Coupled discrete/continuum simulations of the impact of granular slugs with clamped beams: Stand-off effects

Goel, A.; Uth, T.; Liu, Tao; Wadley, H.N.G.; Deshpande, V.S.

doi:10.1016/j.mechmat.2017.03.001

Cited by 4 publications

(5 citation statements)

References 33 publications

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“…4b in a manner similar to that of Goel et al [40]. Thus, following Goel et al [40], it suffices to approximate as where is the time taken for the piston to ramp up to its final velocity .…”

Section: 2mentioning

confidence: 97%

“…The particle contact model was defined by four parameters , , and . While Liu et al [2] demonstrated that these parameters do not affect the interaction response of the granular slug impacting beams, Goel et al [40] demonstrated that strongly influence the evolution of the granular slug as it emerges from the launcher. It was therefore necessary to calibrate , as discussed below, while maintaining the other parameters fixed at reference values based on previous studies; see for example Refs.…”

Section: 1mentioning

confidence: 99%

“…6b that resulted in the lengthening of the slug during free-flight. Goel et al [40] demonstrated that this velocity gradient is strongly dependent on and hence needed to be calibrated independently. This was performed as follows.…”

Section: 1mentioning

confidence: 99%

“…Generation of the sand slug To accurately capture the state of the sand slug during its free-flight and thereby its state just prior to impact, it is necessary to explicitly model the ejection of the sand slug from the launcher as described in Goel et al [40]. In order to simplify the numerical calculations, the impact of the projectile against the piston and the deformation of the piston were not directly modelled.…”

Section: 2mentioning

confidence: 99%

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Effect of surface properties on momentum transfer to targets impacted by high-velocity sand slugs

Goel

Uth

Wadley

et al. 2017

International Journal of Impact Engineering

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The response of dry and water saturated sand slugs impacting normally oriented and inclined rigid-stationary targets with four different surface coatings is measured with an emphasis on the quantification of the momentum transmitted from the slugs into the targets. The targets were coated with Alumina, PTFE, Aluminium or sandpaper layers in order to investigate the effect of varying surface hardness and surface roughness. In all the cases, the fraction of the slug momentum transferred into the target was equal for dry and water saturated sand slugs and also independent of the slug velocity over the range that is investigated here. For normal impacts, the surface coatings had no measurable influence on the momentum transfer into the targets and this was attributed to the symmetry of the impact event. However, the break of symmetry in the inclined impact cases resulted in two non-zero components of the net transmitted momentum into the targets and a strong influence of the surface coatings. This is attributed to friction between the sand particles and the target surface with the resultant transmitted momentum increasing in the order Alumina to PTFE to Aluminium to sandpaper surface coatings. In all cases, the transmitted momentum was less than the corresponding value under normal impact. Coupled discrete particle/ Lagrangian simulations of these experiments with the sand particles modelled as spheres captured the normal impact measurements with a high degree of fidelity. However, the simulations underestimated the transmitted momentum for the inclined impacts especially for the rough surface coatings such as the sandpaper: increasing the friction coefficient between the particles and the target in the simulations did not improve the predictions. We demonstrate that this discrepancy is due to the spherical particle assumption: in the experiments the sand particles are sub-spherical and this reduces the tendency of particles to roll on the target surface and thereby increases frictional interactions. Increasing the radius of gyration of particles decreased the discrepancy between the measurements and the predictions but yet could not accurately predict all components of the transmitted momentum. Most numerical calculations tend to use spherical particles to represent the impacting granular media. However, this study demonstrates the need to appropriately parameterise particle shape in such discrete particle calculations to accurately capture the granular media/ structure interactions.

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“…4b in a manner similar to that of Goel et al [40]. Thus, following Goel et al [40], it suffices to approximate as where is the time taken for the piston to ramp up to its final velocity .…”

Section: 2mentioning

confidence: 97%

Section: 1mentioning

confidence: 99%

Section: 1mentioning

confidence: 99%

Section: 2mentioning

confidence: 99%

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Effect of surface properties on momentum transfer to targets impacted by high-velocity sand slugs

Goel

Uth

Wadley

et al. 2017

International Journal of Impact Engineering

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“…These included increasing the standoff distance by raising the height of a vehicle above the surface. This reduces the applied impulse as the sand density decreases as it expands both axially and laterally, and as air drag decelerates the soil particles before they reach the structure [13,54,78,97]. The use of a V-shaped hull has also been shown to reduce the fraction of momentum that is transferred to an impacted surface [12,[71][72][73][74][75].…”

Section: Introductionmentioning

confidence: 99%

Impulse Mitigation of Structures Impacted by Granular Media

Kyner¹

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as well as technical interest [18-20]. The impact of the granular media on a structure applies a net force for the duration of the loading. This change in momentum, ∆ = ∆ , results in a total impulse, I, applied to the structure with a specific impulse, Io, that represents the impulse per unit area on the impacted surface. The need for robust structural designs has led to the Chapter 1. Chapter 3. High intensity impulsive loading by explosively accelerated granular matter

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