scholarly journals On the tensile fracture behavior of Cr coating for ATF cladding considering the effect of pre-oxidation

2021 ◽  
Vol 2076 (1) ◽  
pp. 012047
Author(s):  
Ziyan Pan ◽  
Mingduo Yuan ◽  
Zhenyu Zou ◽  
Weijian Zhang ◽  
Mingyue Du ◽  
...  
Keyword(s):  
Interfacial Strength ◽  
Tensile Fracture ◽  
Fracture Mechanisms ◽  
Failure Behavior ◽  
Premature Failure ◽  
Interfacial Cracks ◽  
Micro Cracks ◽  
Coating Microstructure ◽  
Cr Coating

Abstract In this study, the fracture mechanisms of Cr-coated Zr4 alloy samples were studied by in-situ tensile testing with high-resolution observations. Both original sample and pre-oxidized sample were studied to study the effects of pre-oxidation on the cracking and failure behavior. For the Cr-coated Zr4 sample, with the increase of tensile strain, multiple surface cracks were dominant and less interfacial cracks were formed, indicating good interfacial strength of Cr coating. For the pre-oxidized samples, there was a thin oxide layer formed on the Cr coating surface, revealing improved oxidation resistance and protection effects. However, a brittle ZrCr2 diffusion layer was formed in the same while at the Cr/Zr4 interface underneath the Cr coating, which would lead to earlier micro-cracks formed under tensile stress and evidently degrade the interfacial strength. The findings in the study indicated the importance of optimizing coating microstructure in future study to avoid forming the above-mentioned brittle diffusion interlayer and the associated premature failure.

In Situ SEM Investigation of Tensile Fracture Process of Fe-25Cr-35Ni Based Superalloy

2011 ◽  
Vol 279 ◽  
pp. 39-43 ◽  
Author(s):  
Jing Feng Guo ◽  
Ren Gen Xu ◽  
Li Zhao ◽  
Wen Zhu Shao ◽  
Lian Jie Qin
Keyword(s):  
Tensile Load ◽  
Tensile Fracture ◽  
Second Phase ◽  
Growing Up ◽  
Notched Specimen ◽  
Micro Cracks ◽  
Second Phase Particles ◽  
Initiation And Propagation ◽  
Stress Concentration Region

Initiation and propagation of micro cracks in the Fe-25Cr-35Ni based superalloy were observed and investigated through in situ tensile test in SEM using a single-edge notched specimen. The results show that the micro crack sources may easily occur with one of those, the second phase particles and matrix interface, and the stress concentration region. The micro-cracks which propagated at first for those that are perpendicular to the tensile load would be growing up and connected mutual with the increase of external stress until forming the main crack. While the length of the mail crack enlarged enough in the specimen, it become instable for the main cracks and the fracture occurred rapidly.

scholarly journals Numerical modeling of cracking behavior in Cr coating for ATF cladding under three-point bending

2021 ◽  
Vol 2076 (1) ◽  
pp. 012088
Author(s):  
Mingduo Yuan ◽  
Ziyan Pan ◽  
Zhenyu Zou ◽  
Weijian Zhang ◽  
Mingyue Du ◽  
...  
Keyword(s):  
Cohesive Zone Model ◽  
Local Stress ◽  
In Situ Observation ◽  
Zone Model ◽  
Cracking Behavior ◽  
Three Point Bending ◽  
Interfacial Cracks ◽  
Crack Tips ◽  
Cr Coating

Abstract In-situ three-point bending tests and finite element modeling based on the cohesive zone model were developed to study the stress evolution and cracking behavior of the Cr coated Zr-4 alloy for accident tolerant fuel claddings. The initiation and propagation of micro-cracks were captured by in-situ observation and predicted by the numerical simulation. The results showed that vertical cracks first initiated from the coating surface and propagated to the Cr/Zr4 interface. Under larger bending strain, interfacial cracks began to initiate from the vertical crack tips driven by large local stress concentration.

scholarly journals Elastoplastic Deformation and Fracture Behavior of Cr-Coated Zr-4 Alloys for Accident Tolerant Fuel Claddings

2021 ◽  
Vol 9 ◽  
Author(s):  
Xianfeng Ma ◽  
Wenjie Zhang ◽  
Zejia Chen ◽  
Dong Yang ◽  
Jishen Jiang ◽  
...  
Keyword(s):  
Strain Localization ◽  
Grain Orientation ◽  
Elastoplastic Deformation ◽  
Fracture Behavior ◽  
Tensile Tests ◽  
Crystal Plasticity Finite Element ◽  
Interfacial Cracks ◽  
Deformation And Fracture ◽  
Cr Coating

In situ tensile tests and crystal plasticity finite element modeling (CPFEM) were used to study the deformation and cracking behaviors of Cr-coated Zr-4 alloys for accident tolerant fuel claddings under tension. Based on the experimental results, vertical cracks in the coating generally initiated from the interface between the coating and the substrate, and expanded to the top surface of the coating. In addition, under large deformation, the vertical cracks also resulted in interfacial cracks that initiated from the cracking tips and propagated along the interface. According to the CPFEM, the cracking behaviors were mainly caused by the substantial stress concentration at the coating/substrate interface and at the grain boundaries in the Cr coating. The preferential crack initiation was related to the strain localization associated with grain orientation variation and strain mismatch.

