Failure mechanics of thin coatings under multiaxial loading

AbstractSome of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes, while a few more advanced models employ two damage variables. Models with a single variable have an inherent difficulty in accounting for the damage accrued due to tensile and compressive actions in appropriately different manners, and their mutual dependencies. In the current models that adopt two damage variables, the independence of these damage variables during cyclic loading results in the failure to capture the effects of tensile damage on the compressive behavior of concrete and vice-versa. This study presents a cyclic model established by extending an existing monotonic constitutive model. The model describes the cyclic behavior of concrete under multiaxial loading conditions and considers the influence of tensile/compressive damage on the compressive/tensile response. The proposed model, dubbed the enhanced concrete damage plasticity model (ECDPM), is an extension of an existing model that combines the theories of classical plasticity and continuum damage mechanics. Unlike most prior studies on models in the same category, the performance of the proposed ECDPM is evaluated using experimental data on concrete specimens at the material level obtained under cyclic multiaxial loading conditions including uniaxial tension and confined compression. The performance of the model is observed to be satisfactory. Furthermore, the superiority of ECDPM over three previously proposed constitutive models is demonstrated through comparisons with the results of a uniaxial tension-compression test and a virtual test.

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Study on the Influence of the Ball Material on Abrasive Particles’ Dynamics in Ball-Cratering Thin Coatings Wear Tests

Materials ◽

10.3390/ma14030668 ◽

2021 ◽

Vol 14 (3) ◽

pp. 668

Author(s):

Gustavo Pinto ◽

Andresa Baptista ◽

Francisco Silva ◽

Jacobo Porteiro ◽

José Míguez ◽

...

Keyword(s):

Aisi 304 ◽

Thin Coatings ◽

Iron And Steel ◽

Test Configuration ◽

Abrasive Particles ◽

Aisi 52100 ◽

Aisi 304 Steel ◽

Aisi 52100 Steel ◽

Steel Balls ◽

Particles Dynamics

Micro-abrasion remains a test configuration hugely used, mainly for thin coatings. Several studies have been carried out investigating the parameters around this configuration. Recently, a new study was launched studying the behavior of different ball materials in abrasive particles’ dynamics in the contact area. This study intends to extend that study, investigating new ball materials never used so far in this test configuration. Thus, commercial balls of American Iron and Steel Institute (AISI) 52100 steel, Stainless Steel (SS) (AISI) 304 steel and Polytetrafluoroethylene (PTFE) were used under different test conditions and abrasive particles, using always the same coating for reference. Craters generated on the coated samples’ surface and tracks on the balls’ surface were carefully observed by Scanning Electron Microscopy (SEM) and 3D microscopy in order to understand the abrasive particles’ dynamics. As a softer material, more abrasive particles were entrapped on the PTFE ball’s surface, generating grooving wear on the samples. SS AISI 304 balls, being softer than the abrasive particles (diamond), also allowed particle entrapment, originating from grooving wear. AISI 52100 steel balls presented particle dynamics that are already known. Thus, this study extends the knowledge already existing, allowing to better select the ball material to be used in ball-cratering tests.

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Thin coatings for fire protection: An overview of the existing strategies, with an emphasis on layer-by-layer surface treatments and promising new solutions

Progress in Organic Coatings ◽

10.1016/j.porgcoat.2021.106217 ◽

2021 ◽

Vol 154 ◽

pp. 106217

Author(s):

Anne-Lise Davesne ◽

Maude Jimenez ◽

Fabienne Samyn ◽

Serge Bourbigot

Keyword(s):

Fire Protection ◽

Surface Treatments ◽

Layer By Layer ◽

Layer Surface ◽

Thin Coatings

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Failure mechanics and infrared radiation characteristics of soft coal at various moisture contents

Geomatics Natural Hazards and Risk ◽

10.1080/19475705.2021.1920479 ◽

2021 ◽

Vol 12 (1) ◽

pp. 1370-1384

Author(s):

Yiju Tang ◽

Jing Liu ◽

Tianxuan Hao ◽

Fan Li ◽

Lizhen Zhao

Keyword(s):

Infrared Radiation ◽

Radiation Characteristics ◽

Failure Mechanics ◽

Moisture Contents ◽

Soft Coal

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Bio-based polyurethane nanocomposite thin coatings from two comparable POSS with eight same vertex groups for controlled release urea

Scientific Reports ◽

10.1038/s41598-021-89254-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lixia Li ◽

Meng Wang ◽

Xiandong Wu ◽

Wenping Yi ◽

Qiang Xiao

Keyword(s):

In Situ Polymerization ◽

Polyhedral Oligomeric Silsesquioxanes ◽

Poly Ethylene Glycol ◽

Thin Coatings ◽

Polyurethane Coatings ◽

Coated Urea ◽

Poly Ethylene ◽

Coated Fertilizer ◽

Polyurethane Matrix

AbstractNanocomposite modification has attracted much attention in improving properties of bio-based polymer coating material for coated fertilizer. Herein two comparable polyhedral oligomeric silsesquioxanes (POSS), with eight poly(ethylene glycol) (PEG) and octaphenyl groups attached to the cage, respectively, were successfully incorporated into thin castor oil-based polyurethane coatings via in-situ polymerization on the urea surface. The nanostructure coatings are environmentally friendly, easy to prepare, and property-tunable. The results show that the vertex group of POSS had a pronounced influence on dispersion level and interaction between polyurethane and POSS that well-tuned the release pattern and period of coated urea, even at the coating rate as low as of 2 wt%. The liquid POSS with long and flexible PEG groups had better compatibility and dispersibility in polyurethane matrix than the solid POSS with rigid octaphenyl groups, as evidenced by SEM/EDS. The unique properties were resulted from the different extents of physical crosslinkings. This modification of bio-based polyurethane coating with POSS provided an alternative method of regulating and controlling the properties of coated fertilizer.

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