Computer-Aided Visioplasticity Solution to Axisymmetric Extrusion Through Curved Boundaries

1972 ◽  
Vol 94 (4) ◽  
pp. 1225-1230 ◽  
Author(s):  
A. H. Shabaik
Keyword(s):  
Material Properties ◽  
Extrusion Ratio ◽  
Strain Rates ◽  
Exit Section ◽  
Flow Function ◽  
Curved Boundaries ◽  
Circular Arc ◽  
Conical Die ◽  
Stress Components ◽  
Experimental Values

A procedure for smoothing the experimental values of the flow function ψ in axisymmetric extrusion through curved boundaries was developed. The analysis was applied to a 45 deg conical die with a 6:1 extrusion ratio and a circular arc of 0.33-in. radius and 0.033-in. land at the exit section. An analytical expression of ψ in terms of r and z was obtained and used in the calculation of velocity and strain rate components in axisymmetric extrusion of a superplastic of the eutectic of lead–tin. The stress components were obtained from the known values of the strain rates by considering equilibrium and plasticity equations and material properties.

Pemodelan Numerik Perilaku Lentur Dan Defleksi Elemen Balok Ferrogeopolymer

2021 ◽  
Vol 1 (1) ◽  
pp. 1-12
Author(s):  
Bill J. Ebenheazar ◽  
Remigildus Cornelis ◽  
Partogi H. Simatupang
Keyword(s):  
Material Properties ◽  
Cement Mortar ◽  
Small Diameter ◽  
Wire Mesh ◽  
Beam Model ◽  
Thin Wall ◽  
Numerical Result ◽  
Number Of Layers ◽  
Geopolymer Cement ◽  
Experimental Values

Ferro-gepolymer is a type of thin-wall reinforced element constructed of geopolymer cement mortar reinforced with closely spaced relatively small diameter mesh in layers. In this investigation, the flexural and the deflection behavior of the ferro-geopolymer beams were determined numerically and the results compared to the experimental values. All the experimental material properties adopted for numerical modeling. The numerical model of all the five beams was 600 mm effective span, 100 mm width, and 100 mm height. Each specimen of the beam model having different layers of wire mesh that are 3, 5, 7, 9, and 11. The results showed that the greater the number of layers, the variation between numerical and experimental results follows the same path without much difference. The numerical result showed that the greater the number of layers, the strength was increases but insignificant.

The Strain Rates of the Brain and Skull Under Dynamic Loading

2018 ◽  
Author(s):  
Mohammad Hosseini Farid ◽  
Ashkan Eslaminejad ◽  
Mohammadreza Ramzanpour ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Material Properties ◽  
Brain Injuries ◽  
Human Head ◽  
Element Model ◽  
Blast Waves ◽  
Cranial Bone ◽  
Strain Rates ◽  
Head Acceleration ◽  
Blunt Impact ◽  
The Brain

Accurate material properties of the brain and skull are needed to examine the biomechanics of head injury during highly dynamic loads such as blunt impact or blast. In this paper, a validated Finite Element Model (FEM) of a human head is used to study the biomechanics of the head in impact and blast leading to traumatic brain injuries (TBI). We simulate the head under various direction and velocity of impacts, as well as helmeted and un-helmeted head under blast waves. It is shown that the strain rates for the brain at impacts and blast scenarios are usually in the range of 36 to 241 s−1. The skull was found to experience a rate in the range of 14 to 182 s−1 under typical impact and blast cases. Results show for impact incidents the strain rates of brain and skull are approximately 1.9 and 0.7 times of the head acceleration. Also, this ratio of strain rate to head acceleration for the brain and skull was found to be 0.86 and 0.43 under blast loadings. These findings provide a good insight into measuring the brain tissue and cranial bone, and selecting material properties in advance for FEM of TBI.

