International Journal of Modern Manufacturing Technologies
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Published By Asociatia Profesionala In Tehnologii Moderne De Fabricatie

2067-3604, 2067-3604

2021 ◽  
Vol 13 (3) ◽  
pp. 105-110
Author(s):  
Małgorzata Olender-Skóra ◽  
◽  
Wacław Banaś ◽  
Aleksander Gwiazda ◽  
◽  
...  

3D printing is a one of a new solution of manufacturing methods. This is caused by the ability of print a small part in a short time (rapid prototyping), but also because of the available materials. This is important because by using 3D printing, a specialized element is made for a specific apply. Compared with traditional production methods, such as turning and milling, 3D printing gives a wider possibility of making specific product patterns, thanks to which this method gained support and became a competitive one. Hence, the designing and manufacturing process based on it is more and more often referred as the “design-driven manufacturing”. This method gives the possibility of making personalized elements or a larger number of product variants, but also gives the possibility of manufacturing complete elements in one run. The article describes the possibilities of using 3D printing in the production of unusual elements in a uncertain situations.


2021 ◽  
Vol 13 (3) ◽  
pp. 66-71
Author(s):  
Adrian Ioana ◽  
◽  
Monica Iorga (Craciunica) ◽  
Florin-Stefan Petcu ◽  
Dumitru Deonise ◽  
...  

The article has as a starting point the presentation and analysis of the advantages of spatial organization of enterprises, as a management method. Thus, we analyze: creating the optimal conditions for the rhythmic realization of the production process; ensuring greater flexibility in the use of means of production; the possibility of carrying out a maintenance and repair activity of the equipment without disturbing the technological production process; ensuring an efficient management of the production unit. We also analyze, critically and comparatively, the disadvantages of spatial organization, such as: the need for a high qualification of workers; the need for a very high volume of transport and handling; technical quality control is much more complex in the conditions of a diversified production; the production cycle of manufactured products is long.


2021 ◽  
Vol 13 (3) ◽  
pp. 117-124
Author(s):  
Himanshu V. Patel ◽  
◽  
Harshit K. Dave ◽  

The Liquid composite Molding (LCM) process, such as Vacuum Assisted Resin Transfer Molding (VARTM), offers a fast and high-quality production of composites laminates. In the VARTM process, the simulation tool is found beneficial to predict and solve composite manufacturing issues. The part quality is dependent on the resin mold filling stage in the VARTM process. The infiltration of resin into a porous fibrous medium is taken place during the resin mold filling stage. The permeability has a crucial role during the resin mold filling stage. In this study, simulation of resin infusion through multiple injection gates is discussed. The various infusion schemes are simulated to identify defect-free composite manufacturing. The simulation approach is applied to five different stacking sequences of reinforcements. In this transient simulation study, permeability and resin viscosity is essential inputs for the resin flow. The simulation approach found that a gating scheme plays a vital role in mold filling time and defect-free composite fabrication. It is found that the line gating system can be useful for fast mold filling over the point gating system.


2021 ◽  
Vol 13 (3) ◽  
pp. 164-170
Author(s):  
Sergiu Spinu ◽  
◽  

Various biomedical components, such as dental crowns and hip prostheses, data processing devices, and other numerous mechanical components that transmit load through a mechanical contact, may benefit from a tri-layer design. The coating may be optimized for wear protection and corrosion prevention, whereas the intermediate layer provides increased adhesion between the outer layer and the substrate, and confines the crack propagation. The solution to the contact problem involving tri-layered materials can be pursued numerically with the finite element or the boundary element methods, but semi-analytical techniques benefitting from the efficiency of the fast Fourier transform (FFT) technique have also been successfully applied. At the heart of the FFT-assisted approach lie the frequency response functions (FRFs), which are analytical solutions for fundamental problems of elasticity such as the Boussinesq and Cerruti problems, but expressed in the frequency domain. Considering recent efforts and results in application of FFT to convolution calculations in contact problems, the displacement arising in a tri-layer configuration is computed in the frequency domain, and the contact problem is subsequently solved in the space domain using a state-of-the-art algorithm based on the conjugate gradient method. The method relies on the FRFs derived in the literature for tri-layered materials, and the efficiency and accuracy of computations in the frequency domain is assured by using the Discrete Convolution Fast Fourier Technique (DCFFT) with influence coefficients derived from the FRFs. The computer program reproduces well-known results for bi-layered materials. Numerical simulations are performed for various configurations in which the elastic properties of the layers, as well as the frictional coefficient, are varied. By using the newly advanced simulation technique, design recommendations may be advanced for the optimal configuration of tri-layered materials under contact load.


