Direct drive motor-pumps have attracted a lot of attention from researchers because of high efficiency and compact structure. This paper presents a new type of direct drive motor-pump, which integrates the structure of the radial piston pump and axial-flux permanent-magnet machine. The rotor of the disc motor is fixedly connected to the pump rotor, and the new pump uses a new type of distribution shaft for oil distribution. This structure reduces the intermediate transmission mechanism, and the application of the disc motor further reduces the axial size, the overall volume, and heat dissipation. The efficiency of the entire system has been improved. The three-dimensional finite element method is used to dynamically analyze flow field in the flow channel, which is extracted and simplified. The flow and pressure of the pump meet the design requirements in the simulation. A disc motor was designed for the pump, and the theoretical formula of the disc motor was derived. The initial size of the motor was obtained. The response surface method and three-dimensional finite element are used to optimize the corresponding axial-flux permanent-magnet machine. Loading the torque condition of the pump to the load end of the motor, the response of the motor meets the requirements.

This study proposes a new type of tri-screw pump, which has a 1:2:3 ratio of the active diameter of the screw, the diameter of the pitch circle, and the top diameter of the active screw. Fixed width correction method of the driven screw is also proposed to avoid wear of tooth top. The mathematical model of active and driven screws is established. To avoid the wear of the tooth top arc, several transition patterns are proposed, and the transition curve in the form of a circular arc is deduced. The designed screw curve is grinded, and the tri-screw pump is assembled. The hydraulic pump test bench is tested using the overflow valve to perform pressure loading of 3–5 MPa on the outlet of the screw pump. The outlet flow rate and pressure are tested, and results indicate that the output flow of the pump conforms to the designed flow rate. This study establishes the detailed equation of the end face profile of the tri-screw pump (active and driven screws) and corrects the arc profile of the line angle.

A laser-assisted high-speed shearing (LAHSS) method has been proposed for metal bars, which prefabricates equally spaced fracture-start kerfs by Nd:Yag laser to make stress concentration, and applies a high-speed load to complete fracture separation. Comparative tests were conducted for Q235, 40Cr, and 304 steel bars, and the effects of fracture-start kerfs and axial clearance were investigated on the fracture section. Moreover, the fracture behavior was demonstrated by numerical simulation, and the micro-fracture mechanism was revealed by fractographic analysis. The numerical simulation results show that the material damage concentrates along with the kerf tips with peak equivalent plastic strain, and the corresponding stress triaxiality drops to almost zero at the kerf tip, which reveals that the material is subjected to pure shearing at kerf tip; the Max. loading force is reduced by 15.2%–29.6%, and the impact energy is decreased by 29.8%–46.9% for the three types of bar material. The experimental results showed that the fracture-start kerfs effectively inhibited the plastic deformation stage, and higher precision blanks were obtained in the LAHSS test: roundness error improved from 2.7%–10.9% to 1.1%–2.6%, Max. bending deflection decreased from 1.3–3.4 mm to 0.4–1.0 mm, and flatness error dropped from 0.9–3.3 mm to 0.3–0.7 mm. The fractographic analysis reveals that the crack initiation is related to alternative V-shape micro-notches at the laser-affected zone; the predominant fracture mechanism involves mode II microvoid coalescence at the main fracture plane; smaller and less elongated dimples were formed in 40Cr steels due to higher number density of grains and pinning effect of second-phase particles compared to Q235 and 304 steel bars.

This paper aims to analyze the flow characteristics and fluid torques in a direct drive rotary control valve with a novel structure, and based on the computational fluid dynamics method, the advantages of improved structure are verified. With the establishment of the valve structure and the simulation model, the sliding mesh model and moving region grid are applied to simulate the complete opening and closing process of the valve at dynamic conditions. The results present that the fluid torques generate resistance torques during the increasing process of flow area while providing driving torques in the decreasing period of flow area, which is consistent with the theoretical analysis. In addition, the flow regulation of the fluid chamber is conducted with the computational fluid dynamics method and experimental test, which exhibited disagreement due to the oil leakage phenomenon. The simulation results and experimental results both convince the pressure and flow characteristics, and the improved valve model shows decreased fluid torques of around 17% compared with the original one under the system pressure of 6 MPa.