Applied Mechanics and Materials Vols. 809-810

Abstract: The use of high power railway vehicles requires enhanced control of wheel-rail adherence. When setting the train in motion, driving axles can exhibit torsional vibrations resulting in poor adherence and even axle damage. A significant number of railway authorities safety warnings and accident reports were issued related to the above phenomena. Adhesion saturation and negative slope are the characteristics which lead to self-sustained axial vibration. The aim of the present work is to prove the appropriateness of non-smooth models in the study of the axle torsional stick-slip vibrations which may occur when traction vehicles are set into motion. The model is simple, observes the main friction characteristics and provides the basis for efficient dynamics simulation. An experimental setup comprising a reduced scale wheel set is analyzed in order to validate the model proposed. The friction parameters are then identified using the proposed force-creepage relationship. Validation and verification is further carried out in frequency domain using both steady state and transient manoeuvres. Specific phenomena like discontinuities in the time-history friction force values occur. Validation and verification is carried out in frequency domain using both steady state and transient manoeuvres. From the comparison between the numerical and experimental results, it can be concluded that the setup is modeled accurately. Related problems may be solved using the present method, as it is pointed out in the article.

Abstract: The new perspectives with regard to early stage beginning vehicles development introduce the need for using driving simulators also. The objective of this study consists in investigating the stress behavior during driving simulator operation at maximum balance angle. The investigation during functioning of the mechanism (the stresses that occur in the system) starts with the static stress analysis, followed by the investigation for different angular positions from 0° to 10° that are mandatory. The analysis can predict the structural stress level that may become very high and generate deficiencies for the entire assembly while using different materials, including composite materials.

Abstract: The paper deals with the trajectories and lows of motion of a mechanism of type T-RRP that was buil by using the properties of Cardano circles. It has two slides moving along the axis of the system xOy. A second leading element and another T-RRP dyad were added to this mechanism, the resulting mechanism, of type T-RRP-R-RRP. The trajectories of three points of interest were determined, for various (linear) correlations between the movements of the leading elements. The obtained trajectories are similar, but not identical, to the loops of epicycloides, wrapping ellipses. The generated laws of movement were also determined, variable oscillations of the final slide being obtained.

Abstract: The aim of the article is to present an experimental research on the behavior of a pneumatic muscle actuated rehabilitation device for hip/knee affections, developed in a laboratory from Transylvania University of Brașov. The equipment has been tested and studied its response to some rehabilitation programs implemented: one for hip joint recovery and other for knee joint recovery. For the research was used WINPISA software with the two programs created by the researchers using NC commands. The knee rehabilitation program consists of slider displacement corresponding to a rotating angle of the knee of 75 degrees with a short temporization and the hip joint rehabilitation program consists of slider displacement corresponding to a rotating angle of the hip of 40 degrees. The results of experiments present the displacement of the slider which effectuates the rehabilitation moves, the velocity and acceleration in a proposed time.

Abstract: One way to increase the durability of the machine is active surface coatings using new technological processes such as thermal spray coatings, especially the plasma jet. Was made by coating nickel plating process of the plasma jet knife blade for removal of a group from the grower. In order to emphasize increasing the reliability of these knives by coating with nickel, they were mounted on a cultivator with a lot of knives witness, uncovered, and have been used extensively. Data on wear two groups of knives, coated with nickel and witness uncovered were recorded by photometric methods were processed and plotted statisitic. There was a significant decrease of 66.79% in average wear on the knife blades coated with nickel compared to the control, uncoated.

Abstract: The main purpose of this work is the presentation reverse task of mechanical systems including active elements. This reserve task is known as synthesis of mechanical system. In result of conducted synthesis was received structures and parameters of a discrete model meeting the defined requirements concerning the dynamic features of the system, in particular, the frequency spectrum. The presented approach i.e. a non-classical synthetic method applied in designing mechanical or mechatronical systems, one (as early as at the design and construction stage) may verify future systems. The aim of this paper is also analysis of obtained system to check relationship between basic system and active subsystem reduction vibrations. This active subsystem was consisted from electric elements. In this paper was used a non-classical method of polar graphs and their relationship with algebra of structural numbers. The use of such a method enables the analysis and synthesis of mechanical systems irrespective of the type and number of the elements of such a system. Active elements give better results (in compare with passive elements) in case of reduction of low frequency vibrations. Presented approach simplifies the process of selecting the dynamical parameters of systems in view of their dynamical characteristics. Thanks to the approach, introduced in this paper, can be conducted as early as during the designing of future functions of the system as well as during the construction of the system. Using method and obtained results can be value for designers of mechanical systems with elements reducing vibrations.

Abstract: In contextual evolution of the global economy and new technologies, quality, competitiveness, and cost engage companies to focus on continuous improvement and innovation. This approach is highly visible in the bearing industry, due to the emergence and improvement of existing and new types of bearings.The authors of the paper are engaged in a long-term research, which aims to improve the performance of heavy bearings, including identification of new constructive solution. The study is focused on the characteristics and constructive structure of the bearings cages in discussion.In this context, it is logical that the research focuses upon known bearings cages that are currently used [1], as well as unknown or unapplied constructive solutions which are the subject of patents.The critical analysis of various constructive cage solutions for bearings, intended or not for heavy bearings, is a valuable source of inspiration and information towards identification of constructive elements and characteristics useful to develop new technical solutions, by applying integrations, combinations, innovations and development processes [2].In the presented paper several patents are analyzed critically [3, 4, 5], in terms of constructive solutions, manufacturing complexity and presumptive operational energy consumption.

Abstract: The goal of this paper is to show that one can teach mechanical design making the students aware about the sustainability issues in mechanical engineering by incorporating obsolete parts. The example herein developed aims at finding viable design solutions by re-using end-of-life components to perform functions that are very similar to the ones for which they were initially designed, with only minor adjustments to make them suitable for their new purposes. A Savonius wind turbine was chosen for our exercise since it is easy to build and assemble, has low manufacturing costs and is appropriate for delivering a small amount of mechanical power.

Abstract: The Mohr-Coulomb failure theory presents the major drawback that can be applied only for plane state of stress. In this paper, we propose a modification of the Mohr-Coulomb theory that might eliminate this disadvantage. It is proposed to replace the three Mohr's circles for spatial state of stress with one “virtual circle” with diameter σ₁-σ₃±2ρ, concentric with the circle that has the diameter σ₁-σ₃. The triaxial state of stress and biaxial state of stress are considered to be equivalent dangerous.

Abstract: Since large hydraulic turbines already have very good energy performance, nowadays the challenge is to study, improve and construct low power turbines. One important step in the design of a new type of turbine is the experimental study based on adequate equipment. In real-life applications, the turbine is loaded by the electricity consumers. Usually experiments try to reply such conditions, when it is possible and by consequence an electrical loading system seems to be adequate for tests on pico turbines. The present paper focuses on the analysis of an electrical loading system and a mechanic loading system to be used for laboratory experiments on pico turbines. The quality of experiments and the extension of graph area recommend without doubt the mechanic loading system to be used for tests on new pico hydro turbines.