Advanced Materials Research Vol. 837

Abstract: Authors of this article had to build the Poka-Yoke [ unit for unusual geometry element, which require to use the inductive proximity switches with relatively small diameter and good sensing range. Industrial sensors suppliers putted on to the market new type of sensor named quasi flush or semi flush which fulfill the needs. An article shows the observed influence of the geometry of tested elements for the self-excitation phenomenon of quasi shielded inductive proximity switches. In consequence this phenomenon can cause in false quality control and passing the wrong elements through the Poka-Yoke unit.

Abstract: The clearances in the cinematic links appear due to the long functioning. In the paper we shall make a few considerations of geometric and mechanic type about the clearances in the linkages, linkages planes with rotation joint links. We shall elaborate methods to study the influence of the clearances. Consider a rotational kinematic coupling clearance, the clearance being defined by the distance, difference between the radius of the bearing and the radius of the journal. This relationship between elements is unilateral. Journal's behaviour inside the bearing can be highlighted the value normal reaction force. The journal can have the following phases, phase contact (when there is contact between the bearing and journal, the normal reaction force is zero) flight phase (no contact between end journal bearing at this stage is normal reaction force 0). It is considered the most dangerous phase, recovery phase of flight phase where the contact is restored. In this phase occurs shocks, shocks in turn produce vibration in the mechanism leading to the destruction of the system. The clearance size is directly proportional to magnitude impact and vibration level especially high. To be reduced or even eliminated these shocks, the paper presents a solution. Crank Mechanism with clearance, mechanism considered in this paper applies a force so that maintain contact between the bearing and journal, is considered the center of gravity of the connecting rod the forces and the moment. Based on the relations obtained from equation echililibru and vector equation of the contour goes to the numerical calculation for the engine element is inserted angle value (which defines the initial position of the mechanism), one deduces the angles, which define the position of the mechanism. Any would be their source of appearance, they usually produce unwished effects during the mechanisms functioning.

Abstract: The modeling phase of the computer system development is one of the most important elements affecting the final success of the created software. Structures developed at this stage are the basis for the design and implementation of computer program code. The paper presents the general model of static structures (main classes and their relationships) of production scheduling system supporting discrete and multiassortment production. In the description of the object-oriented model a graphical systems and specifications modeling language notation UML was used.

Abstract: The paper presents a solution useful for production scheduling in the context of the constraints arising from the complexity of the structures of realized processes and possibilities of use variants of their implementation. The proposed method uses both activity on arc and activity on node types of graph for describing multivariant processes. Representation of complex (composed) structures the AND-OR graphs are used that combines both conjunction and disjunction relations between nodes.

Abstract: Military vehicles have to travel, at least from time to time, on the national road network. Whenever that happens, the A military vehicle doesnt have to meet all the requirements of a civilian vehicle. Moreover, its lifecycle is much longer than a civilian vehicles one. This is the reason a military vehicle doesnt have to meet all the requirements that a civilian one has to. Nevertheless, traffic security asks for periodical checks of the braking, steering and other systems. In this respect, we have been contracted to develop a method to assess the braking systems parameter of a certain class of military vehicles. When an assessment is involved, we usually develop a basic mathematical model to be the basic feature for further investigation. Since for the old vehicles there are no database, we have created two models, one by numerical simulation and the other one by processing the experimental data. Should be mentioned that prior to use one of them for further analysis, we had to check for the models accuracy. Data have been achieved using a very up-to-date measuring system. Moreover, the data was subject to filtering procedures, taking into account the noises of the system and different other measuring errors. We have tested several vehicles that were in good technical condition. All in all, we have tried to create a reliable database that should stand back from a trusting point of view. The working characteristic features of a process can be synthetically expressed as a mathematical model. For the technical systems, this model can be obtained either based on the mathematical expressions that describe the working way of the systems components or on data-base grounds that have been previously achieved throughout experimental research. As far as the validation of the mathematical model is concerned, the modelling error should be kept under tight control. Therefore, the researcher has to permanently determine the difference between either the simulated and measured output parameters. Eventually, the validated mathematical model can be used to analyse the dynamic performances of the system or a proper way to improve them, as far as the actual evolution of the system is accurately enough described. Key words: vehicles, braking system, theoretical models, data based models, modelling error

Abstract: Military vehicles have to travel, at least from time to time, on the national road network. Whenever that happens, the legal requirements have to be met with respect to the systems that contribute to the traffic safety. One of these systems is the braking system. On the other hand, most of the military vehicles arent that up-to-date that the rest of the traffic partners are. Therefore, a military automotive engineer should have at hand a fast method to diagnose the technical status of the braking system even the checked vehicle is rather old. It would be also even better if the faulty party were accurately identified. The paper aims at providing a method helps the diagnosing teams to quickly compare the behaviour of an actual vehicle braking system status with a general model that had been acquired by tests. Since nobody provided that kind of information during 70s, our model derived from a large number of tests that have been performed on good technical condition vehicles. Key words: vehicle braking system, parametric models, data-based models.

