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Analysis of peel and shear strains in cracked lap shear specimens subjected to fatigue loading using digital image correlation
Get PDFAdhesive bonding presents many advantages, such as efficient manufacturing and improved structural performance [1]. However, in structures subjected to fatigue, cracks might initiate and propagate in joints, leading to in-service failure [2]. Most adhesively bonded joints are subjected to combination of peel and shear loads, so mixed I+II mode loading conditions are present [3]. In this work, Cracked Lap Shear specimens, which feature mixed I+II mode loading conditions, were tested under fatigue loading. During tests, crack growth was monitored using Visual Testing and Digital Image Correlation. With Digital Image Correlation, opening and sliding displacements in the bondline were extracted from the substrates’ displacement fields and compared against a Finite Element Model, revealing a highly strained process zone ahead of the crack tip. Results highlight the usefulness of DIC in capturing the deformation behaviour of adhesive joints under mixed mode loading conditions
Effect of the long-term storage methods on the stability of cartilage biomechanical parameters
Get PDFLong-term stability of the tissue product in terms of mechanical parameters is a key factor for its expiration date. For the investigation of storage effects on the cartilage tissues the experimental mechanical loading test combined with XCT scanning for the irregular shape inspection was performed. The samples were preserved according to three different protocols using the deep-freezing and two types of saline solution preservation. The stability of the biomechanical parameters was tested within annual intervals. All samples were subjected to uni-axial compression loading using the in-house developed compact table top loading device in displacement-driven mode. Based on the measurements, the results are represented in the form of stress-strain curves and quantified as elastic modulus and ultimate compression stress. It can be concluded that no significant difference was found in neither the mechanical properties of the samples nor in the effects of each preservational method
Multiphysical Simulation of Impulse Current Arcs in Spark Gaps for Industrial Applications
Get PDFDigital prototyping enables cost-effective production and modular optimization of surge protection devices (SPD). Numerical model of SPD prototypes involves complex multiphysics phenomena. However, the processes related to impulse current arcs in spark gaps are not well understood so far. Limited knowledge exists regarding hydrodynamic effects, plasma states, and radiation properties. This work studies an impulse current 8/20 µs with an amplitude of about 5 kA in experiment and simulation
The Effect of Gas Type on Flow Characteristics in a Circuit Breaker under Cold Flow Scenario
No full textThis paper presents first stage of supersonic flow modelling in gas circuit breakers without an arc. Flow characterisation focused on shock and flow separation phenomenon. Velocity deceleration caused by shock will play a significant role in determining arc cooling performance and will impact thermal interruption capability. Gas properties such as specific heat ratio, density, and viscosity influenced the flow characteristics including shock location, strength and the flow separation process
The effect of ambient temperature on the delay time of perimeter protection
Get PDFPerimeter security defines the private space from the public space and also serves as the first barrier between the intruder and the protected interest. Delay time is one of the input parameters used in a quantitative approach to the design of a physical protection system. The objective of the physical protection system is to delay the intruder long enough for the law enforcement to arrive on the scene and apprehend the intruder. Perimeter protection is located in the exterior and is affected by various factors such as ambient temperature. In cold temperatures, the technical parameters deteriorate and the delay time for penetration into the protected object decreases. The paper points out that the delay time is longest at 0 °C and that the delay time decreases as the ambient temperature increases. A further perspective is mentioned on the adaptation of the tests and increasing the degree of subjectivity of the test results
Fake face detection based on a multi discriminator deep CNN architecture (MDD-CNN)
Get PDFDue to the robustness of the deep learning tools used to design these applications, fakes are becoming increasingly common as these applications become more widely available and accessible to the general public. These fakes are typically fake faces or even fake people, which are difficult to distinguish from real individuals. Therefore, we need more efficient applications for fraud detection. In this work, we propose a new multi-discriminator architecture to distinguish fake faces from real ones. The architecture consists of three deep networks (discriminators) competing with each other, each trained differently. The final decision is made by voting based on the decisions of the three discriminators. The core element of our architecture is the proposed new adversarial deep network discriminator (NDGAN), which is trained in three different ways, resulting in three distinct discriminators. Discriminator 1 undergoes adversarial training, discriminator 2 is trained using transfer learning, and the third discriminator undergoes supervised training with a standard CNN using examples and counterexamples. Training and testing were performed on 70 000 real faces from the Flickr-Face-HQ (FFHQ) dataset, while 70 000 fake faces were generated using Nvidia’s StyleGAN. The tests conducted on the three networks produced significant results, with accuracy ranging from 79 % to 98 % for fake faces, and from 80 % to 98 % for real faces. The reliability of the discriminators contributes significantly to the overall performance of the multi-discriminator system, achieving an accuracy of 96 % for fake faces and 98 % for real faces
Application of the Source-Jerk method using a neutron generator in a subcritical reactor
Get PDFThis paper describes the application of the Source-Jerk method using a neutron generator in the VR-1 reactor. The experiments were carried out on a shutdown reactor with subcriticality greater than -10 βeff. A D-D neutron generator located in the radial channel of the VR-1 reactor was used as an external neutron source for the Source-Jerk method. The obtained results were discussed and compared with a conventional Source-Jerk method used at the VR-1 reactor and with the values calculated by the Serpent 2 code. The presented experimental works and their results will allow to extend the methods of reactivity measurements on the VR-1 reactor. They will also help to optimise reactivity measurements on the new subcritical reactor VR-2, which is currently being commissioned at the Czech Technical University in Prague
Utilising Pareto efficiency and RSM to adjust binder content in clay stabilisation for Yttre Ringvägen, Malmö
Get PDFIn this paper, we present a new framework for improving soil strength using an advanced method of engineering statistics. The materials included clay till collected in Yttre Ringvägen, southern Sweden. Binders included quicklime, slag and ordinary Portland cement used as pure binders and blended mixtures. We first applied the Response Surface Methodology techniques aimed at binder blend optimisation: 1) Central Composite Design; 2) Box-Behnken Design; 3) Simplex Lattice Design. The Pareto charts were presented for modelling responses from tests with different binders and estimating their effects on soil strength. Finally, to examine the variables important for soil stabilisation, we also evaluated the effect of the amount of binder and the interaction between cement/lime/slag in different ratios: 30-50-20 %; 50-50-0 %; 100-0-0 % The paper highlights the major opportunities and challenges of engineering statistics as a cross-cutting research direction for the issues of civil engineering
From positional representation of numbers to positional representation of vectors
Get PDFTo represent real m-dimensional vectors, a positional vector system given by a non-singular matrix M ∈ ℤm×m and a digit set Ɗ ⊂ ℤm is used. If m = 1, the system coincides with the well known numeration system used to represent real numbers. We study some properties of the vector systems which are transformable from the case m = 1 to higher dimensions. We focus on an algorithm for parallel addition and on systems allowing an eventually periodic representation of vectors with rational coordinates
The experimental evaluation of tensile forces in stays of a cable-stayed footbridge
Get PDFThe topic of this paper is an experimental analysis of the dynamic behaviour of stays of an existing footbridge focusing on determination of the tensile forces in stays. The examined structure was the footbridge across the Vltava river in Lužec nad Vltavou. It is a cable-stayed footbridge, the horizontal load-bearing structure consists of UHPC components, which are prestressed by a pair of external cables. The horizontal load-bearing structure is suspended on a 39.85 m high A-shaped steel pylon by means of a system of 17 pairs of stays. As a part of the work the tensile forces in stays were determined using the vibration frequency method. The method is based on the knowledge of natural frequencies of the stays, which were investigated by the experimental analysis