The recent supercritical CO2 power turbine configuration development introduced a cooling zone parametric model to overcome the existing technical challenges. The parametric model is the annulus cooling passage with a supercritical CO2 coolant consisting of radial clearance, length, and shaft diameter are the geometrical parameter. This study aims to investigate the pressure profile and stiffness coefficient of the cooling passage using computational fluid dynamics (CFD) and to explore the validity of the assumptions that exist in the simplified analysis. The effect of eccentricity ratio, shaft speed, and axial length are investigated. The result showed that, like the hydrodynamic bearing, the supercritical CO2 swirling in the annulus passage produces substantial mechanical support on the shaft. Hence, the cooling zone stiffness contribution should be included in the supercritical CO2 turbine shaft vibration analysis which is not presently taken into consideration.
{"title":"Pressure Profile and Stiffness Analysis of Supercritical CO2 Inside a Rotating Annulus Cooling Passage Using CFD","authors":"M. Uddin, Professor Halim Gurgenci, Zhiqiang Guan","doi":"10.1115/1.4062812","DOIUrl":"https://doi.org/10.1115/1.4062812","url":null,"abstract":"\u0000 The recent supercritical CO2 power turbine configuration development introduced a cooling zone parametric model to overcome the existing technical challenges. The parametric model is the annulus cooling passage with a supercritical CO2 coolant consisting of radial clearance, length, and shaft diameter are the geometrical parameter. This study aims to investigate the pressure profile and stiffness coefficient of the cooling passage using computational fluid dynamics (CFD) and to explore the validity of the assumptions that exist in the simplified analysis. The effect of eccentricity ratio, shaft speed, and axial length are investigated. The result showed that, like the hydrodynamic bearing, the supercritical CO2 swirling in the annulus passage produces substantial mechanical support on the shaft. Hence, the cooling zone stiffness contribution should be included in the supercritical CO2 turbine shaft vibration analysis which is not presently taken into consideration.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42306977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gregory R. Roytman, Jocelyn Faydenko, Matthew Budavich, Judith D. Pocius, Gregory David Cramer
Crepitus vibrational and acoustic signal analysis of the human facet joints of the lumbar spine has historically been a difficult problem due to the inhomogeneous and varied signal characteristics. Here we improve upon our previous automated computational method, now enhancing it for analysis of human crepitus. Compared with this group's previous studies using a mechanical model; human crepitus is extremely complex. Moreover, there is no existing availability of large numbers of human crepitus data to enable effective machine learning approaches. Therefore, we proposed an automated method (AM) of analysis that, analogous to machine learning, used a test set (n = 16) and an experimental set of data (n = 48). The advantage of beginning with this approach was that we identified characteristics of the signal that are unavailable or otherwise not easily obtained in more advanced methods, such as “black box” machine learning methods. However, we did not have the high fidelity that a machine learning approach would provide. This was shown by only a fair level of inter-rater agreement (Kw = 0.367; SE = 0.054, 95% CI = 0.260-0.474) between the AM and human observers before adjustments were made in the AM. Following adjustments to the AM, inter-rater agreement improved to a substantial level of agreement (Kw = 0.788; SE = 0.056, 95% CI = 0.0.682-0.895). In the future, we recommend a machine learning study with a high number of subjects, that can better capture the nuances of varying types of human crepitus.
{"title":"Automated Vibration and Acoustic Crepitus Sensing in Humans","authors":"Gregory R. Roytman, Jocelyn Faydenko, Matthew Budavich, Judith D. Pocius, Gregory David Cramer","doi":"10.1115/1.4062808","DOIUrl":"https://doi.org/10.1115/1.4062808","url":null,"abstract":"\u0000 Crepitus vibrational and acoustic signal analysis of the human facet joints of the lumbar spine has historically been a difficult problem due to the inhomogeneous and varied signal characteristics. Here we improve upon our previous automated computational method, now enhancing it for analysis of human crepitus. Compared with this group's previous studies using a mechanical model; human crepitus is extremely complex. Moreover, there is no existing availability of large numbers of human crepitus data to enable effective machine learning approaches. Therefore, we proposed an automated method (AM) of analysis that, analogous to machine learning, used a test set (n = 16) and an experimental set of data (n = 48). The advantage of beginning with this approach was that we identified characteristics of the signal that are unavailable or otherwise not easily obtained in more advanced methods, such as “black box” machine learning methods. However, we did not have the high fidelity that a machine learning approach would provide. This was shown by only a fair level of inter-rater agreement (Kw = 0.367; SE = 0.054, 95% CI = 0.260-0.474) between the AM and human observers before adjustments were made in the AM. Following adjustments to the AM, inter-rater agreement improved to a substantial level of agreement (Kw = 0.788; SE = 0.056, 95% CI = 0.0.682-0.895). In the future, we recommend a machine learning study with a high number of subjects, that can better capture the nuances of varying types of human crepitus.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42477138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The tribological performance of scrolls lubricated with CO2/oil mixture is investigated using a combination of the mixed lubrication model and homogeneous model. The physical characteristics of the CO2/oil mixture were established prior to using the lubrication model. Then the evolution of the lubrication condition during the meshing process of scrolls was investigated, and the impact of radial clearance and refrigerant on the tribological behavior was assessed. The lubrication condition of the tribo-pair deteriorates as the meshing point moves toward the center of the scrolls. The effects of radial clearance and refrigerant mass fraction on friction and lubrication are strongly influenced by the meshing position. In addition, the presence of refrigerant leads to less hydrodynamic pressure and more asperity contact.
