Pub Date : 2024-02-07DOI: 10.3390/lubricants12020047
Pushkar Deshpande, K. Wasmer, Thomas Imwinkelried, Roman Heuberger, Michael Dreyer, B. Weisse, R. Crockett, V. Pandiyan
Human joint prostheses experience wear failure due to the complex interactions between Ultra-High-Molecular-Weight Polyethylene (UHMWPE) and Cobalt-Chromium-Molybdenum (CoCrMo). This study uses the wear classification to investigate the gradual and progressive abrasive wear mechanisms in UHMWPE. Pin-on-disc tests were conducted under simulated in vivo conditions, monitoring wear using Acoustic Emission (AE). Two Machine Learning (ML) frameworks were employed for wear classification: manual feature extraction with ML classifiers and a contrastive learning-based Convolutional Neural Network (CNN) with ML classifiers. The CNN-based feature extraction approach achieved superior classification performance (94% to 96%) compared to manual feature extraction (81% to 89%). The ML techniques enable accurate wear classification, aiding in understanding surface states and early failure detection. Real-time monitoring using AE sensors shows promise for interventions and improving prosthetic joint design.
由于超高分子量聚乙烯（UHMWPE）和钴铬钼（CoCrMo）之间复杂的相互作用，人体关节假体会出现磨损故障。本研究采用磨损分类法来研究超高分子量聚乙烯的渐进和渐进磨损机制。在模拟活体条件下进行了针盘测试，使用声发射（AE）监测磨损情况。磨损分类采用了两种机器学习（ML）框架：带有 ML 分类器的手动特征提取和带有 ML 分类器的基于对比学习的卷积神经网络（CNN）。与人工特征提取（81% 至 89%）相比，基于 CNN 的特征提取方法实现了更高的分类性能（94% 至 96%）。ML 技术可实现精确的磨损分类，有助于了解表面状态和早期故障检测。使用 AE 传感器进行实时监测为干预和改进假体关节设计带来了希望。
{"title":"Classification of Progressive Wear on a Multi-Directional Pin-on-Disc Tribometer Simulating Conditions in Human Joints-UHMWPE against CoCrMo Using Acoustic Emission and Machine Learning","authors":"Pushkar Deshpande, K. Wasmer, Thomas Imwinkelried, Roman Heuberger, Michael Dreyer, B. Weisse, R. Crockett, V. Pandiyan","doi":"10.3390/lubricants12020047","DOIUrl":"https://doi.org/10.3390/lubricants12020047","url":null,"abstract":"Human joint prostheses experience wear failure due to the complex interactions between Ultra-High-Molecular-Weight Polyethylene (UHMWPE) and Cobalt-Chromium-Molybdenum (CoCrMo). This study uses the wear classification to investigate the gradual and progressive abrasive wear mechanisms in UHMWPE. Pin-on-disc tests were conducted under simulated in vivo conditions, monitoring wear using Acoustic Emission (AE). Two Machine Learning (ML) frameworks were employed for wear classification: manual feature extraction with ML classifiers and a contrastive learning-based Convolutional Neural Network (CNN) with ML classifiers. The CNN-based feature extraction approach achieved superior classification performance (94% to 96%) compared to manual feature extraction (81% to 89%). The ML techniques enable accurate wear classification, aiding in understanding surface states and early failure detection. Real-time monitoring using AE sensors shows promise for interventions and improving prosthetic joint design.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"81 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139855626","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 : 2024-02-06DOI: 10.3390/lubricants12020046
Cem Maden, Hande Ustunel, D. Toffoli
Atomic force microscopes are used, besides their principal function as surface imaging tools, in the surface manipulation and measurement of interfacial properties. In particular, they can be modified to measure lateral friction forces that occur during the sliding of the tip against the underlying substrate. However, the shape, size, and deformation of the tips profoundly affect the measurements in a manner that is difficult to predict. In this work, we investigate the contribution of these effect to the magnitude of the lateral forces during sliding. The surface substrate is chosen to be a few-layer AB-stacked graphene surface, whereas the tip is initially constructed from face-centered cubic gold. In order to separate the effect of deformation from the shape, the rigid tips of three different shapes were considered first, namely, a cone, a pyramid and a hemisphere. The shape was seen to dictate all aspects of the interface during sliding, from temperature dependence to stick–slip behavior. Deformation was investigated next by comparing a rigid hemispherical tip to one of an identical shape and size but with all but the top three layers of atoms being free to move. The deformation, as also verified by an indentation analysis, occurs by means of the lower layers collapsing on the upper ones, thereby increasing the contact area. This collapse mitigates the friction force and decreases it with respect to the rigid tip for the same vertical distance. Finally, the size effect is studied by means of calculating the friction forces for a much larger hemispherical tip whose atoms are free to move. In this case, the deformation is found to be much smaller, but the stick–slip behavior is much more clearly seen.
