The impact attenuation performance of a helmet is evaluated by releasing the impactor from a specific height in guided free-fall onto an impact head form. The forces transmitted to the head form are measured with integral load sensor and accelerometer and compared to performance limits.
A large batch of helmets can be easily tested by entering the identification number in to the Database through the LabVIEW VI. The number of impacts, test sites, description of impact location, impact anvil, drops mass, drop velocity; type of standard and type of head-form used are variables that can be set for each helmet tested. (The drop tower complies with helmet test standards stipulated by ASTM, IS, EN, ANSI, Snell, Dot, and other organizations).
Prior to the commencement of testing, database fields incorporated in the SCADA simplify record keeping and report generation once testing is completed. Information such as sizing, helmet identification, conditioning environments and test standards can be entered and stored with the test data.
The user interface
Prior to the commencement of testing, helmet identification, conditioning environments and test standard to be entered and stored with the test data.
Pressing “Configure Test” window invokes the editor menu. Configure required test standard or specification. All the standards have test parameters Mass (g), Heights (m), Velocity (m/s), ‘g’ (m/s²), maximum Force, ‘g’ max limit that will be stored in database.
Set to zero position
Follow steps for setting zero position:
- First magnetize drop carriage slider by pressing “MAGNETIZE” button (Slider magnetized and indicator glow red on slider)
- Keep pressing “IMPACTOR LOWER” button and let the slider move in downwards direction till it reaches impactor striker plate. The moment the impactor touches striker plate, the green light on slider glows; at that point of time release IMPACTOR LOWER KEY. (The interlock will prevent overshoot)
- Click & keep pressed “IMPACTOR RAISE” button, the drop carriage slider with the impactor striker moves up with high speed. Release the button before it touches upper end of impactor rod.
- Use the motor’s low speed to fine tune.
- Click “SET TO ZERO” button to mark zero position(displacement indicator counts ‘set to zero’)
Certain specifications about the impact assembly, head-form, anvil etc. are available in relevant standards and that description is out of scope of this blog.
Test Results to check compliance of the helmet to the relevant standard
The results from each test are instantly displayed both numerically and graphically. The load (Kn) / time graph and Acceleration (g)/time graph will be displayed as per the user requirement- either Shock absorption or Acceleration test. The data are displayed numerically for Velocity@impact, Peak Force, and peak Acceleration. The data are also saved to disk for review at a later date.