{"title":"Mixed lubrication analysis of scrolls lubricated with CO2/oil mixture based on a homogeneous model","authors":"Chunjie Wei, Hui Song, Z. Hu, Wei Wang","doi":"10.1115/1.4062690","DOIUrl":"https://doi.org/10.1115/1.4062690","url":null,"abstract":"\u0000 The tribological performance of scrolls lubricated with CO2/oil mixture is investigated using a combination of the mixed lubrication model and homogeneous model. The physical characteristics of the CO2/oil mixture were established prior to using the lubrication model. Then the evolution of the lubrication condition during the meshing process of scrolls was investigated, and the impact of radial clearance and refrigerant on the tribological behavior was assessed. The lubrication condition of the tribo-pair deteriorates as the meshing point moves toward the center of the scrolls. The effects of radial clearance and refrigerant mass fraction on friction and lubrication are strongly influenced by the meshing position. In addition, the presence of refrigerant leads to less hydrodynamic pressure and more asperity contact.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44213966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Prashant H. Jain, S. Bhosle, A. Keche, R. Desavale
In this study, the effects of the evolution of bearing outer race defect size and increase in speed on the vibration characteristics of a shaft-bearing system under unbalanced conditions. The contact stiffness between the races and the balls is considered as a series of springs is also incorporated in the model. Hertzian contact deformation theory is used to obtain the contact stiffness. This model considers the contact deformation between the balls and the races, the additional displacement between the balls and the inner race due to radial clearance, and due to defect geometry. The maximum possible radial displacement of the ball into the defect is calculated analytically using the groove radius, ball radius and defect diameter. The rectangular function is used for modelling the defect. MATLAB codes are developed for modelling the shaft-bearing system and for solving the differential equations of motion using the Runge-Kutta method. The vibration responses obtained by modelling and by experimentation show similar vibration characteristics. The investigation shows that the values of statistical parameters initially increase with the increase in defect size and then decrease with a further increase in defect size. While peak and RMS increase with the speed and crest factor and kurtosis decrease with an increase in speed. Peak is more sensitive for diagnosing spalls on outer race and its evolution. This study helps as an effective diagnosis of antifriction bearings having spalls on the outer race under unbalanced conditions.
{"title":"A dynamic model of outer race defective bearing considering the unbalanced shaft-bearing system with experimental simulation","authors":"Prashant H. Jain, S. Bhosle, A. Keche, R. Desavale","doi":"10.1115/1.4062689","DOIUrl":"https://doi.org/10.1115/1.4062689","url":null,"abstract":"\u0000 In this study, the effects of the evolution of bearing outer race defect size and increase in speed on the vibration characteristics of a shaft-bearing system under unbalanced conditions. The contact stiffness between the races and the balls is considered as a series of springs is also incorporated in the model. Hertzian contact deformation theory is used to obtain the contact stiffness. This model considers the contact deformation between the balls and the races, the additional displacement between the balls and the inner race due to radial clearance, and due to defect geometry. The maximum possible radial displacement of the ball into the defect is calculated analytically using the groove radius, ball radius and defect diameter. The rectangular function is used for modelling the defect. MATLAB codes are developed for modelling the shaft-bearing system and for solving the differential equations of motion using the Runge-Kutta method. The vibration responses obtained by modelling and by experimentation show similar vibration characteristics. The investigation shows that the values of statistical parameters initially increase with the increase in defect size and then decrease with a further increase in defect size. While peak and RMS increase with the speed and crest factor and kurtosis decrease with an increase in speed. Peak is more sensitive for diagnosing spalls on outer race and its evolution. This study helps as an effective diagnosis of antifriction bearings having spalls on the outer race under unbalanced conditions.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":"1 10","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41276099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuangbiao Liu, Nicole H. Dorcy, Q. Wang, Y. Chung, S. Berkebile
