Measurement and Analysis

Physical effects such as force, strain and accelerations are conventionally made with physical sensors such as load cells or strain gauges. In recent years the steady improvement in video imaging and computing power has allowed video measurement to replace some techniques. Deformation of surrogate skulls under dynamic load are used to investigate injury mechanisms and protection systems.  Strain gauges have been used to measure deflections on skull simulants under dynamic load strain gauges provide precise measurements. Alternatively, Digital Image Correlation (DIC) which is a stereo imaging technique that may use high speed cameras to provide whole surface strain mapping. The strain resolution is comparable to strain gauges whilst the temporal resolution is only limited by the frame rates of the cameras. 

Strain gauges are used here as a method to measure skull deflection under simulated blast load in a shock tube.

Harington B, Peare A & Horsfall I (2016) The study of a human head simulant's dynamic response to a blast wave. In: 29th International Symposium on Ballistics, 2016, Edinburgh, 9-13 May 2016.

Recently DIC has been used as it provides a much more complete view of strains in complex cases such as skulls under impact loading.

Franceskides  C, Leger T, Horsfall I, Shanker T, Adams GJ , Clasper J & Zioupos P  (2016) Evaluation of bone excision on occipital area of simulated human  skull. In: 22nd Congress of the European Society of Biomechanics (ESB  2016), Lyon. 

The Digital Image Correlation software used in this study was GOM ARAMIS.

The Camera system was a pair of Vision Research Phantom ultra high speed videos. 

The impact tests were conducted in an Imatek IM10 accelerated instrumented drop tower.

An instrumented knife was developed so that the energy that people can generate in a stabbing could be assessed for armour test standards.  This used a load cell and accelerometer to determine the velocity, force and energy during stabbing.

Horsfall I, Prosser P D, Watson C H & Champion S M (1999) An assessment of human performance in stabbing., Forensic Science International, 102 (2-3) 79-89.

The Instrumented knife was used in further studies for stab standards, forensic aspects of knife damage to clothing and to investigate the historical and prehistorical use of spears.