Transactions of the Canadian Society for Mechanical Engineering

Volume 30 (2006), Issue 2

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The aim of this study is to analyze the influence of machined surface characteristics on localized corrosion in synthetic sea water. The studied material is a duplex stainless steel. Mechanical surfaces are finished by turning, grinding or burnishing after turning or after grinding. Potentio-dynamic tests show an increase of pitting potential for grinded and burnished samples. In turning, residual stresses are positive because of the elevation of temperature during machining. Grinding improves surface roughness and introduces tensile residual stresses often less important than in turning. Burnishing gives excellent surface roughness and compressive residual stresses. So, this last mechanical treatment is the best for improving corrosion resistance.

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Consideration is given, in this paper, to the numerical solution of the linear dynamic behaviour of a helical spring under loading. The mathematical formulation is constituted of two coupled, linear, hyperbolic, partial differential equations. The problem has been solved by the method of linear characteristics and the finite difference conservative scheme of Lax-Wendroff. The obtained results, with the use of these two methods, permitted to analyze the wave's propagation of the axial and angular deformations in different sections of the spring, due to an axial loading. The loading is represented by the time dependent axial velocity at the impacted end. To validate the reliability of the presented model, the computed results of the two numerical techniques are compared with the analytic solution of the studied problem.

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In this paper, in the environment of the Pro/Engineer software package, 3D model of the drive is constructed. FEM analysis package, Pro/Engineer, is used to calculate stress distribution in the elements for the toroidal drive under loads. The stress distributions on worm, stator and planet for the drive are obtained. Changes of the stress distribution along with planet rotating angle and planet number are presented. The results show: The load share among the contact tooth pairs is not uniform. The maximum stress in the stator is larger than that in the worm. As planet rotates, stress distribution on the stator and worm changes periodically. At two teeth mesh zone, the maximum stress on the stator or worm is larger than that at three teeth mesh zone. Increase of the planet number can reduce stress in the toroidal drive. It is because uniform stress distribution and more sharing points of the load.

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This work presents a curve-fitting approach and addendum-modifying procedures to eliminate the cusps of the epicycloidal planet gear for cycloid drives with two-tooth difference. Envelope theory and kinematic gearing can obtain the epicycloidal profiles. Its inevitable cusps are replaced by the smooth Bezier curves. The curve-fitting results indicate that the best curve fitting for Bezier curves is when the control points pass through the cusp of the epicycloidal profiles. For the interpolation of Bezier curves, it is better for the two reference points to be closer. If the curve-fitting curves require tangent continuity, we should apply the interpolation of Bezier curves. Two examples including six cases demonstrate the usefulness of the proposed approach.

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The estimation of exact loads or forces that cause plastic flow of the material in a metal forming process is often difficult. The main objective of this paper is to estimate the limit loads for some well-known metal forming processes, using a new generation of robust simplified methods. These methods, based on iterative linear elastic finite element analyses, are implemented by modifying the local elastic modulus of the material during subsequent iterations. On account of the possibility of local plastic collapse, the reference volume concept is invoked in order to identify the kinematically active and dead zones in the metal component. The reference volume method is shown to give a reasonable prediction of the limit load. The estimates of limit loads are then compared with corresponding results obtained using inelastic finite element analysis, and analytical solutions, with good effect.

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This paper illustrates the use of the envelope theorem for the geometric design of a cycloidal speed reducer. Specifically, it proposes two designs for a mathematical model with tooth differences: a pin wheel epitrochoid meshing - which is a cycloidal wheel (internal rotor) profile equidistant to an epitrochoid (or extended epicycloid) curve and a cycloidal wheel is generated by a pin wheel (external rotor) - and a pin wheel hypotrochoid meshing. These two contrasting structures differ in their equidistance to the epitrochoid (or extended epicycloid) curve and hypotrochoid (or extended hypocycloid) curve. Using the design result parameters, the analysis also compares contact forces and assesses curvature to determine whether the cycloidal wheel has a non-undercutting or continuous condition.

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An analytical solution for the isentropic expansion of subsonic-supersonic two-phase steam flow is provided in this paper. The results are supported by our earlier numerical computations, and available experimental values of others (1973). The two-phase mixture is assumed to undergo an isentropic expansion. However the entropy of the vapor portion of the two-phase mixture increases as the released latent heat of the condensate, reversibly moves toward the vapor, and enhances its entropy, as well as the so called "local stagnation" temperature of the vapor. The mass flow rate of the vapor portion of the two-phase mixture is obtained based on the "local stagnation" conditions, and then corrected to give the mixture mass flow rate. Most of the attempts have been made to develop the solution in a manner similar to those of the ideal gases.

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Designing a four-bar mechanism that guides a coupler system through five given poses is an old and well known problem named after L. Burmester. In this paper we show that with kinematic mapping a much neater, more comprehensive solution is obtained. It produces a univariate quartic that can be solved explicitly. Furthermore, solutions that yield ordinary four-bars, slider-cranks or elliptical trammels are identified, a-priori.