• Journal of Ocean Engineering and Technology
• /
• v.23 no.6
• /
• pp.99-104
• /
• 2009

PTFE has good mechanical and chemical stability at a wide range of temperatures and demonstrates a low friction coefficient value. PTFE is being used for self-lubricating parts in industry. But it shows a high wear rate. Thus, PTFE and nano-diamond powder were mixed into a composite and the wear properties of a PTFE coating layer on Al6061 was investigated. A ball-on-disk type of wear tester was used under a dry condition and different temperatures of oil. After the wear test, the wear track wasexamined by optical microscope. The PTFE-diamond showed the lowest friction coefficient (0.02) of all the lubricants in the experiments. The friction coefficient was shown to be directly related to the diamond powder in the PTFE coating. Adhesion estimations were performed by a scratch test, which is mainly used for coatings. The critical load between the coating and substrate was defined through analyses of the friction load, normal load curve, and acoustic emissions, along with optical microscope observations. The scratch test results showed that an import item (SWISS) gave the highest critical load values.

• Korean Journal of Computational Design and Engineering
• /
• v.10 no.5
• /
• pp.375-379
• /
• 2005

Durability of rubber dust cover in the ball joint for automotive suspension parts is analyzed by FEM and compared with experimental data. Upper open area of ball joint is sealed by dust cover for preventing outflow of the lubricating oil and intrusion of send, dust, water, etc. This rubber cover undergoes repeated loadings such as tension and compression while the car is running. Analysis about rubber material needs to consider every kinds of nonlinearities arise in finite element analysis, which are geometric nonlinearity due to large displacement and small strain, materially nonlinearity and nonlinear boundary condition such as contact. The deformation behavior of dust cover is analysed by using the commercial finite element program MARC. In the study, this program could solve these kinds of nonlinear analysis accurately. Finite element model of dust cover is considered as 3-dimensional half model based on 2-dimensional axisymmetric model. Material property of rubber is modeled by Ogden model and input data for calculation takes form uniaxial tension test of rubber specimen. The final object of the study is obtaining the design specification of dust covers and the result of analysis should be a useful data to design of rubber cover.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.153-153
• /
• 2016

Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1 MeV electron beam energy in five doses (100, 200, 300, 500 and 700 KGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using Pin on disk tribometer, Raman spectroscopy, SEM-EDS, Optical microscopy, 3D Nano surface profiler system and Contact angle analyzer. Electron beam irradiation at a dose of 100 kGy resulted in a decrease of the friction coefficient and wear loss of POM-C block due to well suited cross-linking, carbonization, free radicals formation and energetic electrons-atoms collisions (physical interaction). It also shows lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation doses at 200, 300, 500 and 700 kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The electron beam irradiation transferred the wear of unirradiated POM-C block from the abrasive wear, adhesive wear and scraping to mild scraping for the 1 MeV, 100 kGy irradiated POM-C block which is concluded from SEM-EDS and Optical microscopic observations. The degree of improvement for tribological attribute relies on the electron beam irradiation condition (energy and dose rate).

• Archives of Plastic Surgery
• /
• v.38 no.3
• /
• pp.333-337
• /
• 2011

Purpose: Various operations have been proposed to compensate for congenital absence of the vagina using ileal or colonic interposition. These methods involve laparotomy, which shows postoperative complications such as long scar and delayed recovery. One case of neovagina reconstruction with laparoscopic rectosigmoid colpopoiesis in Mayer-Rokitansky-Kuster-Hauser syndrome is presented to avoid laparotomic complications. Methods: Laparoscopic surgery was performed in a 27-year-old MRKH syndrome patient. After a cruciate incision, blunt dissection through two-finger wide space was created between the bladder and the rectum. A 14-cm rectosigmoid segment vascularized by a branch of sigmoid artery was isolated by laparoscopy. The distal end was sutured with vaginal vestibule mucosa. A continuity of intestine was restored by circular end-to-end proximate curved intraluminal stapler CDH29$^{(R)}$ through perineal opening. Results: Total operation time was 4 hr 15 min. Normal walking and ingestion were possible within 3 days and 4 days after surgery. The hospital stay was 7 days and the patient was followed up for 6 months. The neovaginal introitus was wide enough for inserting two fingers, and there has been no narrowing of the neovagina on palpation as confirmed by vaginogram. The patient had functional self-lubricating neovagina without excessive mucous production or the need for routine dilation or unnoticeable scar. Conclusion: The successful result of this laparoscopic vaginal reconstruction technique with rectosigmoid segment suggests that this technique can be considered for the option of vaginal reconstruction in girls with the MRKH syndrome.

