scholarly journals A Microstructural Study of Load Distribution in Cartilage: A Comparison of Stress Relaxation versus Creep Loading

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Ashvin Thambyah ◽  
V. M. van Heeswijk ◽  
C. C. van Donkelaar ◽  
Neil Broom
Keyword(s):  
Stress Relaxation ◽  
Load Distribution ◽  
Stress Release ◽  
Main Mode ◽  
Tissue Microstructure ◽  
Compressive Response ◽  
The Matrix ◽  
Microscopy Techniques ◽  
Creep Loading ◽  
Initial Mode

The compressive response of articular cartilage has been extensively investigated and most studies have focussed largely on the directly loaded matrix. However, especially in relation to the tissue microstructure, less is known about load distribution mechanisms operating outside the directly loaded region. We have addressed this issue by using channel indentation and DIC microscopy techniques that provide visualisation of the matrix microstructural response across the regions of both direct and nondirect loading. We hypothesise that, by comparing the microstructural response following stress relaxation and creep compression, new insights can be revealed concerning the complex mechanisms of load bearing. Our results indicate that, with stress relaxation, the initial mode of stress decay appears to primarily involve relaxation of the surface layer. In the creep loading protocol, the main mode of stress release is a lateral distribution of load via the mid matrix. While these two modes of stress redistribution have a complex relationship with the zonally differentiated tissue microstructure and the depth of strain, fourmechanostructuralmechanisms are proposed to describe succinctly the load responses observed.

scholarly journals An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4384
Author(s):  
Mohd Aidy Faizal Johari ◽  
Asmawan Mohd Sarman ◽  
Saiful Amri Mazlan ◽  
Ubaidillah U ◽  
Nur Azmah Nordin ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Shear Band ◽  
Shear Bands ◽  
Test Duration ◽  
Phase Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Matrix ◽  
Relaxation Stress ◽  
Band Deformation

Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.

Stress Relaxation Behavior of GH4169 Alloy

2020 ◽  
Vol 1013 ◽  
pp. 52-58
Author(s):  
Xu Dong Lu ◽  
Song Yi Shi ◽  
Bo Wen ◽  
Ya Wei Zhang ◽  
Jin Hui Du
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stress Relaxation ◽  
Initial Stress ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Transmission Electron ◽  
Microscopy Techniques ◽  
The Relationship ◽  
Gh4169 Alloy

The relaxation properties of GH4169 alloy were studied contrastively at temperatures ranging from 600 oC to 700 °C and initial stress ranging from 550 MPa to 850 MPa. The relationship between the microstructure and relaxation behavior was evaluated using transmission electron microscopy techniques. It was found that the relaxation limit and relaxation stability of the alloy decreased obviously with the increase of temperature. Further investigations show that the relaxation behavior is mainly depend on both precipitate characteristics and its interaction with dislocations. The alloy with higher strength lever has more excellent stress relaxation stability, because of the inhibition of a large number subgrains on dislocations motion.

scholarly journals Further Insight into the Depth-Dependent Microstructural Response of Cartilage to Compression Using a Channel Indentation Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Ashvin Thambyah ◽  
Neil D. Broom
Keyword(s):  
Stress Relaxation ◽  
Axial Strain ◽  
Compressive Strain ◽  
Microstructural Analysis ◽  
Elastic Response ◽  
Axial Deformation ◽  
Aspect Ratios ◽  
The Matrix ◽  
Tissue System ◽  
Relaxation Responses

Stress relaxation and structural analysis were used to investigate the zonally differentiated microstructural response to compression of the integrated cartilage-on-bone tissue system. Fifteen cartilage-on-bone samples were divided into three equal groups and their stress relaxation responses obtained at three different levels of axial compressive strain defined as low (~20%), medium (~40%) and high (~60%). All tests were performed using a channel indenter which included a central relief space designed to capture the response of the matrix adjacent to the directly loaded regions. On completion of each stress relaxation test and while maintaining the imposed axial strain, the samples were formalin fixed, decalcified, and then sectioned for microstructural analysis. Chondron aspect ratios were used to determine the extent of relative strain at different zonal depths. The stress relaxation response of cartilage to all three defined levels of axial strain displayed an initial highly viscous response followed by a significant elastic response. Chondron aspect ratio measurements showed that at the lowest level of compression, axial deformation was confined to the superficial cartilage layer, while in the medium and high axial strain samples the deformation extended into the midzone. The cells in the deep zone remained undeformed for all compression levels.

scholarly journals Preparation and Properties of Novel In Situ Composite Materials Based on Polyethylene-Polyamide Oriented Blends

