ASE B4 Structural Analysis & Damage Repair key terms

A vehicle design in which the floor pan, rails, and body panels are welded together into one load-bearing shell that carries suspension loads and absorbs collision energy.

A design in which a heavy separate steel frame supports the engine, transmission, and suspension, and the body shell is bolted to it through rubber insulators.

A long boxed or channel-shaped steel beam running front to rear that forms the main load path of a full frame or the lower backbone of a unibody.

The structural sill below the doors, joining the floor pan to the front and rear body sections; it is a major longitudinal strength member and a common corrosion area.

A front or rear structure engineered to collapse in a controlled, accordion-like way during a collision, absorbing energy so less of it reaches the passenger compartment.

A reinforced housing that receives the top of a MacPherson strut and feeds suspension loads into the body; its exact position directly affects wheel alignment angles.

Hot-stamped or specially processed steel with tensile strength often above 1,000 MPa, used in occupant-protection areas; manufacturers usually forbid heat straightening and unrestricted sectioning of it.

The vehicle maker's published document giving dimensions, materials, weld schedules, sectioning locations, and approved procedures that govern every structural repair on that model.

An imaginary horizontal reference surface defined by the manufacturer from which the vertical height dimensions in the body measurement chart are calculated.

An imaginary vertical plane that divides the vehicle into matching left and right halves and serves as the reference for side-to-side and sway measurements.

A specific hole, seam, bolt head, or stamped feature whose published location is used as a measuring reference to judge whether the structure has moved.

A hand-held measuring tool with two adjustable pointers used to compare the distance between two points, often diagonals, against the specification chart.

A bench-mounted or portable computer system that uses targets, cameras, or arms to compare many control points with OEM specifications in length, width, and height at once.

Comparing left and right side readings against the centerline; matching values indicate the structure is centered, while a mismatch shows one side has shifted.

A condition in which the frame or body is pushed out of square, with one side displaced forward and the other rearward, producing unequal diagonal measurements.

Shortening of a rail or structural member caused by a direct end-on impact, leaving the metal compressed and the overall length below specification.

A sideways shift of the frame or body, usually from a side impact, revealed by both sides reading off-center in the same direction.

A condition in which one section of the structure is rotated out of its normal plane relative to the rest, so matched left and right heights no longer agree.

Applying controlled hydraulic force, with the vehicle anchored and measured, to pull a damaged structure back within the manufacturer's dimensional tolerances.

Using a ram, chains, and clamps to apply force in a chosen direction; pulls are made in small increments with measurements taken after each one to avoid over-pulling.

Applying localized heat to relieve stress and help metal return to shape; many high-strength and boron steels must not be heated because they lose strength.

Correcting structural steel at room temperature using mechanical force only, which avoids the strength loss that excessive heat causes in modern high-strength steels.

Securing the vehicle to a frame bench or floor pots with clamps and chains so pulling force travels into the damaged structure rather than dragging the whole car.

A zinc-rich coating brushed on mating surfaces before welding; it allows current to flow for the weld and leaves corrosion protection between the joined panels.

A creeping rust inhibitor sprayed or fogged inside closed box sections after repair to coat interior surfaces that paint and undercoat cannot reach.

Replacing only the damaged portion of a structural part, cutting at a manufacturer-approved location and joining the new piece, instead of replacing the whole component.

The point where the manufacturer permits a structural part to be cut and rejoined; it avoids crush zones, reinforcements, and areas of high stress.

The original joint where the assembly plant joined two panels; replacement parts are often separated at these seams when a full panel is installed.

Cutting out the original resistance spot welds with a drill, hole saw, or grinder so a damaged panel can be lifted off without gouging the panel underneath.

A high-strength two-part epoxy that bonds panels and spreads load across the joint; it needs clean surfaces, the correct gap, and clamping until fully cured.

A joining method that combines structural adhesive with rivets, common on aluminum and mixed-material bodies where the manufacturer specifies it for strength and corrosion control.

A fastener that punches through the top panel and flares into the lower one without a pre-drilled hole; used where spot welding is unsuitable, such as aluminum structures.

A process that feeds a continuous wire electrode through a shielding gas to fuse metal; commonly called MIG welding and widely used for structural steel in collision repair.

Clamping two panels between copper electrodes and passing current to form a nugget, reproducing the factory weld; preferred over plug welds where the equipment can reach.

Joining steel with a silicon-bronze filler wire at a temperature lower than welding, which limits heat damage to coatings and to high-strength steels.

A weld made in a hole punched or drilled in the outer panel so the arc fuses it to the panel behind; used where a spot welder cannot reach.

The ring of base metal next to a weld that is heated but not melted; its strength changes, so manufacturers limit heat input and specify weld size and spacing.

How deeply the weld metal fuses into the base metal; too little leaves a weak joint, while too much can burn through thin or coated panels.