AE12.pdf

Configuration of the test object and the coordinate

This preview shows page 10 - 13 out of 40 pages.

Configuration of the test object and the coordinate system for transducer locations are shown in Fig. 4. The test object in this study consists of a reinforced concrete column and foundation. The dimensions are 0.4 m (16 in.) wide × 0.4 m (16 in.) deep × 1.7 m (68 in.) high and 1 m (40 in.) wide × 2 m (80 in.) deep × 1.15 m (45 in.) high, respectively. Figure 5 shows the lateral 395 Special Applications of Acoustic Emission Testing F IGURE 3. Results of moment tensor analysis in a reinforced concrete rigid frame. Legend = tensile crack = shear crack F IGURE 4. Configuration of the concrete column and the coordinate system: (a) front view; (b) side view; (c) view from overhead. The loading simulates earthquakes. 1 m (40 in.) Loading point Loading point Loading direction Axial Load Axial Load 1.9 m (75 in.) 0.2 m (8 in.) z y 0.8 m (32 in.) 0.4 m (16 in.) z x Loading direction 2 m (80 in.) 1 m (40 in.) (a) (b) (c) 0.2 m (8 in.) 1.7 m (65 in.) 1.15 m (45 in.) 0.4 m (16 in.) 0.4 m (16 in.) 3.25 m (128 in.) Legend x = width in X axis y = depth in Y axis z = height in Z axis
Image of page 10

Subscribe to view the full document.

396 Acoustic Emission Testing F IGURE 5. Loading schedule for concrete column tests. Lateral displacement, mm (in.) Time (relative scale) 160 (6.4) 120 (4.8) 80 (3.2) 40 (1.6) 0 –40 (–1.6) –80 (–3.2) –120 (–4.8) –160 (–6.4) Drift angle, mrad (deg) 3 (0.14) 1 (0.07) 5 (0.29) 10 (0.57) 15 (0.86) 20 (1.15) 30 (1.74) 40 (2.29) 50 (2.86) 59 (3.37) 71 (4.09) 77 (4.41) 1 2 3 4 5 6 7 Loading stages F IGURE 6. To validate the technique, quantitative comparison between predicted and detected cracks in the reinforced concrete foundation: (a) stage 1; (b) stage 4. Predicted Detected z 0 y z 0 x (a) Legend x, y, z = workpiece dimensions = crack initiation site = strain direction Predicted Detected z 0 y z 0 x (b)
Image of page 11
loading schedule applied to the test objects. The columns were subjected to three cycles for each of the maximum predetermined displacements, corresponding to the drift angles. Loading stages are schematically illustrated in Fig. 5. Six resonant 60 kHz transducers were used to detect acoustic emission signals from the foundation. It is well known that the attenuation of acoustic emission waves during propagation depends on their frequencies. At lower frequencies, attenuation is less severe in both the near field and far field. Therefore, optimal frequencies for high sensitivity depend on the size of specimens to be monitored. Because the test objects are relatively small in laboratory tests, high frequency (150 kHz) resonant transducers are widely used. However, low frequency transducers were chosen in the present field test because the test object is much larger than the laboratory specimens. Acoustic emission parameter analysis shows a large difference in the acoustic emission activity between stage 1 (axial load of 156.9 kN) and stage 2 (1.58 MN) in the early phases of the cyclic loadings. Acoustic emission activity in terms of acoustic emission hits and amplitude was much higher in stage 1 than in stage 2 in the early phases of damage.
Image of page 12

Subscribe to view the full document.

Image of page 13
  • Fall '19
  • The Land, Nondestructive testing, Acoustic Emission, Acoustic Emission Testing

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern