SwePub - sökning: WFRF:(Carlson Johan E. 1973 )

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1.	Carlson, Rolf, et al. (författare) The Study of Experimental Factors 2020. - 2 Ingår i: Comprehensive Chemometrics. - : Elsevier. ; , s. 251-285 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract The article presents methods for the study of experimental factors. The use of Ishikawa diagrams as tools for identifying relevant experimental variables is discussed. The construction and evaluation of two-level factorial and fractional factorial designs are presented in detail. Statistical properties of such designs are discussed. It is shown how the use of t-statistics and confidence intervals as well as how cumulative Normal probability plots can be used to identify significant variables. The methods are illustrated by examples from chemical experiments.
2.	Andersson, Tobias, et al. (författare) A machine vision system for estimation of size distributions by weight of limestone particles during ship loading 2012 Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 25:1, s. 38-46 Tidskriftsartikel (refereegranskat)abstract The size distribution as a function of weight of particles is an important measure of product quality in the mining and aggregates industries. When using manual sampling and sieving, the weight of particles is readily available. However, when using a machine vision system, the particle size distributions are determined as a function of the number of particles. In this paper we first show that there can be a significant weight-transformation error when transforming from one type of size distribution to another. We also show how the problem can be overcome by training a classifier and scaling the results according to calibrated average weights of rocks. The performance of the algorithm is demonstrated with results of measurements of limestone particles on conveyor belts.
3.	Ashraf, Asra, et al. (författare) Enabling High-speed Ultrasound Communication Through Thin Plates by Reverberation Suppression 2021 Ingår i: 2021 IEEE International Ultrasonics Symposium (IUS). - : IEEE. Konferensbidrag (refereegranskat)abstract In all digital communications, knowledge of the propagation channel between the transmitter and the receiver is essential. For transmitting of data through solid bodies, such as metal plates, pipe walls, etc., ultrasound is a viable alternative to radio communication and wired transmission. In ultrasound communication, the channel consists of two parts, the combined response of the transducers used as transmitter and receiver, and the impulse response of the propagation medium itself. For a thin plate with parallel surfaces, this results in a reverberating channel that significantly reduces the achievable bitrate if not handled properly. In this paper we show with simulations how the bit-error rate in Orthogonal Frequency Division Multiplexing (OFDM) communications, is affected by the reverberating nature of the plate, and how this can be overcome by the introduction of a channel shortening filter placed in front of the OFDM conventional receiver. The results show that this significantly reduces the bit-error rate, especially for thin plates. If the reverberations instead were to be compensated by the conventional channel equalization method in OFDM, we show that for the example in the simulations, the bitrate would drop by almost 25 %, from about 3.9 Mbit/s to about 2.9 Mbit/s.
4.	Ashraf, Asra, 1989-, et al. (författare) The solid-body reverberating ultrasound communications channel and its OFDM interference 2022 Ingår i: 2022 IEEE Latin-American Conference on Communications (LATINCOM). - : Institute of Electrical and Electronics Engineers (IEEE). Konferensbidrag (refereegranskat)abstract In this paper we present an analytical approach to the solid-state ultrasound communications channel. Channel reverberations and the long associated channel delay spreads pose the possibility that the channel length exceeds that of the moderate cyclic prefix in an orthogonal frequency division multiplexing (OFDM) system, resulting in intersymbol and intercarrier interference. We present a channel model based on the propagation material characteristics and evaluate the extent and impact of the intrinsic OFDM interferences. We derive an analytical expression and show with simulations that the intersymbol and intercarrier interference (ISI and ICI) are spectrally concentrated to the lower frequencies of the OFDM multiplex.
5.	Ashraf, Asra, et al. (författare) Ultrasound Communication Through Thin Plates: Understanding and Estimating the Channel 2022 Ingår i: 2022 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781665466578 Konferensbidrag (refereegranskat)abstract As with all digital communications, understanding the propagation channel is essential. In this paper we present an analytical model of a channel consisting of a thin plate, including effects of frequency-dependent speed of sound and attenuation. We show how a compressed sensing approach can be used to estimate this channel impulse response from real measurements, even for cases when the plate thickness causes the reverberating pulses to overlap. The estimate can be seen as a sparsity constrained deconvolution of the combined impulse responses of the transmitting and receiving transducers. We then show with simulations that the proposed sparsity-constrained estimate is able to cope also in the presence of dispersion. We also analyze the performance of the proposed method both with simulations and experiments on 6 mm and 2 mm thick glass plate and 3 mm thick aluminum plate, and our results show that the model assumptions seems to hold.
