An Absolute Calibration System for Nondestructive Testing Devices

Details

• Creators:
  Tandon, Vivek ; Nazarian, Soheil
• Corporate Creators:
  University of Texas at El Paso. Center for Geotechnical and Highway Materials Research
• Corporate Contributors:
  Texas State Department of Highways and Public Transportation
• Subject/TRT Terms:
  Accuracy Algorithms Calibration Deflection Dynaflect Falling Weight Deflectometers Geophones Load Cells Nondestructive Tests Pavements
• Publication/ Report Number:
  913-1 F
• Resource Type:
  Tech Report
• Geographical Coverage:
  Texas ; United States
• Edition:
  Volume 2
• Corporate Publisher:
  University of Texas at El Paso. Center for Geotechnical and Highway Materials Research
• Abstract:
  The Falling Weight Deflectometer (FWD) and Dynaflect devices are presently being used by highway agencies. The primary function of the FWD and Dynaflect devices is to measure a deflection basin due to a load imparted to the pavement. Deflection basins measured in the field are used in backcalculating modulus profiles of pavement sections. As such, it is critical to determine the deflection basins in the field with great accuracy. Velocity transducers (also called geophones) are used to determine the deflections, and load cells are utilized to measure applied load. It has become increasingly important in recent years to be able to evaluate the performance of the deflection and load sensors of the Falling Weight Deflectometer or the Dynaflect devices. It has been shown that a small error in the deflections measured in the field may yield significantly erroneous modulus values. As such, a very reliable method for evaluating the accuracy of the sensors used for determining these deflections is necessary. If geophones are used to determine deflections, the algorithm developed for calculating deflection will also become important. A geophone measures the so-called "raw" particle velocity of the pavement surface directly underneath it. Therefore, the methodology and algorithm employed to obtain the "actual" displacement must be carefully considered. Errors in the load cell measurements are not as important but should be avoided for reliable results. In this report the components and procedures involved in the calibration process are described. The system basically consists of two well-calibrated geophones, three load cells, a signal conditioning unit, a loading plate, and an analog-to-digital board and a computer. A software is developed to control the AID board and to reduce the data. A detailed procedure is also developed and is described in this report. Basically, the load cells are calibrated on a concrete pad, and the geophones are evaluated on an asphaltic surface. The data are analyzed utilizing a statistical package.
• Format:
  PDF
• Funding:
  913
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:14c78e81cd1dda3f2d62a88ee363e7cef09586a1596e1563b1f8c69c89e2455ee88f7182b497e96eb585a838e821abb2b17834aecfbca71d18e103285796d8ec
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/86036/dot_86036_DS1.pdf
• File Type:
  [PDF - 1.14 MB ]