Die Anwendung der Ludwik-Gleichung zur Beschreibung des Spannungs-Dehnungs-Verlaufes

Bestimmung der Spannungen und Verformungen im Bereich der Gleichmaß- und der Einschnürdehnung. Erörterung der Auswirkungen prüfbedingter Störeinflüsse. Beschreibung des Verfestigungsverlaufes von neun Stählen unterschiedlicher Kohlenstoff- und Mangangehalte mit der Ludwik-Gleichung. 1-, 2-und 3-n-Verhalten. Einfluß von Prüftemperatur, Dehngeschwindigkeit, Ferritkorngröße und Werkstoffzusammensetzung.     

Evolution of dislocation structures and deformation behavior of iron at different temperatures: Part I. strain hardening curves and cellular structure

The deformation behavior of iron has been investigated at different temperatures by means of tension tests. There exist two temperature ranges for deformation. In the low-temperature range(T < 293 K), the flow stress σ, the work-hardening rate θ at ε = 0.06, and the yield stress σ_y decrease with increasing temperature, but in the higher temperature range(T ≥: 293 K), σ and θ at the same strain increase while σ_y decreases more slowly. The change of dislocation density, with temperature, atε = 0.06 exhibits the same tendency as that of the flow stress. The strainhardening rates decrease almost linearly with increasing stress up to necking in the low-temperature range, except the initial strain range. At the higher temperature range, the hardening rates decrease linearly with stress only at the early stage of deformation, but above certain strains, the decreases become more gradual; that is, the G-cr curves deviate from the linear region. The evolution of dislocation structure has also been observed by transmission electron microscopy (TEM). The results show that a substructural transition takes place in the nonlinear range of G-cr curves. In the linear decreasing region of strain-hardening curves, the deformation is controlled by the uniformly distributed dislocations or cell multiplication prevails. However, in the nonlinear region of G-cr curves, cell multiplication seems to be balanced by cell annihilation.     

Ermittlung der Dämpfung stickstoff- und kohlenstofflegierter Stähle mit unterschiedlichen Mangangehalten durch Zeitmessung

Beschreibung der Dämpfungsmessung zur Ermittlung interstitiell gelöster Elemente. Erläuterung der Ermittlung der Dämpfung durch Zeitmessung und Beschreibung des Versuchsaufbaus mit Zeitmeßeinrichtung und Datenverarbeitung. Darstellung der Versuchsergebnisse in Dämpfung-Temperatur-Kurven an Eisenlegierungen mit Stickstoff und Kohlenstoff und unterschiedlichen Mangangehalten.     

Mohs' surgery of periocular basal cell carcinoma using formalin-fixed sections and delayed closure

Mohs' surgery of periocular basal cell carcinoma (BCC) ensures a high cure rate with maximal preservation of normal tissue. The formalin-fixed paraffin-embedded tissue technique allows Mohs' surgery to be performed using routine pathology facilities and permits the efficient use of operating room personnel and theatre time. The inevitable delay between excision and closure may potentially result in a poor functional and cosmetic outcome, particularly around the eye. We prospectively studied all patients with periocular BCC treated with this technique at our unit between 1985 and 1996. One hundred and twenty-three periocular BCCs in 120 patients were treated. Microscopic clearance was achieved in all cases. Closure was performed on average 5 days after the initial excisional stage. Closing procedures included direct closure, flaps and grafts. Significant complications affecting outcome were noted in only two patients. Eighty-eight per cent of patients assessed had a functional and cosmetic result regarded as excellent, good or adequate. Mohs' surgery of periocular BCC using formalin-fixed paraffin-embedded tissue and delayed closure results in a satisfactory functional and cosmetic outcome and offers a viable alternative to the frozen section fresh tissue technique.     

Toxic effects of aliphatic chlorinated by-products from vinyl chloride production on marine animals

The acute toxic effects of chlorinated aliphatic hydrocarbons, formed as by-products from one Swedish and one Norwegian plastic production factory, were examined by experiments with cod (Gadus morhua), shrimp (Crangon crangon) and a polychaete (Ophyryotrocha labronica). The toxicity of 1,2-dichloroethane—a dominating compound of the by-products—and a distillate with heavier compounds were also estimated. The toxicity (48 h, LC50) ratio between the concentrations of a Swedish by-product, a Norwegian by-product, and dichloroethane was 1:9:34. The effects of 1,2-dichloroethane, 1,1,2-trichloroethane and 1,1,2-trichloroethene on the reproductivity, and on the survival of adults of Ophryotrocha were studied. The reproductivity was affected by these components in far lower concentrations than those having acute toxic effects on adult specimens. In one experiment series Ophryotrocha was exposed suddenly to the test solutions and in a second series the first presentation was made by a successive increase of the concentration during one hour. The estimated 96-h LC50-values for the test with successive increase were 1·8–3·1 times higher than those found for the test with sudden exposure. It is suggested that a physiological shock in the start of bioassay experiments might have reduced the LC50-values in many previous tests.     

Evolution of dislocation structures and deformation behavior of iron at different temperatures: Part II. dislocation density and theoretical analysis

The evolution of dislocation density in iron deformed at 173 K and at room temperature has been examined by transmission electron microscopy (TEM). At room temperature, the dislocation density in the cell walls increases as the deformation progresses up to large strains, whereas in cell interiors, the density evolves toward a saturation value. A linear relationship exists between the flow stress and the square root of total dislocation density both at 173 K and room temperature. The dependence of deformation behavior on the evolution of dislocation structures is discussed in terms of a model considering the dislocation distribution during deformation. Comparison of the calculated result using this model with the experimental curve at room temperature gives excellent agreement. The changes of deformation behaviors at different temperatures can be described by the effect of temperature on the evolution of dislocation distribution.