scholarly journals Effect of Excess Atomic Volume on Crack Evolution in a Deformed Iron Single Crystal

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6124
Author(s):  
Dmitrij S. Kryzhevich ◽  
Aleksandr V. Korchuganov ◽  
Konstantin P. Zolnikov
Keyword(s):  
Atomic Volume ◽  
Structural Defects ◽  
Crack Growth Behavior ◽  
Self Healing ◽  
Crack Evolution ◽  
Iron Single Crystal ◽  
Bcc Iron ◽  
Loaded Material ◽  
Crack Tips ◽  
Edge Cracks

This paper presents a molecular dynamics study of how the localization and transfer of excess atomic volume by structural defects affects the evolution and self-healing of nanosized cracks in bcc iron single crystals under different mechanical loading conditions at room temperature. It is shown that deformation is initially accompanied by a local growth of the atomic volume at the crack tips. The crack growth behavior depends on whether the excess atomic volume can be transferred by structural defects from the crack tips to the free surface or other interfaces. If an edge crack is oriented with respect to the loading direction so that dislocations are not emitted from its tip or only twins are emitted, then the sample undergoes a brittle-ductile fracture. The transfer of the excess atomic volume by dislocations from the crack tips prevents the opening of edge cracks and is an effective healing mechanism for nanocracks in a mechanically loaded material.

scholarly journals Development of Self-Healable Organic/Inorganic Hybrid Materials Containing a Biobased Copolymer via Diels–Alder Chemistry and Their Application in Electromagnetic Interference Shielding

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1755
Author(s):  
Yi-Huan Lee ◽  
Wen-Chi Ko ◽  
Yan-Nian Zhuang ◽  
Lu-Ying Wang ◽  
Tao-Wei Yu ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Hybrid System ◽  
Electromagnetic Interference ◽  
Diels Alder ◽  
Structural Defects ◽  
Material System ◽  
Self Healing ◽  
Electromagnetic Interference Shielding ◽  
Band Frequency ◽  
Inorganic Hybrid

In this study, a novel biobased poly(ethylene brassylate)-poly(furfuryl glycidyl ether) copolymer (PEBF) copolymer was synthesized and applied as a structure-directing template to incorporate graphene and 1,1′-(methylenedi-4,1-phenylene)bismaleimide (BMI) to fabricate a series of self-healing organic/inorganic hybrid materials. This ternary material system provided different types of diene/dienophile pairs from the furan/maleimide, graphene/furan, and graphene/maleimide combinations to build a crosslinked network via multiple Diels–Alder (DA) reactions and synergistically co-assembled graphene sheets into the polymeric matrix with a uniform dispersibility. The PEBF/graphene/BMI hybrid system possessed an efficient self-repairability for healing structural defects and an electromagnetic interference shielding ability in the Ku-band frequency range. We believe that the development of the biobased self-healing hybrid system provides a promising direction for the creation of a new class of materials with the advantages of environmental friendliness as well as durability, and shows potential for use in advanced electromagnetic applications.

Variation of Stress Intensity Factor and Crack Distance Length for Double Edge Crack in Human Femur Bone

2014 ◽  
Vol 695 ◽  
pp. 580-583
Author(s):  
Noor A. Md Zain ◽  
Ruslizam Daud ◽  
W.Z.A.W. Muhamad ◽  
Khairul Salleh Basaruddin ◽  
Yazid Bajuri ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Parallel Edge ◽  
Linear Elastic ◽  
Femur Bone ◽  
Double Edge ◽  
Crack Tips ◽  
Elastic Fracture ◽  
Edge Cracks

The theory of linear elastic fracture mechanic (LEFM) has proven that we can evaluate the amount of stress located at the crack tip by determining the stress intensity factor (). The stress at the tip of a sharp crack has the highest stress which can lead to failure on the material. Thus, the cracks within human bones are quite complicated because of the bone microstructure. There are a few factors that can minimize the effect of the cracks so that patients can heal much faster. Hence, this paper focuses on how several crack distances, between two parallel edge cracks can affect the value of stress intensity factor (). Using the LEFM theory, the interaction between two neighboring crack tips was investigated.

