Rectangular Pressure Pulse Research Articles

Dynamic response of axially constrained plastic beams to blast loads

The analysis of a rigid, perfectly plastic rectangular beam with constrained ends subjected to a rectangular pressure pulse of finite duration is presented. Closed form expressions are obtained for the maximum permanent deflection for both simply supported and clamped boundary conditions. These expressions are valid for the full dynamic range from pseudo-static step load to high pressure impulsive loading. The results indicate that the response is strongly influenced by geometry changes even for small deflections. Finally the response expressions are combined to form isoresponse relationships which when plotted form isoresponse curves of direct engineering use.

Radial and Axial Variations in Transient Pressure Waves Transmitted Through Liquid Transmission Lines

An implicit factorization method has been developed for solving numerically the complete two-dimensional Navier-Stokes and continuity equations for pressure transients in a slightly compressible viscous liquid contained in a rigid pipe. Two problems have been analyzed: (1) The stopping of a steady Poiseuille flow by closure of a valve, and (2), the initiation of a nearly rectangular pressure pulse at the end of the pipe. In problem (1), radial as well as axial pressure variations were found; nearly periodic damped waves exist at the centerline and at the wall, and are approximately 180 deg out of phase. Essentially plane waves are found for problem (2), regardless of whether the fluid is flowing or not, provided that the initial pulse magnitude is not too large; the results show that the viscous effects are concentrated in a thin boundary layer.

Axial dynamic compression of tubular metallic crushers

In studying the dynamic strength of structures and materials, the load is usually placed on test objects by rectangular or trapezoidal pressure pulses. In addition, their amplitude and duration vary over wide ranges. Such a loading pressure pulse can be obtained with impact loading through a special damper, for which the dependence of the force on the magnitude of compression has a region where the compression force is constant. Polystyrene foam is an example of a material used for such a damper [i, 3]. However, widespread use of polystyrene foam for these purposes is hampered by the instability of its strength characteristics, which decrease the reproducibility of rest results, and comparatively low strength, which limits the level of loads that are created. In this respect, tubular crushers under axial compression have more universal possibilities.

Efficient Pulse Shapes to Plastically Deform Beams

The transient motion of a simply supported, rigid-plastic beam in response to uniformly distributed pressure pulses of arbitrary shape is considered. The objective is to determine the pulse shape that will maximize the residual deflection at the center of the beam subject to certain load constraints. Results for two constraints are determined. When a specified impulse is applied to the beam an impulsive load causes the largest deflection. When a specified amount of work is done on the beam the deflection is maximized by limiting the maximum pressure so only the static collapse deformation mode occurs. This result is independent of pulse shape. These conclusions are supported by comparisons of the deformation due to triangular, exponentially decreasing and double rectangular pressure pulses.

An Approximate Rigid-Plastic Analysis of Shell Intersections Loaded Dynamically

An approximate rigid-plastic method of analysis which may be used in order to estimate the behavior of various shell intersections subjected to large dynamic loads is presented herein. In particular, the two common cases of cylindrical nozzles intersecting either spherical or cylindrical shells are considered in some detail. The maximum permanent radial deflections of these two structures which arise from rectangular pressure pulses are presented for various geometrical parameters.

Finite deflections of a simply supported rigid-plastic annular plate loaded dynamically

A theoretical analysis is presented for the dynamic behavior of a simply supported rigid, perfectly plastic annular plate subjected to a rectangular pressure pulse. It is shown that this theory, which considers the simultaneous influence of membrane forces and bending moments, predicts final deformations which are considerably smaller than those given by the corresponding bending theory even when maximum deflections only of the order of the plate thickness are permitted. It is believed that this theoretical analysis could be developed further in order to describe the behavior of plates having other support conditions and different dynamic loading characteristics.

Shock-Wave Propagation in Solid and Compactible Media

The equations of motion for a hydrodynamic solid are studied for a pressure-density relation appropriate to pulse propagation in solid and compactible media. After collapse of the compactible material, the pressure-density relation is assumed to have the form P = A[(ρ/ρ0)γ−1]. A semianalytical method of solution is used on the resulting one-dimensional set of nonlinear partial differential equations. By using characteristic variables, the nonlinear differential equations are transformed to a set of linear partial differential equations whose solution is then obtained numerically. Applications are made to aluminum, for which the constants A and γ are known, and to compactible materials using an assumed value for γ. This investigation serves to define the various types of phenomena that can occur in a semi-infinite compactible material that is shocked by a rectangular pressure pulse. In particular, the analysis shows that the shock-wave penetration depth at the end of the first shock-rarefaction interaction has a minimum when regarded as a function of the material porosity.

Dynamic plastic deformations of simply-supported square plates

I n this paper an analysis is given within the framework of thin plate theory of the problem of a simply-supported, square plate subjected to a uniformly-distributed rectangular pressure pulse. All effects due to elastic strain, work-hardening and strain-rate are neglected, although some approximate account of the two latter may be made. To simplify the analysis further, Johansen's yield criterion is adopted as an approximation to Tresca's. The most important results concern the maximum displacement and the total time of motion. Errors in these quantities from approximating Tresca's yield criterion are estimated to be about five per cent.