SOME ADVANCES IN STUDIES OF THE NEUTRAL AXIS OF BEAM^1)

The history for the concept of beam neutral axis and its positioning methods is reviewed on the premise of reflecting the recent progresses of new materials and microbeam structures. By comparing the description methods of strain field of beam structure, and demonstrating the deviation of the neutral axis and the non-uniqueness of zero stress axis, we reveal that the neutral axis of elastic homogeneous beam should pass through the centroid of section, however the neutral axes of non-linear elastic beam, double modulus beam, elasto-plastic beam, superposition beam and laminated beam may deviate from the centroid of section. These insights are helpful for solving the related problems in engineering reasonably and effectively with a correct understanding of the neutral axis of beams.