Anti-intrusion bar

An anti-intrusion bar or beam is a passive safety device, installed in most cars and other ground vehicles, which must protect passengers from side impacts.[1] Side impacts are particularly dangerous for two reasons: a) the location of impact is very close to the passenger, who can be immediately reached by the impacting vehicle; b) in many side-impact accidents, the impacting vehicle may be larger, taller, heavier, or structurally stiffer than the struck vehicle. The role of an anti-intrusion bar is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash.

Designs to counteract side impact collisions were explored as early as 1969 by General Motors,[2] and Ford was issued a patent for the technology in 1975.[3] Volvo introduced the Side Impact Protection System for its 700, 800, and 900[4] series cars in the early 1990s.[5]

Performance

The performance of a side beam is measured by several indicators. The most important are:

  • the Specific Energy Absorption (SEA), which measures the amount of energy absorbed per unit mass;
  • and the energy efficiency η, which is the ratio between the mean load and the peak load transmitted to the vehicle during the impact.

Furthermore:

  • the amount of intrusion, for a given energy, must be as small as possible;
  • the maximum depth or diameter of the bar must be reasonably small, as the vehicle door does not generally allow much space;
  • the cost of the member must be reasonably small.

Typical design

The anti-intrusion beams commonly span the length of the door at about a vertical midsection of the door. As the figure shows, the typical profiles can be open or closed (tubular, usually with a round cross section).

Some examples of anti-intrusion bars for cars

They are conventionally made by stamping or hydroforming processes. When the cross section is closed, the tubes can be used as-received. In the scientific and technical literature, some unconventional designs have been proposed.[6]

Typical materials

The anti-intrusion bars are generally made of high strength steels.[7] However, some studies indicate that stainless steel 304 might be a better choice, because of its larger plastic field and a larger amount of potentially absorbed energy before fracture.[8] In the scientific and technical literature, some unconventional material combinations have been proposed, too, e.g. based on metal foam filled tubes[9] or composite materials.[10]

See also

References
  1. "On the Safe Side" (PDF). Crash Test Technology International. May 2009.
  2. Hedeen, C. E.; Campbell, D. D. (1969-02-01). "Side Impact Structures 690003". 1969 International Automotive Engineering Congress and Exposition. SAE International. doi:10.4271/690003.
  3. Ford Motor Company. "Side door intrusion protection (US3868796A)". Google Patents.
  4. "Volvo '92: New model, new engine and a unique safety innovation". new.volvocars.com (Press release). Rockleigh, New Jersey: Volvo Cars of North America. 1992. Archived from the original on 2017-02-06. Retrieved 2017-07-07.
  5. "R&D milestones of the Volvo Group". www.volvogroup.com. Volvo Group. 2011. Archived from the original on 2011-06-16. Retrieved 2017-07-07.
  6. "Vehicle anti intrusion bar by Bond, Sam – AU 1999065514".
  7. High Strength Steel for Automotive Safety Components Archived December 20, 2011, at the Wayback Machine
  8. Coppola, T.; Picella, P.; Segala, S.; Migliorini, R.; Capelli, F. "National Benchmark on Material Performance in Anti-Intrusion Beams" (PDF). Archived (PDF) from the original on June 29, 2023.
  9. Strano, M.; Mussi, V.; Monno, M. (2010). "Non-conventional technologies for the manufacturing of anti-intrusion bars". International Journal of Material Forming. 3: 1111–1114. doi:10.1007/s12289-010-0966-y. S2CID 136670060.
  10. "Anti-intrusion beam for vehicle door assembly - US Patent 7819462 Description". www.patentstorm.us. Archived from the original on 21 April 2013. Retrieved 6 June 2022.
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