Jonathan Newell finds out how software modelling of crash testing can now go beyond the outer human shell to the vital organs beneath.
The automotive industry has made significant strides in preventing broken bones and piercing injuries caused by protruding objects and flying debris during a vehicle impact but addressing the “second impact”, when the internal organs collide with the walls of the body, remains a challenge.
To help designers come up with ways of reducing the likelihood of internal injuries, global car manufacturer Toyota released its THUMS (Total Human Model for Safety) software, which included the ability to model internal organs from version 4 released in 2010.
Now the company has gone a stage further and added three child models to the existing three adult models. Representing 10, 6 and 3-year-old children, the models have two versions each to represent car passengers and pedestrians. The protection of pedestrians is now an important factor in receiving the coveted Five-Star award from the European New Car Assessment Programme (Euro NCAP).
Developed as part of a collaborative project involving Wayne State University, the University of Michigan and Toyota’s Collaborative Safety Research Centre in Ann Arbor, Michigan, the software contains detailed models of the brain as well as the placement and interaction of internal organs within the body. The muscular system of the body is also simulated enabling the model to perform realistic bracing in the moment before impact.
Preparing for crash tests
Preparing for the NCAP organisations’ crash tests is a long, painstaking and expensive process for car manufacturers and one which often involves destroying prototypes and final products. By simulating an Anthropomorphic Test Device (ATD or crash test dummy) in software, time and money can be saved whilst preparations take place. This is particularly important, since the NCAPs are continuously making their specifications more stringent and changing the criteria which need to be met to reach the various star ratings.
We spoke to Andrew Miller, the Chief Operating Officer at vehicle engineering and test organisation, Thatcham Research as well as the current Chairman of the Board of Euro NCAP about future plans for improved vehicle safety and the role such software can play in meeting the planned changes in criteria.
He told us that Euro NCAP will be developing a new 2021-25 roadmap shortly and this will contain future developments of passive safety assessments. Euro NCAP will be reviewing the latest design practice including simulation modelling and will consider how this might be used to further refine assessment processes.
“Experience to date has shown that simulation modelling is only as good as the detailed mathematical models upon which it is built, which by nature are approximations of real-world engineering characteristics. In the crash tests Euro NCAP conducts, expected and actual crash performance sometimes differs significantly, especially in the complex physical interaction of the ATDs and the restraint systems,” he told us. For this reason, Euro NCAP will be continuing to conduct real life crash tests for the foreseeable future.
The correlation between real crash test results and the predictions made within the software modelling environment is under constant scrutiny by both Toyota and the vehicle and sub-system manufacturers that use it. The wealth of data collected during NCAP testing serves a useful secondary purpose in refining the modelling to achieve greater accuracy.
Miller believes that there is certainly a significant role that software simulation of ATDs plays in improving the safety of cars.
“Simulation modelling of crash performance is an excellent design tool for manufacturers as it allows them to assess a very wide range of potential impact types and estimate the impact of these on a wide range of occupant types. Euro NCAP therefore approves strongly of this design practice,” he told us.