Sample at
T = 400 °C

Sample at
T = 1100 °C

A Laser Extensometer optimized for use at elevated temperatures was used for measuring strain at a TMF experiment (Thermo-Mechanical-Fatigue). The experiments were carried out at MTU Aero Engines and served as a performance test of our Laser Extensometers.
The specimen was heated by inductive coils cycling between the temperatures 400 °C and 1100 °C. The two figures show the specimen at the lower and the upper temperature level.
The specimen was equipped with 8 markers. For marking Al₂O₃ powder was used, which was successfully applied up to 1400 °C.

The figure on the left hand side shows the signals temperature, strain and stress as recorded throughout the experiment. Two sections are marked.

The second diagram shows the temperature-strain curves for the two sections and the stress-strain curve for the second section. The little bumps of the curves are caused by parameters which were not important for the test measurements. These parameters were therefore not optimized.

To achieve optimum accuracy, the laser extensometer was equipped with heat blockers. To reduce influence of turbulences effectively, an evacuated tube was used. For blocking the induction of the high frequency electromagnetic radiation, a protective metal shield was inserted.