Reliability studies on the influence of joint clearance on the kinematics of the nose landing gear mechanism of a transport aircraft using contact theory
Contact between two objects is an important facet in multibody dynamics. It is a discontinuous, non linear phenomenon and consequently it requires iterative simulations. The paper presents the reliability evaluation of the retraction landing gear mechanism by three contact models Viz. Impact Function Model, Coefficient of Restitution Model and Clearance Link Model. The simulations have been performed using the standard commercial multibody dynamics software ADAMS. The precision of these simulations depends on user defined parameters like stiffness, Damping, Penetration Depth, Force exponent, Penalty and Restitution Coefficient that impacts the overall reliability of the mechanism. The optimal value of these parameters have been obtained by an optimization process using Design of Experiments tool available in ADAMS to match with the nominal values without any clearance. The overall reliability of the mechanism has been evaluated at different instants of the retraction cycle by using Response Surface Based Monte Carlo Simulation and Direct Monte Carlo Simulation by using in house codes created in MATLAB software. The comparison, significance and accuracy of the results obtained using the above mentioned approaches has been discussed and the impact based contact modelling for the clearance appears to be accurate and realistic for practical applications.