Document ID: chunk:federal_register_of_legislation:F2025L00028:front:0:p33
Version: federal_register_of_legislation:F2025L00028
Segment Type: other
Provision Reference: 
Character Range: 93066–96242

6.6.2.3.               Accelerometer data for impulse calculations will be filtered to CFC 60, ISO 6487:1987.

              6.6.2.4.               Load cell data will be filtered to CFC 60, ISO 6487:1987.

              6.6.3.               Calculation of MDB face deflection

              6.6.3.1.               Accelerometer data from all three accelerometers individually (after filtering at CFC 180), will be integrated twice to obtain deflection of the barrier deformable element.

              6.6.3.2.               The initial conditions for deflection are:

              6.6.3.2.1. Velocity = impact velocity (from speed measuring device).

              6.6.3.2.2. Deflection = 0

              6.6.3.3.               The deflection at the left hand side, mid-line and right hand side of the mobile deformable barrier will be plotted with respect to time.

              6.6.3.4. The maximum deflection calculated from each of the three accelerometers should be within 10 mm. If it is not the case, then the outlier should be removed and difference between the deflections calculated from the remaining two accelerometers checked to ensure that it is within 10 mm.

              6.6.3.5. If the deflections as measured by the left hand side, right hand side and mid-line accelerometers are within 10 mm, then the mean acceleration of the three accelerometers should be used to calculate the deflection of the barrier face.

              6.6.3.6. If the deflection from only two accelerometers meets the 10 mm requirement, then the mean acceleration from these two accelerometers should be used to calculate the deflection for the barrier face.

              6.6.3.7. If the deflections calculated from all three accelerometers (left hand side, right hand side and mid-line) are NOT within the 10 mm requirement, then the raw data should be reviewed to determine the causes of such large variation. In this case the individual test house will determine which accelerometer data should be used to determine mobile deformable barrier deflection or whether none of the accelerometer readings can be used, in which case, the certification test must be repeated. A full explanation should be given in the test report.

              6.6.3.8. The mean deflection-time data will be combined with the load cell wall force-time data to generate the force-deflection result for each block.

              6.6.4. Calculation of energy

                The absorbed energy for each block and for the whole MDB face should be calculated up to the point of peak deflection of the barrier.

 Where:

 t0         is the time of first contact,

 t1         is the time where the trolley comes to rest, i.e. where u = 0,

 s          is the deflection of the trolley deformable element calculated according to paragraph 6.6.3.

              6.6.5. Verification of dynamic force data

              6.6.5.1. Compare the total impulse, I, calculated from the integration of the total force over the period of contact, with the momentum change over that period (M*V).

              6.6.5.2. Compare the total energy change to the change in kinetic energy of the MDB, given by: