The Modal Test And Finite Element Analysis Of QC485 Engine Block

The engine block is one of the most important components.The structure and force are relatively complex.Its angular rigidity and strength is the precondition of normal work,Reveals the relation between the outside exciting force and the inherent characteristic,the working condition and the distortion of the engine block by using modal test and finite element analysis.It's very significative for improving the Strength of the engine structureThe modal test technique and the Finite Element Method are synthetically used to analyze the dynamic characteristics of the cylinder block of 485 diesel engine.By frequency domain modal parameters identification way,the modal test is performed on the engine block,arranging 641-test points on the cylinder block and establishing the modal model.By using dynamic signal analyzer,we can gain the transfer function from 0-2000Hz, inherent modal parameters containing twelve ranks are obtained by using the software of STAR.The analysis and calculate of the dynamic response is performed,we can gain the real distortion of the engine block on the working condition.According to the calculation of the freely modal and constrain modal for the 485 engine block.The mode shape is mainly the curving,torsional of the whole and the local modal of the main spindle bearing and crankcase.The inherent relation between the constraints and the natural parameters of the cylinder block is analyzed.Because of the constraint, the free degree is decreased,the angular rigidity is increase,the frequency is bigger than the freely way.Through the calculate of the dynamic response,when the third cylinder works,the biggest distortion of the cylinder is the third on the top of the cylinder,also the distortion is decreased from up and down,the cylinder's distortion is relatively small,the mainly bearing's distortion is bigger.on this foundation,bring foreword some improved schemes,bring forward the scheme of appending trapezoid frame on the bottom of the engine,the frequency increases which increase the angular rigidity of the engine,comparatively distortion is decreased.The modal test is done of the improved and the improved with the cylinder head.