Through analyzing tangential strain of three areas, it found out that neutral layer of strain move entad, but the displacement is not equal in each radial section.

• 在对三个区域的切向应变作了较为详细的分析讨论后,提出了应变中性层虽向内移动,但其内移量在各径向剖面内是不相等的这一说法。