On-Specimen Measurement

GCTS offers multiple solutions for on-specimen measurement of various specimen properties.

The DEF-5000 Rock Deformation Devices measure axial and average radial strain directly on the specimen using two axial LVDT holder rings and a radial chain device. This setup is available for all specimens with a starting diameter between 25 mm and 150 mm and can be used within our high-pressure triaxial cell at elevated or low temperatures. Elastic constants such as Young’s modulus and Poisson’s ratio can be determined as well as inelastic strains that occur after sample failure (post failure analysis). By utilizing this setup with one of our servo control units and load frames, direct control of the axial or radial strain of a specimen can be performed.

The DEF-CAN Diametral Deformation Device replaces the radial chain device from the DEF-5000 with a cantilever bridge for measurement of the radial strain in two planes. This device consists of a single ring connected to four sensor arms, each located 90 degrees apart, and each equipped with a strain gauge that is paired to the opposite arm. This allows two diametral deformations to be measured, helping to account for non-homogeneous specimen deformation. This device mounts directly onto a specimen through the use of long screws attached to the arms of the cantilever. By using these long screws, the device can quickly and easily be adjusted to fit a large range of specimen diameters. This device can also be used within a high-pressure, high-temperature triaxial cell or in an unconfined setting.

The CDM fixtures are designed to measure various parameters across a cylindrical specimen.  They are used with a reusable membrane that is capable of withstanding pressures up to 210 MPa (30,000 psi) and temperatures up to 200˚C.  These membranes incorporate four lateral ports located at the mid specimen height of each circumference quadrant. GCTS offers a variety of sensors that can be used together with the GCTS DEF-CAN Diametral Deformation device to obtain different physical properties simultaneously. These sensors are simply inserted into the membrane lateral ports and are typically provided in pairs, allowing for a combination of different type of sensors. This setup can also accommodate axial sensors (ultrasonic, Acoustic Emissions, Axial Strain, etc.) to perform simultaneous measurements in three-dimensional space. GCTS can provide membranes with various sizes and different port configurations as required.