A high-accuracy and generally applicable method of predicting the frequency response functions of engine structures up to the radiated noise range has been developed.Because the joints between engine parts possess nonlinear properties, as exemplified by the head gasket, analytic models that are linearized in relation to the state of the joints are essential in conducting frequency response analyses. The analysis discussed in this paper was divided into two stages. In the first stage, pressure data for the joint sections was obtained by means of nonlinear contact analyses. In the frequency response analyses conducted in the second stage, accuracy was increased by defining the stiffness and damping of the joint sections as linear properties based on the pressure data, and formulating vibration analysis models that considered strain due to bolt axial force.Some properties of the joint sections cannot be determined in materials tests, and pressure conversion tables assumed to express properties dependent on pressure were therefore defined. Uncertain values were identified on the basis of test results for the base engine. The application of this method to another engine demonstrated that the frequency response analysis achieved a level of accuracy that represented no impediment to practical use, and indicated that the method possessed general applicability for frequency response analyses of engine structures.
Article of Honda R&D Technical Review Vol.23 No.1 (116 - 124)