The paper presents a part of the comparative experimental researches carried out by the authors o... more The paper presents a part of the comparative experimental researches carried out by the authors on ring-type parts made of a powder mixture consisting of austenitic stainless steel AISI 316L and alumina (Al2O3) powder and on valve supports from the engines of Volkswagen and Audi cars. The purpose of the researches was to determine whether the mentioned valve supports could be manufactured also of the analysed powder mixture. The analysed powder mixture resulted from previous researches carried out by the authors and from studies in the speciality literature. The experiments first targeted the microstructures and microhardnesses of samples taken from the supports of admission and evacuation valves from Volkswagen (A1 and E1) and Audi (A2 and E2) cars, respectively. The same analyses were then applied to ring-shaped parts made by sintering from a mixture of austenitic stainless steel 316L + 30% alumina (Al2O3) powder.
Castability is, along with biocompatibility, one of the most important characteristics of metalli... more Castability is, along with biocompatibility, one of the most important characteristics of metallic materials used for dental prosthetic applications. In addition, the characteristics and performance of the employed casting machine are also decisive for the end result of the casting, especially when dealing with titanium or a titanium alloy. Starting from a critical analysis of the existing methods for determining the castability of dental alloys, the current paper presents a new method (and associated pattern) for determining the castability. Also, given the castability’s dependence on the type of casting machine, the paper includes an analysis of suitable casting machines and suggests some possible improvements.
The paper analyses the various possibilities of cutting complex-shaped parts made of titanium all... more The paper analyses the various possibilities of cutting complex-shaped parts made of titanium alloy TiAl6V4 in conditions of high part precision and short production time: water jet cutting, laser cutting, plasma cutting. Each of these modern, nonconventional means of materials processing has certain benefits, but also shortcomings that need to be taken into account. On the other hand, titanium and titanium alloys are materials that, due to their specific physical and chemical properties pose special problems to the attempts to process them, even if several other of their properties certainly recommend them for a wide range of applications. The specific case of a part from the current production of a Romanian company is analysed and some recommendations are made for the correct choice of the processing parameters and of the NC equipment to be employed.
The current paper refers to one of the new non-conventional forming processes for sheet metal, na... more The current paper refers to one of the new non-conventional forming processes for sheet metal, namely incremental forming. Incremental sheet metal forming represents a complex metal forming process, at which, as compared to the classical stretch forming process, the kinematics comprises beneath a movement on vertical direction also a movement in the blank's plane. This paper targets the study of micro structural modifications suffered by parts obtained by incremental sheet metal forming.
The main method for realising small-size cast parts from nonferrous alloys is the so-called lost ... more The main method for realising small-size cast parts from nonferrous alloys is the so-called lost wax technique. This technique, involving the realising of a wax model of the part that needs to be realised by casting, is widely used for example in the casting of dental prosthetic parts. However, despite the many years passed since the development of this technique, it is still applied empirically, without a strong scientific base supporting it, i.e. for example the sizes and shapes of the runners (casting channels) are chosen based on past experience rather than on solid facts. This paper presents an attempt to optimise the shape of the casting sprue using a mathematical model of the system and equations from solid and fluid mechanics. The main conclusion from these researches is that the shape, in the horizontal plane, of the main runner that leads the metal into the mould should be curved, rather than straight, as it is employed currently by most manufacturers.
Currently there are available several commercial casting installations that can be used for the m... more Currently there are available several commercial casting installations that can be used for the manufacturing of small parts employed in prosthetics. However, these installations generally present some disadvantages related to the material consumption, productivity and not least part quality. The paper presents a new method – and the corresponding casting installation – that eliminates these advantages and can be used to obtain high-quality parts of even very small dimensions.
The realizing and improvement of road infrastructure, of modern road networks provides normal, sa... more The realizing and improvement of road infrastructure, of modern road networks provides normal, safe and pleasant road traffic conditions and also help prevent road accidents. The road network, with its constructive characteristics, has to offer optimal conditions for the movement of vehicles, pedestrians and other categories of participants in the road traffic. Starting from the case study of a road sector with heavy road traffic, the current paper analyzes the increase in road safety in Romanian localities along European and national roads through the implementation of specific measures such as setting up sidewalks, installing New Jersey median barriers, expanding the road sectors with 2+1 lanes, replacing normal pedestrian crossings with elevated crossings or with pedestrian crossing with mid-road waiting areas etc.