6.	Ashraf, Asra, 1989- (författare) Ultrasound Communication through Thin Plates: Understanding the Channel 2023 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Ultrasound, composed of sound waves with frequencies above the human audible range, has become widely used in various technological ﬁelds for digital communications. In the past, acoustic and ultrasonic waves were employed in military and commercial un-derwater wireless communication systems due to their superior performance compared to electromagnetic waves. Ultrasound has also emerged as a viable alternative to radio and wired transmission for data transmission through solid bodies like metal plates and pipe walls. Notably, ultrasound oﬀers high-security features as it is nearly undetectable from outside the room, minimizing the risks of wireless interception and attacks like Bluesniping and jamming.In any digital communication system, understanding the propagation channel between the transmitter and receiver is crucial. The ultrasound communication channel comprises three main components: transmitting and receiving transducers and the medium through which the sound propagates. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier scheme that divides the available spectrum into multiple non-overlapping subcarriers for digital communication.In the context of ultrasound communication, the channel consists of two parts: the combined response of the transducers used as the transmitter and receiver, and the im-pulse response of the propagation medium. When dealing with a thin plate with parallel surfaces, this results in a reverberating channel. The reverberating channel comprises a primary pulse along with echo pulses that possess similar shapes but decaying amplitudes. The amplitude decay occurs due to four prominent factors: power losses in the trans-ducers at each side, transmission losses at the boundaries of the plate and transducer, ultrasound pulse attenuation within the plate, and beam spreading as the ultrasound pulse travels over distance. The reverberations elongate the impulse response of the channel, thus require a long cyclic preﬁx to prevent data symbols to overlap. However, this limitation restricts the achievable bit rate and energy eﬃciency of the system.In this thesis, we present a model for the reverberating ultrasound channel suitable for various plate materials. We propose a novel system-level path loss model that accounts for losses at the transducers, transmission losses, material attenuation, and diﬀraction losses. Based on this model, we calculate a comprehensive link budget that explicitly considers plate thickness. Furthermore, we conduct a quantitative analysis to evaluate the impact of Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) on the performance of the OFDM system. Through computer simulations, we evaluate the system’s performance and demonstrate that for a metal plate with a thickness of 5 mm, an uncoded data rate of 32 Mbps can be achieved.
7.	Carlson, Johan E., 1973-, et al. (författare) A Subspace Based Method for Near Transducer Interference Suppression 2018 Ingår i: 2018 IEEE International Ultrasonics Symposium. - : IEEE. - 9781538634257 - 9781538634264 Konferensbidrag (refereegranskat)abstract In applications of direct -contact ultrasound, operating in pulse -echo mode, the transient resulting from the excitation of the transducer will mask any reflections from scatterers near the transducer surface. This results in a so called dead zone, preventing any defects to be detected. This is normally solved by introducing a delay line between the transducer and the specimen. There are drawbacks with this approach, and therefore we propose an alternative technique, which instead suppresses the transient from the excitation by a statistical modeling technique. This paper describes an algorithm for reduction of the dead zone and shows with experiments using both a single -element transducer and a 128 element linear array, that the transient from the transducer excitation can be suppressed sufficiently well to reveal side -drilled holes in a test block, which were previously masked.
8.	Carlson, Johan E., 1973- (författare) Bringing an Old Topic to Life by Changing the Way it is Taught : Reinventing a course in Measurement Systems Engineering 2020 Ingår i: Bidrag från 7:e utvecklingskonferensen för Sveriges ingenjörsutbildningar. - : Luleå tekniska universitet. ; , s. 200-201 Konferensbidrag (refereegranskat)abstract This paper describes the ongoing work to reform teaching of (Electrical) Measurement Systems Engineering, in order to put more emphasis on the students as active learners, better prepared to take on responsibilities of a modern engineer. The paper describes how the development of generic engineering skills are incorporated in the context of the technical subject.