scholarly journals Parametric Vibrations of Axially Moving Beams with Multiple Edge Cracks

2019 ◽  
Vol 24 (2) ◽  
pp. 241-252 ◽  
Author(s):  
Murat Sarıgül
Keyword(s):  
Natural Frequencies ◽  
Equations Of Motion ◽  
Crack Depth ◽  
Multiple Cracks ◽  
Mean Velocity ◽  
Beam System ◽  
Crack Tips ◽  
Axially Moving Beams ◽  
Edge Cracks ◽  
Axially Moving

Nonlinear transverse vibrations of axially moving beams with multiple cracks is handled studied. Assuming that the beam moves with mean velocity having harmonically variation, influence of the edge crack on the moving continua are investigated in this study. Due to existence of the crack in the transverse direction, the healthily beam is divided into parts. The translational and rotational springs are replaced between these parts so that high stressed regions around the crack tips are redefined with the springs' energies. Thus, the problem is converted to an axially moving spring-beam system. The equations of motion and its corresponding conditions are obtained by means of the Hamilton Principle. In numerical analysis, the natural frequencies and responses of the spring-beam system are investigated for principal parametric resonance in detail. Some important results are obtained; the natural frequencies decreases with increasing crack depth. In case of the beam travelling with high velocities, the effects of crack's depth on natural frequencies seems to be vanished.

scholarly journals Self-Healing Properties of Cerium-Modified Molybdate Conversion Coating on Steel

2021 ◽  
Author(s):  
Rimantas Ramanauskas ◽  
Aliona Kirdeikiene ◽  
Olga Girciene ◽  
Laima Gudaviciute ◽  
Vitalija Jasulaitiene ◽  
...  
Keyword(s):  
Protective Coatings ◽  
Structural Characteristics ◽  
Element Distribution ◽  
Conversion Coating ◽  
Oxidation States ◽  
Structural Defects ◽  
Self Healing ◽  
Depth Profiles ◽  
Carbon Steel Surface ◽  
Voltammetric Measurements

A phosphate/molybdate and cerium-modified phosphate/molybdate conversion coatings were deposited on a carbon steel surface and their protective and self-healing abilities were evaluated. Surface morphology and inner structure of the coatings were examined using FE-SEM-FIB and TEM techniques, chemical composition and element distribution depth profiles in conversion layers were determined using EDX measurements, whereas XPS was applied for the analysis of Mo and Ce oxidation states. Voltammetric measurements and EIS were performed to assess the corrosion behavior of the samples. The higher protective and stronger self-healing abilities were found for phosphate/molybdate/cerium conversion coating deposited in a sulphate-containing solution. This was attributed to higher values of both: total cerium and Ce(IV) content in the conversion layer as well as to lower number of structural defects in the coating. It was demonstrated that the micro-structural characteristics of protective coatings are also important in determining self-healing abilities.

scholarly journals EFFECT OF TEXTURE ON FATIGUE PROPERTIES OF AGE-HARDENED Al ALLOYS UNDER ULTRASONIC LOADING

2012 ◽  
Vol 06 ◽  
pp. 294-299
Author(s):  
HIRONORI MATSUSAKO ◽  
KOHJI KARIYA ◽  
NORIO KAWAGOISHI ◽  
QINGYUAN WANG ◽  
MASAHIRO GOTO
Keyword(s):  
Growth Rate ◽  
Crack Growth ◽  
Al Alloys ◽  
Fatigue Properties ◽  
Crack Growth Behavior ◽  
Loading Frequency ◽  
Slip Planes ◽  
Crack Tips ◽  
High Crack ◽  
The Difference

