ASTM E3370 : 24

1.1 This practice covers procedures for matrix array ultrasonic testing (MAUT) of monolithic composites, composite sandwich constructions, and metallic test articles. These procedures can be used throughout the life cycle of a part during product and process design optimization, on line process control, post-manufacturing inspection, and in-service inspection.

1.2 In general, ultrasonic testing is a common volumetric method for detection of embedded or subsurface discontinuities. This practice includes general requirements and procedures which may be used for detecting flaws and for making a relative or approximate evaluation of the size of discontinuities and part anomalies. The types of flaws or discontinuities detected include interply delaminations, foreign object debris (FOD), inclusions, disbond/un-bond, fiber debonding, fiber fracture, porosity, voids, impact damage, thickness variation, and corrosion.

1.3 Typical test articles include monolithic composite layups such as uniaxial, cross ply, and angle ply laminates, sandwich constructions, bonded structures, and filament windings, as well as forged, wrought, and cast metallic parts. Two techniques can be considered based on accessibility of the inspection surface: namely, pulse echo inspection for one-sided access and through-transmission for two-sided access. As used in this practice, both require the use of a pulsed straight-beam ultrasonic longitudinal wave followed by observing indications of either the reflected (pulse-echo) or received (through transmission) wave.

1.4 This practice provides two ultrasonic test procedures. Each has its own merits and requirements for inspection and shall be selected as agreed upon in a contractual document.

1.4.1 Procedure A, Pulse Echo (Non-contacting and Contacting) is at a minimum a single matrix array transducer transmitting and receiving longitudinal waves in the range of 0.5 MHz to 20 MHz (see Fig. 1). This procedure requires access to only one side of the test article. This procedure can be conducted by automated or manual means. Automated and manual test results may be analyzed in real time or recorded and analyzed later.

FIG. 1 Test Procedure A, Pulse Echo Apparatus Set-up for a Composite Panel (Left) and Metal Plate (Right) Using One-sided Access

1.4.2 Procedure B, Through Transmission (Non-contacting and Contacting) is a combination of two transducers. One transmits a longitudinal wave and the other receives the longitudinal wave in the range of 0.5 MHz to 20 MHz (see Fig. 2). This procedure requires access to both sides of the test article. Typically, the signal transmitting and signal receiving transducers are perpendicularly aligned with each other. This is normally achieved using a yoke transducer holder arrangement, which attaches the two transducers to a single point but deploys them on opposite sides of the structure. Through transmission inspections are also permitted without the use of a yoke transducer holder. This is due to the capacity for improved manual alignment via the matrix array transducers, whereby the live C-scan display enables visual confirmation of accurate alignment, and facilitates re-alignment if needed. This procedure can be conducted by automated or manual means. Automated and manual test results may be imaged or recorded.

FIG. 2 Test Procedure B, Through Transmission Apparatus Set-up using Two-sided Access

1.5 Other contact methods such as angle-beam techniques using shear waves to characterize welds, or surface-beam techniques using Lamb waves to detect impact damage in composite panel structures are not covered.

1.6 This practice does not specify accept-reject criteria.

1.7 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International StandardDetails, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.