Automotive manufacturers currently face a challenge with expeditious enhancement of the vibro-acoustic properties of their vehicles. A major reason for this setback is the limited design information available during initial development stages added with limited knowledge of damping within complex structures. It is now well established that CAE studies of vibration energy flow show good correlation between power flowing into trimmed body and the interior noise produced. Aim of the dissertation is to harness this "good" correlation between power input and interior noise, by learning about the changing behaviour of system in different suspension damping scenarios. It investigates how the mechanical power input to body from suspension, interior road noise produced, and their relation is affected by changing the way damping is modelled into suspension. This is being done to make stronger design decisions from NVH point of view during the concept phases of vehicle development. The investigation is for vehicle programs during early development phases, and hence a simplified vehicle CAE model was chosen, that contains a trimmed body with cavity fluid, and wheel suspension to capture all relevant effects of varying damping. Then, a detailed flowchart of suspension and trimmed body connections was prepared to understand how power flows into the trimmed body through suspension. Using results of power flow study, the most relevant paths and their frequency ranges were identified (to reduce the number of parts in study, yet results relevant and easily extrapolatable to a larger system). Lastly, responses are analyzed for various damping cases of suspension and trimmed body.  Results obtained show a reducing trend in mechanical input power and interior noise values with increasing damping in system. Whereas, for good correlation between power and noise, a great inclination towards structural damping localized into bushings is observed compared to other damping cases. Additionally, a strong dependency of noise, active power and reactive power is observed on trimmed body and cavity fluid damping. Active power is reduced when trimmed body damping is decreased to zero, and more so when cavity fluid damping is put to zero. On the other hand, noise and reactive power have an exact opposite correlation compared to active power and noise. These results suggest that although active mechanical input power is the cause of interior noise, their correlation starts to deteriorate with reducing damping within the system, and instead it is the reactive power that starts to correlate better at very low damping values. But, it is physically impossible to have no damping or very low damping, so a modelling of damping within suspension that provides relatively better correlation between (active) input power and noise is when structural damping is localized within connectors.

Over the past century, the automobile has become an integral part of modern industrializedsociety. Consumer demands, regulatory legislation, and the corporate need togenerate a profit, have been the most influential factors in driving forward the evolutionof the automobile. As the comfort, safety, and reliability of the automobile haveincreased, so has its complexity, and most definitely its mass.The work within this thesis addresses the twofold problem of economy and ecologywith respect to sustainable development of automobiles. Specifically, the conflictingproblems of reducing weight, and maintaining or improving noise, vibration, andharshness behaviour are addressed. Potential solutions to these problems must also beexecutable at the same, or preferably lower production costs. The hypothesis is that byreplacing acoustic treatments, aesthetic details, and complex systems of structural componentsboth on the interior and exterior of the vehicle with a single multi-functionalbody panel, functionality can be retained at a reduced mass (i.e. reduced consumptionof raw materials) and reduced fiscal cost.A case study is performed focusing on the roof structure of a production vehicle. Fullvehicle and component level acoustic testing is performed to acquire acoustic functionalrequirements. Vibro-mechanical testing at the component level is performedto acquire structural functional requirements complimentary to those in the vehiclesdesign specifications. Finite element modelling and analysis is employed to createa model representative of the as-tested component and evaluate its acoustic and mechanicalbehaviour numerically. Results of numerical simulations are compared withthe measured results for both acoustic and mechanical response in order to verify themodel and firmly establish a set of acoustic and mechanical constraints for future work.A new, multi-layered, multi-functional sandwich panel concept is proposed which replacesthe outer sheet metal, damping treatments, transverse beams, and interior trimof the existing structure. The new panel is weight optimized to a set of structural constraintsand its acoustic properties are evaluated. Results show a significant reductionin mass compared to the existing system with no degradation of the acoustic environment.A discussion of the results is presented, as is a suggestion for future research.

