Pub Date : 2019-05-21DOI: 10.3389/fmech.2019.00027
Grahame Douglas, Yaping He
In this article, a risk based approach to design for bushfire protection in view of adaptation to global warming is discussed. The concept of design bushfire is explained in an analogy to design flood or design earthquake in terms of event of prescribed return period. In lieu of using the Global Climate Model, the current study is based on the analysis of historical fire weather data from multiple locations in a state wide region. The generalized extreme value (GEV) analysis method is employed to establish the recurrence models for predicting the fire weather index of given return period and the associated fire intensity. To examine the impacts of the climate change, a moving GEV method is utilized to the weather data records over the period of 44 years. The result demonstrated a heterogeneity in the impact of climate change in terms of potential bushfire severity over the region studied. The implication of this outcome is that the traditional prescriptive approach to design for bushfire protection may not be suited for adaptation to climate change.
{"title":"Design Bushfire Selection for Bushfire Protection in Adaptation to Global Warming","authors":"Grahame Douglas, Yaping He","doi":"10.3389/fmech.2019.00027","DOIUrl":"https://doi.org/10.3389/fmech.2019.00027","url":null,"abstract":"In this article, a risk based approach to design for bushfire protection in view of adaptation to global warming is discussed. The concept of design bushfire is explained in an analogy to design flood or design earthquake in terms of event of prescribed return period. In lieu of using the Global Climate Model, the current study is based on the analysis of historical fire weather data from multiple locations in a state wide region. The generalized extreme value (GEV) analysis method is employed to establish the recurrence models for predicting the fire weather index of given return period and the associated fire intensity. To examine the impacts of the climate change, a moving GEV method is utilized to the weather data records over the period of 44 years. The result demonstrated a heterogeneity in the impact of climate change in terms of potential bushfire severity over the region studied. The implication of this outcome is that the traditional prescriptive approach to design for bushfire protection may not be suited for adaptation to climate change.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"4 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83697319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-16DOI: 10.3389/fmech.2019.00023
J. Streator
A generic model has been developed to simulate the effect of phonon interactions during nanoscale sliding with an incommensurate interface. A rigid slider or array of sliders is translated across a 3D elastic slab whose mass elements are harmonically coupled, either in a simple cubic structure (for vast majority of cases) or in a face-centered cubic structure Each slider interacts with the slab via the Lennard-Jones 6-12 intermolecular potential. Elastic waves are allowed to propagate without any damping and no energy is removed from the system. Boundary conditions are set sufficiently remotely that no significant wave energy returns to the interface from boundary reflection. Simulation results demonstrate that for such nanoscale contacts, (1) the presence of one slider can affect the friction felt by another slider through phonon generation; (2) friction force scales with contact width rather than with contact area and (3) the friction force may be sensitive to the number of contact regions that comprise a given total area.
{"title":"Nanoscale Friction: Phonon Contributions for Single and Multiple Contacts","authors":"J. Streator","doi":"10.3389/fmech.2019.00023","DOIUrl":"https://doi.org/10.3389/fmech.2019.00023","url":null,"abstract":"A generic model has been developed to simulate the effect of phonon interactions during nanoscale sliding with an incommensurate interface. A rigid slider or array of sliders is translated across a 3D elastic slab whose mass elements are harmonically coupled, either in a simple cubic structure (for vast majority of cases) or in a face-centered cubic structure Each slider interacts with the slab via the Lennard-Jones 6-12 intermolecular potential. Elastic waves are allowed to propagate without any damping and no energy is removed from the system. Boundary conditions are set sufficiently remotely that no significant wave energy returns to the interface from boundary reflection. Simulation results demonstrate that for such nanoscale contacts, (1) the presence of one slider can affect the friction felt by another slider through phonon generation; (2) friction force scales with contact width rather than with contact area and (3) the friction force may be sensitive to the number of contact regions that comprise a given total area.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"25 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74376822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-14DOI: 10.3389/fmech.2019.00024
F. Borodich, E. Brousseau, A. Clarke, A. Pepelyshev, J. C. Sánchez-López
Topography of surfaces may influence many processes in tribology including friction and adhesion. Its influence is usually taken into account in various statistical models of rough surfaces. Most of these models are based on an explicit or implicit assumption of normality of the asperity heights or similar assumptions that involve Gaussian distributions. Recently it has been shown that the height distribution of surfaces prepared by grinding are not Gaussian at both nano and micro-scales, while topography of epoxy resin replicas of polishing papers having nominal asperity sizes up to several micrometers, was Gaussian. Here we study roughness of carbon-based coatings deposited by direct current pulsed magnetron sputtering with and without substrate bias voltage at micro and nano-scale. First the heights of the nano-asperities were determined by AFM (Atomic Force Microscopy). Then the heights of the micro-asperities were measured by a profilometre (a stylus). Finally the same regions measured by stylus were again studied by AFM. Standard statistical parameters of surfaces are determined at each scale. It has been also shown that the stylus measurements did not cause plastic deformations because the distributions of heights at nano-scale were the same. Using the experimental data obtained, the assumption of the normal distribution for the roughness heights has been studied by application of various modern tests of normality. It was found that the surfaces satisfy the assumption of normality of the heights at both levels. Hence, some of the standard statistical models of contact between rough solids can be applied to these intact surfaces.
