The time-averaged electronic speckle pattern interferometry (ESPI) is employed to measure the frequencies and mode shapes of thin, cantilevered plates with root-slit. The first 12 order linear resonance frequency and mode shape of an intact cantilevered plate is determined by using FEM calculation. The dynamic response of the intact specimen forced by a PZT actuator is measured and its super-harmonic resonance of forced response is investigated experimentally. The results show that the principal mode shape of super-harmonic vibration is similar to its natural modal. In contrast to linear forcing vibration, the threshold of force for super-harmonic resonance is much higher than that of the former. In addition, linear free response of four cantilevered root-slit plates with variation length of slit are analyzed by applying the FEM calculation, and their responses of forcing vibration were measured by using the ESPI method. The validity and accuracy of the numerical prediction are confirmed through experimental studies. The present work shows that the ESPI technique can provide whole-field and real-time measurement for vibration analysis and can also be employed for validation of the FEM calculation.

Six prototype violins made from composite materials are made and investigated using experimental modal analysis with the roving hammer method. The average FRF’s obtained show an influence of the materials on the vibrational response up to 2200 Hz. The A0 breathing mode and B1- mode are identified and are found to be significantly lower than in classical wooden violins. Additional measurements with a Laser Doppler Vibrometer and shaker found the same modes with a small difference in frequency (3-8Hz).

The Pulsed Ultrasonic Polar Scan (P-UPS) is a powerful technique for characterizing anisotropic materials like fiber reinforced plastics. A time-domain analysis of the ultrasonic signals yields amplitude and time-of-flight polar diagrams that provide a fingerprint of the local stiffness properties. Though, this simple analysis ignores a lot of information contained in the ultrasonic signals. In this study, we propose to use the P-UPS technique in combination with the spectroscopic analysis of broadband pulses, to obtain plane wave transmission spectra for all in-plane polar angles. This allows us to combine on one hand the strengths of the P-UPS technique, that does not require a priori knowledge about the sample anisotropy, and on the other hand the frequency-domain analysis that utilizes information contained in the broadband pulses.

Propagation of shock waves in partially- or fully-confined environments is a complex phenomenon due to the possibility of multiple reflections, diffractions and superposition of waves. In a military context, the study of such phenomena is of extreme relevance to the evaluation of protection systems, such as survival containers, for personnel and equipment. True scale testing of such structures is costly and time consuming but small-scale models in combination with the Hopkinson-Cranz scaling laws are a viable alternative. This paper combines the use of a small-scale model of a compound survival container with finite element analysis (with LS-DYNA) to develop and validate a numerical model of the blast wave propagation. The first part of the study details the experimental set-up, consisting of a small-scale model of a survival container, which is loaded by the detonation of a scaled explosive charge. The pressure-time histories are recorded in several locations of the model. The second part of the study presents the numerical results and a comparison with the experimental data.

Different non-destructive testing techniques have been evaluated for detecting and assessing damage in carbon fiber reinforced plastics: (i) ultrasonic C-scan, (ii) local defect resonance of front/back surface and (iii) lock-in infrared thermography in reflection. Both artificial defects (flat bottom holes and inserts) and impact damage (barely visible impact damage) have been considered. The ultrasonic C-scans in reflection shows good performance in detecting the defects and in assessing actual defect parameters (e.g. size and depth), but it requires long scanning procedures and water coupling. The local defect resonance technique shows acceptable defect detectability, but has difficulty in extracting actual defect parameters without a priori knowledge. The thermographic inspection is by far the fastest technique, and shows good detectability of shallow defects (depth < 2 mm). Lateral sizing of shallow damage is also possible. The inspection of deeper defects (depth > 3-4 mm) in reflection is problematic and requires advanced post-processing approaches in order to improve the defect contrast to detectable limits.

Discrete Element modelling of concrete requires the precise calibration of model parameters that is a long lasting and computationally expensive task in case of complex models. Present study introduces a method for estimating a model parameter (normal strength of parallel bonds) for concretes with different particle size distribution and aggregate type. The parameter estimation leads to an optimization problem based on physical measurement data. In the present paper, a model and its parameters are proposed to estimate normal strength of parallel bonds based on the density and compressive strength of concrete.

A phase-shifting shearing interference microscope (PSSIM) is introduced in this paper. It is constructed by placing a Savart shear prism between the objective and sample of a polarizing microscope with a rotatable analyzer as the phase-shifter, and it is capable of determining contour height variation and deformation strain using the principle of shearing interferometry. This paper not only interprets the measurement theory but also presents an experimental setup of the PSSIM. Moreover, this paper exhibits the results from the uses of the setup; the results demonstrate the validity and applicability of the PSSIM.