Transactions of the Canadian Society for Mechanical Engineering
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Volume 40 (2016), Issue 1
Comparison of experimentally measured and simulated workpiece and grinding wheel topography using a new dressing model
Abdalslam Darafon, Andrew Warkentin, Robert Bauer
This paper presents a new empirical model of the dressing process in grinding which is then incorporated into a 3D metal removal computer simulator to numerically predict the ground surface of a workpiece as well as the dressed surface of the grinding wheel. The proposed model superimposes a ductile cutting dressing model with a grain fracture model to numerically generate the resulting grinding wheel topography and workpiece surface. Grinding experiments were carried out using "fine", "medium" and "coarse" dressing conditions to validate both the predicted wheel topography as well as the workpiece surface finish. For the grinding conditions used in this research, it was observed that the proposed dressing model is able to accurately predict the resulting workpiece surface finish for all dressing conditions tested. Furthermore, similar trends were observed between the predicted and experimentally-measured grinding wheel topographies when plotting the cutting edge density, average cutting edge width and average cutting edge spacing as a function of depth for all dressing conditions tested.
Adaptive sparse galerkin methods for vibrating continuous structures
Zaid Ahsan, Thomas K. Uchida, Chandrika P. Vyasarayani
Adaptive reduced-order methods are explored for simulating continuous vibrating structures. The Galerkin method is used to convert the governing partial differential equation (PDE) into a finite-dimensional system of ordinary differential equations (ODEs) whose solution approximates that of the original PDE. Sparse projections of the approximate ODE solution are then found at each integration time step by applying either the least absolute shrinkage and selection operator (lasso) or the optimal subset selection method. We apply the two projection schemes to the simulation of a vibrating Euler–Bernoulli beam subjected to nonlinear unilateral and bilateral spring forces. The subset selection approach is found to be superior for this application, as it generates a solution with similar sparsity but substantially lower error than the lasso.
Performance analysis of a thermoelectric power generator under volumetric constraint
Ahmet Z. Sahin, Bekir S. Yilbas
The efficiency of a thermoelectric power generator can be optimized through proper sizing of the device geometric configurations. In the present study, pin length optimization of the thermoelectric generator for a fixed total pin volume is carried out and the pin length maximizing the device efficiency is formulated. The influences of temperature ratio, defined as the upper junction temperature divided by the lower junction temperature, and the figure of merit, defined as Z = α2/KR, on the device efficiency and output power operating at the optimum pin length are examined. It is found that a unique temperature ratio exists which maximizes the efficiency of the thermoelectric device with the optimum pin length.
On the new mechanical press with a planetary gear train
A new 1-DOF mechanical press with a geared eight-bar linkage mechanism is presented. The proposed press can generate the required kinematic and dynamic performance for drawing, stamping, deep drawing, and precision cutting processes by simply adjusting the offset of the ram. The press consists of an elementary planetary gear train with a pair of planet gears, a slider-crank mechanism, and a slider-crank mechanism with a variable-length crank. The configuration and a solid model are described, and a kinematic analysis, dynamic analysis, and optimized dimensional synthesis of the press are discussed. Examples are provided to verify the feasibility and effectiveness of the design methodology. The proposed press could lead to more flexible and cost-effective applications.
Mapping discrete-time models for descriptor-systems with consistent initial conditions
Shin Kawai, Noriyuki Hori
Discretization of a regular continuous-time descriptor-system, whose initial condition is consistent with its input, is considered using a general mapping method presented in our previous paper. The proposed mapping discrete-time model is shown to be a proper discretization under the definition explained in the paper. This assures that the response of the mapping model approaches that of the continuous-time descriptor system as the sampling period approaches zero. The consistency of initial conditions for the discrete-time model is also studied and the long-standing issue of ambiguities surrounding irregularities of discrete-time responses at the initial time are clarified with a simple solution. A proper range of design parameters are investigated and their suitable choices suggested. To illustrate the use of the proposed method, a simple circuit that cannot be expressed in the ordinary state-space form is considered. Its responses to a sinusoidal input when started from the consistent and inconsistent initial conditions are simulated to show that the irregularities at the initial time can be overcome easily. The proposed technique provides a convenient simulation and design environment for handling discrete-time systems in a unified manner with consistency and ease.
Experimental investigation of the vibrations of a simply supported rod immersed in an axial flow with a nozzle midway
William Zrymiak, Mark Siminowski, Brahim Chebbi
Experiments to study the induced vibrations of a simply supported rod resulting from an axial flow with a constricting nozzle midway are described. Nozzles with different geometries are used. The results are compared to published data in the literature. It is shown that the vibration of this rod for a particular flow velocity beyond the critical value changes both direction and trajectory. It is also shown that machining cuts on a particular mounted nozzle helps suppress the amplitude of the flow induced vibrations.
Design and analysis of cam mechanism with negative radius roller-follower
This paper presents a simple method for the design and analysis of a cam mechanism with a negative radius roller-follower. In the proposed approach, conjugate surface theory is employed to derive a kinematic model of the cam mechanism. Analytical expressions for the pressure angle and principal curvatures of the cam profile are then derived. Finally, analytical expressions for the angular velocity and angular acceleration of the roller are derived. The validity of the proposed design methodology is demonstrated by machining a cam mechanism having a negative radius roller-follower with a radius of 100 mm.
Multi objective optimization of turning parameters using combined MOORA and entropy method
Selection of optimum machining parameters in machining operations leads to good functional attributes for the machined components and increased productivity. In this work, machining parameters and nose radius are optimized in turning of EN25 steel with coated carbide tool by the application of combined Multi-Objective Optimization by Ratio Analysis (MOORA) and entropy measurement method. The selected machining parameters are cutting speed, feed rate, depth of cut and nose radius for minimization of surface roughness, micro-hardness and maximization of Material Removal Rate (MRR). Entropy concept has been used to assign the weight criteria of each objective being considered. The optimum combination of machining parameters and nose radius are obtained using normalized assessment values. The results obtained in the analysis are validated and the results based on turning process responses can be effectively improved.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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