Artur Szewieczek, Christian Willberg, Daniel Schmidt and Michael Sinapius
A design of sensor networks for structural health monitoring (SHM) with guided waves poses a hard challenge. Therefore different approaches are possible. A known one is the usage…
Abstract
Purpose
A design of sensor networks for structural health monitoring (SHM) with guided waves poses a hard challenge. Therefore different approaches are possible. A known one is the usage of probability of detection (POD) criteria. Here, areas of potential impact sensitivity are calculated for every sensor which leads to a POD. The number of sensors is increased until a demanded POD is reached. However, these calculations are usually based on finite element methods and underlie different assumptions and approximations which can cause different inaccuracies. These limitations are avoided by using an experimental data basis for virtual sensors in this paper. The paper aims to discuss these issues.
Design/methodology/approach
An air-coupled ultrasound scanning technique is used for guided wave investigations. Recorded displacements of a structure surface are used as stimulation of virtual sensors which can be designed by software and positioned within available data field. For the calculation of sensor signals an isogeometric finite element model is used. The virtually bonded layer of the virtual piezoceramic sensor interpolates with non-uniform rational B-Splines (NURBS) the measured nodal data for each time step. This interpolation corresponds to a displacement boundary condition and is used to calculate the electrical potential at the free surface of the sensor.
Findings
Experimental data based on air-coupled ultrasound scanning technique can be used for elimination of disadvantages in numerical simulations by developing sensor networks for SHM. In combination with a transfer matrix method (TM) a three-dimensional displacement of specimen surface for complex composites can be calculated. To obtain the sensor signal a surface-bonded sensor is modeled by an isogeometric finite element approach. A good accordance is found between calculated virtual sensor signal and its experimental verification.
Research limitations/implications
Some deviations between calculated signal and its experimental verification are mainly justified by different spectral transfer functions between wave field scanning technique and signal recording of applied sensors. Furthermore, sensor influence on wave propagation is neglected in the presented method.
Originality/value
In this paper, the principle of virtual sensors is applied on anisotropic multilayered lamina by using isogeometric finite elements for piezoelectric sensors. This enables any sensor dimension, layout and position on complex composites. Furthermore a bonding layer between specimen and sensor is considered. The method allows a detailed analysis of sensor behavior on a specimen surface and the design and optimization of entire sensor networks for SHM.
Details
Keywords
Fábio Ribeiro Soares da Cunha, Tobias Wille, Richard Degenhardt, Michael Sinapius, Francisco Célio de Araújo and Rolf Zimmermann
– The purpose of this paper is to present the probabilistic approach to a new robustness-based design strategy for thin-walled composite structures in post-buckling.
Abstract
Purpose
The purpose of this paper is to present the probabilistic approach to a new robustness-based design strategy for thin-walled composite structures in post-buckling.
Design/methodology/approach
Because inherent uncertainties in geometry, material properties, ply orientation and thickness affect the structural performance and robustness, these variations are taken into account.
Findings
The methodology is demonstrated for the sake of simplicity with an unstiffened composite plate under compressive loading, and the probabilistic and deterministic results are compared. In this context, the structural energy and uncertainties are employed to investigate the robustness and reliability of thin-walled composite structures in post-buckling.
Practical implications
As practical implication, the methodology can be extended to stiffened shells, widely used in aerospace design with the aim to satisfy weight, strength and robustness requirements. Moreover, a new argument is strengthened to accept the collapse close to ultimate load once robustness is ensured with a required reliability.
Originality/value
This innovative strategy embedded in a probabilistic framework might lead to a different design selection when compared to a deterministic approach, or an approach that only accounts for the ultimate load. Moreover, robustness measures are redefined in the context of a probabilistic design.
Details
Keywords
Fábio Ribeiro Soares da Cunha, Tobias Wille, Richard Degenhardt, Michael Sinapius, Francisco Célio de Araújo and Rolf Zimmermann
This paper aims to present a new robustness-based design strategy for thin-walled composite structures under compressive loading, which combines strength requirements in terms of…
Abstract
Purpose
This paper aims to present a new robustness-based design strategy for thin-walled composite structures under compressive loading, which combines strength requirements in terms of the limit and ultimate load with robustness requirements evaluated from the structural energy until collapse.
Design/methodology/approach
In order to assess the structural energy, the area under the load-shortening curve between several characteristic points such as local buckling, global buckling, onset of degradation and collapse load is calculated. In this context, a geometrically nonlinear finite element analysis is carried out, in which the ply properties are selectively degraded by progressive failure.
Findings
The advantage of the proposed methodology is observed by analyzing unstiffened composite plates under compressive loading, wherein the lightest plate that satisfies both strength and robustness requirements can be attained.
Practical implications
As a practical implication, this methodology gives a new argument to accept the collapse load close to the ultimate load once robustness is ensured.
Originality value
The structural energy is employed to investigate the robustness of thin-walled composite structures in postbuckling, and new energy-based robustness measures are proposed. In the design of composite structures, this innovative strategy might lead to a more robust design when compared to an approach that only accounts for the ultimate load.