Issue 40

Z. Zhang et alii, Frattura ed Integrità Strutturale, 40 (2017) 149-161; DOI: 10.3221/IGF-ESIS.40.13 154 Figure 2 : Material constitutive curves Experiment setup Experiment load and data collection system The load was applied by MTS material test machine and controlled with displacement load, the curve of which is shown in Fig.3. The time history signal of the actual displacement load and bearing capacity was received by B&K 3050 signal collection system with the software Pulse13.0, where the sample frequency is 1kHz. The data collection system is shown in Fig. 4. Figure 3: Displacement load curve. Figure 4 : Signal collection system. Temperature field monitoring system Another important parameter in this experiment is the temperature field, the Cedip Jade III Infrared camera produced by Cedip company with the technology of infraredfocal plane array was used in this experiment for temperature monitoring and collecting the temperature data. Specifically, the focal plane is composed of 320x240 InSb pixel detectors and could collect the surrounding thermal infrared radiation. The sensitivity of the infrared camera is about 0.001K at the room temperature. The temperature data collection system is shown in Fig.5. Also, the thermo sensitivity is better if the integration time is longer, which is usually set as 1.5ms. The infrared image signal process is based on time-domain averaging method to improve the resolution. Specifically, the random Gaussian noise is reduced via averaging n frames in time-domain to obtain one high quality image, which can be realized by the post-process software ALTAIR. In this experiment, the test sample is fixed with 12 high strength bolts by the sample fixture, which consists of two pairs of asymmetrical L-shape support with the layer width of 20mm, the yield strength of 235MPa and yield strength of 406MPa. Also the two pairs of fixtures are connected and fixed with 20 high-strength bolts so as to fix the sample in the center, and the top and bottom are welded with two symmetrical rod holder with a diameter of Ф 36mm, which is designed for the connection of the fixture and the load experiment system. Also the sample surface is coated with black matted paint to improve the rate of thermal radiation of the sample surface.