Effects of texture and loading frequency on the fatigue crack growth behavior of an extruded and a drawn Al alloys of 2017-T4 were investigated under ultrasonic loading frequency (20kHz) in the relative humidity of 25% and 85%, respectively. The extruded alloy has a marked texture of (111) orientation, but this specified orientation is not observed in the drawn alloy. Most of fatigue life was occupied by the growth life of small cracks in the both alloys regardless of humidity. In the low humidity, crack growth was retarded at about 0.3 mm in length in the both alloys. Although crack growth was accelerated by high humidity in the early growth process, there was no or little influence of humidity on the growth rate of cracks over about 0.3 mm in the both alloys. After the retardation of crack growth, fracture surfaces featured with many slip planes in the extruded alloy and many facets in the drawn one, respectively. The difference in growth mechanism between short cracks (<0.3 mm) and longer ones (>0.3 mm) was caused by the environment at crack tips due to high crack growth rate under ultrasonic loading, and that between the both alloys was related to the degree of texture.

scholarly journals Self-Healing Properties of Cerium-Modified Molybdate Conversion Coating on Steel

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 194
Author(s):  
Aliona Kirdeikiene ◽  
Olga Girčiene ◽  
Laima Gudavičiūte ◽  
Vitalija Jasulaitiene ◽  
Algirdas Selskis ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Element Distribution ◽  
Conversion Coating ◽  
Structural Defects ◽  
Homogeneous Distribution ◽  
Self Healing ◽  
Carbon Steel Surface ◽  
Coating Morphology ◽  
The Relationship ◽  
Chromium Phosphate

Environmentally friendly alternatives to chromium—phosphate/molybdate and cerium-modified phosphate/molybdate conversion coatings—were deposited on a carbon steel surface. Different surface analytic techniques were applied to obtain complementary information on the composition, element distribution morphology and inner structure of the coatings in order to establish the relationship between coating properties and corrosion performance. The higher protective and stronger self-healing abilities were found for phosphate/molybdate/cerium conversion coating deposited in a sulphate-containing solution. The protective barrier strength was found to be related with certain aspects of the coating morphology such like homogeneous distribution of fine crystallites and, hence, lower number of structural defects. The self-healing ability depended on both, the composition (higher amount of Ce(IV)) and micro-structural characteristics, such as defectiveness, of the conversion layer.

scholarly journals ROAD SURFACE OF THE PAVEMENT COATING BRIDGE

2021 ◽  
Vol 6 (4) ◽  
pp. 21-35
Author(s):  
M. Vysotskaya ◽  
A. Kurlykina ◽  
D. Kuznecov ◽  
A. Tkacheva
Keyword(s):  
Asphalt Concrete ◽  
Concrete Surface ◽  
Operational Reliability ◽  
Road Surface ◽  
Structural Defects ◽  
Self Healing ◽  
Concrete Mixtures ◽  
Bridge Structures ◽  
The Rich ◽  
Materials Used

The current topic of the reliability of bridge structures in modern conditions and the role of the structural layers of the roadway (road surface) in increasing and maintaining their operational reliability and durability are considered. The existing standard designs of road surface clothing and the materials used for their arrangement are considered. The analysis and systematization of information from Russian and foreign sources on the construction of the clothing of the driving road indicates the prospects and technical and operational advantages of using cast asphalt concrete mixtures in the upper layers of the bridge pavement. It is noted that an effective road surface made of this material is capable of resisting existing loads, taking into account the specifics of the operation of the asphalt concrete surface during the established service life, additionally performing the protective waterproofing function of the metal structures of the bridge structure. The analysis of the literature demonstrates that active scientific research on the development and creation of effective cast asphalt concrete mixtures is primarily associated with the production and modification of its bituminous part, as a medium capable of initiating "self-healing" of the composite, independently eliminating structural defects. The rich experience of various methods of modifying bituminous binders, accumulated over the past few decades, allows to predict the prospects for using cast asphalt concrete in the construction of the roadway of bridge structures, based on improved binders, in order to create new high-quality materials that can improve the quality of the bridge network in the country.

