Biomechanical engineers are commonly called upon to evaluate the kinematics and subsequent biomechanical loading patterns of individuals involved in various types of incidents and accidents. In other words, biomechanical engineers may be asked how the human body moves in response to external forces and how those forces can cause various types of injuries. Researchers, scientists and engineers have used test dummies, a.k.a. Anthropomorphic Test Devices or ATDs, to evaluate how the human body responds to external forces such as crashes and impacts to the body. ATDs have been compared and validated against studies and testing conducted over the years with live humans and cadavers. The live human and cadaver testing have been reported in scientific literature and provide significant insight into how to evaluate the potential for human injury. With that data as a backdrop, today’s biomechanical engineers can utilize both volunteers and ATDs to study the biomechanical response of the human body to dynamic loading and evaluate the mechanisms and tolerances of specific components of the body to injury.
A proper biomechanical engineering protocol can be used to analyze injury potential and causation in motor vehicle accidents, slip and fall events, industrial accidents and product development, as well as to develop and improve industry safety standards. For instance, vehicle crash testing that employs ATDs can provide a valuable resource for helping evaluate occupant safety and response during the various phases of an accident. The design and implementation of customized experiments involving test subjects and ATDs can also provide relevant injury criteria about events for which there may be little or limited published data or information.
Andrew J. Rentschler, Ph.D., is a senior biomechanist at ARCCA specializing in the study of the forces and mechanics associated with injuries to the human body. Dr. Rentschler has also worked with the National Hockey League to research, develop and test designs to improve player safety.
Recently, I inspected and downloaded the tractor of a commercial vehicle that had been involved in an incident. The tractor had a Detroit engine, and I was able to obtain speed and braking information related to the incident from the engine’s on-board computer system. As an experienced accident reconstructionist, however, I know that “clock drift” must be considered when working with this engine’s computer system. Clock drift enables you to find errors in the ECM clock, correct times reported on DDEC Reports, and determine if a Hard Brake or Last Stop record actually occurred at the reported time of the event. After accounting for clock drift in this case, I was able to ascertain which data was relevant to the crash, causing me to rule out the two recorded Hard Brakes. By utilizing the Last Stop data, it was my determination that the truck driver was not exceeding the posted speed limit and did not stop too abruptly in front of a vehicle that was following too close.
BARRY PEAK, ACTAR, ASE, CFEI, CVFI, PI, is a mechanical engineer at ARCCA specializing in Accident Reconstruction, Crashworthiness and Failure Analysis.
Earlier this year, Dr. Brian Benda, Senior Biomechanist at ARCCA, teamed with Dr. Al Lamperti, Emeritus Professor of Anatomy at Temple University School of Medicine, to present “The Human Brain and Its Multiple Functions.” This presentation was part of the Science Week Celebration at the Free Library of Springfield Township, Montgomery County, Pennsylvania.
Dr. Benda’s presentation included interactive demonstrations with the audience that showed the various ways the brain and spinal cord control movement. Dr. Benda also discussed the many ways one can suffer brain and spinal cord injuries, the devastating consequences of such injuries, and the promise for innovative treatments and cures. He discussed the therapies he helped develop and test to improve the quality of life for young adults with spinal cord injuries and for children with cerebral palsy while a researcher at Shriners’ Hospitals for Children in Philadelphia.
Dr. Benda described the nerve stimulation system implanted in young adults suffering from paraplegia due to spinal cord injuries. This system allowed patients to control coordinated movements of their legs with hand-held computers. The stimulation system, together with crutches, allowed the patients to exercise their legs, to stand up from their wheelchairs, and to walk.
Dr. Benda also described the video game he helped develop to aid children with cerebral palsy extend and flex their ankles in a way that facilitated better walking behavior. The children controlled the video game by moving their feet back and forth. The game was programmed so that movements that closely resembled those seen during normal walking would give higher scores. The game encouraged the children to move their feet in the proper manner.
Brian Benda, PhD, is a senior biomechanist at ARCCA specializing in the study of the structural mechanics of the human body, forensic biomechanics, the study of human injury mechanisms and the interaction of humans and medical devices.
Two rollover tests were conducted, which we believe are the first dynamic rollover tests ever performed with a live human subject, and the results were compared to an actual real-world rollover crash during which an occupant of the same approximate size and in the same model vehicle sustained severe cervical injuries. The test vehicle was configured with a roll-cage and seat-mounted seatbelt incorporating a locking latch-plate at the driver’s position. The rollover tests were initiated by tipping the vehicle down an embankment, resulting in two to three vehicle rolls. Roof damage was limited by the roll-cage, and the subject was well-restrained by the seatbelt. The lap belt severely limited the vertical displacement of the body, and the subject did not sustain any significant injuries. From this research, it was concluded that:
- (1) A lap/shoulder belt restraint system with good geometry, such as an ABTS (all belts to seat) system and a locking latch-plate, are very effective in minimizing vertical head excursion during a rollover crash. By utilizing this type of restraint system during the subject rollover testing, the average vertical head displacement was limited to 11.4 mm, and the head velocity at the single helmet impact during Test 2 was 1.57m/s. This is well below injury threshold. During the tests, the live human subject did not sustain any significant injury.
- (2) The results of the live human volunteer test subject using an ABTS during a rollover event are consistent with the inverted drop testing conducted with a Hybrid?III ATD (crash test dummy) restrained in an ABTS system.
- (3) The kinematics of the live subject demonstrated considerably more head and neck motion than what was observed during previously analyzed rollover testing utilizing ATDs.
- (4) The pre-test vertical helmet clearance with the roof was only 25.4 mm. Due to the minimal roof deformation (approximately 13mm) and minimal vertical head displacement (11.4 mm), and in spite of the test subject weighing 110 kg, no impacts with the roof occurred that would introduce the potential for serious cervical injury. This demonstrates that occupants can survive rollover crashes without serious injury, even with very little initial head clearance, if vertical head excursion, head velocity, and roof crush are minimized.
Gary Whitman, BSME, Director of Crashworthiness at ARCCA, Inc., and his ARCCA colleagues, Lou D’Aulerio, Larry Sicher and Brian Benda (and with co-authors David Scott, Dennis Shanahan, and Alfred Finch), authored a paper on “Rollover Testing with Volunteer Live Human Subject”, which was accepted for publication by the International Journal of Crashworthiness. It is an honor to be associated with the courageous David Scott, who was the lead investigator and voluntary live human subject for this testing.
As an avid motorcyclist, I know that Spring is the time of year motorcycle riders look forward to. Unfortunately, in my role as an accident reconstruction expert, I see many crashes this time of year due to riders re-familiarizing themselves with their machines, motorcycles with neglected maintenance, road conditions that have deteriorated over the winter months, and other drivers who are not used to looking twice for motorcycles. View this post >