• 한국자동차공학회논문집
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• 제18권3호
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• pp.37-42
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• 2010

Plastic region tightening is widely used in critical bolted joints in internal combustion engines in order to reduce the engine weight by maximizing the use of load-carrying capacity of bolt. Mechanical behavior of bolt tightened in plastic region under external axial tensile load is investigated for various friction conditions using three dimensional finite element analysis. The behavior of bolt tightened in elastic region as well as that in tensile test are investigated for comparison. Tightening process is simulated by rotating the bolt in order to examine the friction effect realistically. It is revealed that the bolt tightened in plastic region can carry more external load until the joint is opened, and yields at lower bolt load than the bolt tightened in elastic region. The friction coefficient has effect on the yield load, but not on the load-carrying capacity. Moreover, the scatter in the bolt preload due to friction begins with plastic deformation of bolt in the angle tightening control, whereas it begins with the onset of tightening in the torque tightening control. The observations are interpreted with the residual torsional stress in the bolt generated during the tightening.

• Steel and Composite Structures
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• 제25권6호
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• pp.727-734
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• 2017

This paper describes a quasi-static finite element analysis, which uses the explicit integration method, of the apex joint of a cold-formed steel portal frame. Such cold-formed steel joints are semi-rigid as a result of bolt-hole elongation. Furthermore, the channel-sections that are being connected have a reduced moment capacity as a result of a bimoment. In the finite element model described, the bolt-holes and bolt shanks are all physically modelled, with contact defined between them. The force-displacement curves obtained from the quasi-static analysis are shown to be similar to those of the experimental test results, both in terms of stiffness as well as failure load. It is demonstrated that quasi-static finite element analysis can be used to predict the behavior of cold-formed steel portal frame joints and overcome convergence issues experienced in static finite element analysis.

• Composites Research
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• 제22권5호
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• pp.30-36
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• 2009

복합재 부품의 전형적인 조인트 형태를 평가하기 위해서, 2열 볼트 체결 탄소섬유강화 복합재의 파손강도와 파손 모드에 대하여 연구를 수행하였다. 연구는 상온과 고온다습 조건에서 적층과 형상을 변수로 실험적으로 수행되었다. 실험결과를 바탕으로 다음과 같은 결론을 얻었다. 하중-변위 선도는 두 가지 형태로 관찰되었으며, 각 파손 모드는 하중-변위 선도로 특징지어진다. 고온다습 조건의 파손형태는 베어링 파손 모드이며, 베어링 파손 모드에서 파손 강도는 유효강성의 영향이 크지 않다고 분석된다. 고온다습 조건의 파손강도 감소는 침투한 수분에 의해 섬유와 모재의 층간 결합부의 물성 저하에 기인한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.559-560
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• 2009

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2008년도 국제학술회의
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• pp.53-61
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• 2008

• 한국정밀공학회지
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• 제11권2호
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• pp.189-196
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• 1994

Quality assurance in the process of manufacturing high strengh bolt sets used in the frictional joints of structures in one of important concern to users as well as to manufactures. In case of occurrences of either defective or low-quality products, even if they are quite rare, some systematic means of localizing the cause-characteristics and matching to corresponding production process is necessary. Control chart of torque factor is the primary indicatir in finding defectiveness of the products. Use of correlation diagrams ofnhardness of the bolt set presents in part a way of screening the cause. Retest data of the bolt set provide additional ideas of localizing the cause, for which theoretical background is presented in this regard. A process-characteristics matrix relating the causes of low quality to the corresponding process of manufacturing, which is of prime importance for the feedback control of production, is also proposed. Finally general features of control to assure quality of the set is described.

• Structural Engineering and Mechanics
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• 제56권3호
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• pp.355-367
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• 2015

This paper deals with a new designed joint system for single-layer spatial structures. As the stability of these structures is greatly influenced by the joint behaviour, the aim of this paper is the characterization of the joint response in bending through Finite Element Method (FEM) analysis using ABAQUS. The behaviour of the joints studied here was influenced by many geometrical factors, such as bolts and plate sizes, distance between bolts and end-plate thickness. The study comprised five models of joints with different values of those parameters. The numerical results were compared to the results of previous experimental tests and the agreement was good enough. The differences between the numerical and experimental initial stiffness are attributed to the simplifications introduced when modelling the bolt threads as well as the presence of residual stresses in the test specimens.

