Influence of calcium ions on the mechanical properties of a model biofilm of mucoid Pseudomonas aeruginosa

2001 ◽  
Vol 43 (6) ◽  
pp. 49-57 ◽  
Author(s):  
V. Körstgens ◽  
H.-C. Flemming ◽  
J. Wingender ◽  
W. Borchard
Keyword(s):  
Mechanical Properties ◽  
Pseudomonas Aeruginosa ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Calcium Ions ◽  
Extracellular Polymeric Substances ◽  
Young's Modulus ◽  
Critical Concentration ◽  
Strain Diagram ◽  
Stress Strain

The mechanical properties of biofilms and in particular their mechanical strength is of great importance for both biofilm reactors and for the removal of undesired biofilms as in cases of biofouling and biocorrosion. By uniaxial compression measurements, it is possible to determine the apparent elastic or Young's modulus and the yield stress as parameters for mechanical stability. This was performed with a recently developed device, using model biofilms of mucoid strain Pseudomonas aeruginosa SG81. The biofilms were grown on membrane filters placed on nutrient agar medium with different concentrations of calcium ions. The compressive stress - strain behaviour up to failure was recorded at a compression speed of 1 μm s-1. The apparent Young's modulus, representing the stiffness of the biofilm, and the yield stress obtained from the stress - strain diagram were used for the description of mechanical properties of biofilms. A certain critical concentration of calcium ions was found where the Young's modulus of the P. aeruginosa biofilms increases strongly and subsequently remains constant for higher calcium concentrations. This behaviour is explained by the presence of calcium ions crosslinking alginate, which is the major component of the extracellular polymeric substances produced by the mucoid P. aeruginosa strain used in this investigation.

scholarly journals Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 529
Author(s):  
Chunzhi Du ◽  
Zhifan Li ◽  
Bingfei Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Shape Memory ◽  
Young’S Modulus ◽  
Residual Strain ◽  
Surface Effect ◽  
Young's Modulus ◽  
Strain Curve ◽  
Stress Strain ◽  
Strength Limit

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

scholarly journals Evaluating Mechanical Properties of Thin Layers using Nanoindentation and Finite-Element Modeling: Implanted Metals and Deposited Layers

1996 ◽  
Vol 438 ◽  
Author(s):  
J. A. Knapp ◽  
D. M. Follstaedt ◽  
J. C. Barbour ◽  
S. M. Myers ◽  
J. W. Ager ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Layer Thickness ◽  
Young's Modulus ◽  
Thin Layers ◽  
Element Modeling ◽  
Surface Modified

AbstractWe present a methodology based on finite-element modeling of nanoindentation data to extract reliable and accurate mechanical properties from thin, hard films and surface-modified layers on softer substrates. The method deduces the yield stress, Young's modulus, and hardness from indentations as deep as 50% of the layer thickness.

Effects of cross-sessional area and aspect ratio coupled with orientation on mechanical properties and deformation behavior of Cu nanowires

2021 ◽  
Author(s):  
Hui Cao ◽  
Wenke Chen ◽  
Zhiyuan Rui ◽  
Changfeng Yan
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Cu Nanowires ◽  
The Cross

Abstract Metal nanomaterials exhibit excellent mechanical properties compared with corresponding bulk materials and have potential applications in various areas. Despite a number of studies of the size effect on Cu nanowires mechanical properties with square cross-sectional, investigations of them in rectangular cross-sectional with various sizes at constant volume are rare, and lack of multifactor coupling effect on mechanical properties and quantitative investigation. In this work, the dependence of mechanical properties and deformation mechanisms of Cu nanowires/nanoplates under tension on cross-sessional area, aspect ratio of cross-sectional coupled with orientation were investigated using molecular dynamics simulations and the semi-empirical expressions related to mechanical properties were proposed. The simulation results show that the Young’s modulus and the yield stress sharply increase with the aspect ratio except for the <110>{110}{001} Cu nanowires/nanoplates at the same cross-sectional area. And the Young’s modulus increases while the yield stress decreases with the cross-sectional area of Cu nanowires. However, both of them increase with the cross-sectional area of Cu nanoplates. Besides, the Young’s modulus increases with the cross-sectional area at all the orientations. The yield stress shows a mildly downward trend except for the <111> Cu nanowires with increased cross-sectional area. For the Cu nanowires with a small cross-sectional area, the surface force increases with the aspect ratio. In contrast, it decreases with the aspect ratio increase at a large cross-sectional area. At the cross-sectional area of 13.068 nm2, the surface force decreases with the aspect ratio of the <110> Cu nanowires while it increases at other orientations. The surface force is a linearly decreasing function of the cross-sectional area at different orientations. Quantitative studies show that Young’s modulus and yield stress to the aspect ratio of the Cu nanowires satisfy exponent relationship. In addition, the main deformation mechanism of Cu nanowires is the nucleation and propagation of partial dislocations while it is the twinning-dominated reorientation for Cu nanoplates.

