• 한국정밀공학회지
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• 제20권1호
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• pp.172-178
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• 2003

Two types of bolted lap joints, one with a viscoelastic layer and the other without the viscoelastic layer were chosen to analyze the dynamic characteristics of the joints with the mechanical properties of the bolts in the joints are considered as computational variables. The finite element method was used along with the modal testing to verify the PEM model. The results in the bolted lap joints reveal that the higher the Young's modulus for the bolts we use the higher the natural frequencies we obtain fur the joints. However, the natural frequency differences in the first and second mode are not substantial but become noticeable in the higher modes. Lower natural frequencies were obtained for the bolted lap joints with the viscoelastic layer when compared with those of the bolted lap joints without the viscoelastic layer. And the differences in the natural frequencies for the two types of joints are relatively small in the first and second mode whereas in the higher mode the differences become significant. The loss factors were observed to be significant especially in the second mode for the bolted lap joints with the viscoelastic layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.624-629
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• 2001

Two types of bolted lap joints, one with a viscoelastic layer and the other without the viscoelastic layer were chosen to analyze the dynamic characteristics of the joints with the mechanical properties of the bolts of the joints being taken as computational variables. The finite element method was used along with the impact hammer technique to verify the FEM model. The results in the bolted lap joints reveal that the higher the Young's Modulus for the bolts are the higher the natural frequencies results for the joints. However, the natural frequency differences in the first and second mode are not substantial but become noticeable in the higher modes. Lower natural frequencies were obtained for the bolted lap joints with the viscoelastic layer when compared with those of the bolted lap joints without the viscoelastic layer. And the differences in the natural frequencies for the two types of joints are relatively small in the first and second mode whereas in the higher mode the differences become significant. The loss factors were observed to be significant especially in the second mode for the bolted lap joints with the viscoelastic layer.

• Structural Monitoring and Maintenance
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• 제9권3호
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• pp.237-258
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• 2022

This paper studies detecting and locating loose bolts using nonlinear guided waves. The 3D Finite Element (FE) simulation is used for the prediction of guided waves' interactions with loose bolted joints. The numerical results are verified by experimentally obtained data. The study considers bolted joints consisting of two bolts. It is shown that the guided waves' interaction with surfaces of a loose bolted joint generates Contact Acoustic Nonlinearity (CAN). The study uses CAN for detecting and locating loose bolts. The processed experimentally obtained data show that the CAN is able to successfully detect and locate loose bolted joints. A 3D FE simulation scheme is developed and validated by experimentally obtained data. It is shown that FE can predict the propagation of guided waves in loose bolts and is also able to detect and locate them. Several numerical case studies with various bolt sizes are created and studied using the validated 3D FE simulation approach. It is shown that the FE simulation modeling approach and the signal processing scheme used in the current study are able to detect and locate the loose bolts in imperfect bolted joints. The outcomes of this research can provide better insights into understanding the interaction of guided waves with loose bolts. The results can also enhance the maintenance and repair of imperfect joints using the nonlinear guided waves technique.

• 한국안전학회지
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• 제18권2호
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• pp.1-5
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• 2003

By using an approach developed to determine the torque-tension relationship for bolted joints, frictional properties of several typical bolted joints were studied experimentally. The specific property by bolted joints certify that the most significant influence of materials and bearing surface condition. Experiments on thread friction shows that prevailing torque nuts with distorted threads provide benefit for preventing self-loosening of the nut. Repeated tightening-loosening generally increases frictions in a bolted joint. It was noted that the data scatter of the experimental results of frictions in a belted joint may overshadow the influence of size. speed, and contact positions. The results from the experimental investigation will help to better design bolted joints.

• Steel and Composite Structures
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• 제21권1호
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• pp.137-156
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• 2016

Due to excellent advantages such as better illuminative effects, considerable material savings and ease and rapidness of construction, the bolted ball-cylinder joint which is a new type joint system has been proposed in space truss structures. In order to reveal more information and understanding on the behaviour of bolted ball-cylinder joints, full-scale experiments on eight bolted ball-cylinder joint specimens were conducted. Five joint specimens were subjected to axial compressive force, while another three joint specimens were subjected to axial tensile force. The parameters investigated herein were the outside diameter of hollow cylinders, the height of hollow cylinders, the thickness of hollow cylinders, ribbed stiffener and axial force. These joint specimens were collapsed by excessive deformation of hollow cylinders, punching damage of hollow cylinders, evulsion of bolts, and weld cracking. The strain distributions on the hollow cylinder opening were mainly controlled by bending moments. To improve the ultimate bearing capacity and axial stiffness of bolted ball-cylinder joints, two effective measures were developed: (1) the thickness of the hollow cylinder needed to be thicker; (2) the ribbed stiffener should be adopted. In addition, the axial stiffness of bolted ball-cylinder joints exhibited significant non-linear characteristics.

• Steel and Composite Structures
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• 제20권6호
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• pp.1323-1343
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• 2016

This paper presents the results of an extensive numerical analysis program devoted to the investigation of the mechanical behaviour of bolted ball-cylinder joints. The analysis program is developed by means of finite element (FE) models implemented in the non-linear code ABAQUS. The FE models have been accurately calibrated on the basis of available experimental results. It is indicated that the FE models could be used effectively to describe the mechanical performance of bolted ball-cylinder joints, including failure modes, stress distributions and load-displacement curves. Therefore, the proposed FE models could be regarded as an efficient and accurate tool to investigate the mechanical behavior of bolted ball-cylinder joints. In addition, to develop a further investigation, parametric studies were performed, varying the dimensions of hollow cylinders, rectangular tubes, convex washers and ribbed stiffener. It is found that the dimensions of hollow cylinders, rectangular tubes and ribbed stiffener influenced the mechanical behaviour of bolted ball-cylinder joints significantly. On the contrary, the effects of the dimensions of convex washers were negligible.

