A waste-derived nanocomposite sealant for repairing micro-cracks in concrete

2022 ◽  
pp. 103965
Author(s):  
Uthradevi Kannan ◽  
Shibil Abdul Gafoor ◽  
Sonali Srivastava ◽  
M. Nithyadharan ◽  
Soujit Sen Gupta ◽  
...  
Keyword(s):  
Micro Cracks

Properties of Self-Compacting Cementitious Composite Materials Containing Cement Kiln Dust Powder

2020 ◽  
Vol 38 (6A) ◽  
pp. 879-886
Author(s):  
Ahmed S. Kadhim ◽  
Alaa A. Atiyah ◽  
Shakir A. Salih
Keyword(s):  
Composite Materials ◽  
Total Porosity ◽  
Cement Kiln Dust ◽  
Cement Kiln ◽  
Cementitious Composite ◽  
Cement Dust ◽  
Micro Cracks ◽  
Load Carrying ◽  
Sustainable Materials ◽  
Kiln Dust

This paper aims to investigate the influence of utilization micro cement kiln dust as a sustainable materials additive in order to reduce the voids and micro cracks in the cementitious mortar materials which cause a drastic reduction in the load carrying capacity of the element. Its therefore very important to decrease the pores and enhance the mechanical strength of the cementitious composite materials. In this article, the properties of self-compacting mortar containing micro cement dust additive was experimentally assessed. Micro cement dust powder was added to the self-compacting mortar in (1, 2, 3, 4 and 5 %) percentage by weight of cement to be used as cementitious sustainable materials. The experimental results indicated that the modification and enhancement of the workability of fresh mixture and the mechanical strengths of self-compacting mortar were increased as micro cement dust additives increases. Also; the water absorption and total porosity were decreased with increases of micro cement dust powder.

Temperature and Humidity Dependent Reliability Analysis of RGB LED Chips

2006 ◽  
Author(s):  
Jun-Xian Fu ◽  
Shukri Souri ◽  
James S. Harris
Keyword(s):  
Reliability Analysis ◽  
Printed Circuit Board ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Light Emitting ◽  
Printed Circuit ◽  
Root Cause ◽  
Micro Cracks ◽  
Temperature And Humidity

Abstract Temperature and humidity dependent reliability analysis was performed based on a case study involving an indicator printed-circuit board with surface-mounted multiple-die red, green and blue light-emitting diode chips. Reported intermittent failures were investigated and the root cause was attributed to a non-optimized reflow process that resulted in micro-cracks and delaminations within the molding resin of the chips.

Detection of Micro-Cracks in Electroluminescence Images of Photovoltaic Modules

2020 ◽  
Author(s):  
Natasha Mathias ◽  
Farheen Shaikh ◽  
Chirayu Thakur ◽  
Sweekrithi Shetty ◽  
Pratibha Dumane ◽  
...  
Keyword(s):  
Photovoltaic Modules ◽  
Micro Cracks

scholarly journals Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063 Fillet Lap Joint in Automotive Battery Tray Construction

2021 ◽  
Vol 11 (10) ◽  
pp. 4522
Author(s):  
Tianzhu Sun ◽  
Pasquale Franciosa ◽  
Conghui Liu ◽  
Fabio Pierro ◽  
Darek Ceglarek
Keyword(s):  
Laser Welding ◽  
Fusion Zone ◽  
Aluminium Alloys ◽  
Mechanical Performance ◽  
Lap Joints ◽  
Fatigue Durability ◽  
Micro Cracks ◽  
Remote Laser Welding ◽  
Weld Fatigue ◽  
Weld Root

Remote laser welding (RLW) has shown a number of benefits of joining 6xxx aluminium alloys such as high processing speed and process flexibility. However, the crack susceptibility of 6xxx aluminium alloys during RLW process is still an open problem. This paper experimentally assesses the impact of transverse micro cracks on joint strength and fatigue durability in remote laser welding of AA6063-T6 fillet lap joints. Distribution and morphology of transverse micro cracks were acquired by scanning electron microscope (SEM) on cross-sections. Grain morphology in the weld zone was determined by electron backscatter diffraction (EBSD) while static tensile and dynamic fatigue tests were carried out to evaluate weld mechanical performance. Results revealed that increasing welding speed from 2 m/min to 6 m/min did not introduce additional transverse micro cracks. Additionally, welding at 2 m/min resulted in tensile strength improvement by 30% compared to 6 m/min due to the expansion of fusion zone, measured by the throat thickness, and refinement of columnar grains near fusion lines. Furthermore, the weld fatigue durability is significantly higher when fracture occurs in weld root instead of fusion zone. This can be achieved by increasing weld root angle with optimum weld fatigue durability at around 55°.

