Journal of Computational and Applied Research in Mechanical Engineering
Volume:1 Issue: 1, Autumn 2011

This paper addresses the mixed integer reliability redundancy allocation problems to determine simultaneous allocation of optimal reliability and redundancy level of components based on three objective goals. System engineering principles suggest that the best design is the design that maximizes the system operational effectiveness and at the same time minimizes the total cost of ownership (TCO). To evaluate the performance of the TCO allocation numerical experiments were conducted and compared with previous for the series system, the series-parallel system, the complex (bridge) system and the over speed protection system. From the results of the numerical investigation, reliability redundancy allocation based on minimum TCO will lead to a more reliable, economical design for the manufacturer as well as user compared with the initial cost optimum design and conventional reliability optimum design

In this paper, the dynamic simulation for a high pressure regulator is performed to obtain the regulator behavior. To analyze the regulator performance, the equation of motion for inner parts, the continuity equation for diverse chambers and the equation for mass flow rate were derived. Because of nonlinearity and coupling, these equations are solved using numerical methods and the results are presented. Additionally, the dynamic analysis results consist of the output pressure change versus time, the displacement of the moving parts versus time, the regulator mass flow rate versus time and the output pressure versus mass flow rate in different controlling spring pre-loads. Furthermore, the sensitivity analysis is carried out and the main parameters affecting the regulator performance are identified. Finally, the results of the dynamic simulation are validated by comparing them with the experimental results.

The aim of this work is to investigate the variational discretization and mixed finite element methods for optimal control problem governed by semi linear parabolic equations with integral constraint. The state and co-state are approximated by the lowest order Raviart-Thomas mixed finite element spaces and the control is not discreted. Optimal error estimates in L2 are established for the state and the control variable. As a result، it can be proved that the discrete solutions possess the convergence property of order. Finally، a numerical example is presented which confirms the theoretical results.

In sheet metal forming processes with complex strain paths، a part is subjected to large plastic deformation. This severe plastic deformation leads to high plastic strain localization zones and subsequent accumulation of those strains. Then internal and superficial micro-defects and in other words ductile damage is created. This damage causes quality problems such as fracture. Therefore، design engineers need to accurately estimate the damage initiation and its growth. In this paper، initiation and evolution of damage has been predicted using Lemaitre’s damage and forming limit diagram (FLD) damage models for automotive panel forming، because of its nonlinear strain paths. Lemaitre’s damage criterion has been implemented as a subroutine for an elastic-plastic material and plane stress and finite strain theories. Using this subroutine in explicit finite element code، damage initiation and evolution is predicted for the above mentioned process and the results obtained by FLD and Lemaitre models are compared. In this paper، FLD and Lemaitre damage models results show the fact that the damage localization zones are corresponding to the equivalent plastic strain distributions. Comparison of the FLD damage and Lemaitre damage results show that in an automotive panel forming process، both models predict initiation of cracks in the edges of a sheet. Hence، it is concluded that finite element method combined with continuum damage mechanics can be used as a reliable and rapid tool to predict damage evolution in sheet metal forming processes with nonlinear and complex strain paths such as automotive panel forming.

Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet metal parts. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. Material property of AISI 1010 is used in FE model and experiments. The aim of this study is to identify the response related to deformation and characterize the effect of laser power with respect to the bending angle for a square sheet part. An experimental setup including a Nd:YAG laser Model IQL-10 with maximum mean laser power of 500 W is used for the experiments to verify FE analysis results. It is observed that numerical results are relatively in good agreement with the experimental results. Results also show that increasing laser power increases the bending angle.

This paper shows the coordinates influence on singularity of a three degree-of-freedom structure, namely, three-Universal-Prismatic-Spherical (3-UPS) parallel manipulator. Rotational coordinates, which are chosen to define the orientation of the platform, affect the singularity of the manipulator. Euler parameters, which don''t have any inherent geometrical singularity are utilized, however they are dependent coordinates. This paper shows the advantage of Euler parameters rather than Euler angles as the rotational coordinates for the manipulator. Additionally, the real loci of singularity for the manipulator due to its structure are predicted.

This paper is concerned with an investigation into the localized instability of a thin elastic orthotropic semi-infinite plate. In this study, a semi-infinite plate, simply supported on two edges and under different boundary conditions of clamped, hinged, sliding contact and free on the other edge, is studied. A mathematical model is used and a general solution is presented. The conditions under which localized solutions exist are investigated.