Effect of stress ratio on VHCF behavior for a compressor blade titanium alloy

Abstract

Effect of stress ratio on fatigue properties of a titanium alloy (TC-17) in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) were investigated by electromagnetic and ultrasonic fatigue testing. The S-N curves at R = À1, 0.1, 0.5 and 0.7 at 110 Hz and 20 kHz were obtained and discussed. The effects of frequency on fatigue strength was also investigated. It was concluded that the fatigue strength with 50% fatigue failure probability at R = 0.1, 0.5 and 0.7 is lower to the Goodman line and shows a bilinear decreasing trend. Cleavage fracture of primary grains in the surface and interior initiation zone were observed. The formation of the facets induced by the basal or prismatic slips of the H.C.P grains decreased the fatigue strength with variation in mean stress.

Stress Ratio and Notch Effects on the Very High Cycle Fatigue Properties of a Near-Alpha Titanium Alloy

“…This typical failure feature of Type II has attracted the attention of a large number of researchers. However, with higher requirements for lightweight design and corrosion resistance, research on titanium alloys (Type I materials) have been increasing in recent years [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. The Ti-8Al-1Mo-1V titanium alloy tested in this study is used to manufacture low-pressure compressor blade for an advanced military gas turbine engine [ 12 ].…”

“…Similar to “fish-eye” failure in Type II materials, titanium alloys can also initiate interior fatigue cracks in the VHCF regime [ 13 , 14 , 15 , 16 ]. Therefore, the competition between surface-induced crack initiation and interior-induced crack initiation do not necessarily lead to the appearance of a step-wise or duplex S - N curve for smooth specimens [ 7 ]. The facetted features are revealed in the crack initiation region [ 17 , 18 ], and it becomes more obvious as the stress ratio is increased [ 7 , 8 ].…”

“…Therefore, the competition between surface-induced crack initiation and interior-induced crack initiation do not necessarily lead to the appearance of a step-wise or duplex S - N curve for smooth specimens [ 7 ]. The facetted features are revealed in the crack initiation region [ 17 , 18 ], and it becomes more obvious as the stress ratio is increased [ 7 , 8 ]. However, sometimes no facet is observed at the stress ratio ( R ) of −1 [ 6 ].…”

“…However, sometimes no facet is observed at the stress ratio ( R ) of −1 [ 6 ]. Most researchers believe that the facets result from the fracture of primary α grains [ 7 , 8 , 17 , 19 ].…”

Impact-Sliding Tribology Behavior of TC17 Alloy Treated by Laser Shock Peening

“…These materials commonly exhibit excellent properties, such as high strength to weight ratio, excellent toughness, and outstanding corrosion resistance [1,2]. TC17 titanium alloy has been widely used to manufacture aero-engine fans, compressor disks, jetengine blades, and other important parts of advanced aircrafts [3,4]. However, titanium alloys usually express poor wear resistance and low surface hardness, due to their structural characteristics, which always limit their wide application [5,6].…”