9.	Carlson, Johan E., 1973-, et al. (författare) High Resolution Image Reconstruction from Full-Matrix Capture Data Using Minimum Mean Square Error Deconvolution of the Spatio-Temporal System Transfer Function 2020 Ingår i: 2020 IEEE International Ultrasonics Symposium (IUS). - : IEEE. Konferensbidrag (refereegranskat)abstract The resolution of ultrasound images generated withconventional delay-and-sum beamformers, such as for examplethe Total Focusing Method (TFM), is limited by the overall systemtransfer function (point-spread function). This limits, for examplethe minimum distance between defects that can be detectedwithout the defects showing up as one larger peak in the image.In this paper, we propose a technique based on modeling ofthe complete spatio-temporal transfer function of the imagingsystem, that efficiently suppresses this and thus increases theimage resolution substantially. The method is demonstrated withsimulations and compared with the TFM.
10.	Carlson, Johan E., 1973-, et al. (författare) Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique 2017 Ingår i: IEEE International Ultrasonics Symposium, IUS. - : IEEE Computer Society. - 9781538633830 - 9781538633847 Konferensbidrag (refereegranskat)abstract When investigating thin materials with pulse echo ultrasound, multiple reflections (reverberations) from the layer(s) will overlap. It is therefore difficult to deduce information about speed of sound, thickness, density, etc. from the raw data. In order to extract this information, the overlapping pulses must be either decoupled or we must find some model of the material sample describing the wave propagation. It is, however, often reasonable to assume that the the number of reflections is small relative to the number of samples in the record signal of interest. In other words, the system describing the reverberations is sparse. In this paper we investigate, with simulations and with experiments on a 4.8 and 2.2 mm thick glass plate, respectively, how the framework of compressed sensing can be adopted in order to retrieve the impulse response of the material specimen
11.	Carlson, Johan E., 1973-, et al. (författare) Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique 2017 Ingår i: IEEE International Ultrasonics Symposium, IUS. - : IEEE Computer Society. - 9781538633830 - 9781538633847 Konferensbidrag (refereegranskat)abstract In ultrasound examination of thin multi-layered materials, the received signal is, in both through-transmission and pulse-echo configurations, a superposition of multiple reflections from inside the sample. If the layer thicknesses are small compared to the duration of the emitted ultrasound pulse, the received signal will be a sum of overlapping ultrasound pulses. In such scenarios, estimation of the layer thicknesses is challenging. Previous work has adopted model-based decomposition of the overlapping echoes, or various pulse compression or deconvolution schemes, in order to better reveal the arrival times of each individual echo.
12.	Carlson, Johan E., 1973-, et al. (författare) Modeling of the Stress-Strain Relationship of Rock Bolts from Ultrasound Data 2021 Ingår i: 2021 IEEE International Ultrasonics Symposium (IUS). - : IEEE. Konferensbidrag (refereegranskat)abstract Load-bearing structural elements such as rock bolts and reinforcing bars (rebar) are ubiquitously present in both mining industries and in infrastructure projects, for securing tunnel walls and ceilings. Being able to detect and localize defects in previously installed rock bolts, or even quantitatively estimate the load they are taking, would be very valuable when planning maintenance and service. Unfortunately, there are no such techniques available today. Previous work shows that ultrasound, being a mechanical wave, is sensitive to mechanical changes in rock bolts. The ultrasound signature is, however, rather complex, and traditional modeling of the wave propagation rapidly becomes challenging. In this paper, we show that the ultrasound signature measured from a 3.2 m long dynamic rock bolt can be used to accurately determine the load applied to the bolt and the resulting elongation of the bolt. The method is based on training a Partial Least Squares Regression (PLSR) model to estimate the force an elongation from power spectra of backscattered ultrasound signatures.