原子力显微镜除了作为表面成像工具的主要功能外，还可用于表面操作和界面特性测量。特别是，原子力显微镜可以进行改装，以测量针尖与底层基底滑动时产生的横向摩擦力。然而，针尖的形状、大小和变形会以难以预测的方式对测量产生深远影响。在这项工作中，我们研究了这些影响对滑动过程中横向力大小的贡献。表面基底选择为几层 AB 叠层石墨烯表面，而尖端最初由面心立方金制成。为了将变形的影响与形状区分开来，首先考虑了三种不同形状的刚性尖端，即锥形、金字塔形和半球形。在滑动过程中，形状决定了界面的各个方面，包括温度依赖性和粘滑行为。接下来，通过比较刚性半球形尖端与形状和大小相同但除顶部三层原子外均可自由移动的半球形尖端，对变形进行了研究。压痕分析也证实，变形是通过下层塌陷到上层，从而增加接触面积的方式发生的。这种塌陷减轻了摩擦力，在垂直距离相同的情况下，摩擦力相对于刚性尖端会减小。最后，通过计算原子可自由移动的更大半球形尖端的摩擦力，研究了尺寸效应。在这种情况下，我们发现变形要小得多，但粘滑行为要明显得多。
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Pub Date : 2024-02-06DOI: 10.3390/lubricants12020046
Cem Maden, Hande Ustunel, D. Toffoli
Atomic force microscopes are used, besides their principal function as surface imaging tools, in the surface manipulation and measurement of interfacial properties. In particular, they can be modified to measure lateral friction forces that occur during the sliding of the tip against the underlying substrate. However, the shape, size, and deformation of the tips profoundly affect the measurements in a manner that is difficult to predict. In this work, we investigate the contribution of these effect to the magnitude of the lateral forces during sliding. The surface substrate is chosen to be a few-layer AB-stacked graphene surface, whereas the tip is initially constructed from face-centered cubic gold. In order to separate the effect of deformation from the shape, the rigid tips of three different shapes were considered first, namely, a cone, a pyramid and a hemisphere. The shape was seen to dictate all aspects of the interface during sliding, from temperature dependence to stick–slip behavior. Deformation was investigated next by comparing a rigid hemispherical tip to one of an identical shape and size but with all but the top three layers of atoms being free to move. The deformation, as also verified by an indentation analysis, occurs by means of the lower layers collapsing on the upper ones, thereby increasing the contact area. This collapse mitigates the friction force and decreases it with respect to the rigid tip for the same vertical distance. Finally, the size effect is studied by means of calculating the friction forces for a much larger hemispherical tip whose atoms are free to move. In this case, the deformation is found to be much smaller, but the stick–slip behavior is much more clearly seen.
