Modelling the Fracture of High-Hardness Armour Steel in Taylor Rod-on-Anvil Experiments

2019 ◽  
Author(s):  
Brodie McDonald ◽  
Shannon Ryan ◽  
Stephen J. Cimpoeru ◽  
Nathan Edwards ◽  
Adrian Orifici
Keyword(s):  
Shear Band ◽  
Impact Velocity ◽  
Numerical Models ◽  
Computational Cost ◽  
Stress Triaxiality ◽  
High Hardness ◽  
Material Strength ◽  
Fracture Threshold ◽  
The Impact ◽  
Armour Steel

Abstract A series of Taylor rod-on-anvil experiments have been performed to validate the predicted impact velocity fracture threshold and fracture mode of a high hardness armour steel (HHA) obtained through explicit finite element simulations. Experimentally, the rods exhibited principal shear failure, a condition that can be closely linked to adiabatic shear band (ASB) formation in high strength steel. Using a stress triaxiality and Lode angle dependent failure strain criterion (Basaran 3D fracture locus), calibrated from quasi-static mechanical characterisation tests, the simulations were unable to predict the onset of fracture observed in experiments. As such, a strength-fading criterion is proposed using a phenomenological description to capture the loss of load-carrying capacity resulting from ASB formation. The ASB criterion is based on an exponential fit to experimentally-observed instability strains measured at different average stress triaxialities in a series of tests on inclined cylindrical and modified flat-hat specimens. With the prediction of ASB formation the material strength is reduced to model the thermal softening experienced in the shear band, and fracture of the material (in the form of element erosion) remains controlled by the Basaran fracture model. Incorporating the ASB-based criterion, the numerical models were found to accurately predict both the impact velocity fracture threshold, as well as the general appearance of the observed principal shear fracture. The proposed criterion enables the effects of ASB formation to be captured in an impact simulation with little increase in computational cost.

scholarly journals Influence of Add-On Perforated Plates on the Protective Performance of Light-Weight Armour Systems

2018 ◽  
Vol 9 (1) ◽  
pp. 31-48
Author(s):  
Teresa FRAS ◽  
Norbert FADERL
Keyword(s):  
Hard Core ◽  
High Hardness ◽  
Steel Plates ◽  
Perforated Plates ◽  
Geometrical Properties ◽  
Impact Position ◽  
Circular Holes ◽  
Protective Performance ◽  
The Impact ◽  
Armour Steel

The presented experimental investigation, aimed at verification of defeat mechanisms against small-calibre projectiles, provided by 4-mm-thick perforated plates with different material- and geometrical properties, was performed. A regular pattern of punched holes in steel plates increases the possibility of asymmetrical contact between the plate and projectiles which may cause threat destabilization, rotation or fragmentation depending on the impact position. Three tested armour configurations comprise the super-bainitic high-hardness Pavise™ SBS 600P armour steel plates perforated by elongated holes of size 4  12 mm (the first configuration), the martensitic high-hardness Mars® 300P steel plates perforated by circular holes with a diameter of 5 mm (in the second configuration); and in the third configuration, the martensitic Mars® 300 plates perforated by oblong holes (4  10 mm) were used. The performed impact tests proved that the tested add-on plates assured high protection against the impact of 7.62  51 .308 Win P80 hard-core armour piercing (AP) projectiles. It was also observed that the plates caused similar mechanisms of bullet failure.

scholarly journals Static and Dynamic Four-Point Flexural Tests of Concrete Beams with Variation in Concrete Quality, Reinforcement Properties and Impact Velocity

2021 ◽  
Vol 65 (2) ◽  
pp. 19-38
Author(s):  
Viktor Peterson ◽  
Anders Ansell
Keyword(s):  
Plastic Strain ◽  
Impact Velocity ◽  
Strain Distribution ◽  
Concrete Beams ◽  
Numerical Models ◽  
Reinforced Concrete Beams ◽  
Concrete Quality ◽  
Flexural Tests ◽  
Future Work ◽  
The Impact

Abstract This paper discusses the results from three experimental test series previously conducted. The tests consist of quasi-static monotonic and dynamic four-point flexural tests on reinforced concrete beams. The effect of varying material and load parameters on the plastic strain distribution and energy absorbed by the reinforcement is discussed. The main findings are the significant effect of the post-elastic region of the steel reinforcement and the impact velocity during dynamic loading. The results will be used to validate and construct numerical models in future work, where the findings presented can be investigated further.

scholarly journals Ballistic Impact and Virtual Testing of Woven FRP Laminates

2021 ◽  
Vol 5 (5) ◽  
pp. 115
Author(s):  
Ioannis K. Giannopoulos ◽  
Mehdi Yasaee ◽  
Nikolaos Maropakis
Keyword(s):  
Numerical Models ◽  
Progressive Failure ◽  
Computational Cost ◽  
Carbon Composite ◽  
Steel Ball ◽  
Element Analysis ◽  
General Behaviour ◽  
Explicit Finite Element ◽  
The Impact ◽  
Fidelity Model

The aim of the work was to investigate the numerical simulations correlation with the experimental behaviour of steel ball high velocity impact onto a 2 × 2 twill woven carbon composite laminate. The experimental set up consisted of a pressurised gas-gun able to shot steel ball projectiles onto two different composite plate layup configurations of plates made of the same composite material fabric. Subsequently, the experiments were replicated using the LSDYNA explicit finite element analysis software package. Progressive failure numerical models of two different fidelity levels were constructed. The higher fidelity model was simulating each of the plys of the composite panels separately, tied together using cohesive zone modelling properties. The lower fidelity model consisted of a single layer plate with artificial integration points for each ply. The simulation results came out to be in satisfactory agreement with the experimental ones. While the delamination extent was moderately under predicted by the higher fidelity model, the general behaviour was complying with the experimental results. The lower fidelity model was consistent in representing the damage of the panel during the impact and better predicted the impactor residual velocities due to the better matching of the pane stiffness. Despite the competency of the higher fidelity model to capture the damage of the laminate in a more detailed level, the computational cost was 80% higher than the lower fidelity case, which rendered that model impractical against the lower fidelity one, to use in larger models representing more substantial or more complex structures.

scholarly journals Postmortem Analysis Using Different Sensors and Technologies on Aramid Composites Samples after Ballistic Impact

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2853 ◽  
Author(s):  
Ignacio Rubio ◽  
Antonio Díaz-Álvarez ◽  
Richard Bernier ◽  
Alexis Rusinek ◽  
Jose Antonio Loya ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Numerical Models ◽  
Reaction Force ◽  
Residual Deformation ◽  
Ballistic Impact ◽  
Piezoelectric Sensors ◽  
Specimen Thickness ◽  
3D Scanner ◽  
Internal Damage ◽  
The Impact

This work focuses on the combination of two complementary non-destructive techniques to analyse the final deformation and internal damage induced in aramid composite plates subjected to ballistic impact. The first analysis device, a 3D scanner, allows digitalising the surface of the tested specimen. Comparing with the initial geometry, the permanent residual deformation (PBFD) can be obtained according to the impact characteristics. This is a significant parameter in armours and shielding design. The second inspection technique is based on computed tomography (CT). It allows analysing the internal state of the impacted sample, being able to detect possible delamination and fibre failure through the specimen thickness. The proposed methodology has been validated with two projectile geometries at different impact velocities, being the reaction force history on the specimen determined with piezoelectric sensors. Different loading states and induced damages were observed according to the projectile type and impact velocity. In order to validate the use of the 3D scanner, a correlation between impact velocity and damage induced in terms of permanent back face deformation has been realised for both projectiles studied. In addition, a comparison of the results obtained through this measurement method and those obtained in similar works, has been performed in the same range of impact energy. The results showed that CT is needed to analyse the internal damage of the aramid sample; however, this is a highly expensive and time-consuming method. The use of 3D scanner and piezoelectric sensors is perfectly complementary with CT and could be relevant to develop numerical models or design armours.

scholarly journals Adiabatic Blanking: Influence of Clearance, Impact Energy, and Velocity on the Blanked Surface