13.	Carlson, Johan E., 1973-, et al. (författare) Monitoring Changes in Mechanical Properties of Rock Bolts Using a Low-Power Coded-Excitation Scheme 2018 Ingår i: 2018 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS). - : IEEE. - 9781538634257 - 9781538634264 Konferensbidrag (refereegranskat)abstract In-situ inspection and quality assessment of rock bolts and other load-bearing structural elements, has received significant attention over the years, but there are still no techniques available capable of monitoring changes over time in mechanical properties of already installed bolts. Since mechanical changes will also affect the propagation of mechanical waves, ultrasound is a strong candidate. In this paper we propose a technique based on Orthogonal Frequency Division Multiplexing (OFDM) for coding the transmitted ultrasound pulse in such a way that the propagation channel (transducer and rock bolt combined) can be estimated. We show that a transmit voltage of 1.1 V r.m.s. is sufficient to obtain reliable channel estimates even in bolts as long as one meter. The channel estimates are then used to predict changes in tensile stress on the bolt, from experiments conducted in a laboratory environment.
14.	Carlson, Johan E., 1973-, et al. (författare) Ulraljudsmetod för mätning av belastning på bergbultar : [Ultrasound Method for Measurement of Load on Rock Bolts] 2022 Konferensbidrag (refereegranskat)abstract Inom både gruvindustri och infrastrukturprojekt är tillståndskontroll av bergbultar av stort intresse. Det finns dedikerade mätbultar som kan installeras för att detektera och följa förändringar över tid. Det finns även metoder för att kontrollera ingjutningen av bultar vid installation. Däremot saknas idag mätmetoder för att följa tillståndet hos generiska bergbultar över tid, eller för att detektera avvikelser bland sedan tidigare installerade bultar.I detta projekt utvecklas en metod baserad på ultraljud för att följa förändringar i mekaniska egenskaper över tid och för att kunna detektera avvikande bultar i en population av redan installerade bultar. Metoden bygger på en kort ultraljudspuls skickas in i bulten från den fria änden och att en reflekterat ljud från hela bultens längd samlas in. Detta fingeravtryck av bulten kan sedan jämföras bultar emellan, eller följas för en enskild bult över tid.För att demonstrera principen visar vi hur uppmätta ultraljudssignaturer kan användas för att modellera hela dragprovskurvan (kraft mot töjning), från vila till brottgräns för en c:a 3 meter lång dynamisk bergbult.
15.	Gupta, Payal, et al. (författare) Deep Learning for Modeling of Sound Pressure Fields of Real-World Ultrasound Transducers 2022 Ingår i: 2022 IEEE International Ultrasonics Symposium (IUS). - : IEEE. Konferensbidrag (refereegranskat)abstract There are several freely available toolboxes for modeling the sound pressure field of ultrasound transducers and transducer arrays (e.g., Field II, k-Wave, and DREAM, etc.). These model the beam patterns, or how the ultrasound pulse changes depending on where we observe it, i.e., they model the spatial impulse response of the transducers. Normally, the transmitted pulse is not modeled using these toolboxes, but instead it is assumed that this pulse shape is known. Also, the models are based on assumption of an ideal behavior of the transducers, which is not necessarily the case for a real-world transducers. As a consequence, fitting these models to real measurement data, in order for them to mimic the individual transducer available in the lab, is not generally not possible with any numerical accuracy. In this paper we show, instead, how a deep learning approach can be adopted to train a model that with numerical accuracy models an transducer individual. We compare the proposed technique with real measurements and models using the Field II toolbox and show that for the actual transducer at hand, the deep learning approach outperforms the results from Field II.
16.	Lei, Xiangyu, 1992, et al. (författare) Model-Based Parametric Study of Surface-Breaking Defect Characterization Using Half-Skip Total Focusing Method 2023 Ingår i: Journal of nondestructive evaluation. - : Springer Nature. - 0195-9298 .- 1573-4862. ; 42:2 Tidskriftsartikel (refereegranskat)abstract As the demand of structural integrity in manufacturing industries is increasing, the ultrasonic array technique has drawn more attention thanks to its inspection flexibility and versatility. By taking advantage of the possibility of individual triggering of each array element, full matrix capture (FMC) data acquisition strategy has been developed that contains the entire information of an inspection scenario. Total focusing method (TFM) as one of the ultrasonic imaging algorithms, is preferably applied to FMC dataset since it uses all information in FMC to synthetically focus the sound energy at every image pixel in the region of interest. Half-skip TFM (HSTFM) is proposed in multi-mode TFM imaging that involves a backwall reflection wave path, so that the defect profile could be reconstructed for accurate defect characterization. In this paper, a method involving Snell’s law-based wave mode conversion is proposed to account for more reasonable wave propagation time when wave mode conversion happens at backwall reflection in HSTFM. A series of model based simulations (in software simSUNDT) are performed for parametric studies, with the intention of investigating the capability of defect characterization using HSTFM with varying tilt angle and relative position of surface-breaking notch to array probe. The results show that certain TFM modes could help with defect characterization, but the effectiveness is limited with varying defect features. It is inappropriate to address a certain mode for all characterization perspectives but rather a combination, i.e., multi-mode TFM, should be adopted for possible interpretation and characterization of defect features.
