[en] Following a series of cooperative studies A-I and A-II (phase III) concerning the inelastic behaviour of high temperature materials under uniform state of stress, finite element analyses were carried out on circumferential notched cylinders subjected to plasticity-creep interaction conditions. Using an electric capacitance type extensometer ''Strain-Pecker'', which is capable of measuring a local strain response with a gauge length of 0.5mm under high temperature conditions, stress-strain responses for both global and local regions near the notch root were evaluated. Ten kinds of inelastic constitutive model were introduced into a finite element code, and the responses for four kinds of loading pattern were examined for two types of notch shape. ((orig.))

[en] High-temperature operating experience is lacking in pressure vessel materials that have strength levels above 586 MPa. Because of their tendency toward strain softening, we have been concerned about their behavior under nonsteady loading. Testing was undertaken to explore the extent of softening produced by monotonic and cyclic strains. The specific materials included bainitic 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel containing vanadium, titanium, and boron, and a martensitic 9Cr-1Mo-V-Nb steel. Tests included tensile, creep, variable stress creep, relaxation, strain cycling, stress cycling, and non-isothermal creep ratchetting experiments. We found that these steels had very low uniform elongation and exhibited small strains to the onset of tertiary creep compared to annealed 2 1/4Cr-1Mo steel. Repeated relaxation test data also indicated a limited capacity for strain hardening. Reversal strains produced softening. The degree of softening increased with increased initial strength level. We concluded that the high strength bainitic and martensitic steels should perform well when used under conditions where severe cyclic operation does not occur

[en] Results of an investigation are presented of creep crack growth in tube steels using 10 MoV 6 3 and 10 CrMo 9 10. Particular attention is paid to the load parameter C*. The current knowledge in the fields of empirical load parameter choice, specific materials behavior, continuum mechanics, and creep crack growth models is reviewed. The creep crack growth in steady state is qualitatively described. A prediction of the crack growth and hence of the lifetime on the basis of conservative assumptions is explained. A comparative life time estimate is proposed. The parameters which influence the creep crack growth are discussed. The creep crack growth micromechanism is explained too. (orig./MM)

[en] The effect of creep stress on the crack growth at high temperatures was examined using the heat-resistant steel 13 CrMo 44 (St. 1.7335). The material was loaded with a static load at 560deg C, which led to a permanent strain of 2%. The tensile test values remained unchanged, but the notch impact work was considerably reduced. The fatigue crack growth in CT samples was not affected by the creep prestress. However, due to higher stress in the remaining ligament there was an acceleration in cracking compared to the initial state in the CCT samples. Stopping times at the load reversal points led to additional creep damage and therefore to a further rise in the crack growth rate. The dependence of the crack growth rate on frequency at high temperatures can be approximately described in the creep range by a linear superimposition of fatigue crack growth and creep crack growth. (orig./DG)

[en] A representation of the fracture toughness versus temperature curve is proposed which is based on the corresponding curve of the reference temperature concept but, considers also the temperature regime below -110deg C. It results in a type of lower boundary curve, this complying with the nuclear safety standards. In addition, it offers the advantage that the entire curve can be defined by just measuring fracture toughness values within its lower shelf region. (orig.)

[en] To develop nonisothermal modeling of inelasticity we postulate a similarity equation, which specifies the positional change of a kinematic hardening variable relative to the bounding surface under temperature variation. It results in a temperature-change induced term in the evolution equation of the kinematic hardening variable. On the assumption that the kinematic hardening variable consists of various components, the proposed model is transformed to an equivalent form based on multisurfaces in which the configuration of nested multisurfaces changes with a similarity under temperature variation. Discussing the condition for the temperature-history independence of the inelastic stress response, which is observed rather often in experiments, we derive analytical expressions for the stress versus strain relations under monotonic and cyclic thermomechanical loadings. Finally we show the validity of the proposed model in comparison with experimental data of 2.25Cr-1Mo steel. (orig.)

[en] The fabrication, inspection, shipment, and mechanical properties of a modified 9 Cr-1 steel test article for exposure in the Sodium Components Test Loop (SCTL) at the Energy Technology Engineering Center (ETEC) are described. The test article delivered consisted of modified 9 Cr-1 Mo steel pipe 232 mm in diameter by 12.7-mm wall by 610 mm long. This pipe was safe ended with type 304L stainless steel spool pieces 152 mm long on each end. The joint between modified 9 Cr-1 Mo and type 304L was made with ERNiCr-3 filler wire. The entire test article was postweld heat treated 1 h at 732⁰C and ultrasonically inspected before use. Radiography was used to inspect the welds between modified 9 Cr-1 Mo and type 304L stainless steel. The test article was delivered to ETEC on schedule on October 4, 1982. After delivery of the test article, we fabricated an additional piece of the same dimensions by the same procedure for archive purposes, mechanical property testing, and comparison with the actual test article after test. A part of this archive piece also provided a nondestructive examination standard for in-service inspection for ETEC. The archive specimen has already been subjected to tensile and creep testing, microstructural evaluation, and thermal aging for 2000 h at 510⁰C. The test article has completed a year of operation in the SCTL. We expect to remove this pipe after three years of operation for testing and examination

[en] Effect of water flow rate on the environmentally-assisted cracking (EAC) response of a high-sulfur ferritic steel was studied at 243C. In contrast to earlier studies with compact-type specimens, this study employed relatively large tight semi-elliptical surface cracks tested under generally linear-elastic conditions. Flow velocities parallel to the crack as low as 1.68 - 1.84 m/s were effective in mitigating EAC

[en] Interdependences between the stresses temperature and deformation rate for different stages of plastic flow of VT20 - hydrogen system alloys with hydrogen content of 0; 0.40; 0.58 (mass %) are experimentally measured and described by empirical ratios in the temperature range of hydrogen plasticization effect manifestation. Possible mechanisms controlling alloys plastic deformation are discussed

[en] The effect of thermomechanical parameters of rings production on mechanical properties is studied. The change of properties along the ring cross-section is established as the result of heating non-uniformity. Technological heatings lead inevitably to the decrease of the ultimate strength along the whole cross-section