scholarly journals Evaluating Corrosion Damage Evolution of Cement Mortar in Acid Environment via Relative Elasticity Modulus Method

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Elastic Modulus ◽  
Damage Evolution ◽  
Cement Mortar ◽  
Corrosion Damage ◽  
Surface Damage ◽  
Relative Method ◽  
Damage Layer ◽  
Damage Degree ◽  
Acid Environment ◽  
Hcl Concentration

In order to study the damage variation along thickness from surface, a relative method combined with impulse excitation test was studied in this work to evaluate the elastic modulus of cement mortar corrosion damage layer, by simulating the damage layer as a coating. The damage layer with different damage degree is treated as multilayer coatings in which each layer has different properties. The elastic modulus of each layer is determined by using the relative method step by step. Single face of Portland cement mortar specimens was exposed in an aggressive environment, with 0%, 5%, 7.5% and 10% HCl content, respectively. The corrosion damage degree and evolution law of the mortar were investigated by measuring the elastic modulus of surface damage layer. With the increase of HCl concentration, thickness of corrosion damage layer increased and the modulus of the damage layer decreased greatly. The elastic modulus of each corrosion layer was obtained at different depths. By this way, damage depth and damage evolution were evaluated effectively.

Comparison of corrosion resistance properties of Ni-P and Ni-W-P coatings obtained by electroless deposition

2020 ◽  
Vol 25 (2) ◽  
pp. 66-71
Author(s):  
A.B. Drovosekov
Keyword(s):  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
Electroless Deposition ◽  
Corrosion Damage ◽  
Electrochemical Activity ◽  
High Porosity ◽  
Environment Analysis ◽  
Damage Degree ◽  
Lower Porosity ◽  
Electroless Coatings

Corrosion resistance properties, such as porosity, stability in the atmosphere of NaCl mist, and anodic electrochemical activity in a sulfuric acid solution are studied and compared for Ni-W-P and Ni-P coatings obtained by electroless deposition. The studied coatings were obtained from solutions with glycine as the main ligand and contained 10.2 to 15.6 at.% of phosphorus and up to 3.3 at.% of tungsten. It is shown that Ni-W-P coatings with a tungsten content of 2.3 to 3.3 at.% and a thickness of 15 μm have a significantly lower porosity as compared with nickel-phosphorus coatings of the same thickness. Also, significantly better stability of Ni-W-P coatings in a NaCl mist atmosphere was observed, their corrosion damage degree is less than that of Ni-P coatings, and relatively little depends on the duration of exposure in a corrosive environment. Analysis of anodic polarization curves showed an almost similar electrochemical activity upon dissolution of Ni-P and Ni-W-P coatings in sulfuric acid. Both these types of electroless coatings showed a markedly better tendency to anodic dissolution than pure nickel. Taking into account the obtained experimental data, a conclusion is made as to the better protective characteristics of Ni-W-P coatings in comparison with nickel-phosphorus coatings. The main reason of the inferior protective properties of Ni-P coatings is their relatively high porosity.

scholarly journals Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 809
Author(s):  
Wei Yang ◽  
Chengwu Li ◽  
Rui Xu ◽  
Xunchang Li
Keyword(s):  
Damage Evolution ◽  
Resonance Effect ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Frequency Characteristics ◽  
Evolution Process ◽  
Deformation And Failure ◽  
Time Frequency ◽  
Rock Materials ◽  
Damage Degree

The deformation and failure of coal and rock materials is the primary cause of many engineering disasters. How to accurately and effectively monitor and forecast the damage evolution process of coal and rock mass, and form a set of prediction methods and prediction indicators is an urgent engineering problems to be solved in the field of rock mechanics and engineering. As a form of energy dissipation in the deformation process of coal and rock, microseismic (MS) can indirectly reflect the damage of coal and rock. In order to analyze the relationship between the damage degree of coal and rock and time-frequency characteristics of MS, the deformation and fracture process of coal and rock materials under different loading modes was tested. The time-frequency characteristics and generation mechanism of MS were analyzed under different loading stages. Meanwhile, the influences of properties of coal and rock materials on MS signals were studied. Results show that there is an evident mode cutoff point between high-frequency and low-frequency MS signals. The properties of coal and rock, such as the development degree of the original fracture, particle size and dense degree have a decisive influence on the amplitude, frequency, energy and other characteristic parameters of MS signals. The change of MS parameters is closely related to material damage, but has no strong relation with the loading rate. The richness of MS signals before the main fracture depends on the homogeneity of materials. With the increase of damage, the energy release rate increases, which can lead to the widening of MS signals spectrum. The stiffness and natural frequency of specimens decreases correspondingly. Meanwhile, the main reason that the dominant frequency of MS detected by sensors installed on the surface of coal and rock materials is mainly low-frequency is friction loss and the resonance effect. In addition, the spectrum and energy evolution of MS can be used as a characterization method of the damage degree of coal and rock materials. Furthermore, the results can provide important reference for prediction and early warning of some rock engineering disasters.

scholarly journals Research on the Corrosion Damage Mechanism of Concrete in Two Freeze–Thaw Environments

