SYMPOSIA PAPER Published: 01 January 1986

Investigation and Application of the One-Point-Bend Impact Test


This paper investigates a dynamic fracture test that produces smoothly varying stress intensity histories of controlled amplitude and duration. A test configuration has been adopted in which a simple edge-cracked specimen is loaded in bending by impacting it at the midsection without supporting it at the outer edges. The stress intensity history is measured by a strain gage near the crack tip and has approximately a sinusoidal time dependence.

The dependence of stress intensity amplitude and duration on the impact velocity and on the specimen material and dimensions has been determined both analytically and experimentally. The limit on the specimen aspect ratio to obtain a smooth stress intensity history controlled only by the first mode of vibration of the specimen has also been established. Stress intensity pulses of durations varying between 90 and 500 μs can be readily achieved, and the maximum amplitude can be independently adjusted over an order of magnitude (20 to 200 MPa m1/2).

The new experimental procedure has been used to measure the dynamic fracture toughness of 4340 steel (HRC 50) at three loading rates. Comparison of the dynamic results with the value of the static toughness indicates little strain-rate sensitivity of the fracture toughness of 4340 steel in the range of loading rates investigated (quasi-static to 3 × 106 MPa m1/2 s-1).

Author Information

Giovanola, JH
SRI International, Menlo Park, CA
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Developed by Committee: E08
Pages: 307–328
DOI: 10.1520/STP17404S
ISBN-EB: 978-0-8031-4972-4
ISBN-13: 978-0-8031-0472-3