In this paper the properties of the eigenfunction expansion form in th
e interface crack problem of plane elasticity are discussed in detail.
After using the Betti's reciprocal theorem to the cracked dissimilar
bonded body, several path-independent integrals are obtained. All the
coefficients in the eigenfunction expansion form, including the K-1 an
d K-2 values, and the J-integral can be related to corresponding path
independent integrals. Possibility for formulating the weight function
is also suggested.