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ASNT Level III- Visual & Optical Testing

My Level III Self Study Notes Reading 4 Section 4B

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PART 5: REPLICATION<br />

5.0 General<br />

Replication is a valuable tool for the analysis of fracture surfaces and<br />

microstructures and for documentation of corrosion damage and wear. There<br />

is also potential for uses of replication in other forms of surface testing.<br />

Replication is a method used for copying the topography of a surface that<br />

cannot be moved or one that would be damaged in transferal. A police officer<br />

making a plaster cast of a tire print at an accident scene or a scientist malting<br />

a cast of a fossilized footprint are common examples of replication. These<br />

replicas produce a negative topographic image of the subject known as a<br />

single stage replica. A positive replica made from the first cast to produce a<br />

duplicate of the original surface is called a second stage replica. Many<br />

replicating mediums are commercially available. The types commonly used in<br />

nondestructive testing typically fall into one of two categories: cellulose<br />

acetate replicas and silicone rubber replicas. Both have advantages and<br />

limitations but both can also provide valuable information without altering the<br />

test object.<br />

Charlie Chong/ Fion Zhang

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