• The Journal of Advanced Prosthodontics
• /
• 제13권1호
• /
• pp.36-45
• /
• 2021

Purpose. To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Materials and Methods. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3rd of buccolingual width of an unprepared tooth) or narrow (1/3rd of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used. Results. The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs (P<.001). Conclusion. The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

• 한국자동차공학회논문집
• /
• 제22권6호
• /
• pp.104-112
• /
• 2014

Generally, numerical approaches of evaluation for vehicle seat comfort have been studied without considering time-dependent characteristics and the only seating moment have been considered in seat design. However, the comfort not only at the seating moment but also in the long-term should be evaluated because the passengers are sitting repeatedly on the seat to drive the vehicle for hours. So, the aim of this paper is to carry out a quantitative evaluation of the time-dependent mechanical characteristics of seat foams and to suggest a process for predicting the viscoelastic deformation of seat foam in response to long-term driving. To characterize the seat materials, uniaxial compression and tension tests were carried out for the seat foam and stress relaxation tests were performed for evaluating the viscoelastic behavior of the seat foam. A unit solid element model was used to verify the reliability of the material model with respect to the compression behavior of the seat foam. It is not straightforward to evaluate the time-dependent compression of foams using the explicit solver because the viscoelastic material model is limited. To use the explicit solver, the material model must be modified using stress-degradation data. Normalized stress relaxation moduli were added to the stress-strain curves obtained under static conditions to achieve a time-dependent set of stress-strain relations that were compatible with the implicit solver. There was good agreement between the analysis results and experimental data.

• 한국의류학회지
• /
• 제41권3호
• /
• pp.446-457
• /
• 2017

This study surveys the usage and satisfaction of car seat covers, analyzes the satisfaction and luxuriousness of materials used and provides basic data on optimum car seat covers that improve consumer satisfaction, stability, and comfort, while driving. The survey was conducted on 150 people in their 20s to 60s with a car. Consequently, achromatic colored car seat covers were used most and the satisfaction with black was very high. Interior & exterior harmony and the pursued car image were considered important, this consumer psychology impacted the color selection for car seat covers. The satisfaction reasons were different according to materials. Genuine leather was highly regarded in interior & exterior harmony (20.8%), excellent seat sensation (17.7%), excellent tactile sensation (11.5%), and luxuriousness (8.5%). For artificial leather, interior & exterior harmony (16.5%) and easiness of stain removal (13.6%) was rated high and fabric had excellent seat sensation (12.3%) and economics (10.8%). The material, heated and ventilated device affected car seat cover satisfaction. The luxurious image of car seat covers was pursed and was perceived mainly with a sense of sight. Luxury car seat covers were mainly created with materials. Genuine leather and black car seat covers increased luxuriousness. For car seat covers, those with flexibility, excellent compressive elasticity, and thickness were perceived as luxurious.

• 한국철도학회논문집
• /
• 제9권5호
• /
• pp.524-531
• /
• 2006

Environmental problem is one of important global issues. Transportations are main pollutant emission sources. Although railroad is stilt an environmental-friendly transportation, its environmental impact has been increased continuously. Especially, because a large amount of environmental impact is released from vehicles and facilities, it is necessary to assess and to reduce their environmental impact. Life cycle assessment (LCA) is a representative method which can evaluate environment impact through the whole life cycle of a product or a process. In this study, the environmental impact of seat in the electric motor unit (EMU) was analyzed quantitatively with its material using lift cycle assessment (LCA). As a result, the characteristics of environmental impact were investigated differently with the material of seat. Among ten impact categories, the seat with aluminum and FRP showed the highest ozone depletion (OD). On the other hand, in the seat with stainless steel and plastic, fresh water aquatic ecotoxicity (FAET) and marine water aquatic ecotoxicity (MAET) were high relatively. Therefore, the parts of EMU must be selected considering the characteristics of environmental impact in future.

