Luminita Irimescu | Stefan cel Mare University of Suceava (original) (raw)

Papers by Luminita Irimescu

Research paper thumbnail of Experimental results on interface micro-slip in a rolling contact

In this paper an elliptical torus-plane contact, normally loaded is analysed. In order to point o... more In this paper an elliptical torus-plane contact, normally loaded is analysed. In order to point out the micro-slip due to elastic displacements on the interface contact, experiments were made in repeated rolling. Three scratch marks are experimentally obtained and their placement is in good agreement with the positions of the three maximum equivalent stresses both on traverse and longitudinal directions to rolling. We can conclude that these marks arise from the micro-slip between the surfaces on the contact area. More, the displacements from the sample on the three marks have alternate directions, identically with the micro-slip directions resulted from a numerically model developed by the authors.

Research paper thumbnail of Friction due to microslip in a rolling contact interface

Research paper thumbnail of Shear stresses induced in a rolling contact interface due to micro-slip

Research paper thumbnail of A method of evaluation of elastic hysteresis losses in rolling contact

Research paper thumbnail of Upon rolling friction coefficient

Research paper thumbnail of Huber-Mises-Hencky Equivalent Stress: A Surface Failure Indicator

World Tribology Congress III, Volume 1, 2005

The microslip phenomenon takes place in both rolling and sliding contacts. In the latter case it ... more The microslip phenomenon takes place in both rolling and sliding contacts. In the latter case it occurs in fretting, when the main cause of failure is surface degradation. Both cases are experimentally investigated in order to visualise microslip initiation. The position of the first obtained microslip marks is in good agreement with positions of maximum Huber-Mises-Hencky stress. These results associate the micro-slip initiation with contact stress field and proves the ability of Huber-Mises-Hencky stress to assess the occurrence of failure at the interface of an elastic contact in sliding or rolling motion.

Research paper thumbnail of Tribologie numérique et expertises tribologiques au service d'un contact modèle: le contact'roue-rail

The S. Rajaratnam School of International Studies (RSIS) was established in January 2007 as an au... more The S. Rajaratnam School of International Studies (RSIS) was established in January 2007 as an autonomous School within the Nanyang Technological University. Known earlier as the Institute of Defence and Strategic Studies when it was established in July 1996, RSIS' mission is to be a leading research and graduate teaching institution in strategic and international affairs in the Asia Pacific. To accomplish this mission, it will:  Provide a rigorous professional graduate education with a strong practical emphasis,  Conduct policy-relevant research in defence, national security, international relations, strategic studies and diplomacy,  Foster a global network of like-minded professional schools. GRADUATE EDUCATION IN INTERNATIONAL AFFAIRS RSIS offers a challenging graduate education in international affairs, taught by an international faculty of leading thinkers and practitioners. The Master of Science (M.Sc.) degree programmes in Strategic Studies, International Relations and International Political Economy are distinguished by their focus on the Asia Pacific, the professional practice of international affairs, and the cultivation of academic depth. Thus far, students from more than 50 countries have successfully completed one of these programmes. In 2010, a Double Masters Programme with Warwick University was also launched, with students required to spend the first year at Warwick and the second year at RSIS. A small but select Ph.D. programme caters to advanced students who are supervised by faculty members with matching interests.

Research paper thumbnail of Analyse tribologique du contact roue-rail en couplant tribologie numérique et expertises tribologiques

HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil;... more HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil; Dépôt: S'authentifier; S'inscrire. Consultation: Par domaine; Les 30 derniers dépôts; Par année de publication, rédaction, dépôt; Par type de publication; ...

Research paper thumbnail of Dynamics of Some Physical and Chemical Indicators of Suceava River Water in 2009

For a physical-chemical evaluation of global quality of Suceava river water, water samples were c... more For a physical-chemical evaluation of global quality of Suceava river water, water samples were collected every two months during 2009, on the following sections (sites, locations): • Brodina at 142 km distance from mouth; • Mihoveni, 45 km distance from mouth; • Tisăuţi, 34 km distance from mouth. The values obtained from physical - chemical analyzes of water were processed and compared with the limit values of quality grades, provided by the norm on surface water quality classification, in order to determine the ecological status of water bodies according to Order nr.161/2006. Along Suceava river, the water flows increase from upstream to downstream: the maximum value 4.47 m3/s at Brodina (14.07.2009) increase at Mihoveni, the maximum value being 13.22 m3/s (14.07.2009) and at Tisăuţi, the flow recorded on 14.07.2009 is 13.7 m3/s. The annual average flows have fluctuated on very wide limits, depending on pluviometrical characteristics of rainfall on each year. Usually, the highest...

