Author
Sarah Johannesmann
Bio: Sarah Johannesmann is an academic researcher from University of Paderborn. The author has contributed to research in topics: Ultrasonic sensor & Orthotropic material. The author has an hindex of 4, co-authored 15 publications receiving 51 citations.
Papers
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TL;DR: The application of laser‐induced ultrasonic Lamb waves for the characterization of fiber‐reinforced plastic plates is demonstrated, providing effective parameters for a homogeneous, orthotropic material model.
17 citations
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01 Sep 2016TL;DR: In this article, the authors demonstrate the application of this method for fiber-reinforced plastics, identifying effective parameters for a homogeneous, orthotropic material model for non-destructive material characterization.
Abstract: Ultrasonic measurement techniques are widely used for non-destructive detection of material defects. However, material properties, such as Young's modulus, are still mostly determined destructively, especially for materials with high damping or strong anisotropy. One method for non-destructive material characterization creates and detects ultrasonic waves in plate-shaped specimens, so that the material's influence on wave propagation can be evaluated. In this contribution, we demonstrate the application of this method for fiber-reinforced plastics, identifying effective parameters for a homogeneous, orthotropic material model.
10 citations
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03 Oct 2019
TL;DR: In this paper, a method to quantify absorption and dissipation phenomena with arbitrary frequency dependence is presented using the raw moments of the signals from acoustic transmission measurements, and the method is applied to signals generated using acoustic field simulation with different absorption models.
Abstract: Of all fluid and solid properties, quantities that describe losses are among the most challenging to quantify. In part, this is due to superimposed dissipative mechanisms, such as diffraction effects from spatially limited sources. Inherent to all these phenomena, however, is a specific frequency dependence. The nature of the frequency dependence varies, resulting from the respective absorption mechanism. Pure fluids, for example, exhibit absorption of acoustic waves with quadratic frequency dependence[1]. In solids, there are several absorption models that can be applied, each having different characteristics with respect to frequency. Other dissipative effects, such as diffraction, also show frequency dependence. In an approach using the raw moments of the signals from acoustic transmission measurements, a method to quantify absorption and dissipation phenomena with arbitrary frequency dependence is presented. The described method is applied to different absorption measurement problems. To verify that accurate results can be achieved under ideal conditions, the method is applied to signals generated using acoustic field simulation with different absorption models. To show its numerical stability, it is used qualitatively to evaluate the absorption of a fluid at different thermodynamic states.
6 citations
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09 Dec 2019
TL;DR: In this paper, a new approach, Lamb wave mode repulsion is used to obtain the coupling strength between different layers to characterise the adhesive bonding strength, and their interaction in two-layered plate-like structures with varying coupling strength both numerically, with the Scaled Boundary FEM, and experimentally.
Abstract: Lamb waves are widely used for non-destructive evaluation of material parameters as well as for detection of defects. Another application of Lamb waves is quality control of adhesive joints. Researchers are currently investigating shear horizontal and zero-group velocity modes for characterisation of the adhesive bonding strength. In a new approach, Lamb wave mode repulsion is used to obtain the coupling strength between different layers to characterise the adhesive bonding strength. The modes of the individual layers become coupled in the multi-layered systems forming particular regions, the so-called mode repulsion regions. This study investigates these modes and their interaction in two-layered plate-like structures with varying coupling strength both numerically, with the Scaled Boundary FEM, and experimentally.
6 citations
01 Jan 2017
TL;DR: In this paper, a non-destructive measurement procedure is presented to characterize the properties of additively manufactured components by using focused laser radiation, broadband ultrasonic Lambwave are excited in the plates via the photoacoustic effect.
Abstract: Additively manufactured or 3d printed components are commonly used for rapid prototyping or small series production purposes. Their mechanical properties, especially in the acoustic regime, are sparsely researched as of now. Therefore, we present a non-destructive measurement procedure to characterize the properties of additively manufactured components. We manufacture thick plates by fused deposition modeling of polylactic acid (PLA). Using focused laser radiation, broadband ultrasonic Lambwaves are excited in the plates via the photoacoustic effect. These waves are detected using a purposebuilt ultrasonic transducer for plate waves. The measurement signals processed are compared to the output of a plate waveguide model. In an inverse procedure, the material parameters of the model are optimized to yield estimates for the material properties of the sample. Using this approach, we analyze the influence of printing process parameters on the mechanic and acoustic properties of the manufactured specimens.
