• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.1042-1047
• /
• 2004

Urethane is a high polymeric and elastic material useful in designing mechanic parts that cannot be molded in rubber or plastic material. Especially, urethane is high in mechanical strength and anti-abrasive. Hereby, an urethane coated aluminum wheel is used for supporting of OHT vehicle moving back and forth to transport products. For the sake of verifying the safety of the vehicle, structural safety for applied maximum dynamic load on a urethane wheel needs to be carefully examined while driving. Therefore, we have performed the dynamic simulation on the OHT vehicle model. Although the area definition of applied load can be obtained from the previous study of Hertzian and Non-Hertzian contact force model when having exact properties of contact material, static analysis is simulated, since the proper material properties of urethane have not been guaranteed, after we have performed the actual contact area test for each load. In case of this study, the method of distributing load for each node is included. Finally, in comparison with result of analysis and load-displacement curve obtained from the compression test, we have defined the material properties of urethane. In the analysis, we have verified the safety of the wheel. After all, we have performed a mode analysis using the obtained material properties. With the result, we have the reliable finite element model.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.11
• /
• pp.1453-1459
• /
• 2011

A roller pinion gear (RPG) system composed of either a pin or a roller and its conjugated cam gear can improve the gear endurance from that of a conventional gear system by reducing the sliding contact while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection condition obtained when the profile shift coefficient is introduced. Then, we investigated the Hertzian contact stresses and the load stress factors while the varying the shape design parameters to predict the gear surface fatigue life, which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.10 s.175
• /
• pp.114-120
• /
• 2005

Urethane is a high polymeric and elastic material useful in designing mechanic parts that cannot be molded with rubber or plastic material. In particular, urethane is high in mechanical strength and anti-abrasive. Hereby, a urethane coated aluminum wheel is used to support of the OHT vehicle moving back and forth to transport products. For the sake of verifying the safety of the vehicle, structural safety fur applied maximum dynamic load on a urethane wheel must be examined carefully while driving. Therefore, we performed a dynamic simulation on the OHT vehicle model and we determined the driving load. The area definition of applied load may be obtained from the previous study of Hertzian and Non-Hertzian contact force model having exact properties of contact material. But the static analysis is simulated after we have performed the actual contact area test for each load since the proper material properties of urethane have not been guaranteed. In this study, the method of distributing loads for each node is included. Finally, in coMParison with the results of analysis and load-displacement curve obtained from the compression test, we have defined the material properties of urethane. In the analysis, we verified the safety of the wheel. Finally, we performed a mode analysis using the obtained material properties. With these results, we presented a reliable finite element model.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.9
• /
• pp.983-989
• /
• 2011

A numerical algorithm for predicting fretting wear was developed using the boundary element method (BEM). A contact analysis was performed numerically using the relation between the elastic displacement and uniformly distributed loading of a rectangular patch on a semi-infinite solid. Geometrical updating based on nodal wear depths was performed. The wear depths were computed using the Archard's equation for sliding wear. In order to investigate the efficiency of BEM for predicting fretting wear, a problem involving a two-dimensional cylinder on a flat contact was analyzed, comparing it with the simulation model proposed by McColl et al. that was based on the finite element method. The developed method was then applied to the analysis of a spherical contact and it was shown that the developed simulation technique could efficiently predict fretting wear. Moreover, the effect of a step cycle on the solution obtained by the developed method was investigated.

• Annals of Occupational and Environmental Medicine
• /
• v.34
• /
• pp.7.1-7.10
• /
• 2022

Background: Occupational skin diseases are skin conditions that occur or worsen in relation to work and known to be the second most common type of occupational disease affecting individuals in the United States. In Korea, epidemiological reports related to occupational skin diseases are rare. But, no cases of occupational contact dermatitis caused by welding and grinding work have been reported previously. Case presentation: Nine male workers working in the production department for liquefied natural gas (LNG) ships in Ulsan complained of erythematous papules/patches and itching in various areas of the body after welding and grinding work. The work environment monitoring report revealed that the amount of nickel dust exceeded the time weighted average (TWA) and poor local ventilation status. Based on the symptoms and the overall results of surveys, several tests, and work environment monitoring report, the 2 workers who had positive patch-test reactions to nickel were diagnosed with nickel dust-induced allergic contact dermatitis. The other 7 workers were diagnosed that there was a high probability that they had nickel dust-induced irritant contact dermatitis. The 2 workers who had nickel dust-induced allergic contact dermatitis were recommended to switch their jobs. Conclusions: Nickel is one of the most common cause of allergic contact dermatitis. In this case, the dust was assumed to be created by welding work with a high nickel content new welding rod and subsequent grinding work, and the concentration of this dust exceeded the time weighted average. Thus, it is thought that the nickel dust may have caused contact dermatitis through continuous contact with the workers' exposed skin in a poorly ventilated space. Currently, several domestic shipbuilding companies are manufacturing LNG tankers using a new construction method. Consequently, it is highly likely that similar cases will occur in the future, which makes this case report meaningful.

