Title / Author(s) / Keywords 
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Session |
ECNDT 2018, Microwave, Terahertz, and Infrared NDE Comparison of inductive shearography and thermography for the detection of flaws in structural and elastic adhesive bonds
I. Kryukov  15, M. Kahlmeyer2, S. Böhm13
Department for Cutting and Joining Manufacturing Processes (tff); University of Kassel84, Kassel [Germany]
Adhesives and Bonding, Quality control, Shearography, Thermography
 Close
This article compares the potential of inductively excited shearography and active thermography for non-destructive testing of adhesively bonded joints. For this purpose, the detectability of different defects of elastic and structural adhesive joints between aluminium and deep-drawing steel was investigated.
Both methods show good results for non-destructive testing of structural adhesive bonds. The use of shearography allows the detection of defects that lead to local stiffness inhomogeneities, which can be caused by inhomogeneous stirring of adhesive components or by kissing bonds. The measurement of these defects with thermography is more challenging or almost impossible. However, active thermography is suitable to display defects that lead to measurable temperature gradients on the substrate surfaces which may be caused by an irregular thickness of adhesive. This defect couldn’t be detected via shearography yet. For elastic adhesive bonds, thermography showed better results as shearography. However, defects which effect the curing of adhesives could only be detected with shearography.
Since both methods exploit different physical principles and are thus suitable for the detection of different defects types, a combination of both non-destructive testing methods may prove beneficial. The two very well complementing methods enable examination and display of almost all relevant defects.
 
| Microwave, Terahertz, and Infrared NDE |
Contact NDT at Heights Using Aerial Robotics
R. Dahlstrom, J. Branch
Apellix Aerial Robotics, Jacksonville, FL [USA]
NDT-wide, Ultrasonic Testing (UT), Other Methods, Robot, safety, drones, aerial robotics, surface profile
Close
To take Nondestructive Testing (NDT) measurements at height, currently one may need to utilize a lift, scaffolding, ladders or other solutions to reach areas on ships. bridges, aboveground storage tanks, flare stacks and other Infrastructure and Industrial sites. This is both dangerous, due to the possibility of falls, and time consuming. In certain instances, it may also require taking an asset, such as a flare stack, offline to allow it to cool so it can be accessed to take NDT readings. Use of handheld digital testing devices are very common in these scenarios.
Utilizing an aerial robotics platform for contact-based NDT measurements such as Dry Film Thickness (DFT), Surface Profile (SP), or Ultrasonic Thickness (UT) allows workers to remain safely on the ground to take measurements. Further, since there is no need to move a lift, scaffolding or ladders or for the person taking the NDT readings to move from their current position, the NDT measurement process can be faster in addition to being safer.
The use of an aerial robotics platform is a new and novel application utilizing existing technologies such as DFT, SP, UT, etc. readers, drones, etc. with a system of complex integrations that allows for a better application of science. The system has the potential to improve the inspection, testing and data collection aspects of coated assets, in part, by making the NDT measurement process easier and safer thus allowing for more frequent measurements and/or a larger quantity of measurement samples.
With an easier, faster, and safer method to collect NDT measurements from locations of height we can expand the science of nondestructive testing by collecting data from locations where data was either inaccessible or difficult to obtain (access issues, safety considerations, etc.). The patented aerial robotic system discussed in this paper flies up to a structure with a metal sub-straight, then under full autonomous software control, touches a NDT measurement probe (such as a DFT, SP, UT, etc.) to the target and records the measurement data compliant with SSPC, ISO, ASTM, API or other standards. The goal of this paper is to make participants aware of this new technology as well as provide information as to its efficacy, limitations and operational requirements.