{"title":"Roughness of Deposited Carbon-Based Coatings and Its Statistical Characteristics at Nano and Microscales","authors":"F. Borodich, E. Brousseau, A. Clarke, A. Pepelyshev, J. C. Sánchez-López","doi":"10.3389/fmech.2019.00024","DOIUrl":"https://doi.org/10.3389/fmech.2019.00024","url":null,"abstract":"Topography of surfaces may influence many processes in tribology including friction and adhesion. Its influence is usually taken into account in various statistical models of rough surfaces. Most of these models are based on an explicit or implicit assumption of normality of the asperity heights or similar assumptions that involve Gaussian distributions. Recently it has been shown that the height distribution of surfaces prepared by grinding are not Gaussian at both nano and micro-scales, while topography of epoxy resin replicas of polishing papers having nominal asperity sizes up to several micrometers, was Gaussian. Here we study roughness of carbon-based coatings deposited by direct current pulsed magnetron sputtering with and without substrate bias voltage at micro and nano-scale. First the heights of the nano-asperities were determined by AFM (Atomic Force Microscopy). Then the heights of the micro-asperities were measured by a profilometre (a stylus). Finally the same regions measured by stylus were again studied by AFM. Standard statistical parameters of surfaces are determined at each scale. It has been also shown that the stylus measurements did not cause plastic deformations because the distributions of heights at nano-scale were the same. Using the experimental data obtained, the assumption of the normal distribution for the roughness heights has been studied by application of various modern tests of normality. It was found that the surfaces satisfy the assumption of normality of the heights at both levels. Hence, some of the standard statistical models of contact between rough solids can be applied to these intact surfaces.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"64 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78781919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-13DOI: 10.3389/fmech.2019.00025
I. Brahma
An assumption of constant discharge coefficient (Cd) is often made when modeling highly compressible pulsating engine flows through valves or other restrictions. Similarly, orifices and flow nozzles used for real-time EGR flow estimation are often calibrated at a few steady-state points with one single constant Cd that minimizes the error over the selected points. This assumption is based on near constant Cd observed at high Reynolds number for steady flow. It has been shown in this work that this assumption is not reasonable for pulsating flow, particularly at large amplitudes and low flow rates. The discharge coefficient of a square-edged orifice placed in the exhaust stream of a diesel engine produced Cd’s varying between 0.60-0.90 for the resulting critical/near-critical flows. A novel pulsating flow measurement apparatus that allowed independent variation of pressure, flow rate and frequency and allowed reproducible measurements independent of transducer characteristics, produced Cd’s in the range of 0.25-0.60 with a similar square-edge orifice. The variation in Cd was characterized by two dimensionless variables that normalized the standard deviation of the pulsating signal with dynamic pressure and average differential pressure drop respectively. The results raise important questions that can potentially initiate fundamental work to fill the gap in the literature that exists for highly compressible pulsating flows.
