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- 2019
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Journal article (peer-reviewed)
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| 2. |
- Jiang, Biao, et al.
(author)
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Ultrasonic Imaging Through Thin Reverberating Materials
- 2015
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In: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 70, s. 380-383
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Journal article (peer-reviewed)abstract
- Imaging through anisotropic or highly heterogeneous materials is challenging for the existence of strong boundary and volume reverberations. To image small cracks or flaws in a reverberating thin layers, high resolution techniques are needed in both temporal and spatial domain, so that the reverberation can be suppressed to some level. In this paper, the reverberation suppression performance of the total focusing beamforming method (TFM) was evaluated by simulation and real data processing. The results showed that the more the focusing point moves away from the array central line, the more multi-reflections can be suppressed. Furthermore, TFM combined with adaptive processing greatly improves the small flaw detection performance. Test results on real samples confirmed the robustness and reverberation suppression capability of the TFM imaging method.
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| 3. |
- Landahl, Jonas, 1986, et al.
(author)
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Using product and manufacturing system platforms to generate producible product variants
- 2016
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In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 61-66
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Conference paper (peer-reviewed)abstract
- Product platforms have proven efficient as a means to reduce lead-time and increase product quality simultaneously. When using platforms to generate a family of products, the number of variants that need to be managed in manufacturing increases. To succeed with this, the manufacturing system needs to be maintained in a similar level of flexibility as the product platform. However, there is seldom a joint decision behind each and every conceptual product variant during development, regarding capability in manufacturing. For example, when considering producibility, some product variants require better tolerances than what the manufacturing processes can deliver. This uncertainty can be reduced, by making producibility analyses of a set of conceptual product variants. By performing several different analyses, knowledge can be gained, and joint decisions can be made about cross product-manufacturing aspects. The activities can be systematically arranged to gradually eliminate unfeasible conceptual product variants. In this paper we show how an integrated PLM architecture can be used to create sufficient knowledge as a basis for joint product and manufacturing decisions. The utmost company benefit of this is to reduce lead-time by taking manufacturing capability into account when developing product families.
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| 4. |
- Carlson, Johan E., 1973-, et al.
(author)
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A Subspace Based Method for Near Transducer Interference Suppression
- 2018
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In: 2018 IEEE International Ultrasonics Symposium. - : IEEE. - 9781538634257 - 9781538634264
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Conference paper (peer-reviewed)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.
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| 5. |
- Carlson, Johan E., 1973-, et al.
(author)
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Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique
- 2017
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In: IEEE International Ultrasonics Symposium, IUS. - : IEEE Computer Society. - 9781538633830 - 9781538633847
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Conference paper (peer-reviewed)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
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| 6. |
- Carlson, Johan E., 1973-, et al.
(author)
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Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique
- 2017
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In: IEEE International Ultrasonics Symposium, IUS. - : IEEE Computer Society. - 9781538633830 - 9781538633847
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Conference paper (peer-reviewed)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.
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| 7. |
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| 8. |
- Carlson, Johan E., 1973-, et al.
(author)
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Monitoring Changes in Mechanical Properties of Rock Bolts Using a Low-Power Coded-Excitation Scheme
- 2018
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In: 2018 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS). - : IEEE. - 9781538634257 - 9781538634264
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Conference paper (peer-reviewed)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.
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| 9. |
- Jacobson, Karin, et al.
(author)
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Non-Destructive Testing of Plastics and Composites in the Chemical Processing Industry
- 2016
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Conference paper (peer-reviewed)abstract
- Equipment and components made of plastics and composites are widely used in highly corrosive environments in the processing industry. Examples are the storage tanks, pumps and pipes for chemical transport and stacks in combustion plants. The demand for reliable nondestructive testing of plastic process equipment has increased significantly in recent years. Glass fiber reinforced plastics (GRP) is a common construction material for process equipment in the chemical industry. It can be used both as structural bearing in a dual laminate with a thermoplastic material as a corrosion barrier or as a solid GRP. In the latter case, the laminate is generally built up with a resin rich corrosion barrier (about 2.5 to 5 mm thick) with a low content of glass closest to the chemical. The glass fiber in this layer is usually a surface veil and chopped strand mats (CSM), i.e. it has no general fiber orientation. Outside this is the structural bearing layer with much higher glass content, usually wound fiber and / or woven fiber mats with a preferential fiber direction. The corrosion barrier is not load bearing and corrosion of this layer can be allowed. However, no corrosion can be permitted in the structural support layer. Because of this it is important to measure the thickness of the corrosion barrier for quality control but also to determine how far an attack has reached in the corrosion barrier. Today there is no non-destructive testing method that can answer this. Instead destructive sampling (often a drill core) must be made. This is difficult, expensive and sometimes impossible. There is thus a great interest in a method that, preferably at any time during operation, can provide answers to these questions. Due to the heterogeneity of the GRP material in terms of amount, type and direction of the fibers, conventional algorithm for ultrasound imaging will not work. One aim of our work is thus to develop new signal processing methods to handle this heterogeneity. In addition we are also looking at the possibility to use optical fibers and Fiber Bragg Grating (FBG) sensors for corrosion monitoring of GRP structures
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| 10. |
- Lemlikchi, Safia, et al.
(author)
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Ultrasonic Characterization of Thermally Sprayed Coatings
- 2019
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In: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 28:3, s. 391-404
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Journal article (peer-reviewed)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.
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