In the field of bone tissue engineering, particular interest is devoted to the development of 3D ... more In the field of bone tissue engineering, particular interest is devoted to the development of 3D cultures to study bone cell proliferation under conditions similar to in vivo ones, e.g. by artificially producing mechanical stresses promoting a biological response (mechanotransduction). Of particular relevance in this context are the effects generated by the flow shear stress, which governs the nutrients delivery rate to the growing cells and which can be controlled in perfusion reactors. However, the introduction of 3D scaffolds complicates the direct measurement of the generated shear stress on the adhered cells inside the matrix, thus jeopardizing the potential of using multi-dimensional matrices. In this study, an anisotropic hydroxyapatite-based set of scaffolds is considered as a 3D biomimetic support for bone cells deposition and growth. Measurements of sample-specific flow resistance are carried out using a perfusion system, accompanied by a visual characterization of the mat...
This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of exter... more This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of external gear machines. The model is built considering and evaluating the main friction losses in the machines, including the viscous friction losses at the tooth tip gap, at the bearing blocks-gears gaps, at the journal bearings, and the meshing loss. To calculate the shear stress at each gap interface, the geometry of the gap has to be known. For this reason, the actual position of the gears inside the pump casing and consequent radial pressure distribution are numerically calculated to evaluate the gap height at the tooth tips. Moreover, the variation of the tilt and reference height of the lateral gaps between the gears and the pump bushings are considered. The shear stresses within the lateral gaps are estimated, for different lateral heights and tilt values. At the journal bearings gaps, the half Sommerfeld solution has been applied. The meshing loss has been calculated according to the...
This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured ... more This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured with MC3T3 osteoblasts in response to flow-induced shear stress (FSS). The scaffold adopted here (B-HA) derives from the biomorphic transformation of natural wood and its peculiar channel geometry mimics the porous structure of the bone. From the point of view of fluid dynamics, B-HA can be considered a network of micro-channels, intrinsically offering the advantages of a microfluidic system. This work, for the first time, offers a description of the fluid dynamic properties of the B-HA scaffold, which are strongly connected to its morphology. These features are necessary to determine the FSS ranges to be applied during in vitro studies to get physiologically relevant conditions. The selected ranges of FSS promoted the elongation of the attached cells along the flow direction and early osteogenic cell differentiation. These data confirmed the ability of B-HA to promote the differentiatio...
<jats:p>Hydraulic pressure amplifiers of the cylinder type are much appreciated in hydrauli... more <jats:p>Hydraulic pressure amplifiers of the cylinder type are much appreciated in hydraulic systems where high pressure work is needed only for a limited period of time, while during the remaining duty cycle the system operates at a standard level of pressure. The use of these elements allows the designer not to oversize the system, which will perform the work with a considerable power saving, confining the high pressure operation only on the side of the hydraulic cylinder.</jats:p> <jats:p>This works describes the modelling and simulation of a compact cartridge pressure amplifier for linear actuators. The cartridge amplifier is able to double or more the pressure in the system when needed and to not interfere during normal operation of the system. It has been designed to fit in the narrow space of the rod of normal hydraulic cylinder, being extremely compact and efficient. Designing such a component and the study of the main design parameters influence have required a strong work of modelling and simulation, performed with a lumped parameters approach to depict the dynamic behaviour of the amplifier. This work illustrates the building of the model and a first comparison between simulated and experimental data. Moreover, the simulation activity is enlarged to analysis of the influence of some operating and design parameters on the amplifier dynamic behavior.</jats:p>
This work aims to analyze a complete hydraulic system of a medium size agricultural tractor, in o... more This work aims to analyze a complete hydraulic system of a medium size agricultural tractor, in order to perform an energy dissipation analysis and to suggest possibly alternative configurations and solutions. The fuel consumption and energy dissipation in off road vehicles have in fact become a key feature, given the great attention devoted to the need of reducing pollutant emissions, in order to satisfy the future emission limits. In this work the focus is on the fluid power supply group and the standard architecture of this unit has been compared with an alternative solution, called variable pump margin strategy and compared on the basis of the power consumption to perform the same duty cycle, showing that a relevant percentage of energy may be saved with simple modifications in the hydraulic power generator group.