scholarly journals Modification of bituminous binders for guss asphalt

2021 ◽  
Vol 274 ◽  
pp. 02011
Author(s):  
Marina Vysotskaya ◽  
Anastasia Kurlykina ◽  
Artem Shiryaev ◽  
Anna Tkacheva ◽  
Dmitry Litovchenko
Keyword(s):  
Asphalt Concrete ◽  
Raw Material ◽  
Structural Defects ◽  
Concrete Pavements ◽  
Self Healing ◽  
Modified Bitumen ◽  
Concrete Mixtures ◽  
Bridge Structures ◽  
Bituminous Binders ◽  
Thermal Stability Of

Over the past few years, the research of the use of cast asphalt concrete mixtures in the upper layers of the coating of bridge structures has been actively carried out. The experience gained allows us to conclude that one of the most common effective ways to improve the durability and thermal stability of cast asphalt concrete pavements is the use of modified bituminous binders. The modified bitumen part of cast asphalt concrete acts as a medium capable of initiating the «self-healing» of the composite, independently eliminating structural defects. This study aims to research the rheological characteristics of modified bituminous binders. Bitumen grade BND 50/70 was used as a raw material in the study; the following types of additives were used as its modifiers: rubber modifier (RM), EVATHERM and SBS. The optimal concentrations of the proposed additives for modification allowing to achieve the effect of structuring the mastic component of cast asphalt concrete with insignificant increases in the temperatures of mixing and compaction of mixtures based on them have been revealed.

Crack growth behavior of aluminum alloy 6061 T651 under uniaxial and biaxial planar testing condition

2015 ◽  
Author(s):  
S. Henkel ◽  
E. Liebelt ◽  
H. Biermann ◽  
S. Ackermann
Keyword(s):  
Crack Growth ◽  
Tensile Load ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mode I ◽  
Proportional Loading ◽  
Center Crack ◽  
T Stress ◽  
Crack Tips ◽  
Alloy 6061

The crack growth behavior of the aluminum alloy 6061 T651 was investigated using cruciform specimens with a measurement area of 120 x 120 x 2 mm3 with two center crack configurations of the starting notch parallel to one of the loading axes and under an angle of 45°, respectively. For the case with crack direction in one of the loading axes the load ratio R = ?min / ?max as well as the force parallel to the crack direction (resulting in different T-stresses) were changed. Crack growth rate was studied under varying T-stress. Also the retardation after single overloads was determined for R = 0.1, R = 0.5 and R = 0.8. As a result a change in T-stress does not significantly affect crack growth rate on high R ratios (R = 0.5) for constant ?F loading. In case of lower R-ratios (R = 0.1) crack growth retardation was observed at presence of a static tensile load parallel to the crack growth direction due to higher influence of crack closure. Furthermore, such tensile load results in longer retardation periods after applying an overload at R = 0.1. Less pronounced overload retardation can be assumed with tensile force FX for R = 0.8 and 1.3 times overloads. Non proportional loading with a phase shift in time between the two axes of 45° and 90° results in a mixed mode situation (mode I / mode II) at the crack tip of a crack which is orientated under 45° to the loading axes. Mode I and mode II fractions change during every cycle. A phase change of 45° did not change crack growth significantly compared with proportional load. Crack branching occurred when changing from proportional loading to non-proportional 90° phase shifted loading. The two crack tips of the center crack under 45° divided in 4 crack tips under approximately 90° to the loading axes which were simultaneous propagating for more than 10 mm. Finally, two crack tips propagated faster than the remaining two. The stress intensity factors KI and KII as well as the T-stress where calculated by FEA (ABAQUS). For the 45° crack orientation and the non-proportional load case with 90° phase shift linear elastic FEA calculations show that there are time dependent rotating principal stress axes on the crack tip during one cycle. In the unnotched (uncracked) specimen there are fixed principal stress axes also in the phase shifted loading case. The configuration with 4 cracks has a significant higher ?KI than the configuration with two crack tips while ?KII is significantly lower. In addition uniaxial crack growth measurements were performed on SENB specimen in the size of 10 x 20 x 100 mm3 covering the threshold and Paris-region for loading ratios R = 0.1, 0.3, 0.5, 0.8.

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