Home About us Contact
|
Home About us Contact | ||
|
|
||
Mechanical Characterization (mechanical + characterization)
Kinds of Mechanical Characterization Selected AbstractsDEVELOPMENT OF A NEW EXPERIMENTAL TECHNIQUE FOR MECHANICAL CHARACTERIZATION OF FABRICEXPERIMENTAL TECHNIQUES, Issue 6 2008M. Issa First page of article [source] MECHANICAL CHARACTERIZATION OF SHREDDED WHEATJOURNAL OF TEXTURE STUDIES, Issue 5 2008J.B. LAURINDO ABSTRACT The purpose of the study was to evaluate a methodology for mechanical characterization of brittle foods with strong anisotropy. Spoon-sized pieces of three commercial brands of dry shredded wheat were chosen for the demonstration. They were compressed along their three principal axes, individually and grouped in the same orientation. The force-displacement curves in the three directions were all irregular and irreproducible but had discernible features characteristic of the specimen's orientation. When tested as constrained groups, these features could change, depending on the compression direction, reflecting on the contribution of the broken structure's remnants to the specimen's mechanical resistance. The assemblies' force-displacement curves were all smoother than those of the individual particles, a result of the "averaging effect." The overall force level could not be predicted from the number of pieces because of differences in the specimens' post-failure response to added deformation. The jaggedness of the normalized (dimensionless) force oscillations record was quantified in terms of an apparent Kolmogorov (fractal) dimension, determined with the box counting algorithm. Its value strongly depended on the smoothing model's goodness fit if the fit was too close, but not if it only captured the general shape of the force-displacement curve. PRACTICAL APPLICATIONS Despite the irregular and irreproducible mechanical signature of shredded wheat and the dependence on the specimens' orientation, it is still possible to characterize the products' mechanical properties in a way that distinguishes between their overall strength and brittleness. The described method could help to quantify textural differences between these and other brittle food products, and probably identify the conditions under which crunchiness would be maintained or lost. [source] Mechanical Characterization of Particulate Aluminum Foams,Strain-Rate, Density and Matrix Alloy versus Adhesive EffectsADVANCED ENGINEERING MATERIALS, Issue 7 2010Dirk Lehmhus Abstract The study evaluates mechanical properties of APM particulate aluminum foams built up from adhesively bonded Al foam spheres. Foams of matrix alloy AlSi10 are compared, with PM AlSi7 foams used as reference. The influence of density is studied both for quasi-static and dynamic compressive loading in a range from ,0.35 to 0.71,g,cm,3. The effect of varying the bonding agent is evaluated for a single density and both strain rate levels by replacing the standard, high-strength epoxy-based adhesive with a polyamide of greatly increased ductility. The result is a clear shift of fracture events to higher strain levels, as well as the introduction of a strain-rate dependency of strength. [source] Poly(ethylene oxide)- block -poly[2-(dimethylamino)ethyl methacrylate] as Strengthening Agent in Paper: Dynamic Mechanical CharacterizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2010Arja-Helena Vesterinen Abstract To enhance adhesion properties of PEO on wood fibers, block polymers of PEO and 2-(dimethylamino)ethyl methacrylate were synthesized. The polymers were further modified to obtain strongly cationic species. The resulting polymers were used as additives in paper sheets. Papers were studied by DMA in a controlled-humidity chamber. Addition of the PEO block co-polymers enhanced paper strength. The strength of the paper sheets was highest when polymer with molecular weight of 400,kg,·,mol,1 was used as an additive. Highly cationic block co-polymers increased moduli of paper sheets more than their weakly cationic analogs, which indicated strong interaction with fiber surfaces. Strength of the paper sheets decreased both with increased temperature and humidity. [source] Mechanical Characterization of Motor Proteins: A Molecular Dynamics ApproachMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7-8 2008Iuliana Aprodu Abstract A new approach, based on molecular dynamics, is presented to measure the mechanical properties of motor proteins, which are important for accomplishing their intracellular functions. Two different set-ups were designed to mimic the optical tweezers and surface force apparatus experiments. The results obtained show that the stiffness and elastic modulus of kinesin motor domain are 377 pN,·,nm,1 and 0.17 GPa, respectively, while the myosin motor domain is characterized by a stiffness of 271 pN,·,nm,1 and an elastic modulus of 0.26 GPa. These results suggest that the source of the very low stiffness detected for full-length molecules is located outside of the globular part of the proteins. [source] Synthesis and characterization of injectable bioadhesive hydrogels for nucleus pulposus replacement and repair of the damaged intervertebral discJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010J. Vernengo Abstract Bioadhesive polymers are natural or synthetic materials that can be used for soft tissue repair. The aim of this investigation was to develop an injectable, bioadhesive hydrogel with the potential to serve as a synthetic replacement for the nucleus pulposus of the intervertebral disc or as an annulus closure material. Branched copolymers of poly(N -isopropylacrylamide) (PNIPAAm) and poly(ethylene glycol) (PEG) were blended with poly(ethylene imine) (PEI). This three component injectable system can form a precipitated gel at physiological temperature due to the phase transition of PNIPAAm. The injection of glutaraldehyde into the gel core will adhere the implant to the surrounding tissues. 