2008 ◽  
Vol 587-588 ◽  
pp. 515-519 ◽  
Author(s):  
Nadya Dencheva ◽  
Maria Jovita Oliveira ◽  
Olga S. Carneiro ◽  
Teresa G. Nunes ◽  
Zlatan Z. Denchev
Keyword(s):  
Cold Drawing ◽  
Structural Data ◽  
Polyamide 6 ◽  
Polymer Processing ◽  
Mechanical Tests ◽  
X Ray Scattering ◽  
Nanostructured Polymer ◽  
The Matrix ◽  
Processing Techniques ◽  
Microscopy Techniques

The objective of this study is to manufacture and investigate novel nanostructured polymer composites (NPC) based on oriented blends of high-density polyethylene (HDPE) and polyamide 6 (PA6). Conventional polymer processing techniques are used for this purpose including extrusion blending, cold drawing and compression molding. Thus, various polymer blends are prepared comprising 10 and 20 wt% of PA6 and 0-10 wt% of a copolymeric compatibilizer. These blends are cold-drawn to high draw ratios and the oriented strands so produced are further compression molded at various temperatures between the melting points of HDPE and PA6. All NPC obtained are characterized by microscopy techniques, solid state NMR, mechanical tests and wide- and small-angle X-ray scattering from synchrotron. The mechanical and structural data of NPCs are discussed with relation with the polyamide fibrils’ orientation, as well as with the effect of compatibilizer at the matrix-fibrils interface.

Nano- and Microcrystal Investigations of Precipitates, Interfaces and Strain Fields in Ni-Ti-Nb by Various TEM Techniques

2013 ◽  
Vol 738-739 ◽  
pp. 65-71 ◽  
Author(s):  
Dominique Schryvers ◽  
Hui Shi ◽  
Gerardo T. Martinez ◽  
Sandra Van Aert ◽  
Jan Frenzel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Martensite Plate ◽  
Structural Features ◽  
Present Contribution ◽  
Cast Material ◽  
Strain Fields ◽  
Transformation Temperatures ◽  
The Matrix ◽  
Concentration Changes ◽  
Microscopy Techniques

In the present contribution several advanced electron microscopy techniques are employed in order to describe chemical and structural features of the nano- and microstructure of a Ni45.5Ti45.5Nb9 alloy. A line-up of Nb-rich nano-precipitates is found in the Ni-Ti-rich austenite of as-cast material. Concentration changes of the matrix after annealing are correlated with changes in the transformation temperatures. The formation of rows and plates of larger Nb-rich precipitates and particles is described. The interaction of a twinned martensite plate with a Nb-rich nano-precipitate is discussed and the substitution of Nb atoms on the Ti-sublattice in the matrix is confirmed.

scholarly journals Stress Relaxation Properties and Microscopic Deformation Structure in Bending of the C7025 and C7035 Alloy

2018 ◽  
Author(s):  
Xiangpeng Xiao ◽  
Hai Xu ◽  
Jian Huang ◽  
Junfeng Wang ◽  
Jianbo Zhang
Keyword(s):  
Stress Relaxation ◽  
Structural Changes ◽  
Relaxation Curve ◽  
Relaxation Properties ◽  
Limit Value ◽  
The Matrix ◽  
Long Time ◽  
Microscopic Deformation ◽  
Cantilever Bending ◽  
Two Stages

Stress relaxation tests in cantilever bending were performed on the C7025 and C7035 alloys at 298K and 393K，respectively. The effect of stress-relief treatments on stress relaxation properties was investigated. The structural changes associated with the stress relaxation process were examined using transmission electron microscope. The stress relaxation curve fits well to empirical formula σ*=[Kˊln(t+α0)+C]-n for stress relaxation. The curves can be split into two stages. The stress relax quickly in the first stage, slows down in the second stage, and tends to be a certain limit value after a long time. The curve and microstructure reveals that the C7035 alloy has a lower rate of stress relaxation and a higher anti-stress relaxation capacity than the C7025. The first reason is that the movement of vacancies required by spinodal decomposition is inhibited, and the quantity of cobalt -containing vacancies decreases dramatically in the C7035 alloy. The other reason is that the precipitated phases became uniformly diffused in the C7035 alloy. The precipitate phase uniformly distributes in the grain boundaries and the matrix, during the relaxed condition, and thus the dislocations moving is blocked by the precipitates.

scholarly journals Microstructural Evolution and Behavior of Deuterium in a Ferritic ODS 12 Cr Steel Annealed at Different Temperatures

