Effect of Polyurea on Dynamic Response of Steel Plates Experimental Investigation

1. UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials V0 Steel Bar Confinement Polyurethane Projectile Gas Gun Barrel Polyurethane Gas Gun Barrel DH-36 Steel Plate = steel plate = polyurea = impact side V0 Al 7075 Cylinder 3-inch Steel Bar 17-4 pH Steel Ring Projectile Steel Confinement Top View Side View Severe Failure DH-36 Steel Plate 3” outer diameter M = 90~95 g t = 0.038”~0.041” Slight Failure No Failure Effect of Polyurea on Dynamic Response of Steel Plates Experimental Investigation Student: Mahmoud Reza Amini Advisor: Prof. Sia Nemat-Nasser http://ceam.ucsd.edu Steel Plate Impacted on the Dish Side (with and without polyurea) Necking and shearbanding are typical mechan-isms of failure of the steel plates under ultra-high velocity dynamic stretching conditions With Polyurea Fronting Without Polyurea Fronting Dynamic Impulsive Loading of Steel Plate subject The experimental setup (ring and cylinder design) was changed slightly to obtain more systematic and reliable results; comparison is made among the various results 3-inch Hopkinson Bar Experimental Investigation Ultra high speed camera, Imacon 200 Severe Failure Severe Failure Enhance the Energy Absorbing Characteristics Problem Impact Velocity = 64.90 m/s Input Energy = 1597.68 J Thickness = 0.0991 cm Energy/Thickness = 16128.4 J/cm Impact Velocity = 67.34 m/s Input Energy = 1703.40 J Thickness = 0.1040 cm Energy/Thickness = 16378.8 J/cm LS-DYNA (FEM) Computational Evaluation User-Defined Materials Constitutive Models Table 1. Bare steel impacting on flat side, first Al-cylinder deign without ring Experiments Without Ring, Cylinder #1 Fracture Mode and Severity, Shear Band and Necking Effect of Polyurea on Steel Plate Fracture Steel Plate Impacted on the Flat Side (with and without polyurea) With Polyurea Backing Without Polyurea Backing Polyurea in Front Effect of Polyurea on Steel Plate Dynamic Response Topics of Investigations Fracture Energy per Thickness > 17950 (J/cm) Polyurea in Back Polyurea-Steel Layers Design Configuration Table 2. Bare steel impacting on flat side, first Al-cylinder design with ring No Polyurea Experiments With Ring, Cylinder #1 No Failure Severe Failure Experimental Results Impact Velocity = 76.65 m/s Input Energy = 2231.35 J Thickness = 0.1061 cm Energy/Thickness = 21016.4 J/cm Impact Velocity = 74.75 m/s Input Energy = 2084.90 J Thickness = 0.0992 cm Energy/Thickness = 21012.9 J/cm Experimental Setup The most important experimental quantities include: Imparted energy (mass of projectile, ring and plate and projectile velocity) Steel plate thickness Polyurea location if used Fracture Energy per Thickness > 19500 (J/cm) Ongoing Research New Experimental Setup Table 3. Impact condition, second Al-cylinder design (attached ring) Experiments Without Ring, Cylinder #2 Using water to apply shock pressure on the steel plate instead of polyurethane 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 Deformation process, crack propagation and failure modes are being captured with the new setup Four different configurations of steel plate and polyurea layers Plates behave as simply-supported Dish Flat Flat + PU/Backed Dish + PU/Fronted Failure can be qualitatively categorized as shown: 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) Polyurethane Polyurethane Polyurethane Polyurethane Plate Polyurea Plate Plate Polyurea Plate • Polyurea backing can mitigate failure • Polyurea fronting may promote failure Cylinder Cylinder Cylinder Cylinder Introduction Nature of the Problem Conclusions and Results Summary & Future Directions 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. 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. 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.