超微細粒鋼創製プロセスのためのトライボロジー条件とその評価

In order to reduce the rolling force and the roll wear, the lubricants have been used in hot sheet rolling of steel, but the lubrication behavior at the interface between roll and workpiece in hot steel rolling have never been well understood. On the other hand, hot rolling process with high reduction in thickness have been developed to produce the ultra-fine grained steels. The high reduction in hot rolling causes some troubles such as the increase of the rolling force, the occurrence of friction pick up and so on. To solve these problems, the lubrication behavior at the interface between roll and workpiece in hot steel rolling must be quantitatively understood. In this paper, the coefficients of friction were measured by using the newly developed simulation testing machine for hot rolling. The effects of lubricant factors such as the compositions and the viscosity of the base oil and the additive agents on the coefficient of friction were investigated. From these experimental results, the lubrication behavior at the interface between roll and workpiece was investigated and the lubrication mechanism was proposed.

Using pure water in comparison to water-based lubricant containing 4% TiO2 nanoparticles (NPs), the hot rolling tests of 304 stainless steel were carried out at a rolling temperature of 1050 °C under varying rolling reductions and speeds. The effects of lubrication on rolling force, torque, power and contact friction were systematically investigated. The coefficient of friction (COF) during steady-state hot steel rolling was inversely calculated using a developed flow stress model. The COF models including the effects of rolling reduction and speed were proposed via multiple linear regression. The results indicated that the use of the nanolubricant enabled a reduction of rolling force up to 6.1% and decreases in rolling torque and power up to 21.6%, compared to that of water condition. The results obtained from the linear regression agreed well with those from the inverse calculation, suggesting the developed COF models had high accuracy. The lubrication mechanisms were derived from a boundary lubrication regime, owing to ball bearing and mending effects of TiO2 NPs, and formation of thin lubricant film under high rolling pressure.

The tribological properties of chemical-vapor-deposited (CVD) diamond films vary with the environment, possessing a Jekyll-and-Hyde character. CVD diamond has low coefficient of friction and high wear resistance in air but high coefficient of friction and low wear resistance in vacuum. Improving the tribological functionality of materials (such as achieving low friction and good wear resistance) was an aim of this investigation. Three studies on the surface design, surface engineering, and tribology of CVD diamond have shown that its friction and wear are significantly reduced in ultrahigh vacuum. The main criteria for judging whether diamond films are an effective wear-resistant, self-lubricating material were coefficient of friction and wear rate, which must be less than 0.1 and on the order of 10(exp 6) cu mm/N(dot)m, respectively. In the first study the presence of a thin film (less than 1 micron thick) of amorphous, nondiamond carbon (hydrogenated carbon, also called diamondlike carbon or DLC) on CVD diamond greatly decreased the coefficient of friction and the wear rate. Therefore, a thin DLC film on CVD diamond can be an effective wear-resistant, lubricating coating in ultrahigh vacuum. In the second study the presence of an amorphous, nondiamond carbon surface layer formed on CVD diamond by ion implantation significantly reduced the coefficient of friction and the wear rate in ultrahigh vacuum. Therefore, such surface layers are acceptable for effective self-lubricating, wear-resistant applications of CVD diamond. In the third study CVD diamond in contact with cubic boron nitride exhibited low coefficient of friction in ultra high vacuum. Therefore, this materials combination can provide an effective self-lubricating, wear-resistant couple in ultrahigh vacuum.

