Research On Integrated Design Of Structure And Materials Based On Low Frequency Vibration Problems

In recent years,with the development of automobile technology,the performance of automobile has been continuously improved.People's requirements of ride comfort are increasingly high.On one hand,the problem of vehicle vibration and noise has become one of the important indicators of vehicle ride comfort.It has been paid more and more attention by consumers and major automobile manufacturers.On the other hand,with the increasingly serious environmental and resource problems and the application of new technology,lightweight technology and new material technology have been widely used in automobiles.As an important part of vehicle lightweight design,body lightweight will lead to significant changes in structural dynamic characteristics,especially the mismatch between the vehicle stiffness and the local stiffness.If the structural balance of vehicle is broken,it will bring about some problems,such as the stiffness and strength of vehicle structure,collision safety,particularly vibration and noise problems.Low-frequency vibration and noise problems are difficult to solve due to its wavelength characteristics.Therefore,it is of great significance to solve the problem of low-frequency vibration and noise.At the same time,as a new type of periodic composite acoustic material,phononic crystals(PCs)have the characteristics of inhibiting elastic wave propagation in the bandgap range.The sub-wavelength characteristics of locally resonant phononic crystals provide a new idea for integrated optimization of composite materials for low-frequency vibration and noise reduction.Based on the actual vibration and noise problems of a car,a set of methods and processes of building refined CAE models and problem representation matching the test results were established at first.The idea of optimization based on the balance of structure was put forward.Then,using the methods of sensitivity and modal strain energy,the areas with low local stiffness were accurately positioned,which caused the excessive vehicle vibration and interior noise.Secondly,structural optimization method was used to improve the stiffness of local weak areas.And the accuracy of vibration source location was verified both indirectly and directly.Finally,the integrated optimization of structure and material of 3D PCs was used to greatly reduce the vibration peak amplitude of problem frequency.And the bandgap was modulated to low frequency band to suppress or propagation of low-frequency acoustic waves,and further reduce the vibration amplitude.The solution of practical problems proved that this integration optimization method had a good effect on passenger vehicles.The maximum reduction of vibration amplitude was up to 30%,especially in the low frequency where the noise reduction which is very difficult below 200 Hz.It has not only reduced vibration amplitude,but also satisfied its mechanical performance requirements,laying the foundation for further vehicle design improvements.By looking for the specific location that played a decisive role in the performance of low frequency vibration and noise of structures,the steps and methods of precise simulation and optimization have been summarized.It has not only achieved the purpose of reducing vibration and noise,but also met the mechanical properties requirements of its application in automobiles,laying the foundation for further design improvement of automobile body.