http://hdl.handle.net/10453/87 Sun, 19 May 2013 06:36:45 GMT 2013-05-19T06:36:45Z http://hdl.handle.net/10453/18410 Time-varying Total Stiffness Matrix Of A Rigid Machine Spindle-angular Contact Ball Bearings Assembly: Theory And Analytical/experimental Verifications El-Saeidy Fawzi A lagrangian formulation is presented for the total dynamic stiffness and damping matrices of a rigid rotor carrying noncentral rigid disk and supported on angular contact ball bearings (ACBBs). The bearing dynamic stiffness/damping marix is derived in terms of the bearing motions (displacements/rotations) and then the principal of virtual work is used to transfer it from the bearing location to the rotor mass center to obtain the total dynamic stiffness/damping matrix. The bearing analyses take into account the bearing nonlinearities, cage rotation and bearing axial preload. The coefficients of these time-dependent matrices are presented analytically. The equations of motion of a rigid rotor-ACBBs assembly are derived using Lagrange's equation. The proposed analyses on deriving the bearing stiffness matrix are verified against existing bearing analyses of SKF researchers that, in turn, were verified using both SKF softwares/experiments and we obtained typical agreements. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10453/18410 2011-01-01T00:00:00Z http://hdl.handle.net/10453/18411 Transient Responses Of A Hydraulic Power Assisted Vehicle Steering System Zhang Nong This paper presents a comprehensive model of a hydraulic power steering system for predicting the transient responses under various steering inputs. The first principles of multi-body system dynamics and fluid mechanics are applied to model key nonlinear Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10453/18411 2011-01-01T00:00:00Z http://hdl.handle.net/10453/18413 A multi-criteria topology optimization for systematic design of compliant mechanisms Luo Zhen; Zhang Nong This paper attempts to present a new multi-criteria topological optimization methodology for the systematic design of compliant micro-mechanisms. Instead of employing only the strain energy (SE) or the functional specifications such as mechanical efficiency (ME), in this study an alternative formulation representing multiple design requirements is included in the optimization to describe the performance of compliant mechanisms. In most conventional designs, SE is used to only measure the design requirement from the point of view of structures, while ME is usually applied to describe the mechanical performance of mechanisms. However, the design of a compliant mechanism is required to comprehensively consider both the structural and mechanical performance quantities. Displacement, material usage and dynamic response are imposed as three external constraints to narrow the searching domain. In doing so, the multi-criteria optimization problem involving the SE and ME can reasonably embody the mechanical structural characteristics of compliant mechanisms. A sequential convex programming, the method of moving asymptotes (MMA), is applied to solve the topological optimization problem, which can not only ensure numerical accuracy but also both the monotonous and non-monotonous structural behaviors. SIMP model (solid isotropic material with penalization) is used to indicate the dependence of elastic modulus upon regularized element densities. Several typical numerical examples are used to demonstrate the effectiveness of the proposed methodology, and the prototype of a resulting mechanism has also been manufactured to validate the design of the compliant mechanism. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10453/18413 2012-01-01T00:00:00Z http://hdl.handle.net/10453/18412 Topology optimization for static shape control of piezoelectric plates with penalization on intermediate actuation voltage Kang Zhan; Wang Xiaoming; Luo Zhen This paper investigates the simultaneous optimal distribution of structural material and trilevel actuation voltage for static shape control applications. In this optimal design problem, the shape error between the actuated and the desired shapes is chosen as the objective function. The energy and the material volume are taken as constraints in the optimization problem formulation. The discrete-valued optimization problem is relaxed using element-wise continuous design variables representing the relative material density and the actuation voltage level. Artificial interpolation models which relate the mechanical piezoelectrical properties of the material and the actuation voltage to the design variables are employed. Therein, power-law penalization functions are used to suppress intermediate values of both the material densities and the control voltage. The sensitivity analysis procedure is discussed, and the design variables are optimized by using the method of moving asymptotes (MMA). Finally, numerical examples are presented to demonstrate the applicability and effectiveness of the proposed method. It is shown that the proposed method is able to yield distinct material distribution and to suppress intermediate actuation voltage values as required. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10453/18412 2012-01-01T00:00:00Z