Crash tests

Friday, May 16, 2014

Tags :  testing

Although it is not often remembered these days, 1985 marked a seminal moment in the advancement of driver safety in Formula One. It was the year that saw the introduction of a mandatory frontal crash test for cars, and followed on the heels of a number of other safety advances in the preceding years, not least the introduction of a compulsory reinforced survival cell around the driver in 1981.

Since that first round of testing, the crash tests a chassis must pass before it is accepted for competition have grown considerably in number and complexity. Meeting the requirements of these tests, while also building a car that is as light and tightly packaged as possible, is a stern test for teams’ engineers. Cars must now pass two frontal impact tests, one that assesses the frontal crash structure and another that covers the integrity of the main chassis monocoque. The monocoque must also undergo various rear and side impact tests, as well as impact tests on the roll structure, and various static load tests on areas such as the monocoque sides and cockpit surround. The standards for the frontal tests give an insight into the severity of the tests as a whole.

For the first test, the frontal crash structure is fitted to the monocoque, which must be fitted with a fuel tank filled with water and a 75 kg test dummy. This is then attached to a sled, which has an all-up weight (including the monocoque) of 780 kg. The sled is fired at a solid wall at a velocity of at least 15 m/s (33.6 mph). It is worth noting here that the standard safety rating tests for roadcars feature a similar velocity, but use a deformable barrier (not to mention the fact that roadcars have a much larger frontal volume available for energy absorption). As the monocoque structure impacts the wall, accelerometers record the level of deceleration using a high-speed data acquisition system, and the test is only passed if the levels of deceleration fall within the FIA requirements.

The requirements are as follows:

a) The peak deceleration over the first 150 mm of deformation does not exceed 10 g.

b) The peak deceleration over the first 60 kJ energy absorption does not exceed 20 g.

c) The average deceleration of the sled does not exceed 40 g.

d) The peak deceleration in the chest of the dummy does not exceed 60 g for more than a cumulative 3 ms, this being the resultant of data from three axes.

Or:

a) The peak force over the first 150 mm of deformation does not exceed 75 kN.

b) The peak force over the first 60 kJ energy absorption does not exceed 150 kN.

c) The average deceleration of the sled does not exceed 40 g.

d) The peak deceleration in the chest of the dummy does not exceed 60 g for more than a cumulative 3 ms, this being the resultant of data from three axes.

During this test, the condition of the monocoque, particularly areas such as the safety belt mountings, is also monitored to ensure they do not suffer damage or deformation.

The second frontal test is to account for the fact that it is perfectly feasible that a car will suffer multiple impacts during a crash. It is therefore important that the driver is still protected, even if the front crash structure is no longer present.

For the second test, the monocoque without its front crash structure is fitted to the sled, with the crash structure replaced by an aluminium plate 50 mm thick. This time though the sled is fired at a deformable impact wall, which must resist a minimum load of 60 kN at the same 15 m/s. To obtain a pass, the monocoque must be able to resist the resulting impact with no damage to the survival cell, with particular attention again given to the safety belt mountings.

The requirement for the multitude of other tests that are undertaken are no less stringent. It is therefore no surprise that drivers are now usually able to walk away from accidents that 20 years ago would have held much grimmer consequences. Passing the tests may present its fair share of headaches to teams’ engineers, but the fact that there have been no driver fatalities in a GP since Senna and Ratzenberger in 1994 shows that they are more than worth the effort. 

Written by Lawrence Butcher

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