2731 フェライト焼結磁石の弾性係数に及ぼす配向成形の影響(S28-2 セラミックスおよびセラミックス系複合材料(2),S28 セラミックスおよびセラミックス系複合材料)

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The anisotropies of sound velocities in sintered Sr-ferrites compacted under a magnetic field were investigated by an ultrasonic pulse method. The direction of the applied magnetic field was parallel to that of the compacting pressure. The magnetic field strength was 675kA・m^<-1>, while the green compact was 32mm long, 7mm wide and approximately 7mm high. Compacting pressures of 50MPa and 100MPa were used and three different sintering temperatures were employed, namely 1200℃, 1225℃ and 1250℃. The two directions of the applied sound waves were parallel to the direction of the magnetic field and the compacting pressure, and perpendicular to these directions. The anisotropy of the longitudinal sound velocities was greatest in the orientated sintered compact, the maximum difference between the two velocities was about 8% for such samples. In contrast, the anisotropy of transverse sound velocities was less than 3%. In addition, some anisotropy in the longitudinal sound velocities in the non-orientated sintered compact was detected. This is due to the fact that mechanical alignment of the magnetic particles occurred during the compacting process. The sound velocities were unaffected by the bending strength test. The sound velocity was higher for samples sintering at higher temperatures, but it did not vary with the compacting pressure. This is due to the fact that the sintered density increases with the sintering temperature, but is hardly affected by the compacting pressure. Young's modulus, the shear modulus and Poisson's ratio were estimated from the measured sound velocities using the equations for an isotropic elastic body, since the anisotropy of sound velocities by the orientation forming were 10% or less. In the length direction of the test piece, the greatest rate of change in Young's modulus due to orientation was 7%, while that for the shear modulus was 5% and that for Poisson's ratio was about 10%. In the case of the width and height direction of the test piece, the largest rate of change in the above-mention parameters were approximately 2%, 2% and 16%, respectively.
一般社団法人日本機械学会の論文
2006-09-15

2731 フェライト焼結磁石の弾性係数に及ぼす配向成形の影響(S28-2 セラミックスおよびセラミックス系複合材料(2),S28 セラミックスおよびセラミックス系複合材料)

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