Definition of Strain Amplitude for Cyclic Model to Simulate Actual Damping of Soils under Irregular Loadings

2013 ◽  
Vol 353-356 ◽  
pp. 2163-2170
Author(s):  
Fang Cheng Liu ◽  
Jun Yang ◽  
Wei Zhang
Keyword(s):  
Shear Strain ◽  
Strain Amplitude ◽  
Soil Behavior ◽  
Nonlinear Soil Behavior ◽  
Behavior Simulation ◽  
Loading Trajectory ◽  
Reversed Loading ◽  
Definition Of ◽  
Cyclic Models ◽  
Shear Strain Amplitude

The determination of damping constitutes an essential part of the cyclic characterization of soils. While because of the damping of soils is nonlinear, ie., strain-dependent, the definition of shear strain amplitude under irregular loading process construct the key point of the damping based cyclic models. This paper introduces a new damping-based model (DBM) for nonlinear soil behavior simulation and discusses on the effect of shear strain amplitude definition on model behavior. Both qualitative and quantitative analysis re-sults show that the reversed hysteresis loading curve is significantly influenced by the pre-supposed loading amplitude and generally large pre-proposed shear strain amplitude will lead to low reversed loading trajectory. Analytical comparison among several definitions indicates that defining the maximum reversal point of history as the loading amplitude performs the best.

Shear Modulus and Damping Ratio of Gravel Material

2011 ◽  
Vol 105-107 ◽  
pp. 1426-1432 ◽  
Author(s):  
De Gao Zou ◽  
Tao Gong ◽  
Jing Mao Liu ◽  
Xian Jing Kong
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Dynamic Shear Modulus ◽  
Test Results ◽  
Dynamic Shear ◽  
Data Points ◽  
Shear Strain Amplitude

Two of the most important parameters in dynamic analysis involving soils are the dynamic shear modulus and the damping ratio. In this study, a series of tests were performed on gravels. For comparison, some other tests carried out by other researchers were also collected. The test results show that normalized shear modulus and damping ratio vary with the shear strain amplitude, (1) normalized shear modulus decreases with the increase of dynamic shear strain amplitude, and as the confining pressure increases, the test data points move from the low end toward the high end; (2) damping ratio increases with the increase of shear strain amplitude, damping ratio is dependent on confining pressure where an increase in confining pressure decreased damping ratio. According to the test results, a reference formula is proposed to evaluate the maximum dynamic shear modulus, the best-fit curve and standard deviation bounds for the range of data points are also proposed.

Mean Stress Effects in Biaxial Fatigue of Inconel 718

1984 ◽  
Vol 106 (3) ◽  
pp. 227-232 ◽  
Author(s):  
D. F. Socie ◽  
T. W. Shield
Keyword(s):  
Shear Strain ◽  
Strain Amplitude ◽  
Inconel 718 ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Normal Strain ◽  
Maximum Shear Strain ◽  
Cracking Behavior ◽  
Biaxial Fatigue ◽  
Shear Strain Amplitude

Biaxial fatigue tests were conducted on Inconel 718 thin-walled tubular specimens to quantify the effect of mean stress. The specimens were loaded in combined tension and torsion in strain control at room temperature. Fatigue lives ranged from 3000 to 15,000 cycles depending on the mean stress. These data were correlated with a parameter based on the maximum plastic shear strain amplitude, normal strain amplitude and mean normal stress on the plane of maximum shear strain amplitude. This parameter was combined with the Coffin-Manson equation for estimating fatigue lives. Observations of the cracking behavior show that mean stress affects the rate of crack growth and distribution of cracks.

scholarly journals Empirical Formulas of Shear Modulus and Damping Ratio for Geopolymer-Stabilized Coarse-Grained Soils

2021 ◽  
Vol 9 ◽  
Author(s):  
Shengnian Wang ◽  
Xinqun Gao ◽  
Wei Ma ◽  
Guoyu Li ◽  
Chong Shi ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Large Scale ◽  
Damping Ratio ◽  
Coarse Grained ◽  
Dynamic Shear Modulus ◽  
Empirical Formulas ◽  
Confining Pressures ◽  
Shear Strain Amplitude

The contribution of gravel fraction on the maximum shear modulus (Gmax), dynamic shear modulus ratio (G/Gmax), and damping ratio (λ) of cementitious coarse-grained soils has not been fully understood yet. Large-scale triaxial cyclic tests for geopolymer-stabilized coarse-grained soils (GSCGSs) were conducted with different volumetric block proportions (VBPs) under various confining pressures (CPs) for investigating their dynamic behaviors and energy dissipation mechanisms. Results indicate that the Gmax of GSCGS increases linearly with VBPs but nonlinearly with CP. High VBPs will probably result in a gentle decrease in G/Gmax and a rapid increase in normalized λ (λnor), while the opposite is the case for a high CP. With the shear strain amplitude being normalized, the G/Gmax and λnor are distributed in a narrow band with low dispersion and thus can be well-described by empirical functions of the normalized shear strain amplitude.

