• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.58-68
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• 1998

Advantages of adhesively bonded joints and techniques of weight reduction have led to increasing use of structural adhesives such as LSI(large scale integration) package, automobile, aircraft in the various industries. In spite of such wide applications of adhesively bonded joints, the evaluation method of bonding strength has not been established. Stress singularity occurs at the interface edges of adhesively bonded joints and it is required to analyze it. In this paper, the stress singularity using 2-dimensional elastic boundary element method (BEM) with the changes of the lap length and adhesive for single lap joint was analyzed, and experiments of strength evaluation were carried out. As the results, the evaluating method of bonding strength considering stress singularity at interface edges of adhesively bonded joints and stress intensity factor of interface crack have been proposed in static and fatigue test.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.19-26
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• 1999

This paper deals with the stress singularity induced at the interface corner between the viscoelastic thin film and the rigid substrate as the film absorbs moisture from the ambient environment. The rime-domain boundary element method is employed to investigate the behavior of interface stresses. The order of the free-edge singularity is obtained numerically for a given viscoelastic model. It is shown that the free-edge stress intensity factor is relaxed with time,'while the order of the singularity increases with time for the viscoelastic model considered.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.437-443
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• 1999

This paper deals with the stress singularity induced at the interface corner between the viscoelastic thin film and the rigid substrate subjected to uniform temperature change. The viscoelastic film has been assumed to be thermorheologically simple. The time-domain boundary element method(BEM) has been employed to investigate the behavior of interface stresses. The order of the free-edge singularity has been obtained numerically for a given viscoelastic model. It is shown that the free-edge stress intensity factor is relaxed with time, while the order of the singularity increases with time for the viscoelastic model considered.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.15-22
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• 2008

Applications of bonded dissimilar materials such as integrated circuit(IC) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in bonded joints of dissimilar materials. In order to investigate the IC package crack propagating from the edge of die pad and resin, the fracture parameters of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method(BEM). From these results, crack propagation direction and path by thermal stress in the IC package were numerically simulated with boundary element method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.94-102
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• 2007

Applications of bonded dissimilar materials such as large scale integration (LSI) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in LSI. In order to investigate stress singularities on the bonded interface edges and delamination of die pad and resin in the IC package. In this paper, stress singularity factors(${\Gamma}_i$) and stress intensity factors($K_i$) considering thermal stress in the IC package were analyzed by using the 2-dimensional elastic boundary element method(BEM).

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.164-171
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• 2006

Application of friction welding is increasing in the manufacturing process of machine elements in many industry fields. To establish a reasonable strength evaluation method and fracture criterion, it is necessary to analyze stress singularity under the residual stress condition on friction welded interface between dissimilar materials. In this paper, a method to establish fracture criterion on interface of friction welded dissimiliar materials was investigated by using the boundary element method BEM and static tensile testing. A quantitative fracture criterion for friction welded dissimilar materials is suggested by using stress singularity factor, $\Gamma$.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.59-67
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• 2006

Recently, application of friction welded SUH35/SUH3 is increasing in the manufacturing process of automotive engine valves For securing its reliability and a reasonable strength evaluation method, it is necessary to assess stress singularity under the residual stress condition on the friction welded interface between dissimilar materials. In this paper, strength evaluation method of friction welded materials was investigated by boundary element method and static tensile testing. An advanced method of quantitative strength evaluation for SUH35/SUH3 friction welded material is to be suggested by establishing fracture criterion by using stress singularity factors.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.5
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• pp.62-73
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• 2005

The objects of this research are to establish the criteria of peel occurrence considering the shape of bond terminus and to compare the strength properties of adhesive joint of different three type such as butt joint, T-shape, and single lap Joints. The criteria of peel occurrence at the bond terminus was suggested. Peel loads of three type adhesive joint (butt Joint, T-shape specimen, single lap joint) were determined from tensile tests. Principal stress distributions of these joints were determined from finite element method analysis. Then, peel occurrence was estimated with stress singularity factor$(K_{prin})$ when the terminus shape was square, with average principal stress when the terminus shape was rounded. The conclusions are summarized as follows; (1) In the non-filleted model(e.g., butt joint, T-shape specimen), principal stress shows singularity at the bond terminus, intensity of stress(principal stress) singularity $(K_{prin})$ can use as the criteria of peel occurrence at the bond terminus. (2) In the filleted model(e.g., single lap joint), principal stress has not affected singularity at the bond terminus. Average principal stress$(K_{av})$ can use as the criteria of peel occurrence at the bond terminus.

• Computational Structural Engineering
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• v.10 no.2
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• pp.131-138
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• 1997

This paper concerns the stress singularity at the interface corner of the viscoelastic adhesive layer bonded between rigid adherends, subjected to a uniform transverse tensile strain. The characteristic equation is derived in the Laplace transformed space, following Williams, and the transformed characteristic equation is inverted analytically into real time space for the viscoelastic model considered here. The order of the singularity is obtained numerically. The time-domain boundary element method is employed to investigate the nature of stresses along the interface. Numerical results show that the order of the singularity increases with time while the free-edge stress intensity factors are relaxed with time.

• Computational Structural Engineering
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• v.10 no.1
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• pp.129-134
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• 1997

Interfacial stress singularity in a unidirectional two-dimensional laminate model consisting of an elastic fiber and a viscoelastic matrix has been investigated using the time-domain boundary element method. First, the interfacial singular stresses between the fiber and the matrix of a unidirectional laminate subjected to a uniform transverse tensile strain have been investigated near the free surface, but without any defect or any edge crack. Such a stress singularity might lead to fiber-matrix debonding or interfacial edge cracks. Then, the overall stress intensity factor for the case of a small interfacial edge crack of length a has been computed.