Deguo Wang

Tribological Behaviours of Wax-in-Oil Gel Deposition in Orthogonal Cleaning Process

Tribological behaviour of wax-in-oil gel deposition at orthogonal cleaning process has been directly observed with a custom-built experimental setup. Experimental results show that the chip formation of wax scraping is due to rubber tribology of elastomer disc. The scraping chip instability arises from a competition between scraping forces and the adhesion forces. An analysis of debris-material removal rate in wax scraping with negative rake face has been carried out. The study has also shown that the wax-scraping force component is sensitive to rake angle, which may be used as primary basis for developing wax-removal estimating strategies. Flank face wear results in a substantial increase in the wax-scraping force, which should be incorporated into the wax-cleaning efficiency predictive model. The behaviours of the residual phenomenon depend on the inlet aggregation in orthogonal wax-cleaning process.

Effects of Microscale Particles as Antiwear Additives in Water-Based Slurries with Abrasives

ABSTRACT Abrasive wear is the dominant cause of tool failure in the process of mining and petroleum/gas drilling. This research investigated the effects of two additives, polystyrene and silicon nitride, on the tribological properties of water-based slurries with silicon dioxide or alumina abrasives. A pin-on-disk configuration was utilized to evaluate the performance of the additives for a steel–steel contact. Experimental results showed that polystyrene particles were able to reduce wear but friction increased simultaneously. On the contrary, silicon nitride particles exhibited excellent performance on both wear resistance and friction reduction. Results in this study indicated that the addition of appropriate additives was able to improve the tribological properties of slurries with abrasives.

Abrasion–Corrosion Behaviors of Steel–Steel Contact in Seawater Containing Abrasive Particles

ABSTRACT Materials working in slurries containing seawater and abrasive particles degrade gradually because of the synergic effects of mechanical wear and electrochemical corrosion. In this study, the abrasion–corrosion behaviors of a steel–steel tribopair in an environment with artificial seawater and SiO2/Al2O3 particles were investigated. Corrosion is responsible for surface degradation at low concentrations of SiO2 particles, whereas abrasion is the primary cause for steel damage at high SiO2 concentrations. When Al2O3 particles were used, abrasion was found to be the dominant factor for material loss at all concentrations. Results from this study indicate that at low concentrations of hard particles, abrasion–corrosion behavior is determined by the properties of particles.

Tribological Properties of Sliding Shale Rock–Alumina Contact in Hydraulic Fracturing

Tribological properties of rock/metal/ceramic/rock contact determine the behaviors of earth-moving activities. In this study, tribological performance of shale rock–alumina contact was examined. Experimental results show that friction of the contact is determined by liquid media at the interface. Tribofilm is found to form on the wear track. According to elementary analysis, hard materials in original shale rock or generated during sliding process aggregate on the surface, producing the tribofilm. Coefficient of friction between shale rock and alumina increases with load, which is attributed to increased real contact area under higher load. Findings in this research provide preliminary understanding of tribological properties of shale rock–alumina contact, which benefits further study of rock–ceramic contact and related industrial applications.

Frictional Behavior of Wax–Oil Gels Against Steel

Frictional behavior of wax–oil gels against steel has been investigated using a homemade tribometer to estimate the frictional resistant force produced by wax plugs in pipelines pigging. Experimental results show that there are several impact factors on frictional behavior of wax–oil gels against steel, including wax concentration, normal force and velocity. Coefficient of sliding friction increases with wax concentration. Normal load and velocity have opposite impacts on the coefficient of sliding friction. The outflow mineral oil has an important impact in the frictional process. A mechanism model of wax–oil gels against steel is built based on the results.

Microbubble Phenomenon in Contact Area Between Soft Tribological Interfaces in Sliding Contact

The microbubble phenomenon in contact area between soft tribological interfaces in sliding conditions has been directly observed with a custom-built soft tribology instrument. Experimental results show that the formation of microbubble is due to surface instability. The surface instability in soft films arises from a competition between the adhesion forces and the elastic forces. There are two different mechanisms by which the microbubble phenomenon in contact area between soft tribological interfaces in sliding contact. When a shear force is imposed, the microbubble between PU and glass slide is due to surface buckling instability. For the softer rubber, the buckling does not occur in the thin interface layer between PDMS and glass slide and the contact front forms the microbubble edges. Theoretical analyses have been used to discuss the microbubble formation.

