Research on fracture toughness and strength of thin-walled Ti–B25 pipes using small notched beams

Abstract

One of the most essential processing procedures for thin-walled titanium pipe is hot extrusion. The non-uniform distribution of microstructure along the wall thickness and pipe axis of thin-walled pipes produced with this technology, on the other hand, would affect the non-uniformity of mechanical characteristics. Although it is generally difficult to process specimens that meet the linear elastic fracture mechanics (LEFM) conditions for this thin-walled titanium alloy Ti–B25 pipe, a simple method for non-linear elastic fracture of material was used to test the yield strength σY and fracture toughness KIC of this thin-walled titanium alloy Ti–B25 pipe in this paper. Three-point bending (3-p-b) was used to test the single edge notched beam (SENB) specimens. The fracture surface of each specimen was examined using a scanning electron microscope (SEM). The discrepancy of yield strength values measured by 3-p-b test and tensile test is 0.6% when the fictitious crack zone △afic equals 2.5 mm, and the fracture toughness KIC of the Ti–B25 pipe is determined to be 83.28 MPa m0.5. This method is a simple and practical way to evaluate the fracture toughness of thin-walled pipe, and it can be used to ensure the safe design and application of titanium alloy pipe.