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Displacement Curves (displacement + curve)
Selected AbstractsDATA ANALYSIS OF PENETROMETRIC FORCE/DISPLACEMENT CURVES FOR THE CHARACTERIZATION OF WHOLE APPLE FRUITSJOURNAL OF TEXTURE STUDIES, Issue 4 2005C. CAMPS ABSTRACT The objective of the present study was to compare two chemometric approaches for characterizing the rheological properties of fruits from puncture test force/displacement curves. The first approach (parameter approach) computed six texture parameters from the curves, which were supposed to be representative of skin hardness, fruit deformation before skin rupture, flesh firmness and mechanical work needed to penetrate the fruit. The second approach (whole curve approach) used the whole digitized curve (300 data points) in further data processing. Two experimental studies were compared: first, the variability of the rheological parameters of five apple cultivars; second, the rheological variability that was characterized as a function of storage conditions. For both approaches, factorial discriminant analysis was applied to discriminate the fruits based on the measured rheological properties. The qualitative groups in factorial discriminant analysis were either the apple cultivar or the storage conditions (days and temperatures of storage). The tests were carried out using cross-validation procedures, making it possible to compute the number of fruits correctly identified. Thus the percentage of correct identification was 92% and 87% for using the parameter and the whole curve approaches, respectively. The discrimination of storage duration was less accurate for both approaches giving about 50% correct identifications. Comparison of the percentage of correct classifications based on the whole curve and the parameter approaches showed that the six computed parameters gave a good summary of the information present in the curve. The whole curve approach showed that some additional information, not present in the six parameters, may be appropriate for a complete description of the fruit rheology. [source] The impact of loads on standard diameter, small diameter and mini implants: a comparative laboratory studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2008Simon Rupert Allum Abstract Objectives: While caution in the use of small-diameter (,3.5 mm) implants has been advocated in view of an increased risk of fatigue fracture under clinical loading conditions, a variety of implant designs with diameters <3 mm are currently offered in the market for reconstructions including fixed restorations. There is an absence of reported laboratory studies and randomized-controlled clinical trials to demonstrate clinical efficacy for implant designs with small diameters. This laboratory study aimed to provide comparative data on the mechanical performance of a number of narrow commercially marketed implants. Materials and methods: Implants of varying designs were investigated under a standardized test set-up similar to that recommended for standardized ISO laboratory testing. Implant assemblies were mounted in acrylic blocks supporting laboratory cast crowns and subjected to 30° off-axis loading on an LRX Tensometer. Continuous output data were collected using Nexygen software. Results: Load/displacement curves demonstrated good grouping of samples for each design with elastic deformation up to a point of failure approximating the maximum load value for each sample. The maximum loads for Straumann (control) implants were 989 N (±107 N) for the 4.1 mm RN design, and 619 N (±50 N) for the 3.3 mm RN implant (an implant known to have a risk of fracture in clinical use). Values for mini implants were recorded as 261 N (±31 N) for the HiTec 2.4 mm implant, 237 N (±37 N) for the Osteocare 2.8 mm mini and 147 N (±25 N) for the Osteocare mini design. Other implant designs were also tested. Conclusions: The diameters of the commercially available implants tested demonstrated a major impact on their ability to withstand load, with those below 3 mm diameter yielding results significantly below a value representing a risk of fracture in clinical practice. The results therefore advocate caution when considering the applicability of implants ,3 mm diameter. Standardized fatigue testing is recommended for all commercially available implants. [source] Gradient plasticity modelling of strain localization in granular materialsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2004O. Al Hattamleh Abstract The flow stress in the yield surface of plastic constitutive equation is modified with a higher order gradient term of the effective plastic strain to model the effect of inhomogeneous deformation in granular materials. The gradient constitutive model has been incorporated into the finite element code ABAQUS and used to simulate biaxial shear tests on dry sand. It is shown that the shape of the post-peak segment of the load displacement curve predicted by the numerical analysis is dependent on the mesh size when gradient term is not used. Use of an appropriate gradient coefficient is shown to correct this and predict a unique shape of the load displacement curve regardless of the mesh size. The gradient coefficient required turns out to be approximately inversely proportional to the mesh elemental area. Use of the strain gradient term is found to diffuse the concentration of plastic strains within shear band resulting in its consistent width. The coefficient of the higher gradient term appears as a