2021 ◽  
Vol 13 (3) ◽  
pp. 22-28
Author(s):  
Delia Cerlinca ◽  
◽  
Sergiu Spinu ◽  
◽  

Machined surfaces can be described by heights and wavelengths of the surface asperities that show a statistical variation. Considering that a regular wavy surface with a sinusoidal profile is the crudest model for a rough surface, studying the contact of regular wavy surfaces is a good approximation for the contact of nominally flat surfaces. Such contact problems exhibit periodicity that can be simulated with the aid of computational techniques derived for contact mechanics in the frequency domain. The displacement calculation, which is a necessary step in the resolution of the contact problem, is mathematically a convolution product that can be calculated in the frequency domain with increased computational efficiency. The displacement induced by a unit surface load can be expressed in the frequency domain by the frequency response functions, which are counterparts of the space domain solutions to half-space fundamental problems such as the Boussinesq problem. The displacement induced by a periodic pressure distribution can be computed by executing the convolution product between the frequency response function and pressure on a single period. It should be noted that the convolution calculation in the spectral domain implies that the contributions of all neighbouring pressure periods are accounted for. The need to treat numerically only a single period results in remarkable computational efficiency, allowing for high density meshes that can capture the essential features of any textured real surface. The displacement calculation promotes the solution of the contact problem by an iterative approach. The advanced method is benchmarked against existing analytical solutions for the 3D contact of surfaces possessing two-dimensional waviness. This essentially deterministic model, supported by a direct numerical solution that can be obtained for samples of real rough surfaces, presents itself as a worthy alternative to the existing statistical models for rough contact interaction.


2021 ◽  
Vol 13 (3) ◽  
pp. 14-21
Author(s):  
Yurii Buriennikov ◽  
◽  
Leonid Kozlov ◽  
Oana Rusu ◽  
Viktor Matviichuk ◽  
...  

Mobile machine hydraulic circuits tend to adopt electrohydraulics. Such hydraulic circuits are based on controlled pumps, modulated hydraulics, sensors and controllers. This allows adapting the hydraulic circuit operating modes to the changes of external conditions of the machine operation. Application of hydraulic circuits with electrohydraulics in mobile machines allows to use mobile machines efficiently with a high number of removable endangers, increases their performance and improves the quality of performed works. The authors propose an adaptive hydraulic circuit for a mobile machine. The operation process in the adaptive hydraulic circuit in static and dynamic modes is determined by the interaction of the pump controller and pressure differential control valves. The hydraulic system operation stability, its fast response and readjustment are determined by the controller parameters. It has been revealed that the main parameters affecting the dynamic characteristics of the hydraulic system are: throttle area and coefficient of amplifying the pump controller orifice, dampener area and coefficient of amplifying the pressure differential control valve orifice. These parameters affect the stability, controlling and readjustment time in the hydraulic circuit differently. A functional including the values of controlling time , σ controlling and losses in the pump controller was used as an optimization criterion. The optimization has been made according to the developed mathematical model applying the method developed by I. Sobol and R. Statnikov. During the optimization each controller parameter changed on 3 levels. 81 tests were made and the best combination of controller parameters for the optimization criterion was determined. The following hydraulic circuit operation values were reached under the optimal values of parameters = 1.0·10-6 m2, = 1.0·10-3 m, = 1.2·10-6 m2, = 10·10-3 m: = 1.1 с, σ = 32 %, = 0.82 kW that comply with the requirements towards hydraulic circuits of mobile machines.


