Numerical Analyses On Thermal Ehl Problems Under Sudden Stop And Reciprocationg Motion

Basing on the thermal elastohydrodynamic lubrication(EHL)theory,this thesis uses numerical methods to study the thermal EHL problems under sudden stop and reciprocating motion conditions for the bush-pin chain in the industrial chain.The work includes:(1)A mathematical model for an infinite-line contact thermal EHL problem under the zero entrainment condition is established to study the variation of the oil film under a sudden stop motion.The influence of the initial zero-entrainment velocitiy and suddenstop time on the film thickness,pressure,temperature rise and friction coefficient of the oil film in the contact area is also studied.It is found that,the sudden stop under the zero entrainment condition can cause a sharp increase of pressure at the central of contact area,so the plastic deformation is easy to happen on the surface of solids,causing surface damage.(2)A mathematical model for a point contact thermal EHL under reciprocating motion is built to investigate the variations of pressure,film thickness,temperature rise and friction coefficient.The effects of the stroke length,working frequency,equivalent radius of curvature,load and elliptical ratio on the tribological characteristics of the oil film are studied,respectively.It is found that at the end of the stroke,the oil film is dominated by the squeezing effect.And during the stroke,the squeeze effect and the wedge effect work on the oil film together.On this basis,some optical interferometric experiments were carried out and the results agree well with the results by the numerical simulation.(3)The effect of surface waviness on the point contact thermal EHL under reciprocating motion is explored numerically.Compared with the oil film distribution in smooth surface under the same working condition,this chapter reveals the influence of the wavelength and amplitude of the surface waviness on the thickness,pressure,temperature rise and friction coefficient,and the effect of equivalent radius of curvature on the oil film variation with same surface waviness.(4)A thermal EHL model for a finite-line contact problem of the contact between the bush-pin of a bush chain is established.Using numerical analysis,the variation of the oil film in the contact area at a sudden-stop is investigated.The influences of initial surface velocity and sudden-stop time on the oil film are studied.It is found that the sudden stop can cause the increase of center pressure and the decrease of center film thickness.Friction coefficient and thermal rise also increase during this process.At the edges of the finite-line contact area,the pressure and temperature rise are increased significantly.