. Ruan, T.; Poursaee, A. 2016-04-01 Cement-based materials are widely used in infrastructure facilities. However, often the degradation of structures leads to the failures earlier than designed service life. Thus, non-destructive testing techniques are urgently needed to evaluate the health information of the structures.
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In this paper, the implementation of Electrical Resistance Tomography (ERT) was investigated. This low cost, radiation free and easy to perform modality is based on measuring the electrical properties of the material under test and using that to evaluate the existence of defects in that material. It uses a set of boundary potentials and injected current to reconstruct the conductivity distribution.
An automatic measurement system was developed and surface damages as well as subsurface damages on mortar specimens were investigated. The reconstructed images were capable to show the presence and the location of the damages. Al-Ajmi 2007-06-01 Full Text Available This study is intended to balance the rights of free navigation in all of its forms whether in the high seas or in the territorial waters of other States by resorting to the right of innocent passage and right of transit passage, which is enjoyable by all States and the obligation to protect the environment from any damaging materials as imposed upon all States at the same time, when such damaging materials are shipped from one State to another via seas or oceans. According to this study, which presented many evidence from international law and regional and even national practice, the obligation to protect the environment supersedes the right of free navigation, therefore restricting the right to ship or transport materials that could cause damage to the environment. Soto, Leopoldo; Pavez, Cristian; Inestrosa-Izurieta, Maria Jose; Moreno, Jose; Davis, Sergio; Bora, Biswajit; Avaria, Gonzalo; Jain, Jalaj; Altamirano, Luis; Panizo, Miguel; Gonzalez, Raquel; Rivera, Antonio 2016-10-01 Future thermonuclear reactors, both magnetic and inertial confinement approaches, need materials capable of withstanding the extreme radiation and heat loads expected from high repetition rate plasma. A damage factor (F = qτ1/2) in the order of 104 (W/cm2) s1/2 is expected. The axial plasma dynamics after the pinch in a tabletop plasma focus of hundred joules, PF-400J, was characterized by means of pulsed optical refractive diagnostics.
The energy, interaction time and power flux of the plasma burst interacting with targets was obtained. Results show a high dependence of the damage factor with the distance from the anode top where the sample is located.
A tunable damage factor in the range 10- 105(W/cm2) s1/2 can be obtained. At present the PF-400J operating at 0.077 Hz is being used to study the effects of fusion-relevant pulses on material target, including nanostructured materials. A new tabletop device to be operated up to 1Hz including tunable damage factor has been designed and is being constructed, thus thousand cumulative shots on materials could be obtained in few minutes. The scaling of the damage factor for plasma foci operating at different energies is discussed. Supported by CONICYT: PIA ACT-1115, PAI 79130026. Borkowski, Luke Advanced aerospace materials, including fiber reinforced polymer and ceramic matrix composites, are increasingly being used in critical and demanding applications, challenging the current damage prediction, detection, and quantification methodologies. Multiscale computational models offer key advantages over traditional analysis techniques and can provide the necessary capabilities for the development of a comprehensive virtual structural health monitoring (SHM) framework.
Virtual SHM has the potential to drastically improve the design and analysis of aerospace components through coupling the complementary capabilities of models able to predict the initiation and propagation of damage under a wide range of loading and environmental scenarios, simulate interrogation methods for damage detection and quantification, and assess the health of a structure. A major component of the virtual SHM framework involves having micromechanics-based multiscale composite models that can provide the elastic, inelastic, and damage behavior of composite material systems under mechanical and thermal loading conditions and in the presence of microstructural complexity and variability.
Quantification of the role geometric and architectural variability in the composite microstructure plays in the local and global composite behavior is essential to the development of appropriate scale-dependent unit cells and boundary conditions for the multiscale model. Once the composite behavior is predicted and variability effects assessed, wave-based SHM simulation models serve to provide knowledge on the probability of detection and characterization accuracy of damage present in the composite. The research presented in this dissertation provides the foundation for a comprehensive SHM framework for advanced aerospace materials. The developed models enhance the prediction of damage formation as a result of ceramic matrix composite processing, improve the understanding of the effects of architectural and. J.
Kramberger 2016-01-01 Full Text Available The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications.
This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle.
Degradation of the elastic stifness was modeled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.
