Internal Porosity Detection in Additively Manufactured Parts via Electromechanical Impedance Measurements

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.

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Evaluation of the ISHM Method Applied for Composite Rotors

Volume 8: 31st Conference on Mechanical Vibration and Noise ◽

10.1115/detc2019-98119 ◽

2019 ◽

Author(s):

Karina M. Tsuruta ◽

Lucas A. A. Rocha ◽

Aldemir Ap. Cavalini ◽

Roberto M. Finzi Neto ◽

Valder Steffen

Keyword(s):

Lead Zirconate Titanate ◽

Electrical Impedance ◽

Optimization Procedure ◽

Mechanical Impedance ◽

Lead Zirconate ◽

Sensors And Actuators ◽

Present Contribution ◽

Structure Damage ◽

Electromechanical Impedance ◽

Rotor Shaft

Abstract The use of SHM (structural health monitoring) techniques has shown promising results for fault detection in rotating machines, making possible to identify various malfunctions. SHM methods provide maintainability and safe operation for these systems. The objective of the present work is to evaluate the SHM method based on the electromechanical impedance (ISHM) to detect faults in a composite rotor shaft. Composite materials present complex damage mechanisms due to their anisotropy and heterogeneity. Moreover, the process of damage detection in these materials is more challenging than in metallic structures. The ISHM approach uses piezoelectric (PZT – Lead Zirconate Titanate) patches as sensors and actuators coupled to the monitored structure. Variations in their electrical impedance are associated with changes in the mechanical integrity of the system. The electrical impedance of the PZT sensor is directly related to the mechanical impedance of the structure, which changes according to variations in the mass, stiffness, and damping properties of the structure. Damage metrics are used to quantify variations in the electrical impedance (impedance signatures) of the PZT patches. Despite the ISHM approach be able to detect incipient faults, it presents some disadvantages. For instance, the impedance signatures are susceptible to temperature variation. In the present contribution, to detect damages in the considered composite rotor shaft, the ISHM technique was implemented based on a data normalization methodology. Thus, an optimization procedure based on hybrid optimization was used to avoid false diagnostics.

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Electromechanical Impedance Modeling for Structural Health Monitoring

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

10.1115/smasis2012-8094 ◽

2012 ◽

Author(s):

Liuxian Zhao ◽

Lingyu Yu ◽

Mattieu Gresil ◽

Michael Sutton ◽

Siming Guo

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Electrical Impedance ◽

Piezoelectric Materials ◽

Fiber Composite ◽

Mechanical Impedance ◽

Experimental Result ◽

Electromechanical Impedance ◽

Structural Health ◽

Aluminum Beam

Electromechanical impedance (EMI) method is an effective and powerful technique in structural health monitoring (SHM) which couples the mechanical impedance of host structure with the electrical impedance measured at the piezoelectric wafer active sensor (PWAS) transducer terminals. Due to the electromechanical coupling in piezoelectric materials, changes in structural mechanical impedance are reflected in the electrical impedance measured at the PWAS. Therefore, the structural mechanical resonances are reflected in a virtually identical spectrum of peaks and valleys in the real part of the measured EMI. Multi-physics based finite element method (MP-FEM) has been widely used for the analysis of piezoelectric materials and structures. It uses finite elements taking both electrical and mechanical DOF’s into consideration, which allows good differentiation of complicated structural geometries and damaged areas. In this paper, MP-FEM was then used to simulate PWAS EMI for the goal of SHM. EMI of free PWAS was first simulated and compared with experimental result. Then the constrained PWAS was studied. EMI of both metallic and glass fiber composite materials were simulated. The first case is the constrained PWAS on aluminum beam with various dimensions. The second case studies the sensitivity range of the EMI approach for damage detection on aluminum beam using a set of specimens with cracks at different locations. In the third case, structural damping effects were also studied in this paper.. Our results have also shown that the imaginary part of the impedance and admittance can be used for sensor self-diagnosis.

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Analysis of the Impact of Sustained Load and Temperature on the Performance of the Electromechanical Impedance Technique through Multilevel Machine Learning and FBG Sensors

Sensors ◽

10.3390/s21175755 ◽

2021 ◽

Vol 21 (17) ◽

pp. 5755

Author(s):

Ricardo Perera ◽

Lluis Torres ◽

Francisco J. Díaz ◽

Cristina Barris ◽

Marta Baena

Keyword(s):

Machine Learning ◽

Mechanical Performance ◽

Mechanical Impedance ◽

Machine Learning Techniques ◽

Sustained Load ◽

False Alarms ◽

Engineering Structures ◽

Near Surface ◽

Electromechanical Impedance ◽

The Impact

The electro-mechanical impedance (EMI) technique has been applied successfully to detect minor damage in engineering structures including reinforced concrete (RC). However, in the presence of temperature variations, it can cause false alarms in structural health monitoring (SHM) applications. This paper has developed an innovative approach that integrates the EMI methodology with multilevel hierarchical machine learning techniques and the use of fiber Bragg grating (FBG) temperature and strain sensors to evaluate the mechanical performance of RC beams strengthened with near surface mounted (NSM)-fiber reinforced polymer (FRP) under sustained load and varied temperatures. This problem is a real challenge since the bond behavior at the concrete–FRP interface plays a key role in the performance of this type of structure, and additionally, its failure occurs in a brittle and sudden way. The method was validated in a specimen tested over a period of 1.5 years under different conditions of sustained load and temperature. The analysis of the experimental results in an especially complex problem with the proposed approach demonstrated its effectiveness as an SHM method in a combined EMI–FBG framework.

