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The thesis mainly proposed a novel design method for Sinusoidal Pulse Width Modulation (SPWM) controller based on modulation waveform cycle normalization. T is the period of sinusoidal modulation waveform, and T/n is the cycle of triangular carrier. Shift registers and adders of SPWM controller were designed to translate the 2n numerical value for SPWM waveform on-off switching points, which were calculated offline, to control the level of the outpout SPWM waveform,which is the key point of modulation waveform cycle normalization. In the thesis RTL function simulation verification by ModelSim and testing for FPGA have been achieved successfully. The results show that the novel SPWM controller is reliable, which has practical significance.

Steel 35CrMo is widely used to produce the principal axis of machine, but the principal axis is often abraded or scratched during its service. The CoCr coating produced by electro-spark deposition on the machine principal axis of 35CrMo can solve the problem and resume its application. In this study, the interface behavior of joint between the CoCr coating and the 35CrNo steel substrate was studied. The microstructure of CoCr coating was also observed and analyzed by using a scanning electron microscope with an energy dispersive X-ray spectroscopy analysis. A narrow layer of elements diffusion containing Co0.72Fe0.28, CoCr and Co7Fe3 was detected in the bonding interface between the CoCr coating layer and the 35CrMo steel substrate. The CoCr coating with higher microhardness was obtained on the substrate. The results reveal that a joint between the CoCr alloy and the steel 35CrMo substrate with stable quality can be obtained by electro-spark deposition.

Strengthened coating on the surface of 35CrMo steel alloy was deposited by electrospark process using NiCr electrode. The bond strength and microhardness of the coating was checked and the microstructure of the strengthened coating was analyzed using the optical micro-scope, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrum (EDS). The results show that the bond strength between the coating and the base metal is 495.1MPa, and the hardness of the coating surface is about 2 times than that of the base metal, and the property of the workpieces surface has become better. The coating is a metallurgical reacting bonding layer between the base metal and the NiCr electrode, and its main ingredients are FeNi and NiCrFe.

The microstructure of structural steel (40Cr) and tool steel (T10A) samples and its surface are respectively fined through salt-bath cyclic quenching (SCQ) and high frequency hardening (HFH), then the superplasticity is studied under isothermal compressive superplastic deformation condition. The experimental results indicate that the true stress-strain curves of 40Cr and T10A steel are separately shown to take place obvious superplastic flow characteristic at the temperature of 730-770 °C 710-770°C and at the initial strain rate of 1.7-50×10 -4 s -1 2.5-8.3×10 -4 s -1 , its strain rate sensitivity are respectively 0.30-0.38 and 0.32-0.50, the steady superplastic flow stress are respectively 60-70 MPa and 35-45 MPa, the superplastic flow activation energy are respectively 198-217 KJ/mol and 182-195 KJ/mol, and they are close to α-Fe grain boundary self-diffusion activation energy. The compressive superplastic constitute equations of both steels are correspondingly set up. Due to the finer microstructure of HFH, it appears higher strain rate sensitivity value, smaller the steady superplastic flow stress and the superplastic flow activation energy, so it has better capability of superplastic deformation.

In the paper, the Sn2.5Ag0.7Cu solder alloy is selected out by comprehensive comparison. Minute a mount of rare earth (RE) was added into Sn2.5Ag0.7Cu solder aiming at examining the effect of different a mount of RE on microstructure,the physical properties and mechanical properties of Sn2.5Ag0.7Cu solder.the aim is to define the optimization range of the RE addition.