State whether the following is true or false.
The origin of a fracture in a ceramic can usually be located on the broken surface.
Answer: C
Mirror, mist and hackle regions radiate outward from the origin in a recognisable pattern. Reading them is a well-established technique and is often the fastest route to the cause of a failure. The technique needs the broken pieces to be preserved carefully.
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Assertion (A): Fractography is a routine part of ceramic failure investigation.
Reason (R): The fracture surface records where the failure began and what flaw started it.
Answer: D
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the value of the technique. The fracture surface carries markings - the mirror, mist and hackle regions - that radiate from the origin, so the origin can be located and the flaw at it identified: a pore, an inclusion, an agglomerate, a machining scratch. Naming the flaw names the process step that produced it, which is what turns a failure into a correction.
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A pore found at a fracture origin most likely originated during
Answer: A
Correct answer: forming or sintering rather than in service
A pore is a void that was never filled, so it dates from when the body was consolidated - poor packing at forming, an agglomerate that left a hole, or incomplete sintering. Service loads open cracks rather than creating voids, machining leaves surface damage rather than internal pores, and analysis of the powder touches nothing that ends up in the part.
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Assertion (A): An internal flaw and a surface flaw at a fracture origin implicate different parts of the process.
Reason (R): An internal flaw must have been present before firing, whereas a surface flaw may be introduced later.
Answer: B
Both are true and the reason gives the logic of the investigation: the position of the origin narrows the search considerably, which is why fractography is done before anything else is changed. Guessing at the cause without it wastes a great deal of effort.
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Machining damage to a fired ceramic is significant because it
Answer: C
Grinding leaves cracks below the machined surface, and these become the strength-limiting flaws. Lapping, polishing or a light anneal are used to reduce their severity where strength matters. Machining allowance is planned with the damage layer in mind.
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State whether the following is true or false.
A ground ceramic surface is generally stronger than an as-fired one.
Answer: D
Grinding introduces subsurface cracks that usually leave the machined surface weaker. Where strength matters the machined surface is finished further or the component is designed to keep the ground face in compression.
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Dye penetrant inspection reveals
Answer: A
A coloured liquid is drawn into any surface-connected crack and drawn back out onto a developer. It says nothing about internal flaws, for which radiography or ultrasonics is needed. Each method has its own detection limit and its own blind spots.
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Ultrasonic inspection of a ceramic detects flaws by
Answer: B
A discontinuity reflects part of the beam, and the time of the echo gives its depth. Coupling the transducer to a hard, irregular ceramic surface is the practical difficulty of the method. Immersion testing is used where the geometry allows it.
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Consider the following statements about non-destructive testing of ceramics.
1. Dye penetrant finds surface-breaking flaws.
2. Ultrasonics and radiography can find internal flaws.
3. Any of these methods can measure the Weibull modulus directly.
Answer: C
The first two are correct. The third is wrong, since the modulus is a statistical property derived from testing many specimens to destruction rather than something any single inspection can measure. Statistics and inspection answer quite different questions.
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State whether the following is true or false.
Non-destructive testing can guarantee that a ceramic component contains no flaws.
Answer: D
Every method has a detection limit, and flaws below that size are missed while still being large enough to cause failure. Inspection reduces risk rather than eliminating it. Design must still assume that some flaws escape detection.
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