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xianhua Yao ◽  
Min Zhang ◽  
Junfeng Guan ◽  
Lielie Li ◽  
Weifeng Bai ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Erosion Resistance ◽  
Corrosion Damage ◽  
Damage Mechanism ◽  
Resistance Coefficient ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw ◽  
Environment Temperature ◽  
Performance Deterioration ◽  
Air Void

This study aims to investigate the effects of two freeze–thaw environments (i.e., maintenance freeze-thaw (MFT) environment and immersion freeze-thaw (IFT) environment) on the durability performance, deterioration rules, and mechanisms of concrete. In MFT, the concrete specimens were firstly cured in the standard curing environment (temperature, 20 ± 3, humidity, not less than 95%, and ages, 28 d) and then were carried out in freeze–thaw environment, while in IFT, the concrete specimens were firstly cured in the salt (NaHCO3, NaCl, and Na2SO4) immersion environment for 90 d and then were carried out in freeze–thaw environment. In this study, the damage features, relative dynamic elastic modulus, mass changes, and erosion-resistance coefficient of concrete have been measured. Thereafter, using the scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP), the air-void structure parameters and the microstructures have been measured, respectively. The results show that the relative dynamic elastic modulus and the erosion-resistance coefficient of the compressive strength of the concrete in the IFT environment are, respectively, 14.3% and 21.0% higher than those of the concrete in the MFT environment. In addition, the results of the microstructure analyses show that the corrosion damages of the concrete are mainly caused by the combined action of the corrosion products of ettringite and freeze–thaw environment. However, the damage to the concrete in the MFT environment is more serious than that in the IFT environment. The results of the MIP analysis show that the harmful pore value for the concrete in the MFT environment is almost two times larger than that for the concrete in the IFT environment.

scholarly journals Low Energy, Low Angle, Large Area Ion Polishing for Improved EBSD Indexing

2009 ◽  
Vol 17 (3) ◽  
pp. 30-35
Author(s):  
S.D. Walck ◽  
J.R. Porter ◽  
H-W. Yang ◽  
S.S. Dheda
Keyword(s):  
Current Density ◽  
Surface Defects ◽  
Incident Angle ◽  
Surface Damage ◽  
Beam Current ◽  
Mechanical Polishing ◽  
Beam Current Density ◽  
Large Area ◽  
Electron Backscattered Diffraction ◽  
Damage Layer

Good sample preparation is essential for acquiring successful electron backscattered diffraction (EBSD) patterns in the SEM. Mechanical polishing to obtain the required surface quality with minimal sub-surface defects and deformation that does not interfere with the quality of the diffraction data is, more often than not, an art form. Special polishing techniques, such as low force lapping fixtures, electrochemical-mechanical polishing, and vibratory polishing, have been used to minimize the sub-surface damage, but have not eliminated it. Ion polishing has been used to reduce the damage layer further. However, the commercially available ion systems suffer several drawbacks, including: 1) small area treatment (≤ 1 cm) 2) decreasing beam current density with accelerating voltages, and 3) the inability to process non-conducting samples. Barna and Pecz have shown that at 3 keV with an incident angle of 5° relative to the surface, approximately 25 nm of ion damage occurs in Si and GaAs, but at 250 eV, there is less than 1 nm of amorphization of the surface. They also showed that a glancing angle across the surface is essential for removing topographic features. The ion guns that have been available for ion polishing and ion etching of SEM samples typically cannot operate effectively below 3 keV because of the low current density.

scholarly journals Influence of sub-surface damage evolution on low-energy-plasma-driven deuterium permeation through tungsten

2018 ◽  
Vol 58 (5) ◽  
pp. 056027 ◽  
Author(s):  
Stefan Kapser ◽  
Martin Balden ◽  
Tiago Fiorini da Silva ◽  
Stefan Elgeti ◽  
Armin Manhard ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Surface Damage ◽  
Low Energy

Comparison of diffraction methods for measurement of surface damage in superalloys

2006 ◽  
Vol 21 (7) ◽  
pp. 1775-1781 ◽  
Author(s):  
L.N. Brewer ◽  
M.A. Othon ◽  
Y. Gao ◽  
B.T. Hazel ◽  
W.H. Buttrill ◽  
...  
Keyword(s):  
Surface Damage ◽  
High Energy ◽  
Machining Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Damage Layer ◽  
Potential Source ◽  
Machining Operations ◽  
Electron Back Scattered Diffraction ◽  
Super Alloy

Surface damage from machining operations is a potential source of failure in metallic components. The ability to quantitatively characterize the depth and extent of the damage layer is critical to controlling the machining process. Electron back scattered diffraction and synchrotron high energy x-ray diffraction were applied to the measurement of machining surface damage in a Ni-based super alloy. Both techniques clearly showed a plastic deformation profile below the surface as a function of the machining conditions used. Using the average intragrain misorientation parameter, the electron back scattered diffraction was able to quantify the amount of surface damage from one surface treatment to another. In addition, the x-ray diffraction measurements were able to simultaneously measure the elastic strain as a function of depth from the surface.

Evaluating elastic modulus and strength of hard coatings by relative method

2007 ◽  
Vol 458 (1-2) ◽  
pp. 268-274 ◽  
Author(s):  
Y.W. Bao ◽  
Y.C. Zhou ◽  
X.X. Bu ◽  
Y. Qiu
Keyword(s):  
Elastic Modulus ◽  
Hard Coatings ◽  
Relative Method
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