Browsing by Author "Chung Kim Yuen, Steeve"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Open Access
    Influence of Ball Bearing Size on the Flight and Damage Characteristics of Blast-Driven Ball Bearings
    (Multidisciplinary Digital Publishing Institute, 2022-01-21) Langdon, Genevieve S; Qi, Ruixuan; Cloete, Trevor J; Chung Kim Yuen, Steeve
    This paper presents insights into the influence of ball size on the flight characteristics and damage of a ball bearing embedded in a rear detonated cylindrical charge. It includes results from a post-test damage analysis of ball bearings from previously reported experiments. Computational simulations using Ansys Autodyn were used to provide extra information about the velocity variation during flight and the damage sustained by the ball bearings during the blast event. The influence of bearing size (diameter and mass) was investigated using the validated simulation models to extend the dataset beyond the initial experimental work. The peak bearing velocity is influenced by the charge mass to ball bearing mass ratio and the aspect ratio of the charge. Larger ball bearings require extra momentum to accelerate them to higher velocities, but their higher surface area means a greater portion of the explosive charge is involved in transferring kinetic energy to the projectile. Tensile spalling was to be the major damage mechanism within the ball bearings. The charge aspect ratio also influenced the hydrostatic pressure propagation within the ball bearing itself, affecting the location and degree of internal cracking within the bearings. These findings will prove valuable to blast protection engineers considering the effects of embedded projectiles in improvised explosive devices.
  • No Thumbnail Available
    Item
    Open Access
    The response of a structural target to oblique fragment and blast loading
    (2023) Van Der Merwe, Pierre; Chung Kim Yuen, Steeve; Govender, Reuben; Cloete, Trevor
    An improvised explosive device (IED) can be defined as a homemade bomb which is used to target humans and structures [1]. IEDs commonly have dual damaging effects, a high-pressure blast wave that propagates outwards from the point of detonation as well as blast induced fragments. The blast induced fragments include the casing of the IED and added components to increase its lethality and destructive power. Examples of these added components can include but not limited to nails, pieces of glass, nuts, bolts and ball bearings [2]. Fragments, released upon the detonation of the device, are propelled outwards at high velocities and different directions with devastating effects on structures or human lives. Investigating the fragment effect is vital to develop better protection. Two sets of experiments were undertaken in this study, projectile impact experiments and blast experiments. The impact loading of an IED was investigated by performing projectile impact experiments to infer the average impact velocity of the ball bearing during the blast experiments. Impact loading caused by IEDs is complex and often contains numerous fragments. Typical fragments were simplified to a ball bearing propelled using a two-stage gas gun towards a Domex 700 steel target plate. The velocity of the ball bearing and the orientation angle of the target plate was varied. A numerical study was undertaken to further study oblique impact of a ball bearing on a Domex 700 target plate and to investigate experimental uncertainty. Blast experiments were carried out using a cylindrical charge with an embedded ball bearing representing a simplified IED to investigate the response of a target plate experiencing oblique detonation by varying the angle of the explosive. The mass and geometry of the explosive and the placement of the ball bearings were kept constant. For the projectile impact experiments, it was found that an increase in the target plate orientation angle was associated with a decrease in the maximum deflection experienced by the target plate. In contrast, for the blast experiments, the target plate deflection increased as the orientation angle of the explosive charge increased up to 15°. The effect of the orientation angle of the explosive charge decreases for charge orientation angles larger than 15°.
  • Thumbnail Image
    Item
    Open Access
    Towards an Understanding of the Effect of Adding a Foam Core on the Blast Performance of Glass Fibre Reinforced Epoxy Laminate Panels
    (2021-11-23) Gabriel, Sherlyn; von Klemperer, Christopher J; Chung Kim Yuen, Steeve; Langdon, Genevieve S
    This paper presents insights into the blast response of sandwich panels with lightweight foam cores and asymmetric (different thicknesses) glass fibre epoxy face sheets. Viscously damped elastic vibrations were observed in the laminates (no core), while the transient response of the sandwich panels was more complex, especially after the peak displacement was observed. The post-peak residual oscillations in the sandwich panels were larger and did not decay as significantly with time when compared to the equivalent mass laminate panel test. Delamination was the predominant mode of failure on the thinner facesheet side of the sandwich panel, whereas cracking and matrix failure were more prominent on the thicker side (which was exposed to the blast). The type of constituent materials used and testing conditions, including the clamping method, influenced the resulting failure modes observed. A probable sequence of damage in the sandwich panels was proposed, based on the transient displacement measurements, a post-test failure analysis, and consideration of the stress wave propagation through the multilayered, multimaterial structure. This work demonstrates the need for detailed understanding of the transient behaviour of multilayered structures with significant elastic energy capacity and a wide range of possible damage mechanisms. The work should prove valuable to structural engineers and designers considering the deployment of foam-core sandwich panels or fibre reinforced polymer laminates in applications when air-blast loading may pose a credible threat.