The work hardening coefficient in the easy glide range is measured on Zn and Cd single crystals in the temperature range from 4.2 to 400 K. For low temperatures T/Tm ⪅ 0.15 work hardening was found to decrease rapidly with rising temperature, passes a minimum and at T/Tm = 0.3 there is a well developed maximum of work hardening. The location of this maximum depends on the shear strain rate. If the temperature becomes T/Tm ⪆ 0.3 the well known decrease of work hardening due to recovery processes can be observed. The measured temperature dependence of work hardening is contradictory to the established theories of work hardening of hexagonal metals, which affirm a constant ∂A in the low temperature range.

No abstract

From general physical laws simple formulae have been deduced from which the rigidity of an external fixation unit mounted in different ways becomes mathematically calculable. Furthermore, the stability of various mounting systems under bending forces was investigated experimentally. Particular attention was paid to details of operating technique which are of special importance to the stability of the whole construction. The calculated data are consistent with the mechanical test results. The best arrangement of the Steinmann pins and Schanz screws is discussed, and how to mount the frame optimally, depending on the specific type and location of the fracture. Special instructions concerning the mounting of the external fixation unit are given which, depending on the specific circumstances, guarantee optimum stability of the unit.

Due to the increasing popularity of unilateral dynamizable external fixators for treating tibial shaft fractures, many new devices are being introduced onto the market. Especially in such half-frame fixators, the choice of any particular device depends above all on the stability of its construction. This study compares the biomechanical stability of three systems tested in axial compression, torsion, and both anterior-posterior and medial-lateral bending. In terms of the nondynamized phase, the AO/ASIF tubular fixator (as a one-plane, double-tube, unilateral frame) and the Martin Mono-Dynafix are, in general, less stable than the Orthofix fixator. After dynamization, the AO/ASIF system becomes particularly weak and offers low resistance especially to torque and any force that is perpendicular to the plane of assembly. The other two tested devices evinced much more stability; the Orthofix fixator seems superior to the Dynafix due to the different diameter of its screws.

No abstract

No abstract

No abstract

No abstract