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An investigation on noise transmission through the steering gear system is focused on the area of vehicle NVH (Noise Vibration and Harshness). From previous investigations it is well known that noise transmission through the steering system sometimes has a significant influence referring to tire road noise. In these cases, the interface force between steering gear and vehicle subframe is usually of interest during early stages of vehicle development. The target of the current work is to validate an approach based on a method, commonly known as the “Blocked force method” for noise and vibration testing, and check if it is possible to estimate the interface forces based on this method. This method became popular for mechanical testing in the middle 1900s [1] [2] [3], because of its easy applicability. The basic idea is to fix the component on a rigid plate and measure the interface force at the coupling points with force transducers inserted in between. It has a considerable potential in practical use, because if the blocked force could provide a good estimation for the interface force in noise transmission, it enables an efficient measurement of critical NVH behaviors without having to resort to the complete vehicle.However intuitively, the blocked force data could not be used directly. As a result, a coupled system equation is used for the coupling of the steering gear and the car body. Both the inertance of car body and steering system are taken into account, and thus introduces a compensation for the difference between vehicle and test bench. The method is validated against the transfer function measured on the full vehicle as the reference and compare this with the result calculated with the measured “Blocked force” data. Siemens Test.Lab is used for data acquisition and first data processing. Matlab is used for data post processing. Matrix symmetrization and singular value truncation is used to deal with the ill-conditioned data of steering gear inertance. A hybrid model with Finite Element data is proposed. Two test conditions are investigated: one set is with rigid coupling and the other is decoupled with rubber.

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This study evaluates noise and vibrations in a heavy freight locomotive cab, and provides several measures for providing more comfort to the crew. A full-scale production cab and sill structure is used to provide the results. The cab is setup in a controlled laboratory environment in a manner similar to the installation on a locomotive. Field measurements are used to emulate actual vibration input to the cab structure. A 16-channel data acquisition system is used to collect both noise and vibration data on various parts of the cab structure and inside the cab. Upon establishing the baseline for laboratory vibration measurements and correlating them with field data, a design of experiment was conducted to evaluate the vibration contribution of various parts of the cab. This showed that the cab floor and cab roof had the largest vibrations. A series of solutions including stiffening the cab floor and damping the cab roof were investigated. The results showed that although such solutions reduce localized vibrations, the overall effect on reducing cab interior noise is minimal. As a more global solution, the cab was isolated from the sill structure through six elastomeric elements mounted at the base of the cab and at the crash post. The mounts at the base were selected such that they support the static weight of the cab, provide a resonance frequency that is below the excitation range, and offer good lateral and longitudinal stability. Two tube-form elastomeric mounts were placed between the cab structure and the crash posts which attach to the front of the sill structure. The test results showed that the soft-mounted cab had significantly lower noise and vibration than the original cab. The vibration levels were reduced 10 to 100 times at certain locations and frequency ranges. The overall noise level was reduced by approximately 6 dBA. In an attempt to provide an estimate of effectiveness of the mounts with different stiffness values, a simulation model was prepared in Matlab. Although the model did not yield accurate results, it resulted in several recommendations for future research work. / Master of Science

Hot spotting of automotive disc brakes is an undesired thermal localisation phenomenon, which is a challenge for numerical modelling in terms of both accuracy and efficiency especially for complex disc geometry. In this research, the aim was to develop a computationally efficient finite element (FE) approach for 2-piece pin-mounted ventilated disc hot spot prediction with acceptable accuracy enabling parametric studies to contribute to the knowledge of the complex mechanisms. A time reduction strategy for the simulations was established by incorporating an axisymmetric brake pad assumption with material scaling factor and the friction characteristics were defined by a user-subroutine. The computing accuracy and efficiency of this method were then verified by comparing with traditional FE models. 2D in-plane, 2D out-of-plane, and 3D models were performed to investigate the effects of ventilated disc hot spotting, radial hot spot/band migration, and hot spotting of realistic complex disc geometry respectively. Both 2D and 3D results were validated using experimental results based on a laboratory dynamometer and showed good correlation. The results suggested that adequate modelling of friction pair contact pressure distribution and the subsequent non-uniform heat generation is essential for hot spot simulation; speed was identified as the determinant for the number of hot spots, whereas hot spot temperature was determined by energy level. Furthermore, recommendations for vent design, pins, disc run-out, cooling, material selection, wear rate, pad length and loading distribution were given. Finally, hot spotting and hot band migration cause-effect chains were established based on the results and discussion. / Appendix 1 and Appendix 2 are unavailable online due to copyright restrictions.

The thesis deals with the design of the experimental testing rig. Test rig is designed to measure NVH transmission parameters. First, basic knowledge of vibro-acoustic measurement is discussed. This is followed by an evaluation of the most commonly used power devices to derive real loads on measured gearboxes. In more detail, a back-to-back test rig is disassembled among other things. In the thesis are described two main components, which are composed of a connecting element and a test bench. Both components were optimized during the design due to their modal properties. Numerical modal analysis was performed in ANSYS Workbench software. The thesis also includes strength calculations performed using both numerical and analytical approaches. The indispensable result of the design work is the complete drawing documentation. Finally, measurements of vibrations and noise on the physically made connecting element assembly have been performed and subsequently evaluated.