2021 ◽  
Vol 13 (3) ◽  
pp. 37-44
Author(s):  
Dumitru Deleanu ◽  
◽  
Constantin Louis Dumitrache ◽  

Parametric roll on ships is an auto-parametric resonance phenomenon whose onset causes a sudden rise in roll oscillations leading to dangerous situations for the ship, the cargo and the crew. In the paper, we have numerically investigated the effect of modifying the heading angle on the roll amplitudes. We followed three strategies. In the first, we allowed the heading angle to decrease with a constant angular acceleration so that the encounter frequency has left the dangerous region of the resonance. However, this option involves changing the course of the ship in the long run, which is of course a shortcoming. In the second strategy, we changed the heading angle up and down around an average value that generates large roll amplitudes, by using different periodic sinusoidal or triangular profiles. The beneficial effect of this action is to keep the course, even if at the cost of a momentary delay. We noticed that both control techniques listed above generally managed to significantly reduce the roll amplitudes if certain thresholds have been exceeded. As a last idea for decreasing the parametric roll amplitudes, we used the combined effect of ship forward speed and heading angle change.


2021 ◽  
Vol 13 (3) ◽  
pp. 59-65
Author(s):  
Daniela Ghelase ◽  
◽  
Luiza Daschievici ◽  

It is known that, from the point of view of the accuracy of a machine-tool, at its design, the dynamic behaviour of each element of the kinematic chains prevails. Worm-gear drives are widely used in the different machine-tools and robots. Therefore, it is important that during meshing, as far as possible, there are no vibrations, shocks, power losses, noise and low durability. These requirements can be met if, for example, the gear ratio is constant during meshing, without transmission errors, which means that the worm-gear drive should have a high accuracy. The accuracy improvement of the worm-gear drive has long been a focus of attention for machine-tools designers. Thus, this paper presents various approaches to solving such problems, based on modelling and simulation, such as: estimating the load share of worm-gear drives and to calculate the instantaneous tooth meshing stiffness and loaded transmission errors; the desired worm-gear drive design configuration by altering the optimum set of worm-gear drive design parameters which are suitable for the required performance by associating it with SVM (Support Vector Machine); optimization approach for design of worm-gear drive based on Genetic Algorithm; design optimization of worm-gear drive with reduced power loss; etc. The optimization of the worm-gear design is an important problem for the research because the design variables are correlated to each other. An optimal design algorithm developed by the authors of this paper, for worm-gear drive, is also presented.


2021 ◽  
Vol 13 (3) ◽  
pp. 54-58
Author(s):  
Cornel Catalin Gavrila ◽  
◽  
Mihai Lates ◽  

The transversal mobile couplings are used in movement and torque transmission between two main shafts having parallel axis, with the possibility to undertake misalignments in the transversal plane. These shaft misalignments are usually named transversal movements. The paper presents, starting from some kinematic aspects regarding relative movements between the coupling parts, the kinematic equations useful in determining position of the intermediary elements, depending by the transversal misalignments. Following this, using the inside relative movement in rotation joints between parts and corresponding adequate materials, the friction coefficient is studied. The friction which appears in coupling’s rotation joints between the involved parts has an important influence on their dynamic behaviour, wear and lifetime. The most significant friction and also wear is given by the alternant rotation movements in joints between parts, at the ends of their angular stroke. Due to this, the study of the friction between some materials to be used in coupling manufacturing is required, but also difficult because of some particularities, as reduced rotation in joints, for reduced transversal misalignments between the main shafts. There are presented, in the paper final part, the results and conclusions.


2021 ◽  
Vol 13 (3) ◽  
pp. 29-36
Author(s):  
Bogdan Chirita ◽  
◽  
Catalin Tampu ◽  
Eugen Herghelegiu ◽  
Cosmin Grigoras ◽  
...  

In the pursuit to lighter, less consuming products, manufacturers, especially in aviation and automotive industries, are turning more and more to using lightweight alloys such as the ones based on magnesium. Higher requirements for increased productivity have led to concepts like high-speed machining (HSM), high feed machining (HFM) or high-efficiency machining. Tighter regulations concerning requiring for more environmentally friendly industrial processes led to limitations in the use of cooling liquids and a search for cooling methods with less impact (dry cutting, cryogenic cooling, near dry machining and others). Better machining processes can only be achieved by modelling and optimization. This paper briefly presents the results obtained by our research team concerning the modelling and optimization attempts on face milling of magnesium alloys using different methods: design of experiments (e.g. factorial design, response surface method), fuzzy logic or neural networks.


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