| Poster |
Applications of multimode regime of total focusing method (TFM) for definition the type of reflector
E. Bazulin2, A. Vopilkin5, D. Tikhonov5
Scientific and Production Center, SPC ECHO+11, Moscow [Russia]
Close
Definition of the defect type and sizes is the most important problem of the ultrasonic testing
industrial equipment in operation. Information about the defect type, sizes and coordinates will
allow to make valid conclusion about danger level of such reflector for object operation. One of
the solutions of this task is imaging of all border of the reflector. It is possible to use two phased
arrays located from the different sides of the control area. For the phased array located to the left
side of the reflector (N-channel) it is possible to receive a set of partial images of the reflector
accounting wave type transformation at the repeated reflections of the ultrasonic impulse (the
multimode regime). The same set of images could be received from the echo signals measured by
the phased array located to the right side of the reflector (P-channel) and from the signals
transmitted and received by different phased arrays (NP-channel). Integration of partial images
receiving from all channels by the large quantity of acoustic schemes allows to receive the image
of all defect border and to make a valid conclusion about its type. This approach allows to get
information about defect type when access is only one side with smaller efficiency. To improve
the image quality, the measured echo signals can be subjected to the procedure of extrapolation
its spectrums for reduction the impulses length.
| Poster |
Magnetic Particle Inspection (MPI)
J. Pereira
Catholic University of Petrópolis (UCP), Petrópolis [Brazil]
Close
Proposal of a method for identifying the high-level risks in the Magnetic Particle Inspection
(MPI) of ferromagnetic material parts, based on Analytic Hierarchy Process (AHP) and Bayesian
Belief Network (BBN). The combination of probability and the impact identified the most
significant risks, which needed to be addressed to improve quality management system and
ensure organization sustainability. The inspection of critical ferromagnetic parts with Magnetic
Particle in the manufacturing and services industry is very critical. The correct selection and use
of an adequate analysis method to ensure inspection process reliability is very important and can
avoid part failure and costly accidents. As a methodological approach, the estimated risk
probabilities for the risk factors are loaded into Bayesian Belief Networks software to assess the
probability of occurrence of undesirable events and AHP is utilized to rank the relative
importance (effect) of risks. The combination of probabilities and the effects identified the most
significant risks. No evidence of previous work could be found about the use of AHP and BBN
on the risk assessment of MPI of critical hardware. As far as the authors are aware, this is the
first time this method is being used in this specific process. The novelty of the paper is the
combination of Bayesian Belief Networks with AHP to select the most significant risk in the
inspection of critical parts. The application of the method revealed that the most significant risks
in the inspection of critical hardware are related to operator failure, unfavourable control and
environment, negative organizational factors. The paper proposes responses to these risks aiming
at preventing the occurrence of failure in the MPI inspection of critical hardware. This paper
contributes to the literature in the field non-destructive inspection of critical parts. The proposed
model has also practical implications and is an invaluable source for non-destructive inspection
professionals, safety engineers, quality managers and decision makers in companies to augment
their information and to identify critical risks in the non-destructive inspection of critical
ferromagnetic parts. The identification and prioritization of risk factor makes it easier to allocate
resources to prevent critical parts failure and improve product quality and ensure organization
sustainability.
| Poster |
Crack detection on aerospace composites by means of photorefractive interferometry.
T. Seresini1, S. Sunetchiieva15, H. Pfeiffer128, M. Wevers153, J. Xiong22, C. Glorieux15
1aDepartment of Physics and Astronomy, Laboratory for Soft matter and Biophysics bDepartment of Materials Engineering (MTM) cDepartment of Materials Engineering(MTM); Catholic University of Leuven (KU Leuven) 100, Leuven [Belgium]
2Research Institute of Nano-Resolution Optics (RINRO); Nanjing University of Science and Technology3, Nanjing [China]
Aerospace, Novel Techniques, Surface waves, Technology Transfer in NDT, Ultrasonics
Close
Aircraft industry requires fast, robust and reliable tools for assessing structural integrity. Linear ultrasonic techniques exploit the reflections resulting from the acoustical impedance mismatch caused by an open crack or delamination. However, when the fracture is closed then no reflection occurs. Most techniques rely on contact transducers both for excitation and detection, which is an important limitation when it comes to probing areas that are difficult to reach by the operator. Thus, the need for a technique that has higher sensitivity and ease of use than the available ones.
Surface waves travelling across a crack experience a nonlinear modulation of their frequency content if such crack is subject to periodical opening and closing (clapping). In this work, the phenomenon of clapping is used to assess the presence of defects, such as cracks or delamination, using a fully optical method. A low frequency, high amplitude surface wave is used to act on the defect, opening and closing the two limbs, while a high frequency, low amplitude surface wave is used as a probe, whose transmitted amplitude is modulated at the rhythm of opening and closing. The modulation results in frequency mixing. Although full field optical interferometry allows to visualise the dynamics of frequency mixing, most interferometric schemes have a nonlinear response between the light intensity and the displacements of interest, making it cumbersome to distinguish nonlinear acoustic effects from effects of nonlinear optical response.
