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Engine is the most common and important component in all the vehicles. An improved understanding of noise signal is required for the early detection of incipient engine component failure to achieve high reliability. In diesel engine, the combustion noise is so named to distinguish it from the noise of mechanical sources in the engine such as the valve train, fuel injection system and timing gears. On the other hand, piston slap is a combination of combustion and mechanical sources within the engine, and is not straightforward one. However, the aim of the present work is to separate the noise contributions of combustion and mechanical (motored) sources. Moreover, the noise spectra obtained when the engine was in fired condition were used to detect engine events and faults. The noise spectra were predicted based on the vibration velocity measurements, which were taken over the diesel engine surfaces (panels).

In recent years, the development of environmental friendly vehicles, such as electric vehicles and fuel cell vehicles, has further accelerated. Hybrid vehicles with regards to practical application which employ a combination of gasoline engine and electric motor remain one step ahead of the other technologies. On the other hand, as for noise and vibration (NV) phenomena, hybrid vehicles have many different features from those of conventional vehicle. Firstly high frequency noise is generated by the hybrid units, such as motor/generator and power control unit. Secondly low to middle frequency NV phenomenon tends to be worse. However, this paper describes the noise characteristics for HV induction electric motor, where its noise comprises three types namely: electromagnetic, aerodynamic and mechanical. Moreover, the influences of the cooling fans' blades number on both motor aerodynamic and total noise are presented.

Squeal from brakes is a problem in the automotive industry and large efforts are made to understand the squeal tendencies. The approach taken is mainly to change the design of the caliper, fine-tune the brake pad material and finally to trim the introducing shims on the backside of the pads. Despite these efforts still no general solutions exist. To advance the situation, a deeper understanding of the actual source of excitation of the sound in the friction interface is needed. However, in the present investigation the surfaces modifications of brake disc and pad have been tested with respect to the understanding properties. The surfaces modifications are slotted pad material and coated disc. All tests have been made in a brake test stand consisting of a complete front wheel corner of a vehicle. The changes have resulted in a significant understand of the generated noise.

Brake squeal is one of the most common problems in automobile industry that results in significant warranty cost. To reduce warranty cost due to brake squeal and provide guidance for brake design, it is important to understand the contributions of key brake design parameters for brake noise. This type of noise occurs when a brake system experiences large amplitude mechanical vibration and is audible in 1,000 to 15,000 Hz frequency range. In this paper, an approach to study the drum brake squeal based on finite elements method (FEM) is proposed that can be used as a design tool for improving the quality of the brake system. The finite element model used in the analysis consists of several major components; drum, shoes, lining (trailing and leading)…etc. The full finite element model was used to predict the brake system natural frequency and associated mode shape.

Many basic studies were conducted to discover the main reason for squeal occurrence in both disc and drum brake systems. As, it is well-known that the squealed brake system is more effective than the non-squealed brake system and it is also a common discomfort. So, cancellation of the squeal is not preferable, however, elimination of the brake squeal is a favorable. An approach to study the drum brake squeal is presented based mainly on the Finite Element Method (FEM) representation. The brake system model is based also on the model information extracted from finite element models for individual brake components. This finite element method (FEM) was used to predict the mode shape and natural frequency of the brake system after appropriate verification of FEM.

Squeal of disc brakes is considered as a main source of discomfort for passengers. Typically 1 to 4 kHz noise is considered low frequency squeal and ≻8 kHz noise is considered high frequency squeal. It is a significant problem in passenger vehicles for the comfort of the passengers and a significant financial problem for industry too. Many manufacturers of brake pad materials spend up to fifty percent of their engineering budgets on noise, vibration and harshness (NVH) issues. Squeal noise is strongly correlated to the squeal index and degree of instability of the brake system assembly. Decreasing this squeal noise to some extent during braking is very important matter for the comfort of passengers. So, a mathematical prediction model of 10-degree-of-freedom has been developed to study the effect of different brake components parameters on the degree of instability and squeal index of the brake system.

The influence of the pad contact surface deformation for vehicle brakes on its frictional behavior and friction induced noise is presented in this paper. Friction composite samples of organic binder-type brake pad have been curried out at 17 MPa and 180 °C for heavy-duty applications. However, samples with different surface shapes (solid, drilled and grooved) have been formed and tested tribologically to satisfy suitable friction coefficient at low noise level. A FAST machine was used to find out the accurate friction response at steady frictional moment. Friction acoustic noise has been carried out on the test machine using the sound pressure level meter. Analyses of the obtained results showed that the feature of the pad material surface has a significant influence on the brake frictional stability and noise emission. The results also confirmed that; adding a groove to the brake lining in heavy-duty vehicles gives a better brake performance and hence it is highly recommended.