scholarly journals Influence of Overburden on Seismic Compression

2019 ◽  
Vol 92 ◽  
pp. 08006
Author(s):  
Yee Eric
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Testing Machine ◽  
Volumetric Strain ◽  
Material Model ◽  
Vertical Stress ◽  
Seismic Compression ◽  
Power Rule ◽  
Density State ◽  
Simplified Procedure

The state of practice for estimating ground settlements from seismic compression is the simplified procedure. This method was developed in the 1980's and gets its name from the relatively easy method of estimating shear strain demands from potential earthquakes at a site. This procedure is generally split into two parts; a procedure that estimates shear strain demands and a volumetric strain material model. The volumetric strain material model essentially correlates shear strain to resultant volumetric strain. The volumetric strain material model used in the simplified procedure is based on a study from the 1970's, where it was observed that cyclic volumetric strain is independent of vertical stress. Laboratory testing was conducted on a variety of soil materials that are able to experience seismic compression. Reconstituted samples were subjected to cyclic loading in an advanced simple shear testing machine known as the Digitally Controlled Simple Shear device. Factors such as density state and fines content were kept constant across soil categories. Test results show volumetric strain behaviour is dependent on vertical stress and the relationship appears to be power rule based.

scholarly journals Effect of Suction on the Drained Seismic Compression of Unsaturated Sand

2019 ◽  
Vol 92 ◽  
pp. 08004 ◽  
Author(s):  
Wenyong Rong ◽  
John S. McCartney
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Bridge Decks ◽  
Matric Suction ◽  
Degree Of Saturation ◽  
Shear Tests ◽  
Unsaturated Sand ◽  
Seismic Compression ◽  
Unsaturated Sands ◽  
Constant Suction

Backfill soils in many geotechnical applications are compacted and are likely to be in an unsaturated state during operation. In earthquake-prone areas, seismic compression of unsaturated backfill soils should be understood as small settlements may have significant impacts on the performance of overlying infrastructure like bridge decks, roadways, or railways. Accordingly, the goal of this paper is to describe the results from a series of constant suction, drained, cyclic simple shear tests on unsaturated sands subjected to a range of shear strain amplitudes. A new cyclic simple shear apparatus was developed that involves control of the matric suction and monitoring of changes in degree of saturation using the hanging column approach along with monitoring of the matric suction using an embedded tensiometer.

Basic Experimental and Numerical Investigations on Chip Pressing

2013 ◽  
Vol 554-557 ◽  
pp. 630-637 ◽  
Author(s):  
Martin Grüner ◽  
Marion Merklein
Keyword(s):  
Numerical Simulation ◽  
Aluminium Alloys ◽  
Testing Machine ◽  
Material Model ◽  
Extrusion Process ◽  
Milling Process ◽  
Numerical Investigations ◽  
Compression Direction ◽  
Universal Testing ◽  
The Stability

Aluminium alloys show a great potential for lightweight constructions due to their high strength and low density but the production of this material is very energy consuming. Also the recycling of aluminium alloys, e.g. chips from the milling process, shows different challenges. Beside contamination by cooling lubricant and oxidation of the surface of the chips the melting and rolling process for new semi finish products needs a high amount of energy. TEKKAYA shows a new approach for recycling of aluminium alloy chips by an extrusion process at elevated temperatures producing different kinds of profiles. A new idea is the production of components directly out of chips using severe plastic deformation for joining of the chips similar to the accumulative roll bonding process in sheet metal forming. In a first approach aluminium alloy chips out of a milling process were uniaxial compressed with different loads inside an axisymmetric tool installed in a universal testing machine. The compressed chip disks subsequently were tested with two experiments to gain information on their stability. First experiment is a disk compression test with the disk standing on its cylindrical surface, giving information on the stability perpendicular to the compression direction. Second experiment is a stacked disk compression test with three disks to investigate the stability parallel to compression direction. During all three tests force and displacement values are recorded by the universal testing machine. These data are also processed to calculate or identify input parameters for the numerical investigations. For numerical simulation ABAQUS in conjunction with the Drucker-Prager-Cap material model, which is often used for sintering processes, seems to be a good choice. By numerical simulation of the experiments and comparison with the experiments input parameters for the material model can be identified showing good accordance. This material model will be used in future numerical investigations of an extrusion process to identify tool geometries leading to high strains inside the material and by this to an increased stability of the parts.

