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Fracture Strain (fracture + strain)
Selected AbstractsAnalysis of Superplastic Deformation of AZ31 Magnesium Alloy,ADVANCED ENGINEERING MATERIALS, Issue 9 2007K. Abu-Farha AZ31 is a magnesium alloy possessing good mechanical properties, which makes it particularly attractive for automotive applications. Yet, in order to advance the utilization of this alloy, a broad database of its superplastic behavior is needed. This work presents the results of a comprehensive study on the elevated temperature superplastic behavior of the AZ31 magnesium alloy. Flow stress, fracture strain and strain sensitivity index maps were constructed over a wide range of strain rates, covering temperatures between 325 and 450 °C. [source] Predicting the J integral fracture toughness of Al 6061 using the small punch testFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2007E. BUDZAKOSKA ABSTRACT The 6000 series aluminium alloys (Al,Mg,Si systems) are commonly used as medium-strength structural materials; in particular, the 6061 (Al,1Mg,0.6Si) alloy is widely utilized as a general-purpose structural material due to its excellent formability and corrosion-resisting capabilities. The objective of this study was to obtain a correlation between the small punch (SP) test estimated equivalent fracture strain (,qf) and fracture toughness (J1C) property for 6061 aluminium, and determine its viability as a non-destructive fracture toughness test technique for remaining life assessment of in-service components. Samples of 6061-T6 aluminium were cut from bulk plate, in both the longitudinal and transverse directions, for the as-received condition as well as subjected to three different over-ageing heat-treatment schedules. A strong linear correlation between valid J1C and SP estimated biaxial fracture strain ,qf is presented for aluminium 6061 at room temperature. [source] CHARACTERISTICS OF GELLAN GUM BASED FOOD GELSJOURNAL OF TEXTURE STUDIES, Issue 4 2010DIPJYOTI SAHA ABSTRACT Fruit-based gels with gellan gum as the gelling agent was prepared. Textural attributes of the gellan gum gels, formed with different concentrations of the gum (0.5,3.0%) and sugar and/or pineapple juice, were determined employing the methods of large-deformation uniaxial compression and stress relaxation. Fracture stress/energy markedly increases with an increase in the concentration of gellan gum while fracture strain exhibits a marginal effect. The change in these compressive textural parameters is more pronounced for sugar added samples compared with gels without sugar. Marked decay in stress relaxation curves was observed; the extent of relaxation decreases marginally with an increase in gum content up to 2% but shows much lesser values beyond 2% addition. The sugar added samples exhibit lesser relaxation characteristics but higher relaxation times indicating elastic characteristics compared with samples without sugar. Use of gellan gum provides an innovative method for developing fruit juice based gels as a convenience food because of attractive transparent appearance and textural attributes. PRACTICAL APPLICATION The use of hydrocolloids like gellan gum can develop fabricated foods in the form of fruit juice based gels having unique textural properties. These properties can be altered to suit the consumer preference by varying the proportions of gellan gum, fruit juice and sugar. The results in the present investigation arising from compression and relaxation testing thus help in characterizing the developed gels. [source] ELECTROSTATIC EFFECTS ON PHYSICAL PROPERTIES OF PARTICULATE WHEY PROTEIN ISOLATE GELSJOURNAL OF TEXTURE STUDIES, Issue 4 2001MATTHEW K. McGUFFEY Physical properties of particulate whey protein isolate gels formed under varying electrostatic conditions were investigated using large strain rheological and microstructural techniques. The two treatment ranges evaluated were adjusting pH (5.2-5.8) with no added NaCl and adjusting the NaCl (0.2-0.6 M) at pH 7. Gels (10% protein w/v) were formed by heating at 80C for 30 min. The large strain properties of fracture strain (,f), fracture stress (,f), and a measure of strain hardening (R0.3) were determined using a torsion method. Gel microstructure was evaluated using scanning electron microscopy (SEM) and gel permeability (Bgel). Overlaying ,f and ,f curves for pH and NaCl treatments demonstrated an overlap where gels of equal ,f and ,f could be formed by adjusting pH or NaCl concentration. The high fracture stress (,f, 23 kPa and ,f, 1.86) pair conditions were pH 5.47 and 0.25 M NaCl, pH 7.0. The low fracture stress (,f, 13 kPa and ,f, 1.90) pair conditions were pH 5.68 and 0.6 M NaCl, pH 7.0. The 0.25 M NaCl, pH 7 treatment demonstrated higher R0.3 values than the pH 5.47 treatment. When the sulfhydryl blocker