An integrated computer-aided engineering approach for engine cylinder block analysis using HEXA8 finite elements

Analytical and experimental investigations of a diesel engine cylinder block have been performed. The engine block modeled was a Daewoo D0846HM. This is a six cylinder in-line engine of M.A.N. type design. Traditionally, an engine block has been modeled using either 8-node(HEXA8) or 20-node solid(HEXA20) elements for stress and thermal analyses and modeled using 4-node plate and shell elements for dynamic analysis. As computer analysis increases, it is desirable for the engine industry to reduce analysis costs in the process of designing an engine and to integrate various analysis procedures. To reduce the time and the cost for analysis and simulation, a finite element modeling technique using only 8 node solid elements for both dynamic and static analyses is presented. Based on this integrated modeling technique, eigenvalues are calculated and compared the experimental data obtained from modal testing of the cylinder block.; For problems, in which out-of-plane motion is of prime importance, like cylinder block vibration, HEXA8 elements have not provided an accurate solution to the eigenvalue problem due to their over-estimation of bending stiffness. To improve the computational efficiency as well as accuracy for bending dominated problems, the newly developed directional reduced integration (DRI) technique with hourglass control was extended to dynamic problems and used to formulate the stiffness matrices. Results using this new formulation are compared with results obtained using traditional beam and plate elements.; From eigenvalue analysis of the block, the lowest two natural frequencies predicted were found to be 211.9Hz, and 484.2Hz. The analytical results using HEXA8 finite elements formulated with the DRI technique provided fairly close correlations with the experimental measurements using modal testing, in which the natural frequencies were measured to be 199.67Hz and 430.0Hz, respectively. Using the finite element model, dynamic characteristics of the cylinder block are further evaluated based on computational results obtained up to the 11th. mode. The computational results show the vibration modes, which are related to the vibration and noise transmission characteristics of the engine block.; Additionally, in order to minimize some unacceptable errors in the finite element solution, an adaptive method including a mesh refinement technique in conjunction with a space index mesh generation was introduced for vibration problems. For minimizing the error in the time frame, a cost effective variable time stepping algorithm was introduced based on local truncation error control, when the direct time integration method was used to solve forced response problems.