Deterministic contact modeling based on half-space theories has satisfied a wide range of applications. However, the half-space theories themselves do not involve shape effects of roughness on Green's functions/influence coefficients; in deterministic rough-surface contact analyses, the roughness is considered in gap function. This approach can be called the “roughness simplification”. One needs to answer two questions about the validity of the roughness simplification: How appropriate is the roughness simplification in modeling rough-surface contacts? How accurate can the commonly-included contact-plasticity behavior be captured under the roughness simplification? This work utilized a double-scale representation of an asperity--a microscopic deformable asperity stacked on a deformable half-space, to obtain their combined contact responses in both elastic and plastic regimes. The deformation and contact behaviors of asperities thus configured were obtained with finite element method (FEA) and rough-surface half-space contact solvers. Three stages of asperity contact were discovered: the Hertzian stage, the single-region elastoplastic stage, and the two-region elastoplastic stage where the surrounding base material also takes part in the contact. The comparisons of contact deformation and pressure results from both the FEA and half-space contact solvers support the validity of the half-space theories with the roughness simplification for various ellipsoid-shape asperities with circular-bases in both elastic and elastoplastic rough-surface asperity modeling. The research also reveals that when significant plastic deformations occur, asperities with different aspect ratios can bear different maximum elastoplastic contact pressures.
{"title":"Contacting Micro Asperity of a Deformable Surface","authors":"Shuangbiao Liu, Nicole H. Dorcy, Q. Wang, Y. Chung, S. Berkebile","doi":"10.1115/1.4062576","DOIUrl":"https://doi.org/10.1115/1.4062576","url":null,"abstract":"\u0000 Deterministic contact modeling based on half-space theories has satisfied a wide range of applications. However, the half-space theories themselves do not involve shape effects of roughness on Green's functions/influence coefficients; in deterministic rough-surface contact analyses, the roughness is considered in gap function. This approach can be called the “roughness simplification”. One needs to answer two questions about the validity of the roughness simplification: How appropriate is the roughness simplification in modeling rough-surface contacts? How accurate can the commonly-included contact-plasticity behavior be captured under the roughness simplification? This work utilized a double-scale representation of an asperity--a microscopic deformable asperity stacked on a deformable half-space, to obtain their combined contact responses in both elastic and plastic regimes. The deformation and contact behaviors of asperities thus configured were obtained with finite element method (FEA) and rough-surface half-space contact solvers. Three stages of asperity contact were discovered: the Hertzian stage, the single-region elastoplastic stage, and the two-region elastoplastic stage where the surrounding base material also takes part in the contact. The comparisons of contact deformation and pressure results from both the FEA and half-space contact solvers support the validity of the half-space theories with the roughness simplification for various ellipsoid-shape asperities with circular-bases in both elastic and elastoplastic rough-surface asperity modeling. The research also reveals that when significant plastic deformations occur, asperities with different aspect ratios can bear different maximum elastoplastic contact pressures.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47414023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study's primary goal is to examine the effects of wear parameters and the wear rate (WR) of magnesium (AZ91) composites. The composites are made up of using stir casting process with aluminum oxide (Al2O3) and graphene as reinforcements. In the present work, one material factor (Material Type (MT)) and three tribological factors (load(L), velocity (V), and sliding distance (D)) were chosen to study their influence on the wear rate. Taguchi technique is employed for the design of experiments and it was observed that load (L) is the most influencing parameter on WR, followed by MT, D, and V. The optimal values of influencing parameters for WR are as follows: MT = T2, L = 10 N, V = 2 m/s, and D = 500 m. The wear mechanisms at the highest and lowest WR conditions were also studied by observing their SEM micrographs on wear pin's surface and its debris. From the SEM analysis, it was observed that abrasion, delamination, adhesion and oxidation mechanisms were exhibited on the wear surface. Machine learning (ML) models such as artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and decision tree (DT) were used to develop an effective prediction model to predict the output responses at the corresponding input variables. Confirmation tests were conducted under optimal conditions, and the same were examined with the results of ANN, ANFIS and DT. It was noticed that DT model exhibited higher accuracy when compared to other models considered in this study.