Research paper thumbnail of Some Remarks on Contact Models of Fingerpad-Part II: Surface Stresses

Abstract: Distal phalanx biomechanics is important in human manipulation of objects and therefore... more Abstract: Distal phalanx biomechanics is important in human manipulation of objects and therefore the model of fingerpad is essential. In order to model finger grasping for a wide range of applications, from medical to robotics, information on a large variety of parameters is ...

Research paper thumbnail of Influence of the initial structure on the critical points in solid-state phase transformation of some hypoeutectoid steels

This study allowed, by dilatometric analyses, both to highlight the solid state transformations t... more This study allowed, by dilatometric analyses, both to highlight the solid state transformations that occurred during the continuous heating of three hypoeutectoid steels (with 0.087% C 0.511% Mn, 0.101% C 0.529% Mn and 0.093% C 1.922% Mn), as well as to investigate the effect of the initial ferrite-pearlite structure on the critical points at which these transformations occurred. Dilatometric analyses were performed on specimens of steels with unmodified structures (as-delivered structures) and on specimens with structures obtained from full annealing (heating at 980 C for 60 minutes and slow cooling in the furnace). These structures (with different grain size indices, mean diameters and mean area of grain) have influenced both the aspect of the dilatometric and the first derivative curves, as well as the values of the critical points in solid-state phase transformation.

Research paper thumbnail of Device for Studying Sliding Friction

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel bar and two drive rollers on which it is supported. Movement of the steel bar is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational movements with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal bar. By measuring the oscillation period of the steel bar, the friction coefficient between the bar and the drive roller is obtained.

Research paper thumbnail of Influence of the initial structure on the critical points in solid-state phase transformation of some hypoeutectoid steels

This study allowed, by dilatometric analyses, both to highlight the solid state transformations t... more This study allowed, by dilatometric analyses, both to highlight the solid state transformations that occurred during the continuous heating of three hypoeutectoid steels (with 0.087% C 0.511% Mn, 0.101% C 0.529% Mn and 0.093% C 1.922% Mn), as well as to investigate the effect of the initial ferrite-pearlite structure on the critical points at which these transformations occurred. Dilatometric analyses were performed on specimens of steels with unmodified structures (as-delivered structures) and on specimens with structures obtained from full annealing (heating at 980 C for 60 minutes and slow cooling in the furnace). These structures (with different grain size indices, mean diameters and mean area of grain) have influenced both the aspect of the dilatometric and the first derivative curves, as well as the values of the critical points in solid-state phase transformation.

Research paper thumbnail of Device for Studying Sliding Friction

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel bar and two drive rollers on which it is supported. Movement of the steel bar is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational movements with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal bar. By measuring the oscillation period of the steel bar, the friction coefficient between the bar and the drive roller is obtained.

Research paper thumbnail of Considerations on friction coefficient in a simple harmonic motion

IOP Conference Series: Materials Science and Engineering, 2018

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel rod and two drive rollers on which it is supported. The motion of the steel rod is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational motions with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal rod. By measuring the oscillation period of the steel rod, the coefficient of sliding friction between the rod and the drive roller is obtained.

Research paper thumbnail of Considerations on friction coefficient in a simple harmonic motion

IOP Conference Series: Materials Science and Engineering, 2018

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel rod and two drive rollers on which it is supported. The motion of the steel rod is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational motions with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal rod. By measuring the oscillation period of the steel rod, the coefficient of sliding friction between the rod and the drive roller is obtained.

Research paper thumbnail of Experimental Aspects Concerning Self-locking Angle

SYROM 2009, 2009

Self-locking is a phenomenon that occurs both in lower pairs and higher pairs, being quantified b... more Self-locking is a phenomenon that occurs both in lower pairs and higher pairs, being quantified by the self-locking angle; it occurs due to friction forces, depending directly on normal forces from mechanism pairs. The paper presents some preliminary experimental aspects regarding the influence of different parameters (bushing geometry and material, shaft heat treating, gap dimension and friction type, rolling/sliding for

Research paper thumbnail of Proposed parameter for the characterization of friction in cylindrical gears teeth contact

IOP Conference Series: Materials Science and Engineering, 2020

Gear mechanisms are widely used in technical applications, mainly for transmitting rotational mot... more Gear mechanisms are widely used in technical applications, mainly for transmitting rotational motion between two axes with constant transmission ratio via a higher pair. Significant friction energy loss in the pair between teeth highlights the importance of estimating the mechanical work lost by friction within this contact. In a previous study, the coefficient of rolling friction between a cylindrical body and a flat face body was found based on the decrease of oscillations amplitude of a cycloidal pendulum. The basic idea of the present paper follows the observation that in the case of a gear mechanism, the relative motion between the wheels can be taken as relative motion of their axodes. In this regard, a pendulum obtained from a mobile cylindrical gear with attached rod and a fixed corresponding rack is considered. The law of motion of the cycloidal pendulum is applied for the proposed pendulum and an “equivalent rolling friction coefficient” which characterises the friction be...