The paper presents a part of the comparative experimental researches carried out by the authors o... more The paper presents a part of the comparative experimental researches carried out by the authors on ring-type parts made of a powder mixture consisting of austenitic stainless steel AISI 316L and alumina (Al2O3) powder and on valve supports from the engines of Volkswagen and Audi cars. The purpose of the researches was to determine whether the mentioned valve supports could be manufactured also of the analysed powder mixture. The analysed powder mixture resulted from previous researches carried out by the authors and from studies in the speciality literature. The experiments first targeted the microstructures and microhardnesses of samples taken from the supports of admission and evacuation valves from Volkswagen (A1 and E1) and Audi (A2 and E2) cars, respectively. The same analyses were then applied to ring-shaped parts made by sintering from a mixture of austenitic stainless steel 316L + 30% alumina (Al2O3) powder.
Castability is, along with biocompatibility, one of the most important characteristics of metalli... more Castability is, along with biocompatibility, one of the most important characteristics of metallic materials used for dental prosthetic applications. In addition, the characteristics and performance of the employed casting machine are also decisive for the end result of the casting, especially when dealing with titanium or a titanium alloy. Starting from a critical analysis of the existing methods for determining the castability of dental alloys, the current paper presents a new method (and associated pattern) for determining the castability. Also, given the castability’s dependence on the type of casting machine, the paper includes an analysis of suitable casting machines and suggests some possible improvements.
The paper analyses the various possibilities of cutting complex-shaped parts made of titanium all... more The paper analyses the various possibilities of cutting complex-shaped parts made of titanium alloy TiAl6V4 in conditions of high part precision and short production time: water jet cutting, laser cutting, plasma cutting. Each of these modern, nonconventional means of materials processing has certain benefits, but also shortcomings that need to be taken into account. On the other hand, titanium and titanium alloys are materials that, due to their specific physical and chemical properties pose special problems to the attempts to process them, even if several other of their properties certainly recommend them for a wide range of applications. The specific case of a part from the current production of a Romanian company is analysed and some recommendations are made for the correct choice of the processing parameters and of the NC equipment to be employed.
The current paper refers to one of the new non-conventional forming processes for sheet metal, na... more The current paper refers to one of the new non-conventional forming processes for sheet metal, namely incremental forming. Incremental sheet metal forming represents a complex metal forming process, at which, as compared to the classical stretch forming process, the kinematics comprises beneath a movement on vertical direction also a movement in the blank's plane. This paper targets the study of micro structural modifications suffered by parts obtained by incremental sheet metal forming.
The main method for realising small-size cast parts from nonferrous alloys is the so-called lost ... more The main method for realising small-size cast parts from nonferrous alloys is the so-called lost wax technique. This technique, involving the realising of a wax model of the part that needs to be realised by casting, is widely used for example in the casting of dental prosthetic parts. However, despite the many years passed since the development of this technique, it is still applied empirically, without a strong scientific base supporting it, i.e. for example the sizes and shapes of the runners (casting channels) are chosen based on past experience rather than on solid facts. This paper presents an attempt to optimise the shape of the casting sprue using a mathematical model of the system and equations from solid and fluid mechanics. The main conclusion from these researches is that the shape, in the horizontal plane, of the main runner that leads the metal into the mould should be curved, rather than straight, as it is employed currently by most manufacturers.
Currently there are available several commercial casting installations that can be used for the m... more Currently there are available several commercial casting installations that can be used for the manufacturing of small parts employed in prosthetics. However, these installations generally present some disadvantages related to the material consumption, productivity and not least part quality. The paper presents a new method – and the corresponding casting installation – that eliminates these advantages and can be used to obtain high-quality parts of even very small dimensions.
The realizing and improvement of road infrastructure, of modern road networks provides normal, sa... more The realizing and improvement of road infrastructure, of modern road networks provides normal, safe and pleasant road traffic conditions and also help prevent road accidents. The road network, with its constructive characteristics, has to offer optimal conditions for the movement of vehicles, pedestrians and other categories of participants in the road traffic. Starting from the case study of a road sector with heavy road traffic, the current paper analyzes the increase in road safety in Romanian localities along European and national roads through the implementation of specific measures such as setting up sidewalks, installing New Jersey median barriers, expanding the road sectors with 2+1 lanes, replacing normal pedestrian crossings with elevated crossings or with pedestrian crossing with mid-road waiting areas etc.
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