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Conference Presentations by Eduard Riemschneider

The paper analyzes the effect of the surface microstructure effects on the cavitation erosion fol... more The paper analyzes the effect of the surface microstructure effects on the cavitation erosion following rapid remelting and solidification of gray cast iron parts with lamellar graphite and perlitic matrix. The heat source used was the electric arc generated between the tungsten electrode and the part (TIG). The local melting of the surface was performed at different linear energy values (E l = 3420-5400 J/cm) varying the current between 60 A and 90 A, at a constant voltage of 9.5-10 V. The results showed an increase of the surface hardness at values of 700-740 HV5 and an improvement of the cavitation erosion resistance, the mean penetration depth of the erosion decreasing by 2.4 times, and the erosion rate by 2.2 times.

Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavit... more Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavitation erosion. The TIG remelting technique of the surface of these parts is an efficient way to improve the lifespan of engineering components working in cavitation environments. This paper illustrates the cavitation erosion behavior of a gray cast iron with a microstructure composed of a pearlitic matrix, a small proportion of phosphorous eutectic and lamellar graphite. The cavitation test was performed using an ultrasonic vibrator, and the liquid chosen was water from the public network. Based on the cavitation curves and the examination of the surfaces tested by optical and scanning electron microscopy, a sequence of damage models is proposed to explain the behavior of cavitation erosion.

The paper presents the results of the experiment cavitation vibrators, carried on carbon steel fo... more The paper presents the results of the experiment cavitation vibrators, carried on carbon steel for general use UST 37-2, used in the manufacture of hydraulic turbine components, along the route of water flow into the turbine.Testing is performed on standard crystal vibrator device piezoceramic of the Cavitation Laboratory of the University Politehnica Timisoara. OH12NDL comparison with standard steel and gray iron with pearlite structure shows that steel has low resistance to cavitation generated by the vibrator device, therefore not recommended in the manufacture of parts in areas of developed cavitation.

In this paper we consider a version of the Ramsey growth model in finite and continuous time, wit... more In this paper we consider a version of the Ramsey growth model in finite and continuous time, with the bounded consumption. This model of Ramsey leads to an optimal control problem. We prove an existence theorem of the optimal solution for this optimal control problem.

By surface hardening of the cast iron having metallic matrix consisting of perlite and fine lamel... more By surface hardening of the cast iron having metallic matrix consisting of perlite and fine lamellar graphite separations, it has been aimed an increase in hardness and wear resistance. Testing of cavitation erosion resistance was done in the laboratory in accordance with the standard ASTM G32 2010. The mass losses curves, depending on the duration of the cavitational attack by induction hardened and tempered at 220 ºC samples, were analyzed in comparison with those samples obtained after the stress relief annealing at 525 ºC.The hardness measurements performed on the longitudinal section of the cavitation samples beside the microstructural investigations of the eroded surfaces allowed the explanation of the wear mechanism both by the action of the graphite stress concentrator and also by the sensitivity of the metallic mass to the notch effect.