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LI Sheng-yi; WANG Zhuo; WU Yu-lie 2007-01-01 A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials. Postulated condition of the model was that subsurface damage depth and peak-to-valley surface roughness are equal to depth of radial and lateral cracks in brittle surface induced by small-radius (radius≤200 μm) spherical indenter, respectively. And contribution of elastic stress field to the radial cracks propagation was also considered in the loading cycle. Subsurface damage depth of ground BK7 glasses was measured by magnetorheological finishing spot technique to validate theoretical ratio of subsurface damage to surface roughness. The results show that the ratio is directly proportional to load of abrasive grains and hardness of optical materials, while inversely proportional to granularity of abrasive grains and fracture toughness of optical materials. Moreover, the influence of the load and fracture toughness on the ratio is more significant than the granularity and hardness, respectively.
The measured ratios of 80 grit and 120 grit fixed abrasive grinding of BK7 glasses are 5.8 and 5.4, respectively. Oungoulian, Sevan R; Durney, Krista M; Jones, Brian K; Ahmad, Christopher S; Hung, Clark T; Ateshian, Gerard A 2015-07-16 The objective of this study was to measure the wear response of immature bovine articular cartilage tested against glass or alloys used in hemiarthroplasties. Two cobalt chromium alloys and a stainless steel alloy were selected for these investigations. The surface roughness of one of the cobalt chromium alloys was also varied within the range considered acceptable by regulatory agencies. Cartilage disks were tested in a configuration that promoted loss of interstitial fluid pressurization to accelerate conditions believed to occur in hemiarthroplasties. Results showed that considerably more damage occurred in cartilage samples tested against stainless steel (10 nm roughness) and low carbon cobalt chromium alloy (27 nm roughness) compared to glass (10 nm) and smoother low or high carbon cobalt chromium (10 nm).
The two materials producing the greatest damage also exhibited higher equilibrium friction coefficients. Cartilage damage occurred primarily in the form of delamination at the interface between the superficial tangential zone and the transitional middle zone, with much less evidence of abrasive wear at the articular surface. These results suggest that cartilage damage from frictional loading occurs as a result of subsurface fatigue failure leading to the delamination. Surface chemistry and surface roughness of implant materials can have a significant influence on tissue damage, even when using materials and roughness values that satisfy regulatory requirements. 2016-07-01 Frictional sliding and crack growth are two main dissipation processes in quasi brittle materials. The frictional sliding along closed cracks is the origin of macroscopic plastic deformation while the crack growth induces a material damage. The main difficulty of modeling is to consider the inherent coupling between these two processes.
Various models and associated numerical algorithms have been proposed. But there are so far no analytical solutions even for simple loading paths for the validation of such algorithms. In this paper, we first present a micro-mechanical model taking into account the damage-friction coupling for a large class of quasi brittle materials. The model is formulated by combining a linear homogenization procedure with the Mori-Tanaka scheme and the irreversible thermodynamics framework. As an original contribution, a series of analytical solutions of stress-strain relations are developed for various loading paths.
Based on the micro-mechanical model, two numerical integration algorithms are exploited. The first one involves a coupled friction/ damage correction scheme, which is consistent with the coupling nature of the constitutive model. The second one contains a friction/ damage decoupling scheme with two consecutive steps: the friction correction followed by the damage correction. With the analytical solutions as reference results, the two algorithms are assessed through a series of numerical tests. It is found that the decoupling correction scheme is efficient to guarantee a systematic numerical convergence. Bor, Teunis Cornelis; Warnet, Laurent; Akkerman, Remko; de Boer, Andries 2010-01-01 Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment.
The composite material. Bor, T.C.; Warnet, L.; Akkerman, R.; Boer, de A. 2010-01-01 Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment. The composite material co. Alexandre Chmel 2014-10-01 Full Text Available A set of heterogeneous and homogeneous materials differing in their brittle and ductile characteristics (granite, marble, silica ceramics, silicon carbide, organic glass were subjected to impact damaging by a falling weight. Multiple chemical bond ruptures produced by elastic waves propagating from a damaged zone were accompanied by the photon emission generated throughout the sample (tribo- or fractoluminescence, FL.
The statistical analysis of the FL time series detected with high resolution (10 ns showed that the energy release distributions in brittle solids follow the power law typical for the correlated nucleation of primary defects. At the same time, the formation of damaged sites in ductile materials (marble and organic glass was found to be fully random. 2016-11-01 component 1A:1B rigid high density polyurethane.The Program Manager was Jeb S. Tingle, ERDC-GSL.
This work was performed by the Airfields and Pavements Branch (GMA) of the Engineering Systems.airfield damage repair AFCEC U.S. Air Force Civil Engineer Center APB Airfields and Pavements Branch ASTM American Society for Testing and Materials. Pensky, H.M.H. 2000-07-01 For realistic numerical simulations of the stress-strain behaviour of structures, models are necessary which describe elastic-inelastic and scattering material behaviour. The developed models simulate elastic, viscoplastic and anisotropic damage material phenomena. An approach is proposed for covering stochastic material beahviour by correspondingly distributed parameters of the deterministic material model.