In questo lavoro si descrive la metodologia utilizzata per caratterizzare una parte del circuito ... more In questo lavoro si descrive la metodologia utilizzata per caratterizzare una parte del circuito idraulico di una trattrice agricola. Lo scopo dell\u2019attivit\ue0 \ue8 stato quello di ricavare informazioni necessarie alla definizione delle caratteristiche di regolazione della parte di circuito analizzata da utilizzare successivamente in un modello di simulazione del circuito stesso con il quale replicare poi in un ambiente virtuale le effettive condizioni di lavoro incontrate dal veicolo durante le lavorazioni
The paper describes the influence of the fluid modeling on cavitation and aeration detection in e... more The paper describes the influence of the fluid modeling on cavitation and aeration detection in external gear pumps and motors inter-teeth volumes during the gears meshing process, in order to compare the results coming from the use of different physical models of air release/adsorption and cavitation. A simplified cavitation model is firstly involved, and pressure transients are calculated imposing a pressure cut when the fluid vapor pressure (or the dissolved air partial pressure) is reached. After, assuming an equivalent approach able to involve the vapor phase generation, the cavitation phenomena in the meshing volumes are deepened, and the influence of the fluid modeling enhancement on the cavitating machine behavior is highlighted. Then, the equivalent fluid approach is enhanced introducing the air release, and properly coupling the gaseous phases release/adsorption to the Henry's Law for not instantaneous processes. Finally, the influence of the air release/adsorption tim...
This paper studies the proportional directional controlvalves design influence on the energetic b... more This paper studies the proportional directional controlvalves design influence on the energetic behavior of amid-power compact excavator.In particular, with reference to the hydraulic circuitactuating the primary workgroup, in the paper thehydraulic power metering performed with the boomcylinder proportional control valve is studied, and somedesign solution useful in reducing both the hydraulicpower dissipation, and the power absorption from themachinery prime mover are highlighted.The analysis, experimentally performed for differentoperating conditions, is carried out highlighting theinfluence of a metering configuration both on the supplypressure modulation and on the flow-rate supplied tothe actuator.The hydraulic power metering and the boom actuationhydraulic efficiency are defined for two alternativeproportional control valve metering configurations and,within the limits implicitly implied on the actuation circuitarchitecture, a possible design solution in determiningthe improvement of the boom actuation systemperformances is investigated
In this paper some design aspects related to externalgear pumps balancing surfaces are studied, a... more In this paper some design aspects related to externalgear pumps balancing surfaces are studied, and someuseful guidelines for designing bearing blocksbalancing surfaces are suggested. In order to studybearing blocks axial balance, a numerical procedurefor the determination of the pressure distribution insidethe clearance bounded by gears sides and bearingblocks internal surfaces is firstly presented andapplied. After, the influence of bearing blocksgeometry and pump operating conditions on thewidening thrust is highlighted, considering bothconstant and variable lateral clearance heights. Then,the computations are performed to evaluate thewidening thrust variation as a function of bearingblocks relative tilt with respect to gears lateral sides,and both positive and negative bearing blocks tilts areevidenced and discussed. Finally, the numericalprocedure is validated through a comprehensivecomparison of its results with experimental data(coming from some bibliographic sources), and someuseful guidelines in designing external gear pumpsbalancing surfaces are defined
In this paper a lumped parameters numerical model isreviewed to study the meshing process of exte... more In this paper a lumped parameters numerical model isreviewed to study the meshing process of external gearpumps and motors, with the aim of highlighting theinfluence of some geometrical design parameters andoperating conditions on inter-teeth volumes pressures.The inter-teeth space is modeled adopting a two-volumeapproach, properly tailored both for the pump and for themotor units behavior description. In both cases, thecommunications between the interconnected inter-teethvolumes and the high and low pressure ports aresketched as variable equivalent turbulent restrictors; flowareas have been determined as functions of the gearsand of the meshing grooves main design parameters.The inter-teeth pressures, and the leakage flows, arecalculated solving the incompressible and isothermalcontinuity equation, contemporarily applied to bothvolumes and properly combined with the classicalturbulent orifice equation. Successively, for a referenceoperating condition, properly chosen for underlining theinter-teeth meshing cycle and corresponding to a verylow pressure load, the meshing processes of an externalgear pump and of an external gear motor are compared.Among others, the attention is focused on the behaviorof those hydraulic variables more conditioning themeshing cycle, and the differences rising up in interteethpressure peaks and in cavitation interval amplitudeand angular positioning are evidenced. Then, themeshing