1H NMR results indicated the successful physical incorporation of PEI into the PNIPAAm-PEG network by blending. In addition, the covalent crosslinking between the amine functionalities on the PEI and the aldehyde functionalities on the glutaraldehyde was verified using FTIR difference spectroscopy. Mechanical characterization of these blends showed a significant increase (p < 0.05) in compressive modulus following glutaraldehyde injection. The in vitro bioadhesive force studies with porcine skin showed a significant increase (p < 0.05) in the mean maximum force of detachment for PNIPAAm-PEG/PEI gels when glutaraldehyde was injected into the gel core. The results of this study indicate that the reactivity between amines and aldehyde functionalities can be exploited to impart bioadhesive properties to PNIPAAm-PEG/PEI copolymers. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] Mechanical characterization of new glass fiber reinforced epoxy compositesPOLYMER COMPOSITES, Issue 2 2004D. Ratna Glass fiber reinforced plastic (GFRP) composites were made using CTPEGA [carboxyl terminated poly(ethylene glycol) adipate] modified epoxy as a matrix and characterized for their flexural properties, impact strength and interlaminar shear stress (ILSS). The volume fraction of glass was about 0.45 for all the composites. The concentration of CTPEGA in the matrix was varied gradually from 0 to 40 phr (parts per hundred parts of resin), to investigate the effect of CTPEGA concentration on the mechanical properties of the composites. It was found that the flexural strength and ILSS gradually decreases with increase in CTPEGA concentration. However, the impact strength of the composites increases up to 20 phr of CTPEGA concentration and decreases thereafter. Scanning electron microscope (SEM) analysis of the fracture surface indicates massive plastic deformation in modified epoxy based composites. Polym. Compos. 25:165,171, 2004. © 2004 Society of Plastics Engineers. [source] Physical and mechanical characterization and the influence of cyclic loading on the behaviour of nickel-titanium wires employed in the manufacture of rotary endodontic instrumentsINTERNATIONAL ENDODONTIC JOURNAL, Issue 11 2005M. G. A. Bahia Abstract Aim, To analyse the influence of cyclic loading on the mechanical behaviour of nickel-titanium (NiTi) wires employed in the manufacture of ProFile rotary endodontic instruments. Methodology, Nickel-titanium wires, 1.2 mm in diameter, taken from the production line of ProFile rotary endodontic instruments before the final machining step, were tensile-tested to rupture in the as-received condition and after 100 load,unload cycles in the superelastic plateau (4% elongation). The wires were characterized by X-ray energy-dispersive spectroscopy, X-ray diffraction and by differential scanning calorimetry and compared with new size 30, .06 taper ProFile instruments. The fracture surfaces of the wires were observed by scanning electron microscopy. Results, The mechanical properties of the as-received wires, their chemical composition, the phases present and their transformation temperatures were consistent with their final application. Only small changes, which decreased after the first few cycles, took place in the mechanical properties of the cycled wires. The stress at maximum load and the plastic strain at breakage remained the same, while the critical stress for inducing the superelastic behaviour, which is related to the restoring force of the endodontic instruments, decreased by approximately 27%. Conclusions, The mechanical behaviour of the NiTi wires was modified slightly by cyclic tensile loading in the superelastic plateau. As the changes tended towards stabilization, the clinical use of rotary NiTi ProFile instruments does not compromise their superelastic properties until they fracture by fatigue or torsional overload, or are otherwise discarded. [source] Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Luigi Torre Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Manufacturing, mechanical characterization, and in vitro performance of bioactive glass 13,93 fibersJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006E. Pirhonen Abstract Fibers were manufactured from the bioactive glass 13,93 by melt spinning. The fibers were further characterized by measuring their tensile and flexural strength, and their in vitro performance was characterized by immersing them in simulated body fluid, which analyzed changes in their mass, their flexural strength, and surface reactions. The strength of glass fibers is highly dependent on fiber diameter, test method, and possible surface flaws, for example, cracks due to abrasion. In this study, the thinnest fibers (diameter between 24 and 33 ,m) possessed the highest average tensile