In this work an approach is presented that exploits frequency selectivity of a photorefractive interferometer scheme to detect vibrations that are excited due to acoustic nonlinear effects that occur in the neighbourhood of defects, without interference of effects of optical nonlinearity. The method is non-contact and allows to inspect both in a pointwise scanning fashion, and in full-field mode, imaging vibrations of a complete large area at once, thus detecting defects in an early stage.
| Academia |
Non-destructive evaluation of dissimilar material joints
D. Smagulova, E. Jasiuniene27
aLaboratory of Acoustics and Thermal Physics bUltrasound Institute; Ultrasound Institute at Kaunas University of Technology189, Kaunas [Lithuania]
Adhesives and Bonding, Composite materials, Phased arrays, Ultrasonics
Close
The aim of this research was to find the most suitable and effective ultrasonic non-destructive technique that would enable to find defects in dissimilar material joints made of steel and GFRP.
By analyzing ultrasonic wave propagation characteristics through dissimilar joints several ultrasonic methods and transducer types were investigated using modeling and experimentally. Firstly the sample of steel and GFRP was designed in CIVA software where different solutions were used to compare the results of investigations of dissimilar material joint. It was determined that steel is 3 time less attenuating material than GFRP according to results of ultrasonic fields investigation and attenuation influence in steel and composite. Different types of transducers were applied for delamination detection between steel and GFRP. Phased array transducers were selected as the most suitable due to ability of steering of multiple elements, focusing and covering large area of the sample avoiding mechanical scanning. As a result of CIVA modeling it was determined that the amplitude difference of reflection from sample interface and sample delamination is very small what proves the complexity to detect the defects in experimental part. Comparing amplitude values of reflections from delaminations using different frequencies of phased array transducers and taking into account attenuation it was determined that the most suitable frequency to detect the defects in such sample is 3,5 MHz and 5 MHz phased array transducers.
In experimental part the Omniscan measurement system as well as phased array transducers were used for the inspection. All the artificial delaminations as well as their dimensions and depths were determined. As a result of this research, the best configuration for the delamination detection in dissimilar steel and GFRP sample was found.
| Academia |
New technologies for air-coupled ultrasonic transducers
M. Gaal41, D. Kotschate14
Akustische und Elektromagnetische Verfahren,Ultraschallsonderprüftechniken; BAM Federal Institute for Materials Research and Testing1265, Berlin [Germany]
Air-coupled ultrasound, Transducers, Ultrasonics
Close
Air-coupled ultrasonic testing (ACUT) has experienced rapid growth within the last years. It is especially well suited to inspection of lightweight structures consisting of composite materials and adhesive joints. Uniform coupling and easy maintenance are its advantages compared to contact technique. However, the impedance mismatch between the transducer and air poses a major challenge to the development of ACUT transducers. Commercially available air-coupled transducers consist of a piezocomposite material and matching layers. Their fabrication is difficult in handling and their signal-to-noise ratio sometimes not sufficient for various testing requirements. However, there are several innovative approaches using other materials and other physical principles to transmit and receive an ultrasonic pulse.
We present a review of the latest advances in research on air-coupled transducers for non-destructive testing, including previously unpublished results. We recognize two major directions as most promising: ferroelectrets and thermoacoustic transducers. Ferroelectrets are charged cellular polymers exhibiting piezoelectric properties. Their small acoustic impedance is matched to air better than matching layers applied in conventional air-coupled transducers. Applying bias voltage to a ferroelectret receiver is the latest development in this field, which increased the received signal by 12 to 15 dB. Thermoacoustic transducers use heat to initiate an ultrasonic wave, acting as transmitters. The working principle is known from nature as thunder and lightning: thermal energy of an electrically heated material, which can also be air, is converted into acoustic energy. Some thermoacoustic transmitters consist of a conductive layer with a thickness in the nanometer range deposited on a solid substrate. Another possibility is to use an electric spark. For the first time, measurements of the sound field of an electric spark up to 500 kHz were performed. Thermoacoustic transducers enable excitation of extremely broadband pulses while producing high pressure levels, which opens new possibilities for advanced signal processing.
