scholarly journals A Study on the Improvement of the Fatigue Life of Bearings by Ultrasonic Nanocrystal Surface Modification Technology

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1114 ◽  
Author(s):  
Shirmendagva Darisuren ◽  
Jeong-Hyeon Park ◽  
Young-Sik Pyun ◽  
Auezhan Amanov
Keyword(s):  
Surface Roughness ◽  
Surface Modification ◽  
Fatigue Life ◽  
Roller Bearing ◽  
Surface Hardness ◽  
Oil Lubrication ◽  
Roller Bearings ◽  
Before And After ◽  
Lubrication Conditions

In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) technology on the fatigue life of needle roller bearings were investigated. The fatigue life of the untreated and UNSM-treated needle roller bearings was evaluated using a roller fatigue tester at various contact stress levels, under oil lubrication conditions. It was found that the fatigue life of the UNSM-treated needle roller bearing was extended by approximately 34.3% in comparison with the untreated one. The results of the surface roughness and surface hardness of the needle roller bearings before and after UNSM technology were compared and discussed in order to understand the role of UNSM technology in improving fatigue life. It was found that the application of UNSM technology to the needle roller bearings can improve their fatigue life by reducing the friction coefficient and increasing the wear resistance, which may be attributed to the reduction in surface roughness from 0.50 µm to 0.15 µm and also the increase in surface hardness from 58 HRC to 62 HRC.

Improvement in Microscratch Resistance of Graphite by Surface Modification for Molding Applications

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Auezhan Amanov ◽  
Bakhtiyor Urmanov ◽  
Ki-Chol Kim ◽  
Young-Sik Pyun
Keyword(s):  
Surface Roughness ◽  
Surface Modification ◽  
Three Dimensional ◽  
Surface Hardness ◽  
Scratch Test ◽  
Scratch Resistance ◽  
Molding Process ◽  
Cover Glass ◽  
Force Microscopy ◽  
Before And After

This paper deals with the improvement in surface properties and microscratch resistance of graphites by means of an ultrasonic nanocrystalline surface modification (UNSM) technique. The surface roughness and surface hardness of the untreated and UNSM-treated graphites were investigated using an atomic force microscopy (AFM) and a microhardness tester, respectively. The scratch resistance was assessed using a microscratch tester at a progressive load. Moreover, a Raman spectroscopy was employed to characterize the microstructure of graphites before and after UNSM treatment. The scratch test results revealed that the resistance to scratch of both UNSM-treated graphites was found to be better in comparison with the untreated graphites. The increase in scratch resistance of both UNSM-treated graphites may be mainly attributed to the reduced surface roughness and increased surface hardness by UNSM treatment. The graphite produced by Poco exhibited a higher resistance to scratch compared to that of the graphite produced by Mersen. The objective of this study is to extend the service life of three-dimensional (3D) cover glass moldings made of graphite by the application of UNSM treatment through the understanding the effects of surface roughness and surface hardness on the scratch defect generation behavior during glass molding process.

scholarly journals Rolling Contact Fatigue Life of Case−Hardened Steel Treated by Shot Peenings with Shot Diameters of 0.05 mm and 0.30 mm

2011 ◽  
Vol 86 ◽  
pp. 645-648 ◽  
Author(s):  
Lei Wang ◽  
Guang Liang Liu ◽  
Masanori Seki ◽  
Masahiro Fujii ◽  
Qian Li
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Shot Peening ◽  
Fine Particle ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Surface Hardness ◽  
Hardened Steel ◽  
Rolling Contact ◽  
Contact Fatigue Life

In order to investigate the influence of different shot peenings on the rolling contact fatigue life of case−hardened steel, the thrust type rolling contact fatigue test was performed with a ball−on−disk contact tester. In this study, the case−hardened steel disks were treated by the fine particle peening with a shot diameter of 0.05 mm and the normal shot peening with a shot diameter of 0.30 mm. The surface hardness and the surface compressive residual stress of the test disks were increased by these peenings. On the other hand, the surface roughness of the test disks was increased by the normal shot peening, and was decreased by the fine particle peening. The rolling contact fatigue test showed that the rolling contact fatigue life of the test disks was improved by the fine particle peening, and was not improved by the normal shot peening. The rolling contact fatigue life of the test disks became longer as their surface roughness became smaller. Therefore, it follows from this that the fine particle peening, which can provide the increase in surface hardness and the decrease in surface roughness, is good for the increase in the rolling contact fatigue life of case−hardened steel.

