Split-Hopkinson Pressure Bar - Torsion Testing

Torsion Testing

As with tension testing, there exist a variety of methods for specimen attachment and loading when subjecting materials to torsion on a SHPB.

One way of applying loading called the stored-torque method involves clamping the midsection of the incident bar while a torque is applied to the free end. The incident wave is created by suddenly releasing the clamp, which sends a torsion wave toward the specimen.

Another loading technique known as explosive-loading uses explosive charges on the free end of the incident bar to create the incident wave. This method is particularly sensitive to error because each charge must apply an equal impulse to the incident bar (to create pure torsion without bending) and must both detonate simultaneously. Explosive-loading is also unlikely to produce clean incident waves, which may cause uneven strain rates throughout the test. This method however has the advantage of having a very small rise time as compared to the stored-torque method.