Investigation on Material's Fatigue Property Variation Among Different Regions of Directional Solidification Turbine Blades—Part I: Fatigue Tests on Full Scale Blades

Abstract

At present, directional solidification (DS) made blades are commonly used in high per formance turbine for their better high temperature mechanical, especially in creep prop erties compared with the equiaxed grain (EG) blades made by conventional casting method. To predict DS blades' fatigue life accurately, one of the practical ways is to con duct tests on full-scale blades in a laboratory!bench environment. In this investigation, two types o f full scale turbine blades, which are made from DZ22B by DS method and K403 by conventional casting method, respectively, were selected to conduct high tem perature combined low and high cycle fatigue (CCF) tests on a special design test rig, to evaluate the increase o f fatigue life benefitted from material change. Experimental results show that different from EG blades, DS blades' fracture section is not located on the position where the maximum stress point lies. By comparing fatigue test results of the two types of blade, it can be found that the fatigue properties among different regions o f the DS blade are different, and its fatigue damage is not only related to the stress field, but also affected by different parts material's fatigue properties.

Experimental investigation on creep‐fatigue behaviours of as‐received and service‐exposed turbine blades: Mechanism and life evaluation

“…More recently, the full-scale turbine blades were experimentally investigated by simulating the in-service stress and temperature distributions along the critical section. [5][6][7][8] In the design phase, the current safe factor of turbine blade may be overly conservative. The accurate creep-fatigue life estimation model can help to extend the expected life of blade.…”

“…However, the experimental investigations on fatigue behaviour of as-received and serviced blades were limited in the literature. [5][6][7][8] Creep-fatigue interaction is a typical damage mode of turbine components, and attracts numerous attentions. [17][18][19][20] Wang et al 17 proposed a creep-fatigue life estimation model using the concept of the hysteresis energy density rate.…”

Effect of pneumatic shot peening on the high and low cycle combined fatigue life of K403 turbine blades

“…Large number of researches about the effect of PSP on the fatigue life of the metal are carried out [11][12][13][14][15][16][17][18][19][20][21][22][23]. Gao et al [11] investigate the effect of PSP on the small crack growth rate and fatigue life of 7475-T7351 aluminum alloy.…”

“…At present, the effect of PSP on material fatigue properties is usually studied with the smooth specimens. However, the differences between the full-scale turbine blades and smooth specimens, such as the geometry structure, heat treatment, manufacturing process and microstructure, may cause the discrepancy between their mechanical performance and life distribution [16]. And these factors may further affect the improvement of PSP on the fatigue performance.…”

Fatigue analysis for the first row of blades of a micro turbine under full loading cycle using transient modal analysis

“… An accurate measurement of the length as well as the thickness of the blade is necessary for the purpose of preventing the blade from creeping effect. Yan et al (2014), Yan and Nie (2008) investigated the vibrational characteristics of the materials' fatigue effect at different turbine parts. For this purpose, they first designated critical areas of the blade and then analyzed these areas by performing experimental tests.…”