The development of oil and gas pipelines in the direction of large diameter, high pressure, high steel grade has put forward higher requirements for pipeline inspection technology. Traditional magnetic flux leakage (MFL) internal inspection techniques suffer from low micro-metallic defect inspection rates and are significantly affected by the velocity effect. Similarly, eddy current (EC) internal inspection technologies exhibit limitations in the inspection capability of internal wall defects and are noticeably influenced by lift-off effects. This paper addresses these challenges by analyzing the signal patterns of pipeline defects under the superposition of axial direct current constant magnetic fields and radial alternating magnetic fields, considering the impact of velocity effects on defect signals. A novel approach is proposed, combining MFL and EC inspection methods for inspecting micro-metal loss defects, referred to as the magnetic-electric composite inspection method. A dynamic and fast inspection magnetic-electric composite (MagEC) probe is developed to implement this approach. Laboratory experiments were conducted to test the inspection capabilities of the probe for crack-like defects and pinhole defects. Cracks with a minimum width of 0.1mm and pinhole defects with a diameter of 3mm and above can be inspected. The probe was further incorporated into a 1219 mm multi-physics field comprehensive internal inspection device, and pulling tests were conducted. The results indicate that the magnetic-electric composite probe can effectively identify various types of pipeline micro-metal defects, with differential sensitivities of the MFL and EC sensors to internal and external wall defects.

35CrMo steel is a widely used material in machinery equipment for the petroleum industry. With the improvement of exploring technology, some particular complex features cannot be achieved with traditional processing methods. However, electrochemical machining provides a potential solution to such problems, especially in the machining of the turbine blades of turbine drilling tools, in which the surface behavior of the workpiece is an important basis for judging the machining effect. To investigate the surface behavior of 35CrMo after electrochemical machining, the electrochemical machining experiment of 35CrMo steel was conducted by a self-made experimental system. Effects of the electrolyte type, concentration, and current density on surface quality were investigated in this study. The surface characteristics of 35CrMo steel were analyzed under different current densities in three different electrolytes—NaCl, NaClO₃ and NaNO₃—with different concentrations. Based on the obtained results, an optimum machining plan was obtained. The principle of the electrolysis reaction of 35CrMo steel in NaCl, NaClO₃ and NaNO₃ electrolytes were studied as well. Experimental results showed that the best surface quality of 35CrMo steel was achieved under an NaClO₃ electrolyte concentration of 200 g/L and current density of 30 A/cm². The results in this paper provide a theoretical basis for the effective machining of complex parts such as downhole turbine blades.

Ceramic materials possessing the properties of high-strength and rigidity are widely used in industry. The shell nacre has a layered structure containing both macroscopic and microscopic levels and is equipped with superior qualities regarding hardness and strength. Therefore, the ceramic composites with a nacre-like layered structure have the potential to be utilized as sliding bearings employed in the harsh conditions of wells. For the purpose of this paper, a porous Al₂O₃ ceramics skeleton with nanometer powder is prepared using the freeze-casting method. Then the porous ceramic skeleton is filled with polymer polymethyl methacrylate (PMMA) through mass polymerization to produce a bionic Al₂O₃/PMMA composite with a lamellar structure. The properties of the prepared composite are determined by the analysis of micro-hardness, fracture toughness, friction coefficient, wear scar diameter, and the morphology of the worn surface. Consequent results indicate that elevation in the A1₂O₃ powder, which acts as the initial solid phase content, prompts the ceramic slurry to exhibit an increase in viscosity and a gradual decrease in the pore size of the ceramic skeleton. The prepared layered Al₂O₃/PMMA composite possesses high fracture toughness, which closely resembles that of Al, is approximately four times that of the matrix of the Al₂O₃ ceramics and 16 times that of the PMMA. Three kinds of composites containing different solid phase content are subjected to testing involving lubrication by water-based drilling fluid to determine the friction coefficient of each. The results indicate that an increased load leads to a decreased friction coefficient while the impact of speed is not evident. Under dry conditions, the friction coefficient of three different composites tested, declines with elevated load and speed. With the use of water-based drilling fluid as lubrication, the wear scar diameter increases at higher speed, while dry conditions denote increased load. Abrasive wear is determined to be the principal form of erosion of layered Al₂O₃/PMMA composites.

Owing to the requirements for high performance and long life, the friction and wear problems of rolling piston type rotary compressors have drawn much attention. Various theoretical models have been developed and improved to reveal the inner state of the compressor and obtain the optimization schemes. However, there remain some disadvantages and research gaps in the corresponding modeling and mixed lubrication analyses, and a comprehensive summary is lacking. To have a better understanding of the research status, this paper reviews the theoretical model development and mixed lubrication analyses of the compressor in the past decades. The determination of compression pressure, the modeling process of moving components, and the key findings are presented in detail. On this basis, some important influencing factors and the problems remaining to be solved are also discussed. This paper provides multifaceted guidance for manufacturers and researchers to conduct further theoretical analysis and optimal design.