Applied Mechanics and Materials Vols. 110-116

Abstract: In this paper, for the first time, kinematics modelling of snake robot travelling with concertina locomotion is presented. Next a novel kinematics modelling method is presented which has an advantage of allowing natural snake like locomotion. During concertina motion, certain parts of the body contract, expand or do not change their shape. This results into having different body curves for different parts of a snake. To simulate this, first we introduce a mathematical equation, called dynamic function, in which by varying a certain function parameter, body curve during motion is realized. To obtain concertina gait, the snake body is divided into three different modules, head module, tail module and main body module that connects the head to the tail module. Each module forms a specific curve which can be modelled using the proposed dynamic function. At each moment during snake locomotion, the kinematics of different links can be derived by fitting links to the body curve. Finally concertina locomotion is simulated using Webots software. Results indicate concertina locomotion can be obtained. Furthermore, the proposed dynamic function requires relatively lower computation requirement. Therefore, adaption of body curve to other real snake like gaits as well as mixed type locomotion is made possible. This works represents a first approach to a simulation of a snake-like mechanism in order to get basic characteristics of such locomotion and to enable our future research.

Abstract: In this study, an analytical realization of end-milling system was introduced using recursive parametric modeling analysis. Also, the numerical mode analysis of end-milling system with different conditions was performed systematically. In this regard, a recursive least square (RLS) modeling algorithm and the natural mode for real part and imaginary one were discussed. This recursive approach (recursive least square method : RLSM) can be adopted for the on-line system identification and monitoring of an end-milling for this purpose. After experimental practice of the end-milling, the end-milling force was obtained and it was used for the calculation of FRF (Frequency response function) and mode analysis. Also the FRF was analyzed for the prediction of an end-milling system.

Abstract: Experimental and Theoretical studies on Pipeline all reveal important difficulties in data interpretation. This paper proposes 3-D dynamic finite element (3-DDFE) model based on the digital data set from the Natural Gas Pipeline section. The analysis was constructed to demonstrate the effectiveness of the 3-DDFE model as a potential Pipeline fracture investigatory technique. A three-dimensional mesh generation technique is developed in this paper. Problems arising due to interactive modeling are highlighted in relation to complex geometries. A preprocessor finite element grid generator. FEMGEN has been modified for mesh generation. The modified FEMGEN program is linked with a three dimensional finite element program. Pipe sample is chosen to describe the flexibility and capability of the modified FEMGEN program. The appendix I shows typical subroutines to support the computer program discussed in the paper. The 3-DDFE analysis of Natural Gas Pipeline would allow the assessment of the fractures effects of different impact conditions and enable the development of enhanced Pipeline fracture and protection criteria for Natural Gas Pipeline.

Abstract: This research is aimed to study the influence of the background color which affects efficiency in visual inspection. The visual search simulation program was set to test the search for the letters X and Y assigned to represent defects and mixed up with other background letters in 4 different colors: white, yellow, red and blue. The test were conducted with 48 samples who passed the selection standard by having normal eyesight, more than 50% accuracy in defect search while the average search time was less than 50%. The samples were separated into 4 groups for defect search with 4 colors background. The result was shown that the different background colors affect the average search time for defect search in each screen and the accuracy of the search for different defects. The white background provided the inspector the highest defect search efficiency with the level of statistical significance at .05.

Abstract: Modeling and analysis of inventory systems in reverse logistics is more complex than in forwards logistics, because in reverse logistics not only amount of demand is not clear, but also uncertainty of product return is appeared in the system. In this paper, an inventory system with the possibility of product return is modeled by means of simulation tools and then thermal equivalent of inventory model, using laws of heat transfer is developed. In order to provide the thermal equivalent, components of the inventory system are known and for each component the thermal equivalent is introduced and then sensitivity analysis is used to show the similar behavior of the two models. Hence, analyzing the thermal model can lead us to know the effect of different policies and parameters on inventory system performance. Thermal equivalent model presented in this paper is a strong base for inventory system analysis with more complex structures in future studies.