Uniaxial Mechanical Properties of Sandstone under Cyclic of Drying and Wetting

2011 ◽  
Vol 243-249 ◽  
pp. 2310-2313 ◽  
Author(s):  
Hua Yan Yao ◽  
Zhen Hua Zhang ◽  
Zhao Hui Zhu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Test Results ◽  
Stress Strain ◽  
Deformation And Failure ◽  
Deformation Behaviors ◽  
Uniaxial Strength

Water is an important factor that influences the mechanical properties of rock. Uniaxial compressive experiments have been carried out on sandstone under different cyclic times of drying and wetting. The corresponding complete stress-strain curves are obtained, and characteristics of deformation and failure are analyzed. Test results show that when sandstone samples are submitted to cyclic of drying and wetting, the uniaxial strength and Young's modulus of sandstone obviously decrease. Then, the improved Duncan constitutive model is developed, which can do better in describing sample’s deformation behaviors subject to different cyclic times of drying and wetting. Introduction

High Temperature Mechanical Properties of Ni-YSZ Cermets for SOFC Anode

2010 ◽  
Author(s):  
Fumitada Iguchi ◽  
Hiromichi Kitahara ◽  
Hiroo Yugami
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Flexural Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Strain Diagram ◽  
Thermal Cycles ◽  
High Temperature Mechanical Properties ◽  
Sofc Anode ◽  
The Difference

The mechanical properties of Ni-YSZ cermets at high temperature in reduction atmosphere were evaluated by the four points bending method. We studied the influences of reduction and thermal cycles, i.e. a cycle from R.T. to 800°C, to flexural strength and Young’s modulus. The flexural strength of Ni-YSZ at room temperature was lower than that of NiO-YSZ by about 10 to 20% mainly caused by the increment of porosity. But, the flexural strength of Ni-YSZ at 800°C was drastically decreased by an half of that at R.T. In addition, the stress–strain diagram of Ni-YSZ at 800°C indicated that it showed weak ductility. The maximum observed strain was over 0.5% at 30MPa. On the contrary, NiO-YSZ showed only brittlely at 800°C. The difference was caused by Ni metal in the Ni-YSZ cermets. Therefore, it was expected that Ni-YSZ is easily deformed in operation, though residual stress between an anode and an electrolyte was low. The influence of thermal cycles to flexural strength and Young’s modulus was not observed clearly. At the same time, the differences of microstructure were not observed. Therefore, it was concluded that the cycle does not change mechanical properties significantly.

The Mechanical Properties of Electroplated Cu Thin Films Measured by means of the Bulge Test Technique

2001 ◽  
Vol 695 ◽  
Author(s):  
Yong Xiang ◽  
Xi Chen ◽  
Joost J. Vlassak
Keyword(s):  
Mechanical Properties ◽  
Film Thickness ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Bulge Test ◽  
X Ray Diffraction ◽  
Test Technique ◽  
Cu Films ◽  
Analytical Formulae

ABSTRACTThe mechanical properties of freestanding electroplated Cu films were determined by measuring the deflection of Si-framed, pressurized membranes. The films were deformed under plane-strain conditions. The pressure-deflection data are converted into stress-strain curves by means of simple analytical formulae. The microstructure of the Cu films was characterized using scanning electron microscopy and x-ray diffraction. The yield stress, Young's modulus, and residual stress were determined as a function of film thickness and microstructure. Both yield stress and Young's modulus increase with decreasing film thickness and correlate well with changes in the microstructure and texture of the films.

Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures

2010 ◽  
Vol 638-642 ◽  
pp. 3793-3798
Author(s):  
Wolfgang H. Müller ◽  
Holger Worrack ◽  
Jens Sterthaus
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Linear Optimization ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Non Linear

The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.