Stress-Strain Curves for Oxygen-Free High Conductivity Copper at Shear Strain Rates of up to 103s-1

1970 ◽  
Vol 185 (1) ◽  
pp. 1149-1158 ◽  
Author(s):  
K. Bitans ◽  
P. W. Whitton
Keyword(s):  
Shear Strain ◽  
Testing Machine ◽  
Shear Bands ◽  
Strain Curve ◽  
Strain Rates ◽  
Adiabatic Shear Bands ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
The Given ◽  
Tubular Specimens

Shear stress-shear strain curves for o.f.h.c. copper at room temperature have been obtained at constant shear strain rates in the range 1 to 103s-1, using thin walled tubular specimens in a flywheel type torsion testing machine. Results show that, for a given value of strain, the stress decreases when the rate of strain is increased. Moreover, the elastic portion of the stress-strain curve tends to disappear as the rate of strain is increased. It is postulated that these effects are due to the formation of adiabatic shear bands in the material when the given rate of strain is impressed rapidly enough. A special feature of the design of the testing machine used is the rapid application of the chosen strain rate.

scholarly journals EVOLUTION OF THE CARBON NANOTUBE BUNDLE STRUCTURE UNDER BIAXIAL AND SHEAR STRAINS

2020 ◽  
pp. 525
Author(s):  
Leysan Kh. Rysaeva ◽  
Dmitry V. Bachurin ◽  
Ramil T. Murzaev ◽  
Dina U. Abdullina ◽  
Elena A. Korznikova ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Shear Strain ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Shear Bands ◽  
Volumetric Strain ◽  
Structural Evolution ◽  
Biaxial Compression ◽  
Chain Model ◽  
Nanotube Bundle

Close packed carbon nanotube bundles are materials with highly deformable elements, for which unusual deformation mechanisms are expected. Structural evolution of the zigzag carbon nanotube bundle subjected to biaxial lateral compression with the subsequent shear straining is studied under plane strain conditions using the chain model with a reduced number of degrees of freedom. Biaxial compression results in bending of carbon nanotubes walls and formation of the characteristic pattern, when nanotube cross-sections are inclined in the opposite directions alternatively in the parallel close-packed rows. Subsequent shearing up to a certain shear strain leads to an appearance of shear bands and vortex-like displacements. Stress components and potential energy as the functions of shear strain for different values of the biaxial volumetric strain are analyzed in detail. A new mechanism of carbon nanotube bundle shear deformation through cooperative, vortex-like displacements of nanotube cross sections is reported.

Discussion on 'Shape fabrics and superimposed simple shear strain in a Precambrian shear belt, W Greenland' by John Grocott

1979 ◽  
Vol 136 (4) ◽  
pp. 497.1-500
Author(s):  
John Grocott ◽  
P. Allen ◽  
M. K. Wells
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Rock Masses ◽  
Structural History ◽  
Field Area ◽  
Different Parts ◽  
Shear Belt

THE PRESIDENT (Professor P. Allen) asked Dr Grocott if the structural history in his field area reflected events in the broader context (e.g. jostling of the Greenland blocks).DR M. K. WELLS asked the author to comment on possible variations of fabric which might be related to lithological contrasts of major rock masses in different parts of the region. Was there any evidence to suggest that the development of some form of layered anisotropy in the rocks was a necessary preliminary to the development of the second kind of fabric he described?

scholarly journals Cyclic and Permanent Shear Strains of a Soft Cohesive Soil Subjected to Combined Static and Cyclic Loading

2020 ◽  
Vol 10 (23) ◽  
pp. 8433
Author(s):  
Hernán Patiño ◽  
Rubén Galindo ◽  
Claudio Olalla Marañón
Keyword(s):  
Simple Shear ◽  
Cohesive Soil ◽  
Mediterranean Coast ◽  
Vertical Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Shear Tests ◽  
Cyclic Shear ◽  
Shear Strains ◽  
Number Of Cycles

This paper refers to cyclic shear strains (γc) and permanent shear strains (γp) of a soft cohesive soil, when both monotonic shear stresses (τo) and cyclic shear stresses (τc) are applied. The research is backed by an extensive experimental program with 139 cyclic simple shear tests that included identification and classification tests. These cyclic simple shear tests were conducted under different levels of stresses, τo, before the cyclic phase. Laboratory tests were carried out on undisturbed samples from the Port of Barcelona, located in Spain on the Mediterranean coast, and characterized by a monotonic strength (τmax) approximately equal to 30% of the initial effective vertical stress (σ′ov). The samples were taken at depths between 29 and 52 m and correspond to an initial effective vertical stress between 277 and 413 kPa, respectively. In general, the results indicate that: (a) the combination of τo and τc controls the generation of γc and γp, (b) it is not always true that when τo/σ′ov + τc/σ′ov ≈ τmax/σ′ov, the soil reaches failure cyclically, and (c) empirical relations useful for design can be established between γc, γp, and the number of cycles (N), for different relationships varying (τo/σ′ov) between 0% and 25%.