The adverse effect of cavitation is the destruction of the solid surface microjeturile impact or ... more The adverse effect of cavitation is the destruction of the solid surface microjeturile impact or shock waves generated by the implosion or explosion of cavitation bubbles. It manifests all the pressures fluctuate hydromechanical equipment leading to the emergence and development of these bubbles, due to changing flow sections. The paper examines the behavior and the resistance to cavitation shaker with lamellar graphite gray cast iron and pearlitic microstructure, for the manufacture of the valve bodies and shutters metal-to-metal seal. The experiment is carried out on an apparatus vibratory standard, and the evaluation is performed based on the images microstructure of the surface eroded as well as the comparison of the curves and the specific parameters to those of carbon steel as C45, subject to the anneal for softening, in the annealed state It has a hardness close to that font. Keywords: cast iron, ultrasound cavitation, microstructure 1. INTRODUCTION As compared with the steels, cast iron with lamellar graphite is characterized by a high vibration damping capacity. Therefore, they are used mainly to operational execution required parts to mechanical vibration. Their mechanical properties depend on the size, quantity and distribution of graphite lamellae and the nature of the base metal mass. Because graphite cast irons have a high resistance to wear, good machinability in cutting, good thermal shock resistance and a high casting capacity. Among other things, the microstructure pearlite gray cast irons are used in valves and valve bodies, but for large and shutter body may be a drawer plan (Figure 1.A) or a flat plate / tab (Figure 1B). a) b) Figure 1 Examples of areas subject to cavitation erosion a) plane shutter with slide valve, b) plane shutter with valve disc During operation of these components, there may be significant loss of material due to the impact generated stress with microjets solid surface and shock waves of the cavitation bubbles implode produced in the hydrodynamic [1], [2], [3]. In the present work aimed at establishing the performance of anticavitations with pearlitic microstructure of a cast iron castings intended for the implementation of the composition of hydraulic machinery and equipment [6]. 2. RESEARCH METHODOLOGY The material investigated is cast iron EN-GJL-200 which, after heat treatment for tempering at 525 ± 10 ° C, the following values of mechanical basic resistance: tensile static Rm = 247 MPa and Brinell hardness HB =

Papers by Eduard Riemschneider

METAL 2021 Conference Proeedings, 2021

Numerous engineering components which are in contact with liquid environments that are working un... more Numerous engineering components which are in contact with liquid environments that are working under pressure can be degraded by cavitation erosion. The present paper study the improvement of cavitation erosion resistance of gray cast iron with lamellar graphite and pearlite microstructure by applying the nitriding thermochemical treatment. The cavitation tests were carried out on a vibratory device with piezoceramic crystals in accordance with ASTM G32-2016 standard. The material degradation is demonstrated by mass loss and erosion rate variation depending on the cavitation attack period. As reference material it was considered the same type of gray cast iron, subjected to softening annealing treatment. The eroded surface was examined by optical and scanning electronic microscopy.

Materials Today: Proceedings, 2021

Abstract Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded... more Abstract Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavitation erosion. The TIG remelting technique of the surface of these parts is an efficient way to improve the lifespan of engineering components working in cavitation environments. This paper illustrates the cavitation erosion behavior of a gray cast iron with a microstructure composed of a pearlitic matrix, a small proportion of phosphorous eutectic and lamellar graphite. The cavitation test was performed using an ultrasonic vibrator, and the liquid chosen was water from the public network. Based on the cavitation curves and the examination of the surfaces tested by optical and scanning electron microscopy, a sequence of damage models is proposed to explain the behavior of cavitation erosion.

IOP Conference Series: Materials Science and Engineering, 2018

By surface hardening of the cast iron having metallic matrix consisting of pearlite and fine lame... more By surface hardening of the cast iron having metallic matrix consisting of pearlite and fine lamellar graphite separations, it has been aimed an increase in hardness and wear resistance. Testing of cavitation erosion resistance was done in the laboratory in accordance with the standard ASTM G32 2010. The mass losses curves, depending on the duration of the cavitational attack by induction hardened and tempered at 220 oC samples, were analysed in comparison with those samples obtained after the stress relief annealing at 525 oC. The hardness measurements performed on the longitudinal section of the cavitation samples beside the microstructural investigations of the eroded surfaces allowed the explanation of the wear mechanism both by the action of the graphite stress concentrator and also by the sensitivity of the metallic mass to the notch effect.

CENTRAL EUROPEAN SYMPOSIUM ON THERMOPHYSICS 2019 (CEST)

In this paper we consider a version of the Ramsey growth model in finite and continuous time, wit... more In this paper we consider a version of the Ramsey growth model in finite and continuous time, with the bounded consumption. This model of Ramsey leads to an optimal control problem. We prove an existence theorem of the optimal solution for this optimal control problem.