| Academia |
NDT 4.0 - Overall Significance and Implications to NDT
R. Link19, N. Riess213
1Consultancy Dr. Rainer Link9, Kerpen [Germany]
2Helling GMBH13, Heidgraben [Germany]
Technology Transfer in NDT, Image processing
Close
Industry 4.0 is, with ongoing digitization and internet abilities, assumed to become the
fourth industrial revolution after the first which is based on mechanical manufacturing
driven by water and steam power, the second which comprises mass production with
electrical energy and the third revolution is determined by digital systems and robotics.
The aim of the project Industry 4.0 is to support plant manufacturing of the future in
Germany to make the production faster, more efficient and highly flexible.
It comprehends complete networks within industrial processes, from raw materials to
the finished product, including design with consideration to Non-Destructive Testing
(NDT, or NDE, Non-Destructive Evaluation), inspection, production, central quality
control and Structural Health Monitoring (SHM).
Today Industry 4.0 still is the relevant idea to be defined and promoted by state
institutions. However with available network possibilities it will in addition be a selffulfilling
future aspect in industrial processes. It is believed, that nearly all areas
involved in the industrial process are affected.
The question arises as to which extent it will influence the area and profession of NDT
as a technique and its related human resources. What would be the requirements and
challenges for NDT4.0?
Some aspects of the integration of the inspection results and quality control and online
information to the production department are not really new for NDT.
The overall networking of NDT 4.0, including all aspects within the industrial process
however requires more comprehensive information on the automation of NDT test
procedures to be applied and at the same time provide information to all interested
parties.
Intelligent sensors are guiding the component through the production process. Relevant
information has to be provided online to the quality and back to the production
department and as well to the customer. This obviously will require additional demands
to the performance of NDT systems. Structural Health Monitoring (SHM) of the
finished components or integrated into the complete system during operation is offering
additional perspectives and surveillance.
In this paper a completely automated system for magnetic particle inspection of steering
knuckles, tubes and round bars is described as an example.
| Academia European Reserch Day |
Nonlinear Signal Processing for NDT 4.0
S. Dos Santos125, Z. Převorovský263, C. Mattei32, V. Vengrinovich423, G. Nardoni534, J. Wrights6
1INSA Centre Val de Loire, Blois campus, University of Tours27, Blois [France]
2Institute of Thermomechanics, NDT Laboratory; Academy of Sciences of the Czech Republic (ASCR/CAS)108, Prague [Czech Republic]
3Creo Dynamics AB2, Linköping [Sweden]
4Institute of Applied Physics (IAPH); National Academy of Sciences (NAS) of Belarus100, Minsk [Belarus]
5I&T Nardoni Institute35, Brescia [Italy]
6Theta Technologies, Exeter [United Kingdom]
NDT-wide, Ultrasonic Testing (UT), signal processing, image processing, research, TR-NEWS, Ultrasonics, Standards, Novel Techniques, Technology Transfer in NDT, NDT 4.0
Close
The most efficient way of building up energy in an oscillating system is to do it in phase with a
resonant frequency of the system. If the resonant frequency changes for any reason this is difficult
to obtain with a static frequency generator. It is of course possible to sweep over a frequency
interval to find the maximum repeatedly, but a frequency sweep takes time and it is performed at
discrete frequencies. A better approach is to set the device under test in feedback resonance. This
will guarantee that the frequency is always a peak in the spectrum and the adaptation to change
is immediate and continuous in every aspect. A continuous observation of feedback frequency can
conceivably serve as an SHM indicator. Experiments with geophones as actuators are performed.
A 9-day test revealed smooth frequency variations in the 236.901 to 237.353 Hz interval. These
smooth variations are believed to be caused by thermal and humidity changes in the laboratory.
An audible tension release in the test device during this period was clearly indicated by a
momentary step in the resonant frequency.
