MODELING, VALIDATION AND OPTIMAL DESIGN OF THE CLAMPING FORCE CONTROL VALVE USED IN CONTINUOUSLY VARIABLE TRANSMISSION

Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.

Prosthetic venous valves for chronic venous insufficiency:Advancements and future design directions

With the serious aging population and lifestyle changes,chronic venous insufficiency accounts for approximately 25.95%of the population,which may lead to lower limb edema and leg heaviness,as well as severe infections of skin ulcers that can result in sepsis and necessitate amputation.Conservative treatment and other supportive measures can only slow the disease's progression but are unable to drastically reverse it;surgical interventions are rarely used due to the high risk of catastrophic postoperative consequences.As one of the most promising minimally invasive therapies,percutaneous prosthetic valve replacement has emerged in light of this situation,providing novel alternatives for patients with deep venous valve insufficiency.We reviewed the historical prosthetic venous valve designs,including their structure and materials,animal evaluation models,and assessment criteria.On the basis of the findings from in vitro tests,animal studies,and clinical trials,we summarized the major challenges and potential solutions for the development of advanced prosthetic venous valves.

Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.