Fatigue of AL6XN Stainless Steel

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Sergiy Kalnaus ◽  
Yanyao Jiang
Keyword(s):  
Fatigue Life ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Fatigue Behavior ◽  
Equivalent Plastic Strain ◽  
Multiaxial Fatigue ◽  
Cyclic Plasticity ◽  
Pure Torsion ◽  
Shear Cracking ◽  
Shear Strain Amplitude

Tension-compression, torsion, and axial-torsion fatigue experiments were conducted on the AL6XN alloy to experimentally investigate the cyclic plasticity behavior and the fatigue behavior. The material is found to display significant nonproportional hardening when the equivalent plastic strain amplitude is over 2×10−4. In addition, the material exhibits overall cyclic softening. Under tension-compression, the cracking plane is perpendicular to the axial loading direction regardless of the loading amplitude. The smooth strain-life curve under fully reversed tension-compression can be described by a three-parameter power equation. However, the shear strain-life curve under pure torsion loading displays a distinct plateau in the fatigue life range approximately from 20,000 to 60,000 loading cycles. The shear strain amplitude corresponding to the plateau is approximately 1.0%. When the shear strain amplitude is above 1.0% under pure shear, the material displays shear cracking. When the shear strain amplitude is below 1.0%, the material displays tensile cracking. A transition from shear cracking to tensile cracking is associated with the plateau in the shear strain-life curve. Three different multiaxial fatigue criteria were evaluated based on the experimental results on the material for the capability of the criteria to predict fatigue life and the cracking direction. Despite the difference in theory, all the three multiaxial criteria can reasonably correlate the experiments in terms of fatigue life. Since the cracking mode of the material subjected to pure torsion is a function of the loading magnitude, the prediction of cracking orientation becomes rather challenging.

Stiffness and strength changes in cohesionless soils due to disturbance

1992 ◽  
Vol 29 (5) ◽  
pp. 853-861 ◽  
Author(s):  
Thomas G. Thomann ◽  
Roman D. Hryciw
Keyword(s):  
Shear Strain ◽  
Strain Amplitude ◽  
Ground Surface ◽  
Field Tests ◽  
Horizontal Stress ◽  
Stress Index ◽  
Cohesionless Soils ◽  
Dense Sand ◽  
Tip Resistance ◽  
Shear Strain Amplitude

A laboratory and field study of stiffness and strength changes to cohesionless soils due to disturbance has been performed. Laboratory samples were tested in a resonant column torsional shear device. The magnitude of the stiffness loss in laboratory samples was found to be primarily a function of the imposed shear strain amplitude. The time for the stiffness to regain values prior to disturbance also appears to be controlled by the shear strain amplitude. In field tests, decreases in soil strength and stiffness were observed following an explosive detonation in a partially saturated, medium-dense sand. Although there were no measured changes in the soil density, the ground surface elevation, and the dilatometer horizontal stress index, the cone tip resistance and shear wave velocity decreased noticeably. Subsequent time-dependent increases in penetration resistance were observed; however, at certain locations, the increases were not large enough to offset the initial decreases. Comparisons are made between changes in the laboratory and field stiffness values following disturbance, and possible explanations for the behavior are presented. Key words : soil dynamics, disturbance, shear strain amplitude, in situ testing, shear modulus, time effects.

Relationship Between Soil Stiffness Gauge Modulus and Other Test Moduli for Granular Soils

2003 ◽  
Vol 1849 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Auckpath Sawangsuriya ◽  
Tuncer B. Edil ◽  
Peter J. Bosscher
Keyword(s):  
Shear Strain ◽  
Strain Amplitude ◽  
Laboratory Tests ◽  
Resilient Modulus ◽  
Granular Soils ◽  
Dynamic Force ◽  
Element Analysis ◽  
Near Surface ◽  
Soil Stiffness ◽  
Shear Strain Amplitude

