Applied Mechanics and Materials Vols. 110-116

Abstract: This study explores the method of extracting modal parameters of constrained structure from test data. The normal mode spectrum matrix constituted of low order frequencies of the structure can be derived from the free test data, while the normal mode shapes and the extra high order modes can be obtained through FEM analysis; The boundary constrains are equivalent as a kind of sub-structure, and the modal synthesis is used to extract the constrained modal parameters. Experiment and simulation are conducted and the results show that the extraction method based on the modal synthesis and which combines the experiment model and the analytical model is feasible.

Abstract: The paper presents a non conventional technique to predict the constitutive behavior of materials by assessing the true stress–true strain relationship through miniature specimen tests. The miniature test was conducted on two different types of steel ring specimens (outer diameter14mm, inner diameter 8mm, thickeness 0.5mm) with V-notch (1mm depth) added diametrically to it. A finite element model was developed and validated to calculate the load–deflection curve obtained from the miniature specimen experiment. The constitutive behavior assigned to the specimen for the calculations was determined from the standard tensile test. Using an inverse methodology, it was possible to show that the constitutive behavior from the miniature tests using inverse FE procedure, and that from the conventional standard ASTM test bears close resemblance.

Abstract: There is increasing demand for developing smart structures in various electronic and electromechanical systems during past two decades. The modeling analyzing and manufacturing of these small-scale components remained always a challenging job. Finite element capability available in commercial software package ANSYS makes it convenient to perform modeling and analyzing of these smart structures. In this study a 3-D finite element analysis for cantilever plate structure excited by patches of piezoelectric actuator is presented. To investigate the influence of actuator location and configuration of piezoelectric actuators attached to the plate structure in order to identify the optimal configuration of the actuators for selective excitation of the mode shapes of the cantilever plate structure. The finite element modeling based on ANSYS package using modal analysis and harmonic analysis is used in this study for cantilever plate structure excited by patch type of piezoelectric actuators of PZT-5A at different locations of same geometrical parameters on the cantilever beam. The results clearly indicate optimal locations and configuration of the piezoelectric actuator patches for achieving the excitation of plate modes. Consequently, the results indicate that effective active damping of structural vibration of the cantilever plate can be achieved by proper positioning of the piezoelectric actuator patches.

Abstract: In this paper, performance of a 16 link snake robot in serpentine locomotion is investigated. Key kinematics and dynamics parameters are identified. The aim of this paper is to minimize average power consumption per unit distance traveled. Dynamic and kinematics equations of snake robot are used to perform simulation and obtain results. Key kinematics parameters are identified. Taguchi method is utilized and orthogonal array table is constructed. ANOVA technique is used to analyze the statistical significance of kinematic and dynamic parameters. Taguchi method is used to determine optimum parameter settings effecting performance of snake robot. Finally, the snake robot is modeled in WEBOTS software and forward motion is obtained.

Abstract: — Dimensional changes because of shrinkage is one of the most important problems in production of plastic part using injection molding. In this study, effect of injection molding parameters on the shrinkage in polypropylene (PP) and polystyrene (PS) has been investigated. The relationship between input and output of the process is investigated using regression analysis and ANOVA method. To do this, existing data is used. The selected input parameters are melting temperature, injection pressure, packing pressure and packing time. Effect of these parameters on the shrinkage of above mentioned materials is studied using mathematical modeling. For modeling the process, different types of regression equations including linear polynomial, Quadratic polynomial and logarithmic function, are used to interpolate experiment data. Next, using step backward elimination and 95% confidence level, insignificant parameters are eliminated from model. To check validity of the PP model, correlation coefficient of each model is calculated and the best model is selected. The same procedure is repeated for the PS model. Finally, optimum levels of the input parameters that minimize shrinkage, for both materials are determined. Simulated Annealing (SA) algorithm is applied on the developed mathematical models. The optimization results show that the proposed models and algorithm are effective in solving the mentioned problems.

Abstract: The rapid development of manufacturing industry making the pursuit of equipment performance increasingly demanding. Proceeded from design, considering testing and diagnosis problems from whole system and life cycle is an effective way to avoid major accidents and reduce the cost of maintenance, therefore, testability is widespread concerned. In this paper, taken marine diesel engine as research object, analyzed its necessity and feasibility of design for testability (DFT), through fully study of marine diesel engine’s testability characteristics, introduced multi-signal model to analysis marine diesel engine’s lubrication system testability, then advanced improvements for its testability, it can detect and isolate all faults of lubrication system, which provided a reference guide to marine diesel engine’s manufacturing.

Abstract: The reliability of the pneumatic cylinder was investigated by routine life test. The results show that the failures of the pneumatic cylinder can be described as a Weibull distribution and fatigue fracture of the aluminum end cap and the head of install bolt is the major failure for the pneumatic cylinder. The pneumatic cylinder life distribution parameters were estimated by the median rank method in combination with maximum likelihood method. The distribution model for the reliability of the pneumatic cylinder was also proposed here.

Abstract: Cooling system is a subsystem of a power plan that has an indispensable effect on efficiency of power plant. Air Cooled Condenser (ACC) system as a cooling system, is usually used in many power plants. Steam duct as a part of ACC conveys the steam flow with high velocity form steam turbine exhaust to head of tube bundle which is located at height of 25 to 30 meters. In this paper, pressure drop in steam duct is calculated using computational fluid dynamic method. Then, in order decrease pressure drop and consequently increase ACC efficiency, steam duct configuration is modified. The steam flow is modeled as an incompressible, turbulent and single phase flow. The solution strategy is based on SIMPLE and Segregated Implicit algorithm and the k-ε RNG model for turbulence are employed. The second order upwind differencing scheme are applied to discrete governing equations. Numerical results confirm reducing of total pressure drop in modified diffuser comparing with primary geometry.

Abstract: This paper describes hybrid multivariate methods: Fisher’s Discriminant Analysis and Principal Component Analysis improved by Genetic Algorithm. These methods are good techniques that have been used to detect faults during the operation of industrial processes. In this study, score and residual space of modified PCA and modified FDA are applied to the Tennessee Eastman Process simulator and show that modified PCA and modified FDA are more proficient than PCA and FDA for detecting faults.

Abstract: Choosing reaction time as dependent variable, the paper discussed the effects of object independent vibration on visual identification efficiency, which was under different vibration frequency, amplitude, direction and the position of target gap. The major experiment results indicated that the reaction time increase exponentially with the increasing of vibration frequency and amplitude within a certain range. This will provide a scientific basis for design optimization and vibration control of human-machine system.