function of the grain size, the mean confining stress, and the plastic softening modulus. Copyright © 2004 John Wiley & Sons, Ltd. [source] Calendar year age estimates of Allerød,Younger Dryas sea-level oscillations at Os, western NorwayJOURNAL OF QUATERNARY SCIENCE, Issue 5 2004Øystein S. Lohne Abstract A detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea-level rise was more than 9,m in an area which subsequently experienced an emergence of almost 60,m. The sea-level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time-scale by 14C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post-glacial rise in Betula (birch) pollen). The sea-level curve demonstrates that the Younger Dryas transgression started close to the Allerød,Younger Dryas transition and that the high stand was reached only 200,yr before the Younger Dryas,Holocene boundary. The sea level remained at the high stand for about 300,yr and 100,yr into Holocene it started to fall rapidly. The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice-sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea-level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød,Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd. [source] Analysis of laser/IR-assisted microembossingPOLYMER ENGINEERING & SCIENCE, Issue 5 2005Chunmeng Lu To shorten the cycle time in conventional hot embossing, an infrared laser (laser/IR)-assisted microembossing process was investigated in this study. Since the laser/IR heats the substrate rapidly and locally, the heating and cooling time can be substantially reduced. Two different modes of IR embossing were tested. In one case, the polymer substrate was the IR-transparent poly(methyl methacrylate) (PMMA) and a carbon black-filled epoxy mold was used. In the second case, the polymer substrate was an IR-absorbent PMMA, and an IR transparent epoxy mold was used. The experimental results showed that both a shorter cycle time and good replication accuracy could be achieved. A commercially available finite element (FEM) code, DEFORMÔ, was used for process simulation. The relationship between the penetration of radiation energy flux from the laser/IR heating source and temperature distribution inside the polymer substrate was considered in the simulation. The flow pattern observed in the experiments agreed well with the numerical simulation. However, the displacement curve showed a discrepancy. POLYM. ENG. SCI., 45:661,668, 2005. © 2005 Society of Plastics Engineers [source] The modelling of anchors using the material point methodINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2005C. J. Coetzee Abstract The ultimate capacity of anchors is determined using the material point method (MPM). MPM is a so-called meshless method capable of modelling large displacements, deformations and contact between different bodies. A short introduction to MPM is given and the derivation of the discrete governing equations. The analysis of a vertically loaded anchor and one loaded at 45° is presented. The load,displacement curves are compared to that obtained from experiments and the effect of soil stiffness and anchor roughness is investigated. The results of the vertically loaded anchor are also compared to an analytical solution. The displacement of the soil surface above the anchor was measured and compared to the numerical predictions. Convergence with mesh refinement is demonstrated and the effect of mesh size and dilatancy angle on the shear band width and orientation is indicated. The results show that MPM can model anchor pull out successfully. No special interface elements are needed to model the anchor,soil interface and the predicted ultimate capacities were within 10% of the measured values. Copyright © 2005 John Wiley & Sons, Ltd. [source] Comparison of non-local and polar modelling of softening in hypoplasticityINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2004Th. Maier Abstract The paper deals with the comparison of a non-local and a polar (Cosserat) hypoplastic model. The hypoplastic constitutive law in the version of von Wolffersdorff is chosen as local reference model. For the comparison the results of biaxial tests on dense Hostun Rf sand are predicted with both enhanced models. The comparison is based on a strict separation of input data from triaxial- and oedometer tests and output data from biaxial tests. The comparison is drawn in terms of the shear band width, the load,displacement curves and the influence of the pressure level. Finally, the non-local and the polar hypoplastic model are applied on the strip foundation problem. Copyright © 2004 John Wiley & Sons, Ltd. [source] Three-dimensional analysis of single pile response to lateral soil movementsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2002J. L. Pan Abstract Three-dimensional finite element analysis was carried out to investigate the behaviour of single piles subjected to lateral soil movements and to determine the ultimate soil pressures acting along the pile shaft. The finite element analysis program ABAQUS was used for the analysis and run on a SUN Workstation. The von Mises constitutive model was employed to model the non-linear stress,strain soil behaviour. The pile was assumed to have linear elastic behaviour. This was considered to be a reasonable approximation, as the maximum stress developed in the pile did not exceed the yield stress of the concrete pile. The length of the pile is 15 m, the width of the square pile is 1 m. The three-dimensional finite element