Research paper thumbnail of Structures and Mechanical Properties of Some Dual-Phase Steels with Low Manganese Content

Metals

In recent years, to reduce cars costs, research has been conducted on dual-phase steels with low ... more In recent years, to reduce cars costs, research has been conducted on dual-phase steels with low manganese content (below 1.0%). This study investigated the influence of technological parameters of heat treatment (heating temperature and cooling medium) on such steels’ structures and mechanical properties. The ferrite-martensitic structures, specific for dual-phase steels, were obtained by intercritical quenching: heating of samples (made of alloys with 0.511% Mn, respectively 0.529% Mn) to temperatures located between critical points Ac1 and Ac3, followed by cooling in water without mechanical agitation and in water activated with ultrasounds at the frequency of 59 kHz. Through metallographic analyses and tensile tests, it was possible to determine the volume fraction of martensite, the ferrite microhardness, the ultimate tensile strength, the total elongation, and with the obtained data, their variations with the heating temperature and the cooling medium were established. Raising...

Research paper thumbnail of Method and device for measurement of dynamic viscosity

IOP Conference Series: Materials Science and Engineering, 2017

The paper proposes a methodology and ensuing test rig for finding the viscosity of a liquid lubri... more The paper proposes a methodology and ensuing test rig for finding the viscosity of a liquid lubricant. The principle consists in obtaining a contact between two spherical surfaces, one concave and the other one convex. One of the surfaces is kept immobile and to the other, a rotation motion is imposed around the common normal in the contact point and then the law of motion for the mobile lens is found. The law of motion allows for estimation of friction torque, dependent on viscosity at its turn. Applying the method for mineral oils, values comparable to the ones presented by the producer were obtained.

Research paper thumbnail of Experimental results on interface micro-slip in a rolling contact

In this paper an elliptical torus-plane contact, normally loaded is analysed. In order to point o... more In this paper an elliptical torus-plane contact, normally loaded is analysed. In order to point out the micro-slip due to elastic displacements on the interface contact, experiments were made in repeated rolling. Three scratch marks are experimentally obtained and their placement is in good agreement with the positions of the three maximum equivalent stresses both on traverse and longitudinal directions to rolling. We can conclude that these marks arise from the micro-slip between the surfaces on the contact area. More, the displacements from the sample on the three marks have alternate directions, identically with the micro-slip directions resulted from a numerically model developed by the authors.

Research paper thumbnail of Friction due to microslip in a rolling contact interface

Research paper thumbnail of Shear stresses induced in a rolling contact interface due to micro-slip

Research paper thumbnail of A method of evaluation of elastic hysteresis losses in rolling contact

Research paper thumbnail of Upon rolling friction coefficient

Research paper thumbnail of Huber-Mises-Hencky Equivalent Stress: A Surface Failure Indicator

World Tribology Congress III, Volume 1, 2005

The microslip phenomenon takes place in both rolling and sliding contacts. In the latter case it ... more The microslip phenomenon takes place in both rolling and sliding contacts. In the latter case it occurs in fretting, when the main cause of failure is surface degradation. Both cases are experimentally investigated in order to visualise microslip initiation. The position of the first obtained microslip marks is in good agreement with positions of maximum Huber-Mises-Hencky stress. These results associate the micro-slip initiation with contact stress field and proves the ability of Huber-Mises-Hencky stress to assess the occurrence of failure at the interface of an elastic contact in sliding or rolling motion.