A second experiment revealed that as the feedback gain was adjusted in steps, the feedback
frequency followed suit. This establishes indirectly the relation between deformation and resonant
frequency. It is thus possible to determine non-linearity with the controlled feedback resonance
method.
| Academia European Reserch Day |
NDT Integrity Engineering
P. Trampus16, V. Krstelj11
Academia NDT International, Brescia [Italy]
Education, Fracture mechanics, Strength
Close
In recent decades, enormous efforts have been made to increase the capacity of highvalue
and high-risk assets leading to their more intensive utilization. Besides this
commercial goal, the health, safety and environmental management system is equally
important. NDT Integrity Engineering supported by academic and educational systems
will evidently serve these purposes. NDT Integrity Engineering primarily focussing on
non-destructive methods encompasses all disciplines to establish any integrity related
decision. Core knowledge includes the physical bases, the possibilities and limitations
of major NDT methods; the evaluation principles of NDT results; the current tendency
to provide early detection of material degradation; the structural health monitoring
strategies and techniques; the impact of the development of information technology and
microelectronics on NDT and technical diagnostics. Its knowledge should also cover the
awareness of the physical field arising in the component during operation, including the
basics of analytical and numerical calculation methods. As a result, operation and
accident loading, stress / strain status, stress intensity factor, and other operational
conditions can be calculated. The properties of structural materials belong to here as
well: „material’s response” to loading and the environment, i.e. the potential ageing
processes such as embrittlement, loss of toughness, fatigue, corrosion, creep, wear and
some more, as well as their effect on component integrity. Expected knowledge
outcomes include all technical, scientific and social aspects involved in NDT quality
chain and maintaining the integrity of materials and products.
| Academia European Reserch Day |
Current Developments in Digital Radiography and Computed Tomography from nm to macro scale
U. Ewert212
8.3 Radiation Methods; BAM Federal Institute for Materials Research and Testing1265, Berlin [Germany]
Defects, Radiography, Tomography
Close
Digital Detector Arrays enable an extraordinary increase of contrast sensitivity in comparison to film radiography. The increased sensitivity of digital detectors enables the efficient usage for dimensional measurements and functionality tests substituting manual maintenance. The digital measurement of wall thickness and corrosion status is state of the art in petrochemical industry. X-ray back scatter techniques have been applied in safety and security relevant applications with single sided access of source and detector. First inspections of CFRP in aerospace industry were successfully conducted. Computed tomography (CT) applications cover the range from nm to m scale. Small structures of integrated circuits are visualized and measured with lens based CT-systems or at synchrotrons. Phase contrast imaging provides enhanced structure contrast in micro radiography and micro CT. The scope of typical CT applications changes from flaw detection to dimensional measurement in industry substituting coordinate measurement machines. Mobile computed tomography is applied for in-service radiographic crack detection and sizing of welded pipes in nuclear power plants and for NDT of large CFRP structures in aerospace applications. New specialized high energy CT devices have been laid out for inspection of complete cars before and after crash tests. High speed applications with flash tubes permit the 3D measurement of fast process dynamics including car crash visualization. Digital radiography techniques, computed tomography and computed laminography designs are nowadays developed by numerical simulation before hardware construction. New X-ray source concepts based on laser wake field acceleration permit further reduction of spot sizes and minifocus high energy applications.
| Academia European Reserch Day |
A music-inspired approach to structural health monitoring
J. Pimentel4, R. Klemm4, A. Irretier4, M. Dalgic4, H. Zoch4, K. Krieger4
aInstitute of Electrodynamics and Microelectronics (ITEM) bInstitute for Materials Testing, MPA; University of Bremen14, Bremen [Germany]
Acoustic Emission (AE), condition monitoring, data processing, Metals, Sensors, Acoustic emission, Percussive separation
Close
Acoustic emissions (AE) in a solid body can be used to monitor its structural health. Lightweight structures subjected to high and varying load, such as lightweight truck frames, are particularly susceptible to fatigue failures. Previous work from the authors showed success in the detection of macro- and microfractures in steel samples of truck trailer structures during both static tensile tests and dynamic fatigue tests. The physical processes that lead to the formation and propagation of cracks typically involve a sudden energy release, generating signals that are typically short-lived and span a relatively wide frequency range compared to the background noise. In these aspects, AE signals exhibit similarities to percussive instruments, although in rather different scales.
This work describes a new music-inspired approach to analyse vibroacoustic data from tensile and fatigue tests of steel structures. Its application involves analysing the sampled signals both over time and in the frequency domain to detect percussive onsets. A time registry of the AE events and their intensities is generated.