• Journal of Yeungnam Medical Science
• /
• v.3 no.1
• /
• pp.387-393
• /
• 1986

Antiseptics are substances that kill or prevent the growth of microorganisms when applied to living tissue. They must be effective against microoranisms but must also retain their activity in presence of body fluids without being harmful locally or systemically. Among many antiseptics. $Betadine^{(R)}$ has been widely used because of its low toxicity and high germicidal efficacy. We reported 2 cases of allergic contact dermatitis to $Betadine^{(R)}$ in surgical patients. They had eczematous eruption along the $Betadine^{(R)}$ applying sites. Patch tests with $Betadine^{(R)}$ confirmed the diagnosis.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.11
• /
• pp.1711-1718
• /
• 2004

When the tracked vehicle is running on various types of terrain, the physical properties of the interacting ground can be different. In this paper, the interactions between track link and soft soil ground are investigated using static sinkage theory of soil ground. Grouser surfaces of a track link and triangular patches of ground are implemented for contact detection algorithm. Contact force at each segment area of a track link is computed respectively by using virtual work concept. Bekker's static soil sinkage model is applied for pressure-sinkage relationship and shear stress-shear displacement relationship proposed by Janosi and Hanamoto is used for tangential shear forces. The repetitive normal loads of a terrain are considered because a terrain element is subject to the repetitive loading of the roadwheels of a tracked vehicle. The methods how to apply Bekker's soil theory for multibody track system are proposed in this investigation and demonstrated numerically by high mobility tracked vehicle.

• Journal of agricultural medicine and community health
• /
• v.20 no.2
• /
• pp.187-195
• /
• 1995

Hwamunsok(mat with flower design) is a special product of Kanghwa, which is made up of cyperus exaltatus. According to Allergy, cyperus exaltatus is one of the inhalant allergens and provokes respiratory symptoms and signs. There have been few reports about respiratory allergic disease or contact dermatitis occurring in farmers who cultivate the cyperus exaltatus or manufacture Hwamunsok with it. We studied the relationship between allergic symptoms and exposure to cyperus exaltatus. First, we questioned 141 voluntaries living in Kangwha on the symptoms of contact dermatitis, allergic rhinitis and bronchial asthma. Secondly, open tests with cyperus exaltatus were done to permitted 73 voluntaries. Patch tests with the European standard series(23 antigens) were only done to exposure 49 subjects to cyperus exaltatus. The results were as follows : 1. As the manifestation rate of allergic symptoms by age, its of 60 years old over in male showed 333 per 1,000 persons. Its of 50 years old in female showed 412 per 1,000 persons. Those age groups in both genders exhibited the highest manifestation of allergic symptoms than all other age groups. Also, if age and sex were adjusted with the rural population of Kanghwagun('93 base population), the manifestation rate of allergic symptoms in male showed 283 per 1,000 persons. Its in female and totals of study populations showed which is each 206 and 234 per 1,000 persons. Specially, it showed that statistics significantly(p=0.002), exposured subjects by cultivation of cyperus exaltatus & manufacture of Hwamunsok have experienced symptoms of contact dermatitis more frequently than unexposured subjects. Secondly, it tested statistics significantly that the risk factor as manifestation of allergic symptoms was the exposure of cyperus exaltatus's allergen(p=0.024). The manifestation risk of allergic symptoms in exposure groups was 3.73 times higher than unexposured subjects. Thirdly, positive reactions in open tests with cyperus exaltatus were higher in exposured subjects than non-exposured subjects. After 72 and 96 hours, positive reactions in open tests were all 10 subjects(20.4%). Also, after 1 week, positive reactions were 8 subjects(16.4%). In conclusion there is a close relationship between contact dermatitis and exposure to cyperus exaltatus while cultivating it and manufacturing Hwamunsok. Therefore, various studies should be continued and a health education program undertaken on contact dermatitis with those who were be engaging in Hwamunsok's manufacture.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.2
• /
• pp.283-289
• /
• 2012

Cam rack pinion (CRP) system which consists of cam rack and roller pinion transforms the rotation motion into linear one. The roller pinion has the plurality of rollers and meshes with its conjugated cam rack. The exact tooth profile of the cam rack and the non-undercut condition to satisfy the required performance have been proposed by introducing the profile shift coefficient. The load stress factors are investigated by varying the shape design parameters to predict the gear surface fatigue limit which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• International Journal of Automotive Technology
• /
• v.1 no.1
• /
• pp.26-34
• /
• 2000

The new numerical procedure for hydroplaning has been developed by considering the following three important factors; fluid/structure interaction, tire rolling, and practical tread pattern. The tire was analyzed by FEM with Lagrangian formulation and the fluid is analyzed by FVM with Eulerian formulation. Since the tire and the fluid are modeled separately and their coupling is automatically computed by the coupling element, the fluid/structure interaction of the complex geometry such as the tire with the tread pattern can be analyzed practically. We verified the predictability of the hydroplaning simulation in the different parameters such as the water flow, the velocity dependence of hydroplaning, and the effect of the tread pattern on hydroplaning. In order to predict the streamline in the contact patch, the procedure of the global-local analysis was developed. Since the streamline could be predicted by this technology, we could develop the new pattern in a short period based on the principle; "make the stream line smooth".