The validity of material properties obtained from uniaxial tension tests using different specimen types and measurement techniques is investigated in this paper. Four different specimen geometries were tested, including round axisymmetric and rectangular flat samples of different sizes. This gave a significant variation in both size and shape of the specimens. The specimens were strained in tension to fracture, and different measurement techniques were applied to measure the deformation of the specimens during loading. This involved an extensometer, a laser micrometre, digital image correlation (DIC) and edge tracing. Cauchy (true) stress versus logarithmic strain curves were obtained from the experimental data, and little spread was seen between the different test series. The data were further used to calibrate a work-hardening relation for the material, and it was found that the fitted curves differed mainly for strains beyond diffuse necking.

Pull-out mechanisms for different common steel fibers were investigated using adapted pull-out tests performed in-situ in an x-ray micro tomograph (µXRT). High-resolution volume images from the µXRT scans enable clear visualization of aggregates, pores, the fiber and the fiber-matrix interface. Furthermore, the natural density speckle pattern from aggregate distribution and pores was found suitable for Digital Volume Correlation (DVC) analysis. From the DVC results it was possible to visualize and quantify the strain distribution in the matrix around the fiber at the different load levels up to final failure, being marked by either pull-out or fiber rupture. This study demonstrates that strain measurements within the concrete matrix can be obtained successfully using µXRT imaging and DVC analysis, which leads to an increased understanding of the interaction mechanisms in fibre reinforced concrete under mechanical loading.

Analysis of failure mechanisms under high strain rate loading in engineering materials is a key point for the design of structures submitted to accidental overloads. We are here interested in the crack arrest capability under impact loading of polymers used as structural and/or protection materials. In the present work, crack arrest capability is defined by how an engineering structure which is initially weakened by a pre-crack behaves when dynamically reloaded. The Kalthoff and Winkler (KW) impact test, consisting in impacting the edge of a double notched plate, is retained for that purpose. An experimental investigation of the dynamic crack arrest capability of shock-resistant PMMA under high strain rate loading is presented, evidencing the brittle feature of the material failure. A high-speed camera is used to record the chronology of the failure mechanisms. It is notably shown that the higher the impact velocity (in the range 50-100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen.

The dynamic response and spall characteristics of a double-layer TC4 titanium alloy thin target under intense impulse loading was investigated experimentally using electric gun technique. A velocity measuring instrument, known as VISAR (velocity interferometer system for any reflector), measured the free surface velocity of targets. Typical characteristic parameters of the velocity were calculated by the obtained data. The deformation/failure modes of the samples were analyzed. And based on stress wave propagation theory, the spall thickness was derived. Furthermore, it was found that the oscillation period of the free surface velocity can be used to estimate the location of spalling damage, but cannot directly reflect the full spallation of the target.

A biaxial compression Hopkinson bar set-up bas been designed. It consists in a projectile, an input bar and two co-axial output bars. After the projectile impact on the input bar, the internal output bar measures the axial loading of the cross sample whereas the external output bar measures its transversal loading via a mechanism with sliding surfaces. Gauges glued on the bars enable stain measurements which lead to the forces and to the displacements on the interfaces between the bars and the mounting. The displacement field of the sample is obtained by high-speed imaging and by digital image correlation. Experiments show that the set-up works despites two disadvantages. Firstly, the transversal force in the sample is over-estimated because of the friction in the mechanism. Moreover, comparisons between the displacements on the bars interfaces and the sample displacement field display that the clearance have an influence on the sample loading.

Considering the Mooney–Rivlin hyperelastic model, a semi-analytical approach is introduced to analyze the rigid–flexible contact behaviors of an inflated membrane balloon between two plates with various interface conditions. This approach is based on the differential formulation and the coupling property of equilibrium equations are well-solved. In order to verify the reliability of the proposed theoretical model, an experimental test is designed, by which some important contact characteristics and patterns (no-slip condition) are obtained. Two special phenomena are observed for the meridian stretch ratio with different friction coefficients. One is that the intersection points of all curves fall in a small interval and the intersection of any two curves represents the same changing rate of the horizontal ordinate, resulting in the maximum difference. The other is the dividing point, where the stretch ratio decreases on the left of it and increases on the right due to the introduction of friction. These results provide solid guidance and support for our understanding of the rigid-flexible contact behaviors of an inflated membrane balloon.

The main aim of this paper was to computationally simulate the cardiac ischemia employing Finite Element Method (FEM) and detect its presence and localization using data mining approach. A simplified heart-torso model was created based on computed tomography (CT) images, with performed segmentation of the heart (17 zones). Ischemic and non-ischemic cardiac beats were simulated in different zones with aim to create a virtual database which was used for data mining. Using the virtual database, we trained several classifiers and tested them for the purpose of ischemic beat detection based on the body surface potentials map (BSPM). If the ECG is classified as ischemic by the first stage classifier, potentials were processed by the second stage data mining model, which predicted the location of the ischemic area. The use of the second stage classifier, which located the ischemia in one of the heart’s segments created in the FEM model, goes beyond the current state of the art. Thus, the proposed approach is improved solution which can instantly allow clinicians to implement an adequate treatment strategy in future.

Realistic characterization of fatigue loading resistance is a paramount for an economical and reliable structural design of reinforced concrete (RC) and prestressed concrete (PC) structures. The need for innovative experimental methods for the characterization of fatigue behavior is driven by the current aims to construct wind turbine towers that must resist up to N=10⁷ loading cycles corresponding to 25 years of service life. Considering the number of possible configurations with regard to structural geometries, cross-sectional layout of reinforcement and loading scenarios, experimental data are required that capture the key mechanisms driving the fatigue damage between the reinforcement and concrete matrix. Experimental investigations of bond behavior under fatigue loading have been reported in the literature in the 90’s of last century. Since then, no systematic investigation of bond fatigue behavior has been published. As a consequence, no assessment rules are available for the bond fatigue, only separate assessment rules for concrete and steel. The present paper will report on the ongoing research of bond fatigue behavior using the beam-end test setup. The test campaign includes the push-in loading with the goal to provide data characterizing the compressive behavior of reinforced cross sections in wind turbine towers.

Combined non-destructive in situ techniques – namely sonic tests and ambient vibration measurements – are applied on two Nepali Pagoda temples damaged by the 2015 Gorkha earthquake, providing the dynamic elastic modulus of masonry and the buildings’ frequencies.

The IET was used to determine the macroscopic elasticity constants of the multiphase coating. In order to determine the macroscopic elasticity constants of the film firstly, a critical assessment of Young’s modulus determination was done by comparing all the models proposed in the literature. The best model was identified and a study was performed to identify and quantify the most influent factors on the global uncertainty. Secondly, an enhanced formulation to determine the shear modulus of coating by IET was developed. The methodology was applied on a tungsten thin film deposited by DC magnetron sputtering.