Advanced Materials Research Vol. 1036

Abstract: Nowadays, thin-walled structures and different materials destined to absorb kinetic energy initiated a great interest among the researchers from the auto, naval, military industries even from the protection equipment production industry. The main role of these structures is to absorb and dissipate the kinetic energy so the maximum level of deceleration to be limited. Thus, the structures collapse through progressive buckling. The aim is to control this progressive buckling as efficient as possible through the collapse mode or the construction technique. This collapsing mode is well described and characterised by the international literature [.The plastic strain history of the components constituting the thin-walled structure is very important because each bending, stretching process or tensioning brings with it self-a series of transformations which compete to influence the dynamic response of this kind of structures [2].In this study, all the above presented aspects were taken into consideration in the analysis of the impact and energy absorption behaviour regarding thin-walled structures by using explicit nonlinear finite element code LS_Dyna V971. The thin-walled structures involved in this research are made from tailor welded blanks (TWB) and were subject of axial impact crashing tests. There were used three types of cross-section shapes: rectangular, pentagonal and hexagonal. In order to have a fare comparison study, all the studied structures had a 250mm cross-section perimeter and a height of 250mm, also. Each structure is constituted from four, five or six sheet metal parts bonded together.

Abstract: Together with the rapid development of high-speed railways, extensive research into railway technologies is compulsory, especially on the aspect of dynamic interactions between vehicle and railway line, in order to guarantee the operational security of vehicles at high speed and improve the passengers comfort. The increase in the severity of the dynamic interaction between wheel and rail arises from the increasing speed of trains. As a result, it is necessary to analyze for the characteristics of wheel-rail vibration. The curve is an important component of a railway line and is usually the very source of wheel-rail vibration, especially at the time when a vehicle rapidly passes through a railway line, and will seriously affect the safety and comfort of the vehicle. At present, the usual practice is to only take some limit values to design the vertical section of railway lines, such as the maximum slope and the minimum slope length, according to the grade of a certain right line. Moreover, the existing studies on the vertical curve focused more on the vertical section parameters without considering the influence of these parameters on the dynamic interaction between the vehicle and line. The aforementioned studies involve either static or quasi-static analysis. There is little literature available on using a systematic method based on dynamics to study wheel-rail vibration, and some related issues are mainly the assessment making for a certain line. Based on the multi-body dynamics and the existing achievements, this paper aims to systematically investigate the influence of vertical section parameters on the characteristics of wheel-rail vibration and discuss the relationship between the acting region of wheel-rail vibration and these parameters. Furthermore, the characteristics of wheel-rail vibration at different velocities are investigated. The evaluation of the vibrations behavior in a railway vehicle is one of the matters taken into consideration even from the design stage. The decrease of vibrations to an acceptable level in terms of running behavior, safety, passengers comfort and track fatigue is required by regulations at European level for vehicle homologation and their admission into traffic.The vibrations of railway vehicles are mainly produced by the interaction between the track and the rail. Regarding a track with irregularities or deviations from the ideal geometry it creates vibrations of vehicles, which are developed both vertically and horizontally. These two types of vibrations are decoupled, though, due to the construction symmetries (inertial, elastic, plastic, linear and geometric). As for the vertical vibrations, the bounce and pitch vibrations are the main reasons of the vehicles dynamic behavior. They can be studied on simple models, one or two degrees of freedom, based on the hypothesis of excitation symmetry, by considering only one mobile base as if the wheel-sets had identical motions . This is the reason why the results with these models can be overestimated.This paper presents the influence of vehicle wheel bases and of the steel tire in running conditions, depending on some geometric characteristics. The influence will be further reflected by the vehicles response to the crossing over the rolling track random irregularities and in the magnitude of the vertical accelerations. This is the reason why the complete model of a passenger vehicle has been accounted for, including the car body bending vibrations. The movement equations have been treated in an original manner and brought to a form that points out the symmetrical and anti-symmetrical decoupled movements of vehicle and their excitation modes.

