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Effect of Polyurea on Dynamic Response of Steel Plates Experimental Investigation Introduction The dynamic behavior of circular plates, with deflections.

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Presentation on theme: "Effect of Polyurea on Dynamic Response of Steel Plates Experimental Investigation Introduction The dynamic behavior of circular plates, with deflections."— Presentation transcript:

1 Effect of Polyurea on Dynamic Response of Steel Plates Experimental Investigation Introduction The dynamic behavior of circular plates, with deflections in the range where both bending moments and membrane forces are important, is investigated experimentally and numerically. This type of loading is typical in high strain-rate events such as impact- and blast-loading leading to catastrophic results. Therefore there is ongoing need to improve the energy absorbing characteristics of steel plates. One of the most convenient ways of enhancing the energy absorption of the steel plates and improving the resistance to fracture in dynamic events is to use polyurea. Therefore, the effect of polyurea on the fracture mode and energy absorption characteristics of steel plates is studied, focusing on the effect of the relative location of steel and polyurea layers with respect to the loading direction. Nature of the Problem The polyurea can have a significant impact on the mechanical response of the steel plate under dynamic impulsive loading both in terms of failure resistance and energy absorbing capacity, if used appropriately as backing of the plate. This experimental observation has been also proved computationally using detailed finite element models employing very accurate constitutive models for DH-36 steel and polyurea. Conclusions and Results In this work we addressed the effect of the polyurea on the dynamic behavior of steel plates. The failure process of the steel plates can be captured with the new experimental setup leading to a better insight into the failure mechanisms of the steel plates. Summary & Future Directions Student: Mahmoud Reza Amini Advisor: Prof. Sia Nemat-Nasser Dynamic Impulsive Loading of Steel Plate Enhance the Energy Absorbing Characteristics Effect of Polyurea on Steel Plate Dynamic Response Polyurea-Steel Layers Design Configuration Polyurea in Front Polyurea in Back No Polyurea = steel plate= polyurea= impact side subject Problem Experimental Investigation Computational Evaluation Effect of Polyurea on Steel Plate Fracture 3-inch Hopkinson Bar Ultra high speed camera, Imacon 200 LS-DYNA (FEM) User-Defined Materials Constitutive Models Fracture Mode and Severity, Shear Band and Necking Topics of Investigations 3-inch Steel Bar Al 7075 Cylinder Steel Confinement Polyurethane DH-36 Steel Plate 17-4 pH Steel Ring V0V0 Projectile Gas Gun Barrel Projectile Polyurethane Confinement Steel Bar V0V0 Severe Failure Slight Failure No Failure Top ViewSide View Experiments Without Ring, Cylinder #1 Energy per Thickness > (J/cm) Fracture Energy per Thickness > (J/cm) Fracture Experiments With Ring, Cylinder #1 Experiments Without Ring, Cylinder #2 Without Polyurea Backing With Polyurea Backing Impact Velocity = m/s Input Energy = J Thickness = cm Energy/Thickness = J/cm Impact Velocity = m/s Input Energy = J Thickness = cm Energy/Thickness = J/cm No FailureSevere Failure Without Polyurea Fronting With Polyurea Fronting Impact Velocity = m/s Input Energy = J Thickness = cm Energy/Thickness = J/cm Impact Velocity = m/s Input Energy = J Thickness = cm Energy/Thickness = J/cm Severe Failure Experimental Setup FlatDish + PU/FrontedFlat + PU/Backed Cylinder Plate Cylinder Plate Polyurea Polyurethane Dish Cylinder Plate Polyurethane Four different configurations of steel plate and polyurea layers Experimental Results At large deformations (deflection/thickness > 10) the membrane effect is predominant. Thus the behavior of the steel plate is proportional to the inverse of the thickness DH-36 Steel Plate 3 outer diameter M = 90~95 g t = 0.038~0.041 The most important experimental quantities include: Imparted energy (mass of projectile, ring and plate and projectile velocity) Steel plate thickness Polyurea location if used Plates behave as simply-supported Failure can be qualitatively categorized as shown: Necking and shearbanding are typical mechan- isms of failure of the steel plates under ultra- high velocity dynamic stretching conditions The experimental setup (ring and cylinder design) was changed slightly to obtain more systematic and reliable results; comparison is made among the various results As presented in Table 3, plates impacted at Energy per Thickness greater than 19,500 (J/cm) with Polyurea backing did not fracture, but the Polyurea- fronted plates fractured at Energy per Thickness value of 16,100 (J/cm) (<<19500 J/cm) 1. Polyurea backing can mitigate failure 2. Polyurea fronting may promote failure Ongoing Research New Experimental Setup Table 1. Bare steel impacting on flat side, first Al-cylinder deign without ring Table 2. Bare steel impacting on flat side, first Al-cylinder design with ring Table 3. Impact condition, second Al-cylinder design (attached ring) UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials Using water to apply shock pressure on the steel plate instead of polyurethane Deformation process, crack propagation and failure modes are being captured with the new setup Steel Plate Impacted on the Flat Side (with and without polyurea) Steel Plate Impacted on the Dish Side (with and without polyurea)


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