An anti-intrusion bar or beam is a

passive safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design ...

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 energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...

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, and

Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...

was issued a patent for the technology in 1975.

Volvo The Volvo Group ( sv, Volvokoncernen; 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, distributio ...

introduced the

Side Impact Protection System Side Impact Protection System (SIPS) is a passive safety system in an automobile to protect against injury in a side collision, developed by Volvo Cars. History SIPS was first introduced in 1991 for the Volvo 700, 900 and 850 series cars of mod ...

for its 700, 800, and 900 series cars in the early 1990s.

Performance

The performance 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, sto ...

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). Anti-intrusion bars

They are conventionally made by stamping or

hydroforming Hydroforming is a cost-effective way 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 hydroforming is the automotiv ...

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 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 A metal foam is a cellular 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) or interconnected (open-c ...

filled tubes or composite materials.

References

{{Reflist Vehicle safety technologies Auto parts Car doors