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Large static strain appears on the fillet on upper deck of diesel engine
cylinder block by tightening force of cylinder head bolts. Reducing static strain is
necessary to avoid the crack initiation on the fillet. The static strain along the fillet
can be reduced, for example, by modifying the depth of thread engagement, and
modifying the bead shape and position into the bore grommet of cylinder head
gasket. In the present study, the depth of thread engagement was optimized
considering four conditions, the overall magnitude of strain, the circumferential
fluctuation of strain, the change rate of strain against the depth of thread
engagement, and the length of cylinder head bolt. The bead shape or position was
optimized considering two conditions, the overall magnitude of strain, and the
distribution of contact pressure on the contact area with the cylinder block and the
cylinder liner. The analysis results of the circumferential distribution of static
strain were agreed with the measurement results. The optimum depth of thread
engagement of cylinder head bolt and the optimum type of the cylinder head
gasket were evaluated using FEM.