Designing Hot Working Processes of Nickel Base Superalloys Using FEM Simulation

2001 ◽  
Author(s):  
R. Kopp ◽  
M. Tschirnich ◽  
M. Wolske ◽  
J. Klöwer
Keyword(s):  
Testing Machine ◽  
Fem Simulation ◽  
Material Model ◽  
Hydraulic Testing ◽  
Compression Tests ◽  
Finite Element Program ◽  
Real Process ◽  
Forming Temperature ◽  
Element Program ◽  
Nickel Base

Knowledge of correct flow stress curves of Ni-based alloys at high temperatures is of essential importance for reliable plasto-mechanical simulations in materials processing and for an effective planning and designing of industrial hot forming schedules like hot rolling or forging. The experiments are performed on a computer controlled servo-hydraulic testing machine at IBF (Institute of Metal Forming). To avoid an inhomogeneous deformation due to the influence of friction and initial microstructure, a suitable specimen geometry and lubricant is used and a thermal treatment before testing has to provide a microstructure, similar to the structure of the material in the real process. The compression tests are performed within a furnace, which keeps sample, tools and surrounding atmosphere at the defined forming temperature. The uniaxial compressions were carried out in the range of strain rates between 0.001 and 50 s−1 and temperatures between 950 and 1280°C. Furthermore two-stage step tests are carried out to derive the work hardening and softening behaviour as well as the recrystallisation kinetics of the selected Ni-based alloys. At the end of this work a material model is adapted by the previously determined material data. This model is integrated into the Finite Element program LARSTRAN/SHAPE to calculate a forging process of the material Alloy 617.

scholarly journals Method for Evaluating Potential Maximum Shear Strain for a Fine Metal Wire in Torsion Testing

2020 ◽  
Author(s):  
S. Gondo ◽  
H. Akamine ◽  
R. Mitsui ◽  
S. Kajino ◽  
M. Asakawa ◽  
...  
Keyword(s):  
Shear Strain ◽  
Strain Distribution ◽  
High Carbon Steel ◽  
Testing Machine ◽  
External Factors ◽  
Maximum Shear Strain ◽  
Internal Factors ◽  
Torsion Testing ◽  
The Difference ◽  
Potential Maximum

Abstract The torsion number of drawn fine high carbon steel wires was measured through torsion testing. The angles between the scratches on the tested wire surface and its longitudinal axis were measured. The shear strain calculated from torsion number γt, shear strain at fractured point γf, and plastic shear strain γpc were evaluated. The following results were obtained. First, the shear strain distribution homogenized; further, torsion number per unit length N, γt, and γpc increased when decreasing the difference between γf and γpc where γpc subtracted from γf (=Δγfpc) > 0. Second, the external factors caused non-uniform shear strain distribution and reduction from the potential maximum shear strain, even for the wire that was hardly affected by the internal factors. The difference of shear strain non-uniformity caused a variation in reduction from the potential maximum shear strain. The internal factors included non-uniform microstructure and existence of inclusions and voids. The external factors were caused by the testing machine and setting of the sample. The potential maximum shear strain was obtained when the effects of internal and external factors were inhibited. Finally, two evaluation methods of the potential maximum shear strain were suggested. One method identifies a sample with a small Δγfpc, and a large γpc where Δγfpc > 0. This sample can be regarded as having the closest strain to the potential maximum shear strain. The other method determines γpc when Δγfpc is closest to 0. This value can be interpreted as plastic strain of the potential maximum shear strain.

Cyclic Simple Shear Apparatus for Low-Strain Soil Tests

1996 ◽  
Vol 1548 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Heather J. Miller ◽  
Pedro de Alba ◽  
Kenneth C. Baldwin
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Simple Shear ◽  
Recovery Period ◽  
Triaxial Tests ◽  
Cyclic Shear ◽  
Aging Period ◽  
Direct Simple Shear ◽  
Fabric Evolution ◽  
Excess Pore Pressures

A testing system has been developed to study the behavior of saturated sand under low-level cyclic shearing strains. The system has been used to determine threshold shear strain levels for fabric destruction in sand aged for different time periods. The system includes a special soil chamber and a direct simple shear (DSS) machine. To impose very small shearing strains, the DSS machine was designed to apply and measure horizontal deformations as small as 0.0005 mm (2 × 10−5 inches). Data obtained to date support the results of previous investigators who performed triaxial tests on freshly deposited samples, indicating a threshold cyclic shear strain level of approximately 0.01 percent. At strains in excess of those levels, destruction of the sand fabric occurred, as evidenced by a reduction in shear modulus at low strain levels. Subsequent modest increases in shear modulus were observed after the specimens were allowed to recover for 24 hours and then tested again. During the recovery period, drainage valves were left open to allow for dissipation of excess pore pressures and for potential consolidation during the short aging period. The DSS system was found to work well for low strain measurements. Furthermore, since shear strains are measured directly under DSS conditions (as opposed to triaxial conditions), the DSS system shows much promise as a device for studying parameters that may influence threshold shear strain levels and fabric evolution and destruction in sands.

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