原子力显微镜除了作为表面成像工具的主要功能外，还可用于表面操作和界面特性测量。特别是，原子力显微镜可以进行改装，以测量针尖与底层基底滑动时产生的横向摩擦力。然而，针尖的形状、大小和变形会以难以预测的方式对测量产生深远影响。在这项工作中，我们研究了这些影响对滑动过程中横向力大小的贡献。表面基底选择为几层 AB 叠层石墨烯表面，而尖端最初由面心立方金制成。为了将变形的影响与形状区分开来，首先考虑了三种不同形状的刚性尖端，即锥形、金字塔形和半球形。在滑动过程中，形状决定了界面的各个方面，包括温度依赖性和粘滑行为。接下来，通过比较刚性半球形尖端与形状和大小相同但除顶部三层原子外均可自由移动的半球形尖端，对变形进行了研究。压痕分析也证实，变形是通过下层塌陷到上层，从而增加接触面积的方式发生的。这种塌陷减轻了摩擦力，在垂直距离相同的情况下，摩擦力相对于刚性尖端会减小。最后，通过计算原子可自由移动的更大半球形尖端的摩擦力，研究了尺寸效应。在这种情况下，我们发现变形要小得多，但粘滑行为要明显得多。
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Pub Date : 2024-02-04DOI: 10.3390/lubricants12020044
Yang Yang, Guan Wang, Xingchen Zhou, Xingkang Su, Long Gu
Vacuum-sliding electrical contacts find extensive application in aerospace components, yet they face limitations related to inadequate lubrication performance. In this study, we analyzed the design of an emerging conductive lubricant material, NbSe2. A series of NbSe2-Ti films with varying doped Ti contents were prepared through magnetron sputtering technology. We investigated the correlation between the sputtering current and composition, microstructure, mechanical properties, and current-carrying tribological properties of the films. The results indicate that under vacuum and current-carrying conditions, the NbSe2-Ti films demonstrate significant advantages over existing electrical-contact lubrication materials. Compared with electroplated gold films, the NbSe2-Ti films reduced the coefficient of friction from 0.25 to 0.015, thereby improving the wear life by more than six times. This result demonstrates that magnetron-sputtered NbSe2 film can be used as a lubricant for space current-carrying sliding contacts.
{"title":"A Promising Conductive Lubricant for Space Sliding Electrical Contact: NbSe2-Ti Film","authors":"Yang Yang, Guan Wang, Xingchen Zhou, Xingkang Su, Long Gu","doi":"10.3390/lubricants12020044","DOIUrl":"https://doi.org/10.3390/lubricants12020044","url":null,"abstract":"Vacuum-sliding electrical contacts find extensive application in aerospace components, yet they face limitations related to inadequate lubrication performance. In this study, we analyzed the design of an emerging conductive lubricant material, NbSe2. A series of NbSe2-Ti films with varying doped Ti contents were prepared through magnetron sputtering technology. We investigated the correlation between the sputtering current and composition, microstructure, mechanical properties, and current-carrying tribological properties of the films. The results indicate that under vacuum and current-carrying conditions, the NbSe2-Ti films demonstrate significant advantages over existing electrical-contact lubrication materials. Compared with electroplated gold films, the NbSe2-Ti films reduced the coefficient of friction from 0.25 to 0.015, thereby improving the wear life by more than six times. This result demonstrates that magnetron-sputtered NbSe2 film can be used as a lubricant for space current-carrying sliding contacts.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"13 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139867182","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 : 2024-02-04DOI: 10.3390/lubricants12020045
J. Wranik, Walter Holweger, Ling Wang
White Etching Cracks (WEC) have become a subject of extensive research in material science, chemistry and lubrication, and even operational mathematics by AI learning. Initially reported in the 1960s and considered an exotic anomaly, the failures gained importance with the global rise of wind energy power and the automotive industry. Unexpectedly high failure rates in various bearing applications have led to the need for a deeper understanding and prevention of WEC. It has come a long way from materials inspection, to parametrically studying WECs on test rigs, to the understanding that WEC is a stand-alone phenomenon and sparingly related to common failures in bearing technology. It has been commonly accepted that WEC drivers have multiple dimensions, e.g., material, contact mechanics, chemistry, and electricity. The impact of these factors on WEC failures is frequently studied using test rigs at the component level, such as the FE8 test rig. The FE8 has been utilized in numerous investigations due to its ability to replicate WEC failures without requiring artificial electricity or hydrogen charging by using specific lubricant chemistry and operating conditions. However, through intensive testing, it was observed in this study that a standard material in an FE8 rig component demonstrated a profound influence on WEC formation. This paper presents the details of the testing and analysis, aiming to investigate the mechanisms of interactions between the hose material and the low reference lubricant. The results demonstrate that the chemistry of the component material plays an important role in WEC formation. This finding may have significant impact in WEC studies, especially when the FE8 rig is used.
