The Annals of “Dunarea de Jos” University of Galati. Fascicle IX, Metallurgy and Materials Science

Studies and Research Regarding the Creation of a Dental Model, Through Rapid Prototyping Technologies

2024-03-02T19:36:38+02:00

The paper presents the creation of a dental bridge through two rapid prototyping technologies, SLA and FDM. The dental bridge model was made in a dental laboratory, being used later for 3D printing, through rapid prototyping, using the two technologies, FDM and SLA.

Mathematical Modeling of Thermal Processing for an Al-Si Alloy

2024-03-02T19:36:37+02:00

This paper presents the realization of a mathematical model of a heat treatment process of an Al-Si alloy, with the help of which the values of some mechanical properties are preached. The method of elaborating the mathematical model is a statistical method, namely the method of the active experiment.
With the help of the MATLAB software and based on the elaborated mathematical model, we created a graphic interface that allows the prediction of the values of three mechanical properties depending on the thermal processing conditions of the studied alloy.

Comparative Study of Some Materials Used in Nail Plate Prosthesis

2024-03-02T19:36:37+02:00

Nails are involved in most everyday activities, whether physically for seemingly simple actions such, protection against external factors or roles with an aesthetic implication, for the integration of people into society. Often, any change at an aesthetic level is felt both from the point of view of the patient, who can be affected at a psychological level, feeling anxiety due to the lack of a part considered essential, and from the point of view of society that imposes a certain standard to be accepted in the community. Because of this societal standard, people with an untreatable nail deformity or disease can feel marginalized and excluded. Recently, an important number of studies have been carried out in this field, especially since the uses of polymeric materials have gained a wide field of applicability.
In this work, the comparison between three types of polymeric materials used in salon work was highlighted, for the aesthetic treatment of some diseases with a long healing time or even untreatable, by making prostheses for the affected nail plates of onycholysis. The mentioned materials were analysed microscopically, tested for roughness and hardness, and tested for compression and bending resistance, in order to understand how a nail prosthesis made of these materials behaves under different actions and external factors to which the nails are subjected to in daily activities. Finally, the method of making a nail prosthesis from one of the tested polymeric materials was presented and the importance of the functions of the nails, both aesthetic and medical, was highlighted.

Analysis of the Materials Used in Some Rapid Prototyping Technologies, from the Point of View of Microhardness and Surface Quality

2024-03-02T19:36:37+02:00

The paper presents a comparative study, from the point of view of microhardness and surface quality, of samples made from materials used in rapid prototyping technologies, namely photopolymer resin and PLA. Microhardness determinations were made for both materials, with Micro-Vickers HDT-VS1D INSIZE digital automatic hardness tester, and the surface of the samples was analysed, from a qualitative point of view, with the optical microscope, OLYMPUS BX51M.

Optimization of Thermal Treatment Parameters for the Alloy AlZn4.5Mg1

2024-03-02T19:36:37+02:00

The paper presents the method of finding the optimal variant of thermal processing through artificial aging that is applied to a non-ferrous aluminum-based alloy.
The criterion based on which the optimum for the thermal process of artificial aging is obtained is that of the minimum consumption of energy consumed with the heat treatment furnace.
With the help of MATLAB, we created a graphic interface for the calculation simulation of the energy consumed by the treatment furnace depending on the process parameters and the identification of the optimal variant.

Evaluation of Corrosion Behaviour by Gravimetric Method

2024-03-02T19:36:37+02:00

The study aims to evaluate the corrosion behaviour of two steels: BL245 and S235JR, produced at Liberty Steel Galati. BL245 is an alloy used in the oil and gas industry to manufacture pipes for pipeline transportation systems. S235JR is used to make hot finished hollow sections for construction. Gasoline, diesel and a 3.5% sodium chloride solution were chosen as corrosion environments for this study, considering the field of use of the two alloys (oil and construction). Corrosion assessment was analysed using the gravimetric method, which is based on weighing the samples before and after they were immersed for 7, 14, and 35 days in the above-mentioned corrosion environments. Based on the initial weighing and those recorded after the immersion periods, the mass variation of the samples was determined, and the corrosion rate and penetration index were calculated.

Flow Simulation of Fluid Under Pressure, Through Pipes for Oil and Gas Transport

2024-03-02T19:36:37+02:00

The work presents a simulation of the flow of liquids under pressure, through pipelines intended for the transport of oil and natural gas. The simulation was done using the SOLIDWORKS program. Computational Fluid Dynamics (CFD) simulation facilitates the analysis of complex fluid flow problems involving liquid-gas, fluid-solid, or fluid-fluid interactions. CFD allows us to design products and systems that meet fluid flow and heat transfer requirements.

Properties of Dental Zirconium Oxide and Metal-Ceramic: A Comparative Study

2024-03-02T19:36:37+02:00

Zirconium oxide which is intended to be a material that is quite attractive due to its key characteristics, i.e. aesthetic appearance and mechanical resistance, compared to dental metal-ceramics, which to date it has proven to be a satisfactory solution for many of the requirements in the dental market. Understanding the characteristics and properties of these materials provides a starting point for new trends in the development or improvement of solutions for various medical conditions. The research topic of this work aims to understand the characteristics and properties of two categories of materials that are so competitive in the field of dental restoration. For this purpose, the behaviour of some dental crowns made of zirconium oxide and metal ceramic was evaluated in order to obtain experimental data regarding microhardness, corrosion and roughness, before and at different time intervals of immersion in a solution of corrosion, respectively saline solution (3.5% NaCl).

