• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.15-28
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• 2016

Although the aircraft industry was the first to use fibre composites, now they are increasingly used in a range of structural applications such as flooring, decking, platforms and roofs. Interlayer delamination is a major failure mode which threatens the reliability of composite structures. Delamination can grow in size under increasing loads with time and hence leads to severe loss of structural integrity and stiffness reduction. Delamination reduces the natural frequency and as a consequence may result in resonance. Hence, the study of the effects of delamination on the free vibration behaviour of multilayer composite structures is imperative. The focus of this paper is to develop a 3D FE model and investigate the free vibration behaviour of fibre composite multilayer sandwich panels with interlayer delaminations. A series of parametric studies are conducted to assess the influence of various parameters of concern, using a commercially available finite element package. Additionally, selected points in the delaminated region are connected appropriately to simulate bolting as a remedial measure to fasten the delamination region in the aim of reducing the effects of delamination. First order shear deformation theory based plate elements have been used to model each sandwich layer. The findings suggest that the delamination size and the end fixity of the plate are the most important factors responsible for stiffness reduction due to delamination damage in composite laminates. It is also revealed that bolting the delaminated region can significantly reduce the natural frequency variation due to delamination thereby improving the dynamic performance.

• 한국초지조사료학회지
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• 제39권2호
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• pp.75-80
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• 2019

Oilseed rape is known to crop having low nitrogen use efficiency (NUE) but requires high levels of N fertilizer. NUE is associated with N remobilization from source to sink organ, consequently affects seed yield. Remobilization of leaf N is also related to transport of C/N metabolites in phloem. However, interaction between seed yield and phloem transport was not fully documented. In response to seed yield, N and C metabolites and their transport into seed from bolting to pod filling stage investigated in two contrasting genotypes (Capitol and Pollen) cultivated under ample (HN) or limiting nitrate (LN) supply. Seed yield was significantly reduced in N limitation and its reduction rate was much lower in Capitol than in Pollen compared to HN treated plants. Amino acid and protein content was higher in Capitol than in Pollen at bolting stage. They gradually decreased during plant development but not significant between two cultivars and/or two treatments. Glucose, fructose and sucrose content were 1.8-,1.6- or 1.25-fold higher in LN condition than in HN condition, respectively. Amino acid and sucrose content in phloem were largely higher in Capitol than in Pollen under LN condition. These results indicate that the higher seed yield might be related to greater transport ability of amino acid and sucrose in phloem under LN condition.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.93-101
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• 2003

Steel frame-type retaining walls(SFRW) are constructed by on site bolting of prefabricated steel frames and internal filling of materials such as rocks with the size of 150-300mm. Easy & fast construction, superior drainage performance and structural performance to rigorous site conditions are some of the merits of applying the SFRW to various construction sites. After the development of the structural details, a test construction of SFRW, with the height of 6m and 30m in length, was carried out at an apartment site. After completion, several months of monitoring was carried out on the structure to check displacement, tilting, settlement, soil pressures and drainage characteristics. The results of the structural behavior of SFRW along with its construction methods are presented in the paper.

• 비파괴검사학회지
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• 제9권1호
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• pp.106-110
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• 1989

Bolting degradation problems in primary coolant pressure boundary applications have become a major concern in the nuclear industry. In the bolts concerned, the failure mechanism was either corrosion wastage(loss of bolt diameter) or stress-corrosion cracking.(3) Here the manual ultrasonic testing of RPV(Reactor Pressure Vessel) and RCP(Reactor Coolant Pump) stud has been performed. But it is difficult to detect indications because examiner can not exactly control the rotation angle and can not distinguish the indication from signals of bolt. In many cases, the critical sizes of damage depth are very small(1-2 mm order). At critical size, the crack tends to propagatecompletly through the bolt under stress, Resulting in total fracture.(3) Automatic stud scanner for studs(bolts) was developed because the precise measurement of bolt diameter is required in this circumstance. By use of this scanner, the rotation angle of probe was exactly controlled and the exposure time of radiations was reduced.