{"title":"The Influence of Peripheral Components in Test Rig Creation of White Etching Cracks","authors":"J. Wranik, Walter Holweger, Ling Wang","doi":"10.3390/lubricants12020045","DOIUrl":"https://doi.org/10.3390/lubricants12020045","url":null,"abstract":"White Etching Cracks (WEC) have become a subject of extensive research in material science, chemistry and lubrication, and even operational mathematics by AI learning. Initially reported in the 1960s and considered an exotic anomaly, the failures gained importance with the global rise of wind energy power and the automotive industry. Unexpectedly high failure rates in various bearing applications have led to the need for a deeper understanding and prevention of WEC. It has come a long way from materials inspection, to parametrically studying WECs on test rigs, to the understanding that WEC is a stand-alone phenomenon and sparingly related to common failures in bearing technology. It has been commonly accepted that WEC drivers have multiple dimensions, e.g., material, contact mechanics, chemistry, and electricity. The impact of these factors on WEC failures is frequently studied using test rigs at the component level, such as the FE8 test rig. The FE8 has been utilized in numerous investigations due to its ability to replicate WEC failures without requiring artificial electricity or hydrogen charging by using specific lubricant chemistry and operating conditions. However, through intensive testing, it was observed in this study that a standard material in an FE8 rig component demonstrated a profound influence on WEC formation. This paper presents the details of the testing and analysis, aiming to investigate the mechanisms of interactions between the hose material and the low reference lubricant. The results demonstrate that the chemistry of the component material plays an important role in WEC formation. This finding may have significant impact in WEC studies, especially when the FE8 rig is used.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"2010 33","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139807178","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 : 2024-02-04DOI: 10.3390/lubricants12020044
Yang Yang, Guan Wang, Xingchen Zhou, Xingkang Su, Long Gu
Vacuum-sliding electrical contacts find extensive application in aerospace components, yet they face limitations related to inadequate lubrication performance. In this study, we analyzed the design of an emerging conductive lubricant material, NbSe2. A series of NbSe2-Ti films with varying doped Ti contents were prepared through magnetron sputtering technology. We investigated the correlation between the sputtering current and composition, microstructure, mechanical properties, and current-carrying tribological properties of the films. The results indicate that under vacuum and current-carrying conditions, the NbSe2-Ti films demonstrate significant advantages over existing electrical-contact lubrication materials. Compared with electroplated gold films, the NbSe2-Ti films reduced the coefficient of friction from 0.25 to 0.015, thereby improving the wear life by more than six times. This result demonstrates that magnetron-sputtered NbSe2 film can be used as a lubricant for space current-carrying sliding contacts.
