セラミックスの超塑性特性の三点曲げ試験による評価法 : 曲げ試験結果と引張試験結果の比較

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The three-point bending deformation of a beam under a constant deflection-rate has been analyzed using the constitutive equation of superplasticity. Then the bend test and a tension test of a yttria-stabilized tetragonal ZrO_2 polycrystal (Y-TZP) in which the occurrence of superplasticity has been confirmed have been carried out at various deflection-rates and strain-rates at different temperatures. Results of the bend test have been compared with those of the tension test. Outer-fiber stress (σ_xc)_s and strain-rate (ε_xc)_s at the center of the beam have been calculated from measured values of bending force P_c, deflection-rate υ_c and deflection-rate sensitivity index m' defined as δln P_c/δln υ_c The strain-rate sensitivity index m obtained from the slope of the log-log plot of (σ_xc)_s and (ε_xc)_s agrees well with the m-value obtained from the tension test within the range of the present experiment. An activation energy of the deformation Q obtained from ln P_C^<1/m'> vs. 1/T or ln υ_C vs. 1/T plot in the bend test corresponds well with the Q-value obtained from the tension test, where T is temperature. A relatively rapid decrease in Young's modulus and an abrupt increase in deflection to fracture with an elevation in temperature are thought to be an indication of the onset of superplasticity. We can conclude from these results that the three-point bend test is a good method to evaluate superplastic properties in ceramics of which tension test is generally not so easy.
一般社団法人日本機械学会の論文
1990-08-25

セラミックスの超塑性特性の三点曲げ試験による評価法 : 曲げ試験結果と引張試験結果の比較

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