Application Of Modal Analysis On Powertrain Development

The powertrain as the heart of the vehicle is the most important source of noise and vibration, so it will directly affect the NVH performance of the vehicle, the production licence of the company, the competition ability of production in the market. Now,NVH control has became the urgent affairs because of more and more strict vehicle noise regulation.Modal analysis which is consisted of test modal analysis and computational modal analysis is a kind of technology to research and evaluation the parameters needed by systemic dynamic characteristic. The finally aim of modal analysis is to identify modal parameters of system, and to offer the basis to vibration characteristic analysis of structure system, to diagnose and predict of vibration fault, optimize the design of dynamic characteristics of structure system. Modal analysis application is concluded as following:(1) Evaluating the dynamic characteristic of present structure(2)Estimating and optimizing the design of the dynamic characteristic of new structure(3) Diagnosis and prediction of vibration fault(4) Controlling the radiation noise of structure(5) Identifying the load of structure system(6)Refining the vehicleThe following works were done by using modal analysis technology:1.The test modal analysis of parts and assemblies of powertrain Inherence characteristic parameters of parts and assemblies of sample engine designed by self-determination were acquired by test modal analysis of oil pan, crankshaft-flywheel- torsion absorber system, engine block, cylinder head , timing belt cover, rocker cover& cylinder sleeve etc. The same test modal analysis was done to the parts and assemblies of criterion sample engine. The disadvantages of self-determination designing engine were discovered by contrast. Optimizing design was carried out combining with CAE. Nicer effect was acquired by model validating of test modal analysis of oil pan and engine block versus counting modal analysis. Total noise level drops 0.5dB after the optimizing design of oil pan. The noise test was taken in total anechoic chamber.Modal aracteristic parameters of parts and assemblies of engines can be acquired accurately by test mode analysis. Some parameters contrasted and analyzed can be offered to engines design departments to help them to optimize design the structure of the engines contrast and analysis. Problems such as the high radiation noise level of rocket cover and oil pan, at the same time, test modal analysis offers basis to finite units accounting models. Above-mentioned things shorten the period of the research and development of sample engine.2 .Powertrain modal test.Powertrain mountings as vibration isolation component are important to drop interior noise of vehicles and advance car ride comfort .Powertrain rigid mode analysis is an important means to match the mountings. Powertrain mountings as main components of vibration transfer path are very an important teach for vehicles vibration isolation and sound isolation. The stand or fall of present mountings was known by rigid mode test. The matching mountings combining dynamic emulation account need vibration isolation and acquire pure modes, mountings systems appeasing support and limiting to some position as well.We took engine, clutch & gear box as a whole to do powertrain flexibility modal test to examine the connecting stiffness of engine and clutch shell, fly-wheel shell and gear box. If the connecting stiffness is over low, parts will be damaged easily due to drastic vibration. The test means is applied because of its easiness. Using the test means, I found that the first uprightness bend mode and the first level bend mode of some power train is very low . Imaginable bad result was avoided because design components amended the thin position.4.Computational worksIt is of importance to optimize design the parts and assembles of powertrain using HyperMesh software to compute these three-dimensions models. For instance, oil pan ,twi-optimized and computing, has almost the same inherence characteristic as the example. The engine stand tests indicated that the surface radical noise of oil pan becomes low certain degree, optimize designing obtained a good affect., besides, experiences are piled up for following R&D of new kinds of engine.For cylinder block, by CAE analysis the task brings forward adding reinforcing rib on the cylinder block skirt and thicken it to advance intensity of the cylinder block, which optimizes the characteristic of structure and sound,yet the total structure hardly changed. For power train mountings system, dynamic simulation was carried out using the ADAMS. At first, analyzed model was based, then the model quality parameters ( the position of center of mass, quality &moment of inertia), kinematics parameters(geometry orientation),dynamic characteristic parameters( intensity, damp etc. )&environment parameters(road surface spectrum, wind level)were obtained. After contrast between count and test result ,I found that vibration isolation of the power train mountings is very poor, as well as the modes mixed. Therefore ,further optimizing design is needed combining test result.Because time is limited, mode synthesized test of cylinder block, cylinder head cover &oil pan wasn't done. In the near future, the works will be done.In a word, using modal analysis technology good effects were obtained during research and development of vibration and noise of evaluating and controlling of powertrain to optimize design.