• 대한산업공학회지
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• 제20권4호
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• pp.153-180
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• 1994

The assemblability is determined by the structure of product and the relationship between composing parts and machining parts. In this paper, the bolt was divided into bolt-head, -shaft, -thread and -end. For higher assemblability in bolting process, it was analyzed the geometric and technological characteristics of bolts were analysed regarding pre- and in-assembly process. And this paper presents the knowledge-based expert system to assist for designer in the processor of designing bolt for easier assembly. The developed expert system for supporting bolt design assemblability which is named as BDFA SYSTEM consists of two system such as "BOLT DESIGN SYSTEM" which provide feasible assembly bolt design to designer and "EVALUATION SYSTEM" which provide assembly evaluation to alternative of bolt design.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.448-451
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• 2005

An aspheric mirror, which requires less than $\lambda/2\;(\lambda=632.8nm)$ of form error for the $\phi$ 200mm reference curved surface, has been manufactured with an ultra-precision turning machine. We have known through several tests that the deformation patterns of the reflecting surface is related with bolting positions. In this paper the effect of main factors on deformation of a reflector is studied with a FE code. The considered factors are angular velocity, natural frequencies for a mirror, temperature increment during machining. The obtained test results are similar to the deformation shape due to the assumed temperature increment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 학술대회 논문집 정보 및 제어부문
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• pp.343-344
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• 2008

본 논문에서는 고층건물의 철골 구조물의 자동화된 볼트 체결을 위해 볼팅로봇에 장착된 카메라에 의한 영상정보를 처리하여 볼트 구멍을 인식하고 제어시스템에게 볼트 구멍의 위치를 알려주는 시스템을 제안한다. 볼팅로봇 전면에 설치된 광각 카메라를 이용하여 목표물까지 이동하고 로봇의 팔에 장착된 소형 카메라로 볼트 구멍을 인식하는 알고리즘을 제안하고 실제 볼팅로봇에 적용하여 그 성능을 평가하였으며 이는 볼팅로봇의 성능향상에 기여할 것이다.

• 한국안전학회지
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• 제13권2호
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• pp.13-21
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• 1998

This is a study on the natural vibration characteristics of Vehicle frame. Nowadays, many trucks freight the over-load, do the car designers consider the over-load about 200% in the design. It's necessary to make the model of a vehicle and simulate it for the test of driving condition, durability and vibration behavior before the vehicle is manufactured. If it is possible to make a simulation using the static and dynamic analysis, this is very useful in accomplishing an optimal design of the vehicle. In this paper, we studied the vibration characteristics of a truck body frame. The automobile body frame model for experiment is made smaller than real size frame with the ratio of 1/10. The vibration characteristics of a frame is considered as one of main factors in analyzing and improving the problem for ride comfort, noise and vibration reduction. Therefore, we experimented two method to neglect the nonlinearity. First is bolting and second is welding at the joint section. We compared computer simulation results and experimental data.

• 한국초지조사료학회지
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• 제16권3호
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• pp.215-218
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• 1996

This study examines the possibility of early production of forage rape (cv. Akela and Velox) in the period of wintering. Bolting date was Feb. 2 to Feb. 9 in PE film house culture by non-heating and Mar. 3 to Mar. 12 in open field culture. And flowering date was Feb. 24 to Mar. 3 in PE film house culture by non-heating, so it was 30~50 days faster than the open field culture of Apr. 17 to Apr. 22. Fresh matter yield was 8, 356~4, 887 kg/10a in PE film house culture by non-heating, so it was 1, 431~1, 603 kg/10a yield increase than in the open field culture of 7, 253~7, 456 kg/10a Dry matter yield was 953~963 kg/10a in PE film house culture by non-heating, so it was 71~284 kg/10a yield increase than in the open field culture of 669~892 kg/10a.

• Computers and Concrete
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• 제8권5호
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• pp.541-561
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• 2011

The Finite Element Method (FEM) was employed to demonstrate that accurate simulations of seismically repaired and retrofitted reinforced concrete shear walls can be achieved provided a good analysis program with comprehensive models for material and structural behaviour is used. Furthermore, the analysis tool should have the capability to retain residual damage experienced by the original structure and carry it forward in the repaired and retrofitted structure. The focus herein is to provide quick, simple, but reliable modelling procedures for repair and retrofitting strategies such as concrete replacement, addition of diagonal reinforcing bars, bolting of external steel plates, and bonding of external steel plates and fibre reinforced polymer sheets, thus illustrating versatility in the modelling. Slender, squat, and slender-squat shear walls were investigated. The modelling utilized simple rectangular membrane elements for the concrete, truss bar elements for the steel and FRP retrofitting materials, and bond-link elements for the bonding interface between steel or FRP to concrete. The analyses satisfactorily simulated seismic behaviour, including lateral load capacity, displacement capacity, energy dissipation, hysteretic response, and failure mode.