Design And Experimental Research Of Loading System In High And Low Temperature Environment

With the development of the automobile industry and the improvement of manufacturing technology,people have higher and higher requirements for the comprehensive capabilities of automobile engines.As the most important power mechanism in a car,the engine bears more pressure.The engine is the most important power mechanism of a car.In order to meet the requirements of higher speed,faster and more stable,the engine speed is constantly increasing.The increase in speed brings unprecedented challenges and tests to the engine pistons.The working environment of the engine piston is very harsh,and it has been subjected to the coupling effect of high temperature and mechanical cyclic load during work.In addition,when the piston is not working,the external environment will also have a greater impact on it.Especially in cold winters,parking for a long time will make the piston stay in a low temperature environment for a long time.The mechanical properties of piston materials in high and low temperature environments directly affect the reliability and safety of the engine.Therefore,how to construct a high and low temperature service environment close to the service conditions of piston materials and to study and obtain its mechanical properties has important scientific significance and application value.In order to reconstruct the service conditions of the piston material,a high and low temperature loading system was designed and developed in this paper.Completed the system cavity structure design from the shell,heating unit,refrigeration unit,etc.,combined with thermodynamic theoretical calculations and Ansys Workbench temperature field simulation analysis,optimized and improved the high and low temperature environment cavity structure;studied the temperature control of the environment cavity Strategy,designed and realized the temperature closed-loop control of the high and low temperature environment cavity,completed the functional verification and calibration of the entire system,realized the temperature loading of-55℃～1100℃,and the temperature control accuracy reached ±5℃.In order to study the changes of the mechanical properties of piston materials in high and low temperature environments,this paper selects the typical piston material ZL109 silicon-aluminum alloy as the research object,and obtains its tensile and fatigue properties at high and low temperatures.Combined with the observation of the fracture by scanning electron microscopy,it is found that the fracture of ZL109 under high temperature tension is mainly ductile fracture.As the temperature rises,the tensile strength of ZL109 gradually decreases,and the elongation first increases and then decreases;under low temperature conditions,the ZL109 fracture The fracture is mainly quasi-cleavage fracture.As the temperature decreases,the tensile strength of ZL109 increases and the elongation decreases;the fatigue fracture mechanism of ZL109 under the action of high and low temperature-fatigue changes from quasi-cleavage fracture to micro-hole aggregation Fracture transformation,the overall trend of fatigue strength decreases with increasing temperature.