Computational Methods in Engineering

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Due to the widespread applications of fiber reinforced polymer composites in various industries, the machining of these materials to reach the desired shapes, close tolerances and surface finish quality is of great importance. But the composite materials are anisotropic and are mostly prepared in laminated form and, therefore, they have special chip formation behaviour. Among the effective parameters in machining of these materials, the angle between the fiber orientation and machining direction and also the properties of fiber and matrix are of great significance. In the present paper, using the latest theories in the field of machining of FRP materials, a mathematical model to improve the feed rate as well as the cutting speed with respect to the fiber orientation has been introduced and, a computer package was developed for the 3-dimensional CNC machining of fiber composite materials. A number of composite pieces were fabricated and machined to check the output of the programme and the work pieces. Besides the reduction in the machining time, the machined work pieces had desired surface quality, while the common defects like matrix burning, delamination and fiber pullout were completely absent. Keywords: Fiber composite Materials, Machining, Software, Cutting force, fiber orientation

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In this paper,  a numerical model  was first verified against dynamic centrifuge tests results performed on an
underground subway tunnel and then, the effect of underground structure on peak ground acceleration (PGA) at the ground
surface investigated considering linear and nonlinear behavior for the soil. The results show that in the range of natural
frequency of the system, nonlinear model shows deamplification of PGA with respected to the freefield. Whereas, linear model
shows opposite trend. Out of the range of natural frequency of the system, linear and nonlinear models predict same results and for both model, underground tunnel resulted in amplification of  low frequencies and deamplification of high frequencies with
respected to the freefield.