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Impedance-based non-destructive evaluation of additively manufactured parts

Rapid Prototyping Journal ◽

10.1108/rpj-03-2016-0046 ◽

2017 ◽

Vol 23 (3) ◽

pp. 589-601 ◽

Cited By ~ 12

Author(s):

Mohammad I. Albakri ◽

Logan D. Sturm ◽

Christopher B. Williams ◽

Pablo A. Tarazaga

Keyword(s):

Complex Geometry ◽

Cost Effective ◽

Learning Context ◽

Content Type ◽

Electromechanical Impedance ◽

Internal Porosity ◽

Non Destructive Evaluation ◽

The Impact ◽

Non Destructive ◽

Am Processes

Purpose This work proposes the utilization of electromechanical impedance measurements as a means of non-destructive evaluation (NDE) for additive manufacturing (AM). The effectiveness and sensitivity of the technique for a variety of defect types commonly encountered in AM are investigated. Design/methodology/approach To evaluate the feasibility of impedance-based NDE for AM, the authors first designed and fabricated a suite of test specimens with build errors typical of AM processes, including dimensional inaccuracies, positional inaccuracies and internal porosity. Two polymer AM processes were investigated in this work: material jetting and extrusion. An impedance-based analysis was then conducted on all parts and utilized, in a supervised learning context, for identifying defective parts. Findings The newly proposed impedance-based NDE technique has been proven to be an effective solution for detecting several types of print defects. Specifically, it was shown that the technique is capable of detecting print defects resulting in mass change (as small as 1 per cent) and in feature displacement (as small as 1 mm) in both extruded nylon parts and jetted VeroWhitePlus parts. Internal porosity defects were also found to be detectable; however, the impact of this defect type on the measured impedance was not as profound as that of dimensional and positional inaccuracies. Originality/value Compared to currently available NDE techniques, the newly proposed impedance-based NDE is a functional-based technique with the advantages of being cost-effective, sensitive and suitable for inspecting AM parts of complex geometry and deeply embedded flaws. This technique has the potential to bridge the existing gaps in current NDE practices, hence paving the road for a wider adoption of AM to produce mission-critical parts.

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Finite Element Simulation of Electro-Mechanical Impedance Technique

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1115.539 ◽

2015 ◽

Vol 1115 ◽

pp. 539-542

Author(s):

Kamyar Tahmasebpour ◽

Meftah Hrairi ◽

Mohd Sultan I.S. Dawood

Keyword(s):

Finite Element ◽

Piezoelectric Materials ◽

Piezoelectric Element ◽

Mechanical Impedance ◽

Signal Frequency ◽

Impedance Method ◽

Electromechanical Impedance ◽

Finite Element Software ◽

Sensor Position ◽

Impedance Technique

Electro-mechanical impedance method is emerging as an important and powerful technique for structural health monitoring (SHM). Active elements of the technique are Piezoelectric Wafer Active Sensor (PWAS) bonded on the structure. Modeling and simulation of PWAS and host structure play an important role in the SHM applications with PWAS. For decades finite element method has been extensively applied in the analysis of piezoelectric materials and structures. In this paper, piezoelectric element and a host metallic structure were modeled using Ansys finite element software to find the Electromechanical Impedance (EMI) according to the signal frequency. After that, the EMI signature of the beam was found for different position of the PWAS patch. The study shows that sensor position may directly control the EMI signature.

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Comparison of Mechanical Impedance Methods for Vibration Simulation

Shock and Vibration ◽

10.1155/1996/871696 ◽

1996 ◽

Vol 3 (3) ◽

pp. 223-232 ◽

Cited By ~ 4

Author(s):

Jeffrey A. Gatscher ◽

Grzegorz Kawiecki

Keyword(s):

Mechanical Impedance ◽

Field Measurements ◽

Cumulative Damage ◽

Vibration Test ◽

Element Analysis ◽

Impedance Measurements ◽

Testing Strategies ◽

Impedance Testing ◽

Vibration Simulation ◽

Test Requirements

The work presented here explored the detrimental consequences that resulted when mechanical impedance effects were not considered in relating vibration test requirements with field measurements. The ways in which these effects can be considered were evaluated, and comparison of three impedance methods was accomplished based on a cumulative damage criterion. A test structure was used to simulate an equipment and support foundation system. Detailed finite element analysis was performed to aid in computation of cumulative damage totals. The results indicate that mechanical impedance methods can be effectively used to reproduce the field vibration environment in a laboratory test. The establishment of validated computer models, coupled with laboratory impedance measurements, can eliminate the overtesting problems inherent with constant motion, infinite impedance testing strategies.

