Single Impact Damage Research Articles

Computer Modeling for a Generalized Approach to Measure Impact Damage

This paper describes a generalized and rational computational approach to qualitatively measure the level of damage generated by projectiles impacting a system of bumper plates. A single impact damage index (SIDI) model is proposed based on results from numerical simulations using a hydrocode. The model combines the depth of penetration and the size of the holes. A sensitivity study demonstrated that the SIDI is very useful to make relative comparisons between a wide range of impact configurations, high impact velocities, material densities, and projectile shapes and sizes. Additional simulations with two neighbor impacts were conducted to compute a combined damage index and study its sensitivity to neighboring distances. An artificial neural network was developed to rapidly estimate the SIDI for numerous impact configurations and velocities. The approach can be coupled with other methodologies to assess larger-scale damage involving multiple impacts at high velocities.

Loose-part damage

Experiments and analytical methods were used to develop models that describe loose part impact damage. Single impact damage volume was characterized as a function of impact energy and contact shape. The deformation volume for multiple, overlapping impacts was used to define work hardening. Integrated impact damage experiments were conducted at representative pressurized water reactor steam generator inlet flow velocity using a target plate that represented a section of a steam generator tube sheet. Data from the integrated impact tests were used to develop an empirical relationship for tube end open diameter reduction as a function of loose part energy and accumulated impact density. Monte-Carlo programs were developed to investigate the tube sheet impact density distribution and the penetration of tube end welds. The results provide insight with respect to single and multiple impact damage mechanisms and methods that can be used to predict steam generator tube sheet accumulated impact damage.

Single particle impact damage of fused silica

Single-impact damage of fused silica by spherical and conical tungsten carbide (WC) projectiles of velocities up to 200 m sec−1 has been investigated with a high-speed framing camera photographing at a rate of up to 1.7×106 frames per second. For spherical particles the Hertzian cone cracks, which for higher impact velocities are accompanied by median and radial cracks, form during the loading part of the impact; some growth of all these cracks also occurs during unloading. With the conical particles the Hertzian cone cracks do not form; only radial and median cracks form during the loading; in this case both radial and median cracks grow during the unloading. In both cases “lateral” cracks form during unloading. From these experiments values of the static equivalent of the dynamic stress-intensity factor for high-velocity cracks are also obtained; these are found to be considerably lower than those obtained from quasi-static indentation experiments. Finally, the extent of the damage produced by a single impact has been discussed.