Advanced Materials Research Vol. 837

Abstract: This paper is focused on a short term statistical analysis of the ship dynamic response in random head waves. The waves and the ship responses are considered to be homogenous random processes, being described by a short term Rayleigh first order probability density function. The waves are described in the frequency domain by ITTC power density spectrum function, with time domain formulation by Airy-Faltinsen and Longuet-Higgins models. The numerical analysis are carried out with own program codes package DYN, based on the hydroelasticity theory, with oscillation and vibration components, taking into account the ship speed influence on the dynamic response. The dynamic analysis is based on frequency domain procedures, for linear steady state response, and direct time domain integration procedures, for non-linear and transitory response, resulting power and amplitude density spectrum functions by Fast Fourier Transformation method. The numerical analyses are applied for an optimized 1100 TEU container ship structure, considering six different ship speeds, from 0 to 20 knots, for the full containers loading case. The short term statistical numerical results are pointing out that the ship speed has higher influence on the global vibrations response in compare to the oscillations response, with better accuracy on the non-linear model.

Abstract: A computer analysis has been developed for studying the energy and exergy performance of an direct-injection, naturally-aspirated diesel engine operating under transient load or speed conditions. The model is validated at steady-state operation and incorporates many novel features for simulating the transient response and analyzing all of the engine availability terms. The analysis reveals via multiple diagrams how the exergy properties of the diesel-engine subsystems vary according to the engine cycles for various speed and load changes. The diagrams also show the current-speed response. In addition, the effects of operating parameters such as the intensity of the applied change or heat loss to the walls are described from first-and second-law.

Abstract: The aim of this study is to present a mathematical model for the wave pressure in the Diesel injection system. The method of characteristics and the finite difference method have been used to solve the governing equations. Recent studies show that finite difference method is superior to the method of characteristics concerning computation time and nonlinearity. The injection process of a high-speed Diesel engine was studied in detail, using an original computer program developed in MATLAB. The governing equations are solved by the use of the finite difference method with central pattern at space coordinate in combination with the separation of flux vector. The fuel injection system is divided into pump, pipe and nozzle component to model the entire system. When forming equations of continuity and motion the following assumptions are considered: all the equations have 1D spatial resolution, temperature change due to pressure and time during the cycle is not considered, the vapors pressure of the fuel is small compared to the level of the pressure injection system, it is assumed that cavitation will not occur and elastic deformation in the injection system is not considered. The experiment is carried out to measure the fuel consumption, in-cylinder pressure, the fuel injection pipe pressure near the injection valve and needle lift for several regimes of the working domain of a Diesel engine. The experimental set-up includes a 4 stroke cycle 4 cylinder Diesel engine T684 made by Tractorul Brasov Romania. Simulations show satisfactory results, in principal for regime of low speed, for regime of high speed it is important to take into account cavitation and the elasticity of the component; but improvements are possible. Since the models are developed for certain conditions it was not expected to be valid for all working conditions. Targets for further research related to the present work is to improve the model attaching submodels for cavitation and elasticity of the component

Abstract: This paper presents an analysis for the longitudinal loop power flow of a 4x4 driven vehicle type taking into consideration the influence of the running track. The goal set up by this paper is to experimentally verify the existence of a certain dependency between the longitudinal loop power flow and the type of the running track the vehicle is moving on. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization. The loop power-flow is the result of the self-generated torque within the automobiles transmission, which is, at its turn, a consequence of cinematic misfits during the rolling process of the wheels. The mathematical model stated in this paper is confirmed by the means of multiple tests developed in real conditions. In order to carry out experimental research we used an all-driven, wheeled military APC, reconnaissance vehicle. The longitudinal power flow was determined with the vehicle moving in straight motion but having different rolling radius between the axles. The rolling radii of the wheels of the same axle were the same. The difference between the rolling radii was set to 0.03 m then to 0.05 m. The vehicle traveled on tarmac then on grass. The transmission of a vehicle that is susceptible in generating loop power-flow can be updated to decrease and technically eliminate it. Prior to such an update, a thorough analysis of the transmission working regimes should be performed, especially of those regimes that are most probable to generate loop power-flow. The paper presents the equipment used to perform the measurements and the way it was mounted on the vehicle. It also presents the values for the longitudinal power flow, recorded for both rolling radii differences. The results are presented in graphic display. Eventually, the paper presents the longitudinal power flow taking into account the difference between the rolling radii and its dependency towards the running tracks type. This study can be extended to all the 4WD automobiles, which have special traction control devices. The results obtained were processed in order to underline the power loops within the longitudinal transmission. Thus, important and interesting results could be drawn.

Abstract: Present paper focuses on the power circuits within planetary gearboxes, providing an original mathematical model. This model is an excellent instrument to analyze and determine the torque, angular speed, power factors, global gear ratios and efficiency distribution. The analysis itself has been developed for the second-gear, forward-motion of the gearbox. The analysis provides the mathematical model of the gearboxs way of working both in the static and dynamic modes. The method starts with issuing the equivalent graph (network structure) of the gearbox. Using this model, the gearbox is associated to a power driveline network that both transforms and guides the power flow to the final transmission of the vehicle. Using the network structural model, the gearbox turns into a general nodal diagram (graph). Our study concerned both the static and dynamic modes. It consists in a mathematical determination of the cinematic (angular speed) and dynamic (torque) factors that charge the gearboxs components. The mathematical model takes into account the power losses and the inertia occurring within the entire network and their influences upon the general power distribution. Using the model, we could get accurate results of the torque and power distribution. Moreover, the model provides the map of the power distribution when the gearbox works in its second gear, emphasizing the difference between the analysis performed for the two above mentioned working regimes (static and dynamic). The results can be further used as entry points for a much more complex mathematical model that describes the dynamic features of the vehicle.

