fields and their relationship to the observed slip response. The code accounts for dynamic effects, heat conduction, contact with friction, and full thermo-mechanical coupling. At temperatures below the melting point the material is described as an isotropic thermally softening elastic-viscoplastic solid. For material elements with temperatures in excess of the melt temperature a purely Newtonian fluid constitutive model is employed. The results of the hybrid experimental-computational study provide new insights into the thermoelastic-plastic interactions during high speed metal-on-metal slip. During the early part of friction slip the coefficient of kinetic friction is observed to decrease with increasing slip velocity. During the later part transition in interfacial slip occurs from dry metal-on-metal sliding to the formation of molten Al films at the tribo-pair interface. Under these conditions the interfacial resistance approaches the shear strength of the molten aluminum alloy under normal pressures of approximately 1-4.5 Gpa and shear strain rates of～ 10~7 s~(-1). It is interesting to note that the dynamic shear resistance of molten metal films decreases from ～100 Mpa to ～50 Mpa when the initial slip velocities increase from ～100m/s to ～250 m/s. Scanning electron microscopy of the slip surfaces reveal molten aluminum to be smeared on the tribo-pair interface. Photo-micrographs of the cross-section of the 7075-T6 Al alloy reveals a thin region of severe shearing deformation in close vicinity of the sliding surface. The shearing deformation manifests itself as severely deformed grains in the direction of the sliding.
机译：在本研究中，采用板撞击压力-剪切摩擦实验来研究在极端界面条件下干金属对金属滑移过程中熔融金属膜的动态滑移阻力和时间分辨生长。通过采用包括硬质工具钢的摩擦副对相对较低的熔点金属（例如7075-T6铝合金），可实现高达300 Mpa的界面摩擦应力和约250 m / s的滑移速度。这些相对极端的界面条件有利于在摩擦对界面处形成熔融金属膜。拉格朗日有限元代码被开发出来，以了解热机械场的演变及其与观测到的滑动响应的关系。该规范考虑了动态效果，导热，摩擦接触以及完全的热力耦合。在低于熔点的温度下，该材料被描述为各向同性的热软化弹性粘塑性固体。对于温度超过熔融温度的材料元素，使用纯牛顿流体本构模型。混合实验-计算研究的结果为高速金属对金属滑移过程中的热弹-塑性相互作用提供了新的见解。在摩擦滑动的早期，观察到动摩擦系数随滑动速度的增加而减小。在随后的部分过渡过程中，界面滑动发生从金属对金属的干滑到在摩擦副对界面处形成熔融的Al膜。在这些条件下，在大约1-4.5 Gpa的常压下和大约10〜7 s〜（-1）的剪切应变率下，界面阻力接近铝合金的剪切强度。有趣的是，当初始滑移速度从〜100m / s增加到〜250m / s时，熔融金属膜的动态剪切阻力从〜100 Mpa减小到〜50 Mpa。滑动表面的扫描电子显微镜显示熔融铝将被涂在摩擦副对的界面上。 7075-T6铝合金横截面的显微照片显示，在滑动表面附近很薄的区域出现了严重的剪切变形。剪切变形表现为在滑动方向上的严重变形的晶粒。

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