A ⟨110⟩‐oriented dark‐line defect (DLD) has been induced by mechanical bending in GaAs1−xAlxAs double‐heterostructure (DH) wafers. Both the concave upward and the convex upward bending (with the DH epitaxial layer as the upward surface) of the DH wafer has been carried out using a four‐point bending technique. The DLD formation has shown both the stress‐direction dependence and the asymmetry of the DH wafer. Photoluminescence topography has shown that the characteristics of the DLD’s are exactly the same as those of the optically induced DLD’s. From experimental results, it is conjectured that a glide‐multiplication mechanism is probably acceptable for the production of the ⟨110⟩ DLD dislocations.