Minchao Cui

Finite element modeling and analysis for the integration–rolling–extrusion process of spline shaft

An integration–rolling–extrusion process is raised for the manufacture of spline shaft in this study. First, the principle and procedures of integration–rolling–extrusion process are described. Next, the finite element model with a simplified sector blank is established to obtain a practical method for the simulation of integration-rolling-extrusion process. Through the simulation results, the plastic forming mechanisms are clearly revealed. During the integration–rolling–extrusion process, the equivalent stress, deformation degree, and material flow behavior mainly distribute on the surface layer of the blank and then gradually decrease along the radial inward direction. In the core region of the blank, there are almost no effective stress distribution, deformation degree, and material flow behavior. Next, the experiments are carried out on a specialized forming equipment to verify the finite element model. The results are measured and compared with finite element results. The finite element results show a good agreement with experiments; thus, the finite element analysis on the integration–rolling–extrusion process is credible. In addition, the measurement results show that the dimensions meet the requirement of heavy truck application. It indicates that the integration–rolling–extrusion process is feasible for the manufacture of spline shaft. However, the surface quality of the formed spline shaft is not satisfying, which needs to be discussed further.

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.

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.

EXPRESS: Improvement of the Analysis of Manganese in Steel Samples Using Collinear Long-Short Double Pulse Laser-Induced Breakdown Spectroscopy (LIBS)

A long–short double pulse laser-induced breakdown spectroscopy (long–short DP-LIBS) method was employed to improve the analytical performance of LIBS for the measurement of manganese in steel samples. The long pulse with a duration of 60 μs was generated using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser which was operated at free-running (FR) mode. To investigate the detection ability without sample preparation, the steel washers were tested using single-pulse LIBS (SP-LIBS) and long–short DP-LIBS, respectively. The measurement results show that long–short DP-LIBS was able to record clear spectra from the steel washers with a surface layer. Through the observation on the laser craters with a scanning electron microscope (SEM), the results suggest that the improvement in detection ability can be attributed to the pre-irradiation effect of long-pulse laser beam. Next, the analytical performance for quantitative measurement of manganese was evaluated employing ten standard steel samples. The results show that the linearity fit (R2) of the calibration curve is 0.988 for long–short DP-LIBS, whereas, R2 is only 0.810 for SP-LIBS under the same measurement conditions. The repeated measurement results show that the average relative standard deviation (RSD) of the tested samples is 29.3% for SP-LIBS and is 10.5% for long–short DP-LIBS. The prediction results also show that the average relative error of prediction (REP) is 94.9% for SP-LIBS and is 4.9% for long–short DP-LIBS.

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.

Experimental research on the compressed joints with different geometrical parameters

In recent years, mechanical clinching has been widely used to join aluminium alloy sheets to build the automotive body. The high protrusion on the joint may limit the use of the mechanical clinching in the visible places. In order to get a lower protrusion, a compressing method was investigated in this work. Clinched joints with different geometrical parameters were used to conduct the experiments. AL5052 was taken as the material of the sheets. The protrusion of the clinched joint was compressed by two flat dies. A rivet placed in the pit of the clinched joint was used to control the metal flow in the compressing process. The top die moved downward to compress the protrusion, and the bottom die was fixed. The study shows that the tension-shearing strength and cross-tensile strength can be increased by the compressing method. The compressing method can increase the tension-shearing strength and cross-tensile strength by increasing the neck thickness. The compressed joint has larger neck thickness and lower protrusion than the clinched joint. Neck fracture mode is the main failure mode of the joints. The energy absorption can also be increased after the compressing process.