• Advanced Composite Materials
• /
• 제18권1호
• /
• pp.1-20
• /
• 2009

This paper describes the results of experiments and numerical simulation studies on the impact and indentation damage created by low-velocity impact subjected onto honeycomb sandwich panels for application to the BIMODAL tram. The test panels were subjected to low-velocity impact loading using an instrumented testing machine at six energy levels. Contact force histories as a function of time were evaluated and compared. The extent of the damage and depth of the permanent indentation was measured quantitatively using a 3-dimensional scanner. An explicit finite element analysis based on LS-DYNA3D was focused on the introduction of a material damage model and numerical simulation of low-velocity impact responses on honeycomb sandwich panels. Extensive material testing was conducted to determine the input parameters for the metallic and composite face-sheet materials and the effective equivalent damage model for the orthotropic honeycomb core material. Good agreement was obtained between numerical and experimental results; in particular, the numerical simulation was able to predict impact damage area and the depth of indentation of honeycomb sandwich composite panels created by the impact loading.

• 한국산학기술학회논문지
• /
• 제19권7호
• /
• pp.56-62
• /
• 2018

부스 바는 초고층 빌딩의 전력공급과 플랜트 산업의 전원 공급부 및 장비 제조 산업 분야의 배전반에 널리 사용되는 전기적인 접속 구조이다. 부스 바의 설계 시 고려해야 할 사항으로 사용 환경에 따른 재질, 전원 용량에 따른 단면적, 표면둘레의 길이, 체결 방법 등이 있다. 설계 시 충분한 전원 용량의 사이즈로 제작된 부스 바의 경우에도 실제 체결이 잘못 될 경우 열화에 의한 화재로 이어질 수 있다. 이러한 이유로 전기적 접촉부의 온도 상승에 대한 다양한 연구가 지속되어 왔다. 그러나 접촉부의 온도 상승은 결과에 기인한 현상이지 직접적인 원인은 아니다. 본 논문은 부스 바의 체결력과 중첩 구간에 따른 접촉 저항의 영향성에 대한 연구로 시편을 제작하여 저항의 변화를 측정하여 영향력을 분석하였다. 총 8개의 부스 바시편을 제작하여 측정하였고 각각의 시편을 교차하여 체결시 가해지는 체결력과 중첩 구간의 간격을 가변하여 저항을 측정하였다. 실험 결과를 통해 이러한 요인이 실제 접촉 저항의 변화에 어느 정도 기여하는지를 분석하여 안전한 전원 연결 장치의 모델을 제시하고자 한다.

• 한국전기전자재료학회논문지
• /
• 제25권5호
• /
• pp.353-360
• /
• 2012

As semiconductor device technology continuously shrinks, low-open area etch process prevails in front-end etch process, such as contact etch as well as one cylindrical storage (OCS) etch. To eliminate over loaded wafer processing test, it is commonly performed to emply diced small coupons at stage of initiative process development. In nominal etch condition, etch responses of whole wafer test and coupon test may be regarded to provide similar results; however, optical emission spectroscopy (OES) which is frequently utilize to monitor etch chemistry inside the chamber cannot be regarded as the same, especially etch mask is not the same material with wafer chuck. In this experiment, we compared OES data acquired from two cases of etch experiments; one with coupon etch tests mounted on photoresist coated wafer and the other with coupons only on the chuck. We observed different behaviors of OES data from the two sets of experiment, and the analytical results showed that careful investigation should be taken place in OES study, especially in coupon size etch.

• 소성∙가공
• /
• 제16권7호
• /
• pp.530-537
• /
• 2007

This paper is concerned with the analysis of plastic deformation of bimetal co-extrusion process. Two sets of material combination have been adopted for analysis, i.e. combinations of Cu/Al and Fe/Al. In the first set of material combination, the selected materials are AA 1100 aluminum alloy as hard material and CDA 110 as soft one. This type of material selection is to examine the effect of hard core and soft sleeve and vice versa on the deformation pattern in terms of plastic zone and velocity discontinuity along the contact surface between construction materials. Four different cases of co-extrusion process in terms of material combination and interference bonding were simulated to investigate the effect of material arrangement between core and sleeve, and of bonding on the plastic zones and velocity discontinuity. In the other set of material combination, model materials used as core and sleeve were AA 1100 and AISI 1010, which are relatively soft and hard, respectively. Process parameters except diameter ratio of core to sleeve material such as semi-die angle, reduction in area in global sense and die comer radius have been set constant throughout the simulation to concentrate our effort on the analysis of influence of diameter ratio on deformation behavior such as deformation zone, surface expansion, exit velocity discontinuity between composite materials, and extrusion forces.

• Tribology and Lubricants
• /
• 제24권6호
• /
• pp.285-290
• /
• 2008

The purpose of this paper is to present the case study of tribological failure analysis on the gear damages, oil leakage, and sealant sealing in a manual transmission of front engine and front wheel drive vehicle. The manual transmission is to change the speed range and direction of the engines depending on the driving conditions by friction driving forces with input and output gear system. The material property and surface roughness of the gears are strongly related to the gear noise and micro-vibration, oil leakage and wear, which may decrease the real contact area of the gear and the strength of the oil film thickness between the driving gear and driven one. The O-ring damage of speedometer driven gear and bad sealant sealing of oil pan may produce oil leakage through the contact surfaces, which cause the oil shortage and seizure on the sliding surfaces of the transaxle gears. In the failure case study, the proper repair working and good lubrication are very important for the long life of the transaxle without any tribological failures and oil leakage.

