Equilibrium configurations of single dislocation loops, as well as those of noncoaxial passing dislocation loops, have been determined by means of numerical techniques and by approximating the loops in terms of piecewise segments. Among other things, it is found that the passing behavior of the loops depends on the relative magnitidues of applied stress, dipole strength, and drag stress, and where the dipole strength is the stress to break the dipole formed by the unlike segments of the two loops and the drag stress is the stress needed to generate a unit length of the dipole. For an applied stress greater than the dipole strength, the dislocaiton loops pass one another and their equilbrium shape is identical to that of a single dislocation loop. The passing behavior of the loops also depends on whether or not the loops are constrained by the presence of other neighboring dislocation loops that are usually present in a real crystal. For applied stresses less than the dipole stress, but greater than or equal to the drag stress, the constrained dislocation loops, in particular, form elongated loops with long screw dipoles. For the cases where the cross slip of screw segments is difficult, the results also show that screw dipoles are much more stable than edge dipoles and arises from the higher dipole strength and lower drag stress for screw dislocations as compard to the corresponding stresses for edge dislocations.
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