process analysis is expanded to cover theexternal gear units common operating field, both interms of rotational speed (from 500 to 3000 rpm) and interms of the high pressure port value (from 10 to 250bar). In all cases, the general trend shows that cavitationhas a deeper influence on external gear pumpsoperation, while external gear motors are subjected tomore significant pressure peaks, particularly markedduring the low pressure part of the meshing cycle.Attention is also focused on the influence of gears interaxialdistance and axial width on the meshing processcharacteristics, in order to assess how the volumedimensions could differently affect pressure peaks andcavitation phenomena in pumps and motors.Finally, the role of the balancing plates grooves inconditioning pressure peaks and cavitation is highlightedand, with particular care devoted to external gearmotors, some useful guidelines for their design areoutlined
The paper deals with the analysis of the inter-teeth pressure transients during gears meshing cyc... more The paper deals with the analysis of the inter-teeth pressure transients during gears meshing cycle of external gear pumps. A lumped parameter model, tailored for the prediction of pressures in the meshing zone, is firstly presented. The numerical model, based on the integration of the continuity equation, is applied to the inter-teeth volumes, communicating with the neighbouring ambient through geometry dependent orifices. A comparison between numerical results, obtained considering both constant and variable discharge coefficients, is illustrated. Successively, the dependency of pressure transients on gear pump operating conditions, mainly in terms of delivery pressure and rotational speed, is investigated. The effect of some geometric parameters is also discussed, mainly considering different gears widths and interaxial distances, and high-pressure recess positioning. Finally, in order to highlight the influence of the cavitation modelling on low pressure transition, the results coming from the application of two simplified approaches are shown and compared
External gear pumps and motors are robust and low cost components and are widely used in industri... more External gear pumps and motors are robust and low cost components and are widely used in industrial and mobile applications; nowadays however, optimal global efficiency represents a more crucial aspect to be considered when designing a hydraulic machine. For this reason, it becomes a primary necessity to investigate the phenomena which determine and affect the hydraulic machine total efficiency.In this work, the volumetric efficiency of external gear pumps is investigated by means of a mathematical model already presented in a previous paper and the results obtained are compared with experimental data.First of all, the mathematical model is briefly presented; then the predicted results are discussed considering the influence of the pump operating conditions. Moreover, the influence on the volumetric efficiency of the behaviour of the hydraulically balanced bearing blocks, and hence of the pump axial balance, is exposed. In particular, it is shown that the tilted position of the bearing blocks and the height of the lateral clearance can greatly affect the volumetric efficiency.The data coming from an experimental investigation carried out on commercial external gear pump units are then presented; both the volumetric and the mechanical efficiency have been measured.The comparison between the experimental data and the numerical results allows discussing the bearing blocks balancing behaviour during pump operation
This work aims to analyse a complete hydraulic system of a medium size agricultural tractor, in o... more This work aims to analyse a complete hydraulic system of a medium size agricultural tractor, in order to perform an energy dissipation analysis and to test possible alternative configurations and solutions. The fuel consumption and energy dissipation in off-road vehicles have infact become a key feature, given the great attention devoted to the need of reducing pollutant emissions, in order to satisfy the future emission limits. Standard and alternative architecture configurations are modelled and compared on the basis of the power consumption to perform the same duty cycle. Among the results, it is worth highlighting that a relevant percentage of energy may be saved with simple modifications in the hydraulic power generation group.
In the hydraulic servo-cylinders design, the circumferential grooves are used in order to reduce ... more In the hydraulic servo-cylinders design, the circumferential grooves are used in order to reduce the effect of the locking force. This force arises as a consequence to the distribution of pressure around the piston, when both an eccentric position, caused by the load on the piston, and the manufacturing defects on the piston and cylinder surfaces are present. In this work an approach is presented for the calculation of the contribution of the grooves in the definition of the locking force and of the leakage flow rate. The mathematical model proposed is based on the Reynolds equation, properly combined with the continuity equation applied within the grooves. The results of the analysis are combined together with the ones coming from the analysis at the hydrostatic bearings at the rod ends, which have been analyzed on a previous step of the research. A numerical procedure is then created that, with the appropriate input, allows to study the different design configurations of the servo...
