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The rollover problem had a great concern in the last few years, where various mathematical models for vehicle rollover were developed. The main parameters that are essentials for assessment of vehicle rollover are suspension stiffness, shock absorber damping, and tire stiffness and damping in addition to vehicle weight and geometry. It is a difficult task to change these parameters during a real vehicle dynamic testing. Moreover, such dynamic test is almost a destructive one due to severity of rollover crashes [ 1 ]. Also, a real vehicle dynamic testing has many disadvantages which cannot be easily avoided such as the effect of driver behavior, the cost of instrumentation and equipment, time consumption, and effect of outriggers on the vehicle roll mass moment of inertia. In the present paper, the adoption of a scaled vehicle lab model (VLM) to study the effect of design parameters on vehicle rollover instead of destructive vehicle dynamic testing has shown its validity.

The stability of vibratory motions of the drum/shoe assembly in drum brakes, is studied. The behavior of this assembly is explained in terms of the vibration modal numbers of the drum and the shoe. The equations of motion of the distributed parameters system are obtained where both motions of drum and shoe are considered to be coupled by the tangential distributed friction force. This force is generated by frictional sliding between the rotating drum and a pinned-pinned shoe and it depends on the relative velocity of sliding. The domains of stability at different vibrational modes of both drum and shoe are shown. Geometric induced instability is likely to occur at the first mode of the drum for all extension modes of the shoe. In case of flexural modes of the shoe, instability is found to be dependent upon the drum radius and the angle subtended by the shoe.

Modeling of friction pad in disc brakes as a distributed parameter system (mass-inherent damping-elasticity) is made in order to show the conditions of stable vibrations, The interface characteristics of the pad/disc assembly beside the negatively sloped friction-velocity relationship are taken into account. The interface characteristics are represented by the effective contact stiffness as well as the friction damping of both pad and disc surfaces. It is shown that continuous modification of the equivalent contact stiffness by wear mechanism or by any other mechanism, is the mean cause of squeal triggering. The analysis has shown that stability can be attained at all possible squeal frequencies of the friction pad by the good selection of its geometrical configuration (thick, wide and short brake pad) and its material loss factor within certain limits. Moreover, it is necessary to choose the appropriate way of pad fixation inside the caliper to give higher modes of vibrations.