Shengdun Zhao

Plastic mechanism of multi-pass double-roller clamping spinning for arc-shaped surface flange

Compared with the conventional single-roller spinning process, the double-roller clamping spinning(DRCS) process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.

Study on warm forming effects of the axial-pushed incremental rolling process of spline shaft with 42CrMo steel

The effects of the warm forming temperature on the axial-pushed incremental rolling process were investigated through finite element analysis and experimental studies. Firstly, the principle of warm axial-pushed incremental rolling process of spline shaft was introduced. Next, the material properties of 42CrMo steel at different forming temperatures were studied to discuss the effects of the warm forming temperature. Through finite element analysis, the simulations of the axial-pushed incremental rolling process were carried out to investigate the effects of the warm forming temperature on rolling forces. The results indicated that the axial and radial forces on the rolling dies were both reduced at the warm forming temperature. Finally, the experiment studies were carried out on a warm axial-pushed incremental rolling equipment. The dimensional precision, microstructure, and hardness of the formed spline shafts at warm temperature were compared with those of the formed spline shafts at room temperature. The results indicated that the spline shafts, which were formed at the warm temperature, possesses of a good dimensional precision and excellent performance. The results in this paper demonstrated that the warm forming temperature has the positive effects on the performance improvement of the axial-pushed incremental rolling process of spline shaft.

Comparative investigation of auxiliary processes for increasing the strength of clinched joints

Mechanical clinching has been widely used in the field of automotive industry in recent years. However, the clinched joint has a lower static strength than spot welding. In order to increase the static strength, a comparative investigation of two auxiliary processes for increasing the strength of clinched joints was carried out. One auxiliary process needs a rivet, while another auxiliary process needs a bumped die. Tension-shearing strength tests and cross-tensile strength tests were conducted to assess the static strengths of the joints after different auxiliary processes. Failure mode of all the joints was neck fracture in the tension-shearing strength tests and cross-tensile strength tests. Geometrical parameters of the joint profile were also investigated by comparing the two auxiliary processes. The values of energy absorption of different joints were obtained by measuring the areas between the force–displacement curve and x-coordinate. The two auxiliary processes were proved to be effective. The auxiliary process with a rivet has a better performance than the auxiliary process with a bumped die.

Hybrid-loop servo control system of double toggle mechanical press for flexible forming process based on sliding mode control and neural network techniques

A hybrid-loop servo control system based on sliding-mode control and neural network control is proposed in this article to realize flexible forming process on a double toggle mechanical press. First, kinematics and dynamic analysis of the drive system are conducted to derive the control objective behavior. Then, the structure of the hybrid-loop system is introduced; sliding-mode control is applied to compensate the punch position errors. In the inner loop of the servo motor, complementary sliding-mode control is used to track the motor rotation angle, and a radial basis function neural network estimator is applied to eliminate the considerable load disturbances in the stamping stage. Finally, experimental hardware is constructed and a compound blanking and drawing process is carried out to validate the proposed servo control system in practice. With different materials and drawing depth, high tracking accuracy and robustness are exhibited to realize favorable forming performance.

Study on the 12-10 flux switching integrated-starter-generator for hybrid electric vehicle application

An integrated-starter-generator (ISG) system provides a cheap hybrid power strategy for hybrid electric vehicles (HEV). 12-10 flux switching integrated-starter-generator (FSISG) is one type of ISG machine, which employs the flux switching topological structure to improve the performance. In this paper, a prototype of 12-10 FSISG with the improved structure, which was employed to improve the manufacturability, was analyzed and studied. Through numerical studies, the influences of the improved structure and the characteristics of 12-10 FSISG were revealed. According to finite element analysis (FEA) results, the output voltage of FSISG can be considered as sinusoidal voltage. The results of the output torque show that the excitation current density of FSISG should be limited to less than 9 A/mm2 to avoid serious magnetic saturation. Next, the experimental tests of the prototype were carried out on the testing platform. In generating mode, the experiment results indicate that FSISG can output electrical energy with high efficiency in wide speed and torque ranges. In starting mode, the maximum starting torque of the prototype is 10.5 Nm. During the starting procedure, the prototype reaches a steady state rapidly. In the variable load conditions, it shows a rapid response ability to the changes of loads. According to the experiment results in this paper, the 12-10 FSISG has shown a promising performance for HEV application in both generating mode and starting mode.

Designing of an electromagnetic driver for the reversing valve of CNC die forging hammer

This paper is aimed at the solution of the driving actuator of the reversing valve, which is the core component of CNC die forging hammer. The proposed electromagnetic drive method contributes to a precise control of the valve spool position and eliminates the transmission mechanism and hydraulic circuits. The complete structure and the topology structure of the electromagnetic part are designed to guarantee its high controllability and robustness. The structure parameters of the electromagnetic part are calculated based on the driving requirement of the reversing valve. With the finite element analysis of the direct driving part, saturation phenomenon of the magnetic circuit is eliminated and optimization of the output force ripple is performed. The output force of the electromagnetic part is simulated to reach 1000 N with a rated speed of 0.55u2009m/s, which satisfies the drive demand of the reversing valve spool and the ripple amplitude of the output force is reduced by 43.9%. The operational test of the electromagnetic direct drive component is conducted to verify the finite element method simulation method and shows an expected performance.

Computational fluid dynamics and experimental analysis on flow rate and torques of a servo direct drive rotary control valve

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 6u2009MPa.

Study on the control circuits of Flux Switching Integrated Starter and Generator for HEV application

In order to solve the global environmental and energy problems, Flux Switching Integrated Starter and Generator (FSISG) was applied to Hybrid Electric Vehicle (HEV) application. The control circuits are vital for the FSISG system, which were designed and studied in this paper. The structure of the control circuits of FSISG system was introduced. Then the experimental studies were carried out based on the drivers which were made according to the designed control circuits. In generating mode, the output voltages of FSISG show a high precision and a well stability in wide rotational speed range. In starting mode, FSISG system shows a well dynamic performance under the different load conditions and load variation condition.

A Study on Experiments and Simulations For Ductile Fracture of Isotropic Material Using Rousselier's Damage Model

Ductile fracture has been a hot topic for a long time for its importance to mechanical design in evaluating the risk of failure. In this paper, the A5052BD-H14s ductile fracture is studied using a new constitutive equation based on the continuum damage mechanics. A novel full-implicit stress integration algorithm is developed based on Rousseliers damage model and implemented into finite element analysis (FEA) models by the ABAQUS/Explicit using the user material subroutine. The tensile tests of A5052BD-H14 with notch were taken and the load-displacement curves were recorded. By simulations, the evolutions of the void volume fraction are obtained and can be used as calibration for the critical void volume fraction. The validity of the damage model and the proposed stress integration algorithm are verified by comparing the experimental results and the simulation results. Further, by using the critical void volume fraction and element deletion, the simulation results show that this method is reliable, and can be used to predict the fracture of metals.