Abstract: The automatic calculus in structural problems was a constant concern of the authors, several models of the phenomena being based on algorithmic generalizations of the analytical methods, where the solutions were either ‘exact’ or numerical. The calculus of the geometrical characteristics is important, being closely related to the calculus of the stresses, of the displacements, of the bucking and in other structural problems. This is why an algorithm designed to compute the geometrical characteristics, must take into account all these aspects. A first general and original solution was to create a Boole algebra based on simple shapes for whom there are direct calculus relations and to create complex geometries of the composite cross-sections using the addition and subtracting operations. This method offered an important advantage regarding the position of a very small set of points belonging to the section where the maximum stresses could be found. The weakness of the method consists of the very few ‘simple’ shapes which could be included in the library of the software application. A first direction to generalize the method would be the definition of new simple geometrical shapes, to be included in the general algorithm and in the library of the software application. Other shapes may be also included, such as the rolled steel girders: I-shaped beams, C-shaped beams and others. However, more general methods may be conceived, expressed as algorithm and implemented. The paper presents an original method to calculate the integrals, based on a mathematical generalization of the, so to-say, ‘classic’, theory. The method has some strong points, such as: it is very flexible regarding the definition of the domain; the effective calculus may be done either in a direct way or using the numerical methods; it can be easily adapted to employ approximative solutions in order to check the accuracy of the results using alternate approaches; the computer program may be conceived in several ways, fact which offers another aid in the generalisation of the method. The method was tested and the results are accurate. The next direction of generalisation regards the creation of an algorithm which identifies the most relevant locations of the points where the maximum stresses may be found and the areas where sudden variation of the stresses may occur. In this way, there may be calculated only small amount of relevant ad important data regarding the strength of the structure.

Abstract: The increasingly importance for the uses of the air lift pump in widespread list of fields (mining, nuclear industries, agricultural uses, petroleum industries...etc.) makes it very interested for the researchers to find tools to raise the performance outcome of such pumps. An air lift pump system was setup to study the effect of the suction pipe diameter and submergence ratio on the liquid (water) pumping rate. The system has a lift pipe of (0.021 m) diameter and (1.25 m) length. Five diameters for the suction pipe (0.021, 0.027, 0.033, 0.048 and 0.063 m) with a fixed length of (0.3 m), were tested for each of the submergence ratios (0.2, 0.3, 0.4, 0.5) respectively. Results indicate that the higher the diameter of suction pipe, the higher the pumping rate for a fixed submergence ratio. From another side, the higher the submergence ratio, the higher the pumping rate for a fixed suction pipe diameter. Also, under high submergence ratios, high pumping rates were achieved by the use of lower air flow rates compared with those used with lower submergence ratios. The experimental results show good compatibility with the model suggested by Stenning and Martin for the performance of an air lift pump.

Abstract: Work presents an analysis and computer aided simulation of one-dimensional vibrating system with advanced piezoelectric transducer used as vibration actuator. A Macro Fiber Composite (MFC) transducer is used in order to excite vibration of the system. The mechanical subsystem is a cantilever bending beam made of steel. The MFC transducer is bonded to the beams surface. Analytical calculations are based on an approximate Galerkin method. The computer aided simulation and analysis of the considered system was carried out using Siemens NX software.

Abstract: Industrial robots are used for many tasks, mainly for material handling, welding and cutting. Robots can be also equipped with other tools for example drill or mill cutter and used for machining. Compared to conventional machines, robots have some advantages, which are: large range, flexibility and speed. On the other hand the greater disadvantage is small stiffness of robotic arms. Also the precision of robot positioning is smaller than modern CNC machines. Nowadays small number of robots are used mainly for machining of soft materials, such as plastic, wood, foam and aluminium. We have also executed some experiments with robot machining including styrodur milling. This technique is similar to rapid prototyping technics. Obtained parts can be used as prototypes. Robots can be used also for machining of hard materials and steel, but that is related with greater cutting force. Thanks they flexibility robots can be used for tasks that are performed by hand by locksmiths. An example of deburring and chamfering of sharp edges were analysed. The burrs and sharp edges that remains after some machining operations must be removed. In most cases that is done by chamfering the edges with hand tools. That tasks requires skilled workers and is physically exhausting and therefore industrial robots can be used to perform that work. But the first problem is prediction of cutting force and selection of proper robot with adequate payload. A mechanistic model of cutting force during milling a chamfer on the edge is presented in the article. Obtained results are similar with other experimental results that are described in the analysed bibliography. Afterwards a methodology for robot selection is explained. Because robot manufacturers give only data for static payload of robot arm, there must be a way to take into account the dynamic cutting force. Some problems that are possible during robot machining are discussed, and some solution are proposed. Because milling force is not constant and still subsequently changes value and direction, it can be the source of vibration. Small stiffness of robot arm combined with vibrations can caused losing of robot position and improper surface after machining. Other problem can be robot programming for machining of curved surfaces in 3 dimensional space. There are same CAM system that can be used for that purpose. Results obtained with developed model can be used for design of robotic cell for chamfering and milling.   Normal 0 21 false false false PL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

