Wire Inspection/Testing

Identify and eliminate defective wire before it is formed.

By Frank Passarelli, Resonic Technologies Ventura, CA, USA • www.resonic.com

There has long been a need in industries that use wire of various alloys in forming and forging operations. Most wire unless highly processed, an expensive and energy-intensive process, has defects both on the surface and internally that when formed into a near finished component either fracture due to the forming stresses or fracture during subsequent processing operations. Tooling wear and damage are directly affected by nonconforming materials.

There are several existing technologies including both eddy current and water coupled ultrasonics in use that are either ineff ective in finding a number of material defects or are too expensive or cumbersome to use in daily header machine operations. The technology has evolved from early work conducted at NIST (National Institute of Standards and Technology), into a commercially viable and proven industrial test methodology. The technique is now in use, where it’s providing a cost effective measurement solution with operating simplicity similar to process monitors.

Measurement capability extends from the surface to the deep interior. Additionally, microstructure variation information such as decarb, grain size irregularities and process variations is available.

Discontinuities such as cracks, seams and button defects, detailed by ASTM F2282 as well as localized modulus or elastic properties variations can be selectively detected.


Resonance describes a natural phenomenon throughout nature; all matter vibrates, like a violin string, a tuning fork or an atom. These vibrations characterize the object size, mass and composition.

Resonic Technologies has developed a technology to control the types of vibrations through its noncontacting technology allowing a practical method to extract information that details the materials properties of the object under test.

From a common technology, various applications have been developed from defect detection in wire that can be quickly identified and graded for their severity to individual components such as fasteners. Defects including inclusions and porosity are detected due to variances in thermal history and stress distributions surrounding the aff ected area. Some actual detection photographs are seen in Figure 1 and Figure 2.

Fig. 1 — Note the inclusion field and the distortion of the surrounding
microstructure 8740 alloy wire 0.494″ in diameter.

Fig. 2 — Detection is capable of complying or exceeding ASTM F2282 for surface seams and defects. Defect resolution in 0.250″ low carbon steel wire.

The science is known as EMAR (Electromagnetic Acoustic Resonance) or EMAS (Electromagnetic Acoustic Spectros-copy) in the scientifi c communities. This is not to be confused with the older Acoustic Resonance methods where a body is put into low-frequency vibration with a mechanical actua-tor and the resulting sound is mathematically analyzed for deviations from “normal”. In this application, noncontacting EMATs, Electromagnetic Acoustic Transducers, generate and detect specific shear wave ultrasonic resonances. The unique physics of these transducers enable spatial control of the acoustic fields confi ned in both depth and length along the wire axis. This is conceptually similar to an MRI of the material under inspection. The vibrating patterns change as diff erent material microstructures in the wire or rod pass under the transducers. And the nature of the EMAT allows for the measurement of pure high-frequency resonance modes only possible with a noncontacting method that is not available with the complica-tions of the piezo transducer and liquid couplant. Reference Figure 3 and Figure 4.

The System The ARIS (Acoustic Resonance Inspection System) instru-ment package from Resonic Technologies consists of a touch screen display, Windows™ based signal processing unit and self-adjusting transducer mount adaptable for a wide range of wire diameters. The installation of the ARIS (Acoustic Resonance Inspection System) instrument package is quick and nonintrusive and also requires little if any header machine downtime. Initial calibration and operator support can be provided remotely by Resonic. Communication with the header directly or process monitor is through an internal relay or other standard computer interface. Installation can be performed by the end user’s technical staff (Figure 5). Roller bearing suspension keeps the sensors suspended above the moving wire with the entire mount requiring about 2″ of clearance for mounting. In addition to its unique in-line wire detection technology, Resonic Technologies is developing a suite of applications using its advanced ultrasonic methodology including component level defect detection, precision hardness, hydrogen embrittlement detection and direct measurement of fastener preload. Resonic will be providing detailed information on these applications is the coming months.

Fig. 3 — Simulation of acoustic fields generated at different depths by EMAT transducers through the wire cross-section.

Fig. 4 — Typical transducer placement on wire with complete circumferential coverage, no rotation required.

Fig. 5 — Self-adjusting wire mount with EMAT’s
installed on 16 mm wire.

Company Profile: Resonic Technologies is the developer of a visionary and proprietary, nondestructive testing technology. Through both research and design activities Resonic produces high-performance, integrated inspection systems for manufacturers of specialty wire and automo-tive components in the USA. Resonic clients look to the company for novel inspection capabilities and com-petitive advantages at a time of rising material costs and increased design complexity. Higher performance manufacturing demands higher performance quality control. Since its founding in 2000, Resonic has been an active researcher in the field of applied Resonance Acoustic Spectroscopy or Resonance Scattering Theory. Originating from early scientific collaboration with NIST (National Institute of Standards and Technology), the patented Electromagnetic Acoustic Resonance Spectroscopy technique has been refined over time for a ground-breaking deployment into the service of industrial NDT. Resonic is an excitable and diverse group of engineers and technologists based in California. The company shares a contrarian spirit, a deep admiration for its manufacturing clients and a conviction that NDT will help to drive the future of industrial achievement. www.resonic.com

Source: August 2020/Fastener Technology International