A semi-analytical method has been developed for computing the dynamic response of railways composed of viscoelastic layers under moving loads. One of the aims of this new approach is to be able to simulate railways incorporating asphalt materials. These materials are increasingly used or highly considered for construction projects. We have modeled the mechanical behavior of bituminous mixes with the Huet– Sayegh thermo-sensitive viscoelastic law that is specifically intended for such materials. This method, implemented in a numerical program, is based on a quasi-stationary approach, so that time is not a specific factor in the solution. The required calculation time is therefore small, for the convenience of para-metric studies. The capability of this method is proved with a numerical example that provides several validation points and illustrates at the same time the temperature effect on the response of a railway including an asphalt layer
International audienceThis article covers an in plane experimental characterisation of a polypropylene glass fibre reinforced woven composite. Tensile, shear and compression loadings were carried out with a standard tensile rig and a crossbow/Hopkinson pressure bar rig. The specimen strain was measured by digital image correlation technique. It is concluded that the composite stiffness and strength are highly sensitive to strain rate. Static and dynamic multicycle tests were also undertaken to identify and quantify softening phenomenon. Thus, permanent plastic strain and reduction in stiffness are observed and quantified
Cable-Driven Parallel Robots (CDPRs) are a type of parallel robots that have the particularity of using cables as legs. CDPRs have several advantages such as large workspaces, high acceleration and high payload capacity. However, CDPRs present also some drawbacks such as the possible collisions between their cables and environment. Therefore, this paper is about the geometric determination of the cable-cylinder interference regions in the workspace of a CDPR. The cables are considered massless and straight. Then, the boundaries of the interference regions onto the cylinder form a closed loop composed of arcs and straight line segments that can be expressed symbolically. Those geometric entities generate truncated cones and planes corresponding to the boundaries of the volume of interferences. Finally, a methodology is described to trace the cable-cylinder interference free constant orientation workspace of CDPRs.
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