2021 ◽  
Vol 5 (2) ◽  
pp. 35
Author(s):  
Sven Winter ◽  
Matthias Nestler ◽  
Elmar Galiev ◽  
Felix Hartmann ◽  
Verena Psyk ◽  
...  
Keyword(s):  
Shear Band ◽  
Process Parameters ◽  
Impact Energy ◽  
Adiabatic Shear Band ◽  
High Hardness ◽  
Adiabatic Shear ◽  
Shear Band Formation ◽  
Band Formation ◽  
Adiabatic Shear Band Formation ◽  
The Impact

In contrast to other cutting processes, adiabatic blanking typically features high blanking velocities (>3 m/s), which can lead to the formation of adiabatic shear bands in the blanking surface. The produced surfaces have excellent properties, such as high hardness, low roll-over, and low roughness. However, details about the qualitative and quantitative influence of significant process parameters on the quality of the blanked surface are still lacking. In the presented study, a variable tool is used for a systematic investigation of different process parameters and their influences on the blanked surface of a hardened 22MnB5 steel. Different relative clearances (1.67% to 16.67%), velocities (7 to 12.5 m/s), and impact energies (250 J to 1000 J) were studied in detail. It is demonstrated that a relative clearance of ≤6.67% and an impact velocity of ≥7 m/s lead to adiabatic shear band formation, regardless of the impact energy. Further, an initiated shear band results in the formation of an S-shaped surface. Unexpectedly, a low impact energy results in the highest geometric accuracy. The influence of the clearance, the velocity, and the impact energy on the evolution of adiabatic shear band formation is shown for the first time. The gained knowledge can enable a functionalization of the blanked surfaces in the future.

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

Assessment of the impact of gaseous ship emissions in ports using physical and numerical models: The case of Naples

2021 ◽  
pp. 107812
Author(s):  
Domenico Toscano ◽  
Massimo Marro ◽  
Benedetto Mele ◽  
Fabio Murena ◽  
Pietro Salizzoni
Keyword(s):  
Numerical Models ◽  
Ship Emissions ◽  
The Impact

scholarly journals Aluminium Alloy Foam Modelling and Prediction of Elastic Properties Using X-ray Microcomputed Tomography

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 925
Author(s):  
Diogo Heitor ◽  
Isabel Duarte ◽  
João Dias-de-Oliveira
Keyword(s):  
Aluminium Alloy ◽  
Finite Element Modelling ◽  
Effective Properties ◽  
Numerical Models ◽  
Microcomputed Tomography ◽  
Cellular Materials ◽  
Metallic Foams ◽  
X Ray ◽  
The Impact ◽  
Structural Imperfections

X-ray microcomputed tomography has been gaining relevance in the field of cellular materials to characterize materials and analyse their microstructure. So, here, it was used together with finite element modelling to develop numerical models to estimate the effective properties (Young’s modulus) of aluminium alloy foams and evaluate the effects of processing on the results. A manual global thresholding technique using the mass as a quality indicator was used. The models were reconstructed (Marching Cubes 33), then simplified and analysed in terms of mass and shape maintenance (Hausdorff distance algorithm) and face quality. Two simplification procedures were evaluated, with and without small structural imperfections, to evaluate the impact of the procedures on the results. Results demonstrate that the developed procedures are good at minimizing changes in mass and shape of the geometries while providing good face quality, i.e., face aspect ratio. The models are also shown to be able to predict the effective properties of metallic foams in accordance with the findings of other researchers. In addition, the process of obtaining the models and the presence of small structural imperfections were shown to have a great impact on the results.

scholarly journals Air mediates the impact of a compliant hemisphere on a rigid smooth surface

Soft Matter ◽  
2021 ◽  
Author(s):  
Siqi Zheng ◽  
Sam Dillavou ◽  
John M. Kolinski
Keyword(s):  
Elastic Body ◽  
Elastic Properties ◽  
Impact Velocity ◽  
Solid Surface ◽  
High Speed ◽  
Smooth Surface ◽  
High Speed Imaging ◽  
The Impact ◽  
Rigid Smooth

When a soft elastic body impacts upon a smooth solid surface, the intervening air fails to drain, deforming the impactor. High-speed imaging with the VFT reveal rich dynamics and sensitivity to the impactor's elastic properties and the impact velocity.

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