Explosive pipe coupling method

Claim 1

In a method of explosively joining inner and outer tubular members by internal explosive shock force, the improvement comprising: assembling, in radial proximity, a. an inner, effectively smooth walled, tubular metal member, b. an outer tubular metal member having at least one circumferential internal groove. c. an explosive charge surrounded by a plug of shock force transmitting material within said inner tubular member and with said material in contact with said inner tubular member, and d. an effectively smooth walled, expansible tubular die surrounding said outer tubular member; and detonating said explosive charge and transmitting shock force produced thereby radially through said force transmitting material to the inner tubular member of such magnitude to radially expand and plastically deform said inner member beyond its yield point and cause plastic flow of the inner member metal where surrounded by said outer member into permanent conforming contact with the outer tubular member and to form said inner member into said internal groove, while simultaneously radially expanding and only elastically deforming said outer member by radially expanding said member and radially expanding said expansion die to deform said outer member approaching but not exceeding its yield point, and allowing said outer member to substantially recover its elastic deformation to prodUce residual circumferential compressive stresses in said inner tubular member and residual circumferential tension stresses in said outer tubular member, the combination of the radial compressive forces exerted by the outer member on the inner member due to elastic recovery of the outer member and the formation of the inner member into the groove providing a fluid tight as well as axially strong mechanical joint.