scholarly journals Selective Anisotropy of Mechanical Properties in Inconel718 Alloy

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3869
Author(s):  
Yu Liang ◽  
Jun Ma ◽  
Baogang Zhou ◽  
Wei Li
Keyword(s):  
Solid Solution ◽  
Crack Nucleation ◽  
Rolling Direction ◽  
Mechanical Anisotropy ◽  
Solution Temperature ◽  
Weak Anisotropy ◽  
Nucleation Sites ◽  
Micro Cracks ◽  
Δ Phase ◽  
Rupture Properties

Mechanical anisotropy behaviors are investigated in slightly rolled Inconel718 alloy with string-like δ phase and carbides produced during various solid-solution and aging treatments. A weak anisotropy in the strengths and rupture properties at 650 °C is visible, whereas ductility, i.e., reduction in area (RA) and impact toughness (CVN), presents a sound anisotropy behavior. MC carbides promote the operation of slip systems and thus are conducive to weakening the strength anisotropy. The RA anisotropy mainly stems from high-density δ phase particles that provide more crack nucleation sites and stimulate rapid propagation because of the shorter bridge distance between micro-cracks at the rolling direction. In contrast, CVN anisotropy arises from both δ phase and carbides at a lower solid-solution temperature of 940 °C but only depends on carbides at 980 °C where the δ phase fully dissolves. Apart from dislocation motions operated at room temperature, the activated grain boundary processes are responsible for the weak anisotropy of rupture properties at the elevated temperature. This work provides a guideline for technological applications in the hot working processes for Inconel718 alloys.

scholarly journals Mechanism research on crack propagation in coal induced by CO2 phase-transition fracturing under different lateral compression coefficients

2021 ◽  
pp. 014459872110153
Author(s):  
Qingsong Li ◽  
Jinlei Fu ◽  
Xianwei Heng ◽  
Xiaoqian Xu ◽  
Shu Ma
Keyword(s):  
Phase Transition ◽  
Crack Propagation ◽  
Initial Stress ◽  
Main Crack ◽  
Transition Process ◽  
Simulation Software ◽  
Lateral Compression ◽  
Monitoring Point ◽  
Micro Cracks ◽  
Fractured Coal

To study crack propagation around the fracture hole in the coal body induced by high-pressure CO2 gas produced by CO2 phase transition fracturing, the mechanism of permeability enhancement of fractured coal induced by liquid CO2 phase transition fracturing was studied from two aspects, the process of coal gas displacement by competitive adsorption and physical characteristics of fractured coal induced by phase transition. Crack propagation pattern in coal under different lateral coefficients was explored by using discrete-element numerical simulation software. Distribution characteristics of hoop stress of fractured coal were analyzed through theoretical calculation. The results show that: (1) Micro-cracks in damaged coal body generated during phase transition process are mainly crack_tension type, which are formed by the composite action of tension and compression. The crack propagation is the result of the continuous release of compressive stress from concentrated area to the surrounding units. Micro-cracks are radially distributed in a pattern of “flame”. (2) The main crack formed above the fracture hole grows in the direction of vertical minimum initial stress, and the main crack formed below the fracture hole develops in the direction of horizontal initial stress. As the lateral compression coefficient increases, the extension distance of the second crack will not change after reducing to a certain length. (3) As the distance from the fracture hole increases, the peak compression loaded at the monitoring point decays, and the loop stress in the cracked coal is distributed in a pattern of “peanut”. It provides practical methods and ideas for studying the macroscopic and microscopic development of cracks, as well as theoretical support for the on-site hole layout.

