Structural Design of the Geometrical Shape of Interfaces in Bonded Dissimilar Materials Based on Theoretical Elastic Ana
- PDF / 2,318,532 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 105 Downloads / 171 Views
**
1. INTRODUCTION Bonded dissimilar materials such as a Ceramics-Metals joint may be expected to have the superior physical properties of both materials. The severest problem in a Ceramics-Metals joint is the residual stress, which forms during cooling in high-temperature bonding processes. Then, clarification of the effect of thermal loading on stress distribution near the edge of an interface is required for strength and fracture analyses of bonded dissimilar materials. Many researches [1]-[8] show that an apex on the edge of an interface has singularity stress. Three types of stress singularity are derived from 2-Dimensional theoretical elastic analysis by Bogy[I]-[4]. The index of stress singularity is one of the most important factors in the evaluation for stress distributions near the edge of an interface in bonded dissimilar materials[1]-[8]. It is also known that the intensity of the stress singularity depends on the geometrical shape of the interface and the combination of materials. The aim is for a high practical strength of the bonded system in which the geometric conditions of the interfaces should be chosen in order to reduce or eliminate the stress singularity. Most practical bonded joints, however, have 3-Dimensional interface shapes compare with 2Dimensional theoretical analysis models, and are composed with materials such as CeramicsMetals both of which have temperature-dependent mechanical properties. Most of the interfaces on Ceramics-Metals joints in conventional experimental studies are plane surfaces because most ceramics are too hard for machinery work. It is practically impossible to compare the intensity of the practical strength of bonded systems with various geometrical shapes of interfaces and the power of stress singularity by experiment. To design the interface only by theoretical elastic analysis, is regarded as hard. The authors have found that patterns of stress distribution on the plane-strain condition and on the axis-symmetrical condition are similar to each other, very close to the interface on restricted pairs of materials combination. Recent studies which the authors examined, succeeded in fabricating bonded dissimilar materials with a complicated geometrical interface shape using electrical conductive ceramics, TiB 2, which was EDMed (Electrical discharge machined using Ni as discharging electrode) and Ni. In an elastoplastic configuration such as 273 Mat. Res. Soc. Symp. Proc. Vol. 586 © 2000 Materials Research Society
Ceramics-Metals, if specified elastic properties such as the secant stiffness module can be determined, a relationship between the index of stress singularity on theoretical analysis and the practical strength of bonding will be obtained experimentally. From the results, a simple theoretical evaluation of the bonding strength based on the index of stress singularity which is determined by theoretical elastic analysis using the secant stiffness modules will be possible. In this paper, in order to evaluate the simplified method of theoretical estimation for t
Data Loading...
