New fixtures are designed for use in conjunction with forced gas oven, and enable the characterisation of dynamic properties such as loss and storage moduli
Bohlin Instruments has introduced rectangular torsion fixtures for its Gemini and C-VOR rheometers which are designed to accept a solid sample with a free length of 50mm, width to 13mm and thickness to 10mm.
The ability to measure on larger sample sizes is of particular use for samples containing small particles of aggregate such as bituminous mixes where bulk property determination of the mix is of practical interest.
The new fixtures are designed for use in conjunction with Bohlin's forced gas oven (ETC) and enable the characterisation of dynamic properties, such as loss and storage moduli, over a wide temperature and frequency range.
The temperature range can be extended downwards to -150C when the liquid nitrogen cooling option is employed.
Spring loaded and infinitely adjustable clamps are designed to make sample loading easy without the need to select spacers or shims according to the sample thickness. Uniformity and reproducibility of clamping pressure is ensured by the use of a pre-set torque driver to tighten the sample clamps. A particular feature of the Bohlin design is the ability to fully load and accurately align the sample within the clamps remotely from the rheometer unit.
This is accomplished using a special sample alignment jig and significantly simplifies the experimental set up procedure.
