Stochastic transfer operator methods for modelling the vibroacoustic properties of newly emerging transport structures

在过去的50年里，计算能力的快速增长已经产生了一个完整的仿真行业，服务于制造商的需求，他们希望以最佳的方式设计产品，而不需要花费时间和成本来构建一系列物理原型。作为计算机辅助工程（CAE）的一部分，设计和施工决策越来越多地通过虚拟原型来进行，并且在所有工程领域都寻求有效的仿真工具。在许多机械系统的设计中，噪声和振动是特别重要的性能方面。高噪音和振动水平会对结构和使用者造成损害（例如，可能导致听力损失）。开发计算技术来提高我们对复杂建筑结构的振动和声学的理解，可以提高性能，加快设计周期，最终产生更安全，更少噪音的产品。长期以来，人们一直在寻找方法来模拟大型复杂结构，如飞机、火车和汽车。这些结构的巨大尺寸使得建造全尺寸的物理原型非常昂贵，而且通常是不可行的。这也给模拟方法带来了问题，并限制了许多CAE产品的低频，其中计算运行时间相对较低，不确定性对振动行为的影响很小。在制造过程中产生的不确定性（例如，在材料特性或物理尺寸上）可能导致高频结构的噪音和振动水平的巨大变化，因此机械工程师转向统计学方法来代替预测这些噪音和振动水平的平均值。不幸的是，这些统计方法是基于一组难以控制的假设，通常只适用于更传统的结构设计。它们不满足于今天使用的大型弯曲和模塑部件。因此，目前用于模拟中高频噪声和振动的CAE工具不能满足运输行业工程师的需要。由于2008年英国的气候变化法案和全球类似的倡议，运输行业正在经历一个巨大的变化时期。替代燃料来源和轻质材料是两个主要的发展领域。市场上出现了越来越多的混合动力和电动汽车，整个行业对轻质和复合材料的使用也在增加。工程师们已经需要新的、更通用的中高频模拟方法，但轻量化材料和电源的日益普及使这种情况更加复杂，主要有三个原因：-仅对新制造的轻量化和复合材料的材料特性进行估计，这给模型带来了相当大的不确定性；-轻质和复合材料通常比传统的钢或铝基结构发出更高频率的噪音；-噪音和振动的来源(例如：电动机，空气阻力等)将主要在高频。在本提案中，将开发随机（或随机）传递算子方法来模拟大型复杂结构中的中高频结构振动。这些方法在能够模拟结构设计和材料中的不确定性方面具有当前统计方法的优势，但至关重要的是，这些方法将适用于更广泛的结构，包括大型模塑部件和新型轻质材料。因此，即将开发的方法有可能为寻求开发下一代绿色轻型运输结构的机械工程师提供一个黑盒设计工具。

The rapid growth of computing power during the last 50 years has given rise to a whole simulation industry serving the needs of the manufacturers looking to design products in an optimal manner, without the time and costs associated with building a series of physical prototypes. Design and construction decisions are increasingly made by means of virtual prototyping as part of Computer Aided Engineering (CAE), and efficient simulation tools in all areas of engineering are sought after. Noise and vibration are particularly important performance aspects in the design of many mechanical systems. High noise and vibration levels can be damaging to structures and to their users (potentially causing hearing loss, for example). Developing computational techniques to improve our understanding of the vibration and acoustics of complex built-up structures can enhance performance, speed up the design cycle and ultimately result in safer and less noisy products.Methodologies have long been sought after for modelling large-scale complex structures such as aircraft, trains and cars. The sheer size of these structures makes building full-scale physical prototypes expensive, and often infeasible. It also poses problems for simulation methods and limits many CAE products to low frequencies, where computational run times are relatively low and uncertainties have little influence on the vibrational behaviour. Uncertainties arising during the manufacturing process (for example, in material properties or physical dimensions) can lead to large variations in the levels of noise and vibration of a structure at high frequencies, and so mechanical engineers have turned to statistical methods to instead predict averages of these noise and vibration levels. Unfortunately, these statistical methods are based on a set of assumptions that are hard to control and generally only fulfilled for more traditional structural designs. They are not fulfilled for the large curved and moulded components used today. Therefore the CAE tools available at present for simulating mid- and high- frequency noise and vibration do not meet the needs of engineers in the transport sector. As a result of the 2008 climate change act in the UK and similar initiatives around the globe, transport industries are undergoing a period of great change. Alternative fuel sources and lightweight materials are two of the major areas of development. An increasing number of hybrid and electric powered vehicles are appearing on the market and the use of lightweight and composite materials is increasing across the sector. Engineers were already in need of new and more versatile simulation methods at mid-to-high frequencies, but the increasing popularity of lightweight materials and electric power sources has compounded this situation for three main reasons:- only estimates of the material properties for newly manufactured lightweight and composite materials are available introducing considerable uncertainty into the model;- lightweight and composite materials typically emit noise at higher frequencies than more traditional steel or aluminium based structures;- sources of noise and vibration (eg. electric motors, air resistance etc.) will mostly be at high frequencies.In this proposal, random (or stochastic) transfer operator methods will be developed for modelling mid-to-high frequency structural vibrations in large complex structures. These methods will have the advantages of the current statistical approaches in terms of being able to model uncertainties in the structural design and materials, but crucially will be applicable to a far wider range of structures, including large moulded components and novel lightweight materials. The approach to be developed therefore has the potential to provide a black-box design tool for mechanical engineers looking to develop the next generation of green and lightweight transport structures.