To analyze the influence of the leaf spring hysteresis characteristics on the vehicle body vibration performance, it is necessary to take the physical nonlinear factors into account in the suspension dynamic modeling analysis. The hysteresis characteristics of the leaf spring are caused by the contact and friction between the spring pieces. Besides that, the damping elements of the suspension system are also strongly nonlinear. And hence this article presents a generalized Maxwell-slip damper (GMD) model, which can represent the general hysteresis characteristics of the suspension system. The GMD model incorporates spring stiffness and nonlinear damping in addition to spring friction using the Maxwell model. Then the effects of various parameters on the hysteresis characteristics of GMD model are analyzed and verified by simulation and bench experiments. In addition, an eight degree of freedom (8-DOF) full vehicle model capturing some frictional characteristics was established to study vehicle vibration performance under random road excitation. At the same time, the actual vehicle test is conducted under different road conditions. Ultimately, the results of the nonlinear suspension model have a reasonable agreement with the experimental results, which further demonstrates the credibility of the proposed GMD model. That is, the full vehicle dynamic model with friction force is entirely accurate and useful. The proposed nonlinear hysteresis model may be instructive for accessing the vehicle vibration response to further study the direct effects of friction on vehicle handling and driver feedback.
The integral model is used to predict the concentration field, only suitable for low-pressure leakage, while the virtual nozzle model is widely used in highpressure leakage but ignores the friction between the hydrogen and the tube wall during the leakage. We modified the virtual nozzle model by adding the gas-wall friction loss term to the momentum conservation equation. A theoretical model of a high-pressure under-expanded jet is proposed by combining the integral model with the improved virtual nozzle model, which was validated by a series of helium (instead of hydrogen) dispersion in an unenclosed environment. And then the high-pressure hydrogen leakage system was set up to investigate hydrogen concentration along the centerline of the jet was measured under different pressures. Results show that the mole fractions along with the axial distance all comply with the hyperbolic decay law. Within the range of 40 cm < z < 100 cm, at other pressures of 1, 2, 4 MPa, the minimum deviations of high-pressure under-expanded hydrogen leakage prediction model and experiments are 1.67%, 1.37%, 1.33%, respectively. The study is adequately precise to predict high-pressure leakage concentration and also gives ideas about the installation position of the hydrogen sensor in engineering.
As electrolytic plasma polishing (EPP) offers the advantages of strong shape adaptability, high efficiency, and environmental friendliness, it has great application prospects in biomedical material processing. However, the effect of EPP on the biological performance of the treated surfaces remains unclear. In the present study, the effects of EPP on the surface roughness, micro-morphology, corrosion behavior, and cell response of 316LVM were investigated. The results revealed that the surface roughness (Ra) was reduced from 0.3108 to 0.0454 µm upon EPP, and the sharp peaks and protrusions produced as a result of mechanical grinding were removed. The corrosion current density decreased from 1.129 to 0.164 µA/cm2, while the charge transfer resistance increased from 513.3 to 17,430 kΩ·cm2, which implied that EPP treatment could significantly improve the corrosion resistance of 316LVM. Furthermore, affected by the sharp ridges on both sides of the groove, the outward spreading of osteoblasts (MC3T3-E1) on the untreated samples was inhibited, and the edges were curled. The cells grew along the direction of the mechanical processing texture on the untreated samples, while they grew randomly in all directions on the surface treated using EPP, which adversely affected the growth, spreading, and migration of the cells.
A thermoelectric generation model is proposed based on the structure of thermoelectric generator, working conditions, the effect of air heat transfer and contact resistance in thermoelectric components. In addition, the effect of the thermoelectric generator output performance under the condition of different temperature of the cold and heat source, contact resistance between the cold-end and hot-end, the load resistance and the contact resistance is calculated. The results show that the output voltage is linear associate with the temperature difference between hot and cold ends, however, the output power increase along with the increase of temperature of hot-end and decrease of cold-end. The output voltage reaches 5.76 V and the output power reaches 9.81 W when the temperature difference is 200 °C. Assume that the contact resistance is ignored, the output voltage and power reach peak values of 3.61 V and 3.85 W. The output performance of thermoelectric generator decreases with the increase of thermal contact resistance at hot and cold ends, and the reduction is getting lower and lower. With the increase of the load resistance, the output power increases at the beginning and then decreases. The optimal output power is 3.69 W when the contact resistance is 0 Ω and the optimal load resistance is 3.3 Ω. The maximum output power corresponding to neglecting the contact resistance will be reduced by 13.5% when the contact resistance is 0.5 Ω.
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