Additive Manufacturing (AM) allows increased complexity which poses challenges to quality-control (QC) and non-destructive evaluation (NDE) of manufactured parts. The lack of simple, reliable, and inexpensive methods for NDE of AM parts is a significant obstacle to wider adoption of AM parts.
Electromechanical impedance measurements have been investigated as a means to detect manufacturing defects in AM parts. Impedance-based NDE utilizes piezoelectric wafers as collocated sensors and actuators. Taking advantage of the coupled electromechanical characteristics of piezoelectric materials, the mechanical characteristics of the part under test can be inferred from the electrical impedance of the piezoelectric wafer. Previous efforts have used piezoelectric wafers bonded directly to the part under test, which imposes several challenges regarding the applicability and robustness of the technique. This paper investigates the use of an instrumented clamp as a solution for measuring the electromechanical impedance of the part under test. The effectiveness of this approach in detecting manufacturing defects is compared to directly bonded wafers.
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NDE of Additively Manufactured Parts via Directly Bonded and Mechanically Attached Electromechanical Impedance Sensors
Additive Manufacturing (AM) allows increased complexity which poses challenges to quality-control (QC) and non-destructive evaluation (NDE) of manufactured parts. The lack of simple, reliable, and inexpensive methods for NDE of AM parts is a significant obstacle to wider adoption of AM parts.
Electromechanical impedance measurements have been investigated as a means to detect manufacturing defects in AM parts. Impedance-based NDE utilizes piezoelectric wafers as collocated sensors and actuators. Taking advantage of the coupled electromechanical characteristics of piezoelectric materials, the mechanical characteristics of the part under test can be inferred from the electrical impedance of the piezoelectric wafer. Previous efforts have used piezoelectric wafers bonded directly to the part under test, which imposes several challenges regarding the applicability and robustness of the technique. This paper investigates the use of an instrumented clamp as a solution for measuring the electromechanical impedance of the part under test. The effectiveness of this approach in detecting manufacturing defects is compared to directly bonded wafers.
more »
« less
- Award ID(s):
- 1635356
- NSF-PAR ID:
- 10079220
- Date Published:
- Journal Name:
- IMAC XXXVI A Conference and Exposition on Structural Dynamics,
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The flexibility offered by additive manufacturing (AM) technologies to fabricate complex geometries poses several challenges to non-destructive evaluation (NDE) and quality control (QC) techniques. Existing NDE and QC techniques are not optimized for AM processes, materials, or parts. Such lack of reliable means to verify and qualify AM parts is a significant barrier to further industrial adoption of AM technologies. Electromechanical impedance measurements have been recently introduced as an alternative solution to detect anomalies in AM parts. With this approach, piezoelectric wafers bonded to the part under test are utilized as collocated sensors and actuators. Due to the coupled electromechanical characteristics of piezoelectric materials, the measured electrical impedance of the piezoelectric wafer depends on the mechanical impedance of the part under test, allowing build defects to be detected. This paper investigates the effectiveness of impedance-based NDE approach to detect internal porosity in AM parts. This type of build defects is uniquely challenging as voids are normally embedded within the structure and filled with unhardened model or supporting material. The impact of internal voids on the electromechanical impedance of AM parts is studied at several frequency ranges.more » « less
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Currently, verifying additively manufactured (AM) parts requires time consuming and expensive nondestructive evaluation (NDE) processes such as computed tomography (CT) x-ray scanning. While such methods provide details on flaw type and location, they require significant cost and time. Often, in production environments, significant value is gained by rapidly screening part specimens for flaws at all. Cost-effective per-specimen testing for production runs of AM parts is important for their use to be economically justified. In this work, Northrop Grumman Corporation and Virginia Tech explored impedance-based testing as a means to evaluate AM titanium specimens. Specimens with and without manually-designed flaws were fabricated through a metal- based AM process and evaluated using the impedance-based technique. CT scans confirmed that the intended flaws in the experimental specimens were present. Impedance-based examination also showed the presence of unintended defects. After machining away the unintended defective regions, the flaw-containing defective specimen had a clearly different impedance ‘signature’ than non-flawed baseline specimens. Additional analysis confirmed that the impedance test method required cheaper capital equipment and required less technician time to examine test results. Taken together, this means that the impedance-based this method can reduce the total cost of utilizing AM for metal part manufacturing.more » « less
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Abstract The geographical separation between various supply chain participants creates challenges in ensuring the integrity of the parts under circulation. These supply chains have to regularly deal with counterfeiting, a significant problem with an estimated value equivalent to at least the tenth-largest global economy. Industries are constantly upgrading their anti-counterfeiting methods to tackle this ever-increasing issue. Traditionally, a physical or cyber-physical part identifier is used to assert the integrity and identity of parts moving through the supply chain. For this work, we propose the use of electromechanical impedance measurements to generate a robust, unique part identifier linked to physical attributes. Electromechanical impedance measurements have been employed as a basis for non-destructive evaluation techniques in damage detection and health monitoring. We propose using these high-frequency measurements recorded through bonded piezoceramic transducers to help uniquely identify parts.
For this study, identical piezoceramic transducers (cut from the same wafer to minimize variations) were mounted on identically manufactured specimens. The only distinction between these specimens was the physical variation introduced during manufacturing and instrumentation. Multiple measurements for each specimen were recorded. A unique part identification methodology based on linear projection was created using these measurements. Lastly, a leave-one-out-study was performed to uniquely identify the left-out specimen. This was used to validate the part identification methodology. This paper introduces the use of electromechanical impedance measurements (widely adopted for damage detection) as a unique part identifier, with a basic experimental implementation of the proposed mechanism on identically manufactured parts. The paper also highlights some challenges and future work needed to make this methodology robust and adaptable.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
