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.

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.

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.

Biaxial Fatigue of Inconel 718 Including Mean Stress Effects

2008 ◽  
pp. 463-463-19 ◽  
Author(s):  
DF Socie ◽  
LA Waill ◽  
DF Dittmer
Keyword(s):  
Inconel 718 ◽  
Mean Stress ◽  
Stress Effects ◽  
Biaxial Fatigue

Multiaxial Fatigue Damage Models

2006 ◽  
Vol 324-325 ◽  
pp. 747-750 ◽  
Author(s):  
De Guang Shang ◽  
Guo Qin Sun ◽  
Jing Deng ◽  
Chu Liang Yan
Keyword(s):  
Shear Strain ◽  
Fatigue Damage ◽  
Multiaxial Fatigue ◽  
Normal Strain ◽  
Critical Plane ◽  
Proportional Loading ◽  
Maximum Shear Strain ◽  
Damage Models ◽  
Thin Tube ◽  
Critical Plane Approach

Two multiaxial damage parameters are proposed in this paper. The proposed fatigue damage parameters do not include any weight constants, which can be used under either multiaxial proportional loading or non-proportional loading. On the basis of the research on the critical plane approach for the tension-torsion thin tubular multiaxial fatigue specimens, two multiaxial fatigue damage models are proposed by combining the maximum shear strain and the normal strain excursion between adjacent turning points of the maximum shear strain on the critical plane. The proposed multiaxial fatigue damage models are used to predict the fatigue lives of the tension-torsion thin tube, and the results show that a good agreement is demonstrated with experimental data.

Study of the Multiaxial Fatigue Life Influencing Factors Based on the Critical Plane Approach

2011 ◽  
Vol 295-297 ◽  
pp. 2314-2320
Author(s):  
Peng Min Lv ◽  
Chun Juan Shi
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Phase Difference ◽  
Amplitude Ratio ◽  
Uniaxial Stress ◽  
Multiaxial Fatigue ◽  
Normal Strain ◽  
Critical Plane ◽  
Proportional Loading ◽  
Maximum Shear Strain

The tension-torsion thin walled tube specimens were used as the researching object in this paper. The method of determination to the critical plane which has the maximum normal strain and maximum shear strain was expounded. The strain state on the critical plane under non-proportional loading was analyzed, and the unified prediction model was used to calculate the fatigue life. In order to research the influence of phase difference on fatigue life under the non-proportional loading, the relation of the equivalent strain and the phase difference in different positive strain amplitude and different strain amplitude ratio were analyzed. It’s found that the dangerous phase difference which has the shortest fatigue life is in direct relation with the strain amplitude ratio. The general formula of dangerous phase difference is presented. Through the material mechanics performance and fatigue parameters of uniaxial stress state, the coefficients in the formula can be obtained and the coefficients of 15 kinds of common materials are given for practical application.

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.

scholarly journals On the phase angle role in the shear response of ZK60 Mg alloys under multiaxial fatigue

2019 ◽  
Vol 300 ◽  
pp. 08005
Author(s):  
Seyyed Mohamad Hasan Karparvarfard ◽  
Seyed Behzad Behravesh ◽  
Sugrib Kumar Shaha ◽  
Hamid Jahed
Keyword(s):  
Shear Strain ◽  
Phase Angle ◽  
Strain Amplitude ◽  
Volume Fraction ◽  
Axial Strain ◽  
Active Phase ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Shear Response ◽  
Significant Difference

Proportional and non-proportional multiaxial fatigue tests are conducted on the closed-die forged ZK60 extrusion. The shear strain amplitude was kept constant at 0.5% for all the tests, while two different axial strain amplitudes of 0.4% and 0.7% were considered. At the higher strain amplitude (0.7%) significant difference was observed between the torque amplitudes of proportional and non-proportional tests, whereas the axial load amplitude responses remained the same regardless of the phase angle shifts. It is likely that as the phase angle changes from 0-90, the twin volume fraction at the peak shear strain decreases resulting in higher torque responses. On the other hand, at the lower strain amplitude, i.e. 0.4%, where twinning is not active, phase angle does not show any effect on the shear response. An energy-based fatigue model is employed that effectively explains the different damage contributions by the axial and torsional loadings at different strain amplitudes, and accurately predicts the proportional and non-proportional multiaxial fatigue lives.

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.

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