The paper analyzes the effect of the surface microstructure effects on the cavitation erosion fol... more The paper analyzes the effect of the surface microstructure effects on the cavitation erosion following rapid remelting and solidification of gray cast iron parts with lamellar graphite and perlitic matrix. The heat source used was the electric arc generated between the tungsten electrode and the part (TIG). The local melting of the surface was performed at different linear energy values (E l = 3420-5400 J/cm) varying the current between 60 A and 90 A, at a constant voltage of 9.5-10 V. The results showed an increase of the surface hardness at values of 700-740 HV5 and an improvement of the cavitation erosion resistance, the mean penetration depth of the erosion decreasing by 2.4 times, and the erosion rate by 2.2 times.

Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavit... more Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavitation erosion. The TIG remelting technique of the surface of these parts is an efficient way to improve the lifespan of engineering components working in cavitation environments. This paper illustrates the cavitation erosion behavior of a gray cast iron with a microstructure composed of a pearlitic matrix, a small proportion of phosphorous eutectic and lamellar graphite. The cavitation test was performed using an ultrasonic vibrator, and the liquid chosen was water from the public network. Based on the cavitation curves and the examination of the surfaces tested by optical and scanning electron microscopy, a sequence of damage models is proposed to explain the behavior of cavitation erosion.

The paper presents the results of the experiment cavitation vibrators, carried on carbon steel fo... more The paper presents the results of the experiment cavitation vibrators, carried on carbon steel for general use UST 37-2, used in the manufacture of hydraulic turbine components, along the route of water flow into the turbine.Testing is performed on standard crystal vibrator device piezoceramic of the Cavitation Laboratory of the University Politehnica Timisoara. OH12NDL comparison with standard steel and gray iron with pearlite structure shows that steel has low resistance to cavitation generated by the vibrator device, therefore not recommended in the manufacture of parts in areas of developed cavitation.

In this paper we consider a version of the Ramsey growth model in finite and continuous time, wit... more In this paper we consider a version of the Ramsey growth model in finite and continuous time, with the bounded consumption. This model of Ramsey leads to an optimal control problem. We prove an existence theorem of the optimal solution for this optimal control problem.

By surface hardening of the cast iron having metallic matrix consisting of perlite and fine lamel... more By surface hardening of the cast iron having metallic matrix consisting of perlite and fine lamellar graphite separations, it has been aimed an increase in hardness and wear resistance. Testing of cavitation erosion resistance was done in the laboratory in accordance with the standard ASTM G32 2010. The mass losses curves, depending on the duration of the cavitational attack by induction hardened and tempered at 220 ºC samples, were analyzed in comparison with those samples obtained after the stress relief annealing at 525 ºC.The hardness measurements performed on the longitudinal section of the cavitation samples beside the microstructural investigations of the eroded surfaces allowed the explanation of the wear mechanism both by the action of the graphite stress concentrator and also by the sensitivity of the metallic mass to the notch effect.

