This paper on "FEA of a Cylinder Liner-Engine Block Interface in a Spark Ignition Engine" was presented at the NAFEMS World Congress on Effective Engineering Analysis - 25-28 April 1999, Newport, Rhode Island, USA.

Abstract

Casting voids at the interface of a cast iron combustion cylinder liner and an aluminium alloy engine block may locally constrict heat flow and cause the bore wall to distort. This thermal distortion will compromise the ability of the piston rings to form an effective seal. [14] This paper investigates the thermal and structural effect of casting voids as a function of several significant parameters. The parameters studied include: mechanical and thermal material properties of the cast iron cylinder liner and aluminium alloy engine block, boundary and initial conditions of the assembly, and parameters that describe the macroscopic geometry of the casting voids and the surface roughness at the liner-block interface.
The solution was obtained using a two dimensional thermal-structural cross-section of the liner-block assembly. Plane stress and plane strain assumptions were used to bound the actual values of bore wall displacement and temperature. The conductance assigned to the liner-block interface was an empirical function based on the normal contact pressure and hardness of the materials. The thermal boundary condition for the bore wall during operation was simplified to a constant temperature (Dirichlet) boundary because the penetration depth of the bore wall temperature swing was less than the thickness of the liner and, therefore, did not affect the conductance.
The bore wall temperature and displacement are presented as functions of the bore circumference and selected parameters shown to have an effect. Results show that the parameter most significantly affecting the inner bore wall displacement is the initial temperature of the liner. The initial temperature of the liner leverages the effect of the thermal expansion coefficient, α. Several other parameters were also shown to have an effect on bore wall temperature or displacement. They are listed in order of magnitude of effect: the thermal expansion coefficient; elastic modulus; and thermal conductivity of both materials. The average asperity slope, tanδ, was shown not to have a significant effect within the range of typical sand cast surfaces.
For the range of parameters studied, casting voids are shown not to significantly increase liner temperature or distort the bore wall. Only in extreme cases, including much larger casting void size, are they shown to significantly increase liner temperature and distort the bore wall.