Bonding interface

Defect Evaluation in Diffusion Bonding Interface of Dissimilar Metals Using Ultrasonic Testing Method. 

This study detects the defect of the void and the exfoliation in the solid phase diffusion bonding interface of ductile cast iron and stainless steel with a nickel insert metal using ultrrasonic testing method, and examine the influence of mutual interference of the reflectional wave both the defect and the interface. 

Fig.3 shows the defect position on the bonding interface and the model of the reflective echo. The defects are exists on each bonding surface as(ii) (iv), is no exist as (i). 

The reflective echo on the bonding interface of similar materials is caused only by the defect. On the other hand, the... 

The echo height F/B of the expression (1) is changed that the wave length X becomes shorter, the frequency becomes increaser and the reflective coefficient of sound pressure in the bonding interface becomes higher. 

Therefore, the establishment of the Non-Destructive Inspection technique to understand the presence of the defect on the bonding interface by the ultrasonic wave etc. accurately is demanded. And, the reliability of the product improves further by feeding back accurate ultrasonic wave information obtained here to the manufacturing process. 

This study was in real time measured that the reflective echo height of the bonding interface in the solid phase diffused bonding process of carbon steel and titanium using ultrasonic testing method. As a result, the following were made discernment. 

The plastic deformation, the creep deformation, and the bonding process on the bonding interface can be presumed from the height of the echo. 

Fig.7 shows the relation of the F/B, the temperature T and the time t as the retio of contact surface area Sa /So=50%. O mark is the B echo on the bottom of the upper specimen A mark is the F echo on the bonding interface. The B echo has changed in the changing temperature T. Therefore, the really reflective echo height F/B on... 

The Sa is the bonding interface area. And the calculative value is almost corresponding to the experimential value. This calculative value is described in consideration. 

Fig. 10 shows the analysis result of the element by EPMA and the microphotograph on the bonding interface at the bonding... 

Fig. 10 Microphotograph and analysis result of clement by EPMA on bonding interface...

Nondestructive Testing. Nondestmctive inspection of an explosion-welded composite is almost totally restricted to ultrasonic and visual inspection. Radiographic inspection is appHcable only to special types of composites consisting of two metals having a significant mismatch in density and a large wave pattern in the bond interface (see Nondestructive evaluation). 

Ra.m Tensile. A ram tensile test has been developed to evaluate the bond-2one tensile strength of explosion-bonded composites. The specimen is designed to subject the bonded interface to a pure tensile load. The cross-section area of the specimen is the area of the aimulus between the outer and inner diameters of the specimen. The specimen typically has a very short tensile gauge length and is constmcted so as to cause failure at the bonded interface. The ultimate tensile strength and relative ductihty of the explosion-bonded interface can be obtained by this technique. 

Transition Joints. Use of explosion-clad transition joints avoids the limitations involved in joining two incompatible materials by bolting or riveting. Many transition joints can be cut from a single large-area flat-plate clad and deflvered to limit the temperature at the bond interface so as to avoid undesirable diffusion. Conventional welding practices may be used for both similar metal welds. 

Discontinuities (e.g., imperfectly bonded interfaces or mbber processing flaws)... 

Apart from the elastic stress transfer at the perfectly bonded interface, another important phenomenon that must be taken into account is the stress transfer by friction, which is governed by the Coulomb friction law after the interface bond fails. Furthermore, matrix yielding often takes place at the interface region in preference to interfacial debonding if the matrix shear yield strength, Xm is significantly smaller than the apparent interface bond strength, tb. It follows thus... 

---