Volcanic Glass as a Natural Analog for Borosilicate Waste Glass

1993 ◽  
Vol 333 ◽  
Author(s):  
Maury E. Morgenstein ◽  
Don L. Shettel
Keyword(s):  
Silica Glass ◽  
Glass Structure ◽  
Volcanic Glass ◽  
Waste Glass ◽  
Tensile Failure ◽  
Tensile Fracture ◽  
Failure Behavior ◽  
Basaltic Glass ◽  
Glass Waste ◽  
Natural Analog

ABSTRACTObsidian and basaltic glass are opposite end-members of natural volcanic glass compositions. Syngenetic and diagenetic tensile failure in basaltic glass (low silica glass) is pervasive and provides abundant alteration fronts deep into the glass structure. Perlitic fracturing in obsidian (high silica glass) limits the alteration zones to an “onion skin” geometry. Borosilicate waste glass behaves similarly to the natural analog of basaltic glass (sideromelane).During geologic time, established and tensile fracture networks form glass cells (a three-dimensional reticulated pattern) where the production of new fracture surfaces increases through time by geometric progression. This suggests that borosilicate glass monoliths will eventually become rubble. Rates of reaction appear to double for every 12C° of temperature increase. Published leach rates suggest that the entire inventory of certain radionuclides may be released during the 10,000 year regulatory time period. Steam alteration prior to liquid attack combined with pervasive deep tensile failure behavior may suggest that the glass waste form is not license defensible without a metallic- and/or ceramic-type composite barrier as an overpack.

Interfacial adhesion of nanoporous zeolite thin films

2006 ◽  
Vol 21 (2) ◽  
pp. 505-511 ◽  
Author(s):  
Lili Hu ◽  
Junlan Wang ◽  
Zijian Li ◽  
Shuang Li ◽  
Yushan Yan
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Interfacial Adhesion ◽  
Interfacial Strength ◽  
Future Generation ◽  
In Situ Growth ◽  
Seeded Growth ◽  
Si Substrates ◽  
Film Substrate

Nanoporous silica zeolite thin films are promising candidates for future generation low-dielectric constant (low-k) materials. During the integration with metal interconnects, residual stresses resulting from the packaging processes may cause the low-k thin films to fracture or delaminate from the substrates. To achieve high-quality low-k zeolite thin films, it is important to carefully evaluate their adhesion performance. In this paper, a previously reported laser spallation technique is modified to investigate the interfacial adhesion of zeolite thin film-Si substrate interfaces fabricated using three different methods: spin-on, seeded growth, and in situ growth. The experimental results reported here show that seeded growth generates films with the highest measured adhesion strength (801 ± 68 MPa), followed by the in situ growth (324 ± 17 MPa), then by the spin-on (111 ± 29 MPa). The influence of the deposition method on film–substrate adhesion is discussed. This is the first time that the interfacial strength of zeolite thin films-Si substrates has been quantitatively evaluated. This paper is of great significance for the future applications of low-k zeolite thin film materials.

Mechanics of Geological Materials

1985 ◽  
Vol 38 (10) ◽  
pp. 1256-1260 ◽  
Author(s):  
M. M. Carroll
Keyword(s):  
Solid Mechanics ◽  
Oil And Gas ◽  
Rock Fracture ◽  
Energy Resource ◽  
Earthquake Hazard ◽  
Soil Liquefaction ◽  
Failure Behavior ◽  
Geological Materials ◽  
In Situ Conditions

Needed advances in various areas of energy resource recovery, underground construction, earthquake hazard reduction, and conventional and nuclear defense depend critically on the development of improved theories for mechanical and thermal behavior of geological materials. The areas include oil and gas (including off-shore and Arctic production), mining and in situ recovery, geothermal production, nuclear waste isolation, under-ocean tunneling, underground storage, nuclear test containment, and effects of surface explosions. The needed developments, some of which are detailed in earlier National Academy of Science reports, include constitutive theories for inelastic deformation, failure, and post-failure behavior, influence of microstructure and macrostructure, rock fracture (direct breakage, hydraulic fracture explosive fracture), frictional sliding, soil liquefaction, mechanics of ice, determination of in situ conditions, flow through porous media, and thermal effects. Advances in mechanics of geological materials will require adaptation of some established techniques in rheology, metal plasticity, composite materials, mixtures, etc., and also the development of some entirely new ideas and methods. The complicated nature of rocks and soils, the wide ranges of stress, temperature, strain rate, etc., the interactions encountered in geotechnical processes, and the vastly different dimensions and time scales involved, lead to a host of challenging problems in solid mechanics.

