Split Hopkinson Bar Test Apparatus

Split Hopkinson Bar Test Apparatus

   Materials undergo high strain rates deformation in various applications, e.g. accidental events such as explosions and penetrations, and engineering applications such as crash worthiness of vehicles, bullet proof armors, impact resistant pressure vessel and shipping cask for transport of nuclear materials. In addition to this,forming processes like extrusion, rolling and high speed machining can also result in high strain rate deformation.
   For the optimal design and safety analysis of components seeing high strain rates of loading the constitutive behavior of materials at high strain rates is required.
   Dynamic testing of material is becoming more important due to the need for more optimized crashworthiness and impact analysis. Positive strain rate sensitivity, i.e. the strength increases with strain rate, offers a potential for improved energy absorption during a crash event. The load can be an instant load wave used for very high strain rate. The machine will also have the proper measurement systems to measure and record the important parameters, such as strain, displacement and load.
   The systems has been developed by Adavnce Instrument Inc. in recent years to meet the increasing demand for dynamic testing.

   Split-Hopkinson bar (SHB) works on the principle of one dimensional wave propagation. Its main components are a gas gun, a striker bar, an incident bar and a transmission bar . The striker bar sits in the barrel at the gas gun chamber. The incident bar, transmission bar and striker bar are all made of same material and same crosssection area. At all times during the test the striker, incident and transmission bar should remain elastic. The sample to be tested is sandwiched between the incident and transmission bar. The striker bar is propelled by gas
pressure towards the incident bar.
   On impact, an elastic compression wave propagates down the incident bar toward the sample. On reaching the sample, repeated wave propagation within it deforms it plastically. Part of the wave goes through to the transmission bar (transmitted pulse) and part is reflected back into the incident bar (reflected pulse), each of which is picked up by the strain gauges mounted on the corresponding bars. Strain gauges on each bar are mounted to the axial strain. Elastic strain generated in incident and transmission bar are used to calculate the stress-strain in
the sample.

Fully in-house self-made Split Hopkinsonson Pressure Bar solution:
● World one and only 2-in-1,  Compression / Tension mode, GAS GUN system
● Strain Rate 100 to 10,000 /sec
● STIKER BAR accelerator design for < 3MPa low pressure gas
● SENSOR ROD adopts point-type design, has low friction coefficient
● Accuracy of 0.25% high-precision LASER BEAM speed measuring device
● Automatic pressure transmission system
● Complete security and alarm design
High strain rate testing
Strain rate sensitivity testing

Strain rate hardening testing

   Advance Instrument Inc's designs a number of conceptual for SHPB were thought of and the optimized design was worked out. The precision tolerance, straightness in bars and design and proper functioning of pneumatic gun were met. This setup has been used extensively to study the high strain rate material behavior.
   The system consists of the dynamic loading units, data acquisition and control system and spare parts & tools. The facility is designed for Split Hopkinson Bar Compression high strain rate testing. The system can be equip with high temperature heating system and cooling system. Advance Instrument Inc's apparatus of SHB is the direct determination of dependence of the deformation stress – strain curves and the strain rate – strain curves.
   The system includes a gas gun & bar system for dynamic loading unit, which makes operation safe and easy.
   Advance Instrument Inc's have works closely with Ph. D. Yuh Shiou Tai, leader of the Structure Engineering Lab Department of Civil Engineering, ROC Military Academy.