The method described was applied in the post-processing of measurement data to identify the emergence of cracks. Its success was verified by quantitative comparison with previously used detection methods and further examination of the tested samples (e.g. metallographic analysis), as described in the paper. The processing steps, relevant parameters and their influence on the results are discussed.
| Acoustic Emission |
Acoustic Emission Monitoring of in Service Harbor Cranes in Order to Program Maintenance Operations and Insure Safety Management
A. Proust111, R. Kefferstein2, O. Al Haj12, D. Crucq2
1Mistras Group, SAS19, Sucy-en-Brie [France]
2ArcelorMittal Fos-sur-Mer, Fos-sur-Mer Cedex [France]
Acoustic emission, Data processing, Fatigue, Inspection Qualification, Monitoring, Stress
Close
The plant of ArcelorMittal Fos-sur-Mer (France) is producing 4 million tons per year of hot rolled steel coils.
A significant part of the production is shipped by boats.
Two Titan harbor cranes are used in order to transfer the 40 tons coils on boats.
These cranes have been manufactured in the 70’s and some fatigue cracks have been discovered in 2015. Significant repairs were realized on the metallic structure and inspection plan has been modified and optimized with conventional NDT methods (US, ACFM, MT…)
In order to detect unknown fatigue cracks propagation or initiation, an Acoustic Emission monitoring has been installed on the two harbor cranes. Especially for areas where traditional nondestructive testing methods are difficult to use.
After the proof tests, a specific procedure has been defined to set the instrumentation. Then an appropriate signal processing has been developed using pattern recognition analysis with Noesis software to characterize and identify several AE sources as fretting noises due to crane rotation, in service shocks, mechanical impacts…
The AE results of the monitoring of the first months indicate the activity of sources that are correlated with propagating fatigue cracks detected by dye penetrant and ultrasonic in area where even visual inspection is sometime difficult to perform. AE has demonstrated also the ability to verify in such conditions if a known indication is propagating or not.
Acoustic Emission monitoring has been pushed forward as a very flexible and powerful nondestructive tool for in service monitoring of complex machinery as harbour cranes or overhead travelling cranes. Included in the inspection plan it gives information about the propagating defect in real time allowing to an efficient maintenance policy.
| Acoustic Emission |
The combined use of millimeter wave imaging and acoustic emission for the damage investigation of glass fiber reinforced polymer composites
K. Kalteremidou, A. Pourkazemi, Y. El idrissi, Y. Morabet, G. He, J. Stiens, L. Pyl6, D. Van Hemelrijck18
aDepartment of Mechanics of Materials and Constructions bDepartment of Electronics and Informatics cDepartment Mechanics of Materials and Constuctions; Vrije Universiteit Brussel (VUB) 54, Brussel [Belgium]
Acoustic emission, Composite materials, Terahertz imaging
Close
Polymer composite materials are used in numerous applications, including automotive and civil engineering. The mechanical behaviour and damage of composites is not as straightforward as that of more conventional materials, like metals. Different damage modes are developed depending on different parameters; material properties, lay-up and loading conditions. However, investigating the damage of composites with respect to all these parameters is of great importance if full characterization of the materials is necessary. Moreover, monitoring the damage of composites under different circumstances in lab conditions can be used as damage predictive tool in real applications and for the establishment of damage criteria. For all above reasons, Non-Destructive Techniques (NDTs) are usually used to monitor the damage of materials. Acoustic Emission (AE) is commonly used to distinguish damage modes of the composites by interpreting the elastic waves that generate in the material when it undergoes irreversible changes. AE is a powerful technique and by using relatively simple equipment, damage can be detected and characterized during loading. However, interpretation of the AE data is not so simple in the case of composites and most of the times it can provide qualitative but not quantitative conclusions. For this reason, in this research AE is combined with Millimeter Wave Imaging, which is an emerging method based on electromagnetic wave radiation within the 30 to 300 GHz band, enabling non-invasive, non-ionizing and non-contact examination of dielectric materials, like Glass Fiber Reinforced Polymers (GFRPs). The Millimeter Wave Imaging technique used in our research combines various advantages in comparison to other NDTs, like high resolution, high defect-detection and positioning capability, owing to its high penetration capability. In this research, the potential of combining the two NDTs, AE and Millimeter Wave Imaging for the damage characterization of GFRP flat specimens under tensile loads is investigated for the first time.