Serrated yielding behavior after cold and hot rolling of a high Mg content Al–Mg alloy

In the industrial rolling process of Al sheet, the cold rolling process practically follows immediately to hot rolling process without intermediate annealing. In this case, the hot rolling conditions may have effects on the anisotropy of final annealing sheets.So, we examined, by eare tests, these. effects on the anisotropy of final annealing sheets made of a semi-continuously cast slab (S. C. C. S.) and a book-mold cast slab (B. M. C. S.), both cold rolled in one way and cross way.The results obtained are as follows:(1) The ear values of sheets of S. C. C. S. are not always higher than those of B. M. C. S. but can be made even lower by selecting the proper hot rolling temperature, and are more severely affected by hot rolling temprerature than those of B. M. C. S., in which these effects are almost negligible. (See Fig. 8, 9)(2) Although it has been generally considered that the cross rolling gives lower ear value than one way rolling, it seems to be not always so. (See Fig. 8, 9)(3) In this experiment, both slabs were treated by the same processes after hot rolling, therefore the difference in anisotropies of final sheets made of both slabs should indicate the effects of orientation of cast grains resulted from both casting methodes.(4) The temper of as-hot-rolled plate at 400°C coresponds to I/2 H. When it is annealed, it softens gradually up to 450°C, but in high temperature annealing 600-640°C it rather hardens. (See Fig. 4) Consequently, ears of final annealed sheets become higher at 0-90° directions until the intermediate annealing temperature reaches about 400°C, but when the temperature rises over 400°C, the height of ear becomes lower and then finally the direction changes to 45°. (See Fig. 15)(5) The effects of hot rolling as the antecedents on mechanical properties, can be removed by subsequent intermediate or final annealing, but the effects on ears can never be removed. (See Fig. 13, 14, 15)(6) The pattern appeared on the anodized surface of the sheets made of S. C. C. S. can not be industrially removed by hot or cold rolling and annealing. The only way to cover it is cladding process.

This paper tests the friction between a popular design of rugby ball contacting the palm and three different designs of gloves. The gloves used were from the same manufacturer; one was made from synthetic leather, one had a round, pronounced silicon pattern of pimples and the final one had a silicon pattern with oval shapes cut into it. The friction of the contact was measured in dry conditions, with a small amount of water added to the palm/glove, a larger amount of water added to the palm/glove and finally a dry palm/glove contacting wet material. These tests showed the silicon designs of gloves gave a consistent measurement of coefficient of friction across all moisture levels. However, for the bare palm and the synthetic leather glove the coefficient of friction increased with a small amount of water and then decreased when more water was added. The synthetic leather glove was shown to have the highest coefficient of friction across all levels of water, with the silicon oval patterned glove having the lowest coefficient of friction in the majority of cases.

Hot rolling processes have been extensively used to produce round bars by reducing the cross‐sectional area of continuously cast steel. The current trend toward increasing productivity often requires a more aggressive reduction per pass. Establishing safe and optimized hot rolling parameters must be determined to avoid damage while deforming the specific steel composition. Understanding the damage mechanism during the metal forming process is vital for product quality. Herein, a combined experimental and simulation approach is developed to track the evolution potential damage during hot bar rolling. Hot tension tests are conducted on as‐cast vanadium microalloyed 15V38 steel at different hot rolling temperatures and strain rate conditions to develop Johnson–Cook‐type material model. A thermomechanical finite element model is developed to simulate potential damage trends in a 12‐pass square‐to‐round and 8‐pass round‐to‐round standard industrial hot rolling process, employing damage criteria. Results are illustrated by creating a damage map at each rolling pass to determine the critical hot rolling conditions for damage initiation. Several parametric studies are also performed to illustrate the application of the suggested methodology for hot rolling process optimization. Results show that the probability of the damage initiation is higher at higher pass reductions and lower temperatures.

Turbulence-like Cu/MoS2 films: Structure, mechanical and tribological properties

The vulva's higher capacitance, or skin hydration, leads it to have a higher friction coeffi cient, µ, which can be measured by the Newcastle Friction Meter. The vulva has a higher friction coeffi - cient at 0.66 ± 0.03, compared with the forearm at 0.48 ± 0.01 (7). This higher friction coeffi cient leads to increased vulva skin friction irritation from mechanical trauma, such as occlusion, clothing, sexual activity, and moisture occlusion from incontinence, which increases skin moisture, resulting in an even higher friction coeffi cient (7,8). Of note, the higher incontinence-related friction coeffi cient comes even more onto the front stage in postmenopausal women who suffer from vulvar skin atrophy in addition to incontinence issues, predisposing them even more so to increased vulvar irritation and dermatitis (9).

