Instrumented Impact Testing of Titanium Alloys

Abstract

The dynamic fracture toughness was determined for two titanium alloys (Ti-6A1-4V and Ti-6A1-6V-2Sn) from different suppliers and in various heat-treated conditions. The strain-rate effect associated with the dynamic test is shown to increase the fracture toughness for all the alloys with the exception of mill-annealed and duplex-annealed Ti-6A1-6V-2Sn, where the fracture toughness was found to be independent of strain rate. Dial energy per unit specimen area (W/A)d for precracked Charpy specimens can be used to calculate KId as long as a relatively flat fracture appearance (small shear area) is obtained. Otherwise, when a large amount of shear is present, the energy to maximum load (W/A)m or Pmax from the load-time trace must be used to calculate KId.

Determination of Dynamic Fracture Toughness Using Strain Measurement

“…This equation is available where the load is seen to increase linearly until maximum load is reached where fracture is initiated. K Id-Energy calculated by Ronald's energy equation [5]. ---------------------------------------- -----------------------------------------CT : Al7175-T74(dynamicc:strain) CT : Al7175-T74(dynamic:ASTM) Venkatanarayana [6] reported that the strength properties of M250 are independent of strain rate.…”

Rapid Inexpensive Tests for Determining Fracture Toughness

“…Therefore , if any correlation is expected , it should be between dynamic fracture toughness , K Id, and impact W/A . In studies on the titanium alloys , K Id calculated from the instrumented precracked C y load values were higher than the measured valid K Ic values and tended to produce a reasonable correlation with impact W/A values (Ewing and Raymond , 1974).…”

“…Data on Ti-6-4 (Ewing and Raymond , 1974) include d three combinations of heat s and specimen orientations , all for the mill annealed condition . The…”