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Experimental Investigation on Improving Electromechanical Impedance Based Damage Detection by Temperature Compensation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.569-570.1132 ◽

2013 ◽

Vol 569-570 ◽

pp. 1132-1139 ◽

Cited By ~ 10

Author(s):

Thomas Siebel ◽

Mihail Lilov

Keyword(s):

Damage Detection ◽

Structural Damage ◽

Temperature Compensation ◽

Impact Damage ◽

Correlation Coefficients ◽

Electromechanical Impedance ◽

Reinforced Plastic ◽

Influence Of Temperature On ◽

Compensation Approach ◽

The Impact

The sensitivity of the electromechanical impedance to structural damage under varying temperature is investigated in this paper. An approach based on maximizing cross-correlation coefficients is used to compensate temperature effects. The experiments are carried out on an air plane conform carbon fiber reinforced plastic (CFRP) panel (500mm x 500mm x 5mm) instrumented with 26 piezoelectric transducers of two different sizes. In a first step, the panel is stepwise subjected to temperatures between-50 °C and 100 °C. The influence of varying temperatures on the measured impedances and the capability of the temperature compensation approach are analyzed. Next, the sensitivity to a 200 J impact damage is analyzed and it is set in relation to the influence of a temperature change. It becomes apparent the impact of the transducer size and location on the quality of the damage detection. The results further indicate a significant influence of temperature on the measured spectra. However, applying the temperature compensation algorithm can reduce the temperature effect at the same time increasing the transducer sensitivity within its measuring area. The paper concludes with a discussion about the trade-off between the sensing area, where damage should be detected, and the temperature range, in which damage within this area can reliably be detected.

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Enhanced fatigue resistance and lattice dynamics induced by the strong local strain in Fe-doped KTa1-xNbxO3 single crystal

Journal of Materials Chemistry C ◽

10.1039/d1tc04480j ◽

2021 ◽

Author(s):

Xiaolin Huang ◽

Peng Tan ◽

Yu Wang ◽

Yao Zhang ◽

Xiangda Meng ◽

...

Keyword(s):

Single Crystal ◽

Fatigue Resistance ◽

Lattice Dynamics ◽

Piezoelectric Materials ◽

Local Strain ◽

Lead Free ◽

Fatigue Properties ◽

Practical Applications ◽

Local Structures ◽

The Impact

Improvement of durability is greatly important for the practical applications of lead-free-doped piezoelectric materials. However, the promotional mechanism of anti-fatigue properties and the impact on local structures from ion dopants...

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Temperature Effects on Electromechanical Response of Deposited Piezoelectric Sensors Used in Structural Health Monitoring of Aerospace Structures

Sensors ◽

10.3390/s19122805 ◽

2019 ◽

Vol 19 (12) ◽

pp. 2805 ◽

Cited By ~ 1

Author(s):

Hamidreza Hoshyarmanesh ◽

Mojtaba Ghodsi ◽

Minjae Kim ◽

Hyung Hee Cho ◽

Hyung-Ho Park

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Mechanical Impedance ◽

Peak Shift ◽

Aluminum Plate ◽

Distinct Advantage ◽

Compressor Blades ◽

Turbine Engine ◽

Electromechanical Impedance ◽

Structural Health

Turbomachine components used in aerospace and power plant applications preferably require continuous structural health monitoring at various temperatures. The structural health of pristine and damaged superalloy compressor blades of a gas turbine engine was monitored using real electro-mechanical impedance of deposited thick film piezoelectric transducers at 20 and 200 °C. IVIUM impedance analyzer was implemented in laboratory conditions for damage detection in superalloy blades, while a custom-architected frequency-domain transceiver circuit was used for semi-field circumstances. Recorded electromechanical impedance signals at 20 and 200 °C acquired from two piezoelectric wafer active sensors bonded to an aluminum plate, near and far from the damage, were initially utilized for accuracy and reliability verification of the transceiver at temperatures >20 °C. Damage formation in both the aluminum plate and blades showed a peak shift in the swept frequency along with an increase in the amplitude and number of impedance peaks. The thermal energy at 200 °C, on the other hand, enforces a further subsequent peak shift in the impedance signal to pristine and damaged parts such that the anti-resonance frequency keeps reducing as the temperature increases. The results obtained from the impedance signals of both piezoelectric wafers and piezo-films, revealed that increasing the temperature somewhat decreased the real impedance amplitude and the number of anti-resonance peaks, which is due to an increase in permittivity and capacitance of piezo-sensors. A trend is also presented for artificial intelligence training purposes to distinguish the effect of the temperature versus damage formation in sample turbine compressor blades. Implementation of such a monitoring system provides a distinct advantage to enhance the safety and functionality of critical aerospace components working at high temperatures subjected to crack, wear, hot-corrosion and erosion.

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