In the field of bone tissue engineering, particular interest is devoted to the development of 3D ... more In the field of bone tissue engineering, particular interest is devoted to the development of 3D cultures to study bone cell proliferation under conditions similar to in vivo ones, e.g. by artificially producing mechanical stresses promoting a biological response (mechanotransduction). Of particular relevance in this context are the effects generated by the flow shear stress, which governs the nutrients delivery rate to the growing cells and which can be controlled in perfusion reactors. However, the introduction of 3D scaffolds complicates the direct measurement of the generated shear stress on the adhered cells inside the matrix, thus jeopardizing the potential of using multi-dimensional matrices. In this study, an anisotropic hydroxyapatite-based set of scaffolds is considered as a 3D biomimetic support for bone cells deposition and growth. Measurements of sample-specific flow resistance are carried out using a perfusion system, accompanied by a visual characterization of the mat...
This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of exter... more This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of external gear machines. The model is built considering and evaluating the main friction losses in the machines, including the viscous friction losses at the tooth tip gap, at the bearing blocks-gears gaps, at the journal bearings, and the meshing loss. To calculate the shear stress at each gap interface, the geometry of the gap has to be known. For this reason, the actual position of the gears inside the pump casing and consequent radial pressure distribution are numerically calculated to evaluate the gap height at the tooth tips. Moreover, the variation of the tilt and reference height of the lateral gaps between the gears and the pump bushings are considered. The shear stresses within the lateral gaps are estimated, for different lateral heights and tilt values. At the journal bearings gaps, the half Sommerfeld solution has been applied. The meshing loss has been calculated according to the...
This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured ... more This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured with MC3T3 osteoblasts in response to flow-induced shear stress (FSS). The scaffold adopted here (B-HA) derives from the biomorphic transformation of natural wood and its peculiar channel geometry mimics the porous structure of the bone. From the point of view of fluid dynamics, B-HA can be considered a network of micro-channels, intrinsically offering the advantages of a microfluidic system. This work, for the first time, offers a description of the fluid dynamic properties of the B-HA scaffold, which are strongly connected to its morphology. These features are necessary to determine the FSS ranges to be applied during in vitro studies to get physiologically relevant conditions. The selected ranges of FSS promoted the elongation of the attached cells along the flow direction and early osteogenic cell differentiation. These data confirmed the ability of B-HA to promote the differentiatio...
<jats:p>Hydraulic pressure amplifiers of the cylinder type are much appreciated in hydrauli... more <jats:p>Hydraulic pressure amplifiers of the cylinder type are much appreciated in hydraulic systems where high pressure work is needed only for a limited period of time, while during the remaining duty cycle the system operates at a standard level of pressure. The use of these elements allows the designer not to oversize the system, which will perform the work with a considerable power saving, confining the high pressure operation only on the side of the hydraulic cylinder.</jats:p> <jats:p>This works describes the modelling and simulation of a compact cartridge pressure amplifier for linear actuators. The cartridge amplifier is able to double or more the pressure in the system when needed and to not interfere during normal operation of the system. It has been designed to fit in the narrow space of the rod of normal hydraulic cylinder, being extremely compact and efficient. Designing such a component and the study of the main design parameters influence have required a strong work of modelling and simulation, performed with a lumped parameters approach to depict the dynamic behaviour of the amplifier. This work illustrates the building of the model and a first comparison between simulated and experimental data. Moreover, the simulation activity is enlarged to analysis of the influence of some operating and design parameters on the amplifier dynamic behavior.</jats:p>
This work aims to analyze a complete hydraulic system of a medium size agricultural tractor, in o... more This work aims to analyze a complete hydraulic system of a medium size agricultural tractor, in order to perform an energy dissipation analysis and to suggest possibly alternative configurations and solutions. The fuel consumption and energy dissipation in off road vehicles have in fact become a key feature, given the great attention devoted to the need of reducing pollutant emissions, in order to satisfy the future emission limits. In this work the focus is on the fluid power supply group and the standard architecture of this unit has been compared with an alternative solution, called variable pump margin strategy and compared on the basis of the power consumption to perform the same duty cycle, showing that a relevant percentage of energy may be saved with simple modifications in the hydraulic power generator group.