Abstract: When the optimization of the manufacturing units is considered, the management usually focus on equipment costs and technology parameters. However, being the rising price of the energy, the energy efficiency has become a sensitive issue. Detailed energy related information should be collected in order to understand the consumption profile of each relevant machine/process and identify potential energy savings. Data gathering is time-consuming and very expensive since individual metering devices have to be used for each consumer. To overcome this inconvenient, several solution have been reported. All of them are making use of a single metering device (monitoring the overall energy consumption) and some Load Signature Identification algorithms, used to disaggregate the overall energy between the identified consumers. Their relatively low detection rate (about 80-90%) hindered the spread of LSI-based architectures. In this context, a new hybrid architecture is proposed in this paper, together with it's hybrid LSI algorithm. Several test performed in an electronic prototyping facility result in a detection rate close to 100%.

Abstract: This paper shows the main steps to design and realize an original sound module for a miniature model steam locomotive, which produces the adequate sounds and the characteristic steam puffing in synchronization with the wheels of the locomotive. This continues the previous work of the authors concerning the model railroading and the implications of nonconventional technologies in this field of activity.

Abstract: This paper represents the upgrade of our previous study in which we have presented a model for simulation of the drying kinetic and estimation of the effective moisture diffusivity of clay tiles using a constant diffusivity model. The main objective of this study is to determine the time - dependent effective moisture diffusivity of shrinkable clay tiles. Experimental investigations were carried out, on clay tiles, in a laboratory recirculation dryer in which drying parameters (humidity, temperature, and velocity) could be programmed, controlled and monitored during drying. Results presented in this study have shown that the proposed drying model describes and correlates accurately drying kinetics and gives a reliably estimation of the time - dependent effective moisture diffusivity.

Abstract: For over 20 years the term "three-dimensional scan" (3D) showed the world the possibilities of virtual design, simulation, or reverse engineering. 3D scanning is also known as 3D digitizing, the name coming from the fact that this is a process that uses a contact or non-contact digitizing probe to capture the objects form and recreate them in a virtual workspace through a very dense network of points (xyz) as a 3D graph representation. Until recently, digitization was limited by the speed of the scan head and the correct choice of the probing system, type of scanned piece and budget for the purchase or develops the scanning system. With the evolution of technology appeared a number of new techniques that tend to improve the properties of classical methods. Even if intended for copying or geometrical control, or rather virtual geometric modelling or product realization, there are two groups of technologies: with contact (classical methods with probes) or without contact (laser, optical or combination). Most automotive manufacturers currently use 3D scan metrology based on optical or laser systems to validate products quality. The pieces are initially measured by 3D scanning then they are compared with the designed model (CAD file) using a specialized software. By this comparison producer can interfere very quickly in the manufacturing process to remove the cause of defects, this technique being called Reverse Engineering (RE). There are many variables that affect accuracy of laser scanning and therefore the quality of information: reflectance of surface, colour object, recesses, openings narrow and sharp edges can be difficult to scan. This accuracy may vary from micron to millimetre and the acquisitions size from a few points to several thousand points per second. The overall accuracy of a 3D acquisition system depends above all on the sensors precision and on the acquisition device (acquisition with contact) or acquisition structure (acquisition without contact). In a perfect world or in an integrated production environment, 3D measuring systems should be able to measure all the necessary parameters in a single step without errors, and to render the results in the same way to the manufacturing networks equipped with computers, in formats useful for machines control and processes management.

Abstract: The paper concerns the problem of vibrations of beamlike system with variable cross section. The beam is treated as the movable system in transportation. The considered problem focuses on modelling and dynamic analysis of geometrically nonlinear beam systems in rotational motion within the context of damping. The major scientific purpose of the paper is to elaborate the mathematical model of such a system. Additionally, the main motion impact on the local vibrations due to the mathematical sense is determined. Moreover, it is necessary to remember the interactions between damping forces of the above mentioned mechanisms and the transportation effect. The main motion of the system is treated as transportation, whereas the vibrations of the system are treated as relative motion. There are two types of systems considered: simple vibrating longitudinally and simple vibrating transversally in the plane transportation. The most interesting elements of the analysis determine the dynamic state of the system and present the mutual coupling of vibration amplitudes, natural frequency, and transportation velocity. Analysis of systems moving with low velocities or vibrating only locally treats the systems as already known models in literature. There are many scientific articles where the forms of vibrations of these systems have been described. Due to the obtained results it will be possible to confront mathematical models with the known stationary and non-stationary systems. As regards complex and simple systems running at high speed, the resonance phenomenon can be noticed, and depending on the amplitude and frequency of vibrations, we consider the following cases: when the amplitude reaches theoretical infinity leading in practice to permanent damage of the mechanism or when the amplitude of vibration reaches a certain speed which can cause the decrease of durability of the whole system. The adequate practical usage of the above mentioned researches is justified by its wide range of applications. In the majority of technical cases, further analysis of the systems is considered to be far too much simplified when we ignore the elements of flexibility, damping, or the nonlinear geometry of the beam. All the mentioned influences are presented in the derived mathematical model in form of equations of motion.