I-CAR Structural key terms

The maximum stress a material can carry while being pulled apart before it fractures, usually reported in megapascals and used to classify steels by grade.

The stress level at which a material stops behaving elastically and begins to deform permanently; a key indicator of how a panel will respond to a pull.

A family of steels with carefully engineered microstructures, such as dual-phase and martensitic grades, that deliver high strength at relatively low thickness and demand specific heat and straightening limits.

Steels at the top of the strength range, roughly 780 MPa and above, which are highly sensitive to heat and often require sectioning rather than straightening.

An increase in strength that occurs when paint-curing heat allows carbon atoms to lock dislocations in certain steels; reheating or welding can alter this condition.

The band of base metal next to a weld or heat application whose microstructure and strength change from the thermal cycle, even though it did not melt.

A very high-strength steel used in reinforcements such as B-pillars; it is typically hot-stamped and should not be heated, welded in the field, or straightened in most repair procedures.

The elastic recovery of metal that causes it to move back toward its original shape after a bending or pulling force is released, complicating accurate straightening.

Pulling a structure slightly beyond its original position so that when springback occurs the panel relaxes back to the correct dimension.

A process of comparing vehicle reference points in length, width, and height to a published datum specification to identify and quantify structural movement.

An imaginary horizontal reference surface from which vertical height measurements are taken on a vehicle; it is not usually a physical part of the car.

A specific locating hole, bolt, or feature on the body identified by the manufacturer whose position is measured to confirm structural alignment.

A locating and holding device that secures a panel or structural section in a fixed position during measuring, alignment, or welding so dimensions stay stable.

A heavy anchoring and pulling system with a flat bed and towers used to hold a vehicle and apply controlled straightening forces to its structure.

A location on the vehicle or rack where holding devices are attached to resist pulling force and keep the vehicle stable during straightening.

Applying controlled, low-level force or heat to reduce internal stress built up in a panel or structure during straightening or welding.

A welding process that joins overlapping panels by passing current through electrodes while clamping them, creating a fused nugget at the interface without filler metal.

The fused, lens-shaped zone of metal at the interface of two panels created by a spot weld; its size and penetration indicate weld quality.

Current that bypasses the intended weld location and travels through an adjacent existing weld or grounded path, reducing current density at the new weld.

A conductive coating applied to mating surfaces before welding that limits corrosion while still allowing current to flow and a sound nugget to form.

Gas metal arc welding in which a continuously fed wire electrode melts into the joint while shielding gas protects the molten pool; widely used for steel sectioning joints.

A weld made by filling a hole punched or drilled in an outer panel so the weld fuses to the panel beneath, often used where a factory spot weld cannot be reproduced.

A series of short, spaced welds used to control heat input and distortion when a continuous weld is not required or would damage the panel.

A planned cut and overlap or butt joint used to replace part of a panel rather than the whole, positioned per manufacturer guidance to preserve structural strength.

A steel insert placed behind a sectioning joint to support the weld, control burn-through, and restore strength across the joint.

A sectioning method where panels meet edge to edge and a backing insert behind the seam supports full-penetration welding to restore original strength.

Removing a damaged panel and installing a new or salvage panel by separating factory welds, fitting, welding or bonding, and restoring corrosion protection.

A specialized drill bit that cuts through the outer panel's spot weld without destroying the underlying panel, allowing clean separation at factory joints.

Joining panels with a structural adhesive that cures to transfer load across the joint, often combined with welds or rivets and requiring proper surface preparation.

A hybrid joining method that combines structural adhesive with rivets, which hold the panels in alignment while the adhesive cures and share load afterward.

A fastener driven through the top panel that flares into the lower panel without a pre-drilled hole, commonly used on aluminum and mixed-material assemblies.

A partial-panel replacement joint made with structural adhesive, sometimes with rivets, used where heat or welding is restricted by the panel material.

Corrosion accelerated when two dissimilar metals, such as steel and aluminum, are joined in the presence of an electrolyte; isolation materials and coatings are required at the interface.

A coating, tape, or washer placed between dissimilar metals to prevent electrical contact and slow galvanic corrosion at a joint.

A creeping protective coating sprayed into enclosed box sections and pillars after repair to restore corrosion protection on interior surfaces that paint cannot reach.

A flexible coating applied over joined panel seams to keep water out and duplicate the factory appearance and corrosion protection.

A coating with high zinc content applied to bare or welded steel to sacrificially protect the surface before topcoat, often used on weld zones.

The designed behavior of a vehicle structure that absorbs and redirects crash forces through crush zones and load paths to protect the occupant compartment.

A front or rear structural section engineered to deform progressively and absorb impact energy before forces reach the passenger cabin.

The route through which forces travel through a vehicle's structure, such as rails, pillars, and rockers; repairs must preserve its continuity.