Abstract: The paper is inspired by the computer based solutions developed over a period of almost 30 years. Thus, the original computer based solutions were developed for a wide range of problems: computer aided geometry for domain definition, data generators for finite element applications, output data file processors with visualization facilities, matrices defined as random access files with a wide range of subsequent applications in several disciplines and domains of science, FDM and FEM applications, customized solutions for heat transfer problems, computational fluid dynamics, experimental data reduction software applications, virtual reality facilities, semi-numeric modeling, computer based decisions. Dedicated solutions were developed for applied elasticity problems related to marine engineering problems as we as naval architecture problems: ship strength computing based on the method of initial parameters, geometrical characteristics of the cross sections, automatic calculus of the stresses of a general-shaped section and others. Most of these applications present the output data in a graphical way, in order to be more relevant for a structural analyst. Another objective was to offer not only values of different parameters, but laws of variation which may be used in other subsequent analytic studies. According to the complexity of the problem to be solved, these applications are in a range which starts at the data-crunching level up to complex and intelligent solutions, some of them being implemented in programs of tens of thousands of computer code lines. The paper presents the main features of each computer based solution, the connectivity with other solutions, the possibility to extend or adapt a given solution for a particular case study. Last but not least, there must be noticed that computer based solutions may be used in several directions of development: research, design and education..

Abstract: We use a model that is based on the cycle behavior inlet pressure variation. This analysis revealed the two main regimes of operation marine propulsion engines. Pressure drop in the suction process can be seen from two points of view: this pressure drop is an active dissipation and at the same time is a passive dissipation, contributing to the deterioration of cycle infrastructure. Interference of the two effects is reflected by the appearance of a ψ_a^opt=0,3...0,35, for which indicated power P_i becomes maximum in terms of given geometric and gazodynamic configurations. Respectively for a weighting of conductance gazodynamic imposed. When fuel flow is imposed, the analysis revealed that the share of shall be amended to variation of ψ_a, which involves the geometric and gazodynamic configuration variable. In this numerical analysis showed the existence of ψ_a^opt=0,1...0,15, for which indicated efficiency η_i is maximum. These findings are the basis for the complex optimization cycle program for four-stroke compression ignition engine.

Abstract: This paper presents a dynamic model of a human spine subjected to vertical vibrations. The lack of information regarding the negative load of the spine obstructed the development of an adequate dynamic model. The spine can be considered the resilient load-bearing member, and the mass of the upper body can be considered to be resting on top of the column. The described situation refers to the case in which the acceleration is applied in such a manner that the body is pushed down into the seat. The natural frequency, the dumping coefficient and also the critical levels of the force from the spinal direction are calculated. Fig. 1 presents a biomechanical model of the human body under vertical vibration. In all cases analyzed was the step type excitation. It was considered that the response to step type excitation has greater practical importance than the weight response because a large class of real signals that are external dynamic disturbances of the human body can be treated easily with the help of step-type function (Heaviside functions) or combinations thereof. Fig. 2 presents the force response for differents excitation times: (a) τ₁=0.01s; (b) τ₁=0.10s; (c) τ₁=1.00s. There is a transient increase of transient regime with increasing of model time constant value. Key words: biomechanical model, vertical vibrations, force response, transient regime.

Abstract: The tire driving force is the resultant of the elementary shear forces acting under the running gear contact area; while the tire ground contact area may be assumed to be constant, the sheared area increases with slip but is generally less then the tire-soil contact area. As a result, it may be considered that the tractive force is the result of the elementary forces acting along the portion of the contact area that participates in the shearing process. Starting from this idea, the paper tries to evaluate the shearing area using a traction model and experimental traction data. The traction model and the field tests referred to the driving tires of a 2WD Romanian U-650 tractor; the comparison between experimental data concerning the traction force and the results given by the traction model allowed evaluation of the shear area, using a Komandi type relationship, assuming that shear area is linked to the tire-ground contact area by the means of a wheel slip depending shape parameter D. The goodness-of-fit test applied to the original Komandi equation led to conclusion that this equation was not appropriate for the evaluation of the shear area, at least not for the test conditions. A much better goodness-of-fit between the measured traction forces and the ones predicted by the model was achieved when a modified Komandi type relation was used in order to describe the shape parameter. In this case, 77.8% of the of model predictions were within the 95% confidence interval of each corresponding experimental data point, compared to only 22.2% for the original Komandi equation. In terms of traction efficiency, the modified Komandi equation also led to a better fit between theoretical and experimental data.