mesh used in the analysis was optimized taking into account the computing capacity limitations of the Sun Workstation. The computed ultimate soil pressures agreed well with those from the literature. The shapes of the soil pressure versus soil movement curves and the soil pressure versus the relative soil,pile displacement curves as well as the magnitude of the relative soil,pile displacement to mobilize the ultimate soil pressures were in reasonable agreement with those reported by other researchers. Copyright © 2002 John Wiley & Sons, Ltd. [source] Vibration of a space arc subject to a critical dynamic loadINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2005Lazarus Teneketzis Tenek Abstract The present study concerns the dynamic behaviour of a space arc subject to a midarc vertical buckling load dynamically applied. The arc is discretized with a set of three-dimensional beam finite elements and the non-linear dynamic equation (large displacements) is solved by means of an unconditionally stable time-dependent scheme over time. The vertical excitation gives rise to a very fast and erratic horizontal wave as the structure begins to vibrate in all directions. This horizontal wave has chaotic characteristics as its attractor indicates. Time,displacement curves are obtained for all components of the midarc point. Although the time algorithm was executed here for 2000 time steps, simulation over longer periods of time can reveal the vibration characteristics and even simulate structural failure under the imposed dynamic buckling load for the space arc structure. Copyright © 2004 John Wiley & Sons, Ltd. [source] Elastic Indentation Response of Float Glass SurfacesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Andrea M. Muller Instrumented Hertzian indentation was used to evaluate the reduced elastic modulus and cone-crack initiation forces for the as-received surfaces of commercial float glasses. Custom-built indentation equipment with the capability of acoustic emission detection was used to monitor continuously the load and depth of penetration at the microscopic scale for forces up to 1 kN. Equipment verification was performed using a reference material, GE 124. The air and tin surfaces of commercial soda,lime,silica and borosilicate float glasses were tested to determine any difference in indentation response for the elastic and fracture behavior of as-received surfaces. Information obtained from the analysis of the load,displacement curves and from the visual inspection of the indentation sites was used to determine the elastic modulus, and the conditions for the onset of cone cracking as a function of surface roughness. The reduced modulus results were verified using additional equipment that allowed the in situ observation of the contact area during loading and unloading. The results showed that there was no difference in the reduced modulus data for the air and tin surfaces for the range of surface displacements studied. The same conclusions were found for cone-cracking loads on as-received surfaces but tests on abraded surfaces showed that the tin surfaces had slightly more resistance to cone cracking than the air surfaces. [source] Toughened Oxide Composites Based on Porous Alumina-Platelet InterphasesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Sang-Jin Lee A novel mechanism for debonding at a weak interphase in an all-oxide composite is introduced. This methodology involves the use of alumina platelets that have a diameter of 10,15 or 5,10 ,m and a thickness of 1 ,m. The platelets induce constrained sintering of the ceramic powder, which results in permanent porosity. For room-temperature properties, only minor additions (0,3 vol%) of matrix powder yield sufficiently weak debonding interphases. The platelets lie in random, three-dimensional orientations and provide a debonding mechanism that is independent of temperature, in chemically compatible matrixes. Laminated composites with two types of matrixes,mullite and alumina,have been fabricated with modified fibrous monoliths of alumina in a triple-layer "core/interphase/matrix" arrangement. In the laminated systems, the intimate mixing of strong versus tough microstructures has been tailored by alternating various matrix:interphase thickness ratios. Preliminary load,displacement curves clearly demonstrate characteristics of "graceful failure" and notable improvements in the work of fracture. Scanning electron microscopic observation of the crack paths confirms the viability of platelets for producing permanently porous, debondable interphases at elevated temperatures in air. [source] Preparation and Characterization of Trialkoxysilane-Containing Acrylic Resin/Alumina Hybrid MaterialsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2006Mingqi Li Abstract Summary: In the present study (3-methacryloxypropyl)trimethoxysilane (MPMS) containing acrylic resin/alumina hybrid materials with various alumina contents were prepared. The effects of ethylacetoacetate (EAA) content, catalyst type, and water content during sol,gel process for alumina sols on the microstructure and properties of the hybrid materials were investigated by SAXS, AFM, DSC, TGA, and nano-indentation tester, respectively. It was found that the hybrid materials exhibited a homogeneity and the alumina phase of the hybrids had mass fractal dimension and open structure. The thermal and mechanical properties of the hybrid materials were obviously improved when alumina was incorporated. The EAA