Effect of Polyurea on Dynamic Response of Steel Plates

1
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
Without Polyurea Fronting
With 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)
Without Polyurea Backing
With 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
Flat
Dish PU/Fronted
Flat PU/Backed
Dish
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) (Polyurethane
Polyurethane
Polyurethane
Polyurethane
Plate
Polyurea
Plate
Plate
Plate
Polyurea

• 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.