Anti-intrusion Bar
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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. 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 In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
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 General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
, and Ford was issued a patent for the technology in 1975.
Volvo The Volvo Group (; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distribution and sale of truck ...
introduced the Side Impact Protection System for its 700, 800, and 900 series cars in the early 1990s.


Performance

The
performance A performance is an act or process of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Performance has evolved glo ...
of a side beam is measured by several indicators. The most important are: * the
Specific Energy Specific energy or massic energy is energy per unit mass. It is also sometimes called gravimetric energy density, which is not to be confused with energy density, which is defined as energy per unit volume. It is used to quantify, for example, st ...
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). They are conventionally made by stamping or
hydroforming Hydroforming is a means of shaping ductile metals such as aluminium, brass, low alloy steel, and stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of cost-effective hydroforming is the automot ...
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.


Typical materials

The anti-intrusion bars are generally made of high strength steels. However, some studies indicate that
stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...
304 might be a better choice, because of its larger plastic field and a larger amount of potentially absorbed energy before fracture. In the scientific and technical literature, some unconventional material combinations have been proposed, too, e.g. based on
metal foam Regular foamed aluminium In materials science, a metal foam is a material or structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) ...
filled tubes or composite materials.


See also

*
List of auto parts This is a list of auto parts, which are manufactured components of automobiles. This list reflects both fossil-fueled cars (using internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the c ...


References

{{Reflist Vehicle safety technologies Auto parts Car doors