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This issue of the RECENT journal was edited with the support of: CONTENTS
Avoiding Occupational Diseases in Industry by Adapting the Training Methods to the New Technologieshttps://doi.org/10.31926/RECENT.2020.61.056 Abstract The most common occupational diseases in the industry are mainly due to the non-compliance with the employer's obligation to provide appropriate training in the workplace. This is often performed only by signing training forms only formally. With this fact in mind, we analyze in this paper the occupational diseases in industry specific to Brașov County, presented in the reports of Brașov Labor Inspectorate, from 2005 to 2019. This study was conducted based on the number of occupational diseases due to silicosis, related to the total number of occupational diseases in Brașov County (study period between 2005 and 2019). Given the state of emergency generated by the COVID-19 pandemic, in order to prevent the spread of this virus and to carry out activities using work from home, telework, and to avoid the interaction between workers as much as possible, online communication with employees is considered as being the only way that allows at the same time both the observance of the measures imposed to prevent the spread of the virus and the implementation of the obligations regarding training on occupational safety and health, which the employer has according to the laws in force. In this context, analyzing the values obtained from the experimental data (number of occupational diseases due to silicosis, related to the total number of occupational diseases in Brasov County) it is identified and solved in the paper the use of online environment, especially in remotely training the workers, who have the opportunity to receive training documents, analyze them, sign them electronically and send them to the employer in electronic format and in this way, being trained even in special situations. Keywords OHS, occupational diseases, silicosis, online training
Tool Wear Evaluation Based on Design Space Exploration Coupled with Explicit Cutting Simulations and Cutting Forces Excitation Signaturehttps://doi.org/10.31926/RECENT.2020.61.060 Abstract Cutting operations are still one of the main methods used in the industry for surface generation in mass production. The dynamics of these processes are complex and having a good insight into the interdependencies of the nonlinear physical phenomena can be translated into better cutting performance. One of the main cutting tool geometrical parameter, usually associated with wear, is the cutting edge radius. Continuous direct evaluation of this parameter exhibits some important limitations offline, if this evaluation needs to be online the whole process becomes very complicated due to the measurement limitations that might appear. For online cases, the best approach is to determine the amplitude of this parameter indirectly using various side effects that can be correlated. One possible option is to monitor the vibrations generated by the resulting cutting forces. In the latest years, the usage of explicit finite element methods (FEM) to simulate the cutting processes has grown exponentially with the continuous increase of computation efficiency. With the help of Computer-Aided Engineering (CAE in short) solutions and using the latest advances in design space exploration (DSE) solutions, it is possible to create models able to parametrically explore a design space (DS), having precise targets, and also get the important correlations for all the important, quantifiable, cutting parameters. This paper presents an innovative method to create tool wear evaluation models focused mainly on the cutting edge radius indirect evaluation. The proposed method uses guided simulation loops able to generate a variety of dynamic signatures which are further post-processed to get a complex correlative model. The model can be applied in real cutting cases using the reciprocity property and can determine online the state of the cutting edge radius for further tool wear evaluation. The paper concludes with an analysis of the obtained model and the applicability of the data for the intended purpose. Keywords design space exploration (DSE), explicit cutting simulation (CAE), tool wear, cutting edge radius, cutting forces
Contributions Regarding the Use of Mechanical Vibrations in Order to Improve the Properties of Steels and Welded Joints Used in Metal Constructionshttps://doi.org/10.31926/RECENT.2020.61.067 Abstract The paper presents aspects regarding the influence of vibrations on the mechanical properties of welded joints, made with basic materials of Spanish and Romanian origin. In this research is presented the practical way to make the necessary assemblies for the proposed tests. The tests show that vibrations have a significant contribution to the quality of welded joints. This is explained by the appearance of several crystallization centres which makes the structure finer. By using vibrations, the atoms are rearranged in the structure, ensuring a proper de-tensioning. The stresses induced in welded metals are significantly reduced by the use of vibration during welding process. The addition materials have a significant contribution to the emergence of stresses in welded joints as well. These stresses can contribute to the appearance of micro-structural constituents with significant hardness. The welding equipment and technologies used also have a significant contribution to the emergence of the remaining stresses. For example, the submerged arc welding technology (SAF) can introduce very high internal stresses. By using vibrations during the welding process, it is achieved a fine structure and a significant reduction of remaining stresses in the welded joints. Keywords welded joints, vibrations, low alloy steels, tensile test
Mechanical Properties of Metal Coating Layers after Laser Heathttps://doi.org/10.31926/RECENT.2020.61.072 Abstract The goal of this research is to study the influence of the laser heat treatment on wearing resistance of metal coating layers. Results reveal the influence of microstructures and chemical composition of used electrodes on microhardness and wear resistance of metal coating layers. Laser heat treatment was applied after coating. Evaluation of results was made by observing the microstructures with metallographic microscopy, SEM/EDX and the mechanical properties were obtained by microhardness and wear resistance. Keywords metal coating, laser heat treatment, wearing resistance
Electromagnetic Vibration System Designed for De-Stressing Welded Joints from Large Metal Constructionshttps://doi.org/10.31926/RECENT.2020.61.078 Abstract The paper presents an electromagnetic installation for producing vibrations, used in the de-tensioning of welded joints of welded constructions. They are also presented novelty elements regarding the domains of use of these types of installations, as well as the benefit of their use. They are highlighted the component parts of these types of installations. This type of electromagnetic installations can be used at the treatment of welded joints used only on magnetic steels. The results obtained with this type of installations are obvious. This vibration system can be used to de-stress welded joints and can successfully replace other types of conventional heat treatment. The components of this installation were purchased commercially. That makes possible that this type of installation can be easily built. The installation has designed a protection system for high voltages and currents. The main purpose of using this type of installation is to reduce the costs of conventional heat treatment, used at welded metal constructions. The installation can be used without strict protection rules. If we talk about the results, we can say that this type of treatment can bring significant economic benefits. Keywords installation, vibration, heat treatment, welded joints, constructions
Peculiarities Regarding the Smooth Entrance of the Drill in Cutting When Processing Steelhttps://doi.org/10.31926/RECENT.2020.61.083Abstract Metal drilling is one of the most common methods of obtaining cylindrical bores. At the same time, the drill is the cutting tool that cuts in the most difficult conditions and consequently any measure that leads to the improvement of the cutting process is useful. The smooth entrance in the cutting is a way to increase the durability of the drill and consequently specific devices have been developed. One of these devices is shown in this paper and previous research shows the effectiveness of its use in drilling. The analysis of the device shows that it is used for cutting 41MoC11 and C45 steels with high speed steel drills, which are in a small range of sizes. The active element of the device is identified, a helical spring working for compression, and by calculating the respective axial force of the torque, is determined exactly the range of diameters of the drills that can cut effectively. At the same time is analyzed the way of enlarging the range of drills used with the device for smooth entrance in cutting, by introducing a second spring, concentric with the first, and which works simultaneously with it, thus the device was reengineered. Keywords cutting, drilling, cutting tool wear
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