Metal Additive Manufacturing (AM) technologies have been developing rapidly such that the procedures used to verify the quality and integrity of these products lag behind. Wire + Arc Additive Manufacturing (WAAM) is a leading AM technology that has evolved significantly over the past decade. The process is majorly used to manufacture low-volume high-mix critical components for applications in aerospace and nuclear industries. Therefore, the imposed Non-Destructive Evaluation (NDE) requirements demand very high detection sensitivities. The WAAM components are normally inspected in the post-manufacturing stage for the potential bulk discontinuities. However, after detecting and locating the defects, the components are then sent back to the manufacturing stage, and several layers removed to reach the defective layer and to perform necessary repairs. The automated NDE inspection of WAAM after deposition of every few layers could be the key solution to this problem by offering the advantage of early defect detection and reduction of material scrappage in the repair process.

Contact ultrasound testing (UT) using the array technology is among the few methods that can be effectively integrated as the NDE means in an automated WAAM inspection system, considering that the method provides bulk information and delivers submillimeter detection sensitivity. The testing method also overcomes the limitations associated with the penetration depth of eddy currents, particularly in ferromagnetic materials, and surpasses the radiography testing in terms of safety hazards and the low sensitivity to defects with tight openings. However, there are multiple challenges linked to the automated deployment of contact UT inspections in-process: (i) The layer-by-layer inspection or inspection after every few layers approach should be carried out on newly deposited surfaces when they have high temperatures (HT). This requires the UT probe to withstand HT of \~300˚C, (ii) The WAAM surface finish is curved and wavy which makes it difficult to carry out contact UT inspections. A mechanism should be devised to accommodate for the mismatch between the surface of the UT probe and the WAAM layer, (iii) The use of any type of liquid coupling between the WAAM layers, especially on a hot and newly deposited layer, can introduce defects inside the product and adversely affect the properties of the component and (iv) The design of the probe geometry should enable an easy mechanical scan on the surface of the components using the robot manipulators.

To overcome these challenges, this research presents on the novel design for a high-temperature ultrasonic-roller probe that can be employed on unmachined surfaces of WAAM components to detect near-surface defects. This is in line with the inspection after every a few layers approach for in-process inspection of WAAM. An initial concept for the roller-probe is devised, and material selection for different components of the roller probe is carried out considering the required mechanical, thermal and acoustic properties. The dimensions of the roller probe and its parts are determined according to the required imaging performance. The numerical finite element method is used to investigate the roller probe’s tire thickness for a fixed duty cycle of inspection at a temperature of 350˚C. The roller probe performance for inspection of a defective Ti-6Al-4V WAAM sample is assessed. The dry-coupled roller-probe proved successful of being capable of detecting a 1.5 mm flat bottom hole located at a depth of 5 mm under the unmachined WAAM surface.


A High-Temperature Phased Array Ultrasonic Roller-Probe Designed for Dry-Coupled In-Process Inspection of Wire + Arc Additive Manufactured Components

No proceedings papers in 2020. Video only.

QNDE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.