Nanoclay-reinforced Polyacrylamide Composite: Synthesis, Structural and Mechanical Characterization

2009 ◽  
Vol 1239 ◽  
Author(s):  
Yong Sun ◽  
Zaiwang Huang ◽  
Xiaodong Li
Keyword(s):  
Thin Films ◽  
Deformation Behavior ◽  
Mechanical Characterization ◽  
Interfacial Strength ◽  
Localized Deformation ◽  
Nano Indentation ◽  
Atomic Force ◽  
Nanocomposite Thin Films ◽  
Synthesized Materials

AbstractA facile electrophoretic deposition method was successfully applied to achieve novel nanoclay-reinforced polyacrylamide nanocomposite thin films. A special curled architecture of the re-aggregated nanoclay-platelets was identified, providing a possible source for realizing the interlocking mechanism in the nanocomposites. The curled architecture could be the result from strain releasing when the thin films were peeled off from the substrates. Through micro-/nano-indentation and in situ observation of the deformation during tensile test with an atomic force microscope (AFM), the localized deformation mechanism of the synthesized materials was investigated in further details. The results implied that a localized crack diversion mechanism worked in the synthesized nanocomposite thin films, which resembled its nature counterpart-nacre. The deformation behavior and fracture mechanism were discussed with reference to lamellar structure, interfacial strength between the nanoclays and the polyacrylamide matrix, and nanoclay agglomeration.

scholarly journals LSSVM-Based Rock Failure Criterion and Its Application in Numerical Simulation

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Changxing Zhu ◽  
Hongbo Zhao ◽  
Zhongliang Ru
Keyword(s):  
Rock Mass ◽  
Failure Criterion ◽  
Nonlinear Problems ◽  
Failure Criteria ◽  
Rock Failure ◽  
Support Vector ◽  
Failure Behavior ◽  
Circular Tunnel ◽  
Vector Machines

A rock failure criterion is very important for the prediction of the failure of rocks or rock masses in rock mechanics and engineering. Least squares support vector machines (LSSVM) are a powerful tool for addressing complex nonlinear problems. This paper describes a LSSVM-based rock failure criterion for analyzing the deformation of a circular tunnel under differentin situstresses without assuming a function form. First, LSSVM was used to represent the nonlinear relationship between the mechanical properties of rock and the failure behavior of the rock in order to construct a rock failure criterion based on experimental data. Then, this was used in a hypothetical numerical analysis of a circular tunnel to analyze the mechanical behavior of the rock mass surrounding the tunnel. The Mohr-Coulomb and Hoek-Brown failure criteria were also used to analyze the same case, and the results were compared; these clearly indicate that LSSVM can be used to establish a rock failure criterion and to predict the failure of a rock mass during excavation of a circular tunnel.

Characterization of Melting and Solidification Phenomena in Electromagnetic Punching of Aluminum Tubes

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
De Waele Wim ◽  
Faes Koen ◽  
Van Haver Wim
Keyword(s):  
Plastic Deformation ◽  
Energy Levels ◽  
High Energy ◽  
Effect Of Temperature ◽  
Fracture Mechanisms ◽  
Time Interval ◽  
Short Time Interval ◽  
Total Width ◽  
Premature Failure ◽  
Charging Energy

Electromagnetic punching of tubular products is considered to be a promising innovative perforating process. The required punching energy decreases when using high velocities. Also, less tools are required when compared to conventional mechanical punching. However, the increase in punching speed can involve new strain and fracture mechanisms which are characteristic of the dynamic loading. In high energy rate forming processes the effect of temperature versus time gradient on the material properties becomes important due to the heat accumulated from plastic deformation and friction. The deformation induced heating will promote strain localization in it, possibly degrade its formability and cause premature failure in the regions of high localized strain. The feasibility of the electromagnetic pulse forming process for punching holes in aluminum cylindrical specimens has been investigated on an experimental trial-and-error basis. Experiments were performed using a Pulsar system (model 50/25) with a maximum charging energy of 50 kJ and a discharge circuit frequency of 14 kHz. Microscopic and metallographic inspection of the punched workpieces, together with hardness measurements, was performed to critically evaluate the quality of the cuts. It was observed that damage occurred at part of the edge of the punched hole during some of the perforation experiments. It was evidenced that in most workpieces, especially those performed at higher charging energy levels, a considerably high temperature must have been reached in the regions near the punched hole. The aluminum in this region was assumed to have melted and resolidified. These assumptions were affirmed by the following observations. Microscopic-size precipitates present in the unaffected base metal microstructure, had completely dissolved in that region; shrinkage cavities and dendrite rich regions were clearly visible. Next to this region, a heat affected zone was present where the grain boundaries had partially melted and precipitates partially disappeared. Considerably high temperatures, in the order of 520 to 660 °C, were reached in the regions around the punched holes, leading to melting and resolidification of the material. The total width of the thermally affected regions appeared to be larger at higher energy levels. The combination of heat generated by ohmic heating and by plastic deformation in a very short time interval is the most probable cause of the high peak temperatures that have occurred during the electromagnetic punching process.

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