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Squeak and rattle (S&R) are nonstationary annoying and unwanted noises in the car cabin that result in considerable warranty costs for car manufacturers. Introduction of cars with remarkably lower background noises and the recent emphasis on electrification and autonomous driving further stress the need for producing squeak- and rattle-free cars. Automotive manufacturers use several road disturbances for physical evaluation and verification of S&R. The excitation signals collected from these road profiles are also employed in subsystem shaker rigs and virtual simulations that are gradually replacing physical complete vehicle test and verification. Considering the need for a shorter lead time and the introduction of optimisation loops, it is necessary to have efficient and inclusive excitation load cases for robust S&R evaluation.

Increasing demand for simulation accuracy often leads to increased finite element model complexity, which in turn, results in higher computational costs. As a provision, component mode synthesis approaches are employed to approximate the system response by using dynamic substructuring and model reduction techniques in linear systems. However, the use of available model reduction techniques in nonlinear problems containing the contact type of nonlinearities remains an interesting topic. In this paper, the application of a component mode synthesis method in squeak and rattle nonlinear simulation has been investigated. Critical regions for squeak and rattle of the side door model of a passenger car were modelled by nonlinear contact definition in finite element simulation. Craig-Bampton model reduction method was employed to substructure the finite element model while keeping the nonlinear contacts in the model.

The main objective of this study is to investigate the effect of spot-weld modeling approaches on NVH virtual simulation problems. For this purpose, finite element method is considered for further simulations. The goal is to evaluate and compare results within the domain of 0 to 200 Hz by modeling spot-welds with three different element types: a rigid body constraint element (RBE), two rigid body elements with hexahedral solid element (RBE3-HEXA-RBE3) and CWELD constraint. In order to evaluate the effects, three main NVH analyses are chosen for this study. In the first place, a free-free modal analysis is performed for the BIW and trimmed body models of a D-segment saloon car in order to estimate natural frequencies and mode shapes. Afterwards, a frequency response analysis is performed to evaluate the dynamic stiffness of engine mount. Finally, a noise transfer function (NTF) simulation is carried out to calculate the sound pressure level at driver ear's location.

The main purpose of this research is to reduce the transmitted engine vibration to the subframe structure via improving the mobility of engine mountings. In fact, the main focus is on the geometry optimization of the subframe part, implementing the design of experiments method, to increase the dynamic stiffness of the part to reduce the vibration transfer function in the mountings location. In order to perform the optimization process, the front end model of the reference vehicle including the suspension, steering system, engine and deriveline system is generated in FE software. According to the prevalent guidelines, the mobility of engine mountings should be greater than target value which is usually obtained through benchmarking. To do so, some structural parameters that are apt to influence on the mobility function, e.g the section of subframe, thickness of subframe and vehicle body are selected as design variables for doing the design of experiments analysis.

Nowadays, outer surface design of passenger cars is not just a matter of styling and safety but air flow around car body and exterior accessories has significant effect on fuel consumption, performance and dominantly on the wind noise. In recent years, passenger comfort is one of the most challenging and important automotive attributes for car makers. Controlling the turbulence eddies that causes aerodynamic noise can remarkably affect passenger's comfort quality. Identification of aerodynamic sources is considered as the first step in order to control the wind noise. In this research, computational fluid dynamics method is applied to simulate the wind flow around the car and the investigation of aerodynamic noise pattern is performed by numerical method which is the most prevalent way that is used by auto industries.

One of the main safety criteria of a passenger car is the accurate and stable lateral response of suspension system in severe handling manoeuvres. This behaviour can dramatically change as a result of compliances in mountings of suspension system. In other words, alteration in suspension alignment dimensions, as a result of handling forces in a cornering manoeuvre, can change rear axle installation angle and consequently it negatively affects lateral stability and understeering behaviour of car. In this research, this defect is investigated in an available passenger car and behaviour of the system is improved by optimising stiffness and installation angle of bushings of rear axle. It is noteworthy that although stiffening axle bushes can increase lateral stiffness of rear axle it is a matter of trade-off between ride and handling performances of vehicle.

In this research the main focus is on reducing the transmitted engine vibration through exhaust line to the passenger cabin in a light commercial vehicle. The main approach is firstly to locate the mountings of the exhaust system based on the results of the modal analysis. Afterwards, the stiffness of the rubber hangers is optimised to minimize the measured vibration in the driver seat rail position. The optimisation approaches are executed considering the design of experiments method. To achieve this, the partial BIW model of the reference vehicle and the powertrain system is generated in FE software. The FE model of the exhaust system is validated by experimental results. In order to define the optimum stiffness for the exhaust rubber hangers, design of experiments method is used. The main candidate parameters for DOE analysis are exhaust rubber hangers in the front floor region in addition to the exhaust flexible joint stiffness.

The main purpose of this research is to tune the stiffness of engine mounts of a passenger car in order to reduce the transmitted vibration to driver with regard to the permissible values of natural frequencies of engine using DOE method. Based on the previous experiments, prevalent criteria are introduced by automakers which would lead the designer to optimum values of mountings' stiffness. In this paper we benefit the usage of experimental frequency bands introduced by the NVH authoritative references. To achieve this, we use a mixed Finite element and multi body dynamic modeling. The FEM model of the body front end and engine subframe is developed using Hypermesh. The engine block is modeled as a rigid body attached to the neighbor parts with rubber mounts. The modal natural file of the whole system is created by the aim of MSC/Nastran and exported to the ADAMS/View for further analysis.

The aim of this research is the modification of frequency response of transmitted vibration to vehicle body via alternating the geometry of vehicle structural components. For this purpose after transmitting the FE model of vehicle body into ADAMS software and building full vehicle model, mode shapes, natural frequencies and transmitted vibration to the vehicle cabin in sensitive points were obtained. It has been shown that changing the engine ram geometry and adding strengthening components, not only affect the natural frequencies of vehicle body but also could modify the natural frequencies of full vehicle model. The result of using random road input demonstrates that the amplitude of the vibration transmitted to the vehicle cabin in modified model is decreased.