Analysis for the residual prestress of composite barrel for railgun with tension winding

Based on the elastic theory of cylindrical shells and the theory of composite laminates,a prediction model for the residual prestress of the simplified round composite barrel for railgun is established.Only the fibre pretension is considered in this model.A three dimensional numerical simulation for the residual prestress in the railgun barrel is carried out,by combining the temperature differential method with the element birth and death technology.The results obtained by the two methods are compared.It reveals that the distribution trends of residual prestress are consistent.And the difference for residual prestress in the filament wound composite housing of barrel is relatively small.The same finite element method is used to analysis the residual prestress in the non-simplified composite barrels for railgun,which are under different control modes of winding tension.The results mean that the residual prestress in barrel will increase while the taper coefficient for winding is decreasing.Therefore,the sealing performance in bore is improved,but the strength of the filament wound composite housing drops.In addition,the axial and circumferential residual prestress in the filament wound composite housing with constant torque winding are close to the ones in iso-stress design for barrel.

Secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams

An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand.A numerical model is developed and used to predict the secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams.The model change interaction,which can deactivate and reactivate the elements for simulating the removal and reproduction of parts of the model,is used to reproduce the secondary anchorage of fractured strand.The numerical model is verified by experimental results.Results shows that the fractured strand can be reanchored in concrete through the secondary anchorage,and the secondary transfer length of fractured strand with the diameter of 15.2 mm is 1133 mm.The residual prestress of fractured strand increases gradually in the secondary transfer length,and tends to be a constant beyond it.When the fractured strand is fully anchored in concrete,a minor prestress loss will appear,and the average prestress loss is 2.28%in the present study.