This paper presents a new rotor profile of roots vacuum pump composed of arc, involute and cycloid.It’ s whole tooth profile which is described exactly by combining the meshing principle of gears with parameter equation. The performance of meshing of two rotors is improved without profile interference and packet gas, which are the problems of conventional involute profiles. The work provides new theoretical basis for digital design of new rotor profile, its meshing analysis, dynamic emulation, kinematics and dynamics analysis.
By adopting the method of reducing the pressure angle, this paper carried out an improvement on the profile of traditional involute rotor. It’s whole tooth profile is described exactly by combining the meshing principle of gears with parameter equation. The study made clear that there were drops to some extent on the area utilization coefficient of the improved profile of involute rotor when compared with the traditional profile of the same structure, yet its coincident degree was increased along with the decreased of pressure angle. It raised the stability of rotor transmission and in the mean time raised the bearing capacity of rotor transmission.
The characteristics of stress induced ε martensitic phase transformation and its stress relaxation during tensile stopped loading of Fe-17Mn-5Si-10Cr-5Ni alloy under constant strain constraint were studied by X-ray diffraction. The results showed that the amount of stress-induced martensite of the alloy could be increased effectively under the constant strain constraint condition when the constant strain stopped loading for 0~10 min. The stress relaxation ratio of Fe-Mn-Si memory alloy increased sharply when the constant strain stopped loading for 0~5 min, and the relaxation ratio increased slowly after 5 min, indicating that the stress-induced γ→ε phase transformation was mainly completed within 5 min. Thermo-mechanical training not only improved the shape memory effect of Fe-Mn-Si memory alloy, but also reduced the stress relaxation ratio of the alloy. The characteristics of Fe-Mn-Si memory alloy should be considered when it was applied in practical engineering.
The dissimilar joints of Fe-17Mn-5Si-10Cr-5Ni memory alloy and 304 stainless steel were welded by 5 kw transverse flow CO2 laser. The microstructure, morphology and composition of the welding of the dissimilar joints were analyzed by metallographic microscope, field emission scanning electron microscopy. The results showed that the crystals of dissimilar joints of Fe-17Mn-5Si-10Cr-5Ni memory alloy and 304 stainless steel were symmetrically distributed on both sides of the joint weld center. At Fe-17Mn-5Si-10Cr-5Ni memory alloy close to the side of the weld, ε martensite phase was also found, which was caused by the γ→ε martensite transformation induced by the residual stress. The distribution of dissimilar joint weld elements was in zones obviously, the distribution mode was related to the unique keyhole effect of laser welding, and the weld center metal was still Fe-Mn-Si memory alloy, which had the characteristic of the inverse phase transition of the stress induced martensite.
The paper analyzed the martensite transformation characteristic of Fe-Mn-Si alloy by XRD analysis and tensile test under different deformation condition. In this study, the amount of ε martensite of Fe-17Mn-5Si-10Cr-5Ni alloy was lower than that of Fe-17Mn-5Si-2Cr-2Ni-1V alloy under the same deformation condition, but the change rate of ε martensite was much higher than that of Fe-17Mn-5Si-2Cr-2Ni-1V alloy, and the stress relaxation rate of the both alloys increased with the increase of the stop loading time, and the relaxation rate of the Fe-17Mn-5Si-10Cr-5Ni alloy was obviously higher than that of Fe-17Mn-5Si-2Cr-2Ni-1V alloy. (Abstract)
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