{"title":"Measurement and Prediction of Discharge Coefficients in Highly Compressible Pulsating Flows to Improve EGR Flow Estimation and Modeling of Engine Flows","authors":"I. Brahma","doi":"10.3389/fmech.2019.00025","DOIUrl":"https://doi.org/10.3389/fmech.2019.00025","url":null,"abstract":"An assumption of constant discharge coefficient (Cd) is often made when modeling highly compressible pulsating engine flows through valves or other restrictions. Similarly, orifices and flow nozzles used for real-time EGR flow estimation are often calibrated at a few steady-state points with one single constant Cd that minimizes the error over the selected points. This assumption is based on near constant Cd observed at high Reynolds number for steady flow. It has been shown in this work that this assumption is not reasonable for pulsating flow, particularly at large amplitudes and low flow rates. The discharge coefficient of a square-edged orifice placed in the exhaust stream of a diesel engine produced Cd’s varying between 0.60-0.90 for the resulting critical/near-critical flows. A novel pulsating flow measurement apparatus that allowed independent variation of pressure, flow rate and frequency and allowed reproducible measurements independent of transducer characteristics, produced Cd’s in the range of 0.25-0.60 with a similar square-edge orifice. The variation in Cd was characterized by two dimensionless variables that normalized the standard deviation of the pulsating signal with dynamic pressure and average differential pressure drop respectively. The results raise important questions that can potentially initiate fundamental work to fill the gap in the literature that exists for highly compressible pulsating flows.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"126 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77076043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-09DOI: 10.3389/fmech.2019.00026
E. Torskaya, F. Stepanov
Sliding contact of a smooth indenter and a two-layered half-space is considered taking into account rheological properties of materials. The case of a viscoelastic layer bonded with a rigid half-space is analyzed as well as an opposite one, which is viscoelastic half-space covered by rigid layer. The problem is formulated as quasi-static. Numerical-analytical method of solution is based on boundary element method and iteration procedure. New analytical solution is used to calculate influence coefficients for the computation procedure. Contact pressure, energy dissipation and internal stresses are analyzed in dependence on sliding velocity, layer thickness and Poisson's ratio.
{"title":"Effect of Surface Layers in Sliding Contact of Viscoelastic Solids (3-D Model of Material)","authors":"E. Torskaya, F. Stepanov","doi":"10.3389/fmech.2019.00026","DOIUrl":"https://doi.org/10.3389/fmech.2019.00026","url":null,"abstract":"Sliding contact of a smooth indenter and a two-layered half-space is considered taking into account rheological properties of materials. The case of a viscoelastic layer bonded with a rigid half-space is analyzed as well as an opposite one, which is viscoelastic half-space covered by rigid layer. The problem is formulated as quasi-static. Numerical-analytical method of solution is based on boundary element method and iteration procedure. New analytical solution is used to calculate influence coefficients for the computation procedure. Contact pressure, energy dissipation and internal stresses are analyzed in dependence on sliding velocity, layer thickness and Poisson's ratio.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78123706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-07DOI: 10.3389/fmech.2019.00021
S. Yang, M. Jia
Biodiesel is a renewable, clean-burning diesel replacement, and may have superior brake thermal efficiency with certain blends compared to traditional diesel counterpart at higher compression ratios. The combustion chemistry process of biodiesel, which has not been well understood, is of great interests to some engine researchers. Researchers have developed some complicated chemical kinetic mechanisms for bio-diesel, which cannot be used in engine CFD with current computational resources. The present work aims to construct a new chemical kinetic mechanism with a medium size for biodiesel combustion. Since 2016, H2/O2/CO/C1 and C2-C3 detailed sub-mechanisms (the C3 model contained in AramcoMech2.0) have been developed for accurately predicting laminar flame speeds, ignition delay times, and important species evolutions, and have been validated against a large array of experimental measurements over a wide range of conditions. In this paper, a 3-component biodiesel surrogate chemical kinetic mechanism constructed in 2015 based on decoupling methodology has been combined with the new ‘core’ H2/O2/CO/C1~C3 detailed mechanism to generate a new bio-diesel chemical kinetic mechanism. In the surrogate mechanism construction, three skeletal sub-mechanisms are used for the three biodiesel components (MD, MD5D, and n-decane). The final mechanism, which has 183 species and 1002 reactions, has been validated with available experiment data. It will be validated extensively with more experimental biodiesel data and applied to engine CFD for understanding biodiesel combustion.
