[en] Defects in static components subjected to high temperatures - as e.g. turbine casings, containers, pipe specials - are primarily induced by the recurrent temperature gradients and transients, or the resulting hampered elongation of the material, due to non-steady operation. The examinations and experiments presented in this report achieved their objective, to significantly improve the accuracy of data describing the performance until incipient cracking of such anisothermally and LCF-stressed components with metal temperatures up to 600 C, taking as a basis the available isothermal LCF data of the materials and taking into account the non-linear materials behaviour at the given temperatures. Based on elongation-controlled isothermal LCF experiments with rod-type specimens, performed in the temperature range simulating operating conditions, and various anisothermal LCF experiments with various model shapes made of the cast materials GGG SiMo 3 and G-X 10 CrMoVNb 9.1, recommendations are derived from the correlation of measured/calculated numbers of stress cycles until incipient cracking, for formulation of laws and reference temperatures required for predicting the number of expected stress cycles until incipient cracking of high-temperature components. These recommended methods are verified by means of stress analyses of those highly stressed zones of pressurized casings of superheated steam turbines most at risk of crack initiation. (orig./CB)

[en] The effect of strain induced martensite on the low cycle fatigue behavoir of AISI 304 austenitic stainless steel was investigated. During low cycle fatigue, the austenitic stainless steel showed continuous cyclic hardening. The extent of cyclic hardening was increased with decreasing austenite stability. The austenite stability was controlled by annealing time and temperature, which resulted in different carbide morphology. The continuous cyclic hardening behavior was considered to be resulted from the continuous martensitic transformation during low cycle fatigue. The amount of transformed martensite was measured with ferrite scope. (Author)

[en] We develop a damage calculation to describe low-cycle fatigue behavior of a martensitic stainless steel (12%Cr, Z20CDNV 12-1 type) at high temperature (350-600⁰C). The proposed model is applied to thermal fatigue life prediction

[en] A sudden drop in power after a beam interruption leads to thermal fatigue effects in structural components in the blanket of an accelerator driven system. These thermal fatigue effects limit component lifetimes. A sudden return to power after a beam interruption can contribute significant additional thermal fatigue and greatly reduce component lifetimes. One obvious solution is a gradual return to power after a beam interruption. There are two potential problems with this solution. One problem involves interruptions that are longer than the thermal time constants of thin structural members but shorter than the time constants of thick structural members. In such a case, a gradual return to power reduces the additional thermal fatigue in the thin structural members but increases the thermal fatigue in thick structural members. Some compromise is necessary. The other problem is that for thick components with long thermal time constants a long, gradual return to power is required to minimize additional thermal fatigue. Such a slow return to power can reduce the utilization or the effective load factor of the system. Specific examples of beam interruptions with various assumptions on return to power are provided for a preliminary design for the blanket of the Accelerator Driven Test Facility. Also, mitigation options to increase component lifetime are discussed. These mitigation options include improving beam reliability and modifying the blanket design to better tolerate beam interruptions

[en] By using the strain-range partitioning method, the fatigue life of high-heat-load components made of oxygen-free copper have been successfully predicted within a factor of two. Following a successful study on the prediction of fatigue life of high-heat-load components made of Glidcop, the thermal limitation of oxygen-free copper (OFC), which is used more commonly than Glidcop, has been studied. In addition to its general mechanical properties, the low-cycle-fatigue (LCF) and creep properties of OFC were investigated in detail and compared with those of Glidcop. The breaking mode of OFC, which was observed to be completely different from that of Glidcop in a fatigue fracture experiment, clarified the importance of considering the creep–fatigue interaction. An additional LCF test with compressive strain holding was conducted so that the creep–fatigue life diagram for out-of-phase thermal fatigue could be obtained on the basis of the strain-range partitioning method. The life predicted from elasto-plastic creep analysis agreed well with that determined from the void ratio estimated in the fatigue fracture experiment

[en] This paper briefly discusses the results of a systematic study of thermal ageing in thin film resistors over high-temperature range (from 400 up to 600 C). The relative changers in resistance and changes in TCR have been studied as a function of ageing temperature and time, aspect ratio and termination material. Termination effects for RuO₂/Au and RuO₂/Pd-Ag systems have been separated from intrinsic (bulk) stability of resistive material. The combination of commercially available Du Pont resistive composition and Polish-made Au conductor permits for continuous or semicontinuous long-term operation at 400 C. (author). 8 refs, 2 figs

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[en] The actual effect of elastic follow-up on the creep modified shakedown limit, for SS 316 at 600⁰C, is investigated by the inelastic analysis of a rectangular beam which is fixed from both ends and has a locally reduced cross section and is subjected to a cyclic thermal load. Two beams are chosen, one with a small degree of elastic follow-up and the other with a considerably large degree of elastic follow-up. The accumulated strains and creep-fatigue damage sums are evaluated by a full time stepping inelastic analysis and the results are compared with those predicted by two simplified methods. (orig./HP)