Research On The Coupling Characteristics Of The Closed Irregular Sound Field Of Stiffened Plate Structure

With the improvement of people's living standards,both the civil field and the field of construction machinery have put forward higher and higher requirements for low noise.In engineering,thin plate structure is widely used in mechanical equipment,among which rectangular plate is a typical structure.Because these thin plate structures are easy to vibrate under internal and external excitation,the method of adding stiffeners to the thin plate can improve the strength and stiffness of the plate and achieve the purpose of lightweight design.For example:cars,ships,airplanes,train cars,etc.These structures are generally made of stiffener plate structures,which are in the fluid medium(such as air,water,oil,etc.),when the machine is running or driving,it vibrates under the internal and external excitation and radiates noise to its internal and external coupled with the sound field.Therefore,the acoustic vibration coupling analysis and noise control of the stiffened plate and the irregular closed cavity have always been the research focus at home and abroad.It is of great theoretical and practical significance to study the characteristics of sound field and the law of sound solid coupling in the stiffened plate and irregular closed cavity,so as to control the noise in the cavity.The main content and innovations of the thesis are as follows:(1)Firstly,the free vibration characteristics of the cavity are studied when the shape of the cavity changes from a regular rectangle to a complex cavity with multiple inclined walls.The results show that the free vibration characteristics of irregular cavity modes depend on three factors:the position of inclined wall,the number of cavity modes and the number of cavity modes.At the same time,the results of the analytical method are compared with those of the finite element method to verify the correctness of the theoretical model.(2)In this chapter,based on the modal superposition method,the free vibration characteristics of stiffened plates under two kinds of constraints(fixed support constraint and simple support constraint)are studied,and the influence of the number and placement position of stiffeners on the free vibration characteristics of stiffened plates is analyzed.The results show that the free vibration characteristics of stiffened plates are affected by the number and distribution of stiffeners and the support mode of stiffened plates.Under the same constraint conditions,the lower the natural frequency of stiffened plate is,and the more obvious the modal shape changes,as the position of the stiffened plate is close to the middle of the plate.(3)The free vibration characteristics and the dynamic response under point force excitation of the coupling system of trapezoid cavity and stiffened plate structure are calculated.The results show that the distance from point force to reinforcement is closely related to the dynamic response of the coupling system.