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異材界面2

NIMS前景
異材界面の研究については学生時代から取り組んできました。

異材界面における熱応力場

  
Thermal Stress Field at the Interface Edge in Dissimilar Materials
In elastic dissimilar materials joint subjected to cooling or heating, thermal stresses at the intersection of the edges and the interface are singular. For the Cu/Si3N4 composite, the relation between the intensity Khj of the stress field and bonded wedge angle was examined in detail.
The simultaneous equation can be represented in a matrix form as follows:
[凩{ω}={L}
where is the coeffisient matrix of an 8×8 system, and ω and L are the vector ω={a1,b1,c1,d1,a2,b2,c2,d2}T and L={0,0,0,0,T12,0,0,0}T. Furthermore, a funstion T12 is determined from interface condition for the r direction desplacement through the Mellin transform, defined as

where E2(=2G2(1+ν2)) is Young's modulus of material 2 and k12 is the stiffness ratio G1/G2. And all the stress intensities can be written as

where the function is independent of thermal expansion coefficient.

Model for a two-phase bonded structure with φ12=360°is shown in figure right.
Variations of wedge angle φ1 of material 1 verses Dundurs parameter α12 and stiffness ratio k12, in which Khg associated with a logarithmic singularity becomes zero, under
φ12=360.







For the case where the total wedge angle is 360°, the bonded wedge angle yielding Khj=0 does not disappear, and that approaches φ1=0°as k12→∞ and φ1=360°as k12→0. For the corresponding root p3, it is found the figure above that the stress intensity Khj for singular solution of type log r is zero in the case of φ12=360°and Kh3 for the no singularity solution is zero in the cases of the other total angles, i.e., φ12360°. That is, the singularity of type rp-1 corresponding to the third root p3 cannot disappear from the stress intensity Kh3.
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