Test Exam

Question 1

How does a seat belt system with a pretensioner and load limiter reduce injury risks?

Answer 1

Pretensioners remove slack for earlier restraint, and load limiters reduce chest forces by controlled belt payout during high loads.

Question 2

What are seven important properties of a crash test dummy?

Answer 2

Anthropometry
Bio-fidelity
repeatability
reproducibility
sensitivity
instrumentality
durability

Question 3

What should determine the strength of the compartment in a small car during frontal impacts?

Answer 3

The back-up structure must withstand loads, protect occupants, and absorb crash energy while being compatible with other vehicles.

Question 4

What is the most common car body architecture, and why?

Answer 4

Unibody construction, for its balance of weight, strength, cost-efficiency, and energy absorption capabilities.

Question 5

What two material parameters influence the maximum time step in explicit time integration?

Answer 5

Density (ρ) and Elastic Modulus (E).

Question 6

What happens if you use longer time steps in explicit time integration?

Answer 6

The solution becomes numerically unstable or inaccurate.

Question 7

Why are very short time steps beneficial in explicit FE codes?

Answer 7

They accurately capture high-frequency dynamic responses during crash events.

Question 8

What is the difference between model verification and validation?

Answer 8

Verification ensures correct implementation; validation ensures the model represents real-world behaviors.

Question 9

What are three principal thorax injury mechanisms in crashes? + typical loading situations

Answer 9

• Elastic A frontal collision where the thorax is compressed by the seat belt or airbag, causing temporary deformation without permanent damage. The chest wall absorbs the load elastically, and the deformation rebounds.
• Viscous A high-speed crash where the chest experiences rapid compression due to the seat belt. The velocity of the deformation creates viscous forces within the soft tissues, leading to potential organ injury like lung or heart damage.
• inertial During a side impact, the sudden movement of the body causes internal organs to continue moving due to inertia, leading to shear forces between the organs and the ribcage. This can cause tearing or displacement of internal structures, such as aortic injuries or diaphragm rupture.

Question 10

Compare full vehicle tests and sled tests in crash testing.

Answer 10

Full vehicle tests assess the whole system but are costly; sled tests are cost-effective and repeatable but limited to subsystems.

Question 11

What are the advantages of accelerating sled tests?

Answer 11

In acceleration test the dummy can’t slip away doing the test setup. Less space.

Question 12

How do EuroNCAP and FMVSS frontal test setups differ?

Answer 12

EuroNCAP uses offset frontal crashes (more realistic);
FMVSS uses full-width crashes (uniform load distribution).

Question 13

What are the challenges in FMVSS tests for EuroNCAP-optimized cars, and how can they be addressed?

Answer 13

Less energy absorbed by ridged barrier. Car needs to absorb more in crumple zone

EURO Requires a strong front structure and a strong back-up structure!
US A strong front structure might cause a pulse problem!

Question 14

Define “Regulation” and its purpose in crash safety.

Answer 14

Regulations set legal safety standards to reduce crash-related injuries and fatalities.

Question 15

What is “Harmonization” in crash safety testing?

Answer 15

Aligning global safety testing standards to simplify compliance and improve universal safety.

Question 16

Explain “Certification” and “Compliance testing” and their regional differences.

Answer 16

Certification is self-declaration (USA), while compliance testing is independent verification (Europe).