Cholesterol in Human Body: Importance and Dosage

2024-03-02T19:36:37+02:00

For a healthy life, specialists recommend us to take care of what food we eat and to what extent we do it and how we approach a satisfying lifestyle. Cholesterol is not a bad thing, but often, in large quantities it becomes dangerous for human body. The medical world is faced with frequent changes in the concept of "normal values" of cholesterol, but also with a continuously developing pharmaceutical industry in this field, and the tendency is in this sense, towards an individualized treatment. This aspect in presented in our paper, which aims to describe the role of cholesterol in the functioning of human body; preventing the occurrence of heart diseases due increasing the level of cholesterol in the body and creating a healthy lifestyle that can reduce cholesterol levels. The paper presents some case studies on laboratory investigations of values cholesterol that includes determinations, studying and the research of medical equipment (Cobas Integra 400 Plus analyser), but also the results obtained during practice in the medical analysis laboratory.

Mathematical Modeling to Predict Mechanical Properties Values for Hot Rolled S235 Steel

2024-03-02T19:36:37+02:00

The present paper presents the creation of a mathematical model for predicting the values of the mechanical properties of hot -rolled strips. The paper presents the way of developing the mathematical model, based on a statistical development method, namely, the active experiment method.
The equations of the developed mathematical model successfully allow the prediction of the values of the studied mechanical properties, thus saving material, time and money.

Research on the Influence of Chemical Composition and Technological Parameters on the Mechanical Properties of X60M Steel Used in the Production of Oil and Gas Pipelines

2024-03-02T19:36:37+02:00

The work analyses and determines the mechanical properties of the X60M steel used to make welded pipes for oil and gas transportation. X60M type steels are among the materials most used in the construction of pipelines for the transport of natural gas and oil, due to an advantageous price/performance ratio. Determinations were made of resilience and resistance to breaking, yield strength, elongation and transverse contraction, determined by tensile tests, as well as an analysis of the microstructure.

Research on Corrosion Under Tension a Aluminum Alloy AlZn5.7MgCu

2024-03-02T19:36:37+02:00

The paper presents the results of the research on the resistance to stress corrosion on some samples from the alloy. AlZn5.7MgCu which were previously subjected to various thermal and thermomechanical processing.
The gravimetric index or corrosion rate Vcr was used to evaluate the corrosion resistance under tension of the samples investigated in this regard.

Porosity Measurements and Analysis of Sintered and Thermochemical Heat Treated P/M Compacts

2024-03-02T19:36:37+02:00

The objective of this paper was to examine the porosity in fluidized-bed carburizing on sintered alloys obtained by the powder metallurgy route using an image software analysis, and to compare the results with those obtained using the conventional porosity measuring technique. A material's porosity is a measurement of its vacancy percentage. The volume of empty space divided by the material's bulk volume, given as a percentage, determines the overall porosity of the material. The advancement of digital imaging and software has resulted in a novel and appropriate technique for figuring out the porosity of materials used in powder metallurgy.

Chainsaw Sound Detection Using DNN Algorithm

2024-03-02T19:36:37+02:00

Deforestation and illegal logging stand as important environmental problems. In this paper we propose a DNN architecture for sound recognition of chainsaw detection. Various parameters need to be tuned in order to identify the sound of chainsaw but not to produce too much amounts of false positive detection. The task is challenging as different sound emerge in the forest.

Supervised Learning Plastic Defect Algorithm Detection

2024-03-02T19:36:37+02:00

The goal of this research is to develop a supervised learning algorithm able to detect the defects of plastic’s material. Finding patterns or examples in a dataset that differ from the norm is known as anomaly detection in plastic textures. Anomalies, in the context of plastic textures, can refer to imperfections’ deviations, or anomalies in the material that may have an impact on the final product's overall quality. Conventional anomaly detection techniques frequently rely on rule-based systems or manual examination, which can be laborious, subjective, and unable to identify small anomalies.

Modeling and Simulation of Auxetic Materials for Balistic Protection

2024-03-02T19:36:37+02:00

A type of structural metamaterials known as auxetics has a negative Poisson's ratio. Auxetic structurals have been found to possess a number of better qualities when compared to traditional ones, including: greater energy absorption, stronger indentation resistance, and enhanced mechanical properties. As a result, auxetic structures are becoming more known as a high-performance, lightweight defensive construction that can survive collisions and blasts.

Hybrid Nanostructures Based of Ta2O5-PMMA for Electronic Applications

2024-03-02T19:36:37+02:00

The scientific interest on hybrid materials is mainly related to understanding the types of interactions between inorganic and organic component and the effect of these interactions on the properties of the new material formed. Hybrid nanostructured materials and especially dielectrics are used for electronics (for gate layer) and especially those applicable in structure of different types of thin film transistors (TFTs).
In this paper is presented the research on thin film hybrid materials based on tantalum oxide (Ta₂O₅) starting with inorganic precursor - tantalum ethoxide and polymethylmethacrylate (PMMA). The chemical method sol -gel involves the precursor-tantalum ethoxide which is hydrolysed and functionalized (with special siloxane compound), and the organic methyl methacrylate monomer. The chemical reactions take place at low temperature below 160 ^oC. The sol is deposited as thin films by spin-coating to analyse intensity-voltage (I-V) and capacitance-voltage curves (C-V) to determine the electric properties. Metal-Insulator-Metal (MIM) structures were made-up for electric characterisation. The value of leakage currents was between 10^-10 - 10^-7 A at ± 40 V. The hybrid films were analysed by scanning electron microscopy (SEM) for thickness and morphology and for thermal stability the sol was investigated by TG and DSC.
The dielectric permittivity ranges between 3.5 and 4 at 1 MHz, depending on the tantalum alkoxide: MMA molar ratio, showing good behaviour for gate layer in future TFTs.