| Acoustic Emission |
ECNDT 2018, Additive Manufacturing – characterisation Investigation of fundamental ultrasonic propagation characteristics in NDT of Electron Beam Deposition additive manufactured samples
O. Tofeldt13, S. Pierce26, G. Smillie2, W. Kerr3, G. Flockhart2, C. MacLeod26, R. Blue2, A. Gachagan211, T. Stratoudaki24, J. Olsson12, D. McMahon32
1Production Technology Center (PTC); University of West2, Trollhättan [Sweden]
2aDepartment of Electronic & Electrical Engineering bCentre for Ultrasonic Engineering cSchool of Electrical and Electronic Engineering; University of Strathclyde33, Glasgow, Scotland [United Kingdom]
3Department of Electronic & Electrical Engineering; Advanced Forming Research Centre (AFRC)2, Renfrewshire [United Kingdom]
Propagagation and scattering, Ultrasonics
Close
New approaches for efficient NDT inspection of modern additively manufactured metallic components are required urgently to qualify and validate the next generation of metallic parts across a range of industries. Ultrasonic testing is a fundamental component of NDT for such additive manufacturing processes. This work studies the ultrasonic propagation characteristics of EBM manufactured sample coupons in Alloy 718 material. Fundamental longitudinal and shear wave velocity measurements are experimentally measured in 3 orthogonal build directions of the sample coupons. Results show a dependency of the ultrasonic velocities and the build direction. The measured velocities are further verified in a phased array measurement showing successful results that highlights the potential of continued studies with synthetic apertures techniques.
| Additive Manufacturing – characterisation |
ECNDT 2018, Additive Manufacturing – characterisation Subsurface Residual Stress Analysis in Ti-6Al-4V Additive Manufactured Parts by Synchrotron X-ray Diffraction
T. Mishurova16, K. Artzt24, S. Cabeza37, G. Requena211, G. Bruno121, J. Haubrich23
1BAM Federal Institute for Materials Research and Testing1265, Berlin [Germany]
2German Aerospace Center (DLR)7, Cologne [Germany]
3Institut Laue-Langevin4, Grenoble [France]
Stress, Tomography, X-ray diffraction
Close
Synchrotron X-ray diffraction is a powerful non-destructive technique for the analysis of the material stress-state. High cooling rates and heterogeneous temperature distributions during additive manufacturing lead to high residual stresses. These high residual stresses play a crucial role in the ability to achieve complex geometries with accuracy and avoid distortion of parts during manufacturing. Furthermore, residual stresses are critical for the mechanical performance of parts in terms of durability and safety.
In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process.
High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion.
| Additive Manufacturing – characterisation |
ECNDT 2018, Additive Manufacturing – characterisation An Assessment of Bulk and Surface Residual Stress in Selective Laser Melted Inconel 718
T. Thiede12, S. Cabeza27, T. Mishurova16, N. Nadammal12, A. Kromm13, J. Bode13, C. Haberland3, G. Bruno121
1aTest Devices and Equipment bDivision 8.5 Micro NDE; BAM Federal Institute for Materials Research and Testing1265, Berlin [Germany]
2Institut Laue-Langevin4, Grenoble [France]
3Siemens PG 12, Berlin [Germany]
Metals, Research, Stress, Stress visualization
Close
Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing.
The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate.
The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction.
| Additive Manufacturing – characterisation |
ECNDT 2018, Additive Manufacturing – radiographic methods Optimised Inspection of Complex Geometries
N. Brierley3
The Manufacturing Technology Centre (MTC)3, Coventry [United Kingdom]
Radiographic Testing (RT), data processing, image processing, research, Radiography, Theoretical Modelling
Close
The inspection of complex-shaped components, such as those enabled by additive manufacturing, is a major challenge in industrial quality assurance. The paper describes work seeking to address this challenge by the use of numerical optimisation coupled with a simulation capability as a means of incorporating prior knowledge about the inspection into the inspection design as a means of obtaining an improved capability. The focus of the work is radiographic imaging, but the algorithm described can readily be adapted to other image-based inspection modalities. The algorithm devolved is described, alongside the initial, promising results obtained.
