The use of ultrasonic testing for flaw detection has a history of about seven decades. Beyond this application ultrasonic testing offers many other opportunities in the field of material characterization in which the main interest is the passage of ultrasound through a material with respect to what it reveals of material elastic properties. Two major and measurable attributes of a sound beam passing through a material are Velocity and Attenuation both of which are directly related to material structure. The following paper describes the use of ultrasonic testing to detect and measure Residual Stress in rolled Aluminum plates that are used for machining monolithic components of aircrafts. An example is given in fig. 1. The lower bulkhead of the C17 airplane is machined in one piece out of rolled aluminum plates of up to 8” thick. Excessive residual stress in the plate can cause deflection and deformation in the material during machining operation which renders the operation useless. Aerospace industry currently specifies a destructive test method in which a number of samples are cut from various parts of a plate and tested by machining it in 0.5” steps and measuring the resulting deflection which will then be sued to calculate the amount of residual stress. The following paper describes the work of the authors in developing an ultrasonic test method which can project the degree of deflection and amount of residual stress in a nondestructive fashion.

DOI: 10.32548/RS.2019.006

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