• 로봇학회논문지
• /
• 제14권2호
• /
• pp.94-103
• /
• 2019

The optimal grasping point of the object varies depending on the shape of the object, such as the weight, the material, the grasping contact with the robot hand, and the grasping force. In order to derive the optimal grasping points for each object by a three fingered robot hand, optimal point and posture have been derived based on the geometry of the object and the hand using the artificial neural network. The optimal grasping cost function has been derived by constructing the cost function based on the probability density function of the normal distribution. Considering the characteristics of the object and the robot hand, the optimum height and width have been set to grasp the object by the robot hand. The resultant force between the contact area of the robot finger and the object has been estimated from the grasping force of the robot finger and the gravitational force of the object. In addition to these, the geometrical and gravitational center points of the object have been considered in obtaining the optimum grasping position of the robot finger and the object using the artificial neural network. To show the effectiveness of the proposed algorithm, the friction cone for the stable grasping operation has been modeled through the grasping experiments.

• 대한치과보철학회지
• /
• 제42권4호
• /
• pp.425-442
• /
• 2004

Statement of problem: A difficulty in achieving a passive-fitting prosthesis can be overcome by individual crown restoation of multiple implants. But individualized crown has another difficulty in control of contact tightness and stress distribution. Purpose: This in vitro study is to evaluate the stress distribution and the magnitude in the supporting tissues around Endopore implants with different crown lengths, interproximal contact tightness, and the splinting effects. Material & methods: Three Endopore implants($4.1{\times}9mm$) were placed in the mandibular posterior edentulous area distal to the canine and photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA). Restorations were fabricated in two crown lengths: 9, 13 mm. For non-splinted restorations, individual crowns were fabricated on three custom-milled titanium abutments. After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m$), and heavy($80{\mu}m$). For splinted restorations, 3-unit fixed partial dentures were fabricated. This study was examined under simulated non-loaded and loaded conditions(6.8 kg). Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure. Results: 1. When restorations were not splinted, the more interproximal contact tightness was increased among the three implants, the more stress was shown in the cervical region of each implant. When crown length was increased, stresses tended to increase in the apex of implants but there were little differences in stress fringes. 2. When nonsplinted restorations were loaded on the first or third implant, stresses were increased in the apex and cervical region of loaded implant. Regardless of interproximal contact tightness level, stresses were not distributed among the three implants. But with tighter interproximal contact, stresses were increased in the cervical region of loaded first or third implant. 3. When the nonsplinted restorations were not loaded, there were little stresses on the supporting structure of implants, but low level stresses were shown in the splinted restorations even after sectioning and soldering. 4. With splinted restorations, there were little differences in stresses between different crown lengths. When splinted restorations were loaded, stresses were increased slightly on the loaded implant, but relatively even stress distribution occurred among the three implants. Conclusions: Splinting the crowns of adjacent implants is recommended for Endopore implants under the overloading situation.

• Structural Engineering and Mechanics
• /
• 제63권5호
• /
• pp.691-702
• /
• 2017

Clearances are essential for the assemblage of mechanisms to allow the relative motion between the joined bodies. This clearance exists due to machining tolerances, wear, material deformations, and imperfections, and it can worsen the mechanism performance when the precision and smoothly-working are intended. Energy is a subject which is less paid attention in the area of clearance. The effect of the clearance on the energy of a flexible slider-crank mechanism is investigated in this paper. A clearance exists in the joint between the slider and the coupler. The contact force model is based on the Lankarani and Nikravesh model and the friction force is calculated using the modified Coulomb's friction law. The hysteresis damping which has been included in the contact force model dissipates energy in clearance joints. The other source for the energy loss is the friction between the journal and the bearing. Initial configuration and crank angular velocity are changed to see their effects on the energy of the system. Energy diagrams are plotted for different coefficients of friction to see its influence. Finally, considering the coupler as a flexible body, the effect of flexibility on the energy of the system is investigated.

• 대한기계학회논문집A
• /
• 제22권2호
• /
• pp.476-481
• /
• 1998

It is generally known that in high speed work with more than 1000 m/min cutting speed, according to the work material phenomenon of tool wearing is increased due to the some produced neat and as a result this makes the cutting work impossible. In this study, the high speed cutting is possible because of the different cutting from the presently known fact. That is, most of generated heats influence on the quantity flowing in chip greatly. Therfore, this study aims at the behavior of cutting heat generated at high speed cutting. It makes clearly the euqntity of heat flowing in chip, work materal, tool, and inflowing ratio. The cutting mechanism varies by the changing of cutting depth, slant face and contact area through this study. And it is exammined that the influence of heat of all parts is greatly due to the change the contact length of clearance face. It is confirmed from the exp[eriment that the inflowing heat ratio influences the cutting speed greatly and the heat of clearance face can not be disregarded.

• KSTLE International Journal
• /
• 제3권1호
• /
• pp.38-42
• /
• 2002

Diamond-like Carbon(DLC) films were deposited on Si wafers by an RF-plasma-assisted CVD using CH$_4$gas. Tribological tests were conducted with the use of a rotating type ball on a disk friction tester with dry air. This study made use of four kinds of mating balls that were made with stainless steel but subjected to different annealing conditions in order to achieve different levels of hardness. In all load conditions, testing results demonstrated that the harder the mating materials, the lower the friction coefficient was. The friction coefficients were fecund to be lower with austenite mating balls than with fully annealed martensite balls. Conversely, the high friction coefficient found in soft martensite balls appeared to be caused by the larger contact area between the DLC film and the ball. The wear tracks on DLC films and mating balls could prove that effect. Measuring the wear track of both DLC films and mating balls revealed a similar tendency compared to the results of friction coefficients. The wear rate of austenite balls was also less than that of fully annealed martensite balls. Friction eoefficients decrease when applied leads exceed critical amount. The wear track on mating balls showed that a certain amount of material transfer occurs from the DLC film to the mating ball during a high friction process. Raman Spectra analysis Showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.