Determination of Elastic Constants Required for Application of Fracture Mechanics to Ceramics

  • J. B. WachtmanJr.
Part of the Fracture Mechanics of Ceramics book series (FMOC, volume 1)


Elastic properties enter into fracture mechanics most simply in the case of plane stress in an elastically isotropic body for which EG1 = ПК1 2 where G1 is the energy release rate, K1 is the stress intensity factor, and E is Young’s modulus. For an elastically orthotropic body the sajne result holds provided 1/E is replaced by (s11s22/2)1/2[s22/s11)1/2 + (2s12+s66)/2s11]1/2 where the sij are the single crystal elastic compliances. These equations may be used to establish a Griffith type fracture criterion by setting G1 = G1C = 2γf where γf is the fracture surface energy. Elastic moduli or compliances can usually be determined more accurately than either G1C or γf. Methods for their determination by resonance or by ultrasonic wave propagation are briefly described. Values of the elastic factors in the energy release rates for material in polycrystalline form are compared with values for materials in single crystal form for various orthotropic orientations of cracks to indicate the effectiveness of single crystal elastic isotropy in causing variation in the fracture condition. This theory is shown to predict an anisotropic fracture criterion for certain crystal planes.


Stress Intensity Factor Acoustic Emission Elastic Constant Energy Release Rate Barium Titanate 


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Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • J. B. WachtmanJr.
    • 1
  1. 1.National Bureau of StandardsUSA

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