R. S. Birch

An Experimental Study on the Lateral Impact of Fully Clamped Mild Steel Pipes

This report presents some experimental data that were recorded from 130 impact tests on mild steel pipes in two drop hammer rigs. The pipes were fully clamped across a span which was ten times the corresponding outside pipe diameters which lie between 22 and 324 mm. All of the pipes except five had wall thicknesses of 2 mm approximately and were impacted laterally by a rigid wedge indenter at the mid span, one-quarter span or near to a support. The impact velocities ranged up to 14 m/s and caused various failure modes. Some comparisons between two sets of experimental results indicate that the laws of geometrically similar scaling are almost satisfied over a scale range of approximately five.

Measurement of Impact Loads using a Laser Doppler Velocimeter

The design and selection of transducers is an important consideration for the measurement of impact loads. This paper examines a load-measuring transducer based on a non-contact laser Doppler principle. An experimental study assesses the deformations and velocities obtained using a laser Doppler velocimeter and compares the mean and peak loads with those recorded by an accelerometer and a load cell. The paper concludes that this device is a valuable tool in the structural impact research field.

Influence of Internal Pressure on the Impact Behavior of Steel Pipelines

This article presents some experimental data recorded from 54 impact tests on pressurized mild steel pipes. The pipes were fully clamped across a span which was ten times the outside pipe diameter of 60 mm. The pipes had a wall thickness of 1.70 mm and were impacted laterally by a rigid wedge indenter at the mid-span and one-quarter-span positions. The impact velocities ranged up to 13.6 m/s and caused large inelastic indentations for the lower values and at higher values a loss of integrity which could occur underneath the indenter and/or at an end support. The critical values for the two failure energies were obtained for a range of internal gas pressures.

Dynamic and static axial crushing of axially stiffened cylindrical shells

Abstract The axial impact of cylindrical tubes, which incorporate axial stiffeners, is examined in this paper. For comparison purposes, the effect of static loading is also studied. An examination is made into the influence of stiffener depth (T), number of stiffeners (N) and the effect of placing the stiffeners externally or internally. The experimental results on mild steel specimens show that there are considerable differences between the static and dynamic modes of failure, and that an optimum T/D ratio may exist for a given value of N.

Dynamic and Static Axial Crushing of Axially Stiffened Square Tubes

The axial impact of thin-walled tubes with square cross-sections, which incorporate axial stiffeners, is studied in this paper. An examination is made into the influences of stiffener depth (T), number of stiffeners (N) and the effect of external or internal stiffening. The experimental results on mild steel specimens of side width c suggest, for a given impact energy, that the permanent axial displacements are not reduced significantly by the addition of stiffeners unless T/c exceeds a certain value.

Low-Velocity Perforation of Mild Steel Rectangular Plates With Projectiles Having Different Shaped Impact Faces

This article studies the perforation of mild steel circular plates struck normally by cylindrical projectiles having blunt, hemispherical, and conical impact faces. Experimental results are obtained using a drop hammer rig for the perforation of 2-8 mm thick plates struck by projectiles weighing between 1.75 kg and 176 kg and traveling up to about 12 mis. The impact positions are at several radial locations across a plate, and it turns out that the perforation energy decreases as the impact location is moved away from a plate center toward the support. It transpires that the projectiles with hemispherical and blunt impact faces require the largest and the smallest impact perforation energies, respectively. Comparisons are made between the experimental results for the perforation energies and the predictions of several empirical equations. Design calculations for the impact perforation of plates could be undertaken using projectiles with blunt impact faces, which would provide a lower bound on the perforation energy of projectiles having hemispherical or conical impact faces, at least within the range of the parameters studied.

Performance Assessment of an Impact Rig

A recent upgrading of a drop hammer rig was carried out and a series of calibration tests established the energy losses in the existing anvil. Both the test results and the mathematical modelling showed that significant energy losses would occur at high impact loads. An alternative anvil design considerably reduced the energy losses and improved the performance of the drop hammer rig.

Dynamic failure of structural joint systems

Transportation structures rely heavily on the use of structural jointing based on fixing systems such as bolting or welding. Experimental work in this paper offers some insight into the differences between the static and dynamic failure of some joint configurations made using these methods. The main emphasis of this paper is on the examination of a simple dynamic failure of a spot welded lap joint in thin sheet materials that are used extensively in vehicle construction. A comparison is made with similar bolted type lap joints.

Design of a pulse generator and shock tube for measuring hearing protector attenuation of high-amplitude impulsive noise

Abstract The effectiveness of hearing protectors against high amplitude impulse noise levels remains the subject of research with objective testing techniques using acoustic test fixtures offering the only realistic method of providing rapid performance data for protector design and qualification. The work presented in this paper examines a prototype test method based on a shock tube and acoustic test fixture for the evaluation of protectors against high-level impulsive noise where established real ear attenuation at threshold methods would be impractical to apply. The results show that the system is capable of producing controlled repeatable high amplitude pressure pulses of variable duration for testing hearing protection devices in a grazing wave type test. A series of pilot tests illustrate how the system can have a sufficient self-insertion loss to reject flanking noise and allow the measurement of protector attenuations of up to 45 dB with little corruption from flanking noise.

On the Scaling of Low-Velocity Perforation of Mild Steel Plates

Experimental results are reported for the perforation of geometrically similar fully clamped circular and square mild steel plates struck transversely by cylindrical projectiles having blunt, conical, and hemispherical noses. The striking masses are much heavier than the corresponding plate mass and travel with initial impact velocities up to about 12m∕s. The blunt projectiles perforate the plating easiest, while the hemispherical-nosed ones require the greatest energy. The perforation energy of a conical-nosed projectile is somewhat less than that for a hemispherical-nosed one. The data are used to explore the validity of the geometrically similar scaling laws over a geometric scale range of 4. The experimental results are compared to the empirical equations for the impact perforation of plates and with theoretical rigid-plastic predictions for the large ductile deformation behavior of those test specimens, which did not suffer cracking or perforation. The experimental results satisfy the requirements of geometrically similar scaling and some simple equations are presented, which are useful for design purposes.