الفهرس 
arabic summaryOnly 14 pages are availabe for public view
 |  | from | 115 |  |  |
| | | from | 115 | | |
Abstract
In the first part of the present work, new equations have been derived to calculate the residual stresses in elastic bars and tubes by measuring only the axial strains due to removal (or cutting) of successive layers. Two cases have been considered, namely outside- and inside-cutting. The obtained equations are used for calculating residual stresses using published results of measured strains for bored steel bars. The residual stresses were also calculated using sach’s boring method for comparison.
Then an analytical study is carried out for the determination of the residual stresses in tubes made of viscoelastic material. In this study, equations which were obtained in the first part have been adopted. In order to make these equations applicable for measuring residual stresses in tubes made of viscoelastic material, a three-parameter model is used to represent a real viscoelastic material. The analogy between the governing field equations of elasticity and Laplace transforms of the basic viscoelastic field equations known as the correspondence principle is applied to obtain equations for determining residual stresses in the viscoelastic tubes. Two cases have been considered, namely, inside and outside cutting, expressions for determining residual stresses in each case have been obtained.
Experimental determination of the viscoelastic coefficients contained in the stress-strain relations of the chosen three parameter model is obtained from a torsional bcreep test and a thin walled PVC tubular specimens. Finally experimental measurements of strains on the outer surfaces of PVC tubes with different sizes due to inner surface layers removal have been carried out. Form the experimental measurements residusal in these PVC tubes have been determined using the obtained equations for viscoelastic materisal. For comparison the residual stresses have been determined assuming the tube material to be elastic. The results obtained assuming the material to be elastic show great deviations from the viscoelastic results. This means that the assumption of elasticity of the PVC tubes in determination of residual stresses is not justified.