Journal of Simulation and Analysis of Novel Technologies in Mechanical Engineering
Volume:8 Issue: 3, 2016

Object manipulation techniques in robotics can be categorized in two major groups including manipulation with and without grasp. The aim of this paper is to develop an object manipulation method where in addition to being grasp-less, the manipulation task is done in a passive approach. In this method, linear and angular positions of the object are changed and its manipulation path is controlled. The manipulation path is a screwed track with constant radius and incline. As there is no actuator and active controller in the mechanism, the system requires a kind of mechanical intelligence to navigate the object from initial to goal configuration. This intelligence is achieved by geometry of the object and dynamical and kinematical characteristics if the object and the track. A general set up for the components of the system is considered to satisfy the required conditions. Then after kinematical analysis, detailed dimensions and geometry of the mechanism is obtained. M.SC-ADAMS is exploited to simulate the proposed mechanism

Sprayers are important tools in agriculture that usually moved on the field by tractor. Sprayers should distribute the constant rate of chemicals during various conditions encountered in the field. Unwanted vibrations of sprayer boom cause redaction of its life time and over doses and under doses of chemical sprayed on the field. Therefore, in this study a model of suspension system for rotational vibrations of sprayer boom is proposed using horizontal and vertical elements of spring and damper. Then, the state space of the dynamical system is derived. In this state space, absolute rotation of the frame connected to the tractor around the horizontal axis (tractor roll) is input and absolute rotation of the sprayer boom around the horizontal axis is output. Also, the optimal gain matrix is designed for the state-space of system using linear quadratic regulator (LQR). Finally, impulse, step and ramp responses of sprayer boom are calculated and compared to impulse, step and ramp responses of system without controller. The results show that the designed controller significantly reduces rotational vibration of sprayer boom and improves the performance of sprayer.

Impact is one of very important subjects which always have been considered in mechanical science. Nature of impact is such that which makes its control a hard task. Therefore it is required to present the transfer of impact to other vulnerable part of a structure, when it is necessary, one of the best method of absorbing energy of impact, is by using Thin-walled tubes these tubes collapses under impact and with absorption of energy, it prevents the damage to other parts. Purpose of recent study is to survey the deformation and energy absorption of tubes with different type of cross section (rectangular, circle, square, hexagonal) and with similar volumes, height, mean cross section, and material under three different loading with different indenter. Lateral loading of tubes are quasi-static type and beside as numerical analysis, also experimental experiences has been performed to evaluate the accuracy of the results. Results from the surveys is indicates that in a same conditions which mentioned above, samples with square cross section, absorb more energy compare to another cross section.

Among various dissipating mechanisms, the viscoelastic effect of rubber material on creation of rolling resistance is responsible for 10-33% dissipation of supplied power at the tire/road interaction surface. So, evaluating this kind of loss is very essential in any analysis concerned with improving the fuel consumption of vehicles and resultantly energy savage. Hysteretic loss is a fraction of stored strain energy of tire which is dissipated during the rotational motion. In all related references and published articles, the hysteretic loss per revolution of tire is commonly considered as the rolling resistance. However, a reasonable approximation of stresses and strains time histories is very crucial for evaluating the amount of hysteretic loss. Based on the results of 3D static contact analysis, an efficient in-house program coded in Matlab is used for estimating the time variation of stress-strain cycles at different points of a rolling tire. Half the difference between maximum and minimum principal values of six stress and strain components can be used for evaluating the hysteretic loss during one revolution of a rolling tire. The results closely match the related experimental and numerical investigations.

Due to their light weights and high load carrying capacities, composite structures are widely used in various industrial applications especially in aerospace industry. Stiffening ribs are the main features of lattice type composite structures. Strength to weight ratio is known to be as one of the most critical design parameter in these structures. In this study, the effect of some parameters such as the physical characteristics of the material, shell thickness, angle, thickness and number of ribs on distribution of stresses and buckling loads of shell are investigated. For this purpose, 3D finite element analysis using ANSYS software explicitly was done and then compared with experimental test results. Increasing the thickness of the outer shell causes the structural strength will rise to 50 percent. The next effective parameter is reduction of rib angle which provides an increase of 30 percent in specific load. Although Stiffenerrs (ribs) have a major role in load carrying, but increasing the rib number causes the structural weight rises, thus compared with the two previous parameters do not have a significant effect on the strength of structures.

Vibration of double-graphene sheet-system is considered in this study. Graphene sheets are coupled by Pasternak elastic medium. Classic and Mindlin plate theories are utilized for modeling the coupled system. Upper sheet carries a moving mass. Governing equations are derived using energy method and Hamilton’s principle considering surface stress effects and nonlocal parameter. Using Galerkin method, figures of frequency versus nonlocal parameter are drawn and the effects of different parameters such as moving mass, surface effects and etc. are discussed. Results show considering surface effects, the frequency of coupled system increases. Also heavier mass and farther mass away from supports will result in lower frequencies.