Beitrag zur Abschätzung der Kriechriβeinleitung in fehlerbehafteten Bauteilen

Versuche zur Bestimmung des makroskopischen Kriechanrisses. Unterscheidung der Versagensarten: Riβspitzenschädigung –Ligamentschädigung. Auswertung betriebsbeanspruchter Guβstücke mit Herstellungsfehlern. Vergleich der Bauteilbefunde mit den Laborergebnissen mit Hilfe der fiktiv elastischen Spannungsintensität K_lid des Anfangsrisses und der Nennspannung σ_n im Fernfeld des Risses. Zusammenhang üblicher Kriechdaten (R_mt und A_u) mit der Spannungsintensität K_lid für Kriechriβeinleitung.     

Assessing heat-affected zone properties of pressure vessel weldments using simulation techniques

This paper describes simulation methods for mechanisms occurring in the coarse grain heat affected zone (HAZ) of thick-walled weldments. The simulation process is divided into overheating simulation and simulation of stress-relief heat treatment. Overheating simulation is mainly practised by inductive or conductive heating and produces an HAZ-representative microstructure. For the stress-relief heat treatment simulation, annealing tests and constant load creep tests at stress-relief temperatures are carried out.Classifications in order of crack sensitivity and service-suitability are proposed. The order of crack sensitivity is derived from the magnitude of deformability and creep resistance in constant load creep tests. The order of service-suitability is based on the results of notch-impact tests (ISO-V) and tensile tests subsequent to both simulation treatments. The techniques are demonstrated on an example of an ASTM A 508 CI 2 (22 NiMoCr 37) plate material.     

Improving the uniformity in combustion-synthesized titanium carbide

The effects of reactant dispersion and outgassing on the microstructure of combustion-synthesized TiC were investigated. Pressure filtration casting of Ti+C colloidal suspension was shown to be an effective reactant dispersion method to improve the homogeneity of the product. The relation between the nature of the outgassing atmosphere and the formation of titanium oxide and precombustion titanium carbide was investigated. The combination of the colloidal dispersion technique with outgassing was shown to provide TiC products with reduced defects and improved microstructure.     

Darstellung von Poly-4-hydroxystyrol und dessen Umsetzung zu einem Chelataustauscher auf Basis o-(2-Hydroxyphenylazo)benzoesäure. Chelatbildende Austauscherharze,VIII

The radical pearl-copolymerization of 4-acetoxystyrene in the presence of divinylbenzene yields cross-linked poly-4-acetoxystyrene which can be carefully hydrolized to poly-4-hydroxystyrene. Poly-4-hydroxystyrene reacts with diazocompounds to chelate forming polymers with o,o′-disubstituted azo-groups. The synthesis of a chelating resin based on o-(2-hydroxyphenylazo)benzoic acid is described.     

Current capabilities and limitations of available stereological techniques

The various methods available for stereological analysis of sectioned material are reviewed with special emphasis on a critical evaluation of their capabilities, advantages and limitations. The review deals with four main topics: (I) Comparison with structural standards; (II) Point counting methods; (III) Image analysis with the scanning microphotometer; (IV) Automatic image analysis based on television systems. It is concluded that each of these approaches has its place, and that the choice essentially depends on the properties of the material and on the nature of the problem.     

Verminderung des Verformungsvermögens bei mehrachsigen Spannungszuständen unter Kriechbeanspruchung

Degradation of the Deformation Capacity under Creep due to Multiaxial States of Stress A method is proposed, which describes the degradation of the uniform true (rupture) strain φ due to the multiaxial stress states in creep. The method is based on the formulas of Siebel which describe the ratios of the uniform true strains in the 3 principle stress directions for any given states of stress: σ_m is the hydrostatic stress. These values for different given stress states are normalized by the principle stress σ_IZV for uniaxial tension with the same amount as for the multiaxial stress states. From such ratios it is possible to find out the real uniform true (rupture) strains φ for the different stress states in taking the uniform true (rupture) strain for uniaxial tension, φ_IBZV, as a basis: The comparison of predicted and tested φ-values proves that the formulas describe the toughness-degradations with the right tendency. For multiaxial states of stress it has to be kept in mind that we have two counterbalancing influences which are on the one hand the reduction of the creep rate due to lower v. Mises equivalent stresses and on the other hand the reduction of the deformation capacity, described above. A model ist proposed to estimate these influences of the states of stress on the creep rupture times.