scholarly journals Rapidly-Dissolving silver-containing bioactive glasses for cariostatic applications

2021 ◽  
Author(s):  
Omar Rodríguez ◽  
Adel M.F. Alhalawani ◽  
Saad Arshad ◽  
Mark R. Towler
Keyword(s):  
Silver Oxide ◽  
Surface Hardness ◽  
Inhibition Zone ◽  
Bacterial Strains ◽  
Buffer Solution ◽  
Solution Ph ◽  
Before And After ◽  
Resultant Solution ◽  
Knoop Microhardness

A novel bioactive glass series containing incremental amounts of silver oxide was synthesized, ground down, and subsequently incorporated into a dentifrice for the purpose of reducing the incidence of dental caries and lesion formation. Three glasses were synthesized using the melt quench route: Si-Control (70SiO2–12CaO–3P2O5–15Na2O, mol %), Si-02 and Si-05, where 0.2 and 0.5 mol % Ag2O were substituted, respectively, for SiO2 in Si-Control. The glasses were then ground, sieved, characterized, and dissolved in Tris buffer solution (pH = 7.30) for 6, 12, and 24 h, with the pH of the resultant solution being recorded and the ions that were released into solution quantified. Samples of each glass were subsequently embedded into a non-fluoridated, commercially available toothpaste which was then used to brush resin-mounted lamb molars which, up to the point of testing, had been stored in a 1.0 M HCl solution. Knoop microhardness measurements of the molars were recorded before and after brushing to determine the presence of remineralization on the surface of the teeth (surface hardness loss of 37%, 35%, and 34% for Si-Control, Si-02 and Si-05, respectively, after 24 h). Four oral cavity bacterial strains were isolated through swabs of the inner cheek, gums, and teeth surfaces of three volunteers, and placed on agar discs. Of each glass, 0.5 g was placed onto the discs, and the resultant inhibition zones were measured after 6, 12, and 24 h. Si-05 performed better than Si-02 on two strains after 24 h, while exhibiting similar behavior for the remaining two strains after 24 h; the largest inhibition zone measured was 2.8 mm, for Si-05 after 12 h. Si-Control exhibited no antibacterial effect at any time point, providing evidence for the role of silver oxide as the antibacterial component of these glasses.

An Analytical Dynamic Model of a Hollow Cylindrical Roller Bearing

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Jing Liu ◽  
Yimin Shao
Keyword(s):  
Fatigue Life ◽  
Dynamic Model ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
Great Influence ◽  
Radial Load ◽  
Shaft Speed ◽  
Roller Bearings ◽  
Cylindrical Roller ◽  
Analytical Dynamic

Hollow cylindrical roller bearings (HCRBs) have obtained much attention from design engineers in bearing industries since they can perform better than solid cylindrical roller bearings (SCRBs) in centrifugal forces, contact stiffness, cooling ability, fatigue life, etc. In this study, an analytical dynamic model of a lubricated HCRB is presented to analyze the influences of the radial load, the shaft speed, and the hollowness percentage of the roller on the bearing vibrations, which cannot be formulated by the methods in the reported literature. Both the support stiffness of the shaft and the roller mass are formulated in the presented dynamic model. The hollow hole in the roller is modeled as a uniform one. Numerical results show that the hollowness percentage of the roller has a great influence on the vibrations of the roller and the inner race of the HCRB. Moreover, the vibrations of the components of the HCRB are not only determined by the hollowness percentage of the roller, but also depended on the external radial load and shaft speed. Therefore, during the design process for the hollowness percentage of the roller, the influences of the radial load and the shaft speed on the vibrations of the bearing components should be considered, except for the fatigue life. The results show that this work can give a new dynamic method for analyzing the vibrations of the HCRBs. Moreover, it can give some guidance for the design method for the HCRBs.