Abstract: The work aims at the optimization of the output feed rate of a Stationary Hook Hopper Feeder so that the best possible set of parameters affecting it can be selected to get the desired output. For this purpose the effect of various parameters on the feeder output is studied. To facilitate the study and detailed analysis, a statistical model is constructed which is used to predict and optimize the performance of the system. Efficient feed rate optimization determines the input variable settings to adjust the feed rate of the feeder according to the consumption of the parts in the next phase of production. The Stationary Hook Hopper Feeder, whose performance is to be studied, consists of a rotating circular plate and a guiding hook fixed at the centre and running up to the periphery of the plate. As the plate rotates, the parts follow the trajectory of the hook, orient themselves and then eventually are delivered through the delivery chute, tangentially to the plate. The factors influencing the feeder’s performance include the speed of rotation of the disc, the population of the parts in the hopper and the size of parts to be fed. A series of experiments is performed on the three process parameters to investigate their effect on the feed rate. To study the interaction among the factors a full 23 factorial experiment approach has been adopted using the two basic principles of experimental design-replication and randomization. The process model was formulated based on Analysis of variance (ANOVA) using Minitab® statistical package. The outcome is represented graphically and in the form of empirical model which defines the performance characteristics of the Stationary Hook Hopper Feeder.

Abstract: This paper presents the effect of centrifugal load in functionally graded hollow sphere. Analytical solution for stresses is determined using the direct method and the power series method. The material stiffness varies continuously across the thickness direction according to the power law functions of radial directions. Increasing the angular velocity results in increasing the all above quantities. With increasing the power law indices the radial displacement, the shear and circumferential stresses due to centrifugal load all are decreased and the radial stress due to centrifugal load increased.

Abstract: In this investigation the behavior of classical beams are simulated by a finite element formulation of the plasticity problem under two major kinematic hardening models. Complete formulation is presented for both load and deformation controlled cases. The proposed finite element formulation uses a variable stiffness matrix in each incremental step reflecting the yield surface movement. Examples are worked out for both the Ziegler-Prager and the Armstrong-Frederick theories, to show the stress-strain behavior under cyclic symmetric and asymmetric flexural loading. The results have been graphically illustrated in plots of the response curves and are compared to the published and experimental ones. It was observed that Ziegler-Prager theory for anisotropic cases with symmetric loading predicts a ratcheting response. While the results show agreement with published ones; it was also observed that the two theories do not show similar responses of reverse plasticity or ratcheting for Euler-Bernoulli beams in all the example cases.

Abstract: —This study is aimed at investigating the effects of cut-off ratio on the endoreversible Dual cycle performance with considerations of heat transfer loss and specific heat ratio. By using finite time thermodynamics theory, the relations between the net work output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between net work output and the thermal efficiency of the cycle, are derived. The results shows that if compression ratio is less than certain value, the net work output first decreases and then starts to increase as the cut-off ratio increases. While if compression ratio exceeds certain value, the increase of cut-off ratio make the net work output bigger. The results also shows that the maximum net work output and the optimal thermal efficiency corresponding to maximum net work output first increase and then start to decline as the cut-off ratio increases. The thermal efficiency and the working range of the cycle decrease when the cut-off ratio increased. The results obtained in this work can help us to understand how the cycle performance is influenced by the variation of the cut-off ratio, and they should be considered in practical cycle analysis.

Abstract: —The use of computer simulations for research in solid state physics has a long history. However, the current needs of industry in the new results require a current possibilities of computer technology make it possible to meet the challenges of Solid State Physics (SSP), in general, and crystallography in particular, to a whole new level. This article briefly describes the algorithms finding the orderly and the semi platonic and Archimedean figures and their complexes for the FCC and BCC structures, which contributes to the increased use of the computer modeling techniques in crystallography and SSP. (Abstract)