Industrial Lubrication and Tribology

Routh, Bikash; Maiti, Rathindranath; Ray, Asok Kumar

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-07-2016-0150

PurposeIn a harmonic drive during assembly of its components like strain wave generating (SWG) cam, flexspline (FS) and circular spline, a gap is formed between the cam’s outer surface and the FS cup inner surface due to mismatching. This gap, which is known as “Coning”, plays a vital role in the flow of lubricant at that interface. This paper aims to analyse the coning phenomenon and the lubrication mechanism.Design/methodology/approachIn the present investigation, the geometry of the coning gap and its variation with the SWG cam rotation are established. Essentially, the deflection of FS cup and deformation of SWG cam (bearing outer race) are derived to find the gap due to coning. Next, the hydrodynamic lubrication equation is solved to get pressure profiles for this gap under suitable boundary conditions assuming non-Newtonian lubrication.FindingsMethods of estimating the coning gap and lubrication pressure profiles are established. Effects of non-Newtonian terms (coupling number and non-dimentionalized characteristic length) and SWG length (finite, long and short) on pressure profiles are also shown. All analyses are done in non-dimensionalized form.Originality/valueEstablishing the geometry of coning and non-Newtonian hydrodynamic lubrication aspects in the coning in the FS cup and SWG cam interface are the originality of the present investigation.

Mojumder, Soumyajit; Sikdar, Soumya; Ghosh, Subrata Kumar

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-04-2016-0079

PurposeArtificial biomaterials are implanted to the human body to support the structure depending upon the extent of deformity or damage. This paper aims to formulate an experimental approach to assess the suitability of materials that can be used in the manufacture of human implants.Design/methodology/approachFive different pin materials such as SS304, Alumina, HDPE, UHMWPE and Brass have been chosen to be suitable for implants. The tribological properties of the aforementioned materials have been tested on a simple pin-on-disc apparatus. EN31 was chosen as the disc material because its hardness value is much higher than that of the pin materials used. The test materials were constructed in the form of spherical end pins to have point contacts and to reduce the depth of wear.FindingsIt has been observed that the polymeric (HDPE and UHMWPE) and ceramic materials (Alumina) are much better than the traditional metallic materials. The wear rate is very low for these materials owing to their self-lubricating properties.Practical implicationsThe experimental studies will help predict the performance and life of implant materials in the human body.Originality/valueIn most cases, SS316L that possesses nickel compositions is used as the disc material; SS316L is toxic to the human body. In the present study, a high carbon alloy steel with high degrees of hardness EN31 is used as a disc counter-face material.

Cao, Wei; Wang, Jiaxu; Pu, Wei; Zhang, Ying; Wu, Jiqiang; Ren, Si; Long, Jianbing

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-03-2016-0055

PurposePrevious studies were mainly focused on profile designation of bearing rollers and lubrication performance without considering roller-races skidding. However, the width of round corner, load, rotational speed and some other parameters have significant effects on the roller-races sliding speed. This paper aims to investigate the effect of round corner on lubricating characteristics between the heavily loaded roller and inner race considering skidding and roughness.Design/methodology/approachA mixed elastohydrodynamic lubrication (EHL) model which is capable of handling practical cases with 3D machined roughness is combined with the skidding model to investigate the effect of round corner on lubricating characteristics between the heavily loaded roller and inner race.FindingsThe width of round corner and round corner radius have a desirable range under certain operating condition, within which the maximum pressure, stress and maximum flash temperature remain low. The optimized range is sensitive to the operating condition. Roughness and skidding narrow the optimized range of round corner radius. Roughness increases the pressure peak, Mises stress and friction coefficient. At the same time, skidding and roughness have obvious effects on film thickness at the contact center area if the round radius is small.Research limitations/implicationsThis paper uses the Harris skidding model that has a relatively bigger error, which is not accurate if the bearing load is less.Practical implicationsThis paper unifies the skidding model and mixed EHL model which can be used as a tool for optimization design and lubricating performance analysis of cylindrical roller bearing.Originality/valueLubrication analyses for roller bearing are assumed to be pure rolling contact between roller and races in a previous study, which could not reflect the real contact characteristics. The skidding model is merged into a mixed EHL model which can be used as a dynamic tool to analyze the lubricating performance considering the round corner, skidding and roughness.

Khatri, Chandra B.; Sharma, Satish C.

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-07-2016-0163

PurposeThe aim of the present paper is to study the combined influence of textured surface and micropolar lubricant behaviour on the performance of two-lobe hole-entry hybrid journal bearing system. The bearing performance parameters of the textured circular/two-lobe hole-entry hybrid journal bearing system have been computed against the constant vertical external load supported by the bearing.Design/methodology/approachIn this work, Eringen’s micropolar fluid theory has been used to derive the governing Reynolds equation. The consequent solution of the governing Reynolds equation has been obtained by using finite element method (FEM) numerical technique.FindingsThe present study indicates that the use of the textured surface, two-lobe profile of bearing and micropolar lubricant, significantly enhances the bearing performance as compared to non-textured circular journal bearing.Originality/valueThe present study concerning the influence of surface texturing on the behaviour of the two-lobe hole-entry hybrid journal bearing lubricated with micropolar lubricant is original. The theoretically simulated results of the present study will be useful to design an efficient journal bearing system.

