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research-article

NOVEL TEST FACILITY FOR INVESTIGATION OF THE IMPACT OF THERMALLY INDUCED STRESS GRADIENTS ON FATIGUE LIFE OF COOLED GAS TURBINE COMPONENTS

[+] Author and Article Information
Marcus Thiele

Technische Universität Dresden, 01062 Dresden, Germany
marcus.thiele@tu-dresden.de

Uwe Gampe

Technische Universität Dresden, 01062 Dresden, Germany
uwe.gampe@tu-dresden.de

Kathrin Anita Fischer

Siemens AG, 10553 Berlin, Germany
kathrin-anita.fischer@siemens.com

1Corresponding author.

ASME doi:10.1115/1.4041129 History: Received July 12, 2018; Revised July 18, 2018

Abstract

A novel test facility was designed and set up for the investigation of the influence of stationary temperature, and thus thermal induced stress gradients - on the damage evolution of cooled gas turbine components. Thermally induced stress gradients differ from geometrically induced stress gradients with respect to stress mechanics by means of the independence from external loads and material mechanics by means of the influence of temperature on material properties and strength. Regarding the contribution and evaluation on damage, this characteristic feature in turbo machinery is currently not fully understood. The authors developed a test bench with a unique radiant furnace design to achieve significant heat fluxes of q ?=1.6 MW/m^2 on cylindrical specimen. The austenitic stainless steel 316L was chosen as model material for the investigation of thermally induced stress gradients and, based on this analysis, low cycle fatigue tests with superimposed temperature gradients were done. Linear elastic finite element studies have been performed to calculate the local stress strain field and the service life of the test specimen. The test results show a considerable influence of the temperature gradient on the low cycle fatigue life of the investigated nickel base super alloy. Both the temperature variation over the specimen wall and the thermally induced stresses are stated to be the main driver for the change in low cycle fatigue life. The test results increase the understanding of fatigue damage mechanisms under local unsteady conditions and can be used as basis for improved lifetime calculation methods.

Copyright (c) 2018 by ASME
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