The Experts below are selected from a list of 35118 Experts worldwide ranked by ideXlab platform
John F Watts - One of the best experts on this subject based on the ideXlab platform.
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role of corrosion in the Failure of adhesive joints
Reference Module in Materials Science and Materials Engineering#R##N#Shreir's Corrosion, 2010Co-Authors: John F WattsAbstract:Structural adhesive bonding of metal components is widespread in many areas of engineering, ranging from microelectronics assembly to aerospace applications. It is well known that exposure of such joints to water in liquid or vapor form can compromise the durability of such joints and bring about premature Failure. This chapter reviews the various Failure mechanisms responsible for Failure and the rationale of the need for surface specific methods of chemical analysis to identify the Failure Path (locus of Failure) exactly. Failure is often associated with corrosion of the metallic substrates, and the presence of cathodically generated alkali is shown to have a particularly deleterious effect of adhesive joint performance. A series of case histories are provided to illustrate investigations of the Failure modes experience by some common engineering substrates (aluminum alloy, low carbon steel, and zinc). Finally, the question of modeling Failure kinetics and potential routes to the improvement of bond durability are considered.
Sompote Youwai - One of the best experts on this subject based on the ideXlab platform.
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high internal pressure induced fracture patterns in rock masses surrounding caverns experimental study using physical model tests
Engineering Geology, 2015Co-Authors: Pornkasem Jongpradist, Jukkrawut Tunsakul, Warat Kongkitkul, Nattapol Fadsiri, Goran Arangelovski, Sompote YouwaiAbstract:Abstract This research has experimented with artificial rock specimens that contain a circular or oblong hole using a novel physical modeling approach to investigate the Failure behavior of rock masses surrounding a cavern with high internal pressure. The knowledge of fracture initiation and propagation in rock masses is crucial to the selection of underground storage construction sites and a stability evaluation method. Specifically, this research attempts to investigate the fracture initiation and propagation direction of the rock mass that encloses an underground gas/air storage cavern with high internal pressure under varying control conditions. The experiments are carried out with 200-time scaled-down artificial rock specimens under varying stress ratio (ki), overburden stress (σvi) and the joint's dip angle (α). The internal pressure applied to the hole is gradually increased until the fracture is initiated and propagates. Photogrammetric analysis is utilized to identify the rock mass response induced by increasing internal pressure and the occurrence of Failure Path. The experimental results indicate that the fracture initiation point and propagation direction of Failure Path are strongly influenced by the in-situ stress ratio, k. The findings also reveal that the site with an initial in-situ stress ratio greater than one is suitable for use as a high-internal-pressure underground cavern. In addition, in the presence of a nearby joint, the site with a smaller dip angle joint is more desirable. For the same in-situ stress ratio, an oblong-shaped cavern is more stable than a circular cavern (tunnel) of similar size, although both cavern configurations exhibit the similar Failure patterns.
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investigation of Failure behavior of continuous rock mass around cavern under high internal pressure
Tunnelling and Underground Space Technology, 2013Co-Authors: Jukkrawut Tunsakul, Pornkasem Jongpradist, Warat Kongkitkul, Anucha Wonglert, Sompote YouwaiAbstract:Abstract A series of physical and numerical model tests were performed to investigate the Failure behavior of a continuous rock mass surrounding a silo-shaped cavern under high internal pressure. This research aims to provide information on fracture initiation and propagation in the rock mass around an underground gas storage cavern occurring as a result of applying high internal pressure under different controlled conditions. By scaling down the prototype 200 times, synthetic rock specimens containing silo-shaped hole were confined to vertical pressures of 12.5 and 25 kPa, with a Ko of 0.5, 1 and 3 in the two horizontal directions. The pressure was gradually applied in the silo until fracture initiated and propagated. The photogrammetric analysis provides insights into the response of the rock mass during the application of internal pressure and assists in identifying the Failure Path that occurred. The resulting fracture patterns indicate that the lateral earth pressure coefficient at rest, Ko, has a strong influence on the position of crack initiation and the propagation direction of the Failure Path. Supplemental numerical analyses were carried out to evaluate the Failure mode, which cannot be addressed by the model tests. The numerical method, based on finite element method, considers stress analysis with localization and is developed to capture the formation of discrete fractures in a continuum. It is found that the method is able to accurately represent the factors that affect the fracture pattern and that a qualitative agreement between the experimental and numerical results can be established. A comparison between experimental and numerical results indicates that the fracturing process was caused by tensile cracking.