Abstract: This paper presents an approach to the application of agent-based systems for robotic workcell integration. Agent-based systems constitute a relatively new approach for analyzing, designing as well as implementing applications to be used in distributed systems, which is multi-robot workcell described in the paper. This systems should provide coordinated actions of all cooperating agents in order to achieve a common task. In the work was assumed the independent and autonomous operation of each robot as an individual agent. The aim of the designed system was to maximize the number of tasks realized by robots while minimizing the incompatibility of different robots during their joint work. It is assumed the independent operation of each robot and at their highest efficiency and effectiveness. In the paper are presented steps required to reach this aim and the short descriptions of proposed algorithms.

Abstract: The paper deals with the analysis of a RPP sequential manipulator designed to be used for handling different loads, bringing them to a preset position. This manipulator is used to automating the store and transfer loads for improving working condition, avoid using human operations that require low-skills and reducing the risk of accidents. In the beginning, we performed a structural analysis of the manipulator. It has all the features of any industrial robots. Afterwards, we carried out a study of kinematics and dynamics for this RPP manipulator, using a simulation software package. The simulation results can be used for various purposes such as: trajectory calculation of characteristic point depending of variable couplings; determining whether to change the parameters of particular joint for achieving a certain trajectory of characteristic point; finding the force needed in joints to achieve a certain end-effectors trajectory; finding the kinematics of joint according to the driving force. This study is necessary to command and control system in order to obtain the desired motion. It also allows the choice of actuators of the manipulators. An experimental research was further conducted with the main goal to determine the motion law for the manipulator cinematic joints. We used Hottinger equipment consisting of transducers, amplifiers and a computer, using a parallel connection, data acquisition, type system. Eventually, with respect to the simulation and experimental research, we provide an algorithm for analyzing a sequential manipulator. It can be used to determine the forces that should act within the cinematic joints in order to get a certain trajectory of a characteristic point (that allows choosing the driving system during the design phase of manipulators or checking the driving system if the manipulator is already manufactured).

Abstract: The paper presents the conception of integration of a robot virtual model with its virtual control system. The system of connections between the virtual world and the control system of a virtual model, proposed in the work, should let for developing the technical approach allowing teaching the manual programming of robots. In the paper attempted to define particular subsystems included in the proposed system for teaching programming of robots. In the work it have been distinguished problems that should be solved in order to properly create the proposed virtual system, and namely problems related to the: creation of a robotic system model in CAD systems, including modelling of a robot and its technological equipment; modelling of functioning of a real system in the applications of the VR (Virtual Reality) class; creation of a robot control system basing on a high level programming language (control application); elaboration of a virtual robot control panel (hardware interface); determination of the appropriate stereoscopic projection system and creation of the interfaces between the particular subsystems.

Abstract: Mixed reality is a term which covers a wide range of computer and real world interaction. This name refers to the picture shown on the display device, which consists of real and virtual elements. These elements are mixed in some proportion, so we may distinguish between augmented reality (where the real world dominates) and augmented virtuality (where the virtual world dominates). In most of cases a flat (2D) live image is processed, which makes this technology available in smartphones, car navigation systems etc. In the engineers world the mixed reality is used mainly in simulators and trainers, but also as supporting technology during manufacturing, assembly or maintenance process. This paper discuss different approach: mixed reality as a tool supporting programming of the robot. The main goal was to reproduce a path given by operator in off-line programming software using the visual representation of a real object. The system should be regarded as experimental one, because of early stage of development. It allows defining the coordinates of discrete points or to discretize the path and save this data for further processing. The operator should care the rest of programming task, but the use of the robot is reduced to minimum at this stage. The major disadvantages of the mentioned method are problems with accuracy and the invariable orientation of the tool used by the robot during the process they may be eliminated by using better video equipment and the specialized image processing routine. This paper presents the main assumptions of the method along with a possible solution of the problem.