17.	Lei, Xiangyu, et al. (författare) The effect of ultrasound wave path estimation to defect characterization capability in half-skip total focusing method 2023 Ingår i: Research and Review Journal of Nondestructive Testing (ReJNDT). - : NDT.net. - 2941-4989. ; 1:1 Tidskriftsartikel (refereegranskat)abstract The total focusing method (TFM) is a post-processing imaging technique applied on full matrix capture (FMC) ultrasonic inspection (UT) dataset. In TFM the ultrasonic wave energy is synthetically focused on every pixel in the image region of interest (ROI). In terms of half-skip TFM (HSTFM), wave mode conversion happens when the wave rebounds at interface, such as specimen backwall. This paper aims to propose and evaluate a method that involves Snell’s law to address accurate estimation of distanceof-flight (DOF) of wave propagation when wave mode conversion appears in HSTFM. This HSTFM algorithm is applied to both experimental and simulated FMC dataset that inspects a surface-breaking notch for notch image reconstruction. Comparisons between images with and without considering Snell’s law in wave mode conversion show visible difference that could lead to misinterpretations in characterizing the defect. The sensitivity of TFM to varying defect features such as defect tilt angle is also studied using simulated FMC datasets.
18.	Lemlikchi, Safia, et al. (författare) Parametric estimation of overlapping echoes reflected from coated media 2021 Ingår i: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 178 Tidskriftsartikel (refereegranskat)abstract In this work, a parametric modeling strategy was used to investigate ultrasonic signals reflecting from coated structures. The model parameter vector is defined by the combined model consisting of hard and soft modeling. The hard model describes the overlap with pure delays, reflection and transmission coefficients. The soft model copes with a more realistic case when all ultrasonic losses are included. The estimation procedure follows the maximum likelihood approach and uses the Levenberg–Marquardt algorithm for optimizing the objective function. The tested waveforms were reflected from thermally sprayed Diamalloy 4060 coatings deposited on 310SS substrate with increasing degree of overlapping echoes. Measurements were carried out in pulse-echo mode using a 15 MHz nominal frequency transducer. A good prediction of overlapping signals was achieved. Reverberating coating echoes were successfully separated and coating properties (time-of-flight (TOF), ultrasonic velocity and attenuation) were directly deduced. Results show the potential of the method to investigate overlapping ultrasonic signals reflecting from highly attenuating layers such as thermal sprayed coatings. It also shows the ability for the method to make a complete separation of the overlapping echoes, not only between the substrate and the coating echoes, but also between the reverberations in the coating itself that has been neglected for a long time. This allows an accurate characterization of the coating properties.
19.	Lemlikchi, Safia, et al. (författare) Ultrasonic Characterization of Thermally Sprayed Coatings 2019 Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 28:3, s. 391-404 Tidskriftsartikel (refereegranskat)abstract This paper describes the simultaneous determination of the ultrasonic parameters in thermally sprayed coatings. The parameters of interest are the longitudinal wave velocity and the ultrasonic attenuation. The test materials are two cobalt-based coatings (FSX 414 and Diamalloy 4060), both deposited onto stainless steel (310SS) substrates. The ultrasonic measurements were carried out in the pulse-echo configuration using several transducers. The ultrasonic signals reflected from the coatings were successfully estimated using the combined model, together with the maximum likelihood estimation and the Levenberg–Marquardt approach. The best estimate was obtained for 20 MHz measurements. Once the model was validated, the ultrasonic parameters of the thermally sprayed coatings were extracted. Model validation is based on the analysis of the residual between measured and estimated signals. Results showed non-dispersive ultrasonic velocities with average values of (3940±50)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(3940±50)m/s(3940±50)m/s in Diamalloy 4060 and (4260±20)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(4260±20)m/s(4260±20)m/s in FSX 414. High ultrasonic attenuation with a quadratic frequency dependence was observed for both materials. Moreover, it was found that the ultrasonic parameters in thermally sprayed materials are microstructure dependent. For close densities, the harder the coating, the higher the ultrasonic wave velocity and attenuation.
