铝电解用阴极炭块单轴压缩的声发射特性及破坏形态

Acoustic emission characteristics of cathode carbon blocks under uniaxial compression and its fracture morphology

对铝电解用三种阴极炭块试样进行了单轴压缩声发射试验,研究了不同阴极炭块在应力时程阶段的声发射特性。试验结果表明:在阴极炭块压实阶段,HC35试件采集到了能量较高的声发射振铃数,这是由于HC35试件内部的微裂纹较多;在弹性阶段,HC35和HC100试件出现了较强的声发射信号,振铃数较多,而SMH试件较少,说明SMH阴极炭块试件内部微裂纹较HC35和HC100试件要少,且闭合的微裂纹发展更稳定;在塑性阶段,当达到峰值应力时,三种阴极炭块的声发射信号参数均达到极大值;进入破坏发展阶段,试件发生宏观破裂,且宏观裂隙间的相互作用仍会持续产生一定的声发射信号。从而可以以声发射信号参数的跌落为判据,辨识阴极炭块是否已经破坏。接着数值模拟研究了单轴压缩时阴极炭块内裂纹由萌生、扩展直至失稳断裂全过程。数值模拟结果与阴极炭块的CT层析成像结果吻合很好,表明数值模拟能够再现阴极炭块的变形破坏形态,可以用于预测阴极炭块裂纹的动态演变过程。

Acoustic emission experiments were conducted on three types of cathode carbon blocks which were under uniaxial compression. And acoustic emission properties of different cathode carbon blocks during the time - stress history were studied. Results showed that acoustic emission counts with high energy were accumulated in sample HC35 at compaction stage, which was caused by much more cracks distributing in HC35 ; And at elastic stage, more a- coustic emission counts were accumulated in sample HC35 and HC100 than in sample SMH,which meant that less cracks distributed in SMH than in HC35 and HC100, and crack growth was the most stable in sample SMH; During the plastic stage, acoustic emission parameters reached the maximum val- ues as the stress climbed to the highest value ; At fracture stage, macroscopic fracture appeared in the three samples, and still certain acoustic emission sig- nals could be obtained because of the interaction of cracks. As a result ,the fracture stage of cathode carbon blocks could be identified by the decline of a- coustic emission parameter values. At the meanwhile, numerical simulation was conducted to study the fracture process of cathode carbon blocks which was under uniaxial compression. And the numerical results agreed well with CT image experimental results. So numerical methods could be used to represent fracture process and fracture morphology of cathode carbon blocks.