• 재활복지공학회논문지
• /
• 제8권3호
• /
• pp.205-211
• /
• 2014

본 연구는 휠체어 좌석의 재질 중 하나로 국내에서 주로 사용되는 폴리우레탄 폼의 경도에 따른 압력 분석을 통하여 압력 분산이 적절하게 이루어지는 재질을 제시하는 것에 목적이 있다. 이러한 연구의 목적을 달성하기 위해 폴리우레탄 폼의 경도 $13kg/cm^2$, $18kg/cm^2$, $25kg/cm^2$, $45kg/cm^2$로 구성된 전방웨지 6cm 시트를 총 4개를 설계 및 제작하였다. 실험에는 비장애인 10명이 참여하였으며, 측정도구로는 XSENSOR를 사용하였고 휠체어 시뮬레이션에 시트를 올려 실험하였다. 각 시트마다 착석압력 측정은 5분간 실시하였으며 획득한 데이터 중 평균압력, 최대압력, 접촉면적 분석을 통해 경도에 따른 영향을 살펴보았다. 이에 본 실험을 통해 얻은 결과는 다음과 같다. 폴리우레탄 재질의 경도에 따라 평균압력, 최대압력 및 접촉면적은 경도 $45kg/cm^2$에서 높게 나타났고, 13, $18kg/cm^2$에서 낮게 나타났다(p< .05). 이러한 결과를 통해 폴리우레탄 재질의 경도는 착석 시 압력변화에 영향이 있음을 알 수 있었으며, 향후 자세유지기구의 시트 재질로 폴리우레탄 폼을 사용한다면 경도 $18kg/cm^2$가 체압을 분산하기에 적절한 재질로 파악되었다.

• 한국생산제조학회지
• /
• 제8권5호
• /
• pp.83-89
• /
• 1999

A seat frame structure in automotive vehicles made of polymer matrix composite to achieve weight reduction at low cost was developed. In order to design and manufacture the actual product studies on material selection and structural analysis were performed. Structural analysis was performed with a finite element method. The analysis was done for several cases suggested in various safety regulations. Each results was utilized to modify the actual shape to obtain a lighter, safer and more stable design. The final design was used to produce a sample bottom plate of the seat structure with reinforced by X-shape frame. Substitution of the material resulted in a weight reduction effect with equivalent strength fatigue and impact characteristics.

• 한국자동차공학회논문집
• /
• 제17권3호
• /
• pp.35-44
• /
• 2009

The purpose of this paper is to describe experimental results about the T-joint welding of the high power continuous wave (CW) fiber laser for SAPH steel plate for seat frame of car. The seat rail is a part of seat frame of cars. The assembling method is mostly fix up using a bolt and nut. But this assembling method has many demerits in productivity such as increasing work process and material cost. This paper presents an experimental study about Laser T-Joint weldability of seat rail. Laser welding has many advantages in lightness and saving material costs of seat frame. The laser beam was moved along the work pieces by six axis robot with process optical fiber. The laser beam is focused with a welding head within incident angle $15{\sim}45^{\circ}$ for the purpose of the T-joint welding through two side full penetration. The range of the root gap size is less than ${\leq}0.4mm$. Optical microscopy SEM were performed to observe the micro structures and determine the structures of welded zone.

• 자동차안전학회지
• /
• 제11권4호
• /
• pp.57-62
• /
• 2019

The seat back frame of the vehicle is subjected to load on the passenger behavior. Because of steel material, it is necessary to optimize the frame considering lightweight and safety. In this paper, finite element analysis is used for the optimal design of the seat back frame. First, a lightweight material is applied to reduce the weight of the seat back frame. Secondly, the design position of the pipe part fastened in the seat back frame was selected by considering the strength against the load generated by the occupant. Third, the shape of the side frame was derived by performing the phase optimization analysis for the AFT load condition. And we have compared the initial model with the optimal model to verify the light weighting and safety. As a result, the optimal design model of the seat back frame satisfying the weight reduction and safety has been proposed.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.403-404
• /
• 2006

Sintered materials have been applied widely in Valve Seat Inserts (VSI). The demands for VSIs are not only good heat and wear resistance but also good machinability. The sintered materials, which are made of a mixture of manganese containing iron powder and certain types of sulfide powder, have superior machinability due to precipitation of the fine MnS particles in the matrix. This report introduces a new VSI material, which has both superior machinability, and wear resistance due to applies of this "MnS precipitation" technique.

• 한국자동차공학회논문집
• /
• 제11권6호
• /
• pp.205-212
• /
• 2003

This paper may provide a basic design data for the safer car seat mechanism and the quality of the material used by finding out the passenger's dynamic behavior when protected by seat belt during collision. A computer simulation with finite element method is used to accomplish this objective. At first, a detailed geometric model of the seat is constructed using CAD program. The formation of a finite element from a geometric data of the seat is carried out using Hyper-Mesh that is the commercial software for mesh generation and post processing. In addition to seat modeling, the finite element model of seat belt and dummy is formed using the same software. Rear impact analysis is accomplished using Pam-Crash with crash pulse. The part of the recliner and right frame is under big stress in rear crash analysis because the acceleration force is exerted on the back of the seat by dummy. The stress condition of the part of the bracket is checked as well because it is considered as an important variable on the seat design. Front impact model which including dummy and seal belt is analyzed. A Part of anchor buckle of seat frame has high stress distribution because of retraction force due to forward motion of dummy at the moment of collision. On the basis of the analysis result, remodeling and reanalysis works had been repeatedly done until a satisfactory result is obtained.