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The main end of this research is the optimization of engine sub-frame parameters in a passenger car to reduce the transmitted vibration to vehicle cabin through DOE method. First, the full vehicle model of passenger car including all its sub-systems such as engine, suspension and steering system is modeled in ADAMS/CAR and its accuracy is validated by exerting swept sine and step input. After that, the schematic geometry of sub-frame is modeled in CAD software and transferred to ADAMS/CAR. Hence, the efficiency of the sub-frame in terms of reducing the induced vibration to vehicle cabin is examined through the various road inputs e.g. swept sine, step and random road input type (B). The results will illustrate that the sub-frame has significant effect in reduction of transmitted vibration to occupants. In order to optimize the sub-frame parameters, the sensitivity analysis is performed to derive effective parameters of sub-frame using DOE method.

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.