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Yield Strain (yield + strain)
Selected AbstractsQuantitative Ultrasound Does Not Reflect Mechanically Induced Damage in Human Cancellous BoneJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000P. H. F. Nicholson Abstract This study investigated the ability of quantitative ultrasound (QUS) to detect reductions in the elastic modulus of cancellous bone caused by mechanical damage. Ultrasonic velocity and attenuation were measured using an in-house parametric imaging system in 46 cancellous bone cores from the human calcaneus. Each core was subjected to a mechanical testing regime to (a) determine the predamage elastic modulus, (b) induce damage by applying specified strains in excess of the yield strain, and (c) measure the postdamage elastic modulus. The specimens were divided into four groups: a control group subjected to a nominally nondestructive 0.7% maximum strain (,m) and three damage groups subjected to increasing strain levels (,m = 1.5, 3.0, and 4.5%). QUS measurements before and after the mechanical testing showed no significant differences between the control group and damage groups, despite highly significant (p < 0.001) reductions in the elastic modulus of up to 72%. These results indicate that current QUS techniques do not intrinsically reflect the elastic properties of cancellous bone. This is consistent with ultrasonic properties being determined by other factors (apparent density and/or architecture), which normally are associated strongly with elastic properties, but only when bone is mechanically intact. Clinically, this implies that ultrasound cannot be expected to detect bone fragility in the absence of major changes in bone density and/or trabecular architecture. [source] TEXTURAL CHARACTERIZATION OF SOY-BASED YOGURT BY THE VANE METHODJOURNAL OF TEXTURE STUDIES, Issue 2 2002IGOR V. KOVALENKO ABSTRACT The vane method was applied to evaluate failure characteristics of soy-based yogurts prepared from five soybean varieties at Brix values of 6, 8, and 10°. Yield stress, yield strain, and water-holding capacity were compared. Yield stress values ranging from 133 to 420 Pa at 2.5% protein and 498 to 1171 Pa at 4.0% protein were dependent on soybean variety and increased with increasing protein concentration. The average yield strain of samples was not affected by protein or variety. Compared to commercial dairy yogurt, soy yogurt had 132 to 445% higher yield stress at similar protein content, and was less deformable based on yield strain measurements. Water-holding capacity of soy yogurts was variety dependent, although this dependence was less pronounced at higher protein concentrations. The vane method may be effectively used as a rapid and inexpensive technique for detecting textural differences of soy-based yogurts. [source] Effects of temperature and strain rate on the tensile behavior of unfilled and talc-filled polypropylene.POLYMER ENGINEERING & SCIENCE, Issue 12 2002Part I: Experiments The tensile behavior of unfilled and 40 w% talc-filled polypropylene has been determined at four different temperatures (21.5, 50, 75 and 100°C) and three different strain rates (0.05, 0.5 and 5 min,1). Experimental results showed that both unfilled and talc-filled polypropylenes were sensitive to strain rate and temperature. Stressstrain curves of both materials were nonlinear even at relatively low strains. The addition of talc to polypropylene increased the elastic modulus, but the yield strength and yield strain were reduced. The temperature and strain rate sensitivities of these materials were also different. An energy-activated, rate sensitive Eyring equation was used to predict the yield strength of both materials. It is shown that both activation volume and activation of energy increased with the addition of talc in polypropylene. [source] Yielding behaviour of thermoplastic/elastomer blends cured by gamma irradiationPOLYMER INTERNATIONAL, Issue 3 2001A Shaltout Abstract Mechanical blends of thermoplastic medium density polyethylene (MDPE) and elastomeric ethylene propylene diene monomer (EPDM) have been prepared with a fixed composition of 60/40,wt%. They have been used either in their gum form or loaded with two different reinforcing fillers, high abrasion furnace (HAF) carbon black or precipitated SiO2 (Hi Sil) of concentration 25,100,phr (parts per hundred parts of resin) with respect to the blend. Curing was achieved by gamma irradiation. Yielding properties (yield stress, yield strain and cold drawing) have been followed as a function of irradiation dose for different blend compositions. Yield stress values increased with irradiation dose and with the content of the reinforcing filler, but yield strain and cold drawing values decreased with irradiation dose and also with the filler content. The data obtained reveal that Hi Sil is more effective as a reinforcing filler, and the prepared blends are suitable for load-bearing applications. © 2001 Society of Chemical Industry [source] | ||||||||||