A 7-DOF half-car dynamic model which includes the cab mounting system and seat suspension system was established to study the performance of active seat suspension. The optimal control method was applied to design the active control system. Two dynamic simulation models of the passive seat suspension and the active seat suspension were set up by Matlab/Simulink, and the performance of the passive and active seat system was simulated in the time and frequency domain. The simulation results show that the active seat suspension can greatly improve the vehicle seat performance and the study has supplied the academic reference in the applications of the active seat suspension.
In this study, Mg2Si in in-situ Mg2Si/Al composites were subjected to modification treatment using rare earth element Holmium (Ho). The phase composition and microstructure before and after modification of Mg2Si were also analyzed using X-ray diffraction (XRD) and optical microscope (OM); in addition, its mechanical properties were detected as well. The results showed that moderate addition of rare earth element Ho in in-situ Mg2Si/Al composites presents good modification effects on Mg2Si, the morphology of primary Mg2Si was changed from cross shape before modification to dispersed irregular mass; optimal modification effect was obtained when 0.4% rare earth element Ho was added. Under this condition, the average size of primary Mg2Si was decreased from 74 μm before modification to 16 μm; its mechanical properties were promoted significantly; and its tensile strength increased from 134 MPa before modification to 174.6 MPa, its brinell hardness elevated from 76 HB to 90 HB.
The effect of Al-10Sr master alloy modifier with different content on the microstructure and properties of as-cast Al-12.6Si-0.35 Mg alloy was investigated. The results show that, eutectic silicon varies from original needle and flake to fibrous shape; The shape, size, and quantity of α -Al all changed; When Sr content is 0.023%, the modification effect is most ideal, α -Al shows the highest quantity and smallest size. Meanwhile, the tensile strength and elongation of the alloy reach to the optimum values of 248.2 MPa and 7.2% respectively. These two values are 1.34 and 2.77 times higher than the 185 MPa and 2.6% before modification respectively.
In this study, we conducted heat treatments on W6Mo5Cr4V2Si steel using different annealing, quenching, and tempering processes. Meanwhile, the microstructure and hardness performance of this steel are analyzed. The results showed that, in the annealing temperature range of 790°C-870°C, the higher the annealing temperature was, the better the annealing effect that W6Mo5Cr4V2Si steel presented; W6Mo5Cr4V2Si steel exhibited the lowest annealing hardness of 22.6 HRC after annealing at 870°Cfor 2 h; In the condition of annealing at 830°C for 3 h, quenching at 1200 °C around, and tempering temperature range of 400 °C-700 °C, W6Mo5Cr4V2Si steel showed the highest hardness at tempering of 560 °C around, which is about 66.7 HRC. The tempering structure of this steel was mainly composed by needle or strip-typed martensite, a small amount of residual austenite, and carbide particles.
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