• Tribology and Lubricants
• /
• v.39 no.6
• /
• pp.235-243
• /
• 2023

This paper presents the fabrication process of water-lubricated plastic bearings. Plastic bearings require good mechanical properties and tribological properties as well as elasticity and shock resistance, especially when lubricated in dirty water conditions. In this study, sleeve-type plastic bearings are produced by winding a prepreg sheet, which primary contains nitrile rubber (NBR)-modified epoxy, self-lubricating fillers, and various types of lattice-structured reinforcing fibers such as carbon, Aramid, and polyethylene terephthalate. A thermosetting epoxy is chemically modified with NBR to impart elasticity and low-friction characteristics in water conditions. Experimental investigations are conducted to examine the mechanical and tribological characteristics of the developed bearing materials, and the results are compared with the characteristics of a commercial plastic bearing (Thordon SXL), well known as a water-lubricated bearing. A Thordon bearing (mainly composed of polyurethane) exhibits an extremely low load-bearing capacity and is thus only suitable for medium loading (1~10MPa). The tribological characteristics of the test materials are evaluated through Falex block-on-ring (LFW-1) friction and wear tests. The results indicate that friction exhibited by the carbon-fiber-reinforced NBR-10wt.%-modified epoxy composite material, incorporated with the addition of 20wt.% UHMWPE and 6wt.% paraffin wax, is lower than that of the Thorden bearings, whereas its wear resistance surpass that of Thorden ones. Because of these features, the load carrying capacity of the fabricated composite (>10MPa) is higher than that of the Thorden bearings. These results confirm the applicability of water-lubricated plastic bearing materials developed in this study.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.4
• /
• pp.878-885
• /
• 2008

The FPDs(Flat Panel Displays) such as LCD(Liquid Crystal Display) and PDP(Plasma Display Panel) and OLED(Organic Light Emitting Diode), recently, have been substituted for CRT(Cathode Ray Tube) displays because they have a convex surface, small volume, light weight and lower electric power consumption. The productivity of FPDs is greatly dependent on the area of thin glass panel with 0.6 - 0.8mm thickness because FPDs are manufactured by cutting a large-scaled thin glass panel with patterns to the required product dimensions. So FPD's industries are trying to increase the area of thin glass panel. For example, the thin glass panel size of the 8th generation is 2,200mm in width, 2,600mm in length and 0.7mm in thickness. The air flows both in the thin glass panel and in the porous PE-plate surface were modeled and analyzed, from which a working condition was estimated. The thin glass panel on the porous PE-plate surface with self-lubricating characteristics was investigated and compared with that on the square duct floating bar surface with many holes of 1mm diameter when the thin glass panel contacts the floating bar surface due to malfunction of electric power supply.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2009.05a
• /
• pp.111-112
• /
• 2009

Diamond-like carbon (DLC) is a convenient term to indicate the compositions of the various forms of amorphous carbon (a-C), tetrahedral amorphous carbon (ta-C), hydrogenated amorphous carbon and tetrahedral amorphous carbon (a-C:H and ta-C:H). The a-C film with disordered graphitic ordering, such as soot, chars, glassy carbon, and evaporated a-C, is shown in the lower left hand corner. If the fraction of sp3 bonding reaches a high degree, such an a-C is denoted as tetrahedral amorphous carbon (ta-C), in order to distinguish it from sp2 a-C [2]. Two hydrocarbon polymers, that is, polyethylene (CH2)n and polyacetylene (CH)n, define the limits of the triangle in the right hand corner beyond which interconnecting C-C networks do not form, and only strait-chain molecules are formed. The DLC films, i.e. a-C, ta-C, a-C:H and ta-C:H, have some extreme properties similar to diamond, such as hardness, elastic modulus and chemical inertness. These films are great advantages for many applications. One of the most important applications of the carbon-based films is the coating for magnetic hard disk recording. The second successful application is wear protective and antireflective films for IR windows. The third application is wear protection of bearings and sliding friction parts. The fourth is precision gages for the automotive industry. Recently, exciting ongoing study [1] tries to deposit a carbon-based protective film on engine parts (e.g. engine cylinders and pistons) taking into account not only low friction and wear, but also self lubricating properties. Reduction of the oil consumption is expected. Currently, for an additional application field, the carbon-based films are extensively studied as excellent candidates for biocompatible films on biomedical implants. The carbon-based films consist of carbon, hydrogen and nitrogen, which are biologically harmless as well as the main elements of human body. Some in vitro and limited in vivo studies on the biological effects of carbon-based films have been studied [$2{\sim}5$].The carbon-based films have great potentials in many fields. However, a few technological issues for carbon-based film are still needed to be studied to improve the applicability. Aisenberg and Chabot [3] firstly prepared an amorphous carbon film on substrates remained at room temperature using a beam of carbon ions produced using argon plasma. Spencer et al. [4] had subsequently developed this field. Many deposition techniques for DLC films have been developed to increase the fraction of sp3 bonding in the films. The a-C films have been prepared by a variety of deposition methods such as ion plating, DC or RF sputtering, RF or DC plasma enhanced chemical vapor deposition (PECVD), electron cyclotron resonance chemical vapor deposition (ECR-CVD), ion implantation, ablation, pulsed laser deposition and cathodic arc deposition, from a variety of carbon target or gaseous sources materials [5]. Sputtering is the most common deposition method for a-C film. Deposited films by these plasma methods, such as plasma enhanced chemical vapor deposition (PECVD) [6], are ranged into the interior of the triangle. Application fields of DLC films investigated from papers. Many papers purposed to apply for tribology due to the carbon-based films of low friction and wear resistance. Figure 1 shows the percentage of DLC research interest for application field. The biggest portion is tribology field. It is occupied 57%. Second, biomedical field hold 14%. Nowadays, biomedical field is took notice in many countries and significantly increased the research papers. DLC films actually applied to many industries in 2005 as shown figure 2. The most applied fields are mold and machinery industries. It took over 50%. The automobile industry is more and more increase application parts. In the near future, automobile industry is expected a big market for DLC coating. Figure 1 Research interests of carbon-based filmsFigure 2 Demand ratio of DLC coating for industry in 2005. In this presentation, I will introduce a trend of carbon-based coating research and applications.