6 citations
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261 citations
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TL;DR: In this article, an ultrasonic-based method for the determination of the elastic constants of the Inconel 625 (IN625) material as manufactured via the laser powder-bed fusion process (L-PBF) is presented.
Abstract: The nature of additive manufacturing (AM) processes prescribes direction-dependent properties of the final parts. The degree of material anisotropy is highly dependent on the process parameters and the machine setup which complicates the design of AM parts. A basic problem in the design and quality control of parts and components manufactured by the AM processes is the evaluation of the resulting elastic properties, specifically along the principal directions. In a destructive testing approach, many specimens in the principal directions are normally required to determine the elastic properties of a material. However, an alternative low-cost method based on the ultrasonic wave propagation velocities can also be used for this purpose. In this article, an ultrasonic-based method for the determination of the elastic constants of the Inconel 625 (IN625) material as manufactured via the laser powder-bed fusion process (L-PBF) is presented. Several specimens are fabricated with various process parameters such as laser power, scan speed, and hatch spacing, and nondestructively tested. The material elastic constants are then determined by measuring the ultrasonic wave velocities within the specimen. The results are verified qualitatively with the published results and destructive tensile tests. The obtained results showed a good correlation indicating the effectiveness of the proposed method for the determination of elastic constants of additively manufactured IN625 material.
26 citations
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TL;DR: The application of laser‐induced ultrasonic Lamb waves for the characterization of fiber‐reinforced plastic plates is demonstrated, providing effective parameters for a homogeneous, orthotropic material model.
17 citations
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Abstract: Structural health monitoring is recognized as a viable solution to increase aviation safety and decrease operating costs enabling a novel maintenance approach based on the actual condition of the airframe, mitigating operating costs induced by scheduled inspections. However, the net benefit is hardly demonstrated, and it is still unclear how the implementation of such an autonomic system can affect performance at aircraft level. To close this gap, this paper presents a systematic analysis where the impact of cost and weight of integrating permanently attached sensors—used for diagnostics- affect the main performance of the aircraft. Through a multidisciplinary aircraft analysis framework, the increment of aircraft operating empty weight is compared with the possible benefits in terms of direct operating costs to identify a breakeven point. Furthermore, the analysis allows to establish a design guideline for structural health monitoring systems returning a safer aircraft without any economic penalties. The results show that the operating costs are lower than those of the reference aircraft up to 4% increase in maximum take-off weight. Paper findings suggest to considering a condition monitoring strategy from the conceptual design stage, since it could maximize the impact of such innovative technology. However, it involves in a design of a brand-new aircraft instead of a modification of an existing one.
12 citations
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TL;DR: In this article, the elastic modulus inverted values were well agreed with experimental measurements with the controlled error percentage of 0.02-1.35% and individual layer modulus was calculated from the inversed averaged modulus and fitted with parabolic equation.
Abstract: Additive manufacturing (AM) or Three dimensional (3D) printing has become a promising manufacturing technique in architecture, aerospace, biomedical and automotive industries. However, additively manufactured parts need to demonstrate their stable mechanical properties like elastic modulus and strength. In this study, four various thickness of 3D printing samples were prepared to measure the elastic modulus by tensile testing and laser ultrasound technique (LUT). Besides, an inversion technique is followed to extract the elastic modulus from the 3D printed parts through LUT measured dispersion curve. Results indicate that significant differences in Young's modulus were observed between the various thickness of the tensile specimens. All the elastic modulus inverted values were well agreed with experimental measurements with the controlled error percentage of 0.02–1.35%. Further, individual layer modulus was calculated from the inversed averaged modulus and fitted with parabolic equation. Form the obtained outcomes, to print a sample with 40-layers, the first (top) layer modulus was 3254 MPa while bottom layer shows 4706 MPa which indicates a difference of 45% with inhomogeneous across the printed layers. While printing a new layer, the ultraviolet (UV) light can be exposed to previously printed layers and this more irradiation of UV light could stimulate to additional polymerization of remaining unreacted monomers and increased the modulus in the bottom layer.
10 citations