Influence of the free surface and the mean stress on the heat dissipation in steels under cyclic loading

2009 ◽  
Vol 31 (8-9) ◽  
pp. 1407-1412 ◽  
Author(s):  
Charles Mareau ◽  
Véronique Favier ◽  
Bastien Weber ◽  
André Galtier
Keyword(s):  
Free Surface ◽  
Cyclic Loading ◽  
Heat Dissipation ◽  
Mean Stress ◽  
The Mean

Time-Dependent Response of Polymer Systems Under Cyclic Loading Conditions

2000 ◽  
Author(s):  
Shane Schumacher ◽  
Aleksandra M. Vinogradov ◽  
Zhiyu Liu ◽  
Christopher H. Jenkins ◽  
Isamu Kitahara ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Polyvinylidene Fluoride ◽  
Cyclic Creep ◽  
Nylon 6 ◽  
Time Dependent ◽  
Cyclic Loads ◽  
Mean Stress ◽  
Loading Conditions ◽  
Polymer Systems ◽  
The Mean

Abstract The paper concerns the time dependent response of polymer systems subjected to superimposed static and cyclic loads. An experimental study of two materials, Nylon 6/6 and a piezoelectric polyvinylidene fluoride (PVDF)-based composite, has been conducted with the objective to determine the degree of cyclic creep effects depending on the mean stress, cyclic stress amplitude and frequency. Creep acceleration due to cyclic loading effects has been observed in both materials even in the range of stresses well below their respective viscoelastic linearity limits. It is clear that these effects are essentially nonlinear, as the response of the materials to cyclic loading conditions does not represent a simple superposition of the responses to static and fully reversed cyclic loads applied separately. An increase of creep rates in both polymers has been observed consistently as frequencies and amplitudes of vibration tended to increase. However, the relation between cyclic creep effects and the mean stress appears to vary depending on the polymer type and loading conditions. Nylon 6/6 has demonstrated material hardening as a result of cycling. Considerable crack development in Nylon 6/6 has been detected only in the range of stresses approaching yield conditions.

scholarly journals An interpretation and modification of the SWT function

2021 ◽  
Author(s):  
Daniel Kujawski
Keyword(s):  
Cyclic Loading ◽  
Energy Density ◽  
Maximum Stress ◽  
Mean Stress ◽  
Complementary Energy ◽  
Absolute Value ◽  
Stress Effects ◽  
The Mean ◽  
New Interpretation ◽  
Mean Stresses

In this paper a new interpretation and modification of the SWT function in terms of the total damaging energy density is proposed and discussed. The total damaging energy density is the sum of the damaging part of the strain energy density and complementary energy density corresponding to the first quadrant in damaging σ-ε axes. For cyclic loading with positive mean stress (σ≥0) the proposed function reduces to the original SWT formulation. For cyclic loading with negative mean stress (σ<0) the maximum stress is augmented by 1/3 of absolute value of the mean stress. The proposed approach shows a consistent correlation of the mean stress effects for both positive and negative mean stresses.

Comparative study of the effective parameters on residual stress relaxation in welded aluminum plates under cyclic loading

2020 ◽  
Vol 21 (5) ◽  
pp. 505
Author(s):  
Yousef Ghaderi Dehkordi ◽  
Ali Pourkamali Anaraki ◽  
Amir Reza Shahani
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Stress Relaxation ◽  
Stress Amplitude ◽  
Cyclic Plasticity ◽  
Mean Stress ◽  
Effective Parameters ◽  
Perfect Plasticity ◽  
Residual Stress Relaxation ◽  
Aluminum Plates

The prediction of residual stress relaxation is essential to assess the safety of welded components. This paper aims to study the influence of various effective parameters on residual stress relaxation under cyclic loading. In this regard, a 3D finite element modeling is performed to determine the residual stress in welded aluminum plates. The accuracy of this analysis is verified through experiment. To study the plasticity effect on stress relaxation, two plasticity models are implemented: perfect plasticity and combined isotropic-kinematic hardening. Hence, cyclic plasticity characterization of the material is specified by low cycle fatigue tests. It is found that the perfect plasticity leads to greater stress relaxation. In order to propose an accurate model to compute the residual stress relaxation, the Taguchi L18 array with four 3-level factors and one 6-level is employed. Using statistical analysis, the order of factors based on their effect on stress relaxation is determined as mean stress, stress amplitude, initial residual stress, and number of cycles. In addition, the stress relaxation increases with an increase in mean stress and stress amplitude.

Two New Universal Relations in Nonlinear Elasticity and Some Related Matters

1994 ◽  
Vol 61 (4) ◽  
pp. 784-787 ◽  
Author(s):  
M. Aron ◽  
S. Aizicovici
Keyword(s):  
Nonlinear Elasticity ◽  
Ground State ◽  
Mean Stress ◽  
The Mean

Two inequalities which for certain deformation classes may be viewed as universal relations are shown to hold for two distinct subclasses of unconstrained rubberlike solids. The inequalities express the fact that the mean stress corresponding to any purely distortional deformation originating from a given ground state is dominated by (and, respectively, dominates) the mean stress in that ground state. Also discussed is a case in which the deformations involved are necessarily homogeneous.

scholarly journals Assessment of CFD turbulence models for free surface flow simulation and 1-D modelling for water level calculations over a broad-crested weir floodway

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Ahmed M Helmi
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Water Level ◽  
Dimensional Analysis ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
One Dimensional ◽  
The Mean ◽  
The One

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

Nonlinear Aspects of Subcritical Shallow-Water Flow Past Two-Dimensional Obstructions

1978 ◽  
Vol 22 (04) ◽  
pp. 203-211
Author(s):  
Nils Salvesen ◽  
C. von Kerczek
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Flow Problem ◽  
Free Stream ◽  
The Body ◽  
Two Dimensional ◽  
Third Order ◽  
Submerged Body ◽  
The Mean ◽  
The Waves

Some nonlinear aspects of the two-dimensional problem of a submerged body moving with constant speed in otherwise undisturbed water of uniform depth are considered. It is shown that a theory of Benjamin which predicts a uniform rise of the free surface ahead of the body and the lowering of the mean level of the waves behind it agrees well with experimental data. The local steady-flow problem is solved by a numerical method which satisfies the exact free-surface conditions. Third-order perturbation formulas for the downstream free waves are also presented. It is found that in sufficiently shallow water, the wavelength increases with increasing disturbance strength for fixed values of the free-stream-Froude number. This is opposite to the deepwater case where the wavelength decreases with increasing disturbance strength.

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