Fundamentals of Residual Stresses in Joints Between Dissimilar Materials

MRS Bulletin ◽  
1995 ◽  
Vol 20 (1) ◽  
pp. 37-39 ◽  
Author(s):  
B.H. Rabin ◽  
R.L. Williamson ◽  
S. Suresh
Keyword(s):  
Residual Stresses ◽  
Material Properties ◽  
Critical Stress ◽  
Failure Mechanisms ◽  
Dissimilar Materials ◽  
Free Edge ◽  
Structural Components ◽  
Failure Characteristics ◽  
Stress Components ◽  
Metal Joint

When a discontinuity in material properties exists across a bonded interface, stresses are generated as a result of any thermal or mechanical loading. These stresses significantly affect strength and failure characteristics and may be large enough to prevent successful fabrication of a reliable joint. The use of an interlayer material to successfully reduce mismatch stresses, thereby preventing joint failure or improving joint strength and reliability, requires knowledge of failure mechanisms and of the effects of interlayer properties on the critical stress components.The origin of residual stresses developed during cooling of a ceramic-metal joint from an elevated fabrication temperature is illustrated qualitatively in Figure 1. Away from edges, the in-plane (parallel to interface) stresses are typically compressive in the ceramic and tensile in the metal. These stresses can cause cracking perpendicular to the interface, leading to spalling or delamination failures. Such failures are frequently observed in thin-film and coating geometries. Where the interface intersects a free edge, large shear and axial (perpendicular to the interface) stresses are generated. The edge stresses are typically tensile within the ceramic and tend to promote crack propagation within the ceramic parallel and adjacent to the interface. This is the most commonly observed failure mode in bonded structural components.

Effect of Time Spacing and Hatch Spacing on Thermal Material Properties and Melt Pool Geometry in Additive Manufacturing of S316L

2019 ◽  
Author(s):  
Elham Mirkoohi ◽  
Daniel E. Sievers ◽  
Steven Y. Liang
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Material Properties ◽  
Metal Additive Manufacturing ◽  
Melt Pool ◽  
Experimental Values ◽  
Melt Pool Size ◽  
Transfer Mechanisms ◽  
Hatch Spacing ◽  
Metal Additive

Abstract A physics-based analytical solution is proposed in order to investigate the effect of hatch spacing and time spacing (which is the time delay between two consecutive irradiations) on thermal material properties and melt pool geometry in metal additive manufacturing processes. A three-dimensional moving point heat source approach is used in order to predict the thermal behavior of the material in additive manufacturing process. The thermal material properties are considered to be temperature dependent since the existence of the steep temperature gradient has a substantial influence on the magnitude of the thermal conductivity and specific heat, and as a result, it has an influence on the heat transfer mechanisms. Moreover, the melting/solidification phase change is considered using the modified heat capacity since it has an influence on melt pool geometry. The proposed analytical model also considers the multi-layer aspect of metal additive manufacturing since the thermal interaction of the successive layers has an influence on heat transfer mechanisms. Temperature modeling in metal additive manufacturing is one of the most important predictions since the presence of the temperature gradient inside the build part affect the melt pool size and geometry, thermal stress, residual stress, and part distortion. In this paper, the effect of time spacing and hatch spacing on thermal material properties and melt pool geometry is investigated. Both factors are found statistically significant with regard to their influence on thermal material properties and melt pool geometry. The predicted melt pool size is compared to experimental values from independent reports. Good agreement is achieved between the proposed physics-based analytical model and experimental values.

scholarly journals Material properties of the heel fat pad across strain rates

2017 ◽  
Vol 65 ◽  
pp. 398-407 ◽  
Author(s):  
Grigoris Grigoriadis ◽  
Nicolas Newell ◽  
Diagarajen Carpanen ◽  
Alexandros Christou ◽  
Anthony M.J. Bull ◽  
...  
Keyword(s):  
Material Properties ◽  
Strain Rates ◽  
Fat Pad

Hot Deformation Behavior of Q235 Steel during Isothermal Compression at Elevated Temperature

2015 ◽  
Vol 1088 ◽  
pp. 186-190 ◽  
Author(s):  
Ben Yang ◽  
Zhou Zheng ◽  
Li Xin Wang ◽  
Yong Gang Wu
Keyword(s):  
Constitutive Relation ◽  
True Strain ◽  
Strain Curve ◽  
Strain Rates ◽  
Compression Tests ◽  
Q235 Steel ◽  
Wide Range ◽  
Allowable Range ◽  
Experimental Values ◽  
Jc Model

The isothermal hot compression tests of Q235 steel over a wide range of temperatures (1023-1123 K), strain (0.7) and strain rates (1、5、10 s−1) were performed on Gleeble-1500 system. The results show that when the deformation temperature is constant, as the strain rate increases, the flow stress also increases; Use the JC model to establish constitutive relation equation with true stress-true strain curve. And compare the prediction value of the constitutive relation equation with the experimental values, the relative error between the two is within the allowable range, indicating that the JC model constitutive relation equation applicable for the thermal deformation of Q235 steel.

High Strain Rate Compressive Properties of Soft Tissue

2003 ◽  
Author(s):  
Caleb R. Van Sligtenhorst ◽  
Duane S. Cronin ◽  
G. Wayne Brodland
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Fiber Orientation ◽  
Soft Tissues ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Post Mortem ◽  
Fresh Tissue

High strain rate material properties and constitutive equations are essential for the development of numerical and physical models to assess the performance of soft materials subject to high rate deformation, with potential applications including protective equipment and vehicle crashworthiness. However, these properties are not available for many soft tissues. This is because specialized testing methods must be employed to obtain the necessary data. Fresh bovine tissue from the semimembranosis muscle was obtained and tested using a polymeric Split Hopkinson Pressure Bar. Samples were tested from 1.4 to 200 hours post mortem to observe the effect of rigor and other possible temporal effects on the material properties. Since this muscle had relatively uniform fiber orientation, it was possible to obtain specimens with fiber directions parallel, perpendicular, and at 45 degrees to the compression axis. The stress-strain curves for the muscle were concave upwards, as is typical of soft tissues at high strain rates. Fiber orientation was determined to have negligible effect at the tested strain rates. The testing revealed that the stiffness of the tissue increased with post mortem time until approximately 6 hours. At times greater than 200 hours post mortem, the tissue properties were found to be very similar to the properties of fresh tissue. These findings suggest that properties of fresh tissue might be estimated using more easily obtained post-rigor tissue.

scholarly journals Force Budget (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 212-212
Author(s):  
I. M. Whillans ◽  
C. J. van der Veen
Keyword(s):  
Force Balance ◽  
Horizontal Gradient ◽  
Strain Rates ◽  
Normal Stresses ◽  
Lateral Shear ◽  
Vertical Column ◽  
Stress Components ◽  
Normal Resistance ◽  
Image Position ◽  
Deviatoric Stresses

An expression for force balance is derived for the general case of gradients in longitudinal and lateral normal stresses and lateral shear stress. In order to consider horizontal glacial mechanics in Newton’s style of actions and reactions, the full stresses are partitioned into lithostatic and resistive, Rij, components. The lithostatic stress is the weight of ice above, and the horizontal gradient in lithostatic force on a vertical column is the familiar driving stress, which accounts for the horizontal effect of body or action forces. The horizontal resistive-stress components describe the reactions to this horizontal action of gravity. Force balance iswith horizontal coordinates x1, x2 and vertical z. The upper and bottom elevations are h and b, and τdi and τbi are driving stress and basal drag respectively. This describes net reaction due to normal resistance, lateral shear resistance, and basal drag resistance, and finally the action or driving stress. This equation is exact. Resistive stresses are simply linked to deviatoric stresses, and hence to strain-rates, through the flow law.

Multiple Time-Scale Molecular Simulations: Modeling Realistic Loading Rates

2007 ◽  
Author(s):  
S. N. Medyanik ◽  
E. Guleryuz
Keyword(s):  
Time Scales ◽  
Md Simulation ◽  
Multiple Time ◽  
Strain Rates ◽  
Simulation Methods ◽  
Multiple Time Scale ◽  
Loading Rates ◽  
Simulation Results ◽  
Experimental Values

The vast gap between the molecular dynamics (MD) and experimental time scales poses serious problems to direct comparison between the MD simulation and experimental results. The inability of the traditional MD simulation methods to model long enough time scales also results in modeling unrealistically high loading rates and strain rates that are usually at least six or seven orders of magnitude higher than the corresponding experimental values. This may have a tremendous effect on the realism and quality of the simulation results.

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