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Different Mechanical Properties (different + mechanical_property)
Selected AbstractsInfluences of the Process Chain on the Fatigue Behavior of Samples with Tension Screw Geometry,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marcus Klein To analyze the influence of the material batch, the structure of the manufacturing process chain, and the process parameters, four different material batches of the quenched and tempered steel SAE 4140 were used to manufacture samples with tension screw geometry. Five different, manufacturing process chains, consisting of the process steps heat treatment, turning, and grinding, were applied. After selected process steps, light and SEM micrographs as well as fatigue experiments were performed. The process itself as well as the process parameters influences the properties of the surface layers and the fatigue behavior in a characteristic manner. For example the variation of the feed rate and cutting speed in the hard-turning process leads to significantly different mechanical properties of the surface layers and residual stress states, which could be correlated with the fatigue behavior. The cyclic deformation behavior of the investigated components can be benchmarked equivalently with stress,strain hysteresis as well as high precision temperature and electrical resistance measurements. The temperature and electrical resistance measurements are suitable for component applications and provide an enormous advantage of information about the fatigue behavior. The temperature changes of the failed areas of the samples with tension screw geometry were significantly higher, a reliable identification of endangered areas is thereby possible. A new test procedure, developed at the Institute of Materials Science and Engineering of the University of Kaiserslautern, with inserted load-free-states during constant amplitude loading, provides the opportunity to detect proceeding fatigue damage in components during inspections. [source] Evolution and development of the primate limb skeletonEVOLUTIONARY ANTHROPOLOGY, Issue 3 2002Chi-Hua Chiu Abstract The order Primates is composed of many closely related lineages, each having a relatively well established phylogeny supported by both the fossil record and molecular data.1 Primate evolution is characterized by a series of adaptive radiations beginning early in the Cenozoic era. Studies of these radiations have uncovered two major trends. One is that substantial amounts of morphological diversity have been produced over short periods of evolutionary time.2 The other is that consistent and repeated patterns (variational tendencies3) are detected. Taxa within clades, such as the strepsirrhines of Madagascar and the platyrrhines of the Neotropics, have diversified in body size, substrate preference, and diet.2, 4,6 The diversification of adaptive strategies within such clades is accompanied by repeated patterns of change in cheiridial proportions7, 8 (Fig. 1) and tooth-cusp morphology.9 There are obvious adaptive, natural-selection based explanations for these patterns. The hands and feet are in direct contact with a substrate, so their form would be expected to reflect substrate preference, whereas tooth shape is related directly to the functional demands of masticating foods having different mechanical properties. What remains unclear, however, is the role of developmental and genetic processes that underlie the evolutionary diversity of the primate body plan. Are variational tendencies a signature of constraints in developmental pathways? What is the genetic basis for similar morphological transformations among closely related species? These are a sampling of the types of questions we believe can be addressed by future research integrating evidence from paleontology, comparative morphology, and developmental genetics. [source] Tribological properties of bismaleimide composites with surface-modified SiO2 nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Hongxia Yan Abstract In this article, the surface of SiO2 nanoparticles was modified by silane coupling agent N -(2-aminoethyl)-,-aminopropylmethyl dimethoxy silane. The bismaleimide nanocomposites with surface-modified SiO2 nanoparticles or unmodified SiO2 nanoparticles were prepared by the same casting method. The tribological performance of the nanocomposites was studied on an M-200 friction and wear tester. The results indicated that the addition of SiO2 nanoparticles could decrease the frictional coefficient and the wear rate of the composites. The nanocomposites with surface-modified SiO2 nanoparticles showed better wear resistance and lower frictional coefficient than that with the unmodified nanoparticles SiO2. The specific wear rate and the steady frictional coefficient of the composite with 1.0 wt % surface-modified SiO2 nanoparticles are only 1.8 × 10,6 mm3/N m and 0.21, respectively. The dispersion of surface-modified SiO2 nanoparticles in resin matrix was observed with transmission electron microscope, and the worn surfaces of pure resin matrix and the nanocomposites were observed with scanning electron microscope. The different tribological behavior of the resin matrix and the filled composites should be dependent on their different mechanical properties and wear mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Sensitivity of applanation tonometry readings to the geometrical parameters of the sclera and the shape of the corneaACTA OPHTHALMOLOGICA, Issue 2009E VORONKOVA Purpose To study the effect of the geometrical parameters of a cornea (the thickness and difference of corneal shape from spherical segment) on applanation tonometry readings. Methods The mathematical model for Goldmann and Maklakov tonometers is developed. The corneoscleral shell is modeled as two conjugated transversal isotropic elliptic (with non-zero eccentricity) shells (cornea and sclera) with different mechanical properties. The baseline (prior to loading) two-segment shell is assumed to be filled with incompressible liquid under pressure. Simulated IOP measurements are obtained for Goldman and 5-g and 10-g Maklakov tonometers. To analyze the effect of the eyeball geometry on IOP readings the elastic constants of cornea and sclera are varied and geometrical parameters (such as central corneal thickness, cornea and sclera radii of curvature, scleral thickness, ratio of anterior-posterior eye axis lengths vs. the equator diameter) are varied. Simulated calculations are compared with experimental data. Results The results are obtained over a wide range of parameters of the sclera and cornea. Conclusion If the shape of a cornea differs from spherical it could cause the measurement error of tonometry IOP readings ranged between 3% and 25%. Significant sensitivity of the Goldmann tonometer to corneal thickness compared to Maklakov's method may be explained with smaller contact zone and, hence, the larger influence of the flexural (bending) deformation, which depends on the thickness of a shell. Contrariwise the change of the radius of curvature of cornea affects greatly on the results obtained with Maklakov tonometer. [source] Control of Crystallinity of Hydrated Products in a Calcium Phosphate CementJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Tao Yu A novel calcium phosphate cement (CPC) was prepared by dry-mechanochemical rout in this work. With the different crystallinity, the CPC showed the different degradation ratio after setting. The degradation ratio of CPC was characterized by the calcium ion-dissolving ratio in deionized water after different soaking time. With the increment of crystallinity, the setting times of CPC were prolonged, and the different mechanical property of CPC were obtained. This novel CPC was supposed to match the new bone ingrowth in vivo and have the potential application in orthopedic surgery for filling non-load-bearing bone defects. [source] | ||||||||||