20.	Onur, Tuğba Özge, et al. (författare) Estimation of the Propagation of Flexural Waves in Thin Plates Using a Single Low Cost Sensor 2019 Ingår i: Iranian Journal of Science and Technology, Transactions of Electrical Engineering. - : Springer. - 2228-6179 .- 2364-1827. ; 43:3, s. 405-413 Tidskriftsartikel (refereegranskat)abstract This paper demonstrates how flexural wave propagation in a thin plate can be modeled by estimating the combined effect of the excitation source signal and the impulse response of the ultrasonic sensor. The wave propagation in the plate is modeled using the wave equation for the flexural wave mode. A theoretical model for flexural wave propagation in thin plates has been derived, and it has been compared with measurements excited by tapping gently on the surface. The combined effects of the excitation source signal and the impulse response of the low-cost piezoelectric sensor are modeled using finite-impulse response and/or infinite-impulse response filters. Thereafter, the performances of the selected filters are compared on estimating the wave propagation in a thin quartz glass plate. Results indicate that the most accurate estimation of wave propagation has been obtained using a linear phase filter which attributes all dispersions to the flexural wave.
21.	Zia, Shafaq, et al. (författare) Estimating manufacturing parameters of additively manufactured 316L steel cubes using ultrasound fingerprinting 2023 Ingår i: Research and Review Journal of Nondestructive Testing (ReJNDT). - : NDT.net. - 2941-4989. ; 1:1 Tidskriftsartikel (refereegranskat)abstract Metal based additive manufacturing techniques such as laser powder bed fusion (LPBF) can produce parts with complex designs as compared to traditional manufacturing. The quality is affected by defects such as porosity or lack of fusion that can be reduced by online control of manufacturing parameters. The conventional way of testing is time consuming and does not allow the process parameters to be linked to the mechanical properties. In this paper, ultrasound data along with supervised learning is used to estimate the manufacturing parameters of 316L steel cubes. Nine cubes with varying manufacturing parameters (speed, hatch distance and power) are examined with ultrasound using focused transducers. The volumetric energy density (VED) is calculated from the process parameters for each cube. The ultrasound scans are performed in a dense grid in the built and transverse direction. The ultrasound data is used in partial least square regression algorithm by labelling the data with speed, hatch distance and power and then by labelling the same data with the VED. These models are computed for both measurement directions and as the samples are anisotropic, we see different behaviours of estimation in each direction. The model is then validated with an unknown set from the same 9 cubes. The manufacturing parameters are estimated and validated with a good accuracy making way for online process control.
22.	Zia, Shafaq, et al. (författare) Linking Ultrasound Data to Manufacturing Parameters of 3D-printed Polymers Using Supervised Learning 2022 Ingår i: 2022 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781665466578 Konferensbidrag (refereegranskat)abstract Additive manufacturing is used to produce complex and tailored products that cannot be achieved using conventional manufacturing approaches. The products can be made from different materials including polymers, metals, etc. The material is added layer by layer to create a final product. The mechanical properties of the final part depend on the process parameters. To improve the quality of the product these manufacturing parameters need to be optimised and for this purpose machine learning along with ultrasound measurements can be used. In this paper, the manufacturing parameters of 50 mm thick polymer cubes are linked to the ultrasound data using partial least squares regression. Three cubes with varying layer heights are made from PLA and ABS each, and backscattered responses of ultrasound are recorded from these six cubes. The ultrasound data is used in the partial least squares algorithm to estimate the layer height and the filament type. The clusters that are formed using the first few components obtained from the algorithm show that the data points of the six cubes can be distinguished and themanufacturing parameters are estimated with good accuracy.
