Cracking is a common type of failure in machines and structures. Cracks must be detected at an early stage before catastrophic failure. In structural health monitoring, changes in the vibration characteristics of the structure can be utilized in damage detection. A fatigue crack with alternating contact and non-contact phases results in a non-linear behaviour. This type of damage was simulated with a finite element model of a simply supported beam. The structure was monitored with a sensor array measuring transverse accelerations under random excitation. The objective was to determine the smallest crack length that can be detected. The effect of the sensor locations was also studied. Damage detection was performed using the generalized likelihood ratio test (GLRT) in time domain followed by principal component analysis (PCA). Extreme value statistics (EVS) were used for novelty detection. It was found that a crack in the bottom of the midspan could be detected once the crack length exceeded 10% of the beam height. The crack was correctly localized using the monitoring data.

A statistical simulation model is presented to compute the effective in-plane compliance matrices of the honeycomb materials. The present model is explained in three stages: the micromechanical model, simulation experiments under external loading and boundary conditions, and the analysis of the experiment results. In the micromechanical model, mean values of the geometrical and mechanical parameters and variations related to cell wall height and thickness are used in order to mimic the actual materials in the virtual environment. Simulation experiments are performed on these replicated materials under the assumption of linear elasticity. The effect of solution artefacts near the boundary domain is controlled by defining a measurement domain where the strain and stress fields are assumed to be constant. The simulation results for this domain are processed with transformation and the least squares minimization to obtain the effective in-plane elastic parameters. In this context, two case studies are conducted. The first case study aims at understanding the influences of the cell geometry and aforementioned variations on the linear elastic material behavior. Meanwhile, the scope of the second case study is to validate the proposed model by comparing the simulation results with the measurements conducted on Nomex ® honeycomb materials by the authors.

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A material model is presented that includes the following deformation mechanisms: the instantaneous response of ice due to distortion of crystal lattices, creep, the formation of microcrack nuclei due to creep, the formation of microcracks, and deformation due to microcracks. The new material model has a strict foundation on deformation mechanisms. This constitutive equation was applied to sea ice for engineering applications through implementation in the Abaqus explicit code by writing a VUMAT subroutine. The computed results show that the model correctly predicts the uniaxial tensile and the uniaxial compressive strengths of ice. The computed compressive strength versus strain-rate relation takes an almost linear relation when expressed in the log–log coordinates, which fits well with the data obtained from the literature. The material model shows the Hall–Petch type of strength dependency on the grain size.