Advanced Materials Research Vol. 1036

Abstract: The paper presents an approach concerning the CMM design. The first stage of this research deals with the acquisition and the development of knowledge about the CMM design. The main mechanical design aspects to achieve a high positioning and measuring accuracy are presented and two main objectives are assigned: high repeatability (design for repeatability) and high predictability of the machine response to the main error sources (design for predictability). In the second stage of this research the dynamic errors states for this CMM design have been analyzed. In high-speed measuring processes dynamic errors will have a great influence on the accuracy. This study has been performed by using finite-element analysis (FEA) of the mechanical frame. The total deformation of the mechanical frame for different accelerations of the moving assemblies has been calculated. The major deflections at the probe position due to the accelerations are obtained by using FEA. These results give a prediction about the dynamic error of the CMM.

Abstract: The reduction or elimination of undesired vibration can be achieved by applying various methods. The most commonly applied methods are: passive, semi-active and active.This work presents methods of reduction of the vibration of mechanical systems by means of active elements as well as examples of implementation of reduction of vibration by means of electrical elements. This work also introduces a structural and parametric synthesis, which can be defined as the design of systems meeting specific requirements. These requirements refer to the frequency values of the systems vibration. The presented approach i.e. a non-classical synthetic method applied in designing mechanical systems, one (as early as at the design and construction stage) may verify future systems. As a result of the synthesis one can obtain the structure and parameters of the system of required properties. The synthesis may also be applied to modify the already existing systems in order to achieve a desired result.

Abstract: This paper presents an analysis that aims at identifying the interdependence between the wheels slip and the self-generated torque that occurs at the inter-axle level of a 4x4 automobiles driveline. We consider that this paper has a high degree of novelty since it succeeds in establishing causality relationships between different automotive typical parameters. Moreover, the paper provides the specific mathematical, theoretical equations as well as an example of a generalized mathematical model derived from time or frequency analysis.The theoretical mathematical elements consist of terms referring to the rigid wheels kinematics and specific working conditions of the vehicle when it runs with tire radii differences at the inter-axle level. To achieve the goal of our work we developed a large experimental research work that involved an extended instrumentation of an all-wheel driven military vehicle in such a manner that allowed getting information concerning different shafts torque and angular speed. The vehicle has transfer case, involving a longitudinal differential. The tests were developed with the locking device of the differential working in the engaged mode. Aiming at revealing the connection between the tire radii and the self-generated torque, we have subjected the vehicle to different tire radii running modes. The rolling radius of the wheels that were on the same axle was the same. The bigger the tire radii difference the bigger the self-generated torque; hence the interdependence started to reveal itself as far as the tire slip also followed the behavior of the self-generated torque. In order to determine the wheels slip we also measured the vehicles speed with a GPS. The results are graphically presented.Following the results of the data processing stage, we concluded that the interdependence between wheels slip and the self-generated torque exists and a relationship between these two phenomena can be mathematically expressed, using a generalized model. We consider that a kind of model like this proves its utility in simulating similar conjectures; thus, the experimental research effort can be significantly reduced either by lacking either in torque measuring or wheels slip measuring. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization.

Abstract: The paper presents a possible method to diagnose a mechanical fault of an automotive system. Starting from the point of view that every fault of a mechanical system should introduce an abnormal component within the signal that describes the time history of a mechanical parameter we tried to find a way to reveal it.We were performing some tests involving a military vehicle with respect to the performances of its braking system. The tests were aiming at identifying a way to bring up-to-date the old weapon system from the braking systems point of view. During these tests we observed some anomalies concerning the pressure evolution within the braking cylinders of the vehicle. Some unusual but also systematic noises occurred. As a main issue at this point, the source of the noise should have been identified and filtered if necessary. We had to decide whether the noisy component of the signal is just a noise that should be removed by filtering the signal or it is a physical component of the mechanical parameter itself (not noise but a useful information).These procedures take time and they also request accurate knowledge as well as fine expertise in automotive testing. Since our Dept. has a long and rich practice in this respect, we assumed to processing data and give them a thorough interpretation. So, the first thing we did was to perform a frequency analysis, using classical methods. Usually, a simple frequency analysis cant provide information about a time variation of the frequency spectra due to the Fourier Transforms behavior, since it freezes the signal in time. A much more accurate analysis is the time-frequency analysis. However, observing both the amplitude and power spectra can lead to a useful conclusion. We concluded that the noise we met within the signal is due to the brake drums loss of circular shape (they turned into an oval, the process being known as ovalization). Hence, we cant talk about a noise as it is usually defined.

Abstract: The analysis of literature and own research have showed that there are several important processes in metal pieces coated with plastic cover, which have significant influence on the strength of fatigue. Those processes are caused by generation of electricity in double layer (EDL), affecting the electrode potential shift in positive direction. The increased adhesion forces on the metal substrate is the another factor, which translates into increased strength of fatigue. An equally important issue that could have a significant impact on the growth of strength of fatigue is the penetration of hydrogen into the metal. This phenomenon has been known for a long time, but the mechanism associated with this issue still represents an unexplored area. The aim of this paper is to introduce this mechanism basing mainly on a theoretical analysis of this phenomenon and some selected own research.

Abstract: The paper presents the method of designing equipment for protection the hydraulic system, and particularly hydraulic machines, against dynamic loads. The example of such machine is a powered mining support. A support must work in the conditions related with rock crumps what causes large and quick energy releasing. The designing process bases on the integrated approach what let taking into consideration all needed elements of this process [1,. Each of the elements of the design process could be an independent design agent which could find its solution both in CAD technique and other modeling tools [3,4]. Moreover in the paper is presented the results of computer analysis of the presented solution. This design solution bases on the application, in the protected hydraulic system, two complementary valves: the quick-release valve and the large-caliber one. Analysis of this valve system allow to state that this technical solution should protect a hydraulic system against dynamic loads of any energy.