| Additive Manufacturing – radiographic methods |
ECNDT 2018, Additive Manufacturing – various methods Simulation of NDT methods for Additive Manufacturing of composites
A. Martins, M. Carvalho, J. Cardoso, T. Santos9
Department of Mechanical and Industrial Engineering; NOVA University of Lisbon10, Caparica [Portugal]
Composite materials, Thermography
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Significant progress in Additive Manufacturing technologies, initially intended for rapid prototyping, provided the ability to produce finished parts with complex geometries and reduced cost. In addition, recently developed 3D printers have the capability to yield composite structures by adding a reinforcement material to a polymeric matrix. This improved material may then be used for structural applications that demand for Non-Destructive Testing (NDT).
NDT techniques usually require great effort and large number of experiments to achieve appropriate probes design and testing conditions. However, the cost efficiency of the NDT methods can be achieved through appropriate numerical modelling. The numerical simulation assists the design of customized NDT probes and allows deeper physical phenomena insight. Moreover, with the validated numerical models, it is possible to optimize the test parameters and predict the outcomes of different procedures, being these the advantages of including computational models in NDT methods research.
This work presents the analyses of numerical simulations to support the NDT methods for continuous carbon fibre reinforced polymer parts produced by a fused deposition modelling technology. The possible defects of these specific components that can be detected by NDT are the voids, fibre discontinuities and delamination, for which is required to develop a multiparametric system for the inspection. Moreover, several case studies were selected for experimental testing and model simulations of thermography, ultrasound and eddy current techniques were performed. Available Finite Element Method (FEM) commercial codes ANSYS and LS-Dyna where used for simulation of the physical phenomena associated with these NDT techniques. Furthermore, with the concern to maintain a reasonable computational cost, some efforts are made to make the numerical models efficient.
| Additive Manufacturing – various methods |
ECNDT 2018, Additive Manufacturing – various methods Non-Destructive Testing for Composites Produced by Additive Manufacturing
A. Pontes1, C. Simão2, J. Nunes1, J. Pinto3, J. Viana1, M. Ferreira3, T. Santos29
1Department of Polymer Engineering; University of Minho5, Guimarães [Portugal]
2Department of Mechanical and Industrial Engineering; NOVA University of Lisbon10, Caparica [Portugal]
3Department of Physics; University of Aveiro3, Aveiro [Portugal]
Composite materials, Eddy currents, Thermography
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Additive manufacturing (AM) using 3D printing is one of the most promising manufacturing technologies nowadays. However, the development of reliable Non-Destructive Testing (NDT) techniques for AM products is a big challenge. In fact, AM introduces new defect morphologies, dimensions and locations demanding new, and more reliable NDT techniques. These issue is even more pronounced in the case of AM of composites. In this case, possible defects that may arise include: delamination between matrix layers, lack of bonding between matrix and reinforcements, porosities (inter-filament discontinuity and path discontinuity), trapped support material between internal surfaces, misalignment of reinforcements or excessive surface roughness (staircase defect). Detecting such defects with existing NDT techniques presents major limitations as they were developed for other requirements and operational conditions.
This paper focuses on one of the most difficult challenges in NDT: the challenge of detecting defects in composite materials produced by Additive Manufacturing (AM), in particular, using continuous fibre reinforcement thermoplastics (FRTP). For those products, structural applications and safety requirements are envisaged, increasing the demand for NDT.
Four different NDT techniques were studied: active thermography, eddy currents, digital X-ray and ultrasound. Tests were performed in composite samples produced by Fused Deposition Modelling (FDM) AM containing different artificial defects, using polymeric matrix (PLA, ABS, Polyamide and PEEK) and continuous reinforcement fibres introduced externally (carbon and glass fibres and NiTi wires).
Active thermography with customized heat sources showed to be adequate for detecting voids and delaminations parallel to the surface, while X-ray and eddy currents with customized probes allow the identification of the NiTi wires and their arrangement inside polymeric matrix. Ultrasonic inspection presents major limitations due to the high acoustic attenuation of polymers (not so intense for PEEK) and due to high surface roughness when a 3D printing nozzle of 1.4 mm was used.
| Additive Manufacturing – various methods |
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