Joint assembly for superconducting motors

Abstract

A torsional joint assembly and method of making same having members of formed of dissimilar materials bonded together at calculated angles to result in essentially singularity-free joints.

I claim:  
     
         1 . A joint assembly comprising: 
 a first member having a first surface at a first angle to an external surface of the first member and formed of a first material;    a second member having a second surface at a second angle to an outer surface of the second member and formed of a second material which is different from the first material, each of the first and second materials being characterized by a shear modulus and the second angle being a function of the shear modulus of the first and second materials and of the first angle;    a bonding material which bonds the first and second members together, the bonding material being characterized by a bonding stress;    the first angle being determined according to the equation:              sin                 φ     =       σ   a       σ   c                         where σ α  is the bonding stress and σ c  is a shear stress of the first material; and    the second angle being determined according to the equation:              tan                 β     =           G   yz   c       G       y   ′        z     s       ·   tan                   φ                       where G yz   c  is a shear modulus of the first material in the y-z direction and G y′z   s  is the shear modulus of the second material in the y′-z direction where y′ is parallel to the outer surface and z is perpendicular thereto.    
     
     
         2 . The joint assembly of  claim 1 , wherein the first material is a thermal insulator and the second material is a metal.  
     
     
         3 . The joint assembly of  claim 2 , wherein the first material is a composite.  
     
     
         4 . The joint assembly of  claim 1 , wherein the bonding material is adhesive.  
     
     
         5 . A singularity-free adhesively bonded joint assembly adapted to rotate about a central axis through the joint assembly comprising: 
 a first member having a first surface at a first angle to an external surface of the first member and formed of composite;    a second member having a second surface at a second angle to an outer surface of the second member and formed of metal, each of the first and second materials being characterized by a shear modulus and the second angle being a function of the shear modulus of the composite and metal and of the first angle;    an adhesive which bonds the first and second members together, the adhesive being characterized by an adhesion stress and the composite is characterized by a composite stress;    the first angle being determined according to the equation:              sin                 φ     =       σ   a       σ   c                         where σ α  is the adhesion stress and σ c  is the composite stress; and    the second angle being determined according to the equation:              tan                 β     =           G   yz   c       G       y   ′        z     s       ·   tan                   φ                       where G yz   c  is a shear modulus of the composite in the y-z direction and G y′z   s  is the shear modulus of the metal in the y′-z direction where y′ is parallel to the outer surface and z is perpendicular thereto.    
     
     
         6 . A method for forming a singularity-free bonded joint comprising the steps of: 
 providing a first member having a first surface at a first angle to an external surface of the first member and formed of a first material;    providing a second member having a second surface at a second angle to an outer surface of the second member and formed of a second material which is different from the first material, each of the first and second materials being characterized by a shear modulus and the second angle being a function of the shear modulus of the first and second materials and of the first angle;    connecting the first and second members together with a bonding material, the bonding material being characterized by a bonding stress;    the first angle being determined according to the equation:              sin                 φ     =       σ   a       σ   c                         where σ α  is the bonding stress and σ c  is a shear stress of the first material; and    the second angle being determined according to the equation:              tan                 β     =           G   yz   c       G       y   ′        z     s       ·   tan                   φ                       where G yz   c  is a shear modulus of the first material in the y-z direction and G y′z   s  is the shear modulus of the second material in the y′-z direction where y′ is parallel to the outer surface and z is perpendicular thereto.