Abstract: One of the most important aspects of machine designing is to balance between the economic requirements and the safety ones. Taking into account these requirements it was conducted the design work to elaborate the new concept of the mining roof support that fulfil them. The mining roof support is a mining equipment that has the most influence on the safety of work in deep coal mines and on the productivity of deep mines. Moreover the hydraulic roof support generally accounts for over 50% of the total value of a coal mining and excavating system. It is consider not only with the complexity of the roof support but also with the accepted direction of the development of mining supports. Generally designers elaborate heavier constructions with prof of larger diameters and loads. In this way the support system must be prepare not only to withdraw the rock mass forces but also the forces generated by its hydraulic system. These prerequisites underlie the new project of a roof support. This project bases also on many Polish patents concerning the mechanical devices and hydraulic equipment of a mining roof support. The main idea of the work was to elaborate the scheme of a support that will be compatible with the system of loads generating by the rock mass and by the conditions of work in a deep mine. As a result it was proposed the concept of a hydraulic roof support equipped with four props that work only in a vertical position. To realize that task it was proposed the special designed strait-line mechanism protected by Polish patent. This mechanism is supported by gas springs with low resistance. These springs help to eliminate horizontal forces loaded the construction. It has been also designed special flexible roof part (also patented) that allows to eliminate the horizontal component of roof rock loads. The hydraulic system is equipped with gas dampers that compensate dynamic loads during bumps in longwalls. The design of the dampers is also patented. In the result of design process the new concept of the roof support have been elaborated. One prototype has been manufactured. According to analysis it is about half the weight of standard roof support and the cost of it reaches the 50% of a standard support. It should be the optimal proposal for the European mining industry.

Abstract: The railway transportation system is nowadays one of the most important systems for land transport because its increased load carrying capacity, high speed, low costs, connectivity and ecologic features. As a result, the railways are subjected to additional loads which produce a higher level of strains and stresses. The rolling contact of a wheel on a rail is the basis of many rail-wheel related problems including the rail corrugation, wear, plastic deformation, rotating interaction fatigue, thermo-elastic-plastic behavior in contact, fracture, creep, and vehicle dynamics vibration. Therefore, this topic became the research subject for many researchers worldwide. Practical experience shows that the stress distribution is an important factor at the rail-wheel contact interfaces, that is, two materials in contact at rolling interfaces which are highly influenced by the geometry of the contacting surfaces, material constants, loads and boundary conditions. Three different procedures have conventionally been utilized to inspect rail-wheel contacts including Hertzs theory and Kalkers analytical method. The calculation of these stresses becomes much more complicated in three dimensional real size geometries. For this reason, many scientists have simplified the problem mainly by means of theoretical or numerical approaches based on the Hertzs theory, which can be considered the starting point of all subsequent researches. Both static and dynamic contact stresses have been carefully examined. Accurate theories, as well as computer software have been developed to evaluate all the parameters which influence the rail-wheel interaction. The analytical equations were employed to calculate the Hertzian stresses using the Octave software. For these elements, the simplifying hypothesis was to consider only the elastic properties of materials and, consequently, to neglect the elastic-plastic characteristics. Besides, many models generally neglected the friction coefficient between the rail and wheel, which is one of the most critical factors in determining the precise amount of stresses and distribution of contact pressure in rail-wheel contact area. On the other hand, some practical methods have also been introduced to solve traditional problems related to rail-wheel interaction. Other original contribution of this research is to create a precise finite element model of a 3D rail-wheel, axle and pads in order to evaluate stresses, strains, and contact forces in this complex interaction system. However, unlike many previous works, this study focuses on the real conditions of the problem including exact boundary and loading conditions, using real-size complete model of various components with precise shapes.

Abstract: This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose is to establish mathematical description of vehicle dynamics based on statistically sufficient experimental data and using statistical instruments. The results are analytical expressions and graphical representations that can be used in situations other than those the data were obtained. Experimental research program objective was to obtain a variety of data to define the dynamics of a vehicle. It involved a large number of tests, more than 100, on different runways, pavement, mosaic tiles or asphalt. They were performed in various weather conditions, sunny and warm weather or rain or sleet and snow. The driving style varied between normal and sport ones. The experimental data were used in obtaining mathematical models that define certain dependency between dynamic parameters. There were issued multiple linear regressions with one resulting parameter. If we analyzed the models we issued we notice that the more factorial parameters are involved, the higher the accuracy of the model we get.

Abstract: The ballistic simulation attempted in this work is among the most difficult as both the projectile and the target experience significant deformations. Traditionally these simulations have been performed using a Lagrangian approach, i.e. a deformable mesh with large mesh deformations. There are three often used techniques when studying ballistic problems with the Lagrangian method: remeshing (generally not available for 3D hexahedra meshes), the 'pilot hole' technique and material erosion. Because these techniques imply element removal, in order to allow the calculation to continue, the Lagrangian method lacks a physical basis. Moreover, no general guidance exists for selecting one of the three techniques mentioned before. The Smoothed Particle Hydrodynamic method as implemented in the commercial code LS-DYNA has been used in this paper to solve the problem of the impact between different caliber projectiles and various types of metal targets. The results are compared to those produced by dynamic analysis using conventional finite element methods with material erosion as implemented in LS-DYNA.