Spark-anodization of titanium can produce adherent and wear-resistant TiO2 film on the surface, but the spark-anodized titanium has lots of surface micro-pores, resulting in an unstable and high friction coefficient against many counterparts. In this study, the diamond-like carbon (DLC) was introduced into the micro-pores of spark-anodized titanium by the magnetron sputtering technique and a TiO2/DLC composite coating was fabricated. The microstructure and tribological properties of TiO2/DLC composite coating were investigated and compared with the anodic TiO2 mono-film and DLC mono-film. Results show that the DLC deposition significantly decreased the surface roughness and porosity of spark-anodized titanium. The fabricated TiO2/DLC composite coating exhibited a more stable and much lower friction coefficient than anodic TiO2 mono-film. Although the friction coefficient of the composite coating and the DLC mono-film was similar under both light load and heavy load conditions, the wear life of the composite coating was about 43% longer than that of DLC mono-film under heavy load condition. The wear rate of titanium with protective composite coating was much lower than that of titanium with DLC mono-film. The superior low friction coefficient and wear rate of the TiO2/DLC composite coating make it a good candidate as protective coating on titanium alloys.

Polydimethylsiloxane (PDMS) has many advantages, but the friction coefficient generated by contact with the counter material is high. The purpose of this study is to reduce the friction coefficient by forming hierarchical micro/nanopatterns on the PDMS surface using the imprinting method. In addition, the optimum conditions for reducing the friction coefficient by controlling the sliding speed and normal load were determined. After contacting flat bare PDMS and hierarchical micro/nanostructured PDMS with a counter tip made of polyurethane (PU), the change in friction with sliding speed and vertical load was evaluated. Under normal load conditions, the average friction coefficient of the bare PDMS decreased as the sliding speed increased, and that of the patterned PDMS slightly increased. Regardless of the sliding speed, the friction coefficient decreased as the normal load increased for both specimens. At a sliding speed of 4 mm/s under a load of 10 mN, the friction reduction effect of the pattern structure was the largest at 79%. Overall, the greatest friction reduction effect (84%) was confirmed in patterned PDMS with the lowest friction coefficient under the conditions of 4 mm/s, 50 mN, compared to bare PDMS with the highest friction coefficient under the conditions of 4 mm/s, 10 mN.

Effect of diesel-palm biodiesel fuel with plastic pyrolysis oil and waste cooking biodiesel on tribological characteristics of lubricating oil

High-temperature tribological behavior of Ti containing diamond-like carbon coatings with emphasis on running-in coefficient of friction

Designing polymeric coating with low coefficient of friction for natural rubber glove application

In this study, the tribological performance of polyamide‐6 (PA‐6), polypropylene (PP), polyamide‐6/polypropylene (PA‐6/PP) polymer blend, and nanoclay reinforced polyamide‐6/polypropylene composite are investigated. Nanoclay reinforced polymer composite is produced by melt compounding using co‐rotating twin screw extruder followed by injection moulding. Tribological studies are carried out using a pin‐on‐stainless steel disc configuration under dry sliding conditions. Tribological tests are carried out at sliding speed of 0.5 m s−1 and applied load values of 25, 50,100, 150 N. The friction coefficient and specific wear rate values are obtained and evaluated. The results show that the addition of nanoclay into the PA‐6/PP polymer blend reduced their coefficient of friction and specific wear rate values. The lowest coefficient of friction and specific wear rate values are for nanoclay reinforced PA‐6/PP blend. The highest coefficient of friction and specific wear rate values are for PA‐6 polymer.