How steel reinforcements protect passengers in a crash

Over the last six decades, most mass-produced vehicle bodies were manufactured from stamped steel components. Steel reinforcements play a crucial role in protecting passengers during a crash by absorbing impact energy. During a crash, these reinforcements distribute the kinetic energy generated by the collision. By doing so, they reduce the force transferred to the occupants. Steel reinforcements enhance the overall structural strength of the vehicle, maintaining its shape and integrity during a collision. This helps prevent the cabin from collapsing or deforming excessively, thereby protecting the occupants.

A highly malleable steel sheet has been created through a process that involves refining the grain structure of ferrite. This is achieved by subjecting the steel to high-reduction hot rolling at low temperatures, followed by immediate accelerated cooling after the hot rolling phase. Additional steps include high-reduction cold rolling and high-temperature annealing. The resulting steel sheet plays a significant role in reducing production costs by saving on metal die expenses and eliminating the need for joining processes. This is accomplished through the integrated forming of intricate parts.

In vehicles, these reinforcements, often in the form of high-strength steel, are strategically placed in key areas like the frame, pillars, and door beams.

Crumple zones: steel reinforcements are also designed to create specific crumple zones in a vehicle. These zones, typically at the front and rear, deform in a controlled manner, effectively dissipating the energy of the impact and extending the time of the collision. This gradual deceleration reduces the forces experienced by the passengers inside the cabin. To make car crash protection better, scientists wrap the mild steel parts in a special material called fibre-reinforced composite. They tested two types of this material, carbon/epoxy and e-glass/epoxy, by changing how they wrapped it around metal structures. The goal is to find the most effective combination that maximises the absorption of kinetic energy during a crash, ultimately enhancing the safety of passengers in transportation structures.

Occupant compartment protection: the reinforcements help in maintaining the integrity of the passenger compartment, preventing intrusion from external objects. This protects the occupants from being directly impacted by objects entering the cabin during a crash.

Door beams: Door impact beams are reinforcement members installed in car doors to absorb the kinetic energy of a side collision. They are important in cars because they help to reduce damage to passengers in the passenger compartment, therefore reducing the risk of injury and death in side collisions. Steel tubes are increasingly being used in making door impact beams because they offer weight savings over traditional high-strength steel sheets. When making door impact beams, the outside diameter of the tube depends on the space available in the door, and its wall thickness on the necessary bending load and absorbed energy. The deformation behaviour of door impact beams made of steel tubes is divided into three steps: cross-sectional flattening, plastic collapse, and circumferential buckling. Steel tubes capable of absorbing high energy are a better option for making door impact beams because of their lightweight and high strength.

B-pillars: the B-pillars, located between the front and rear doors on the sides of the vehicle, often contain high-strength steel. They provide structural support and help maintain the integrity of the roof in the event of a rollover or side collision. Hot formed steels are used in various critical automotive components B-pillar reinforcements. In the case of B-pillar reinforcements and similar components, manufacturers employ various strategies:

Welding energy absorbing materials: High-strength low alloy (HSLA) steels or Advanced High-Strength Steels (AHSS) are welded to provide the necessary energy absorption. Some welding processes can create a heat-affected zone with altered material properties. These minimise the creation of brittle zones that could compromise the material's energy-absorbing characteristics.

Thickness alterations: The thickness in energy-absorbing areas is often reduced to reinforce them with conventional high-strength or advanced high-strength steels.

Reinforced frame: the vehicle's frame or chassis is reinforced with high-strength steel, providing the overall structural strength necessary to maintain the vehicle's integrity during various types of crashes. Other parts like cross members are horizontal reinforcements that connect the vehicle's frame or chassis, enhancing overall rigidity and structural integrity.

Roof reinforcements: steel reinforcements are integrated into the roof structure to maintain its integrity in the event of a rollover accident, preventing the roof from collapsing and protecting the occupants.

Sill reinforcements: these reinforcements are along the bottom edge of the vehicle's body. They work in conjunction with other safety features such as airbags, crumple zones, and seatbelt systems. Sill reinforcements add rigidity to the vehicle's chassis and prevent intrusion into the passenger compartment during a side impact.