Zheng, Baochao; Huang, Zhifu; Xing, Jiandong; Xiao, Yiyang; Xiao, Fan

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-08-2016-0195

PurposeThis paper aims to demonstrate the effect of varying chromium content on the wear behavior of white cast iron, to study the interaction relationship between cementite and pearlite in white cast iron, while estimating their contribution rate in abrasive wear.Design/methodology/approachTo study interaction of cementite-pearlite of white cast irons with different chromium content in three-body abrasive wear, three kinds of chromium white cast iron, bulk single-phase cementite, pure pearlite samples and the white cast iron (WCI), were prepared using the melting and casting technique. The so-called pure pearlite samples have the same chemical composition, microstructure and properties as the pearlite matrix in white cast iron.FindingsResults indicated that the interaction has a negative value. Its absolute value decreased with increasing chromium addition. Meanwhile, a high load resulted in an increased interaction value. The contribution rate of cementite to interaction, which was higher than that of pearlite, increased with increasing chromium addition. This indicated cementite was a main phase. Besides, the reductive size of abrasive has a significant effect on the contribution rate at the high load. These prominent cementite occurred fracture, when small size abrasive indented the matrix. These result in the absence of a protective effect of cementite during wear process. Eventually, the contribution rate of cementite decreased significantly.Originality/valueThis paper demonstrates the effect of varying chromium content on wear behavior of white cast iron, to study the interaction relationship between cementite and pearlite in white cast iron while estimating their contribution rate in abrasive wear.

Cai, Jianhua

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-12-2015-0200

PurposeThis paper aims to explore a new way to extract the fault feature of a rolling bearing signal on the basis of a combinatorial method.Design/methodology/approachBy combining local mean decomposition (LMD) with Teager energy operator, a new feature-extraction method of a rolling bearing fault signal was proposed, called the LMD–Teager transform method. The principles and steps of method are presented, and the physical meaning of the time–frequency power spectrum and marginal spectrum is discussed. On the basis of comparison with the fast Fourier transform method, a simulated non-stationary signal was processed to verify the effect of the new method. Meanwhile, an analysis was conducted by using the recorded vibration signals which include inner race, out race and bearing ball fault signal.FindingsThe results show that the proposed method is more suitable for the non-stationary fault signal because the LMD–Teager transform method breaks through the difficulty of the Fourier transform method that can process only the stationary signal. The new method can extract more useful information and can provide better analysis accuracy and resolution compared with the traditional Fourier method.Originality/valueCombining the advantage of the local mean decomposition and the Teager energy operator, the LMD–Teager method suits the nature of the fault signal. A marginal spectrum obtained from the LMD–Teager method minimizes the estimation bias brought about by the non-stationarity of the fault signal. So, the LMD–Teager transform has better analysis accuracy and resolution than the traditional Fourier method, which provides a good alternative for fault diagnosis of the rolling bearing.

Lin, Bingjing; Tieu, A. Kiet; Zhu, Hongtao; Kosasih, Buyung; Novareza, Oyong

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-07-2016-0161

PurposeThis paper aims to assess the adsorption behaviour and the adhesion strength of lubricant films formed by polypropylene oxide-polyethylene oxide-polypropylene oxide (PPO-PEO-PPO) with phosphate ester additive on Ti-coated surface and to identify the influence of molecular architecture and phosphate ester additive.Design/methodology/approachThe thickness of the adsorbed PPO-PEO-PPO with phosphate ester lubricant films on Ti surfaces was measured by ellipsometry. The adhesion strength of the copolymer and the copolymer with phosphate ester lubricants was studied by the micro-scratch tests; the scratch tracks on the surfaces were observed by atomic force microscopy and scanning electronic microscopy.FindingsThe copolymer with a higher weight percentage of PPO not only formed a thicker film but also showed stronger adhesion and better lubrication performance. The added phosphate ester increased the film thickness and improved the tribological behaviour. The finding reveals that the adsorbed film thickness which depends on the PPO chain length and the presence of phosphate ester has a considerable effect on the scratch behaviour.Originality/valueThis paper fulfils the studies about adsorption behaviour and lubrication mechanism of this new lubricant which has not been adequately investigated on the metal surface.