Study on Characteristics of ADI Coated DLC/ TiN /TiAlN Coatings by Cathodic Arc Evaporation

2006 ◽  
Vol 118 ◽  
pp. 257-264 ◽  
Author(s):  
Cheng Hsun Hsu ◽  
Jung Kai Lu ◽  
Ming Li Chen
Keyword(s):  
Surface Roughness ◽  
Corrosion Resistance ◽  
Surface Modification ◽  
Substrate Surface ◽  
Surface Hardness ◽  
High Carbon ◽  
Cathodic Arc Evaporation ◽  
Nodular Graphite ◽  
Arc Evaporation ◽  
Cathodic Arc

In this study, austempered ductile iron (ADI) substrate containing acicular ferrite and high-carbon austenite in the microstructure is made by austempering treatment at 360. Cathodic arc evaporation (CAE) coating technique was used to coat DLC, TiN and TiAlN films on ADI for surface modification. The results showed that the three coatings could be successfully coated onto ADI through CAE process without altering the unique microstructure of ADI. The structures of the coatings were identified by XRD, Raman and TEM, respectively. After HRC indentation testing, it was found that nodular graphite was the initial site of cracking for the coatings and then peeled. Surface roughness of all coated specimens was increased because the droplets generated on the substrate surface during the CAE process. Coated ADI had better wearability performance than uncoated ADI due to higher surface hardness. Coated specimens exhibited higher corrosion resistance than uncoated ones when they were immersed in separate solutions of both 3.5 wt. % NaCl and 10 vol. % HCl. In particular, TiAlN had the best corrosion resistance among the coated specimens.

Effect of Laser Shock Processing (LSP) on the Fatigue Resistance of an Aluminum Alloy

1999 ◽  
Vol 122 (1) ◽  
pp. 104-107 ◽  
Author(s):  
Tang Yaxin ◽  
Zhang Yongkang ◽  
Zhang Hong ◽  
Yu Chengye
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Polyvinylidene Fluoride ◽  
Surface Hardness ◽  
Resistance Mechanisms ◽  
Laser Shock ◽  
Laser Shock Processing ◽  
Fatigue And Fracture ◽  
Before And After ◽  
Shock Processing

The laser shock induced stress wave is described and measured with a polyvinylidene fluoride (PVDF) transducer. A principle for selecting laser parameters is proposed. A small sized laser with a high power is used for Laser Shock Processing (LSP). The fatigue life of the aluminum alloy 2024T62 is greatly improved after LSP. With 95% confidence, the mean fatigue life of LSP specimens is 4.5–9.8 times that of unshocked ones. The fatigue and fracture resistance mechanisms of LSP such as the variation of the surface hardness, the microstructure and the fracture section of specimens before and after LSP are analyzed. [S0094-4289(00)01601-7]

scholarly journals Rapidly-Dissolving silver-containing bioactive glasses for cariostatic applications

2021 ◽  
Author(s):  
Omar Rodríguez ◽  
Adel M.F. Alhalawani ◽  
Saad Arshad ◽  
Mark R. Towler
Keyword(s):  
Silver Oxide ◽  
Surface Hardness ◽  
Inhibition Zone ◽  
Bacterial Strains ◽  
Buffer Solution ◽  
Solution Ph ◽  
Before And After ◽  
Resultant Solution ◽  
Knoop Microhardness

A novel bioactive glass series containing incremental amounts of silver oxide was synthesized, ground down, and subsequently incorporated into a dentifrice for the purpose of reducing the incidence of dental caries and lesion formation. Three glasses were synthesized using the melt quench route: Si-Control (70SiO2–12CaO–3P2O5–15Na2O, mol %), Si-02 and Si-05, where 0.2 and 0.5 mol % Ag2O were substituted, respectively, for SiO2 in Si-Control. The glasses were then ground, sieved, characterized, and dissolved in Tris buffer solution (pH = 7.30) for 6, 12, and 24 h, with the pH of the resultant solution being recorded and the ions that were released into solution quantified. Samples of each glass were subsequently embedded into a non-fluoridated, commercially available toothpaste which was then used to brush resin-mounted lamb molars which, up to the point of testing, had been stored in a 1.0 M HCl solution. Knoop microhardness measurements of the molars were recorded before and after brushing to determine the presence of remineralization on the surface of the teeth (surface hardness loss of 37%, 35%, and 34% for Si-Control, Si-02 and Si-05, respectively, after 24 h). Four oral cavity bacterial strains were isolated through swabs of the inner cheek, gums, and teeth surfaces of three volunteers, and placed on agar discs. Of each glass, 0.5 g was placed onto the discs, and the resultant inhibition zones were measured after 6, 12, and 24 h. Si-05 performed better than Si-02 on two strains after 24 h, while exhibiting similar behavior for the remaining two strains after 24 h; the largest inhibition zone measured was 2.8 mm, for Si-05 after 12 h. Si-Control exhibited no antibacterial effect at any time point, providing evidence for the role of silver oxide as the antibacterial component of these glasses.