{"title":"A Bio-Diesel Chemical Kinetic Mechanism Based on Decoupling Methodology and Detailed H2/O2/CO/C1~C3 Mechanism","authors":"S. Yang, M. Jia","doi":"10.3389/fmech.2019.00021","DOIUrl":"https://doi.org/10.3389/fmech.2019.00021","url":null,"abstract":"Biodiesel is a renewable, clean-burning diesel replacement, and may have superior brake thermal efficiency with certain blends compared to traditional diesel counterpart at higher compression ratios. The combustion chemistry process of biodiesel, which has not been well understood, is of great interests to some engine researchers. Researchers have developed some complicated chemical kinetic mechanisms for bio-diesel, which cannot be used in engine CFD with current computational resources. The present work aims to construct a new chemical kinetic mechanism with a medium size for biodiesel combustion. Since 2016, H2/O2/CO/C1 and C2-C3 detailed sub-mechanisms (the C3 model contained in AramcoMech2.0) have been developed for accurately predicting laminar flame speeds, ignition delay times, and important species evolutions, and have been validated against a large array of experimental measurements over a wide range of conditions. In this paper, a 3-component biodiesel surrogate chemical kinetic mechanism constructed in 2015 based on decoupling methodology has been combined with the new ‘core’ H2/O2/CO/C1~C3 detailed mechanism to generate a new bio-diesel chemical kinetic mechanism. In the surrogate mechanism construction, three skeletal sub-mechanisms are used for the three biodiesel components (MD, MD5D, and n-decane). The final mechanism, which has 183 species and 1002 reactions, has been validated with available experiment data. It will be validated extensively with more experimental biodiesel data and applied to engine CFD for understanding biodiesel combustion.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"219 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76920274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-03DOI: 10.3389/fmech.2019.00020
Chris van Dronkelaar, M. Dowson, C. Spataru, E. Burman, D. Mumovic
Simulation is commonly utilised as a best practice approach to assess building performance in the building industry. However, the built environment is complex and influenced by a large number of independent and interdependent variables, making it difficult to achieve an accurate representation of real-world building energy in-use. This gives rise to significant discrepancies between simulation results and actual measured energy consumption, termed ‘the performance gap’. The research presented in this paper quantified the impact of underlying causes of this gap, by developing building simulation models of four existing non-domestic buildings, and then calibrating them towards their measured energy use at a high level of data granularity. It found that discrepancies were primarily related to night-time use and seasonality in universities is not being captured correctly, in addition to equipment and server power density being underestimated (indirectly impacting heating and cooling loads). Less impactful parameters were among others; material properties, system efficiencies and air infiltration assumptions.
{"title":"Quantifying the Underlying Causes of a Discrepancy Between Predicted and Measured Energy Use","authors":"Chris van Dronkelaar, M. Dowson, C. Spataru, E. Burman, D. Mumovic","doi":"10.3389/fmech.2019.00020","DOIUrl":"https://doi.org/10.3389/fmech.2019.00020","url":null,"abstract":"Simulation is commonly utilised as a best practice approach to assess building performance in the building industry. However, the built environment is complex and influenced by a large number of independent and interdependent variables, making it difficult to achieve an accurate representation of real-world building energy in-use. This gives rise to significant discrepancies between simulation results and actual measured energy consumption, termed ‘the performance gap’. The research presented in this paper quantified the impact of underlying causes of this gap, by developing building simulation models of four existing non-domestic buildings, and then calibrating them towards their measured energy use at a high level of data granularity. It found that discrepancies were primarily related to night-time use and seasonality in universities is not being captured correctly, in addition to equipment and server power density being underestimated (indirectly impacting heating and cooling loads). Less impactful parameters were among others; material properties, system efficiencies and air infiltration assumptions.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"44 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3389/fmech.2019.00020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72368083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-01DOI: 10.3389/fmech.2019.00018
B. LotfizadehDehkordi, P. Shiller, G. Doll
The pressure–viscosity coefficient, α, is a measure of the pressure dependence of the viscosity of the liquid in elastohydrodynamic lubrication (EHL). There seems to be confusion around the understanding of the pressure–viscosity response in the inlet zone. In this paper the values of α were obtained from measurements of viscosity as a function of pressure and offers a understanding on the piezoviscous effect at various inlet pressures for those liquids. Moreover, the viscosities of several commercial engine oils and laboratory blends of mineral and synthetic base oils with polymer additives were measured at pressures up to 1 GPa and at temperatures of 40°C, 75°C, and 100°C. It was observed in some of these materials The significant changes within viscosity are temperature- and pressure-dependent. Analysis of the experimental results indicated that the solidification (significant increase viscosity) is due to liquid-solid phase transitions occurring in the lubricant’s polymer additives. Thus, this paper gives evidence on the role of molecular weight and concentration of polymer and its influence on the pressure- and temperature-dependent onset of the phase transitions. This transition has not been discussed in the open literature and is not accounted for in current bearing design using the Barus equation or the modified Yasatomi equation and may be the cause of some bearing damage modes.