strength of 861 MPa. The flexural strength was initially 1353.5 MPa and it remained at that level for 2 weeks. The Weibull modulus for both tensile and flexural strength values was initially about 2.1. The flexural strength started to decrease and was only ,20% of the initial strength after 5 weeks. During the weeks 5,40, only a slight decrease was detected. The flexural modulus decreased steadily from 68 to 40 GPa during this period. The weight of the samples initially decreased due to leaching of ions and further started to increase due to precipitation of calcium phosphate on the fiber surfaces. The mass change of the bioactive glass fibers was dependent on the surface area rather than initial weight of the sample. The compositional analysis of the fiber surface after 24 h and 5 weeks immersion did confirm the initial leaching of ions and later the precipitation of a calcium phosphate layer on the bioactive glass 13,93 fiber surface in vitro. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] MECHANICAL CHARACTERIZATION OF SHREDDED WHEATJOURNAL OF TEXTURE STUDIES, Issue 5 2008J.B. LAURINDO ABSTRACT The purpose of the study was to evaluate a methodology for mechanical characterization of brittle foods with strong anisotropy. Spoon-sized pieces of three commercial brands of dry shredded wheat were chosen for the demonstration. They were compressed along their three principal axes, individually and grouped in the same orientation. The force-displacement curves in the three directions were all irregular and irreproducible but had discernible features characteristic of the specimen's orientation. When tested as constrained groups, these features could change, depending on the compression direction, reflecting on the contribution of the broken structure's remnants to the specimen's mechanical resistance. The assemblies' force-displacement curves were all smoother than those of the individual particles, a result of the "averaging effect." The overall force level could not be predicted from the number of pieces because of differences in the specimens' post-failure response to added deformation. The jaggedness of the normalized (dimensionless) force oscillations record was quantified in terms of an apparent Kolmogorov (fractal) dimension, determined with the box counting algorithm. Its value strongly depended on the smoothing model's goodness fit if the fit was too close, but not if it only captured the general shape of the force-displacement curve. PRACTICAL APPLICATIONS Despite the irregular and irreproducible mechanical signature of shredded wheat and the dependence on the specimens' orientation, it is still possible to characterize the products' mechanical properties in a way that distinguishes between their overall strength and brittleness. The described method could help to quantify textural differences between these and other brittle food products, and probably identify the conditions under which crunchiness would be maintained or lost. [source] Spectroscopic Investigations of Polymer NanocompositesMACROMOLECULAR SYMPOSIA, Issue 1 2005Liliane Bokobza The addition of an inorganic component to polymers leads to improvements in various physical and mechanical properties. Various examples on filled elastomeric networks will show that a mechanical characterization can be nicely combined with a spectroscopic investigation for a better understanding of the properties of the composite materials. [source] Hysteresis measurements and dynamic mechanical characterization of functionally graded natural rubber,carbon black compositesPOLYMER ENGINEERING & SCIENCE, Issue 5 2010S.S. Ahankari Functionally graded polymer composites (FGPCs) were prepared by construction based layering method employing natural rubber (NR) as a matrix and carbon black (CB) in graded form. CB particles were graded along the rectangular geometry polymer matrix comprising the variation of particle volume fraction along thickness direction. These FGPCs were characterized through hysteresis measurements and compared with uniformly dispersed polymeric composites (UDPCs) maintaining the same average amount of filler. Dynamic mechanical properties of these FGPCs and UDPCs were also compared. Dynamic mechanical characterization revealed that FGPCs show much higher storage modulus than the corresponding UDPCs for any given combination of stacking sequence. Loss tangent of FGPCs was also observed to be lesser when compared to UDPCs leading to less hysteretic losses followed by lesser heat buildup in the composite. Hysteresis measurements accorded with the results of dynamic mechanical characterization. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Use of carboxylated nitrile rubber and natural rubber blends as retreading compound for OTR tiresPOLYMER ENGINEERING & SCIENCE, Issue 12 2008Kaushik Pal Ore transportation is one of the important unit operations in a mineral industry. In this study, three raw rubber compounds are prepared in three different blend ratios, and four types of raw rubber samples of pure NR with silica reinforced has been collected from the different tire retreading industries. Blend properties largely depend on the blend ratio and on the blending technique. The improvement in the physical properties such as cure characteristics, mechanical characterization, cross-link density, FTIR, thermal characterization, SEM studies, and dynamic mechanical analysis has been studied in those samples. It has been found that retread rubber made with 80 phr XNBR and 20 phr NR has given the better results when compared with the other samples against all the characterization done. It is also seen that rubber made by the researchers are very good in tough, rigid and these are extremely able to withstand for using as a retread rubber for 35T dump trucks tire when compared with the retread rubber made by the tire retreading industries for different mines in India. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Thermal and mechanical characterization of epoxy resins toughened using preformed particlesPOLYMER INTERNATIONAL, Issue 8 2001J Day Abstract Preformed, multilayer particles have been used to toughen an epoxy resin. The particles were formed by emulsion polymerization and consist of alternate glassy and rubbery layers, the outer layer having glycidyl groups to give the possibility of chemical bonding of the particles in the cured resin. Two variants of this type of particle were used, termed GM(47/15) and GM(47/37); both types have an overall diameter of 0.5,µm, but the former have a thicker rubbery layer. For comparison, acrylic toughening particles (ATP) with no surface functionality and a liquid carboxyl-terminated butadiene,acrylonitrile (CTBN) rubber were used as toughening agents. The epoxy resin system consisted of a commercial diglycidyl ether of bisphenol A (Shell Epon 828) with diamino-3,5-diethyl toluene as hardener, two commercial sources of which were used, namely Ethacure-100 (Albemarle SA) and DX6509 (Shell Chemicals). These hardeners contain a mixture of two isomers, namely 2,6-diamino-3,5-diethyltoluene and 2,4-diamino-3,5-diethyltoluene Thermogravimetry in nitrogen shows that the preformed toughening particles begin to degrade at 230,°C, whereas the cured resin begins to degrade rapidly at 350,°C. Thus, even though the particles are less thermally stable than the cured resin, their degradation temperature is well above the glass transition temperature of the resin, and their use does not affect the thermal stability of the toughened materials at normal use temperatures. The performance of the toughening agents was compared using Ethacure-100 as the hardener. The GM(47/15) and GM(47/37) toughening particles gave rise to a greater toughening effect than the ATP and the CTBN. For example, the fracture energies were: 0.26,kJ,m,2 for the unmodified resin; 0.60,kJ,m,2 for the resin toughened with CTBN; and 0.69,kJ,m,2 for the resin toughened with the GM(47/15) particles. The ultimate tensile stress of the unmodified epoxy resin was 43,MPa, which increased to 55,MPa when 20,wt% of GM(47/15) toughening particles were added. The toughness of resins cured with the DX6509 hardener were superior to those obtained with the Ethacure-100 hardener, most probably due to DX6509 producing a less-highly-crosslinked network. This highlights the sensitivity of the toughening process to the hardener used, even for hardeners of a similar nature. © 2001 Society of Chemical Industry [source] Mechanical Response Analysis and Power Generation by Single-Cell StretchingCHEMPHYSCHEM, Issue 4 2005Alexandre Micoulet Dr. Abstract To harvest useful information about cell response due to mechanical perturbations under physiological conditions, a cantilever-based technique was designed, which allowed precise application of arbitrary forces or deformation histories on a single cell in vitro. Essential requirements for these investigations are a mechanism for applying an automated cell force and an induced-deformation detection system based on fiber-optical force sensing and closed loop control. The required mechanical stability of the setup can persist for several hours since mechanical drifts due to thermal gradients can be eliminated sufficiently (these gradients are caused by local heating of the cell observation chamber to 37,°C). During mechanical characterization, the cell is visualized with an optical microscope, which enables the simultaneous observation of cell shape and intracellular morphological changes. Either the cell elongation is observed as a reaction against a constant load or the cell force is measured as a response to constant deformation. Passive viscoelastic deformation and active cell response can be discriminated. The active power generated during contraction is in the range of Pmax=10,16Watts, which corresponds to 2500 ATP molecules,s,1at 10 kBT/molecule. The ratio of contractive to dissipative power is estimated to be in the range of 10,2. The highest forces supported by the cell suggest that about 104molecular motors must be involved in contraction. This indicates an energy-conversion efficiency of approximately 0.5. Our findings propose that, in addition to the recruitment of cell-contractile elements upon mechanical stimulation, the cell cytoskeleton becomes increasingly crosslinked in response to a mechanical pull. Quantitative stress,strain data, such as those presented here, may be employed to test physical models that describe cellular responses to mechanical stimuli. [source] EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION,ARCHAEOMETRY, Issue 1 2009H. WEIHE We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electron paramagnetic resonance spectra that supplement provenance determination. [source] | |||||||||||||