Da Qing Tian - One of the best experts on this subject based on the ideXlab platform.
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safety margin characterization for in service pressure vessels containing crack defects
Applied Mechanics and Materials, 2014Co-Authors: Si Jian Lin, Wei Long, Da Qing TianAbstract:It’s significant and necessary to assess the safety of the in-service pressure vessels containing crack defects, and there are so many methods that can do, for example, the finite element method and probabilistic fracture mechanics assessment method. However, knowing the safety of the pressure vessels containing crack defects is not enough. For the residual lifetime reason, we are eager to get the safety margin of the pressure vessels. That is how secure they are. Aiming at this problem, we put forward the concept of Failure Path based on the Failure Assessment Diagram (FAD) and fracture mechanics to help to characterize safety margin. Facts proved that this method was original and useful which can provide a new way in solving the residual lifetime assessment problem of the in-service pressure vessels containing crack defects.
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residual life prediction for in service pressure vessels containing crack defects
Applied Mechanics and Materials, 2014Co-Authors: Si Jian Lin, Wei Long, Da Qing TianAbstract:Residual life is tightly related to the period of examine and repair of pressure vessels. The accuracy of residual life prediction may have a great influence on the reliability and the cost of examine and repair of the in-service pressure vessels containing crack defects. Aimed at the problem of residual life prediction of pressure vessels containing crack defects, we put forward a new method on the basis of crack Failure Path and rate, which is based on the fracture mechanics and Failure assessment diagram (FAD). Though there may be a lot of researches to do, this algorithm is higher in efficiency and easy to calculate, compared to the other methods. This method is original and creative. It provides a new research approach to study the residual life prediction.
F L Matthews - One of the best experts on this subject based on the ideXlab platform.
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adhesively bonded repairs to fibre composite materials ii finite element modelling
Composites Part A-applied Science and Manufacturing, 1998Co-Authors: M N Charalambides, A J Kinloch, F L MatthewsAbstract:Abstract Part I described the static performance (i.e. the performance under a monotonic rate of loading) of carbon-fibre reinforced-plastic (CFRP) composites which had been repaired by adhesively bonding and co-curing, a second section of CFRP prepreg to the original parent material. The mechanical behaviour of these repair joints, as well as of the adhesive and CFRP forming the joint, were determined both in the unaged condition and after ageing. The hot/wet ageing of the repair joints and materials was simulated by immersing the joints and materials in water at 50°C. In Part II, the mechanical properties of the adhesive and the CFRP have been used in conjunction with a finite element analysis (FEA) to determine Failure criteria which would predict the experimentally observed Failure Paths and strength of the adhesively-bonded repair joints. Two material models were used for the adhesive: a linear elastic and linear elastic–plastic. Two models were also used for the composite. In the first model, the composite was assumed to be a homogeneous orthotropic material with smeared properties. In the second, it was modelled as a combination of individual plies of various orthotropic/anisotropic properties, depending upon the fibre orientation angle. Three possible types of Failure for the repair joints were analysed in order to predict the expected Failure Paths and Failure loads. The general agreement between the experimental observations, and predictions of the Failure Path and loads was found to be good.
Youngkeun Chang - One of the best experts on this subject based on the ideXlab platform.
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locus of Failure between a nanowire coated leadframe and an epoxy based molding compound
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hoyoung Lee, Youngkeun ChangAbstract:CuO nanowires were formed on the surface of copper-based leadframe sheets by oxidation in a hot alkaline solution. The nanowire-coated copper-based leadframe sheets were molded with epoxy molding compound (EMC). The molded bodies of nanowire-coated metal (copper-based leadframe)/polymer (EMC) were machined to form sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of the nanowire-coated leadframe/EMC interfaces. The SBN specimen was designed to measure the fracture toughness of the nanowire-coated leadframe/EMC interfaces under mixed-mode (mode I + mode II) loading condition. Fracture surfaces were analyzed by various equipment to investigate Failure Path. An attempt to determine the reasons why different types of Failure occurred was made by introducing a simple adhesion model. Research results have shown that hackle-type Failure occurred in the SBN specimens. Although the Failure Path in the SBN specimens is not dependent on the phase angle as well as the distance from the tip of the pre-crack, it is found that the Failure Path of the SBN specimens can be explained well by using the adhesion model.
