Abstract
Experimental research is carried out to reveal the static frictional behaviors of rubber pipe contact systems. This research is motivated by deep water pipe-laying operations where rubber blocks are used to clamp the pipe to supply sufficient static friction. Within this context, a friction testing instrument has been designed to mimic a situation of the beginning of the pipe-laying installation. Using this instrument, the maximum static friction forces (F) of a rubber pipe contact system are tested. The results show that the ultimate values of the static frictions fluctuate due to the increasing rate of the tangential load (FT). The evolution of contact between rubber and polymethyl methacrylate (PMMA) pipe is observed to identify the formation and propagation of the folds within the apparent contact area. In addition, it is confirmed that the evolution of contact is influenced by the folds and creep of the rubber surface. The creep deformation takes primary effect in accelerating the separation of the interfaces of contact during relative high normal loads (20, 30, 40 N) and low increasing rate of FT; whereas for all of the testing normal loads (10–40 N), the propagation of the folds release the energy which is stored in the interface of rubber when the increasing rate of FT is high. Therefore, the fluctuation of the maximum static friction of the contact system can be regarded as a consequence of interaction of the creep and folds. Furthermore, the instability of the coefficient of static friction in this test has been examined, and it indicated that the creep and folds could affect the static friction distinctly within a certain range of a normal load. This research is beneficial for arranging appropriate normal loads and laying speeds to avoid pipes slipping during a pipe-laying operation.
Highlights
Deep water pipe-laying is a standard industrial process for offshore pipeline installation or maintenance [1,2,3,4]
The propagation of the folds on the rubber surface becomes distinct with the increasing rate of the tangential load and makes the critical value of the tangential load that initiates the macroscopic slip between interfaces increase
The results show that values of the maximum static friction (F) increase with an increasing normal load, whereas it fluctuates due to different increasing rates of tangential load
Summary
Deep water pipe-laying is a standard industrial process for offshore pipeline installation or maintenance [1,2,3,4]. The tensioner is one of the key pieces of equipment for the pipe-laying operation. Rubber blocks are fixed on creeper treads of tensioner against a pipe wall with normal loading. The static friction between rubber blocks and the pipe wall is used to counteract the deadweight of pipeline [5]. The contact between the rubber blocks and the pipe wall can be seen as a soft contact of static friction during the pipe-laying operation. Rubber materials are working in great deformation due to their low elastic modulus when in contact with a rigid substrate. Tribological behaviors of rubber in soft contact is of paramount
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