Transactions of the Canadian Society for Mechanical Engineering
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Volume 36 (2012), Issue 3
Mixed convective slip flows in a vertical parallel plate microchannel with symmetric and asymmetricwall heat fluxes
Hamid Niazmand, Behnam Rahimi
Mixed convective gaseous slip flows in an open-ended vertical parallel-plate channel with symmetric and asymmetric wall heat fluxes are numerically investigated. Buoyancy effects on developing and fully developed solutions are studied using the SIMPLE algorithm. The velocity and temperature fields are examined for different values of Knudsen number, mixed convection parameter and heat flux ratio. It is found that increasing Gr/Re leads to an increase in the heat transfer rate and friction coefficient. Also, rarefaction effects decrease the heat transfer rate and friction coefficient. The friction coefficient decreases with an increase in heat flux ratio.
An approach for counting the number of specialized mechanisms subject to non-adjacency constraints
Yii-Wen Hwang, Chiu-Chin Wu, Shu-Hong Lin
This paper presents an improved approach to count the number of specialized mechanisms subject to non-adjacency constraints from a candidate kinematic chain. First, the permutation group of the candidate kinematic chain is found. Next, an inventory polynomial named kinematic king polynomial (KKP) to count the specialized mechanisms is modified from the traditional king polynomial related to the count of moves of a king on a chess. Then, an algorithm to calculate the KKP is presented by operations on labeled joint adjacency matrix (LJAM). Finally, two examples are illustrated to verify the approach.
Research on theory and applications of virtual tolerance
Wang Xiaohui, Ren Shouhua
Tolerance where the upper deviation is smaller than the lower deviation is defined as virtual tolerance. The essence of virtual tolerance is illustrated in this paper: the absolute value of virtual tolerance is the amount of error compensation whose range is the difference between the upper deviation and the lower deviation. This value can be described as virtual tolerance and provides a basis for the theory of tolerance. Based on this theory, we can unify calculation principles and methods regarding various types of assembly dimension chains, accurately calculate the tolerance of dimensional chains for assembly with compensation assemblies, and put forward a general calculation method for false waste product intervals.
Experimental studies on the microstructure and hardness of laser transformation hardening of low alloy steel
Purushothaman Dinesh Babu, Gengusamynaidu Buvanashekaran, Karupuudaiyar R. Balasubramanian
An experimental investigation with Nd:YAG laser system was carried out to study the effects of laser hardening process parameters on the microstructure and hardness during laser hardening of EN25 steel. The laser beam is allowed to scan on the surface of the work piece by varying the laser beam power (750–1250 W) and travel speed (500–1000 mm/min) of the work table. The microstructural features of the laser hardened EN25 steel were analysed using optical microscope. The microstructure of the surface layer was found to consist of plate martensite. A substantial increase in surface hardness was achieved, by a factor of 2 times the base material hardness.
Dimensional inspection of translating cams by CNC coordinate measuring machine
In this paper, a simple and analytical method is proposed for accomplishing the inspection procedure. In the proposed approach, a kinematic model of the cam profile is derived using homogenous coordinate transformation theory. The normal vectors and principal curvature of the designed translating cam are then derived from the analytical expression for the cam profile. Based on the coordinates and normal vector of each specified point on the cam profile, the NC data required to move the CMM inspection probe to the surface of the cam are then obtained. A least-square fitting method is proposed to minimize the inspection error caused by a misalignment of the actual evaluation frame relative to the ideal frame.
Modelling and analysis of a piezoelectric annular stator structure for a new in-situ dynamic balance regulator
Zhe Du, Xuesong Mei, Muxun Xu
This paper presents the modelling and analysis of a piezoelectric annular stator structure for a new in-situ dynamic balance regulator which is driven by the in-plane bending vibration of the stator. The mathematical model for the in-plane vibration is first developed using an analytical method to determine the theoretical excitation frequency. The excitation modes and structural parameters are then analysed to optimise the performance of the stator. To improve the efficiency of the design and to achieve precise control, a semianalytical electromechanical coupling model is developed using the dynamic substructure method and the finite element method. The model is verified in preliminary tests.
Controllable workspace of cable-driven redundant parallel manipulators by fundamental wrench analysis
Azadeh Zarif Loloei, Hamid Taghirad
Workspace analysis is always a crucial issue in robotic manipulator design. This paper introduces a set of newly defined fundamental wrenches that opens new horizons to physical interpretation of controllable workspace of a general cable-driven redundant parallel manipulator. Based on this set of fundamental wrenches, a novel tool is presented to determine configurations of cable-driven redundant parallel manipulator that belong to the controllable workspace. Analytical expressions of such workspace boundaries are obtained in an implicit form and a rigorous mathematical proof is provided for this method. Finally, the proposed method is implemented on a spatial cable-driven manipulator of interest.
Stifness analysis of two compliant pivots used in series elastic actuators
Shusheng Bi, Tao Qiao, Hongzhe Zhao, Jingjun Yu
A compliant pivot used in series elastic actuators (SEAs) can be of great practical use for saving structure space. The analysis of load-deflection behavior for such pivots can provide an analytical mechanical design method. In this paper, two pivots are proposed for the corresponding implementation. Based on the Awtar accurate approximations, the two annulus compliant pivots are further simplified to linear stiffness behavior for the SEAs applications. Specifically, an annulus compliant pivot based on parallel leaf-springs is firstly analyzed. After that, we focus on a special kind of annulus compliant pivot whose degree of constraint (DOC) was released. Finally, the accuracy characteristics of the models are identified by comparing with the results obtained by nonlinear finite element analysis.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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