{"title":"Experimental investigation and Machine Learning modelling of wear characteristics of AZ91 composites","authors":"S. S. H. Kruthiventi, D. Ammisetti","doi":"10.1115/1.4062518","DOIUrl":"https://doi.org/10.1115/1.4062518","url":null,"abstract":"\u0000 This study's primary goal is to examine the effects of wear parameters and the wear rate (WR) of magnesium (AZ91) composites. The composites are made up of using stir casting process with aluminum oxide (Al2O3) and graphene as reinforcements. In the present work, one material factor (Material Type (MT)) and three tribological factors (load(L), velocity (V), and sliding distance (D)) were chosen to study their influence on the wear rate. Taguchi technique is employed for the design of experiments and it was observed that load (L) is the most influencing parameter on WR, followed by MT, D, and V. The optimal values of influencing parameters for WR are as follows: MT = T2, L = 10 N, V = 2 m/s, and D = 500 m. The wear mechanisms at the highest and lowest WR conditions were also studied by observing their SEM micrographs on wear pin's surface and its debris. From the SEM analysis, it was observed that abrasion, delamination, adhesion and oxidation mechanisms were exhibited on the wear surface. Machine learning (ML) models such as artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and decision tree (DT) were used to develop an effective prediction model to predict the output responses at the corresponding input variables. Confirmation tests were conducted under optimal conditions, and the same were examined with the results of ANN, ANFIS and DT. It was noticed that DT model exhibited higher accuracy when compared to other models considered in this study.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45787063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rui Zhou, Meng Li, Rongfeng Zhang, L. Liu, Jun Yang, Heng Liu, Yi Liu
Wear changes the contact state and contact stiffness of the interface between the ball and the outer raceway under operation of a deep groove ball bearing, resulting in the change of reflection coefficient of the interface. This paper describes a method based on ultrasonic reflection to assess the wear status of rolling element bearings. A deep groove ball bearing wear test was performed and the reflected pulses were collected with a linear ultrasonic probe mounted on the bearing outer ring. The results show as the wear intensity first increases and then decreases from running-in stage to steady wear period, the reflection coefficient of the interface between the outer raceway and ball shows the expected opposite trend. In addition, the ultrasonic measurement of wear state was verified by oil debris monitoring using on-line visual ferrography.
{"title":"Monitoring wear of a deep groove ball bearing using ultrasonic reflection","authors":"Rui Zhou, Meng Li, Rongfeng Zhang, L. Liu, Jun Yang, Heng Liu, Yi Liu","doi":"10.1115/1.4062516","DOIUrl":"https://doi.org/10.1115/1.4062516","url":null,"abstract":"\u0000 Wear changes the contact state and contact stiffness of the interface between the ball and the outer raceway under operation of a deep groove ball bearing, resulting in the change of reflection coefficient of the interface. This paper describes a method based on ultrasonic reflection to assess the wear status of rolling element bearings. A deep groove ball bearing wear test was performed and the reflected pulses were collected with a linear ultrasonic probe mounted on the bearing outer ring. The results show as the wear intensity first increases and then decreases from running-in stage to steady wear period, the reflection coefficient of the interface between the outer raceway and ball shows the expected opposite trend. In addition, the ultrasonic measurement of wear state was verified by oil debris monitoring using on-line visual ferrography.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43652101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Rafi, T. Satish Kumar, T. Thankachan, C. Selvan
In this research, AA2024 aluminum alloy-based surface composites was fabricated using ex-situ titanium boride particles (TiB2) as reinforcement using friction stir processing technique. Microstructural and mechanical variation with respect to addition of TiB2 onto AA2024 surface was studied and evaluated. Results proposed an increase in mechanical strength and hardness with respect to TiB2 addition when compared with the substrate metal. Dry sliding wear characteristics of aluminum surface composites at varying sliding distances (500m, 1000m, 1500m and 2000m) was analyzed using pin-on-disc apparatus. Wear resistance of developed surface composites improved comparatively with respect to substrate metal due to the combined effect of particle inclusion and friction stir processing. Characterization of worn out surface composites proposed that wear mechanism happens due to combination of abrasive and adhesive wear, while the major material removal happens due to abrasive wear.