In questo lavoro si descrive la metodologia utilizzata per caratterizzare una parte del circuito ... more In questo lavoro si descrive la metodologia utilizzata per caratterizzare una parte del circuito idraulico di una trattrice agricola. Lo scopo dell\u2019attivit\ue0 \ue8 stato quello di ricavare informazioni necessarie alla definizione delle caratteristiche di regolazione della parte di circuito analizzata da utilizzare successivamente in un modello di simulazione del circuito stesso con il quale replicare poi in un ambiente virtuale le effettive condizioni di lavoro incontrate dal veicolo durante le lavorazioni
The paper describes the influence of the fluid modeling on cavitation and aeration detection in e... more The paper describes the influence of the fluid modeling on cavitation and aeration detection in external gear pumps and motors inter-teeth volumes during the gears meshing process, in order to compare the results coming from the use of different physical models of air release/adsorption and cavitation. A simplified cavitation model is firstly involved, and pressure transients are calculated imposing a pressure cut when the fluid vapor pressure (or the dissolved air partial pressure) is reached. After, assuming an equivalent approach able to involve the vapor phase generation, the cavitation phenomena in the meshing volumes are deepened, and the influence of the fluid modeling enhancement on the cavitating machine behavior is highlighted. Then, the equivalent fluid approach is enhanced introducing the air release, and properly coupling the gaseous phases release/adsorption to the Henry's Law for not instantaneous processes. Finally, the influence of the air release/adsorption tim...
This paper studies the proportional directional controlvalves design influence on the energetic b... more This paper studies the proportional directional controlvalves design influence on the energetic behavior of amid-power compact excavator.In particular, with reference to the hydraulic circuitactuating the primary workgroup, in the paper thehydraulic power metering performed with the boomcylinder proportional control valve is studied, and somedesign solution useful in reducing both the hydraulicpower dissipation, and the power absorption from themachinery prime mover are highlighted.The analysis, experimentally performed for differentoperating conditions, is carried out highlighting theinfluence of a metering configuration both on the supplypressure modulation and on the flow-rate supplied tothe actuator.The hydraulic power metering and the boom actuationhydraulic efficiency are defined for two alternativeproportional control valve metering configurations and,within the limits implicitly implied on the actuation circuitarchitecture, a possible design solution in determiningthe improvement of the boom actuation systemperformances is investigated
In this paper some design aspects related to externalgear pumps balancing surfaces are studied, a... more In this paper some design aspects related to externalgear pumps balancing surfaces are studied, and someuseful guidelines for designing bearing blocksbalancing surfaces are suggested. In order to studybearing blocks axial balance, a numerical procedurefor the determination of the pressure distribution insidethe clearance bounded by gears sides and bearingblocks internal surfaces is firstly presented andapplied. After, the influence of bearing blocksgeometry and pump operating conditions on thewidening thrust is highlighted, considering bothconstant and variable lateral clearance heights. Then,the computations are performed to evaluate thewidening thrust variation as a function of bearingblocks relative tilt with respect to gears lateral sides,and both positive and negative bearing blocks tilts areevidenced and discussed. Finally, the numericalprocedure is validated through a comprehensivecomparison of its results with experimental data(coming from some bibliographic sources), and someuseful guidelines in designing external gear pumpsbalancing surfaces are defined
In this paper a lumped parameters numerical model isreviewed to study the meshing process of exte... more In this paper a lumped parameters numerical model isreviewed to study the meshing process of external gearpumps and motors, with the aim of highlighting theinfluence of some geometrical design parameters andoperating conditions on inter-teeth volumes pressures.The inter-teeth space is modeled adopting a two-volumeapproach, properly tailored both for the pump and for themotor units behavior description. In both cases, thecommunications between the interconnected inter-teethvolumes and the high and low pressure ports aresketched as variable equivalent turbulent restrictors; flowareas have been determined as functions of the gearsand of the meshing grooves main design parameters.The inter-teeth pressures, and the leakage flows, arecalculated solving the incompressible and isothermalcontinuity equation, contemporarily applied to bothvolumes and properly combined with the classicalturbulent orifice equation. Successively, for a referenceoperating condition, properly chosen for underlining theinter-teeth meshing cycle and corresponding to a verylow pressure load, the meshing processes of an externalgear pump and of an external gear motor are compared.Among others, the attention is focused on the behaviorof those hydraulic variables more conditioning themeshing cycle, and the differences rising up in interteethpressure peaks and in cavitation interval amplitudeand angular positioning are evidenced. Then, themeshing process analysis is expanded to cover