Numerical simulations of biaxial material tests and structural tests demonstrate the range of applicability. (orig.) German Die realitaetsnahe numerische Simulation des Spannungs-Verformungsverhaltens von Bauteilen erfordert Modelle zur Beschreibung inelastischen und streuenden Materialverhaltens. Die hier entwickelten Modelle beschreiben elastische, viskoplastische und anisotrope Schaedigungsphaenomene des Materialverhaltens. Desweiteren wird ein Konzept vorgestellt, mit dem streuendes Materialverhalten mit streuenden Materialparametersaetzen deterministischer Stoffmodelle beschreibbar ist.
Numerische Simulationen von Werkstoff- und Bauteilversuchen veranschaulichen den Anwendungsbereich der Modelle. (orig.).
Chen Yixue; Wu Yican 2005-01-01 Radiation damage to structural material of fusion facilities is of high concern for safety. The superconducting tokamak EAST will conduct D-D plasma experiments with the neutron production of 1015 neutrons per second. To evaluate the material radiation damage a programme system has been devised with the Monte Carlo transport code MCNP-4C, the inventory code FISPACT99, a specific interface, and the fusion evaluated nuclear data library FENDL-2.The key nuclear responses, i.e. Fast neutron flux, displacement per atom, and the helium and hydrogen production, are calculated for the structural material SS-316L of the first wall, and the vacuum vessel, using this programme. The results demonstrate that the radiation damage to the structural material is so little that it will not lead to any significant change of material properties according to the reference design. This indicates that there is a large potential space for EAST to test advanced operation regime from the viewpoint of structural material safety.
Moore, Merriam M. This guidebook is intended for use by teachers of Spanish (FLES through college level) and by teachers in Spanish bilingual programs. It lists all of the Spanish-speaking countries and 72 Spanish-language cultural themes, such as 'Actualidades' (Current Events), 'Carreras y espanol comercial' (Careers and Commercial Spanish), 'Deportes' (Sports),. Moore, Merriam M.
This guidebook is intended for use by teachers of Spanish (FLES through college level) and by teachers in Spanish bilingual programs. It lists all of the Spanish-speaking countries and 72 Spanish-language cultural themes, such as 'Actualidades' (Current Events), 'Carreras y espanol comercial' (Careers and Commercial Spanish), 'Deportes' (Sports),. Gartin, Stacy A.; And Others 1989-01-01 The theme is the National Academy of Sciences study of agricultural education at the secondary level. Reactors discuss educational change, leadership training, student organizations, supervised occupational experience programs, delivery systems, teacher education, and the future of vocational agriculture. (JOW).
Leske, Gary; And Others 1994-01-01 Theme articles focus on the relationship of experiential learning to school-to-work transition, science fair projects, leadership training, performance-based assessment, livestock judging, management instruction for farm women, and instructor preparation. (JOW).
祝荣玲 2008-01-01 1.1The Theme:A Novel without a Hero There is one clear,overarching theme in Vanity Fair:A Novel without a Hero,and Thackeray telegraphs it in his title and subtitle.In the pages of Vanity Fair,all is vanity and all are vain.Some are more vain-more obsessed with self and with the ephemeral treasures of social position and money-than others,. Demos, Stavros G.; Feit, Michael D.; Duchateau, Guillaume 2014-10-01 A model simulating transient optical properties during laser damage in the bulk of KDP/DKDP crystals is presented. The model was developed and tested using as a benchmark its ability to reproduce the well-documented damage initiation behaviors but most importantly, the salient behavior of the wavelength dependence of the damage threshold. The model involves two phases. During phase I, the model assumes a moderate localized initial absorption that is strongly enhanced during the laser pulse via excited state absorption and thermally driven generation of additional point defects in the surrounding material. The model suggests that during a fraction of the pulse duration, the host material around the defect cluster is transformed into a strong absorber that leads to significant increase of the local temperature. During phase II, the model suggests that the excitation pathway consists mainly of one photon absorption events within a quasicontinuum of short-lived vibronic defect states spanning the band gap that was generated after the initial localized heating of the material due to thermal quenching of the excited state lifetimes.
The width of the transition (steps) between different number of photons is governed by the instantaneous temperature, which was estimated using the experimental data. The model also suggests that the critical physical parameter prior to initiation of breakdown is the conduction band electron density. This model, employing very few free parameters, for the first time is able to quantitatively reproduce the wavelength dependence of the damage initiation threshold, and thus provides important insight into the physical processes involved.