Xue, Weiguo; Ma, Wenquan; Xu, Xiaohong; Li, Tao; Zhou, Xuguang; Wang, Peng

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-04-2016-0082

PurposeThiadiazole compounds and their derivatives have carrying capacity and good lubricating properties. However, their poor oil-solubility limited their wide usage in lubricating oil. The study aims to develop thiadiazole lubricant additives with better oil-solubility. When the hindered phenol antioxidation functional group and alkyl-chain are introduced to thiadiazole, the resulting product could have better oil-solubility and excellent antioxidation resistance, anti-wear and corrosion resistance in the lubricating oil.Design/methodology/approachOne kind of thiadiazole lubricant additive, for the first time, has been synthesized from 2,5-dimercapto-1,3,4-thiadiazole. Its tribological performance has also been evaluated by four-ball test. And, its oxidation resistance has been estimated by rotating pressure vessel oxidation test and pressurized differential scanning calorimetry. The anticorrosion performance of such an additive has been studied by GB/T 5096 standard method test.FindingsThe synthesized thiadiazole additive has excellent anti-oxidation capability, good anti-wear and extreme pressure properties and good anticorrosion performance, in comparison with zinc dialkyl dithiophosphate (ZDDP). In base oils, the comprehensive performance of thiadiazole additive is comparable to ZDDP. Mechanistic studies indicate that the S and N active elements were involved in the formation of a boundary film. This may account for the formation of a composite membrane on the metal surface and thus for the tribological performance of such thiadiazole additives.Originality/valueThe thiadiazole derivatives, which are ashless and have environmentally friendly features, are a potential alternative to ZDDP. Because of the film formed on the friction surface, thiadiazole compounds may serve as an excellent anti-wear additive and are expected to reduce friction and wear between metals.

Labiapari, Wilian da Silva; Costa, Henara Lillian; De Mello, José Daniel Biasoli

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-06-2016-0131

PurposeThe progressive wear of cutting tools used in industrial cutlery production results in excessive burr formation and reduces tool service life. This paper aims to investigate the effects of the sheet surface finish on tool wear and service life during blanking.Design/methodology/approachTwo alternative surface finish techniques were proposed and initially implemented under laboratorial conditions and compared with conventional acid pickling. Those surface finish techniques were then implemented on an industrial scale to improve the service life of cutting tools. Industrial blanking tests characterized the effect of sheet surface finish on tool life.FindingsIn the first technique, called skin pass, an additional mechanical pass under controlled conditions reduced the height of the surface peaks and resulted in partial embedding of the carbides into the surface. The second technique, called electrochemical pickling, removed solely the surface carbides, leaving behind a smoother surface without carbides. Real industrial blanking tests identified that the use of skin pass reduced burr formation and increased tool life by around 300 per cent when compared with conventional acid pickling. With electrochemical pickling, burr formation was further reduced and tool life increased further by 300 per cent when compared with skin pass.Research limitations/implicationsFirst, this work proposes an alternative surface finishing technique (electrochemical pickling) to be used after annealing of stainless steel. Second, the work clearly shows the presence of protruding surface carbides when conventional surface finishing techniques are used, which do not exist after acid pickling.Practical implicationsWhen electrochemical pickling is implemented on an industrial scale, the life of blanking tools is substantially improved.Originality/valueAlthough the sheet surface finish is widely recognized to affect metalforming processes, the literature lacks studies on the effect of sheet surface finish on tool wear during blanking. First, this work proposes an alternative surface finishing technique (electrochemical pickling) to be used after annealing of stainless steel. Second, the work clearly shows the presence of protruding surface carbides when conventional surface finishing techniques are used, which do not exist after acid pickling. Third, when electrochemical pickling is implemented on an industrial scale, the life of blanking tools is substantially improved.

Zha, Jun; Chen, Yaolong; Zhang, Penghai

2017 Industrial Lubrication and Tribology

doi: 10.1108/ILT-08-2016-0192

PurposeThe form error of shaft and hole parts is inevitable because of the machining error caused by rotation error of tool axis in machine tools where the elliptical form error is the most common in shaft and bearing bush. The purpose of this paper is to present the relationship between the elliptical form error and rotation accuracy for hydrostatic journal bearing in precision spindle and rotation table.Design/methodology/approachAn error averaging effect model of hydrostatic journal bearing is established by using Reynolds equation, pressure boundary conditions, flux continuity equation of the land and kinetic equation of shaft in hydrostatic journal bearing. The effects of shaft and bearing bush on rotation accuracy were analyzed quantitatively.FindingsThe results reveal that the effect of shaft elliptical form error on rotation accuracy was six times larger than bearing bush. Therefore, to improve the rotation accuracy of hydrostatic journal bearing in spindle or rotation table, the machining error of shaft should be controlled carefully.Originality/valueAn error averaging model is proposed to evaluate the effect of an elliptical form error on rotation accuracy of hydrostatic journal bearings, which solves the Reynolds equation, the flux continuity equation and the kinetic equation. The determination of form error parameters of shaft and bearing bush can be yielded from finding results of this study for precision design of hydrostatic journal bearings.