Increasing Child Safety Using Simulation for Car Seat Design
The worst situation any parent could imagine is the loss of a child. Every year in Europe alone, 400 children die as a result of motor vehicle accidents and another 2,800 suffer serious injuries causing permanent disability .
The forces at play in these accidents can be enormous and quite often the resulting injuries sustained by children are greater than those sustained by the adults in the vehicle. How can the crash forces on children be reduced and safety increased? By tackling this question, the people at Malaika have designed the world’s first range of child car seats that will surpass every international safety standard, effectively raising the bar for child vehicle safety.
Malaika (translated as baby or angel in Swahili), founded in 2012, initially set out to create a more lightweight, user-friendly car seat. They quickly broadened their approach to include safety features. “We believe that children in cars should have the highest possible level of safety that technology permits. We don’t feel like we need to be satisfied with what we have today, we actually want to deliver something that makes it better,” declared one of the company’s founders and current Chief Operating Officer, Karl Hearst.
Modelling the System
To meet such an extreme design challenge, the engineers at Malaika implemented rigorous product testing and design verification procedures at both the component-level and system-level. The SimScale platform has been a requisite part of this process and a series of component simulations have been done to validate the structural integrity of the primary ISOfix connection to the main chassis and the adjustment rack.
As a supplement to physical testing, structural simulations were conducted based on worst case scenarios to a force of 3600 N .
The primary ISOfix connector is a steel component that attaches the adjustment bar on the base of the car seat to a fixed anchorage point in the body of the vehicle. During a vehicle crash, this is a critical component for ensuring that the car seat remains in place.
The impact force is applied to the 4 bolts at the base of the connector. There is sliding contact between the adjustment bar (which is fixed) and the circular connector head. A secondary rim has been added to the circular connector head to increase the rigidity and strength of the part.
High-stress zones are present on the circular connector head and near the bolt holes. These stresses do not exceed the yield strength of the material meaning that this connecting piece can withstand worst case loading scenarios.
The greatest displacements are seen at the base of the connector where the forces are applied. These are, however, very small and do not introduce design concerns.
Length Adjustment Rack
The length adjustment rack is part of the base of the car seat and consists of a set of grooves into which steel teeth from the adjustment bar fit. Sliding occurs between the grooves and teeth when a force is applied. There are significant stresses at the locations of contact under the worst case loading conditions.
Under these simulation conditions, the highest stresses occurred at the middle tooth. These stresses exceeded the tensile strength of steel signifying that material yielding occurs. Locating these zones of yielding provides information about where additional design considerations should be made before physical testing is done.
Although the final stages of the design are still in progress, it can be seen that simulation with SimScale and physical testing complement each other perfectly, putting Malaika at the forefront of child vehicle safety.
1. European Commission CASPER Project (http://casper-project.eu/)
2. For this test, a full system force of 7200 N was applied ([18 kg child + 15 kg child restraining system]*22g). For components, due to symmetry, a load of 3600 N was applied. Current testing has increased this symmetric load to 6000 N.
3. Images are courtesy of Malaika Ltd.