CHILDREN'S PROTOTYPE VEHICLE IMPACT TESTS

Felisa Guzmán

Researchers from the Escuela Superior de Ingeniería Mecánica y Eléctrica (ESIME), Unidad Zacatenco, led by Dr. Christopher René Torres San Miguel, developed a prototype of a low-cost infant dummy (anthropomorphic dummy) for vehicle impact tests on people with special needs and to generate research to improve child restraint systems.

Using fused deposition modeling (3D printing) with screwed joints and a special silicone that mimics the texture, weight, and deformation of human skin, specialists from the Applied Biomechanics Laboratory at ESIME Zacatenco created a Q3 mannequin, corresponding to a three-year-old infant, whose lower limbs were modified to simulate a bone-degenerative disease to evaluate the damage it would suffer in the event of a collision.

With this technological innovation project, it is possible to undertake tests of a vehicle crash, safety in child restraint systems, and car deformation, to reproduce the impact that each variable represents in the body of a passenger and even for motor vehicle insurance companies to know with certainty which parts should be restored or changed in a collision.

These studies lay the groundwork for the creation of a national evaluation center at the Polytechnic that would benefit the Automotive Systems Engineering and Mechanical Engineering programs in the training of human resources of excellence in this area of the automotive sector. "It is an excellent opportunity niche. Even though Mexico ranks seventh in the world in vehicle manufacturing, it only assembles vehicles and passive safety tests are carried out in the United States or European countries," said the expert.

Mannequin Q3

Impact testing in the automotive industry has been a fundamental tool in transportation safety research. However, describing the in-car collision phenomenon in infants is more complex because the center of gravity is different from that of an adult.

Although there are different types of tests, it is essential to develop tools that help generate more research on safety for people with special needs. In this sense, he developed the prototype of a dummy that simulated osteogenesis imperfecta or glass bones to perform specific tests.

In collaboration with Ph.D. students in Mechanical Engineering, Alejandro Cuautle Estrada, Mario Alberto Grave Capistrán, and José Luis Torres Ariza, Torres San Miguel achieved a prototype with a cost 90 percent lower than those existing on the market. "We generated a mannequin with a new methodology to which it is possible to adapt some type of injury or bone deformation to carry out tests that allow us to know how to transport these users safely," said Torres San Miguel.

Test Bank

At ESIME Zacatenco they designed a test bench consisting of a ramp with a length of two meters, where a mobile platform supports a chair with sufficient dimensions to place the prototype of the dummy developed.

The mechanism has an angle of inclination of 15 degrees that with the two-meter run, and a weight of 15 kilograms of the mobile platform with the dummy installed generates a final impact speed equivalent to 7.1 km/h. To increase the speed they used a pair of elastic bands to produce a final impact speed of 25 km/h.

The specialists considered factors influencing the outcome of each experiment such as the total mass of the launch platform, the position of the dummy, the stretch of the rubber bands, and the lubrication of the rails in the impact mechanism.

As part of the instrumentation, the Biomechanics Laboratory uses accelerometers capable of measuring with excellent precision the impacts on the neck and thorax of the mannequin.

"They are wired to the computer, through a data acquisition device and through a Human Machine Interface that helps decode the signals sent from the sensors to the computer. Using a National Instruments computer program, the voltage signals are converted into an acceleration or g-force measurement, visualizing the information in real-time," explained the ESIME Zacatenco academic.

With 50 percent progress in the project and the possibility of providing data on what happens at low speeds in a real collision, the IPN scientists conduct the impact measurements videometrically with a GoPro action camera to obtain a graph of the speeds reached during the crash, the accelerations and the position of the mannequin.

"In the software you can see the impact trajectory of each member of the dummy, clearly observing the kinematic behavior of each of its parts," said the doctor in mechanical engineering.

These studies broaden the panorama of automotive engineering in Mexico, as well as that of biomechanics applied to passenger safety. For this reason, the polytechnic researcher expressed his satisfaction with training new cadres of professionals who contribute their knowledge to support innovation in this industrial sector in Mexico.