23.	Zia, Shafaq (författare) Non-destructive assessment of additively manufactured objects using ultrasound 2024 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Additive manufacturing (AM) enables the manufacturing of complex and tailored products for an unlimited number of applications such as aerospace, healthcare, etc. The technology has received a lot of attention in lightweight applications where it is associated with new design possibilities but also reduced material costs, material waste, and energy consumption. The use of ultrasound has the potential to become the material characterization method used for AM since it is quick, safe, and scales well with component size. Ultrasound data, coupled with supervised learning techniques, serves as a powerful tool for the non-destructive evaluation of different materials, such as metals.This research focuses on understanding the additive manufacturing process, the resulting material properties, and the variation captured using ultrasound due to the manufacturing parameters. The case study included in this thesis is the examination of 316L steel cubes manufactured using laser powder bed fusion. This study includes the estimation and prediction of manufacturing parameters using supervised learning, the assessment of the influence of the manufacturing parameters on the variability within samples, and the quantitative quality assessment of the samples based on the material properties that are a result of the changes in manufacturing parameters.The research is vital for analyzing the homogeneity of microstructures, advancement in online process control, and ensuring the quality of additively manufactured products. This study contributes to valuable insights into the relationship between manufacturing parameters, material properties, and ultrasound signatures. There is a significant variation captured using ultrasound within the samples and between samples that shows the backscattered signal is sensitive to the microstructure that is a result of the manufacturing parameters. Since the material properties change with the change in manufacturing parameters, the quality of a sample can be described by the relation between the material properties and backscattered ultrasound signals.The thesis is divided into two parts. The first part focuses on the introduction of the study, a summary of the contributions, and future work. The second part contains a collection of papers describing the research in detail.
24.	Zia, Shafaq, et al. (författare) On Estimation of Sound Velocity and Attenuation in Common 3D-Printing Filaments 2022 Ingår i: 2022 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781665466578 Konferensbidrag (refereegranskat)abstract Estimation of frequency-dependent attenuation and speed of sound using ultrasound is of great importance. The acoustic properties can be used for material characterization and to study the local variations in a solid. As ultrasound is a mechanical wave, it is directly sensitive to changes in the material properties. The layered nature of additively manufactured prod-ucts pose a challenge for the estimation of acoustic properties. The non-parametric approaches using frequency transforms are sensitive to noise. In this paper, a parametric model is used to estimate the phase velocity and attenuation of 3D-printed cubes. The received signal from the cubes is a superposition of the backscattered responses from multiple layers of the printed part. A reference echo from aluminium is used as an input to the linear model and to estimate the received ultrasound response. The estimate of the ultrasound signal using the linear model is similar to the measured data and it suggests that it can be used to estimate wave propagation in additively manufactured products. The estimated acoustic properties show an increasing trend with the frequency and dispersion can be seen due to the layered nature of the material.
25.	Zia, Shafaq, et al. (författare) Prediction of manufacturing parameters of additively manufactured 316L steel samples using ultrasound fingerprinting 2024 Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 137 Tidskriftsartikel (refereegranskat)abstract Metal based additive manufacturing techniques such as laser powder bed fusion can produce parts with complex designs as compared to traditional manufacturing. The quality is affected by defects such as porosity or lack of fusion that can be reduced by online control of manufacturing parameters. The conventional way of testing is time consuming and does not allow the process parameters to be linked to the mechanical properties. In this paper, ultrasound data along with supervised learning is used to estimate the manufacturing parameters of 316L steel samples. The steel samples are manufactured with varying process parameters (speed, hatch distance and power) in two batches that are placed at different locations on the build plate. These samples are examined with ultrasound using a focused transducer. The ultrasound scans are performed in a dense grid in the build and transverse direction, respectively. Part of the ultrasound data are used to train a partial least squares regression algorithm by labelling the data with the corresponding manufacturing parameters (speed, hatch distance and power, and build plate location). The remaining data are used for testing of the resulting model. To assess the uncertainty of the method, a Monte-Carlo simulation approach is adopted, providing a confidence interval for the predicted manufacturing parameters. The analysis is performed in both the build and transverse direction. Since the material is anisotropic, results show that there are differences, but that the manufacturing parameters has an effect of the material microstructure in both directions.

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