{"title":"Pressure- and Temperature-Dependent Viscosity Measurements of Lubricants With Polymeric Viscosity Modifiers","authors":"B. LotfizadehDehkordi, P. Shiller, G. Doll","doi":"10.3389/fmech.2019.00018","DOIUrl":"https://doi.org/10.3389/fmech.2019.00018","url":null,"abstract":"The pressure–viscosity coefficient, α, is a measure of the pressure dependence of the viscosity of the liquid in elastohydrodynamic lubrication (EHL). There seems to be confusion around the understanding of the pressure–viscosity response in the inlet zone. In this paper the values of α were obtained from measurements of viscosity as a function of pressure and offers a understanding on the piezoviscous effect at various inlet pressures for those liquids. Moreover, the viscosities of several commercial engine oils and laboratory blends of mineral and synthetic base oils with polymer additives were measured at pressures up to 1 GPa and at temperatures of 40°C, 75°C, and 100°C. It was observed in some of these materials The significant changes within viscosity are temperature- and pressure-dependent. Analysis of the experimental results indicated that the solidification (significant increase viscosity) is due to liquid-solid phase transitions occurring in the lubricant’s polymer additives. Thus, this paper gives evidence on the role of molecular weight and concentration of polymer and its influence on the pressure- and temperature-dependent onset of the phase transitions. This transition has not been discussed in the open literature and is not accounted for in current bearing design using the Barus equation or the modified Yasatomi equation and may be the cause of some bearing damage modes.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"192 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76967614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-30DOI: 10.3389/fmech.2019.00017
P. Mishra, Santosh Kumar
Piston subsystem is subjected to very complex but dynamic forces. Such forces include combustion gas force, inertial dynamics forces, lubricating action/damping forces, contact friction forces to name a few. Further, piston ring mounted in piston in addition to these forces experiences out ward springing action inside engine mounting due to inherent elasticity. To evaluate the strength of reciprocating piston, the simultaneous effect of all these forces should be considered, while simulating it through FEM. With effect of all these forces, the currently considered piston of Grey Cast Iron, Al-alloy and Metal-Metric-Composite (Si-C) are given four different crown shapes for optimization of material and crown geometry. The rings mounted are considered to be coated with Nickasil. The combined numerical simulation for contact and FEM simulation of structural strength and their correlation suggest many important outcomes.
{"title":"Modeling for Design Optimization of Piston Crown Geometry Through Structural Strength and Lubrication Performance Correlation Analysis","authors":"P. Mishra, Santosh Kumar","doi":"10.3389/fmech.2019.00017","DOIUrl":"https://doi.org/10.3389/fmech.2019.00017","url":null,"abstract":"Piston subsystem is subjected to very complex but dynamic forces. Such forces include combustion gas force, inertial dynamics forces, lubricating action/damping forces, contact friction forces to name a few. Further, piston ring mounted in piston in addition to these forces experiences out ward springing action inside engine mounting due to inherent elasticity. To evaluate the strength of reciprocating piston, the simultaneous effect of all these forces should be considered, while simulating it through FEM. With effect of all these forces, the currently considered piston of Grey Cast Iron, Al-alloy and Metal-Metric-Composite (Si-C) are given four different crown shapes for optimization of material and crown geometry. The rings mounted are considered to be coated with Nickasil. The combined numerical simulation for contact and FEM simulation of structural strength and their correlation suggest many important outcomes.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"58 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90623636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-18DOI: 10.3389/fmech.2019.00013
Azhar Vellore, Nicholas Walters, A. Martini
60NiTi is an intermetallic alloy of nickel and titanium that exhibits a unique combination of properties, including hardness comparable to steel, almost twice the elasticity of steel, high corrosion resistance, and tensile strength comparable to ceramics. These properties are very desirable for bearing materials, especially those used in space applications where components must operate efficiently and reliably in harsh conditions. However, despite the fact that most bearings are grease lubricated, there has not been a systematic study of the tribo-performance of greases for 60NiTi lubrication. To address this, we compare the wear and friction of self-mated 60NiTi lubricated by different greases, including those currently used in space missions and general-purpose grease, in boundary lubricated contact. The results provide valuable information to guide selection of grease for 60NiTi contacts as well as lay the groundwork for possible development of new greases specifically for 60NiTi tribo-contacts.
{"title":"Grease Lubrication of Self-Mated 60NiTi Bearing Materials","authors":"Azhar Vellore, Nicholas Walters, A. Martini","doi":"10.3389/fmech.2019.00013","DOIUrl":"https://doi.org/10.3389/fmech.2019.00013","url":null,"abstract":"60NiTi is an intermetallic alloy of nickel and titanium that exhibits a unique combination of properties, including hardness comparable to steel, almost twice the elasticity of steel, high corrosion resistance, and tensile strength comparable to ceramics. These properties are very desirable for bearing materials, especially those used in space applications where components must operate efficiently and reliably in harsh conditions. However, despite the fact that most bearings are grease lubricated, there has not been a systematic study of the tribo-performance of greases for 60NiTi lubrication. To address this, we compare the wear and friction of self-mated 60NiTi lubricated by different greases, including those currently used in space missions and general-purpose grease, in boundary lubricated contact. The results provide valuable information to guide selection of grease for 60NiTi contacts as well as lay the groundwork for possible development of new greases specifically for 60NiTi tribo-contacts.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"87 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85436648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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