The International Session, “The 53rd JAST Fall Tribology Conference International, ” was held on September 17 and 18th, 2008, in the 53rd Japanese Society of Tribologists (JAST) Fall Meeting in order to promote internationalization of the conference and activity of JAST. In this session, contributed papers on any subjects were welcomed. A total of sixteen presentations were made in four sessions; Micro/Nano Tribology, Lubrication & Oils, Friction & Wear, and Novel Tribo Surfaces.
After presented at the International Session, papers submitted to this International Journal “Tribology Online (TROL)” were published timely in this special issue through the normal peer review process by multiple reviewers. In this special issue, eight papers are published.
As the Chief Organizer of the International Session, I appreciate the speakers who presented their papers at the International Session and the member of the Organizing Committee. The Editorial Committees wishes to express their appreciation to all the authors who submitted their papers to this International Journal. As the Associate Editor, I would like to express my sincere thanks to the Editors-in-Chief, the Reviewers, and the Publication Coordinators for their effort to complete the peer-review processes and the publication work under the tight schedule.
Chief Organizer of the International Session, Associate Editor Kenji Fukuzawa
Nitriding of tool steel was investigated in a controlled electron beam excited nitrogen plasma environment. The samples were nitrided in two distinct regions, a region with high plasma density and a region with low plasma density called the irradiated and non-irradiated region, respectively. The experimental results confirm the formation of the brittle compound layer in treating the sample in the irradiated region of the process chamber whereas, the samples treated in the non-irradiated region produced diffusion based nitriding without the compound layer. The hardness measurements of the samples nitrided in both regions were more than two times the hardness of the untreated samples. The overall results of our experiments show that nitriding of tool steels can be performed in a controlled plasma nitriding environment to produce surfaces with or without the compound layer depending on the required surface.
Adherence of carbon nanotube film made by surface decomposition of SiC was studied. For this purpose we carried out scratch tests in nano- and microscale. By microscratch test, it was found that adherence at the interface was higher for CNT films with shorter CNTs and CNTs were not broken at the middle but removed from the interface. To clarify the dominant force (shear force or moment of force) which caused different adherence, we also carried out nanoscratch test by using AFM. In nanoscratch, AFM tip made of diamond coated silicon applied shear force to CNT films from lateral direction. And there was no significant change of adherence by lateral force (shear force at the interface). We conclude that bending-induced moment of force is dominant on the interface strength of CNT films.
Improvement of the sensitivity of a dual-axis probe for friction force microscopy is presented. The dual-axis micro-mechanical probe combines a double cantilever and torsion beams. This probe could reduce the mechanical cross-talk between the lateral and vertical force detections. In addition, dual-axis forces can be detected by measuring the dual-axis displacement of the probe end using the optical lever-based method. A low reflection region is formed at the probe end. The region is irradiated with an optical lever laser light and the reflected light is focused onto a four-segmented photo diode (PD). The lateral force can be detected by measuring the displacement of the probe end using the dark region displacement on PD. A shallow step structure was used as a low reflection region in our previous study. However, its darkness was not enough and the improvement of the sensitivity was difficult. In this paper, a new type of low reflection region is presented. The low reflection region using a slope-structure could improve the lateral deflection sensitivity by a factor of 1.4 as compared with conventional one. And the minimum detection limits of the lateral deflection and force were of the order of 1 nm and 1 nN, respectively. This leads to accurate investigation of nanotribological phenomena.
The adhesion force between a chloride-isobutene-isoprene rubber (CIIR) and stainless steel ball was studied in this paper. In order to decrease the adhesion force, the CIIR rubber was treated with high-density microwave plasma employing oxygen and argon gases. The experimental results showed that the adhesion force decreases with increasing treatment time and microwave power following both oxygen and argon plasma treatments. In addition, optical measurements revealed that the real contact area between a CIIR rubber and quartz plate decreases with decreasing adhesion force. The decreasing trend of the contact area was almost similar to that of the adhesion forces. The field emission scanning electron microscope image showed that the surface roughness generally increases with treatment time and microwave power, implying that roughening of rubber surface by plasma treatment is one of the reasons for the decrease in the adhesion force.
The purpose of this paper is to measure the non-linear dynamic properties of O-rings in wide frequency ranges including in the ultra-high-speed rotational regions and to calculate the stability threshold of herringbone grooved aerodynamic journal bearings with O-rings support. First, the Voigt model was used as a rheological model of the O-rings, and the spring and the damping coefficients were evaluated in a wide frequency range from 0.5 to 4 kHz. Then, the stability threshold of the herringbone grooved aerodynamic journal bearings supported by O-rings was calculated. In this calculation, the compressible Reynolds equation based on the Narrow Groove Theory was solved by the perturbation method. Finally, the theoretical results were compared with the experimental results. The calculated results had a good agreement with the experimental ones
The tribological problem in natural sand dust environment was proposed and an equipment for simulating the natural sand dust environment based on Multi-Venturi structure was introduced for studying the tribological problem. The wear performance of polymer tapes in sand dust environment was evaluated by using a roller-scraper tribosystem. Three typical wear models including cutting, wedge forming and ploughing during the intrusion of sand particle into the contact interface of polymer materials were found. The abrasive wear mechanisms were discussed with particle intrusion mechanism.
The purpose of this paper is to clarify the friction and wear properties of the architectural membrane sliding against the steel. Different matrix materials for the architectural membrane as PVDF (Polyvinyliden Fluoride), PVF (Polyvinyl Fluoride) and PTFE (Polytetra Fluore Ethylen) were prepared and fixed on a steel disk. Some steel pins were used in the pin-on-disk sliding test against steel disk covered with membranes. Friction tests were conducted with different load and sliding velocity as 2-60 N and 0.02-0.20 m/s, respectively. The results showed that the friction coefficient is independent on the sliding velocity for all materials. On the other hand, contact load changed the friction coefficient well, especially for the PVDF. Friction coefficient of PVDF composite material sliding against bearing steel is lower than PTFE and PVF. On the other hand, PTFE showed lowest friction of all when μpv is more than 0.005 MPa m/s. Comparing with three membrane materials, PTFE membrane shows the lowest friction coefficient and highest wear resistance of all.
The purpose of this paper is to investigate stiction properties of suction cups on a flat surface and find out empirical rule of stiction. For this purpose, contact areas on SUS304 plate of three kinds (#40, 240, 400) of roughness under dry and wet contact conditions are made and pull-off test was carried. The SUS304 plate was fixed in the lower chuck of the tension tester, and the suction cup was chucked in the upper part of the tension tester. It is pushed by tension tester with initial compressive force Pc on the SUS304 plate, and then loaded by pulling force P at speed V=20 mm/min. In the whole pull-off process, the maximum pulling force (Pmax) and the final pull-off force (Poff) were observed. In conclusion, the empirical rule of stiction of suction cup : Pmax=σA, where Pmax[N], A [m2] and σ[Pa] are confirmed to exist, the σ is the constant depending on the roughness and dry or wet of plate surface.