• 대한기계학회논문집A
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• 제38권7호
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• pp.765-770
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• 2014

본 논문에서는 복합재 대차프레임 볼트 체결부의 내구성 향상 방안에 대한 연구를 다루고 있다. 이를 위해, 인서트와 나사산 유무에 따른 3가지 경우를 고려하여 볼트 체결부에 대한 시험 및 해석을 통해 인서트 형태 및 유무에 미치는 영향을 평가하였다. 제안된 볼트 체결부의 구조 성능은 ASTM D5961에 의거한 시험을 통해 비교 평가하였다. 시험결과, 나사산이 없는 인서트를 갖는 볼트 체결부가 가장 적합한 것으로 확인되었다. 또한, 볼트 체결부를 고려한 복합재 대차프레임에 대한 구조 안전성 평가를 JIS E 4207에 의거하여 유한요소해석을 통해 평가하였다. 복합재 구조물은 Tsai-Wu 파손기준식에 의해 파손평가를 적용하였고, 볼트 체결부와 같은 금속재 구조물은 Von-Mises 파손기준식에 의해 평가하였다. 이때, 볼트 체결부의 경우에는 상세한 구조해석 결과 검토를 위해 서브모델링 기법을 적용하였다. 구조해석결과, 나사산이 없는 인서트가 적용된 볼트 체결부의 경우에는 볼트 체결부 주위의 복합재 구조물에 발생하는 Tsai-Wu 파손지수가 다른 경우에 비해 약 50% 감소하는 경향을 보였는데, 이는 나사선이 없는 인서트 형상이 복합재 대차프레임 볼트 체결부의 내구성을 향상시킬 수 있을 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.557-568
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• 2019

Accurate modeling of contact interface in bolted joints is crucial in predicting the dynamic behavior for bolted assemblies under external load. This paper presents a contact pressure distribution based non-uniform virtual material method to describe the joint interface of assembly structure, which is connected by sparsely distributed multi-bolts. Firstly, the contact pressure distribution of bolted joints is obtained by the nonlinear static analysis in the finite element software ANSYS. The contact surface around bolt hole is divided into several sub-layers, and contact pressure in each sub-layer is thought to be evenly. Then, considering multi-asperity contact at the micro perspective, the relationship between contact pressure and interfacial virtual material parameters for each sub-layer is established by using the fractal contact theory. Finally, an experimental platform for the dynamic characteristics testing of a beam lap structure with double-bolted joint is constructed to validate the efficiency of proposed method. It is found that the theoretical results are in good agreement with experimental results by impact response in both time- and frequency-domain, and the relative errors of the first four natural frequencies are less than 1%. Furthermore, the presented model is used to examine the effect of rough contact surface on dynamic characteristics of bolted joint.

• 대한기계학회논문집A
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• 제41권10호
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• pp.983-989
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• 2017

본 논문에서는 첨단복합재의 볼트단일접합 베어링강도에 대한 시험적 평가 결과를 수록하였다. 볼트단일접합 시험은 stabilized 접합과 unstabilized 접합에 대하여 수행하였다. Stabilized 접합은 접합부 면외회전을 제한하는 접합이다. Unstabilized 접합은 면외변위를 제한하지 않는 접합이다. 볼트 단일접합에서 적층판의 베어링강도 값은 적층판 내 적층각 $0^{\circ}$, $+45^{\circ}$, $-45^{\circ}$ 및 $90^{\circ}$ 비율에 영향이 없음을 보여준다. 볼트접합부 면외거동의 영향으로 unstabilized 볼트 단일접합 베어링 강도값이 stabilized 볼트 단일접합 베어링 강도값 보다 작음을 보여주고 있다. 본 논문에 사용된 복합재료는 $177^{\circ}C(350^{\circ}F)$에서 경화되는 Carbon/Epoxy UD Tape 프리프레그이다. 표준각 $0^{\circ}$, $+45^{\circ}$, $-45^{\circ}$ 및 $90^{\circ}$ 층으로 적층된 8종류의 적층판에서 총 112개 볼트단일접합 시험시편을 구성하였다. Stabilized 접합과 unstabilized 접합의 시험방법은 ASTM-D-5961M 규정을 사용하였다.

• Steel and Composite Structures
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• 제31권3호
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• pp.303-317
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• 2019

This paper presents a finite element model for predicting the behaviour of high-strength steel bolted beam-to-column joints under monotonic loading. The developed numerical model considers the effects of material nonlinearities and geometric nonlinearities. The accuracy of the developed model is examined by comparing the predicted results with independent experimental results. It is demonstrated that the proposed model accurately predicts the ultimate flexural resistances and moment-rotation curves for high-strength steel bolted beam-to-column joints. Mechanical performance of three joint configurations with various design details is examined. A parametric study is carried out to investigate the effects of key design parameters on the behaviour of bolted beam-to-column joints with double-extended endplates. The plastic flexural capacities of the beam-to-column joints from the experimental programme and numerical analysis are compared with the current codes of practice. It is found that the initial stiffness and plastic flexural resistance of the high-strength steel beam-to-column joints are overestimated. Proper modifications need to be conducted to ensure the current analytical method can be safely used for the bolted beam-to-column joints with high-performance materials.