Effect of contact forms on the wear of hard silicon surfaces by soft polymers
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Effect of contact forms on the wear of hard silicon surfaces by soft polymers Zhaoxiang ZHANG1,2,3, Xiaohong JIA1,2, Fei GUO1,2,*, Zhongde SHAN3, Yuming WANG1,2 1
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
2
Joint Research Center for Rubber and Plastic Seals, Tsinghua University, Beijing 100084, China
3
State Key Laboratory of Advanced Forming Technology & Equipment, China Academy of Machinery Science & Technology, Beijing 100044, China
Received: 15 August 2019 / Revised: 05 November 2019 / Accepted: 18 February 2020
© The author(s) 2020. Abstract: The mechanism of hard surfaces worn by soft polymers is not clearly understood. In this paper, a new hypothesis has been proposed, it holds that the stress acting on the hard surface under certain working conditions is the main reason for wear of the hard surface by a soft polymer. The hypothesis was investigated by changing the contact form between tribo-pairs. For this, friction tests between six polymer spheres and smooth, rough, and inclined monocrystalline silicon surfaces were carried out. The results show that for the same tribo-pair, the silicon surface will not be worn in some contact forms, but in other contact forms it will be worn. We believe the wear of hard surface by a soft polymer is the result of the combined stress state action on the hard surface. Keywords: polymers; silicon surface; wear; combined stress
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Introduction
In recent years, polymer has been widely used in engineering because of its light-weight, high specific strength, corrosion resistance, and low friction coefficient [1, 2]. Among these applications, tribo-pairs of hard and soft polymer surfaces are widely used in many fields, such as seals, gears, lathes (cutting), and artificial joints [3−6]. When soft polymer and hard material are used as friction pair, it is usually expected that the soft material is the one that will be worn out, and the theory of surface wear related to material hardness is put forward [7]. The theory is used to predict the wear behavior of materials and, based on this theory, ways to enhance the wear resistance of polymer surfaces were also proposed [8, 9], however, the foundation of these efforts is that hard surfaces are not worn out by the soft polymers. Since the 1960s, researchers have observed the
unusual phenomenon that a metal surface with a very high hardness can be worn out by soft polymers. Specially, a systematic review of these research was presented by Zhang and He in 2004 [10]. Since the wear of hard surfaces by soft polymers becomes an established physical phenomenon, a series of theories have been put forward to explain this unusual phenomenon. Among these theories, there are four primary ones: 1) The mechanism of adhesive wear caused by a polymer–metal reaction was proposed by Vinogradov et al. [11], and developed by Zhang et al. and Wilches et al. [12, 13]. It is thought that when a polymer with active functional groups rubs against the metal surface, t
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