Recently, there has been a concerted effort to develop methods for direct measurement of soil stiffness, modulus, or both. A new field test device called the soil stiffness gauge (SSG), which is currently marketed as GeoGauge, shows potential to assess near-surface stiffness. A comparison is presented of moduli obtained from the SSG with moduli obtained from other tests on granular soils. The maximum singleamplitude dynamic force produced during the SSG measurement is determined to be 17.3 N. On this basis, an estimate of the shear strain amplitude produced from the SSG is made by finite element analysis. A plot of shear modulus versus shear strain amplitude on a medium sand obtained from different laboratory tests, including the SSG, is presented. The comparison of the SSG modulus with the moduli from other laboratory tests indicates that the SSG outputs a dynamic modulus corresponding to a strain amplitude approximately 20 times higher than the expected range and with a magnitude lower than it should be on the basis of the induced strain. Nevertheless, the SSG modulus is still higher than that from the resilient modulus test typically used for pavement design.

scholarly journals Cyclic Deformation and Low-Cycle Fatigue for 316LN Stainless Steel under Non-proportional Loading

2019 ◽  
Vol 300 ◽  
pp. 08002
Author(s):  
Yajing Li ◽  
Bin Ren ◽  
Xu Chen
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Amplitude Ratio ◽  
Cyclic Behavior ◽  
Loading Path ◽  
Proportional Loading ◽  
Loading Paths ◽  
Shear Strain Amplitude

The effects of loading path and strain amplitude ratio on the cyclic behavior and fatigue life were investigated on a 316LN nuclear grade stainless steel employing a series of symmetrically strain-controlled fatigue tests at room temperature. The loading paths of Uniaxial, Torsional, Proportional, Rhombic, Rectangular, and Circular were employed with the constant equivalent strain amplitude of 0.5%. The strain amplitude ratio of 2.35, 1.73 and 1.27, defined by the ratio of shear strain amplitude to the axial strain amplitude, was realized by changing the shear strain amplitude under Proportional, Rhombic, Rectangular and Elliptical loading paths. As expected, the significant non-proportional additional hardening was observed. It’s interesting to note that the axial cyclic stress response varied with the strain amplitude ratio, and the law was different under different loading paths. The fatigue life of all the tests were evaluated by three critical plane criteria proposed by Smith-Watson-Topper (SWT), Fatemi-Socie (FS) and Chen-Xu-Huang (CXH). Results show that the SWT criterion significantly overestimated the fatigue life of non-proportional loading because the effect of shear damage was not considered. The CXH criterion for tensile-type failure yielded good prediction results except for two torsional data points. The FS criterion provided better predictions than other models.

Multiaxial Fatigue Life Predictions Under the Influence of Mean-Stresses

1988 ◽  
Vol 110 (4) ◽  
pp. 380-388 ◽  
Author(s):  
Ali Fatemi ◽  
Peter Kurath
Keyword(s):  
Fatigue Life ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Multiaxial Fatigue ◽  
Mean Stress ◽  
Stress Strain ◽  
Life Predictions ◽  
1045 Steel ◽  
Mean Stresses ◽  
Shear Strain Amplitude

Two materials, an Inconel 718 and a 1045 steel, are used to verify the extension of a shear strain-based parameter developed to account for out-of-phase cyclic strain hardening to multiaxial mean-stresses. Shear strain amplitude on the maximum shear strain amplitude plane and the maximum stress normal to this plane are the nominal stress-strain parameters considered in this approach. Tension-torsion and axial-internal pressure loadings using tubular specimens are employed to investigate stress-strain states that exhibit mean-strains and/or mean-stresses. Deformation response relevant to the proposed fatigue damage algorithm such as mean-stress relaxation is discussed. Adequate fatigue life correlations are obtained by implementing the proposed analysis. It is also demonstrated that methodologies successful for correlating uniaxial mean-stress data often lead to erroneous multiaxial life predictions.

scholarly journals Magneto-induced rheological properties of magnetorheological gel under quasi-static shear with large deformation

RSC Advances ◽  
2020 ◽  
Vol 10 (53) ◽  
pp. 31691-31704
Author(s):  
Runsong Mao ◽  
Huixing Wang ◽  
Guang Zhang ◽  
Xudan Ye ◽  
Jiong Wang
Keyword(s):  
Magnetic Field ◽  
Shear Rate ◽  
Energy Dissipation ◽  
Shear Strain ◽  
Rheological Properties ◽  
Large Deformation ◽  
Strain Amplitude ◽  
Magnetic Particles ◽  
Static Shear ◽  
Shear Strain Amplitude

Magnetorheological gel is a material composed of magnetic particles and polyurethane. CIPs content, shear rate, shear strain amplitude and magnetic field affect damping performance. The magento-induced enhancement of energy dissipation density of MRG-60 could reach 104900%.

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