FINITE ELEMENT BEHAVIOR OF AA7075 UNDER SQUARE SHAPE OF STRIKER OF SPLIT HOPKINSON PRESSURE BAR WITH VARYING LOADS

To know the high strain rate behavior of aluminum alloy 7075 (AA7075) is very significant due to its vital uses in aviation, buildings, and automobile industries. Taylor impact test, projectile tests and split Hopkinson pressure bar are usually utilized to know the behavior of materials under high strain rate conditions. But due to lack of availabilities and very costly setups, various types of changes can’t be done easily. However, numerical simulation gives opportunity to observe the phenomena of materials under different conditions without much cost. This paper investigated the behavior of square shaped specimens of AA7075 under varying impact velocities of impact velocities of 20m/s-50m/s of square striker bar of SHPB using Abaqus. To understand the importance of shape, striker bar and specimen shape are varying from square to circular under dynamic conditions. Results obtained under varying conditions indicated that the material behavior strongly dependent to the strain rates, striker shapes and specimen shapes.

A Rapid Throughput System for Shock and Impact Characterization: Design and Examples in Compaction, Spallation, and Impact Welding

Many important physical phenomena are governed by intense mechanical shock and impulse. These can be used in material processing and manufacturing. Examples include the compaction or shearing of materials in ballistic, meteor, or other impacts, spallation in armor and impact to induce phase and residual stress changes. The traditional methods for measuring very high strain rate behavior usually include gas-guns that accelerate flyers up to km/s speeds over a distance of meters. The throughput of such experiments is usually limited to a few experiments per day and the equipment is usually large, requiring specialized laboratories. Here, a much more compact method based on the Vaporizing Foil Actuator (VFA) is used that can accelerate flyers to over 1 km/s over a few mm of travel is proposed for high throughput testing in a compact system. A system with this primary driver coupled with Photonic Doppler Velocimetry (PDV) is demonstrated to give insightful data in powder compaction allowing measurements of shock speed, spall testing giving fast and reasonable estimates of spall strength, and impact welding providing interface microstructure as a function of impact angle and speed. The essential features of the system are outlined, and it is noted that this approach can be extended to other dynamic tests as well.

High Strain Rate Behavior of Aluminum Alloy for Sheet Metal Forming Processes

Aluminum alloy sheets are gaining increasing interest in the construction of some or all components of the car body in view of their lightweight properties which can allow significant fuel consumption reduction. In order to be suitable for car body application, aluminum alloy sheets should have sufficient mechanical properties both in static (e.g., structural stability and durability) and dynamic conditions (e.g., crash test). Static and dynamic mechanical tests (strain rates: ε ˙ ≈ 1 × 10−3 s−1 and ε ˙ ≈ 5 × 102 s−1 respectively) were conducted on AA6016 alloy sheet (1 mm thick), in T4 and T6 temper and for the longitudinal, transverse, and diagonal rolling directions by means of standard static tensile test and modified Hopkinson bar dynamic tests. Microstructural and fracture morphology observations are also reported. The results show that the ultimate tensile strength increases by 13−14%, and the elongation at fracture increases by 75−105%, depending on the temper, by increasing the strain rate.