Molecular dynamics simulations of the effect of temperature and strain rate on the plastic deformation of body centred cubic iron nanowires

2021 ◽  
pp. 1-19
Author(s):  
Qian Wu ◽  
Yong Wang ◽  
Tao Han ◽  
Hongtao Wang ◽  
Laihui Han ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Strain Rate ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Strain Curve ◽  
Dislocation Slip ◽  
Stress Strain Curve ◽  
Stress Strain

Abstract The tensile tests of BCC Fe nanowires were simulated through molecular dynamics methods. The temperature and strain rate effects on the mechanical properties as well as the orientation-dependent plastic deformation mechanism were analyzed. For [001]-oriented BCC Fe nanowires, as the temperature increased, the yield stress and Young's modulus decreased. While the yield stress and Young's modulus increased as the strain rate increased. With the increase of temperature, when the temperature was less than 400 K, the twin propagation stress decreased dramatically, and then tended to reach a saturation value at higher temperatures. Under different temperatures and strain rates, the [001]-oriented Fe nanowires all deformed by twinning. The oscillation stage in the stress-strain curve corresponds to the process from the nucleation of the twin to the reorientation of the nanowire. For [110]-oriented Fe nanowires, the plastic deformation is dominated by dislocation slip. The independent events such as the nucleation, slip, and annihilation of dislocations are the causes of the unsteady fluctuations in the stress-strain curve. The Fe nanowires eventually undergo shear damage along the dominant slip surface.

Interfacial Effect on Mechanical Properties of Polypropylene Ternary Nanocomposites

2018 ◽  
Vol 913 ◽  
pp. 564-570 ◽  
Author(s):  
Wei Wang ◽  
Wei Wang ◽  
Dong Lv ◽  
Jing Shen Wu
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Vital Role ◽  
Enhancement Effect ◽  
Weak Interface ◽  
The Matrix ◽  
Grafted Nanoparticles ◽  
The Impact

The matrix/filler interface plays a vital role in mechanical properties of polypropylene (PP)/rigid nanoparticles composites. In general, the use of spherical stearic acid modified CaCO3 (SA-CaCO3) can induce a weak interfacewhich facilitatesparticle debonding from the matrix under loading and reduces plastic resistance, enhancing the toughness of nanocomposites, while the use of polymer-grafted nanoparticles (PGS) can improve the Young’s modulus and yield stress because of strong interfacial binding between particle and matrix. With the objective to simultaneously improve the modulus, yield stress and toughness, the ternary nanocomposites, PP/PGS/CaCO3 (PPSC), were prepared and the morphology, crystallization, and mechanical behavior were investigated and compared to their binary nanocomposites. The results show that Young’s modulus is enhanced as the particle loading, and the yield stress is balanced by two interactions, i.e. the decreasing effect of the weak interface and the enhancement effect of the strong interface. The impact strength of the ternary nanocomposites shows insignificant improvement compared with neat PP, which is attributed to the brittle effect of the weak interface in the particle cluster of SA-CaCO3 and PGS.

scholarly journals Simultaneous Modeling of Young’s Modulus, Yield Stress, and Rupture Strain of Gelatin/Cellulose Acetate Microfibrous/Nanofibrous Scaffolds Using RSM

2021 ◽  
Vol 9 ◽  
Author(s):  
Alireza Barazesh ◽  
Mahdi Navidbakhsh ◽  
Ali Abouei Mehrizi ◽  
Mojtaba Koosha ◽  
Sajad Razavi Bazaz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cellulose Acetate ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Mechanical Characteristics ◽  
Rotation Speed ◽  
Young's Modulus ◽  
Structural Parameters ◽  
Weight Ratio ◽  
Wide Range

Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing various types of biopolymers, flexible structures, and also the diversity of output properties. Mechanical properties are one of the major components of scaffold design to fabricate an efficacious artificial substitute for the natural extracellular matrix. Additionally, fiber orientations, as one of the scaffold structural parameters, could play a crucial role in the application of fabricated fibrous scaffolds. In this study, gelatin was used as a highly biocompatible polymer in blend with cellulose acetate (CA), a polysaccharide, to enhance the achievable range of mechanical characteristics to fabricated fibrous electrospun scaffolds. By altering input variables, such as polymers concentration, weight ratio, and mandrel rotation speed, scaffolds with various mechanical and morphological properties could be achieved. As expected, the electrospun scaffold with a higher mandrel rotation speed shows higher fiber alignment. A wide range of mechanical properties were gained through different values of polymer ratio and total concentration. A general improvement in mechanical strength was observed by increasing the concentration and CA content in the solution, but contradictory effects, such as high viscosity in more concentrated solutions, influenced the mechanical characteristics as well. A response surface method was applied on experimental results in order to describe a continuous variation of Young’s modulus, yield stress, and strain at rupture. A full quadratic version of equations with the 95% confidence level was applied for the response modeling. This model would be an aid for engineers to adjust mandrel rotation speed, solution concentration, and gelatin/CA ratio to achieve desired mechanical and structural properties.

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