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Quasi-static Loading (quasi-static + loading)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Dynamic numerical simulations of void growth and coalescence with stress triaxiality maintained constant,Application to ductile solids with secondary voids

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008
L. Siad
Abstract Dynamic explicit finite element analysis is used to investigate void growth and plastic collapse of an axisymmetric unit cell model with a primary spherical void imbedded in a porous matrix material. The Gurson,Tvergaard,Needleman homogenized model is used to describe the plastic behaviour of the matrix material. The simulations are performed under large strain conditions for varying secondary void volume fractions and quasi-static loading controlled by constant stress triaxiality. The proposed accomplishment of constant stress triaxiality associated with dynamic explicit computations provides a method allowing to trace the collapse of the unit cell from the onset of coalescence to practically its final failure. Consistent with experimental and theoretical results available in the literature, the obtained results substantiate the sensitivity of coalescence to the presence of secondary voids. Copyright © 2008 John Wiley & Sons, Ltd. [source]

PREDICTION OF MECHANICAL PROPERTIES OF CUMIN SEED USING ARTIFICIAL NEURAL NETWORKS

JOURNAL OF TEXTURE STUDIES, Issue 1 2010
M.H. SAIEDIRAD
ABSTRACT In this paper, two artificial neural networks (ANNs) are applied to acquire the relationship between the mechanical properties and moisture content of cumin seed, using the data of quasi-static loading test. In establishing these relationship, the moisture content, seed size, loading rate and seed orientation were taken as the inputs of both models. The force and energy required for fracturing of cumin seed, under quasi-static loading were taken as the outputs of two models. The activation function in the output layer of models obeyed a linear output, whereas the activation function in the hidden layers were in the form of a sigmoid function. Adjusting ANN parameters such as learning rate and number of neurons and hidden layers affected the accuracy of force and energy prediction. Comparison of the predicted and experimented data showed that the ANN models used to predict the relationships of mechanical properties of cumin seed have a good learning precision and good generalization, because the root mean square errors of the predicated data by ANNs were rather low (4.6 and 7.7% for the force and energy, respectively). PRACTICAL APPLICATIONS Cumin seed is generally used as a food additive in the form of powder for imparting flavor to different food preparations and for a variety of medicinal properties. Physical properties of cumin seeds are essential for the design of equipment for handling, harvesting, aeration, drying, storing, grinding and processing. For powder preparation especially the fracture behavior of the seeds are essential. These properties are affected by numerous factors such as size, form and moisture content of the grain and deformation speed. A neural network model was developed that can be used to predict the relationships of mechanical properties. Artificial neural network models are powerful empirical models approach, which can be compared with mathematical models. [source]

Shear properties of epoxy under high strain rate loading

POLYMER ENGINEERING & SCIENCE, Issue 4 2010
Niranjan K. Naik
Shear properties of epoxy LY 556 under high strain rate loading are presented. Torsional Split Hopkinson Bar apparatus was used for the studies in the shear strain rate range of 385,880 per sec. Experimental details, specimen configuration and development, data acquisition, and processing are presented. Shear strength, shear modulus, and ultimate shear strain are presented as a function of shear strain rate. For comparison, studies are presented at quasi-static loading. It is observed that the shear strength at high strain rate is enhanced up to 45% compared with that at quasi-static loading in the range of parameters considered. Further, it is observed that, in the range of parameters considered, the change in shear properties with the change in shear strain rate is not significant. Comparison of torque versus time behavior derived from signals obtained from strain gauges mounted on incident bar and transmitter bar is also presented. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers [source]

Experimental study of sharp-tipped projectile perforation of GFRP plates containing sand filler under high velocity impact and quasi-static loadings

POLYMER COMPOSITES, Issue 10 2009
Ali Reza Sabet
Penetration and perforation behavior of glass fiber reinforced plastic (GFRP) plates containing 20% sand filler have been investigated via high velocity impact tests using sharp tipped (30°) projectile and quasi-static perforation tests. Two size sand filler (75 and 600 ,m) were used in 4-, 8-, and 14-layered laminated composite plates to study sensitivity of filler size toward loading system. Composite plates were examined for perforation load rate at 5 mm/min and high-velocity impact loading up to 220 m/s. Results indicated higher energy absorption for GFRP plates containing sand filler for both high-velocity impact and quasi-static perforation tests. Higher ballistic limits were recorded for specimens containing sand filler. The study showed clear role played by coarse-sized sand filler as a secondary reinforcement in terms of higher energy absorption as compared with nonfilled and specimens containing fine-sized fillers. The investigation successfully characterized behavior of quasi-static test during penetration and perforation of the sharp-tipped indenter as an aid for impact application studies. Residual frictional load in the specimens containing sand filler constituted considerable portion of load bearing during perforation in quasi-static tests. Delaminations followed by fiber and matrix fracture were major failure mode in high-velocity tests and the main energy absorbing mechanism in thick-walled plates, whereas in quasi-static tests the failures were more of matrix fracture and fiber sliding. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]