Destructive Testing and Properties Flashcards
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Which of the following destructive tests is specifically designed to evaluate the notch toughness of a material, particularly its susceptibility to brittle fracture at various temperatures?
Answer: Charpy V-Notch Test
The Charpy V-Notch (CVN) test measures the amount of energy a standardized notched specimen absorbs during fracture from a pendulum strike. This absorbed energy is a direct measure of the material's notch toughness, which is critical for assessing its resistance to brittle fracture, often across a range of temperatures.
A Procedure Qualification Record (PQR) for a groove weld on a 1-inch thick plate specifies side bend tests instead of root and face bend tests. What is the primary reason for this requirement?
Answer: The material thickness is too great for a meaningful root or face bend test.
Welding codes such as AWS D1.1 and ASME Section IX require side bend tests for thicker materials (typically 3/8" or 10mm and greater). On thick sections, a root or face bend would place extreme strain on the outer fibers, making a valid test of weld soundness difficult. A side bend tests the entire weld cross-section for ductility and discontinuities.
A CWI performs a macroetch test on a cross-section of a fillet weld as part of a procedure qualification. Which of the following observations would be a primary focus of this examination?
Answer: The weld's profile, including depth of fusion and leg size.
A macroetch test involves polishing and etching a weld cross-section to reveal its metallurgical structure at a macroscopic level. It is used to evaluate the overall weld profile, depth of penetration, fusion to the root, leg sizes, and the presence of large discontinuities like porosity, lack of fusion, or cracks.
During a transverse tensile test of a welded specimen, which of the following properties is NOT directly determined from the test data?
Answer: Impact Strength
A transverse tensile test measures a material's response to a slow, static pulling force, which is used to determine its ultimate tensile strength, yield strength, ductility (elongation and reduction of area), and the fracture location (weld metal, HAZ, or base metal). Impact strength, which is a measure of toughness under a high strain rate, is determined by a dynamic test like the Charpy V-Notch test, not a tensile test.
A welder's performance qualification test requires a nick-break test on a groove weld. What is the primary objective of this specific destructive test?
Answer: To reveal the internal soundness and fusion of the weld metal.
The nick-break test involves cutting notches into the weld and then fracturing the specimen along the weld line. This exposes the internal fracture surface, allowing for a visual examination of the weld's internal quality. It is specifically used to check for discontinuities such as slag inclusions, porosity, and lack of fusion.
In the context of material properties, which statement best describes the typical relationship between hardness and toughness in the heat-affected zone (HAZ) of a carbon steel weld?
Answer: An increase in hardness, often due to rapid cooling, generally leads to a decrease in toughness.
For many carbon and low-alloy steels, there is an inverse relationship between hardness and toughness. Rapid cooling rates in the HAZ can create hard, brittle microstructures (like martensite), which increases the material's hardness but significantly reduces its ability to absorb energy before fracturing, thus lowering its toughness.