In order to determine the stiffness distribution of a piston

a matrix was used to describe the piston radial stiffness

and a bench test was made to measure the piston deformations at specified points when loading was made at different positions. The effect of stiffness change on the secondary motion

kinetic energy in knocking and friction loss was analyzed by simulation. In order to ensure the accuracy of boundary conditions such as piston temperature field

thermal piston deformation and installed liner deformation

the simulation process was calibrated and validated by the measured data obtained with the hardness plug temperature test and liner profiler. The results show that a dynamic analysis must include the influence of liner stiffness and piston stiffness

otherwise the piston tilting angle from the simulation will be smaller and the friction loss will be larger than their actual values

and the kinetic energy in knocking will generate cyclical deviations at different crank angles

some deviations may even reach 70%; that the piston stiffness will change with the structure

and usually if the stiffness of skirt is increased

the maximum tilting angle at each turning point will become smaller and so will be the peak kinetic energy at each knocking point.