Applied Mechanics and Materials Vol. 657

Abstract: Industrial cleaning is a classic application of water jets technology. In the late 1950s, when reliable high pressure pumps were built, the usage of water jets spread widely in the field of pipes and sewerage cleaning. In our particular case, water jets with less than 340 bar pressure are being used. The experiment is the research method used in the study of the impact forces that occur in the sewerage cleaning head system. In order to measure the impact forces between the water jet and a flat and rigid surface, we designed and built a stand for generating pressure jets, as well as a device to measure the impact force. Using the impact forces measured were calculated the coefficients of discharge, speed and contraction of water jet at the outlet of nozzle.

Abstract: The problem approached in this paper refers to designing a device for wire electrical discharge machining (EDM) which can be used on a ram electrical discharge machine. Usually, wire electrical discharge machine is applied only on specialized electrical discharge machines. The device proposed in the paper will ensure widening the technological possibilities of the given ram EDM equipment. A principle schema of the device was established, after analyzing the main requirements specific to the device service. One took into consideration a possibility to rotate and fix the subassembly for guiding the wire electrode so that the active zone of the wire tool electrode has a horizontal, vertical or even inclined position. Another requirement was to ensure a way for achieving machining processes in cavities existing in workpieces of higher dimensions. Functioning of the designed device and strain resistance of some components were tested by using CATIA V5 software. Some optimization possibilities for this constructive solution of the device were identified.

Abstract: Compliance is one of the main requirements to be satisfied by a gripper system. The paper addresses this issue and proposes a compliant, pneumatic muscle actuated gripper system. Constructive and functional models of an innovative gripper system are presented, together with a discussion of its limits.

Abstract: Creating 3D models automatically from photographs is a relatively new technology. This sort of 3D scanning is based on the principles of photogrammetry, similar in methodology to panoramic photography; the photos are taken of one object and from different positions of camera in order to replicate the object. Paper approaches different typical anatomic surfaces by photogrammetric scanning and 3D reconstruction. Documented surfaces include anatomic surfaces like foot, upper body, head, and ear. The aim is to give users recommendations, which body part is suited best for this type of scanning, or even if a combination of photogrammetry and another 3D scanning technique is advisable. Comments like possible medical applications, quality of the results, required equipment and occurring problems are to be considered.

Abstract: Sound may be defined as any pressure variation (in air, water or other medium) that the human ear can detect. Just like dominoes, a wave motion is set off when an element sets the nearest particle of air into motion. This motion gradually spreads to adjacent air particles further away from the source. Depending on the medium, sound propagates at different speeds. In air, sound propagates at a speed of approximately 340 m/s. In liquids and solids, the propagation velocity is greater 1500 m/s in water and 5000 m/s in steel [2].

Abstract: This paper presents the final design of glass-reinforced polyester (GRP) blade for 10 kW wind turbine developed at the Technical University of Moldova by finite element (FE) analysis techniques. This design was reached through an iterative analysis process following a previous design. The objective of this research is to maximize structural robustness of composite blade while reducing its mass and cost. Design optimization of the composite wind turbine blade was performed by checking the static and dynamic behavior. The design variables considered are related to the composite material parameters: fiber direction, layups direction and blade shell thickness based on number of composite layers. The constraints are tip deformations, allowable stresses and resonant vibration of the blade. According to FE analysis results the optimized blade will be stiff enough in storm conditions, will operate out of dangerous resonance frequencies and will weigh approximatively 20% less.

Abstract: In this paper is presented a statistical method for calculating the establishment of tolerances of a chain of complex dimensions, method which is applied quickly and efficiently by a computer program. The question that arises is the influence of a reducer shaft axis non-parallelism that can lead to some shortcomings in its operation. These deficiencies are based on the size of deviation from parallelism of the axes of the two shafts. For their removal was necessary to study the chain of dimensions which was formed to mount the type of reducer 1400-30/7ERC. Using the data obtained in practice by running a computer program achieved CALTOL was determined statistical tolerance deviation from parallelism between the axis reducer shafts.

Abstract: The paper presents a new approach to the numerical solution of a particle in equilibrium lying on a circle and subjected to the action of a linear spring. The difficulties of solving such a problem and the Mathcad and Simulink based solutions are presented in [1, 2, 3]. The most important difficulties consist in symbolically solving a forth degree trigonometric equation or in solving a complicated trigonometric inequality. This is why a numerical solution is preferred. The use of the bond graph modelling method for solving this problem of equilibrium is presented in this paper. The bond-graph modelling method is designed only for dynamics and the paper presents the possibility of its adaptation for solving this problem of statics of a particle. This approach can be then applied to solve other problems of statics. From the bond graph model the equilibrium equation and the block diagram model can be obtained. The block diagram model is usually preferred in engineering and, for this reason, the block diagram model obtained from the bond-graph model is shown in the paper together with the numerical results obtained after performing the simulations. The results are compared with those previously obtained in [2, 3].

Abstract: Bearing condition monitoring confronts the most machine users. Diagnostic methods used to include bearing problems represent one of the most important challenges. The scuffing phenomenon initiation of the bearing elements produces an important increase in the vibration level and can be emphasized by the analysis of the bearing friction forces which are the most sensitive indicator of the bearing failure. Commonly used technique for damage detection is the vibration signature analysis that must be carefully utilized in conjunction with the friction torque monitoring through the strain gauges measurements. In order to detect the scuffing onset, the paper presents an experimental setup for the scuffing tests performed on a 7206 ball bearing. A virtual instrument monitoring the friction force respectively the braking torque was created. An accelerometer captures the signal from the bearing outer ring then it is processed using PCI-4451 National Instruments data acquisition board and LabVIEW soft.

Abstract: The paper focuses on the validation of the numerical simulations regarding the behavior of a railway vehicle while running on a track with irregularities. These simulations are developed from a complex vehicle track system that allows the evaluation of the dynamic behavior on a vertical direction of the railway vehicles in terms of running quality, vibration comfort and the fatigue stress on the track. The validation process consists in the comparison of the acceleration spectra derived from numerical simulations and those from the data recorded during the vehicle circulation on the running line. In this context, the frequency spectra of the measured acceleration are shown that they can be classified into two categories one is of the spectra similar in shape with the ones considered in the numerical simulations, used as a basis for the validation process and the other one includes the acceleration spectra that are sensibly different than the ones derived from the numerical simulations.