{"title":"Synergistic Effect of FSP and TiB2 on Mechanical and Tribological Behavior of AA2024 Surface Composites","authors":"S. Rafi, T. Satish Kumar, T. Thankachan, C. Selvan","doi":"10.1115/1.4062517","DOIUrl":"https://doi.org/10.1115/1.4062517","url":null,"abstract":"\u0000 In this research, AA2024 aluminum alloy-based surface composites was fabricated using ex-situ titanium boride particles (TiB2) as reinforcement using friction stir processing technique. Microstructural and mechanical variation with respect to addition of TiB2 onto AA2024 surface was studied and evaluated. Results proposed an increase in mechanical strength and hardness with respect to TiB2 addition when compared with the substrate metal. Dry sliding wear characteristics of aluminum surface composites at varying sliding distances (500m, 1000m, 1500m and 2000m) was analyzed using pin-on-disc apparatus. Wear resistance of developed surface composites improved comparatively with respect to substrate metal due to the combined effect of particle inclusion and friction stir processing. Characterization of worn out surface composites proposed that wear mechanism happens due to combination of abrasive and adhesive wear, while the major material removal happens due to abrasive wear.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44971256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The friction characteristics of SUS440C-Si3N4 lubricated by PTFE under cryogenic environment have not been researched well. The lubrication mechanisms in such friction condition need to be clarified to improve the fidelity of performance modeling for ball bearings used in liquid rocket engine turbopumps. This research experimentally investigated the friction coefficient of bearing materials via PTFE lubrication under cryogenic environment to clarify the friction characteristics of cryogenic turbopump ball bearings. These experiments revealed the dependance of the contact pressure on the friction coefficient. By several analyses, it was found that lower friction and better wear-resistance characteristics were caused by PTFE film that strongly adhered on metal fluoride formed on the surface of SUS440C due to moderate friction energy.
{"title":"Friction Characteristics of SUS440C/Si3N4 Lubricated by Polytetrafluoroethylene under Cryogenic Environment","authors":"Hiromitsu Kakudo, S. Takada, T. Hirayama","doi":"10.1115/1.4062486","DOIUrl":"https://doi.org/10.1115/1.4062486","url":null,"abstract":"\u0000 The friction characteristics of SUS440C-Si3N4 lubricated by PTFE under cryogenic environment have not been researched well. The lubrication mechanisms in such friction condition need to be clarified to improve the fidelity of performance modeling for ball bearings used in liquid rocket engine turbopumps. This research experimentally investigated the friction coefficient of bearing materials via PTFE lubrication under cryogenic environment to clarify the friction characteristics of cryogenic turbopump ball bearings. These experiments revealed the dependance of the contact pressure on the friction coefficient. By several analyses, it was found that lower friction and better wear-resistance characteristics were caused by PTFE film that strongly adhered on metal fluoride formed on the surface of SUS440C due to moderate friction energy.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47355168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Subrata Barman, Kritesh Kumar Gupta, S. Kushari, S. Dey
This investigation presents the deterministic and stochastic responses of the journal bearing with two-layered porous bush. Pressure equations in the porous layers and modified Reynolds equations in the clearance region are governed by the finite difference method (FDM). Stochastic analysis based on Monte Carlo Simulation (MCS) is used to investigate the effect of random variation in input parameters caused by uncertain operating conditions, improper installations, and manufacturing imperfections. In order to enhance computational efficiency, this probabilistic study is conducted in conjunction with the machine learning model (ML) based on the Support Vector Machine (SVM) algorithm. The uncertainty in the bearing responses is presented in the form of the probability density function (PDF), considering both the independent and combined effect of the stochastically varied input parameters. Graphical illustration of the data-driven sensitivity represents the relative significance of each input parameter affecting the steady-state responses of the journal bearing with two-layered porous bush. The findings of the present study reveal that the stochastic variations in the input parameters have a profound influence on the operational characteristics of the porous bearing. The outcome of the present study will be helpful in deciding the operational regime of the porous bearing under the practically-relevant stochastic environment.
{"title":"Stochastic performance of journal bearing with two-layered porous bush- A machine learning approach","authors":"Subrata Barman, Kritesh Kumar Gupta, S. Kushari, S. Dey","doi":"10.1115/1.4062487","DOIUrl":"https://doi.org/10.1115/1.4062487","url":null,"abstract":"\u0000 This investigation presents the deterministic and stochastic responses of the journal bearing with two-layered porous bush. Pressure equations in the porous layers and modified Reynolds equations in the clearance region are governed by the finite difference method (FDM). Stochastic analysis based on Monte Carlo Simulation (MCS) is used to investigate the effect of random variation in input parameters caused by uncertain operating conditions, improper installations, and manufacturing imperfections. In order to enhance computational efficiency, this probabilistic study is conducted in conjunction with the machine learning model (ML) based on the Support Vector Machine (SVM) algorithm. The uncertainty in the bearing responses is presented in the form of the probability density function (PDF), considering both the independent and combined effect of the stochastically varied input parameters. Graphical illustration of the data-driven sensitivity represents the relative significance of each input parameter affecting the steady-state responses of the journal bearing with two-layered porous bush. The findings of the present study reveal that the stochastic variations in the input parameters have a profound influence on the operational characteristics of the porous bearing. The outcome of the present study will be helpful in deciding the operational regime of the porous bearing under the practically-relevant stochastic environment.","PeriodicalId":17586,"journal":{"name":"Journal of Tribology-transactions of The Asme","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45669314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：