2022 ◽  
Author(s):  
V. S. M. Pereira ◽  
S. Wang ◽  
T. Morgan ◽  
H. Schut ◽  
J. Sietsma
Keyword(s):  
Waiting Times ◽  
Thermal Desorption Spectroscopy ◽  
Average Diameter ◽  
Low Energy ◽  
Deuterium Plasma ◽  
Annealed Condition ◽  
The Matrix ◽  
Different Temperatures ◽  
And Behavior ◽  
Microscopy Techniques

AbstractIn the present work, an ODS 12 Cr steel was characterized using Electron Microscopy techniques, in an as-received condition and after annealing treatments between 773 K and 1573 K. Results show a complex microstructure, with the presence of fine Y–Ti–O nanoparticles dispersed in the matrix. After annealing at 1573 K, the average diameter of Y–Ti–O nanoparticles increases from ~ 4 to ~ 7 nm and partial recrystallization occurs. The trapping behavior of deuterium in the steel in its as-received state and annealed at 1573 K was investigated. Samples were exposed to low-energy deuterium plasma and analyzed with thermal desorption spectroscopy, after waiting times of 1 day and 25 days. The samples measured 1 day after exposure released a higher total amount of deuterium than the ones measured after 25 days. The effect of waiting time is explained by the release of deuterium, at 300 K, from sites with low activation energy for detrapping, Ed. In the as-received condition, part of the deuterium detrapped at 300 K was re-trapped by high-Ed sites. For the samples in the annealed condition, the redistribution of deuterium from low-Ed to high-Ed sites was not observed, but the total amount of deuterium released was higher.

Evolution of Carbides during Prestrain and Tempering

2021 ◽  
Vol 1016 ◽  
pp. 82-87
Author(s):  
Wen Hong Ding ◽  
Bo Jiang ◽  
Chao Lei Zhang ◽  
Ya Zheng Liu ◽  
Li Sun ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Dynamic Equilibrium ◽  
Energy State ◽  
High Strength ◽  
High Energy ◽  
Material Strength ◽  
Low Carbon ◽  
The Matrix ◽  
High Energy State ◽  
Two Stages

The effect of thermo-mechanical treatment on the microstructural evolution of low carbon micro-alloyed high strength steel was studied by combining prestrain with tempering (PST) in this paper. It was found that the prestrain causes the dislocation to plug up around the grain boundary and carbide, resulting in carbide boundary fragmentation. Moreover, it breaks the thermo-dynamic equilibrium between the matrix and carbide, induces the dissolution of carbon in the high energy state, and then changes the distribution of carbon in the matrix. In the subsequent tempering process, the precipitation regularity of carbide was changed, which promoted the precipitation carbide at low temperature. The influence of carbide precipitation on dislocation can be divided into two stages: the first stage was precipitation induced creep, which promoted stress relaxation; the second stage was precipitation pinning dislocation, which improved material strength and inhibited stress relaxation.

Assessment of the Mechanical Properties of Three Commercially Available Thermoplastic Aligner Materials used for Orthodontic Treatment

2021 ◽  
Vol 15 (2) ◽  
Author(s):  
Alok Ranjan ◽  
Anil Kumar Biradar ◽  
Ankita Patel ◽  
Vanessa Varghese ◽  
Ankita Pawar ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Yield Strength ◽  
Tooth Movement ◽  
Testing Machine ◽  
Bending Test ◽  
P Value ◽  
Stress Release ◽  
Relaxation Properties ◽  
Intergroup Comparison ◽  
Materials Used

Objectives: This studied aimed to measure the yield strength and stress relaxation properties of three commercially available thermoplastic aligner materials. Methods: The three different thermoplastics aligner materials Duran (Scheu, Iserlohn, Germany), Erkodur (Pfalzgrafenweiler, Erkodent, Germany) and Track (Forestadent, Germany) were selected. A three-point bending test was carried out via the universal testing machine to measure their yield strength and stress relaxation properties. An independent t- test was performed for intergroup comparison. P-value < 0.05 was set as the level of significance. Results: All the selected three polymers liberate a notable amount of stress during 24 hours. The highest stress release was observed in Duran i.e. 18.96 N/cm2 as compared to Erkodur, which was 13.96 N/cm2 and Track, which was 13.18 N/cm2. The yield strength of Duran was the highest (75.85 Mpa) compared to Track and Erkodur with the yield strength of 52.75 Mpa and 55.86 Mpa, respectively. Conclusions: Tooth movement is influenced by the composition of aligner material and its thickness. Duran had the highest stress release and yield strength. Stress released by different aligners exceeds around half of the initial stress value, which directly affects the orthodontic force application and subsequent tooth movement.

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