{"title":"A Promising Conductive Lubricant for Space Sliding Electrical Contact: NbSe2-Ti Film","authors":"Yang Yang, Guan Wang, Xingchen Zhou, Xingkang Su, Long Gu","doi":"10.3390/lubricants12020044","DOIUrl":"https://doi.org/10.3390/lubricants12020044","url":null,"abstract":"Vacuum-sliding electrical contacts find extensive application in aerospace components, yet they face limitations related to inadequate lubrication performance. In this study, we analyzed the design of an emerging conductive lubricant material, NbSe2. A series of NbSe2-Ti films with varying doped Ti contents were prepared through magnetron sputtering technology. We investigated the correlation between the sputtering current and composition, microstructure, mechanical properties, and current-carrying tribological properties of the films. The results indicate that under vacuum and current-carrying conditions, the NbSe2-Ti films demonstrate significant advantages over existing electrical-contact lubrication materials. Compared with electroplated gold films, the NbSe2-Ti films reduced the coefficient of friction from 0.25 to 0.015, thereby improving the wear life by more than six times. This result demonstrates that magnetron-sputtered NbSe2 film can be used as a lubricant for space current-carrying sliding contacts.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"2006 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139807287","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 : 2024-02-04DOI: 10.3390/lubricants12020045
J. Wranik, Walter Holweger, Ling Wang
White Etching Cracks (WEC) have become a subject of extensive research in material science, chemistry and lubrication, and even operational mathematics by AI learning. Initially reported in the 1960s and considered an exotic anomaly, the failures gained importance with the global rise of wind energy power and the automotive industry. Unexpectedly high failure rates in various bearing applications have led to the need for a deeper understanding and prevention of WEC. It has come a long way from materials inspection, to parametrically studying WECs on test rigs, to the understanding that WEC is a stand-alone phenomenon and sparingly related to common failures in bearing technology. It has been commonly accepted that WEC drivers have multiple dimensions, e.g., material, contact mechanics, chemistry, and electricity. The impact of these factors on WEC failures is frequently studied using test rigs at the component level, such as the FE8 test rig. The FE8 has been utilized in numerous investigations due to its ability to replicate WEC failures without requiring artificial electricity or hydrogen charging by using specific lubricant chemistry and operating conditions. However, through intensive testing, it was observed in this study that a standard material in an FE8 rig component demonstrated a profound influence on WEC formation. This paper presents the details of the testing and analysis, aiming to investigate the mechanisms of interactions between the hose material and the low reference lubricant. The results demonstrate that the chemistry of the component material plays an important role in WEC formation. This finding may have significant impact in WEC studies, especially when the FE8 rig is used.
{"title":"The Influence of Peripheral Components in Test Rig Creation of White Etching Cracks","authors":"J. Wranik, Walter Holweger, Ling Wang","doi":"10.3390/lubricants12020045","DOIUrl":"https://doi.org/10.3390/lubricants12020045","url":null,"abstract":"White Etching Cracks (WEC) have become a subject of extensive research in material science, chemistry and lubrication, and even operational mathematics by AI learning. Initially reported in the 1960s and considered an exotic anomaly, the failures gained importance with the global rise of wind energy power and the automotive industry. Unexpectedly high failure rates in various bearing applications have led to the need for a deeper understanding and prevention of WEC. It has come a long way from materials inspection, to parametrically studying WECs on test rigs, to the understanding that WEC is a stand-alone phenomenon and sparingly related to common failures in bearing technology. It has been commonly accepted that WEC drivers have multiple dimensions, e.g., material, contact mechanics, chemistry, and electricity. The impact of these factors on WEC failures is frequently studied using test rigs at the component level, such as the FE8 test rig. The FE8 has been utilized in numerous investigations due to its ability to replicate WEC failures without requiring artificial electricity or hydrogen charging by using specific lubricant chemistry and operating conditions. However, through intensive testing, it was observed in this study that a standard material in an FE8 rig component demonstrated a profound influence on WEC formation. This paper presents the details of the testing and analysis, aiming to investigate the mechanisms of interactions between the hose material and the low reference lubricant. The results demonstrate that the chemistry of the component material plays an important role in WEC formation. This finding may have significant impact in WEC studies, especially when the FE8 rig is used.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"8 5-6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139867323","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 : 2024-02-03DOI: 10.3390/lubricants12020043
Yongjian Yu, Ruixiang Ma, Yujun Xue, Yonggang Liu
To develop an angular contact ball bearing with low power consumption, a heat generation calculation model for angular contact ball bearings has been established based on bearing quasi dynamics, elastohydrodynamic lubrication theory, heat transfer theory, and Kirchhoff’s law of energy conservation, considering the effects of roundness error, bearing preload, centrifugal effect, and thermal expansion. The correctness of the model is verified through experiments. The influence of different operating conditions and roundness errors on the thermal characteristics of angular contact ball bearings is analyzed. The results of the calculation indicate that when the roundness error order is equal to the number of balls n/2 ± 2 (where n = 1, 2, 3, …), the overall heat generation of the bearing is lower than that without considering the roundness error. When the roundness error order is equal to (2n − 1)/4 ± 2 (where n = 1, 2, 3, …), the overall heat generation of the bearing is higher than that without considering the roundness error. At the same rotating speed, the overall heat generation fluctuates as the roundness error order changes, and the trend becomes more pronounced as the rotating speed increases. The maximum overall heat generation is achieved when the roundness error order equals (2n − 1)/4 times (where n = 1, 2, 3, …) the number of balls. When the roundness error order is equal to n/2 times the number of balls (where n = 1, 2, 3, …), the bearing’s overall heat generation is minimal. The variation in the total heat generated by the bearing is directly proportional to the amplitude of the roundness error. With the increase in roundness error harmonic order, the bearing integral heat generation shows a periodic change, and the change period has a mapping relationship with the number of balls.
