No abstract

A simple method has been developed for calculating the stresses near the ends of a parallelsided adhesive layer. The method can be applied to adhesive layers having aspect ratios of 10 or greater, and Poisson's ratios of 0.49 or less. For a layer subject to uniform boundary conditions of displacement at the adhering surfaces, the stress fields at distances greater than about five layer thicknesses from the free surfaces are uniform. The stress field throughout the layer is uniquely determined by the stresses in the uniform stress region. If the stress field is expressed by functions of reduced coordinates of position, obtained by dividing the Cartesian coordinates by the layer thickness, these functions are for practical purposes independent of the aspect ratio or the thickness.The method has been used to calculate shrinkage stresses, the stresses in a joint under tension perpendicular to the plane of the adhesive layer, and the stresses in a joint under shear. The features of the stress fields are described, and where necessary, shown in the form of graphs or contour plots.

Designing a friction material for a brake system entails considering the effects of each constituent and the interactions that they may present between them. In the present work, a characterization of the influence of the resin-rubber ratio in a brake block material is carried out. Railway brake shoes were produced and tested in a full-scale railway dynamometer in demanding conditions. The brake blocks had also their physical and mechanical properties tested. The progressive addition of resin was proven to heavily affect the friction level in dry and wet conditions. Interestingly, the use of 5% of resin showed significantly higher friction in wet conditions. This composition also presented more severe metal pick-up. The nature of the binder also affected wear rates (which were lower for lower resin contents), and the wear mechanism. The sample using only rubber presented thermal cracks and heavier delamination as specific failure modes. Differences on the microstructure of the friction materials were observed depending on the binder. A 5% of resin appears as a very interesting choice to avoid friction loss in wet environments without incurring in high wear rates, as long as metal pick-up is by different means diminished. Otherwise, a 100% of rubber as a binder grants the instantaneous friction stability that is often threaten by thermal fade.

No abstract

No abstract