Presentation on theme: "Effect of Polyurea on Dynamic Response of Steel Plates"— Presentation transcript:
1 Effect of Polyurea on Dynamic Response of Steel Plates UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced MaterialsEffect of Polyurea on Dynamic Response of Steel PlatesExperimental InvestigationStudent: Mahmoud Reza AminiAdvisor: Prof. Sia Nemat-NasserSteel 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 conditionsDH-36 Steel Plate3” outer diameterM = 90~95 g t = 0.038”~0.041”With Polyurea FrontingWithout Polyurea FrontingDynamic Impulsive Loading of Steel PlatesubjectThe experimental setup (ring and cylinder design) was changed slightly to obtain more systematic and reliable results; comparison is made among the various results3-inch Hopkinson BarExperimental InvestigationGas Gun BarrelProjectilePolyurethaneConfinementSteel BarV0Ultra high speed camera, Imacon 200Severe FailureSevere FailureEnhance the Energy Absorbing CharacteristicsProblemImpact Velocity = m/sInput Energy = JThickness = cmEnergy/Thickness = J/cmImpact Velocity = m/sInput Energy = JThickness = cmEnergy/Thickness = J/cmLS-DYNA (FEM)Computational EvaluationUser-Defined Materials Constitutive ModelsTable 1. Bare steel impacting on flat side, first Al-cylinder deign without ringExperiments Without Ring, Cylinder #1Effect of Polyurea on Steel Plate FractureFracture Mode and Severity, Shear Band and NeckingSteel Plate Impacted on the Flat Side (with and without polyurea)With Polyurea BackingWithout Polyurea BackingPolyurea in FrontEffect of Polyurea on Steel Plate Dynamic ResponseTopics of InvestigationsEnergy per Thickness > (J/cm)FracturePolyurea in BackPolyurea-Steel Layers Design ConfigurationTable 2. Bare steel impacting on flat side, first Al-cylinder design with ringNo PolyureaExperiments With Ring, Cylinder #1No FailureSevere Failure= steel plate= polyurea= impact sideExperimental ResultsImpact Velocity = m/sInput Energy = JThickness = cmEnergy/Thickness = J/cmImpact Velocity = m/sInput Energy = JThickness = cmEnergy/Thickness = J/cmExperimental SetupThe most important experimental quantities include:Imparted energy (mass of projectile, ring and plate and projectile velocity)Steel plate thicknessPolyurea location if used3-inch Steel BarAl 7075 CylinderSteel ConfinementPolyurethaneDH-36 Steel Plate17-4 pH Steel RingV0ProjectileGas Gun BarrelEnergy per Thickness > (J/cm)FractureOngoing ResearchNew Experimental SetupTable 3. Impact condition, second Al-cylinder design (attached ring)Experiments Without Ring, Cylinder #2Using water to apply shock pressure on the steel plate instead of polyurethaneAt large deformations (deflection/thickness > 10) the membrane effect is predominant. Thus the behavior of the steel plate is proportional to the inverse of the thicknessDeformation process, crack propagation and failure modes are being captured with the new setupFour different configurations of steel plate and polyurea layersPlates behave as simply-supportedDishFlatFlat + PU/BackedDish + PU/FrontedFailure 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)PolyurethanePolyurethanePolyurethanePolyurethaneSevere FailureSlight FailureNo FailureTop ViewSide ViewPlatePolyureaPlatePlatePolyureaPlatePolyurea backing can mitigate failurePolyurea fronting may promote failureCylinderCylinderCylinderCylinderIntroductionNature of the ProblemConclusions and ResultsSummary & Future DirectionsThe 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.UC San Diego Mechanical and Aerospace Engineering Center of Excellence for Advanced Materials
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