Forming and Mechanical Joining Criteria for Beryllium Structures 670804
The deformation and mechanical joining of beryllium and beryllium-aluminum alloys is discussed with respect to a typical aerospace structure utilizing normal cross-rolled sheet, characterized by a maximum BeO content of 2.0% ingot sheet rolled directly from high purity cast billets, and 62% beryllium-SS'Yo aluminum alloy. Selection and application of material types is determined on the basis of mechanical properties, manufacturing considerations, and availability.
Surface imperfections induced by manufacturing procedures are shown to be greatly reduced or eliminated by proper stress relief and etching. Examples of simple unidirectional bends and complex forming, requiring severe multidirectional material flow, are given.
Mechanical joints resulting in net tension values equal to the yield strength of the beryllium are shown to be possible with proper choice of fasteners and joint geometry. It is, therefore, concluded that highly efficient, optimum weight beryllium structure can be achieved using presently available materials and manufacturing capability.