Research paper thumbnail of Tribologie numérique et expertises tribologiques au service d'un contact modèle: le contact'roue-rail

The S. Rajaratnam School of International Studies (RSIS) was established in January 2007 as an au... more The S. Rajaratnam School of International Studies (RSIS) was established in January 2007 as an autonomous School within the Nanyang Technological University. Known earlier as the Institute of Defence and Strategic Studies when it was established in July 1996, RSIS' mission is to be a leading research and graduate teaching institution in strategic and international affairs in the Asia Pacific. To accomplish this mission, it will:  Provide a rigorous professional graduate education with a strong practical emphasis,  Conduct policy-relevant research in defence, national security, international relations, strategic studies and diplomacy,  Foster a global network of like-minded professional schools. GRADUATE EDUCATION IN INTERNATIONAL AFFAIRS RSIS offers a challenging graduate education in international affairs, taught by an international faculty of leading thinkers and practitioners. The Master of Science (M.Sc.) degree programmes in Strategic Studies, International Relations and International Political Economy are distinguished by their focus on the Asia Pacific, the professional practice of international affairs, and the cultivation of academic depth. Thus far, students from more than 50 countries have successfully completed one of these programmes. In 2010, a Double Masters Programme with Warwick University was also launched, with students required to spend the first year at Warwick and the second year at RSIS. A small but select Ph.D. programme caters to advanced students who are supervised by faculty members with matching interests.

Research paper thumbnail of Analyse tribologique du contact roue-rail en couplant tribologie numérique et expertises tribologiques

HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil;... more HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil; Dépôt: S'authentifier; S'inscrire. Consultation: Par domaine; Les 30 derniers dépôts; Par année de publication, rédaction, dépôt; Par type de publication; ...

Research paper thumbnail of Dynamics of Some Physical and Chemical Indicators of Suceava River Water in 2009

For a physical-chemical evaluation of global quality of Suceava river water, water samples were c... more For a physical-chemical evaluation of global quality of Suceava river water, water samples were collected every two months during 2009, on the following sections (sites, locations): • Brodina at 142 km distance from mouth; • Mihoveni, 45 km distance from mouth; • Tisăuţi, 34 km distance from mouth. The values obtained from physical - chemical analyzes of water were processed and compared with the limit values of quality grades, provided by the norm on surface water quality classification, in order to determine the ecological status of water bodies according to Order nr.161/2006. Along Suceava river, the water flows increase from upstream to downstream: the maximum value 4.47 m3/s at Brodina (14.07.2009) increase at Mihoveni, the maximum value being 13.22 m3/s (14.07.2009) and at Tisăuţi, the flow recorded on 14.07.2009 is 13.7 m3/s. The annual average flows have fluctuated on very wide limits, depending on pluviometrical characteristics of rainfall on each year. Usually, the highest...

Research paper thumbnail of Some Remarks on Contact Models of Fingerpad-Part II: Surface Stresses

Abstract: Distal phalanx biomechanics is important in human manipulation of objects and therefore... more Abstract: Distal phalanx biomechanics is important in human manipulation of objects and therefore the model of fingerpad is essential. In order to model finger grasping for a wide range of applications, from medical to robotics, information on a large variety of parameters is ...

Research paper thumbnail of Influence of the initial structure on the critical points in solid-state phase transformation of some hypoeutectoid steels

This study allowed, by dilatometric analyses, both to highlight the solid state transformations t... more This study allowed, by dilatometric analyses, both to highlight the solid state transformations that occurred during the continuous heating of three hypoeutectoid steels (with 0.087% C 0.511% Mn, 0.101% C 0.529% Mn and 0.093% C 1.922% Mn), as well as to investigate the effect of the initial ferrite-pearlite structure on the critical points at which these transformations occurred. Dilatometric analyses were performed on specimens of steels with unmodified structures (as-delivered structures) and on specimens with structures obtained from full annealing (heating at 980 C for 60 minutes and slow cooling in the furnace). These structures (with different grain size indices, mean diameters and mean area of grain) have influenced both the aspect of the dilatometric and the first derivative curves, as well as the values of the critical points in solid-state phase transformation.

Research paper thumbnail of Device for Studying Sliding Friction

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel bar and two drive rollers on which it is supported. Movement of the steel bar is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational movements with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal bar. By measuring the oscillation period of the steel bar, the friction coefficient between the bar and the drive roller is obtained.

Research paper thumbnail of Influence of the initial structure on the critical points in solid-state phase transformation of some hypoeutectoid steels

This study allowed, by dilatometric analyses, both to highlight the solid state transformations t... more This study allowed, by dilatometric analyses, both to highlight the solid state transformations that occurred during the continuous heating of three hypoeutectoid steels (with 0.087% C 0.511% Mn, 0.101% C 0.529% Mn and 0.093% C 1.922% Mn), as well as to investigate the effect of the initial ferrite-pearlite structure on the critical points at which these transformations occurred. Dilatometric analyses were performed on specimens of steels with unmodified structures (as-delivered structures) and on specimens with structures obtained from full annealing (heating at 980 C for 60 minutes and slow cooling in the furnace). These structures (with different grain size indices, mean diameters and mean area of grain) have influenced both the aspect of the dilatometric and the first derivative curves, as well as the values of the critical points in solid-state phase transformation.

