Simple and accurate fracture toughness testing （简单和准确的断裂韧度测试）.pdfVIP

Simple and accurate fracture toughness testing methods for pyrolytic carbon/graphite composites used in heart-valve prostheses J. J. Kruzic,1 S. J. Kuskowski,2 R. O. Ritchie3 1Department of Mechanical Engineering, Oregon State University, Corvallis, Oregon 97331 2Medical CV, Incorporated, Inver Grove Heights, Minnesota 55077 3Materials Sciences Division, Lawrence Berkeley National Laboratory, and Department of Materials Science and Engineering, University of California, Berkeley, California 94720 Received 4 January 2005; revised 23 February 2005; accepted 24 February 2005 Published online 22 June 2005 in Wiley InterScience (). DOI: 10.1002/jbm.a.30380 Abstract: The fracture toughness is a critical material prop- toughness values of 1.46 0.13 and 1.35 0.09 MPam erty for the pyrolytic carbon materials used in mechanical were obtained for the pyrolytic carbon-coated graphite ma- heart-valve prostheses; however, making accurate tough- terials, using precracked and razor micronotched specimens, ness measurements has traditionally been problematic due respectively. The difference between these mean values to difficulties in fatigue precracking specimens. In this work, proved to be statistically insignificant, and these values are a simple, effective, and reliable precracking method is pre- in general agreement with published fracture toughness sented where a sharp precrack is “popped in” from a razor results obtained using fatigue precracked specimens. © 2005 micronotch, which allows significant savings of time and Wiley Periodicals, Inc. J Biomed Mater Res 74A: 461–464, materials relative to fatigue precracking methods. It is fur- 2005 ther shown that equivalent results may be obtained using razor micronotched specimens directly without precracking, Key words: pyrolytic carbon; fracture; fatigue; micronotch; provi