LVDT displacement sensor deformation monitoring scheme in tensile tests

Application scenarios

In tensile tests of metals, plastics, and composite materials, it is necessary to accurately measure the elongation within the gauge length of the specimen (such as 50 mm or 25 mm) to calculate mechanical parameters such as stress-strain curves, yield strength, and elastic modulus.

Technical points

● Gauge-length mounting: The LVDT is fixed to both ends of the specimen gauge length by a clamping mechanism and moves synchronously with the specimen elongation.

● Elastic modulus measurement depends on sensor resolution: submicron resolution is a prerequisite for accurately capturing minute deformations during the elastic phase.

● Fracture and detachment protection: Some solutions use magnetic or spring clamps to automatically detach the sensor the moment the sample breaks, preventing impact damage.

Detailed analysis

The elastic modulus calculation in tensile testing typically involves only minimal deformation within the 0.05% to 0.25% strain range, placing high demands on sensor resolution and noise levels. While the resolution of LVDTs is theoretically unlimited (limited by backend AD sampling and noise floor), sub-micron resolution is more common in practical engineering. In gauge-length installations, the coupling stiffness between the sensor and the specimen, as well as parasitic clearances in the clamping mechanism, introduce errors, requiring preload design to eliminate backlash. Dongfang Measurement Instruments' LVDT displacement sensors can be used with customized fixtures for gauge-length extensometer retrofits, or integrated as independent displacement probes into self-made testing fixtures. The output signal supports synchronous recording by a backend acquisition card or MD integrated measuring instrument, forming a complete stress-strain data link.