Search results for "Softening"
showing 10 items of 72 documents
Recristallisation Dynamique au Cours de la Déformation à Chaud de Quatre Nuances de Bronze à 9% d'Etain
1995
Pour cerner les techniques metallurgiques des artisans protohistoriques, il est necessaire de connaitre les evolutions microstructurales obtenues selon les deformations imposees. La compression a chaud de deux bronzes industriels (contenant soit 0,026% soit 0,26% de zinc) et deux bronzes «archeologiques» (contenant soit 0,5% de soufre soit 0,5% de soufre et 0,5% de plomb) permet les observations suivantes : - Les comportements des bronzes «archeologiques» sont tres similaires : jusqu'a 600°C pour e = 0,1 on n'observe pas de recristallisation ; pour e = 1,2 on observe une recristallisation en collier le long des joints de grains. A 750°C la recristallisation semble homogene dans tout le mate…
Reversible stress softening and stress recovery of cellulose networks
2009
The mechanical properties of the plant cell wall play an important role in communication, differentiation and growth of plant cells. In particular, the expansive growth of plant cells is only possible because the material that forms the plant cell wall yields at a specific stress level, allowing for an increase in cell wall area. This process can be defined in mechanical terms as the relaxation of the wall stress. The current understanding of plant cell growth suggests that such relaxation behaviour occurs due to the presence of wall loosening agents rather than to the properties of the cellulose network itself. It is believed that certain nonenzymatic proteins, acting as wall loosening age…
Nonstationary flow surface theory for modeling the viscoplastic behaviors of soils
2016
Abstract This paper presents a three-dimensional elastic viscoplastic model that can describe the time-dependent behaviors of soft clays. The constitutive model is formulated based on the nonstationary flow surface theory and incorporates new developments, including (i) an improved definition of the nonstationary flow surface that is capable of capturing the stress–strain behaviors under different loading paths, (ii) a unique stress–strain—viscoplastic-strain-rate equation that is able to explicitly describe the nonstationary flow surface, and (iii) a final stable state concept that identifies the final equilibrium state at the end of creep and stress relaxation, which is also used to simpl…
Experimental and Numerical Study on Linear Friction Welding of AA2011 Aluminum Alloy
2014
Linear Friction Welding (LFW) is a solid-state joining process used for non-axisymmetric components. LFW involves joining of materials through the relative motion of two components undergoing an axial force. In the process, the heat source is given by the frictional forces work decaying into heat and determining a local softening of the material and eventually the needed bonding conditions. In the paper, an experimental and numerical campaign is proposed for AA2011 aluminum alloys welding. Different case studies are considered with fixed oscillation frequency and varying pressure at the interface between the specimens. Constant oscillation amplitude and specimens geometry is used. The calcu…
Investigations on the linear friction welding process through numerical simulations and experiments
2012
Abstract Linear Friction Welding (LFW) is a solid-state joining process applied to non-axisymmetric components. LFW involves joining of materials through the relative motion of two components undergoing an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. In the paper the authors present a designed and assembled laboratory fixture for LFW operations and the results of an experimental and numerical campaign aimed to weld steel parts. The dedicated fixture permitted to highlight the effect of the most important process parameters. Process conditions allowing ef…
The impact of high-temperature, short-time thermal treatment on texture and weight loss of green asparagus
1997
The kinetics of the degradation of texture and loss of weight of green asparagus heated to between 100 and 130 °C was studied. The texture of the asparagus was evaluated with two types of cells fitted to a universal texturometer: one cell measured resistance to cutting with a wire and the other was a Kramer cell. The two methods enabled distinction between the different thermal treatments, although the Kramer cell gave information about the behaviour of parts of the spear further away from the tip. The thermally induced degradation of the texture and loss of weight followed first-order kinetics. With respect to the texture, the parameters obtained with the wire cell 2.5, 5 and 7.5 cm from t…
Thermal Degradation of Green Asparagus Texture
2019
A cutting cell was developed to evaluate the texture of green asparagus by measuring its resistance to being cut with a wire. The cell was used in conjunction with a universal texturometer and improved on the single-point method of the Wilder fibrometer. Experimental conditions were determined for using the cell to measure the cutting resistance of asparagus subjected to different extents of heat treatment. Better discrimination between samples was obtained than with a Kramer cell. The fresh asparagus spears. were heated at temperatures between 70 and 100°C for different lengths of time and the kinetics of the degradation of texture was studied. A biphasic (two-component) behavior was obser…
Effects of 1-methylcyclopropene on postharvest quality of white- and yellow-flesh loquat (Eriobotrya japonicaLindl.) fruit
2014
Introduction. The effects of 1-methylcyclopropene (1-MCP) were evaluated on white-flesh cv. Claudia and yellow-flesh cv. Nespolone di Trabia loquat fruit. Materials and methods. Application of 1-MCP ((0.5 to 1) µL⋅L -1 for 20 h)) was monitored at 20 °C (7 days) and 0 °C (7 days at 0 °C and then 7 days at 20 °C). Results. Treatments with 1-MCP slowed fruit softening, depending on the concentration. Softening inhibition was greatest in fruit treated and held at 20 °C. The optimum concentration for softening inhibition at 20 °C was 1µ L ⋅L -1 of 1-MCP, while 0.5 µL⋅L -1 of 1-MCP was more effective at 0 °C. Conclusion. Treatments with 1-MCP inhibited titratable acidity loss in both cultivars. 1…
The Effect of Some Commercial Fibers on Dough Rheology
2011
Bread is largely consumed and could be used as a carrier for different nutrients. Fibers play an important role in human nutrition but the bread are depleted in this nutrient. For fibers, supplementation could be used different sources. The fibers needed to be tested before their use in breadmaking. This work investigates how some commercial fibers (Exafine, Apple AF12, Potato KF 200, Oat HF 200 and Wheat WF400) influence the rheology of dough at 10 and 15 % addition. All fibers increased the water absorption and development time because of competition for water between fibers and flour component. Product Apple AF12 deteriorates the dough rheology by dough stability reduction and increases …
Gelation of semiflexible polyelectrolytes by multivalent counterions
2012
Filamentous polyelectrolytes in aqueous solution aggregate into bundles by interactions with multivalent counterions. These effects are well documented by experiment and theory. Theories also predict a gel phase in isotropic rodlike polyelectrolyte solutions caused by multivalent counterion concentrations much lower than those required for filament bundling. We report here the gelation of Pf1 virus, a model semiflexible polyelectrolyte, by the counterions Mg(2+), Mn(2+) and spermine(4+). Gelation can occur at 0.04% Pf1 volume fraction, which is far below the isotropic-nematic transition of 0.7% for Pf1 in monovalent salt. Unlike strongly crosslinked gels of semiflexible polymers, which stif…