为了开发低功耗角接触球轴承，基于轴承准动力学、弹性流体动力润滑理论、传热理论和基尔霍夫能量守恒定律，并考虑了圆度误差、轴承预紧力、离心效应和热膨胀的影响，建立了角接触球轴承的发热计算模型。通过实验验证了模型的正确性。分析了不同工作条件和圆度误差对角接触球轴承热特性的影响。计算结果表明，当圆度误差阶数等于球数 n/2 ± 2 时（其中 n = 1、2、3、......），轴承的总体发热量低于不考虑圆度误差时的发热量。当圆度误差阶数等于 (2n - 1)/4 ± 2 时（其中 n = 1、2、3、...），轴承的总发热量高于不考虑圆度误差时的发热量。在相同转速下，随着圆度误差阶数的变化，轴承的总发热量也随之波动，随着转速的增加，这种趋势更加明显。当圆度误差阶数等于球数的 (2n - 1)/4 倍（其中 n = 1、2、3、...）时，总发热量最大。当圆度误差阶数等于球数的 n/2 倍（其中 n = 1、2、3、......）时，轴承的总发热量最小。轴承总发热量的变化与圆度误差的大小成正比。随着圆度误差谐波阶数的增加，轴承整体发热量呈周期性变化，且变化周期与滚珠数量呈映射关系。
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Pub Date : 2024-02-03DOI: 10.3390/lubricants12020043
Yongjian Yu, Ruixiang Ma, Yujun Xue, Yonggang Liu
To develop an angular contact ball bearing with low power consumption, a heat generation calculation model for angular contact ball bearings has been established based on bearing quasi dynamics, elastohydrodynamic lubrication theory, heat transfer theory, and Kirchhoff’s law of energy conservation, considering the effects of roundness error, bearing preload, centrifugal effect, and thermal expansion. The correctness of the model is verified through experiments. The influence of different operating conditions and roundness errors on the thermal characteristics of angular contact ball bearings is analyzed. The results of the calculation indicate that when the roundness error order is equal to the number of balls n/2 ± 2 (where n = 1, 2, 3, …), the overall heat generation of the bearing is lower than that without considering the roundness error. When the roundness error order is equal to (2n − 1)/4 ± 2 (where n = 1, 2, 3, …), the overall heat generation of the bearing is higher than that without considering the roundness error. At the same rotating speed, the overall heat generation fluctuates as the roundness error order changes, and the trend becomes more pronounced as the rotating speed increases. The maximum overall heat generation is achieved when the roundness error order equals (2n − 1)/4 times (where n = 1, 2, 3, …) the number of balls. When the roundness error order is equal to n/2 times the number of balls (where n = 1, 2, 3, …), the bearing’s overall heat generation is minimal. The variation in the total heat generated by the bearing is directly proportional to the amplitude of the roundness error. With the increase in roundness error harmonic order, the bearing integral heat generation shows a periodic change, and the change period has a mapping relationship with the number of balls.
