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Thermomechanical fatigue (TMF) crack growth modeling has been conducted on Inconel 718 with dwell time at maximum load. A history dependent damage model taking dwell damage into account, developed under isothermal conditions, has been extended for TMF conditions. Parameter determination for the model is carried out on isothermal load controlled tests at 550–650 °C for surface cracks, which later have been used to extrapolate parameters used for TMF crack growth. Further, validation of the developed model is conducted on a notched specimen subjected to strain control at 50–550 °C. Satisfying results are gained within reasonable scatter level compared for test and simulated number of cycles to failure., Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through Swedish research programme TURBO POWER

Testing and simulation of aero-engine spectra with dwell times are reported in this paper. The modeling concept used is built on linear elastic fracture mechanics (LEFM) and provides a history-dependent evolution description of dwell damage and its interaction with cyclic load. The simulations have been carried out for three spectra: (1) cyclic loads, (2) combined sustained load and cyclic loads, and (3) slow load ramps and cyclic loads, all for surface cracks at 550 °C for Inconel 718. All simulations show reasonable good agreement with experimental results. Prediction of multiple tests of several batches is also provided to show statistical scatter., Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through Swedish Research Programme TURBO POWER

In this paper, scatter in crack growth for dwell time loadings in combination with overloads has been investigated. Multiple tests were performed for surface cracks at 550 °C in the commonly used high temperature material Inconel 718. The test specimens originate from two different batches which also provide for a discussion of how material properties affect the dwell time damage and overload impact. In combination with these tests, an investigation of the microstructure was also carried out, which shows how it influences the growth rate. The results from this study show that, in order to take overloads into consideration when analyzing spectrum loadings containing dwell times, one needs a substantial amount of material data available as the scatter seen from one batch to the other are of significant proportions., Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through Swedish research programme TURBO POWER

Crack length evaluations for cyclic loading and sustained loading at high temperature and a mix of both have been conducted on Inconel 718 surface crack specimens at 550 C-a similar to. The choice of method for evaluating the crack length is seen to have a non-negligible impact on the resulting crack propagation rate values. In this paper, some aspects regarding how to evaluate such testing when using the potential drop technique are presented, with the aim of giving a firm explanation on how to proceed for the best possible result., Funding Agencies|Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through the Swedish research programme TURBO POWER

Sustained load have been shown to give rise to increased crack growth rate at elevated temperature. Such loads generate a history dependent fatigue problem due to weakening and cracking of grain boundaries during dwell times, later broken apart during subsequent load cycles. So far most studies have focused on sustained load and the interaction of load cycles, overloads, and temperature, but few studies have been carried out for vibrations and how these affect the dwell time crack growth. Vibrations of different kinds are frequently seen in engine components, and present in combination with sustained loads a more realistic loading situation than the latter itself. An investigation of how a vibrational load affects the dwell time cracking and how to incorporate it in a modelling context is therefore of importance. In this paper a study of the most frequently used gas turbine material, Inconel 718, has been carried out. Mechanical testing has been conducted at 550◦C for surface cracks with and without the interaction of engine vibrations on sustained load, here represented by a superimposed high cycle fatigue (HCF) load. Subsequent investigation of the fracture behaviour was performed by Scanning Electron Microscope (SEM) and the modelling work has been conducted by incorporating the HCF load description within a history dependent crack growth law. The obtained results show reasonable accuracy with respect to the mechanical tests.

Testing and simulation of aero engine spectra with dwell Imes are reported in this paper. The modelling concept used built on LEFM and provides a history dependent evolution 2scription of dwell damage and its interaction with cyclic load. he simulations have been carried out for three spectra, 1) cyclic ?ads, 2) combined sustained load and cyclic loads and 3) slow ad ramps and cyclic loads, all for surface cracks at 550 C for nconel 718. All simulations show reasonable good agreement ith experimental results. Prediction of multiple tests of several atches is also provided to show statistical scatter

Thermo-mechanical fatigue (TMF) crack growth modelling as been conducted on Inconel 718 with dwell time at maximum;ad. A history dependent damage model taking dwell damage uto account, developed under isothermal conditions, has been xtended for TMF conditions. Parameter determination for the lodel is carried out on isothermal load controlled tests at 55050 C for surface cracks, which later have been used to extrapole parameters used for TMF crack growth. Further, validation the developed model is conducted on a notched specimen sub?cted to strain control at 50-550 C. Satisfying results are gained ithin reasonable scatter level compared for test and simulated umber of cycles to failure.

In this paper scatter in crack growth for dwell time loadings combination with overloads has been investigated. Multiple Jsts were performed for surface cracks at 5500C in the commonly sed high temperature material Inconel 718. The test specimens -iginate from two different batches which also provides for a disission of how material properties affect the dwell time damage rnd overload impact. In combination with these tests an investiation of the microstructure was also carried out, which shows 9w it influences the growth rate. The results from this study show tat, in order to take overloads into consideration when analysing,ectrum loadings containing dwell times, one needs a substantial mount of material data available as the scatter seen from one atch to the other is of significant proportions.