Research On Saint-venant's Torsion Of Composite Circular Shafts

Circular shafts under torsion are widely used in engineering, especially composite shafts find also increasing applications to raise the undergoing-load level of the shafts. On the other hand, these shafts caintain more or less some defects, such as holes, cracks or inclusions. Thus, it is of not only theoretical interest but also practical importance to study the torsion of circular shafts containing holes or inclusions.In the present work we propose a straightforward and concise approach to analyze the problem of composite shaft in torsion based on complex variable method. Below are the main contents of this work: following the brief introduction given in Chapter 1, basic field equations of Muskhelishvili are outlined in Chapter 2. Chapter 3-5 are the main contributions of the work which address the Saint-Venant's torsion of a circular shaft containing multiple holes/cracks/inclusions. A semi-analytical solution for the shear stresses and torsional rigidity are first given. Then, the expression for the stress intensity factors of cracks is also derived. Finally, several numerical examples are presented to discuss the effects of the geometry parameters or array-types of inclusions/holes/cracks on the fields of stresses.In Chapter 6, we studied the Saint-Venant's torsion of a piezoelectric circular shaft containing multiple circular holes. The stress field in the piezoelectric circular shaft is solved base on the similar approach adopted in the above Chapters, combined with the consideration of the material characteristic of the rightwards spiral crystals. Then, the distribution of surface charge densities is also derived according to the equivalent principle of electrie field.Finally, this wok is concluded and future works are proposed in Chapter 7.