The crack initiation equals to fracture for bonded joint with brittle adhesive. The criterion is formulated in terms of the quasi-stress intensity factor Kp, for the maximum principle stress, that is analogous to the stress intensity factor used to characterize the stress field in the vicinity of bond terminus. Kp is evaluated using a boundary element analysis. The crack initiation at the terminus of adhesive bonded joints is estimated with the critical quasi-stress intensity factor Kp. This method presented here hardly pays attention to the crack propagation. Since there is a large influence of crack propagation on the strength of adhesive joints and structures, crack propagation must be taken into account on strength prediction of bonded joints. The quasi-stress intensity factor Kp for the maximum principle stress can use as the criteria of the crack initiation at the terminus of adhesive bonded joints having various shapes.

The objectives of the present study are to show how to predict the crack initiation at the terminus of adhesive bonded joints to calculate the crack growth in the adhesive layer using the total strain energy release rate. The crack propagation for ductile adhesives is theoretically estimated using -curve. -curve is determined from static shearing tests of single lap joints. The total strain energy release rate for single lap joints is evaluated using a boundary element analysis. The strength prediction is conducted by means of the R-curve and the total strain energy release rate.The conclusions are summarized as follows; (1) A crack propagation geometry of the bonded structure using ductile adhesive was predicted from the distribution of the total strain energy release rate. (2) The final failure load for lap joints is predicted by the R-curve method based on the fracture mechanics. (3) The final failure load for stiffened plates with a steel L-beam is predicted by the R-curve method based on the fracture mechanics.

접착제와 피착재의 물성치는 고정된 값을 가지기보다 항상 어느 정도의 불확실성을 내포하고 있으며, 이는 결합부의 성능에 영향을 미치게 된다. 본 논문에서는 컨벤스 모델링을 이용하여 불확실한 물성치를 갖는 단일 겹치기 이음의 응력해석을 수행하였다. 불확실성을 고려한 수치해석 결과, 결합부에 작용하는 전단 및 수직 응력은 증가하였으며 이는 결합부의 강도 해석에 불확실성이 반드시 고려되어야 함을 보여준다. 또한 컨벡스 모델링의 신뢰성과 효율성을 입증하기 위해 몬테카를로 기법에 의한 응력 해석 결과와 비교하였으며, 두 방법에 의한 결과는 잘 일치함을 알 수 있었다.