I-CAR Structural flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Direct vs. indirect damage

Direct damage occurs at the impact point where force was applied. Indirect damage appears elsewhere as energy travels through the structure, often at hinges, seams, and glass openings.

Sway damage definition

Sway is lateral displacement of the body at one end relative to the other, so the structure shifts sideways rather than shortening. It is detected by comparing side-to-side and diagonal measurements.

Diamond distortion

Diamond is a parallelogram distortion in plan view, where one side shifts forward and the opposite side shifts rearward. Cross-diagonal measurements differ, revealing the condition.

Mash damage

Mash is vertical collapse or shortening of the structure, typically from a direct frontal or rear impact. Height measurements at control points fall outside OEM specification.

Stress riser locations

Stress risers are geometric discontinuities such as hole edges, weld seam ends, sharp bends, and sectioning joints. Cracks and elongation concentrate at these points during a collision.

Unitized body construction

In a unitized body, panels, rails, and pillars are welded into a single load-bearing structure. There is no separate frame, so structural damage directly affects alignment and crash performance.

Body-over-frame construction

Body-over-frame vehicles use a separate frame that carries structural loads, with the body mounted on rubber or solid mounts. Frame damage and body damage are diagnosed separately.

Crush zone function

Crush zones are designed sections at the front and rear that deform in a controlled way to absorb collision energy. They must not be reinforced or repaired in ways that change that behavior.

Occupant safety cage

The safety cage includes pillars, rockers, roof, and floor reinforcements. It is designed to resist intrusion and protect occupants, so repairs there follow strict OEM structural procedures.

Heat-affected zone

The heat-affected zone is base metal whose microstructure and strength changed from welding heat without melting. It is often the weakest part of a repair joint.

Sectioning joint definition

A sectioning joint is an OEM-specified cut-and-join location used when replacing part of a panel. It avoids crush zones and original weld heat-affected zones.

Datum plane and centerline

The datum is a horizontal reference plane, and the centerline is the vertical symmetry plane through the vehicle. Control-point coordinates are given relative to these references.

Control point measurement

Control points are specific holes, bolts, or features with OEM X, Y, and Z coordinates. Measurements are taken at these points, not at arbitrary panel surfaces.

Three-point fixturing principle

A component must be located in three planes to be stable. Loose or missing fixturing allows the structure to move during pulling, producing inaccurate results.

Tram and diagonal measurement

Tram measurements compare diagonal distances between reference points. Unequal diagonals indicate diamond or sway distortion and guide the direction of the pull.

Pull direction rule

Pulling should oppose the direction of the original impact. Pulling at an angle to the damage path introduces new distortion rather than reversing the existing damage.

Incremental pulling

Incremental pulling applies force in small steps with re-measurement between pulls. It prevents overstretching metal and lets the technician stop when OEM dimensions are reached.

Anchoring during pulling

The vehicle must be anchored so the reaction force is carried by the bench or floor. Without secure anchoring, the body slides and the pull does not correct the damage.

Heat limits on AHSS

Many advanced high-strength and boron steels prohibit heating during straightening because heat reduces strength. Where heat is allowed, stay within OEM temperature limits and never quench.

STRSW nugget formation

Squeeze-type resistance spot welding passes current through stacked panels held by electrodes. Resistance heat at the faying surface forms the nugget, so clean mating surfaces are essential.

Shunting in spot welding

Shunting occurs when current bypasses the intended weld through an adjacent weld or conductive adhesive. It reduces current density and can produce an undersized nugget.

Destructive weld test

A destructive test uses a chisel or peel on a test coupon of the same stack-up. It verifies nugget diameter and failure mode before production welding begins.

Weld-through adhesive limits

Weld-through adhesive may be used only where the OEM permits it. Adhesive between panels changes electrical resistance and requires a validated weld schedule.

MIG versus MAG welding

MIG uses inert shielding gas, while MAG uses reactive gas mixtures. Both are gas-shielded arc processes using a consumable wire electrode, commonly called GMAW.

Plug weld requirements

Plug welds require an OEM-specified hole size and count in the outer panel. The weld must fuse both layers, and hole location follows the OEM procedure.

Heat input control

Heat input control uses the lowest practical amperage, shortest arc, and skip-weld sequences. This limits heat-affected zone softening in advanced high-strength steel.

Spot weld cutter use

A spot weld cutter removes the weld from the panel being replaced. The cutter must be sized to the weld and must not cut through the lower panel, which stays in place.

Trial fit before welding

Trial fitting checks gaps, flushness, and control-point alignment before any welding. Correcting fit after welding is much more difficult and may damage the new panel.

Weld count matching OEM

Replacement panels must receive the OEM-specified number and placement of welds. Fewer or relocated welds reduce structural integrity and crash performance.

Adhesive surface preparation

Structural adhesive bonding requires removing coatings where specified, abrading, and cleaning with the approved cleaner. Bonding must occur within the adhesive open time.

Rivet bonding concept

Rivet bonding combines structural adhesive with rivets. The adhesive carries shear load, while rivets clamp the joint during cure and add peel resistance.

Self-piercing rivet access

Self-piercing rivets require access to both sides of the joint for the rivet and die. Blind rivets are used where only one side is accessible.

Galvanic corrosion cause

Galvanic corrosion occurs when dissimilar metals contact in the presence of an electrolyte. Steel-to-aluminum joints need adhesive, sealant, or coated fasteners as isolation.

Cavity wax application

Cavity wax is applied inside rails, pillars, and rockers after welding to protect hidden surfaces. Access holes and drain paths must remain open after application.