Destructive Testing Practice Questions

Explanation: In a root bend, the root of the weld is on the outside (convex) radius, subjecting it to the maximum tensile strain to check for root defects.

Explanation: AWS D1.1 Section 4.9.3.3 states that the convex surface shall not contain discontinuities exceeding 1/8 inch (3 mm) measured in any direction.

Explanation: This test uses a cylindrical specimen machined entirely from the weld metal to determine the properties (yield, UTS, elongation) of the filler metal itself, excluding base metal effects.

Explanation: Rockwell C (HRC) uses a diamond cone (brale) indenter and a 150 kg load, typically used for harder steels. Rockwell B uses a steel ball.

Explanation: The fillet weld break test involves breaking the sample to inspect the fracture surface for root fusion, penetration, and internal defects like slag or porosity.

Explanation: Macroetching (visual examination at low magnification) reveals the weld structure, including penetration, HAZ width, and individual weld passes.

Explanation: The nick-break test forces a fracture through the weld metal (by nicking the sides) to expose internal discontinuities like slag inclusions, gas pockets, or lack of fusion.

Explanation: Percent Elongation = ((Final Length - Original Length) / Original Length) x 100. It measures ductility.

Explanation: Impact toughness changes drastically with temperature (DBTT). The specimen must be tested at a specific, controlled temperature to get valid results.

Explanation: The Brinell test presses a 10mm ball into the surface. The hardness number (HB) is calculated based on the *diameter* of the indentation.

Explanation: Side bends expose the entire cross-section (root to face) of the weld and are commonly used for thicker plates (>3/8 inch) instead of separate root and face bends.

Explanation: The highest point on the stress-strain curve represents the maximum load the material sustained, which is the Ultimate Tensile Strength (UTS). It indicates the maximum stress the material can withstand before necking begins.

Explanation: If the break occurs in the base metal, it proves the weld metal and interface were stronger than the base metal.

Explanation: The Vickers test uses a square-based diamond pyramid indenter, suitable for microhardness testing of small areas (like specific HAZ zones).

Explanation: Peel testing involves mechanically peeling apart two sheets joined by a resistance spot weld to measure the button diameter and fracture mode.

Explanation: Reduction of Area = ((Original Area - Final Area at fracture) / Original Area) x 100. It is a measure of ductility.

Explanation: A hardness survey traverses the Base Metal, HAZ, and Weld Metal to detect hard spots (martensite) or soft spots.

Explanation: Longitudinal bends are taken parallel to the weld axis. They are often used when the base metals have significantly different yield strengths.

Explanation: The Drop Weight Test (ASTM E208) determines the Nil-Ductility Transition (NDT) temperature, below which the steel behaves in a brittle manner.

Explanation: Microetching involves high magnification (>50X) to see grain structure, phases, and microscopic inclusions. (Macro is <10X or naked eye).

Explanation: Nital (typically 5-10% nitric acid in methanol/ethanol) is the standard etchant for revealing carbon steel weld structures.

Explanation: Fillet welds are designed to carry shear loads. Transverse or longitudinal shear tests are used to determine their strength.

Explanation: For materials with a distinct yield point (like mild steel), the load stops increasing temporarily while strain continues (drop of the beam).

Explanation: Wraparound jigs ensure the specimen follows the radius without sliding friction or kinking, which is critical for softer metals like aluminum.

Explanation: Due to the rapid heating and cooling cycle (quenching effect) of welding, the HAZ often transforms into harder microstructures (like martensite/bainite) compared to the annealed base metal.

Explanation: Stress = Force / Area. 35,000 lbs / 0.5 sq in = 70,000 psi.