n-ethylmaleimide was added at 2 mM to the 0.25 M NaCl, pH 7 gel treatment, its rheological behavior was NSD (p>0.05) to the pH 5.47 gel treatment, indicating disulfide bond formation regulated strain hardening. Altering surface charge or counterions, and disulfide bonding, was required to produce gels with similar large strain rheological properties. An increase in gel permeability coincided with an increase in pore size as observed by SEM, independent of rheological properties. This demonstrated that at the length scales investigated, microstructure was not linked to changes in large strain rheological properties. [source] VARIATIONS IN FLEXURAL AND COMPRESSIVE FRACTURE BEHAVIOR OF A BRITTLE CELLULAR FOOD (DRIED BREAD) IN RESPONSE TO MOISTURE SORPTIONJOURNAL OF TEXTURE STUDIES, Issue 5 2000Y. P. CHANG Mechanical properties of dried bread (a cellular baked product) equilibrated at different water activities (Aw) were measured using three-point bending and uniaxial compression to compare their responses to moisture sorption. The glass-to-rubber transition was clearly demarcated in all the mechanical property-Aw curves, although there were differences in critical Aw (0.32,0.56) at which the dramatic changes in mechanical properties occurred. The role of water appeared to be strictly that of a plasticizer where flexural mechanical parameters were concerned, leading to reduced modulus and fracture stress but increased fracture strain with increasing Aw. Uniaxial compression tests revealed moisture-induced mechanical antiplasticization effects on the material in the glassy state which resulted in maximum compressive fracture stress but minimum fracture strain over the Aw range from 0,0.56. Compressive modulus apparently was not affected much by moisture sorption up to an Aw of 0.43, above which it decreased sharply. [source] Prediction of sensory textural properties from rheological analysis for process cheeses varying in emulsifying salt, protein and moisture contentsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2007Colm D Everard Abstract Textural characteristics of process cheeses varying in emulsifying salt (disodium phosphate), protein and moisture contents were evaluated by rheological compression using texture profile analysis and by sensory evaluation. The primary objective of this study was to predict sensory textural parameters using instrumental rheological parameters. All sensory parameters correlated with one or more instrumental parameters, e.g. rheological firmness versus sensory firmness (R = 0.98, P < 0.001), rheological chewiness versus sensory rubbery (R = 0.92, P < 0.001) and rheological chewiness versus sensory chewy (R = 0.86, P < 0.001). Partial least squares calibration models were developed for each of nine sensory parameters using instrumental parameters. Principal component analysis of instrumental and sensory parameters illustrated relationships among parameters. It was shown that instrumental parameters could be used to supplement sensory evaluation of process cheese texture. Increasing emulsifying salt content increased firmness, springiness and chewiness and decreased adhesiveness, mouthcoating and mass formation. Increasing protein content resulted in increased fracture strain and stress and chewiness and decreased melting. Increasing moisture content increased cohesiveness and decreased firmness and chewiness. Copyright © 2007 Society of Chemical Industry [source] Thermal analysis of poly(3-hydroxybutyrate- co -3-hydroxyvalerate) irradiated under vacuumPOLYMER INTERNATIONAL, Issue 11 2004Huili Yang Abstract Poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) was irradiated by 60Co ,-rays (doses of 50, 100 and 200 kGy) under vacuum. The thermal analysis of control and irradiated PHBV, under vacuum was carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile properties of control and irradiated PHBV were examined by using an Instron tensile testing machine. In the thermal degradation of control and irradiated PHBV, a one-step weight loss was observed. The derivative thermogravimetric curves of control and irradiated PHBV confirmed only one weight-loss step change. The onset degradation temperature (To) and the temperature of maximum weight-loss rate (Tp) of control and irradiated PHBV were in line with the heating rate (°C min,1). To and TP of PHBV decreased with increasing radiation dose at the same heating rate. The DSC results showed that 60Co ,-radiation significantly affected the thermal properties of PHBV. With increasing radiation dose, the melting temperature (Tm) of PHBV shifted to a lower value, due to the decrease in crystal size. The tensile strength and fracture strain of the irradiated PHBV decreased, hence indicating an increased brittleness. Copyright © 2004 Society of Chemical Industry [source] | |||||||||||||