Detonation loading of tubes in the modified shear wave speed regime
We performed experiments and numerical simulations on a thin-wall aluminum tube with internal gaseous detonation loading in the modified shear wave speed regime. Strain gauges were used to determine the time-dependent hoop strain on the surface of the tube. The experimental results were compared with analytical models and numerical simulations with explicit finite element computation treating the detonation as a traveling load. Hoop strain amplification factors (defined as the ratio of the dynamic strain to the equivalent static strain) close to two were obtained both in the present experiments and simulations. No resonance phenomena in the hoop strain were found in either experiments or simulations. Computations reveal the existence of a resonance in the shear strain.
Dynamic Response of a Tube Under Moving Pressure
The dynamic response of a thin-walled cylindrical tube under internal moving pressure is analyzed. The investigation contains both the steady state and transient responses. The equations of motion to be used include the terms resulting from the shear deformation and the rotatory inertia. An analytical method by means of the Fourier transform is used for the steady state response, whereas a numerical method of characteristics is used to solve the hyperbolic partial differential equation for the transient response. Numerical examples give the transient responses of the radial deflection at two stations.
Prophets praying for, or preying on people’s faith: A reflection on prophetic ministry in the South African context
In mainline churches, the ministry of prophecy or the prophetic ministry involves the proclamation of the gospel. This, in turn, is related to the every-believer ministry. However, there is now a resurgence of the prophetic ministry as a special office as evidenced by the establishment of neo-prophetic churches. This article argues that neo-prophetic churches are tapping into people’s longing for the fresh divine word to speak directly into their personal situations. The article also probes whether neo-prophets in the prophetic activities are not also preying on people’s faith.