theexternal gear units common operating field, both interms of rotational speed (from 500 to 3000 rpm) and interms of the high pressure port value (from 10 to 250bar). In all cases, the general trend shows that cavitationhas a deeper influence on external gear pumpsoperation, while external gear motors are subjected tomore significant pressure peaks, particularly markedduring the low pressure part of the meshing cycle.Attention is also focused on the influence of gears interaxialdistance and axial width on the meshing processcharacteristics, in order to assess how the volumedimensions could differently affect pressure peaks andcavitation phenomena in pumps and motors.Finally, the role of the balancing plates grooves inconditioning pressure peaks and cavitation is highlightedand, with particular care devoted to external gearmotors, some useful guidelines for their design areoutlined
The paper deals with the analysis of the inter-teeth pressure transients during gears meshing cyc... more The paper deals with the analysis of the inter-teeth pressure transients during gears meshing cycle of external gear pumps. A lumped parameter model, tailored for the prediction of pressures in the meshing zone, is firstly presented. The numerical model, based on the integration of the continuity equation, is applied to the inter-teeth volumes, communicating with the neighbouring ambient through geometry dependent orifices. A comparison between numerical results, obtained considering both constant and variable discharge coefficients, is illustrated. Successively, the dependency of pressure transients on gear pump operating conditions, mainly in terms of delivery pressure and rotational speed, is investigated. The effect of some geometric parameters is also discussed, mainly considering different gears widths and interaxial distances, and high-pressure recess positioning. Finally, in order to highlight the influence of the cavitation modelling on low pressure transition, the results coming from the application of two simplified approaches are shown and compared
External gear pumps and motors are robust and low cost components and are widely used in industri... more External gear pumps and motors are robust and low cost components and are widely used in industrial and mobile applications; nowadays however, optimal global efficiency represents a more crucial aspect to be considered when designing a hydraulic machine. For this reason, it becomes a primary necessity to investigate the phenomena which determine and affect the hydraulic machine total efficiency.In this work, the volumetric efficiency of external gear pumps is investigated by means of a mathematical model already presented in a previous paper and the results obtained are compared with experimental data.First of all, the mathematical model is briefly presented; then the predicted results are discussed considering the influence of the pump operating conditions. Moreover, the influence on the volumetric efficiency of the behaviour of the hydraulically balanced bearing blocks, and hence of the pump axial balance, is exposed. In particular, it is shown that the tilted position of the bearing blocks and the height of the lateral clearance can greatly affect the volumetric efficiency.The data coming from an experimental investigation carried out on commercial external gear pump units are then presented; both the volumetric and the mechanical efficiency have been measured.The comparison between the experimental data and the numerical results allows discussing the bearing blocks balancing behaviour during pump operation
This work aims to analyse a complete hydraulic system of a medium size agricultural tractor, in o... more This work aims to analyse a complete hydraulic system of a medium size agricultural tractor, in order to perform an energy dissipation analysis and to test possible alternative configurations and solutions. The fuel consumption and energy dissipation in off-road vehicles have infact become a key feature, given the great attention devoted to the need of reducing pollutant emissions, in order to satisfy the future emission limits. Standard and alternative architecture configurations are modelled and compared on the basis of the power consumption to perform the same duty cycle. Among the results, it is worth highlighting that a relevant percentage of energy may be saved with simple modifications in the hydraulic power generation group.
In the hydraulic servo-cylinders design, the circumferential grooves are used in order to reduce ... more In the hydraulic servo-cylinders design, the circumferential grooves are used in order to reduce the effect of the locking force. This force arises as a consequence to the distribution of pressure around the piston, when both an eccentric position, caused by the load on the piston, and the manufacturing defects on the piston and cylinder surfaces are present. In this work an approach is presented for the calculation of the contribution of the grooves in the definition of the locking force and of the leakage flow rate. The mathematical model proposed is based on the Reynolds equation, properly combined with the continuity equation applied within the grooves. The results of the analysis are combined together with the ones coming from the analysis at the hydrostatic bearings at the rod ends, which have been analyzed on a previous step of the research. A numerical procedure is then created that, with the appropriate input, allows to study the different design configurations of the servo...
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Papers by Barbara ZARDIN