The adverse effect of cavitation is the destruction of the solid surface microjeturile impact or ... more The adverse effect of cavitation is the destruction of the solid surface microjeturile impact or shock waves generated by the implosion or explosion of cavitation bubbles. It manifests all the pressures fluctuate hydromechanical equipment leading to the emergence and development of these bubbles, due to changing flow sections. The paper examines the behavior and the resistance to cavitation shaker with lamellar graphite gray cast iron and pearlitic microstructure, for the manufacture of the valve bodies and shutters metal-to-metal seal. The experiment is carried out on an apparatus vibratory standard, and the evaluation is performed based on the images microstructure of the surface eroded as well as the comparison of the curves and the specific parameters to those of carbon steel as C45, subject to the anneal for softening, in the annealed state It has a hardness close to that font. Keywords: cast iron, ultrasound cavitation, microstructure 1. INTRODUCTION As compared with the steels, cast iron with lamellar graphite is characterized by a high vibration damping capacity. Therefore, they are used mainly to operational execution required parts to mechanical vibration. Their mechanical properties depend on the size, quantity and distribution of graphite lamellae and the nature of the base metal mass. Because graphite cast irons have a high resistance to wear, good machinability in cutting, good thermal shock resistance and a high casting capacity. Among other things, the microstructure pearlite gray cast irons are used in valves and valve bodies, but for large and shutter body may be a drawer plan (Figure 1.A) or a flat plate / tab (Figure 1B). a) b) Figure 1 Examples of areas subject to cavitation erosion a) plane shutter with slide valve, b) plane shutter with valve disc During operation of these components, there may be significant loss of material due to the impact generated stress with microjets solid surface and shock waves of the cavitation bubbles implode produced in the hydrodynamic [1], [2], [3]. In the present work aimed at establishing the performance of anticavitations with pearlitic microstructure of a cast iron castings intended for the implementation of the composition of hydraulic machinery and equipment [6]. 2. RESEARCH METHODOLOGY The material investigated is cast iron EN-GJL-200 which, after heat treatment for tempering at 525 ± 10 ° C, the following values of mechanical basic resistance: tensile static Rm = 247 MPa and Brinell hardness HB =

METAL 2021 Conference Proeedings, 2021

Numerous engineering components which are in contact with liquid environments that are working un... more Numerous engineering components which are in contact with liquid environments that are working under pressure can be degraded by cavitation erosion. The present paper study the improvement of cavitation erosion resistance of gray cast iron with lamellar graphite and pearlite microstructure by applying the nitriding thermochemical treatment. The cavitation tests were carried out on a vibratory device with piezoceramic crystals in accordance with ASTM G32-2016 standard. The material degradation is demonstrated by mass loss and erosion rate variation depending on the cavitation attack period. As reference material it was considered the same type of gray cast iron, subjected to softening annealing treatment. The eroded surface was examined by optical and scanning electronic microscopy.

Materials Today: Proceedings, 2021

Abstract Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded... more Abstract Gray cast iron parts with lamellar graphite in contact with liquid media can be degraded by cavitation erosion. The TIG remelting technique of the surface of these parts is an efficient way to improve the lifespan of engineering components working in cavitation environments. This paper illustrates the cavitation erosion behavior of a gray cast iron with a microstructure composed of a pearlitic matrix, a small proportion of phosphorous eutectic and lamellar graphite. The cavitation test was performed using an ultrasonic vibrator, and the liquid chosen was water from the public network. Based on the cavitation curves and the examination of the surfaces tested by optical and scanning electron microscopy, a sequence of damage models is proposed to explain the behavior of cavitation erosion.

IOP Conference Series: Materials Science and Engineering, 2018

By surface hardening of the cast iron having metallic matrix consisting of pearlite and fine lame... more By surface hardening of the cast iron having metallic matrix consisting of pearlite and fine lamellar graphite separations, it has been aimed an increase in hardness and wear resistance. Testing of cavitation erosion resistance was done in the laboratory in accordance with the standard ASTM G32 2010. The mass losses curves, depending on the duration of the cavitational attack by induction hardened and tempered at 220 oC samples, were analysed in comparison with those samples obtained after the stress relief annealing at 525 oC. The hardness measurements performed on the longitudinal section of the cavitation samples beside the microstructural investigations of the eroded surfaces allowed the explanation of the wear mechanism both by the action of the graphite stress concentrator and also by the sensitivity of the metallic mass to the notch effect.

CENTRAL EUROPEAN SYMPOSIUM ON THERMOPHYSICS 2019 (CEST)

In this paper we consider a version of the Ramsey growth model in finite and continuous time, wit... more In this paper we consider a version of the Ramsey growth model in finite and continuous time, with the bounded consumption. This model of Ramsey leads to an optimal control problem. We prove an existence theorem of the optimal solution for this optimal control problem.