Large Deformations Near a Pair of Closely-Spaced Spherical Voids in a Rate-Dependent Solid

A set of geometrically based FCC crystal slip-systems hardening inequalities is analytically investigated in (110) channel die compression for all lateral constraint directions between and , following previous analyses of the other two distinct orientation ranges in (110) compression. With all critical slip systems active, it is proved that these inequalities uniquely predict initial lattice stability and finite crystal shearing only in the horizontal channel plane, consistent with experiments for this range of orientations. (The earlier analyses had predicted load-axis stability in both orientation ranges, and lattice stability in one, also commonly found experimentally.) Moreover, it is established that the lateral constraint stress predicted by the hardening inequalities will be less than that given by classic Taylor hardening as this stress evolves with deformation. It is further shown, taking into account experimental stress–strain curves and latent hardening experiments for aluminium and copper, that lattice stability generally can be expected to very large deformations, except perhaps for lateral constraint orientations near the end of the range, which result is consistent with experiment. In appendix A, the possibilities of solutions with a critical slip system inactive are investigated, and predictions of a power law rate-dependent plasticity model are analysed for comparison with the results based on the hardening inequalities.

Download Full-text

Modeling Temperature and Strain Rate Dependent Large Deformations of Metals

Applied Mechanics Reviews ◽

10.1115/1.3120834 ◽

1990 ◽

Vol 43 (5S) ◽

pp. S312-S319 ◽

Cited By ~ 100

Author(s):

Douglas J. Bammann

Keyword(s):

Strain Rate ◽

Large Deformations ◽

Uniaxial Stress ◽

Thermal Softening ◽

Plasticity Model ◽

Anisotropic Hardening ◽

Temperature Dependent ◽

History Effects ◽

Rate Dependent ◽

Comparison With Experimental Data

We review the development of a strain rate and temperature dependent plasticity model for finite deformation. In particular we address both the method of determining the parameters of the model and the engineering meaning of the parameters in terms of uniaxial stress-strain curves. The ability of the model to predict some aspects of anisotropic hardening, strain rate history effects, and thermal softening are then illustrated by comparison with experimental data.

Download Full-text

Strain Rate Dependent Constitutive Modelling of 3D Printed Polymers

EPJ Web of Conferences ◽

10.1051/epjconf/202125002029 ◽

2021 ◽

Vol 250 ◽

pp. 02029

Author(s):

Maria Lißner ◽

Daniel Thomson ◽

Nik Petrinic ◽

Jeroen Bergmann

Keyword(s):

Strain Rate ◽

Large Deformations ◽

Material Model ◽

Constitutive Modelling ◽

Experimental Results ◽

Good Representation ◽

Material Models ◽

Rate Dependent ◽

3D Printed ◽

Dependent Behaviour

Experimental results from 3D printed TPC (thermoplastic copolyester) compression specimens were used to develop a combined experimental-numerical framework to support the design of e.g. 3D printed mouthguards. First, a commercially available material model capable of representing the strain-rate dependent behaviour of materials undergoing large deformations is identified. Second, experimental results from solid 3D printed compression specimens are used to calibrate the identified material models. Third, 3D printed compression specimens with two different cavity geometries are used to assess the ability of the material model to accurately reproduce the experimental observations. The numerical investigation indicates a good representation of the strain rate dependent experimental results of 3D printed specimens.

Download Full-text

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079176 ◽

1977 ◽

Vol 35 ◽

pp. 330-333

Author(s):

T. Gulik-Krzywicki ◽

M.J. Costello

Keyword(s):

Biological Materials ◽

Molecular Organization ◽

X Ray Diffraction ◽

Glass Capillary ◽

X Ray ◽

Rate Dependent ◽

Before And After ◽

Freeze Etching ◽

Diffraction Patterns ◽

Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Download Full-text