Thermo-electro-mechanical modeling of thermal fatigue failure process of corset samples from single crystal nickel superalloys

High-temperature single-crystal nickel-based alloys [1] are widely used for the manufacture of rotor blades of gas turbine engines (GTE). The thermal-fatigue strength of such materials with a pronounced anisotropy and a sensitivity of mechanical properties to the temperature is currently not fully studied. For the investigation of thermal fatigue durability under wide range of temperatures with and without intermediate delays the experiments are carried out on different types of samples, including corset (plane) specimen on the installation developed in NPO TSKTI [2]. The corset sample is fixed with two bolts in a massive snap and is heated periodically by passing electric current through it. The aim of the research is determinate numerically the thermal and stress states of the corselet specimen under cyclic electric loading and to study systematically the effect of delay at maximum temperature on the thermal fatigue durability on the base of the deformation criterion [3-5] of thermal-fatigue failure for single crystal superalloys using the results of finite element (FE) simulation of full-scale experiments. The coupled transient thermo-electrical analysis of the corset sample is carried out in a FE program ANSYS with taking into account the thermal dependency of material properties, nonstationary Joule heating process, the convective heat exchange and radiant radiation between the sample and the environment. Modeling of inelastic cyclic deformation of corset samples are carried out using the FE program PANTOCRATOR based on the application of micromechanical (physical) models of plasticity and creep of single crystals. These computations were carried out for superalloys VZHM4, VIN3 and ZHS32. Modeling of processes of heating and thermal fatigue fracture of alloys was carried out for temperature modes: 150-900 °C, 500-1050 °C and 700-1050 °C. The results of multivariate computations for full-scale model allow to define the equivalent length of the simplified model of sample, which was found for the alloy VZHM4 equal to 34-42 mm, for the alloy VIN 3 was equal to 38-46 mm and for the alloy ZHS32 was equal to 40-52 mm . In the FE formulation in PANTOCRATOR, the length of the specimen for both alloys was taken to be 40 mm. The comparison of the results of FE simulations demonstrates a good agreement with the experimental results for the temperature distribution along the samples for both considered heating modes. Taking into account obtained temperature distribution, the problem of inelastic deformation of the sample was solved and the thermal fatigue damage is determined. The curve of the influence of the delay time at the maximum temperature on the number of cycles before the formation of the macrocrack was constructed for the two alloys and satisfactory correlation with the experiment was obtained.


Вуз: Санкт-Петербургский государственный политехнический университет (ФГБОУ ВПО «СПбГПУ»)

ID: 5be8801a7966e104eca3dcca
UUID: 3f3641b0-c814-0136-3e09-525400005860
Язык: Английский
Опубликовано: почти 4 года назад
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Артем Савиковский

Санкт-Петербургский государственный политехнический университет (ФГБОУ ВПО «СПбГПУ»)


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