In the present study, regarding the theoretical and practical aspects of nanoparticle capture in liquid-state processing of aluminum composite, different volume fractions of [Formula: see text] and [Formula: see text] nanopowders were incorporated into aluminum alloy via stir casting method. Hardness and sliding wear test were carried out to evaluate the mechanical properties of composites. The effects of wear load and reinforcement content on wear rate and friction coefficient of composites were examined. Microstructural studied showed that particle distribution in A356-[Formula: see text] composites was more favorable than that of the A356-[Formula: see text] samples. Results showed that nanoparticles were partially captured by aluminum matrix. With an increase in reinforcement content the amount of porosity and rejected nanoparticles increased. Regarding the wettability features of particles, the amount of introduced [Formula: see text] powders was higher than that of [Formula: see text] particles. A356-[Formula: see text] composites showed higher mechanical properties compared with those of A356-[Formula: see text] samples. Significant improvements in hardness and wear resistance were obtained in A356-1.5 vol.% [Formula: see text] composite. It was observed that the friction coefficient of the composites was lower than that of the non-reinforced alloy. With an increase in normal wear load, wear rate of composites increased and friction coefficient of reinforced samples decreased. Study on surface morphology of the worn surfaces showed both of the mild and sever wear mechanisms. The depth and number of grooves in worn surface of composites decreased with introduction of nanoparticles into matrix. The presence of oxide layers was detected on worn surface. Iron trace was observed in wear debris of samples.
A typical fixator of tibia consists of an axial rotary joint, 4 revolute joints and 2 prismatic joints in the ends providing a total of 7 degrees of freedom for its maneuverability to reduce the bone fracture in the 3-D space. The purpose of the present study was to calculate the final configuration of the fixator joints to treat a general fracture and to optimize the path to this configuration. To obtain the final configuration, the known space orientation 4×4 matrix of the assumed healed bone was set equal to the orientation matrix of the fixator and the values for the seven joints were calculated assuming a seventh equation stating the final values of the two prismatic joints to be equal. In the second part of the study, the optimal path of the adjustment procedure to the final configuration of fixator was investigated. The optimization criterion was defined as the length of the path of the bone tips throughout the procedure, so that the connective soft tissues are minimally injured. The integral of path length with respect to time was calculated, then the Lagrange equations specifying equalities between joint values and their first and second derivatives were derived. The resulting set of 2nd- order differential equations were transformed into a set of 14 1st- order differential equations, and solved using MATLAB. The significance of this approach was examined considering a simple 2 link planar mechanism, going from a specified starting position to a final configuration. It was found that implication of the optimization procedure reduces the path length by 14.3% in comparison with when the joint angles are change linearly.
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