Self-Healing and Repairing Concrete Cracks Based on Bio-Mineralization

2014 ◽  
Vol 629-630 ◽  
pp. 494-503 ◽  
Author(s):  
Chun Xiang Qian ◽  
Mian Luo ◽  
Li Fu Ren ◽  
Rui Xing Wang ◽  
Rui Yang Li ◽  
...  
Keyword(s):  
Concrete Surface ◽  
Cellular Respiration ◽  
Self Healing ◽  
Capillary Suction ◽  
Water Permeation ◽  
Carbonate Ions ◽  
Micro Cracks ◽  
Small Cracks ◽  
The Common ◽  
The One

In this paper, three bio-mineralization mechanisms were proposed to repair cement-based materials cracks. The common feature is that the three are all induced by bacterial. A type of bacterial which can decompose urea and release carbonate ions could be applied to repair micro cracks on concrete surface when combining calcium ions. But what need to be noted is that the way of repairing cracks is passive. Some alkaliphilic bacterial spores could be added to concrete when casted and two different types of bacterial were used to realize the function of self-healing. The sources of carbonate ions made them different, the one release carbonate dioxide through its own cellular respiration, the other could transfer carbon dioxide in air to bicarbonate. Coefficient of capillary suction, apparent water permeation coefficient and area repairing rate were applied to characterize the repairing effectiveness. The tests results were that all three bio-mineralization mechanisms showed excellent repair effect to small cracks formed at early ages. When the bacteria were immobilized by ceramsite, the self-healing effect could be improved for the cracks formed at late ages.

Electrochemical characterization of micro-cracks in polyurethane resin films deposited on metallic surfaces

2016 ◽  
Vol 46 (12) ◽  
pp. 1237-1243 ◽  
Author(s):  
Karun K. Rao ◽  
Molly Ferguson ◽  
Kyle Murphy ◽  
Jean Zhao ◽  
Daniel Lacks ◽  
...  
Keyword(s):  
Electrochemical Characterization ◽  
Metallic Surfaces ◽  
Polyurethane Resin ◽  
Micro Cracks

Hard and Soft: Principles of Polyner-Impregnated Concrete Using Elastomers

2013 ◽  
Vol 687 ◽  
pp. 118-123 ◽  
Author(s):  
Oliver Weichold ◽  
Udo Antons
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Brittle Failure ◽  
Elastic Moduli ◽  
Domain Size ◽  
Glassy Polymers ◽  
Crack Deflection ◽  
Micro Cracks ◽  
Concrete Interface ◽  
Crystalline Matrix

The effect of incorporating elastomeric domains in concrete is described from the point of fracture mechanics. Concrete is subject to brittle failure, since cracks propagate at an enormous speed in the crystalline matrix. However, micro cracks are attracted to volume elements with lower elastic moduli such as elastomeric domains. Cracks that encounter the concrete-elastomer interface are stopped since energy is dissipated by plastic deformation of and/or crack deflection by the elastomer. The domain size and the distribution of the elastomer as well as, and properties of the elastomer-concrete interface are crucial parameters. Such a combination differs substantially from previously prepared polymer-impregnated concretes, in which only glassy polymers were used.

Creep Behavior of a 4.5% Re Nickel-Base Single Crystal Superalloy at High Temperature

2015 ◽  
Vol 750 ◽  
pp. 139-144 ◽  
Author(s):  
De Long Shu ◽  
Su Gui Tian ◽  
Xin Ding ◽  
Jing Wu ◽  
Qiu Yang Li ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Single Crystal ◽  
Deformation Mechanism ◽  
Creep Property ◽  
Single Crystal Superalloy ◽  
Micro Cracks ◽  
Initiation And Propagation ◽  
Temperature Ranges ◽  
Nickel Base

By means of heat treatment and creep property measurement, an investigation has made into the creep behaviors of a containing 4.5% Re nickel-base single crystal superalloy at high temperature. Results show that the elements W, Mo and Re are enriched in the dendrite arm regions, the elements Al, Ta, Cr and Co are enriched in the inter-dendrite region, and the segregation extent of the elements may be obviously reduced by means of heat treatment at high temperature. In the temperature ranges of 1070--1100 °C, the 4.5% Re single crystal nickel-based superallloy displays a better creep resistance and longer creep life. The deformation mechanism of the alloy during steady state creep is dislocations slipping in the γ matrix and climbing over the rafted γ′ phase. In the later stage of creep, the deformation mechanism of alloy is dislocations slipping in the γ matrix, and shearing into the rafted γ′ phase, which may promote the initiation and propagation of the micro-cracks at the interfaces of γ/γ′ phases up to the occurrence of creep fracture.

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