contents, catalyst type, and water content during sol,gel process for alumina sols had obvious effects on the microstructure and properties of the hybrid materials. Typical load,displacement curves of the pure acrylic resin and hybrid materials with increasing alumina content. [source] Blepharokymographic Analysis of Eyelid Motion in Bell's PalsyTHE LARYNGOSCOPE, Issue 2 2007Seung-Ho Choi MD Abstract Objective: To present characteristics of eyelid motion measured by blepharokymography in Bell's palsy patients and to discuss possible roles and limitations of blepharokymography. Study Design. Retrospective analysis. Methods: The study included 72 patients with Bell's palsy who presented to the Department of Otolaryngology at Asan Medical Center, Seoul, Korea, between April 2002 and March 2005, and who underwent both electroneuronography and blepharokymography. Parameters of eyelid motion were measured using revised blepharokymography. Correlations between blepharokymography and electroneuronography or House-Brackmann grade were examined by Spearman rank correlation and Kendall's ,-b correlation, respectively. Results: Compared with the normal side, all parameters of eyelid motion except opening time were decreased on the palsy side, with peak closing velocity showing the greatest difference (40.2%). On average, paralytic eyelids moved down 6.5 mm in 277 ms with a peak velocity of 55.4 mm/s, whereas normal eyelids moved down 9.7 mm in 214 ms, with a peak velocity of 142.6 mm/s. Subtle paralytic eyelid motion or "lid lag" could be objectively documented by blepharokymography to have longer and gentler downward slopes in displacement curves. Most blepharokymographic parameters correlated with ocular electroneuronography and House-Brackmann grade. Conclusions: Slow or incomplete closure of paralytic eyelids can be graphically and numerically analyzed by blepharokymography. Blepharokymography may be useful for evaluating status, predicting prognosis, and assessing effects of rehabilitative procedures, including gold weight implants in patients with facial palsy. [source] DATA ANALYSIS OF PENETROMETRIC FORCE/DISPLACEMENT CURVES FOR THE CHARACTERIZATION OF WHOLE APPLE FRUITSJOURNAL OF TEXTURE STUDIES, Issue 4 2005C. CAMPS ABSTRACT The objective of the present study was to compare two chemometric approaches for characterizing the rheological properties of fruits from puncture test force/displacement curves. The first approach (parameter approach) computed six texture parameters from the curves, which were supposed to be representative of skin hardness, fruit deformation before skin rupture, flesh firmness and mechanical work needed to penetrate the fruit. The second approach (whole curve approach) used the whole digitized curve (300 data points) in further data processing. Two experimental studies were compared: first, the variability of the rheological parameters of five apple cultivars; second, the rheological variability that was characterized as a function of storage conditions. For both approaches, factorial discriminant analysis was applied to discriminate the fruits based on the measured rheological properties. The qualitative groups in factorial discriminant analysis were either the apple cultivar or the storage conditions (days and temperatures of storage). The tests were carried out using cross-validation procedures, making it possible to compute the number of fruits correctly identified. Thus the percentage of correct identification was 92% and 87% for using the parameter and the whole curve approaches, respectively. The discrimination of storage duration was less accurate for both approaches giving about 50% correct identifications. Comparison of the percentage of correct classifications based on the whole curve and the parameter approaches showed that the six computed parameters gave a good summary of the information present in the curve. The whole curve approach showed that some additional information, not present in the six parameters, may be appropriate for a complete description of the fruit rheology. [source] Factorial designed experiment to study the effects of excipients on the mechanical properties of pelletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2006Abraham B. Bashaiwoldu The aim of this work was to determine the effects of formulation factors on the mechanical properties of pellets produced by the process of extrusion and spheronisation. A range of properties from a simple fracture load to detailed load/displacement curves were used to study the effects of the levels of lactose monohydrate and glyceryl monostearate on the mechanical properties of pellets in terms of their surface tensile strength, pellet deformability and linear strain. A series of independent 22 -factorial designs were employed to establish the relationships between composition of the formulations and pellet properties, whereby the concept of an excess variable was explored. It was found that the spheronisation aid used, microcrystalline cellulose, is the domineering factor in most mechanical properties studied, except for the surface tensile strength, which decreased significantly with an increase in glyceryl monostearate concentration. The change in binder liquid from water to a water/ethanol mixture further changed the behaviour of the systems significantly. The assumption of an excess variable being less critical for the statistical outcome of a factorial experiment has not been found feasible for the systems studied. [source] | ||||||||||||||||