Investigation On Residual Contact Pressure Of Assembled Camshaft Under Hydraulic Expansion

The assembly camshaft utilizes flexible design of parts and combined assembly method,which is manufactured separately for the different performance requirements of components such as shaft,cams,and journals,so it is more fully leverage the properties of materials.Compared with the traditional integrated camshaft,this kind of camshaft has obvious advantages,mainly in the reduction of production resources,the lightweight of the engine and the improvement of engine performance,and it is an advanced technology with great development potential.The Tube hydroforming,as a mature connection technology,which can be applied to assemble the camshaft tightly.During the connecting procedure,the outer wall of the shaft and the inner wall of the cam are contacted with each other.The contact pressure between the shaft and cams is an important indicator for the strength of the assembled camshaft.Therefore,it is necessary to conduct researches on the residual contact pressure of the hydraulically-expanded assembled camshaft.In this paper,based on reasonable hydraulic parameters(hydraulic pressure and axial feed),an assembled camshaft with isometric-trilateral sectional profiles assembled camshafts is researched by two methods: Experimental research and Numerical Analysis.Firstly,based on the hydraulic parameters,the hydraulic connection test was carried out between the shaft and the cam.Secondly,the contact area data of the shaft and the cam were outputted and calculated,and the influence of hydraulic parameters on the contact area was analyzed by the theory of plasticity.Thirdly,the displacement of the shaft was outputted and calculated,and the influence of the hydraulic pressure parameters on its elastic recovery was analyzed.The contact pressure on the surface of the shaft bulging area was processed,and the influence of hydraulic parameters on the contact pressure was comprehensively analyzed based on the basic principles of plastic mechanics and curve fitting method.Finally,the correlation analysis method of mathematical statistics was used to comprehensively analyze and obtain the relationship among the residual contact pressure and the residual contact area and the elastic recovery amount.The research results show that:(1)The elastic recovery of the shaft decreases nearly linearly with the increases of hydraulic parameters,which means that the increases of elastic recovery can be obtained based on the increases of hydraulic pressure and the axial feed.The amount of reduction is about 5% difference between the experimental and simulation results.The increase of hydraulic parameters can reduce the elastic recovery of camshaft and improve the contact reliability of camshaft.(2)The contact area of the camshaft increases almost linearly with the increases of the hydraulic parameters,which means that according to the increases of the internal pressure and the axial feed,the increases in the residual contact area is known.The residual contact area of the camshaft under axial compression is generally larger than that of free expansion.(3)The residual contact pressure of the camshaft increases almost linearly with the increases of the hydraulic parameters,that is to say,according to the ratio of the increase in the pressure and the axial feed of the hydraulic expansion equipment,the increase of the residual contact pressure of the mandrel can be known.The difference between experiment and simulation is about 6%.The overall residual contact pressure at both ends of the camshaft bulging area is greater than the middle contact pressure,indicating that the two ends of the camshaft are in close contact.(4)The circumferential residual contact pressure of the shaft reaches the maximum value at the characteristic point b.While the residual contact pressure presents a wave like distribution along the axial direction,the maximum value is basically between 12-15 mm from the starting point B` and point b,where the connection quality is good.The contact pressure between 5-8mm from the starting point b is very small,which indicates that the connection quality is poor.(5)The larger the residual contact pressure,the larger the residual contact area will be.The elastic recovery is getting smaller with the residual contact pressure is getting larger.