【作者】 肖伟；

【导师】 胡德安； 伍乾坤；

【作者基本信息】 湖南大学 ， 机械工程（专业学位）， 2019， 硕士

【摘要】 结构体的碰撞是工业噪声产生的主要原因之一,并且由于碰撞噪声具有极高的瞬态声压峰值,对周围的设备和人群都会产生不良影响。而在实际工程应用中,结构之间由于碰撞产生的噪声常常无可避免。要想对碰撞噪声进行有效的控制,首先需要了解结构体碰撞噪声的产生机理及辐射规律。本文基于实验和数值仿真的方法,对结构体碰撞噪声的产生及辐射规律展开了研究。并且针对影响结构体碰撞噪声辐射的有关因素进行了数值研究。首先,文章对结构体碰撞噪声辐射问题中涉及到的相关理论进行了简要介绍,主要包含接触碰撞动力学和声波辐射基本理论。在接触碰撞动力学理论中阐述了动力学的三大控制方程(平衡微分方程、几何方程和物理方程)和不同边值问题对应的边界条件,并根据动力学的控制方程和边界条件再次推导了接触碰撞问题中数值解法的控制方程。对于噪声辐射理论,主要介绍了声波的三大基本方程、声学波动方程的推导以及声学边界条件,其中三大基本方程分别为声波连续方程、声波运动方程和声波状态方程。然后,以弹性球的碰撞噪声辐射作为一个典型案例来探讨结构体碰撞噪声辐射的产生机理和辐射规律。利用动力学软件LS-DYNA和声学软件LMS Virtual Lab.分别模拟了弹性球的碰撞过程和噪声辐射过程,并得到了弹性球碰撞的动力学响应结果和瞬态噪声辐射声场。通过分析数值结果,发现球体的刚体加速度是噪声产生的主要原因。此外,为了验证弹性球碰撞噪声辐射数值模型的有效性,设计并搭建实验平台,对弹性球碰撞噪声辐射展开了实验研究。通过实验研究获得了碰撞噪声辐射声场不同位置处的声压时间曲线,将声压曲线与数值模型中对应位置处的声压曲线进行比较发现二者基本吻合,从而验证了数值模型的有效性。接着,基于弹性球碰撞噪声辐射的数值模型分别研究了主动球初始碰撞速度、被动球初始间隙以及被动球数目对球体碰撞噪声辐射的影响。此外,为了获得各影响因素的对弹性球碰撞噪声的影响大小,本文结合正交试验设计方法对各影响因素进行了敏感性分析。通过对结果进行处理与分析发现,初始碰撞速度对球体碰撞噪声的影响最大,且辐射声场的声压幅值与初始碰撞速度成正比;而被动球之间的初始间隙对球体碰撞噪声的影响最小。最后,文章基于碰撞噪声辐射问题的研究方法,展开了轿车关门碰撞噪声辐射的研究。结合动力学软件LS-DYNA和声学软件LMS Virtual Lab.建立了关门碰撞噪声辐射的数值模型,重现了关门碰撞噪声的产生及辐射过程。并利用关门碰撞噪声辐射的数值模型,分别研究了车门关闭速度、车门密封胶条材料和车门外板材料对关门碰撞噪声的影响。数值结果表明了轿车关门碰撞噪声对车门关闭速度和密封胶条的材料比较敏感,而汽车外板材料对汽车关门碰撞噪声几乎没有影响。更多还原

【Abstract】 Collision among structures is a major source of noise in industry.Because of the high acoustic pressure amplitude of collision noise,it has negative effects on the equipments and crowds within the area of noise radiation.And the collision noise generated by the colliding structures is inevitable in practical engineering applications.In order to find an effective approach for colliding noise control,it is first necessary to understand the mechanisms of noise generation and the characteristics of noise radiation.In this paper,the method combines the experiment and numerical simulation to research the production mechanisms and radiation characteristics of collision noise.And the factors that influence the collision noise radiation are also investigated numerically.Firstly,the correlation theories which involved in the collision noise radiation of structures are briefly introduced in this paper.Those mainly include the basic theories of elastic dynamics and acoustic radiation.In elastodynamic theories,three governing equations(equilibrium differential equation,geometric equation and physical equation)and boundary conditions corresponding to different problems are described respectively.And the governing equations of numerical method for the contact collision problem are derived again according to the governing equations and boundary conditions of dynamics.As for noise radiation theories,three basic equations in acoustic,derivation of acoustic wave equations and acoustic boundary conditions are introduced.Three basic equations in acoustic are continuity equation,motion equation and state equation.Secondly,the collision noise radiation of elastic spheres is taken as a typical case to investigate production mechanisms and radiation characteristics of noise radiated by the structures collision.A numerical simulation scheme combining the dynamic solver of LS-DYNA and acoustic solver of LMS Virtual Lab.is implemented to reproduce the sound field generated by the collision of spheres.By analyzing the numerical results,it is found that the rigid body acceleration of spheres is the main cause of collision noise.In order to verify the numerical model of noise radiation,an experimental platform is designed and built to investigate the noise radiation of spheres collision.Ultimately,the sound pressure in radiation field is obtained from the experimental data sets.Comparing the experimental results with numerical results,it can be confirmed that the numerical model can effectively capture the noise radiation of spheres elastic collision.Thirdly,basing on this numerical model of noise radiation for spheres collision,the influence of different factors,including the initial velocity of impactor,the initial gap and the number of impactees,on the collision noise radiation of multiple spheres is studied.In addition,the orthogonal experimental method is used to do sensibility analysis on influencing factors,and the sensibility order of influencing factors is obtained from sensitivity analysis results.By processing and analyzing the results,it can be found that the initial velocity has the greatest influence on the collision noise of the spheres,and the sound pressure amplitude of the radiated sound field is proportional to the velocity.While the initial gap between passive spheres has a minimal impact on the collision noise of spheres.Finally,the research on noise radiation induced by door-slamming collision of a car is carried out based on the research method of collision noise radiation.A numerical model of door-slamming noise radiation is constructed with the explicit nonlinear LS-DYNA3 D and the acoustic module in LMS Virtual Lab.,and the sound field is reproduced by solving the numerical model.On the basis of numerical model,the influence of different factors,such as the door-slamming speed,the material of vehicle door seal and vehicle outer door panel,on the collision noise radiation is discussed respectively.The numerical results show that collision noise radiation is sensitive to the door-slamming speed and the material of vehicle door seal,while the material of vehicle outer door panel has less effect on it.更多还原