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Crash Testing Tools – Instrumentation


One of the ongoing research projects that Sintra Engineering is engaged in is a study of the parameters and results of low speed automobile accidents (less than 15 kilometers per hour). The current test series we are engaged in consists of a variety of single vehicles impacting a solid barrier on both the front and rear bumpers, at a range of speeds up to a maximum of 15 kilometers per hour.

The test vehicles are carefully measured and photographed in their pretest condition; with particular attention being paid to the condition of the front and rear bumpers, covers and structural members. We also examine the fit and alignment of the front and rear quarter panels. After each impact the vehicle is photographed again, and all of the measurements are repeated to quantify any damage or displacement, no matter how subtle.

In addition to the physical examination and measurements, we also record data such as velocity and acceleration, using a data acquisition system. The system consists of a linear position transducer called the 5th wheel, a set of perpendicularly mounted accelerometers, a floor mounted ribbon switch, and a data acquisition hub that connects all the individual instruments to a single computer.

The 5th wheel is literally a smaller, non weight bearing 5th wheel that gets temporarily mounted to one door of the test vehicle. This 5th wheel is fitted with an opti-electric rotary transducer that produces 2024 pulses per rotation. This pulse per rotation number, coupled with the diameter of the wheel, gives us a positional resolution of less than 3mm per pulse. The data acquisition hub has a built-in clock that can measure the time between pulses to accuracies of better than 0.001 seconds. These two data streams are combined to give us an accurate report of the velocity of the test vehicle, both before and after the impact, which is recorded in a spreadsheet data file.

The acceleration component of the vehicle dynamics is measured by a pair of piezo-electric accelerometers that are temporarily mounted to the floor pan of the test vehicle. One accelerometer is aligned with the longitudinal axis of the vehicle and the other the transverse axis. These transducers return a voltage signal proportional to the magnitude and direction of the acceleration they experience, which is converted to an acceleration value using the calibration number that comes with each accelerometer. These acceleration values are recorded as separate data streams in their own data files, just like the velocity data. To ensure the velocity and acceleration data streams are accurately synchronized the signal from the ribbon switch is recorded in all of the individual data files. That’s the technical side of things.

The real value of the results garnered from this type of testing is in the correlations that can be drawn between the measured resultant damage of the impact and the recorded dynamics of a given impact. It means that our engineers are able to more accurately estimate the changes in velocity experienced by a vehicle occupant by measuring a vehicle’s damage following an impact. This can help answer questions about the likelihood of injury expected by an occupant involved in a low speed collision. This can be valuable information in understanding your position in a claim involving an occupant reporting serious or sustaining injuries following a low speed impact.
 


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