• Transactions of Materials Processing
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• v.12 no.2
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• pp.83-87
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• 2003

Current state of plastic processes of steel bearing parts is surveyed. According to the advances in plastic forming technologies and their great advantage to mass production, plastic processes are adopted in manufacturing majority of bering parts. The rings are forged or ring rolled and the rolling elements, i.e, balls or rollers are cold formed before fine machining. Bearing's steel retainers are mainly press formed using cold rolled seel strips. Including the general explanation about above processes, some details of forging technology, control of forging temperature and after cooling process, and examples of computer simulation are described.

• Tribology and Lubricants
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• v.39 no.1
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• pp.1-7
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• 2023

Fluid pumps in chemical processes are typically driven by electric motors. Even if the motor is separated from the pump with seals, wear resulting from friction and misalignment can lead to leakage of chemical fluid, causing corrosion in the bearing supporting the motor, and, eventually, failure of the motor. It is thus a standard procedure to replace bearings at regular intervals. In this article, we propose 3D-printed plastic ball bearings for use as an alternative to commercial stainless-steel ball bearings. The plastic bearings are easy to manufacture, require less time to replace, and are chemically resistant. To validate the applicability of the plastic bearings, we first conducted chemical resistance tests. Bearings were immersed in 30 caustic acid and 30 nitric acid for 30 min and 24 h, respectively. The test results showed no corrosive damage to the bearings. A test rig was set up to compare the performance of the plastic bearings with that of the commercially equivalent deep-groove ball bearings. Loading test results showed that the plastic bearings performed as well as the commercial bearing in terms of vibration level and load-handling capability. Finally, a plastic bearing was subjected to a clean-in-place process for three months. It actually outperformed the commercial bearing in terms of chemical resistance. Thus, 3D-printed plastic bearings are a viable alternative to stainless-steel ball bearings.

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

• Archives of Plastic Surgery
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• v.46 no.6
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• pp.566-571
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• 2019

Background In Western nations, hidradenitis suppurativa (HS) typically affects the apocrine gland-bearing skin of people of African origin, women, smokers, and individuals with obesity. The clinical characteristics of HS in Korea and Japan, however, are reportedly different from those in the West. We therefore hypothesized that wet earwax is associated with HS because most East Asian people are genetically predisposed to produce dry earwax. Methods The medical charts of 53 Japanese patients with HS were reviewed retrospectively. Results Unlike the results of surveys conducted in Western nations, most of our patients were men (72%), whose buttocks were the most commonly affected site. Apocrine gland-bearing areas, such as the axilla, were affected less often. The proportion of HS patients with wet earwax was 51%, which was substantially higher than that found in the general Japanese population. Moreover, when patients with gluteal HS were excluded, the proportion of patients with wet earwax became even higher (68%). Conclusions Although the etiology of HS is unknown, our survey indicated that HS in apocrine gland-bearing skin, such as the axillary and anogenital areas, may be associated with wet earwax. As this study was conducted in a limited clinical setting, a nationwide, multicenter survey is warranted to clarify the clinical characteristics of HS in Japan.

• Steel and Composite Structures
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• v.20 no.3
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.1-5
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• 2009

Recent growth in global economic situation has led dramatic increase in new buildings of large containerships. These increased new building orders have brought keen concerns of developing and improving the quality of design and increasing the productivity of the vessel in order to satisfy the ship Owner's various requirements. For the increment of productivity and quality of containership, the plastic type bearing pad of cargo hatch cover has been investigated intensively for years with the supplier of cargo hatch cover. The result of investigation showed that there are numbers of advantages for the Owner and Builder over the existing bronze bearing pads which are better corrosion resistance long life time, low friction coefficient, easy maintenance, easy installation, better production lead time and low maintenance cost.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1492-1499
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• 2004

In this paper, defect formation in ring rolling is revealed by computer simulation of ring rolling processes. The rigid-plastic finite element method is employed for this study. An analysis model having relatively fine mesh system near the roll gap is used for reducing the computational time and a scheme of minimizing the volume change is applied. The formation of the central cavity formation defect in ring rolling of a taper roller bearing outer race and the polygonal shape defect in ring rolling of a ball bearing outer race has been simulated. It has been seen that the results are qualitatively good with actual phenomena.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.100-107
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• 2005

The objective of the study is to improve the quality of wheel bearing hub by the rigid-plastic finite element analysis and the response surface methodology. The rigid-plastic finite element codes, AFDEX-2D and DEFORM-3D, were used to analyze the two-dimensional and three-dimensional forging processes, respectively. The response surface analysis is used to find the minimum underfill by the variation of design variables such as the height of billet after upsetting and punch angles of blocker dies. The metal flow of forged product shows good agreement with the results from 2D and 3D analysis. Also, the quality of the wheel bearing hub has been improved by the optimization of design variables and the machining time has been reduced by the machining allowance.

• Steel and Composite Structures
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• v.11 no.1
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• pp.1-19
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• 2011

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

• Archives of Reconstructive Microsurgery
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• v.9 no.2
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• pp.110-113
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• 2000

The reconstruction of soft tissue defects of the sole requires to stand the force of weight bearing, provide sensation and adequacy for normal foot-wear. Although certain local flaps have been described and used for resurfacing the foot, extensive injury requires distant or free flaps for coverage. There is no doubt that the ideal tissue for resurfacing the sole is the plantar tissue itself. The specialized dermal-epidermal histology and fibrous septa of the subcutaneous layer gives its unique property to stand the pressure and to absorb the shock upon gait. This paper presents a case of reconstructing the sole that involves about 70% of the weight bearing portion. The combined medial plantar and dorsalis pedis chimeric free flap based on the medial plantar artery and medial plantar nerve adds another dimension in resurfacing the weight bearing sole of moderate to large sized defects.