Semi-Analytical Modeling of Crack Initiation Dominant Contact Fatigue Life for Roller Bearings

1997 ◽  
Vol 119 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Wangquan (Winston) Cheng ◽  
Herbert S. Cheng
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Maximum Shear Stress ◽  
Equivalent Stress ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
New Model ◽  
Roller Bearings ◽  
Contact Width

The fatigue test of a needle roller bearing suggests that the dominant failure mechanism is subsurface crack initiation and propagation. Therefore, a new semi-analytical contact fatigue model is derived from a micromechanics based crack initiation model. The analysis indicates that in the life calculation the selection of the critical stress, such as the maximum orthogonal shear stress, maximum shear stress, octahedral shear stress, or von Mises equivalent stress, becomes arbitrary under the nonfrictional Hertzian line contact condition. The fatigue life of roller bearings under the pure rolling condition can be predicted by simply knowing the Hertzian contact pressure and the contact width, which avoids complicated calculation of the subsurface stresses. The film thickness, roughness, and the material hardness effects on contact fatigue are also included in the new model. The comparisons with different models and the experimental data indicate that the new model makes similar life predictions as the Ioannides-Harris model, but the new model is much simpler to use. The Lundberg-Palmgren model does not fit with the experiment data.

Axial Load Effect on Contact Fatigue Life of Cylindrical Roller Bearings

2004 ◽  
Vol 126 (2) ◽  
pp. 242-247 ◽  
Author(s):  
Wangquan (Winston) Cheng ◽  
Shan Shih ◽  
John Grace ◽  
Wenke Tu
Keyword(s):  
Fatigue Life ◽  
Axial Load ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
Limit Load ◽  
Load Effect ◽  
Roller Bearings ◽  
Contact Fatigue Life ◽  
Fatigue Life Analysis ◽  
Cylindrical Roller

Besides primarily carrying radial load, cylindrical roller bearings with flanges or lips on both inner and outer raceways need also carry axial load in some applications. Because of the axial load, the equivalent dynamic load of the bearing will be increased and the bearing contact fatigue life will be decreased accordingly. The axial load effect on the roller bearing fatigue life had been studied by researchers in the past. Because of different assumptions used in their models, quite different predictions were made in their analysis. This work combines the methods used in the Fernlund-Synek and Brandlein models and studies general contact conditions such as partial contact along the roller length, partial loading zone of the bearing race, manufacturing tolerance and running-in effects on roller length, etc. New formulas for equivalent dynamic loads of the rotating and stationary races are derived. A fatigue limit load is also included in the life calculation to reflect the latest development in contact fatigue life analysis.

scholarly journals Lubrication and Fatigue Life Evaluation of High-Speed Cylindrical Roller Bearing under Misalignment

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Hongyu Duan ◽  
Jiawei Song ◽  
Zhijian Wang
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Roller Bearing ◽  
Coupled Model ◽  
Roller Bearings ◽  
Life Model ◽  
Fatigue Life Evaluation ◽  
Roller Profile ◽  
Cylindrical Roller Bearing ◽  
Cylindrical Roller

This paper developed a coupled model, incorporating the quasistatic model, fatigue life model, and mixed lubrication model, to investigate the effect of misalignment angle on high-speed cylindrical roller bearings. The model is verified by comparing with the published literature results. Then, a parametric analysis is carried out. The results show that as the misalignment increases, the load distribution is basically unchanged, but the fatigue life of the roller bearing decreases due to the variation of contact pressure, and the skewing moment of single roller contact pair increases. Furthermore, the optimal design of roller profile needs to consider the effect of lubrication in order to improve the fatigue life of roller bearings. In general, the optimal crown drop is too small according to the design from the slicing technique.

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