Synchronous clamping control of marine umbilical cable tensioner

The umbilical cable tensioner is a core component of deep-water oil and gas development, and it can lay and recover the umbilical cables to ensure the transmission of communication signals, electric signals or liquid injection. The displacements of tensioner’s clamping hydraulic cylinders, which are not synchronized as the nonlinear electro-hydraulic control system, results in the occurrence of the crawler mechanism’s stuck phenomenon or cause umbilical cable deformation or even cause damage by the extrusion in the umbilical cable’s clamping process. To ensure synchronous clamping, the structure scheme of umbilical cable tensioner, crawler mechanism, clamping mechanism and the hydraulic system of synchronous clamping control is designed in this study. This article also analyzes the function of structure parameters and hydraulic cylinders’ displacement, speed and acceleration, and builds the synchronous clamping mechanical model to reveal crawler mechanism’ clamping law. The study proposes the control strategy including the fast moving stage, the working stage and the pressuring stage based on proportional–integral–derivative control, and analyzes the characteristics of synchronous clamping control by building the synchronous clamping experimental platform in the lab environment. The experimental data shows that the tensioner’s hydraulic cylinders have excellent synchronous clamping performance and the theoretical analysis is feasible. The research has important guiding significance for the tensioner design, and provides theoretical support for the laying of the deep-sea umbilical cables.

Tribological Properties of Hybrid Ag4SiW12O40 Nanoparticles Multilayer Films

Inorganic-organic hybrid nanoparticles molecular deposition films were fabricated by extending the method of nucleation and growth of particles in polymer assemblies. Poly (diallyldimethylammonium chloride) (PDDA) and poly (styrenesulfonate) sodium salt (PSS) were applied as polycation and polyanion respectively. At first, PDDA/PSS films were obtained by alternately depositing PDDA and PSS on the cleaned substrate with molecular deposition (MD) method. Then, follow’s alternately dipped the precursor polyelectrolyte multilayer MD films into AgNO3 and H4SiW12O40 aqueous solutions. Repeating the above synthesis process, Ag4SiW12O40 nanoparticles were synthesized in the polyelectrolyte multilayer films in-situ. UV-vis absorption spectra indicate that the Ag4SiW12O40 nanoparticles grew gradually in the synthesis process. The structure and nanotribological properties of hybrid nanoparticles multilayer films were analyzed by atomic force microscope (AFM) and the antiwear life was analyzed by micro-friction and wear test machine. It was found that these films had small friction force and high antiwear life. The MD film had best tribological properties when the cycle number is six. Nanoparticles within the MD films can enhance antiwear life of MD films attributed to nanoparticles possess load-carrying capacity, and decrease the mobility of the polymer chain segments which can undergo reversible shear deformation.

Research on Worn Mechanism of Disc-Brake Pair Materials for Drilling Rig

A new build-up welding material for brake-disc and a new type of asbestos-free frictional material are developed, of which the tribological behaviours and wear mechanisms of build-up welding materials are discovered. XRD pattern shows that iron-base solid solution of α-Fe and Cr in build-up welding material has fine property of crack arrest, and α-Fe turns into γ-Fe under frictional heat as well as frictional austenite phase γ-(Fe, Ni) +α-Fe + carbide forms, which improves plastic deformation ability of material in wear surface and anti-thermal fatigue property of brake-disc, in addition, carbide Fe3C, Fe5C2, SiC and intermetallics NbNi, NbNi5 disperse in solid solution of α-Fe and Cr make frictional surface hardness of brake disc become higher to improve wear-resisting property of brake-disc. SEM and EDAX patterns show that the wear process of brake block and brake disc is a dynamic process of surface film generating, growing, cracking, stripping and regenerating. When frictional temperature is lower, the wear of brake block is mainly abrasive wear and that of brake disc is oxidized and abrasive wear, and their surface film breaks off mostly by fatigue flaking. When frictional temperature is higher, the wear of brake block is mainly adhesive wear and that of brake disc is adhesive and oxidized wear, and their surface film is scaled mainly by adhesive tearing.

Friction and Wear Behavior of Wear-Resistant Belts in Drill Joints for Deep and Ultra-Deep Wells

The friction and wear of an new material for the drill joint were compared with those of traditional wear-resistant belt materials using an SD-1 test rig against a 42Mn2V steel counterface under deep and ultra-deep well conditions. This provides recommendations as to the tribological application of the wear-resistant belt. The results obtained strongly indicate that the friction and wear of a polycrystalline diamond (PCD) composite are much lower than those of the traditional wear-resistant belt materials. Among those materials, the friction and wear behavior of a FeNiNb alloy are higher than those of a FeCrMnMo alloy. Of the three wear-resistant belt materials, the bilateral protection performance of a PCD composite is the best one. It is feasible to use this composite as the wear-resistant belt material in the drill joint for deep and ultra-deep wells. The dominant wear mechanism of the wear-resistant belt materials is the microcutting wear, accompanied by the adhesive one. In addition, the wear degree of the PCD composite is the least one.