Analysis of the temperature dependence of the fracture stress of sharp notched bending specimens of a structural steel with respect to intermediate transitions

The flow and fracture stresses, σ_y^g and σ_f^g (δ = crack tip displacement), of sharply notched bending specimens of a structural steel U St 37-1 are measured in the temperature range from full scale to small scale yielding. The best adaption of the experimental results for σ_f^g is obtained by a curve which exhibits an intermediate transition, i.e. which follows in a temperature range between an upper, T_tM¹ and a lower, T_tl¹, transition temperature to the curve σ_y^g(T) for the flow stress with a constant δ = δ₁. This transition corresponds to that of the slip to the twin nucleated fracture. Two analyses [3,5] according to the local fracture stress, σ_f^*, concept show that the amount and the temperature dependence of σ_f^* are somewhat different for both methods, but that both exhibit an increase of σ_f^* in the transition range. It is concluded that each transition in the nucleation mode of the fracture is connected with such a transition in the fracture stress. It may, however, become indistinct or even be covered by the scatter of the experimental points.     

Diffusion von Silizium,Phosphor, Schwefel und Mangan in flüssigem Eisen

Zusammenhang zwischen Diffusion und Aktivität. Messung der Diffusionskoeffizienten von Silizium, Phosphor, Schwefel und Mangan in flüssigem Eisen sowie in kohlenstoffgesättigtem, flüssigem Eisen. Angabe der Konzentrationsabhängigkeit und der Temperaturabhängigkeit der ermittelten Diffusionskoeffizienten.     

Three-dimensional analytical calculation of induction machines with multilayer rotor structure in cylindrical coordinates

An analytical three-dimensional solution of the field problem of induction machines with multilayer rotor structure is presented in cylindrical coordinates. The curvature of the machine is no longer neglected as against the known solution in cartesian coordinates. This results in much higher accuracy for machines with a large air-gap width or small bore radius. In addition, the analysis is performed for an arbitrary number of rotor layers and for arbitrary speed of each rotor layer.

Stress- and strain-induced formation of martensite and its effects on strength and ductility of metastable austenitic stainless steels

The effects of deformation-induced formation of martensite have been studied in metastable austenitic stainless steels. The stability of the austenite, being the critical factor in the formation of martensite, was controlled principally by varying the amounts of carbon and manganese. The formation of martensite was also affected by different test and rolling temperatures, rolling time, and various reductions in thickness. The terms “stress-induced” and “strain-induced” formation of martensite are defined. Experimental results show that low austenite stability resulted in stress-induced formation of martensite, high work-hardening rates, high tensile strengths, low “yield strengths,” and low elongation values. When the austenite was stable, plastic deformation was initiated by slip, and the work-hardening rate was too low to prevent early necking. A specific amount of strain-induced martensite led to an “optimum” work-hardening rate, resulting in high strengthand high ductility. For best results processing should be carried out aboveM _d and testing betweenM _d andM _s. Mechanical working aboveM _d had a negligible effect on the yield strength betweenM _d andM _s when the austenite stability was low, but its effect increased as the austenite became, more stable. Serrations appeared in the stress-strain curve when martensite was strain induced.