• Smart Structures and Systems
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• 제17권1호
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• pp.135-147
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• 2016

This paper describes a smart structural system, which uses smart materials for real-time monitoring and active control of bolted-joints in steel structures. The goal of this research is to reduce the possibility of failure and the cost of maintenance of steel structures such as bridges, electricity pylons, steel lattice towers and so on. The concept of the smart structural system combines impedance based health monitoring techniques with a shape memory alloy (SMA) washer to restore the tension of the loosened bolt. The impedance-based structural health monitoring (SHM) techniques were used to detect loosened bolts in bolted-joints. By comparing electrical impedance signatures measured from a potentially damage structure with baseline data obtained from the pristine structure, the bolt loosening damage could be detected. An outlier analysis, using generalized extreme value (GEV) distribution, providing optimal decision boundaries, has been carried out for more systematic damage detection. Once the loosening damage was detected in the bolted joint, the external heater, which was bonded to the SMA washer, actuated the washer. Then, the heated SMA washer expanded axially and adjusted the bolt tension to restore the lost torque. Additionally, temperature variation due to the heater was compensated by applying the effective frequency shift (EFS) algorithm to improve the performance of the diagnostic results. An experimental study was conducted by integrating the piezoelectric material based structural health monitoring and the SMA-based active control function on a bolted joint, after which the performance of the smart 'self-monitoring and self-healing bolted joint system' was demonstrated.

• Steel and Composite Structures
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• 제20권2호
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• pp.267-293
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• 2016

It is well known that, in order to accurately predict the behaviour of steel structures a requirement the definition of the mechanical behaviour of beam-to column joints is of primary importance. This goal can be achieved by means of the so-called component method, which, in order to obtain the whole behaviour of connections, provides to break up joints in basic components of deformability and resistance. One of the main joint components used to model bolted connections is the so-called equivalent T-stub in tension, which is normally used to predict the behaviour of bolted plates in bending starting from the behaviour of the single bolt rows. In past decades, significant research efforts have been devoted to the prediction of the behaviour of bolted T-stubs but, to date, no particular attention has been devoted to the characterization of their plastic deformation capacity. To this scope, the work presented in this paper, taking into account the existing technical literature, proposes a new theoretical model for predicting the whole behaviour up to failure of bolted T-stubs under monotonic loading conditions, including some complexities, such as the bolt/plate compatibility requirement and the bolt fracture, which are necessary to accurately evaluate the ultimate displacement. After presenting the advances of the proposed approach, a comparison between theoretical and experimental results is provided in order to verify its accuracy.

• 한국강구조학회 논문집
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• 제20권2호
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• pp.279-288
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• 2008

본 논문에서는 압축력을 받는 고장력 볼트 마찰이음부의 미끄러짐 거동을 3차원 유한요소 해석 및 실험을 통하여 규명하였다. 모재의 두께가 고장력 불트이음부에 끼치는 영향을 미끄러짐 하중, 볼트의 변형 및 파괴하중과의 관계와 함께 파악하였다. 초기 미끄러짐 하중 이후의 볼트의 강성을 고려한 이음부의 거동 모델을 제시하고 유한요소해석 및 실험을 통하여 비교, 분석하였다. 범용 유한요소해석 프로그램인 ABAQUS에서 지원되는 고체요소를 사용하여 해석모델을 작성하였고 모재 사이의 마찰 및 미끄러짐이 발생한 이후 볼트와 모재 사이의 마찰 등을 고려하였다. 기존의 문헌에 제시된 여러 가지 강재의 응력-변형도 관계를 적용하였으며 미끄러짐 변위와 볼트 주변의 축응력들을 비교하였다. 모재의 두께가 볼트의 직경보다 작은 경우에는 압축력에 의한 휨좌굴에 시험체에 발생하였고 모재의 두께가 볼트 직경보다 두꺼운 경우에는 볼트의 전단파괴가 이음부의 극한강도를 나타냄을 파악하였다.