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This paper as part IV of a series articles first very briefly reviews squeal generation process in terms of energy transfer. A squeal reduction and prevention cascade chart including various contribute elements is formed. Subsequently, variation ranges of some key parameters of brake components and system due to manufacturing processes and operational/usage condition changes are given. Design concept of a broad stable and less vibration brake system is proposed and addressed in light of these variations. Robust design criteria and strategies are discussed. Design tools and methods are summarized. At last, some application examples are provided.

The understanding, prediction and prevention of brake squeal is a difficult and challenging problem because of the large number of design variables involved in a complex brake system and many operational and environmental conditions under which squeal may occur. The design variables may have different optimal values and different contribution trends for different brake systems. Since the 1930's, much progress has been made in gaining physical insight into brake squeal mechanisms and causes, and brakes have become quieter. However, the recurring occurrence of disc brake squeal indicates that our understanding of the phenomenon is both insufficient and incomplete, and that brake squeal is still a quality issue in the automotive industry and its prevention is far from reality. Part I of this series of articles first reviews the various hypotheses put forth for brake squeal mechanisms and causes.

This article, as part III of a series, briefly reviews some of the representative literature on brake squeal testing and evaluation. It discusses the potential influence of variation within brake components and operational conditions on brake squeal dynamometer tests and their correlation to vehicle road tests. Roles and challenges of component/system parameter measurements such as brake pad damping, disc rotor in-plane mode and friction induced vibration characteristics, friction coefficient, moisture absorption and elastic constants of lining material, and contact stiffness are addressed. An application example of a reliability method to assure dynamometer test results are statistically significant is presented. The advantages of using laser metrology are also briefly described, especially the measurement of 3D squeal operational deflection shape. Lastly, general future research directions are outlined.