Is the wear coefficient dependent upon slip amplitude in fretting? Vingsbo and Soderberg revisited
Is the wear coefficient dependent upon slip amplitude in fretting? Vingsbo and Soderberg revisited
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DOI：
10.1016/j.wear.2014.11.005
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发表时间：
2015-05-01
期刊：
影响因子：
5
通讯作者：
Shipway, P. H.
中科院分区：
文献类型：
--
作者：
Pearson, S. R.;Shipway, P. H.
超过25年前，Vingsbo和Soderberg发表了一篇关于微动接触行为映射的开创性论文（O。Vingsbo，S. Soderberg，On fretting maps，Wear，126（1988）131-147）。在本文中，提出了在粗滑移微动区，随着微动位移幅值从约20 pan增加到300 pm，磨损系数增加1到2个数量级之间（定义为粗滑区的极限）。自本文发表以来，在文献中已经发表了许多关于在总滑动状态下的微振磨损的论文，其中没有观察到磨损系数对微振磨损位移的这种强烈依赖性，相反，磨损系数几乎与微振磨损幅度无关。事实上，许多研究人员已经证明，对于许多材料组合，磨损体积和接触中消耗的摩擦能量之间存在良好的相关性，另外还发现接触中消耗的能量存在阈值，低于此值时，未观察到磨损（本文给出了高强度钢微动磨损的实验数据，支持这一观点）有人认为，在得出微动磨损的磨损系数时，有两个关键的考虑因素并不总是得到解决：（i）远场位移振幅不足以替代滑移振幅（前者是后者与接触点和位移点之间系统中的任何弹性变形的总和。测量）;以及（ii）在微动磨损持续时间中存在阈值，低于该阈值不发生磨损，高于该阈值，磨损体积随着持续时间的增加而增加的速率是恒定的（该常数可以被称为磨损系数k（真））。不解决这两个问题会导致导出的标称磨损系数（k（标称））始终小于k（真）。本文提出了一个简单的分析，指出k（标称）/k（真）= 1 -A-B，其中A与错误地利用远-在计算磨损系数和B时，用场位移幅值代替接触滑移幅值与未能认识到微动磨损持续时间存在一个阈值有关，低于该阈值时不会发生磨损。A和B取决于牵引力启动滑动所需的时间（本身取决于所施加的载荷和摩擦系数）、系统刚度、所施加的位移幅度、阈值微动磨损持续时间（低于该阈值时不会发生磨损）以及试验中微动磨损循环次数。使用这些参数的典型值，k（标称值）与k（真实值）的比值已被证明在Vingsbo和Soderberg所述范围内强烈依赖于所施加的位移振幅（在此范围内比值迅速降低一个数量级）。因此，有人认为，k（真）没有表现出很强的依赖性，在微动滑移振幅，并提出了Vingsbo和Soderberg的强烈依赖性的k（标称）位移振幅并不意味着一个变化k（真），因为经常推断。有人认为，这种技术必须经常使用，以允许正确的解释磨损数据的实际滑动幅度（或能量耗散），此外，一系列的条件下，应进行实验检查，以允许阈值微动磨损持续时间低于没有发生的评估和评估其意义。(C)2014作者由爱思唯尔公司出版
More than 25 years ago, Vingsbo and Soderberg published a seminal paper regarding the mapping of behaviour in fretting contacts (O. Vingsbo, S. Soderberg, On fretting maps, Wear, 126 (1988) 131-147). In this paper, it was proposed that in the gross-slip fretting regime, the wear coefficient increased by between one and two orders of magnitude as the fretting displacement amplitude increased from around 20 pan to 300 pm (defined as the limits of the gross-slip regime).Since the publication of this paper, there have been many papers published in the literature regarding fretting in the gross-sliding regime where such a strong dependence of wear coefficient upon fretting displacement has not been observed, with instead, the wear coefficient being shown to be almost independent of fretting amplitude. Indeed, many researchers have demonstrated that there is a good correlation between wear volume and frictional energy dissipated in the contact for many material combinations, with the additional insight that a threshold in energy dissipated in the contact exists, below which no wear is observed (experimental data relating to fretting of a high-strength steel is presented in the current paper which supports this concept).It is argued that in deriving a wear coefficient in fretting, there are two key considerations which have not always been addressed: (i) the far-field displacement amplitude is not an adequate substitute for the slip amplitude (the former is the sum of the latter together with any elastic deformation in the system between the contact and the point at which the displacement is measured); and (ii) there is a threshold in the fretting duration, below which no wear occurs and above which the rate of increase in wear volume with increasing duration is constant (this constant may be termed the wear coefficient, k(true)). Not addressing these two issues results in the derivation of a nominal wear coefficient (k(nominal)) which is always less than k(true). A simple analysis is presented which indicates thatk(nominal)/k(true) = 1 - A - Bwhere A is associated with erroneously utilising the far-field displacement amplitude in place of the contact slip amplitude in the calculation of the wear coefficient and B is associated with the failure to recognise that there is a threshold in fretting duration below which no wear occurs.A and B are shown to depend upon the tractional force required to initiate sliding (itself dependent upon the applied load and coefficient of friction), the system stiffness, the applied displacement amplitude, the threshold fretting duration below which no wear occurs and the number of fretting cycles in the test. Using typical values of these parameters, the ratio of k(nominal) to k(true) has been shown to be strongly dependent upon the applied displacement amplitude over the range addressed by Vingsbo and Soderberg (with the ratio rapidly decreasing by an order of magnitude over this range). As such, it is argued that k(true) shows no strong dependence on slip amplitude in fretting, and that the strong dependence of k(nominal) upon displacement amplitude presented by Vingsbo and Soderberg does not imply a change in k(true) as is often inferred.The routine recording of force-displacement loops in fretting is a major experimental advancement which has taken place since the publication of the paper by Vingsbo and Soderberg. It is argued that this technique must be routinely used to allow the correct interpretation of wear data in terms of the actual slip amplitude (or energy dissipated); moreover, a range of conditions should be experimentally examined to allow the threshold fretting duration below which no wear has occurred to be evaluated and its significance assessed. (C) 2014 The Authors. Published by Elsevier B.V.