Automotive E-ssentials

Vehicle safety testing at component level: interiors testing

Is it safe in a vehicle even if I have an accident other than those mentioned in the legislation or the "Euro NCAP" recommendations? For example, what if the specific kinematics of the vehicle during an accident result in my head coming into contact with something other than an airbag? What about fellow passengers in the second or third row of seats?

How many times have questions like this had consequences for drivers and passengers?

During the development of passive car safety, the number of mandatory tests increased significantly in response to accident statistics and injury severity. Moving on from the original impact tests, which mainly addressed body structure and deformation of the survival space, we advanced to a whole matrix of tests that varied in terms of direction and speed of impact, offset size, barrier types and manikin size. However, none of us want to be seriously injured inside a vehicle just because the impact was not included in the statistically significant accidents and the movement of the vehicle during the impact differed from the movement in the prescribed crash tests.

In general, tests involve various impactors (simulating a person’s head or entire torso). We shoot these impactors against different parts of the interior e.g. against the steering wheel on the steering column, the dashboard, pillar trim or headrests and to establish how "friendly" the interior is to humans. Friendliness here means the ability of the interior to absorb the impact energy of the impactor without sharp edges, extreme deceleration levels as measured by accelerometers, etc.

However, it is important to note that the following test methods deal with the friendliness of overall vehicle interiors at normal impact speeds rather than accidents at extremely high speeds or undisciplined passengers who fail to use seat belts. They relate mainly to ECE regulations and the FMVSS, the dynamic testing part of which is covered by new dynamic test conditions in our laboratory.

ECE 12 Protection of the driver against the steering mechanism in the event of impact (FMVSS203)

ECE 17 Strength of seats, their anchorage and head restraints

ECE 21 Interior Fittings (FMVSS201)

ECE 25 Head restraints

ECE 80 Strength of seats and their anchorage in buses

New workplace in the strength testing laboratory

As the tests include dynamic processes, the workplace is physically separated from the rest of the building. It is a compact unit with a control room and a customer room providing a safe and comfortable facility for our customers. The design of the workplace prioritises safety, e.g. all doors are secured against being opened when tests are under way so that no-one can enter the test area.

Pendulum

• The pendulum replaces a similar device installed in 2008. The replacement was needed because spare parts were no longer available for the control electronics of the old device and modernisation did not make sense economically. Compared to the old device, the new one has higher accuracy and repeatability of impact speed and systems for triggering external devices (e.g. high-speed cameras) and deploying airbags.
• The device is used during energy absorption tests on instrument panels pursuant to ECE Regulation 21 (FMVSS201) and on seats according to ECE Regulations 17, 25 and 80.
• Under ECE 21 the head impact zone comprises all the non-glazed surfaces of the interior of a vehicle which are capable of entering into static contact with a spherical head 165 mm in diameter which is an integral part of a measuring apparatus whose dimensions from the pivotal point of the hip to the top of the head is continuously adjustable between 736 mm and 840 mm.
• We can also investigate the head impact zone dynamically through vehicle impact tests, sled tests (DYCOT laboratory) or simulated impact tests. The movement of the passengers is checked by a deceleration effect based on the deceleration time diagram specified in ECE Regulation 16 (change of speed from 50 km/h) on a family of manikins (5% adult female, 50% and 95% adult male) and by inducing a forward movement of the manikins that corresponds to the movement of manikins during real frontal impact tests. The direction of forward movement of the manikins is considered satisfactory if the central axis of a test object with normal bodywork covers a range of ± 18º from the longitudinal central axis of the sled. Normally it is sufficient to test at 0º, +18º and -18º

Description of the device:

The inverted pendulum is mounted on ball bearings and driven by a pneumatic actuator. The pendulum is equipped with an automatic brake to prevent secondary impacts. The pendulum’s position in relation to the test sample is adjustable in three axes and the pendulum rotates around the Z-axis. The pendulum’s length can be adjusted continuously. The reduced mass at the centre of rotation corresponds to 6.8 kg.

Device parameters:

Maximum impact speed: 32 km/h

Maximum kinetic energy: 180 J

Impact speed accuracy: ± 0.1 km/h

Pendulum length adjustment range: 736÷840 mm

Evaluation of tests:

In the energy absorption test, the deceleration of the impactor may not exceed 80 g continuously for more than 3 milliseconds. The average of the data from the two accelerometers shall be recorded as the deceleration value. Impact speed is 24.1 km/h according to ECE R 21.

Linear impactor

• This is a new device – supplementing the pendulum (some customers require a linear impactor instead of a pendulum for tests on head restraints under ECE 17) and replacing the body block test device from 1973.
• We also use the linear impactor for head form tests and body block tests on steering wheels according to the ECE 12 and FMVSS203 regulations and tests on the energy absorption of seats according to ECE 17, 25 and 80.

Device parameters:

Max impact speed: 40 km/h

Max. impactor weight: 40 kg

Max. kinetic energy: 1300 J

Impact speed accuracy: ± 0.15 km/h

Device description:

The device consists of a pneumatic actuator and one type of guideline for guided (head) and free-flying impactors (e.g. body block). The actuator with the guide is mounted in a frame that allows the impactor to be directed against the test sample in three axes.

Linear impactor - head impact

The test is similar to that of the pendulum test.

The test evaluation is the same as for the pendulum with the exception of steering wheel tests (R12), where the deceleration must not exceed 80 g cumulatively for more than 3 ms.

Linear impactor – body block

The body block must hit the steering wheel at a speed of 24.1 km/h +1.2/- 0 km/h.

When the body block hits the steering wheel at a relative speed of 24.1 km/h (15 mph), the force applied to the body block by the steering control shall not exceed 11,11 kN.

A measurement is taken of the maximum force applied to the body block as a result of the impact on the steering control in a horizontal direction parallel to the longitudinal axis of the vehicle. This force can be measured directly (with load transducers inserted on the steering system) or indirectly (by a calculation based on the acceleration values recorded during the test).

Accelerometers inserted into the body block: Two single-axis accelerometers are symmetrically inserted into the transverse plane of the centre of gravity of the body block. The channel amplitude class shall be 60 g and the channel frequency class 180 Hz.

Both devices (the pendulum and the linear impactor) share control electronics and software, thus allowing considerable savings to be made.

As these are component tests, we can detect any major structural deficiencies in the early stages of development and test the compliance of components with specific product requirements long before a complete prototype body is available, for example.

As a result, there will be no more unpleasant surprises in sled tests and crash tests with these components in terms of energy absorption, sharp edges or component destruction, and there will be no need to repeat these costly tests.

The tests are conducted in our Vehicle Safety and Electronics Lab in Mlada Boleslav- Bezdecin, in Czech Republic

For more information please contact our local expert for strength tests, Jiří Vojtíšek