为了开发低功耗角接触球轴承，基于轴承准动力学、弹性流体动力润滑理论、传热理论和基尔霍夫能量守恒定律，并考虑了圆度误差、轴承预紧力、离心效应和热膨胀的影响，建立了角接触球轴承的发热计算模型。通过实验验证了模型的正确性。分析了不同工作条件和圆度误差对角接触球轴承热特性的影响。计算结果表明，当圆度误差阶数等于球数 n/2 ± 2 时（其中 n = 1、2、3、......），轴承的总体发热量低于不考虑圆度误差时的发热量。当圆度误差阶数等于 (2n - 1)/4 ± 2 时（其中 n = 1、2、3、...），轴承的总发热量高于不考虑圆度误差时的发热量。在相同转速下，随着圆度误差阶数的变化，轴承的总发热量也随之波动，随着转速的增加，这种趋势更加明显。当圆度误差阶数等于球数的 (2n - 1)/4 倍（其中 n = 1、2、3、...）时，总发热量最大。当圆度误差阶数等于球数的 n/2 倍（其中 n = 1、2、3、......）时，轴承的总发热量最小。轴承总发热量的变化与圆度误差的大小成正比。随着圆度误差谐波阶数的增加，轴承整体发热量呈周期性变化，且变化周期与滚珠数量呈映射关系。
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Pub Date : 2024-02-02DOI: 10.3390/lubricants12020042
Yiming Han, Jing Wang, Hengrui Du, Weimin Li, Jingxin Zhao, Zongyi Bai, Meng Hu, Haichao Liu
For wind turbine applications, there is a cyclic load-varying process between rolling elements and raceways in pitch bearings. This kind of motion can also lead to radial fretting. However, this is seldom addressed under grease-lubricated conditions in the literature. In this study, grease-lubricated point contact problems have been investigated experimentally under cyclic load-varying conditions. The findings revealed that as the load-varying range diminishes, the variation in grease film distribution becomes more subtle and the rate of discharge of thickener fiber clusters in the stick zone decelerates. This is due to the fact that the rate of change in the Hertz contact radius is reduced and the migration of grease is weakened during the unloading process. Due to the large apparent viscosity of grease with a high soap content, entrapped grease is not easily discharged during loading, and the thickness of the film in the stick zone progressively increases as the soap content of the grease is augmented. This also causes the variable load zone to wear out more easily. As the grease is subjected to repeated loading and unloading, there is a gradual reduction in film thickness, and larger thickener fiber clusters tear, resulting in a flattened form and shear thinning. Grease containing sulphur–phosphorus additives demonstrates a superior effect on reducing fretting wear within the large variable load range but generally proves effective for smaller load-varying ranges. This study may offer insights into the degradation of grease under variable load motion and methods to prevent radial fretting wear.
{"title":"Film Thickness Decay and Wear Behavior of Grease-Lubricated Point Contact under Cyclic Variable Loads","authors":"Yiming Han, Jing Wang, Hengrui Du, Weimin Li, Jingxin Zhao, Zongyi Bai, Meng Hu, Haichao Liu","doi":"10.3390/lubricants12020042","DOIUrl":"https://doi.org/10.3390/lubricants12020042","url":null,"abstract":"For wind turbine applications, there is a cyclic load-varying process between rolling elements and raceways in pitch bearings. This kind of motion can also lead to radial fretting. However, this is seldom addressed under grease-lubricated conditions in the literature. In this study, grease-lubricated point contact problems have been investigated experimentally under cyclic load-varying conditions. The findings revealed that as the load-varying range diminishes, the variation in grease film distribution becomes more subtle and the rate of discharge of thickener fiber clusters in the stick zone decelerates. This is due to the fact that the rate of change in the Hertz contact radius is reduced and the migration of grease is weakened during the unloading process. Due to the large apparent viscosity of grease with a high soap content, entrapped grease is not easily discharged during loading, and the thickness of the film in the stick zone progressively increases as the soap content of the grease is augmented. This also causes the variable load zone to wear out more easily. As the grease is subjected to repeated loading and unloading, there is a gradual reduction in film thickness, and larger thickener fiber clusters tear, resulting in a flattened form and shear thinning. Grease containing sulphur–phosphorus additives demonstrates a superior effect on reducing fretting wear within the large variable load range but generally proves effective for smaller load-varying ranges. This study may offer insights into the degradation of grease under variable load motion and methods to prevent radial fretting wear.","PeriodicalId":502914,"journal":{"name":"Lubricants","volume":"44 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139810398","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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