Research paper thumbnail of Device for Studying Sliding Friction

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel bar and two drive rollers on which it is supported. Movement of the steel bar is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational movements with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal bar. By measuring the oscillation period of the steel bar, the friction coefficient between the bar and the drive roller is obtained.

Research paper thumbnail of Considerations on friction coefficient in a simple harmonic motion

IOP Conference Series: Materials Science and Engineering, 2018

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel rod and two drive rollers on which it is supported. The motion of the steel rod is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational motions with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal rod. By measuring the oscillation period of the steel rod, the coefficient of sliding friction between the rod and the drive roller is obtained.

Research paper thumbnail of Considerations on friction coefficient in a simple harmonic motion

IOP Conference Series: Materials Science and Engineering, 2018

An experimental device was designed and developed to study the friction coefficient between a ste... more An experimental device was designed and developed to study the friction coefficient between a steel rod and two drive rollers on which it is supported. The motion of the steel rod is achieved by means of two rods mounted on bearing and driven by two engines. The two rollers have rotational motions with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal rod. By measuring the oscillation period of the steel rod, the coefficient of sliding friction between the rod and the drive roller is obtained.

Research paper thumbnail of Experimental Aspects Concerning Self-locking Angle

SYROM 2009, 2009

Self-locking is a phenomenon that occurs both in lower pairs and higher pairs, being quantified b... more Self-locking is a phenomenon that occurs both in lower pairs and higher pairs, being quantified by the self-locking angle; it occurs due to friction forces, depending directly on normal forces from mechanism pairs. The paper presents some preliminary experimental aspects regarding the influence of different parameters (bushing geometry and material, shaft heat treating, gap dimension and friction type, rolling/sliding for

Research paper thumbnail of Proposed parameter for the characterization of friction in cylindrical gears teeth contact

IOP Conference Series: Materials Science and Engineering, 2020

Gear mechanisms are widely used in technical applications, mainly for transmitting rotational mot... more Gear mechanisms are widely used in technical applications, mainly for transmitting rotational motion between two axes with constant transmission ratio via a higher pair. Significant friction energy loss in the pair between teeth highlights the importance of estimating the mechanical work lost by friction within this contact. In a previous study, the coefficient of rolling friction between a cylindrical body and a flat face body was found based on the decrease of oscillations amplitude of a cycloidal pendulum. The basic idea of the present paper follows the observation that in the case of a gear mechanism, the relative motion between the wheels can be taken as relative motion of their axodes. In this regard, a pendulum obtained from a mobile cylindrical gear with attached rod and a fixed corresponding rack is considered. The law of motion of the cycloidal pendulum is applied for the proposed pendulum and an “equivalent rolling friction coefficient” which characterises the friction be...

Research paper thumbnail of Structures and Mechanical Properties of Some Dual-Phase Steels with Low Manganese Content

Metals

In recent years, to reduce cars costs, research has been conducted on dual-phase steels with low ... more In recent years, to reduce cars costs, research has been conducted on dual-phase steels with low manganese content (below 1.0%). This study investigated the influence of technological parameters of heat treatment (heating temperature and cooling medium) on such steels’ structures and mechanical properties. The ferrite-martensitic structures, specific for dual-phase steels, were obtained by intercritical quenching: heating of samples (made of alloys with 0.511% Mn, respectively 0.529% Mn) to temperatures located between critical points Ac1 and Ac3, followed by cooling in water without mechanical agitation and in water activated with ultrasounds at the frequency of 59 kHz. Through metallographic analyses and tensile tests, it was possible to determine the volume fraction of martensite, the ferrite microhardness, the ultimate tensile strength, the total elongation, and with the obtained data, their variations with the heating temperature and the cooling medium were established. Raising...

Research paper thumbnail of Method and device for measurement of dynamic viscosity

IOP Conference Series: Materials Science and Engineering, 2017

The paper proposes a methodology and ensuing test rig for finding the viscosity of a liquid lubri... more The paper proposes a methodology and ensuing test rig for finding the viscosity of a liquid lubricant. The principle consists in obtaining a contact between two spherical surfaces, one concave and the other one convex. One of the surfaces is kept immobile and to the other, a rotation motion is imposed around the common normal in the contact point and then the law of motion for the mobile lens is found. The law of motion allows for estimation of friction torque, dependent on viscosity at its turn. Applying the method for mineral oils, values comparable to the ones presented by the producer were obtained.