scholarly journals Limited Stress Surface Model for Bending and Torsion Fatigue Loading with the Mean Load Value

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7023
Author(s):  
Roland Pawliczek ◽  
Dariusz Rozumek
Keyword(s):  
Stress Amplitude ◽  
Fatigue Loading ◽  
Mean Value ◽  
Fatigue Tests ◽  
Surface Model ◽  
Cycle Asymmetry ◽  
Proposed Model ◽  
Stress Surface ◽  
Alloy Steels ◽  
The Mean

In this study, a linear model of the transformation of the stress amplitude due to the mean value was used. The coefficient of the material sensitivity to cycle asymmetry with consideration of the dependence of this coefficient on the number of fatigue loading cycles is also used. A three-parameter surface model of limited stresses is proposed in this paper. The model is verified using the results of fatigue tests for cyclic bending and torsion under mean loads. The tests are performed for two types of alloy steels—S355J0 and S355J2G1W. Comparison of the allowable stress amplitudes obtained experimentally with those predicted using the proposed model shows errors of no more than 18%, with the area of the surface with the largest error being relatively small.

scholarly journals Experimental and Analytical Study on Residual Stiffness/Strength of CFRP Tendons under Cyclic Loading

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5653
Author(s):  
Chao Wang ◽  
Jiwen Zhang
Keyword(s):  
Residual Strength ◽  
Analytical Study ◽  
Damage Model ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Reinforced Polymer ◽  
Proposed Model ◽  
Residual Stiffness

Based on tension–tension fatigue tests, this paper investigated the mechanical property degradation of carbon fiber reinforced polymer (CFRP) tendons from a macroscopic perspective. According to the degradation regularity, this paper proposed a normalized phenomenological fatigue model based on the residual stiffness/strength of CFRP tendons during the fatigue loading process. In this paper, the residual stiffness of CFRP tendons were tested at five stress ranges, while the residual strength was tested at four stress ranges. In order to validate the reliability and applicability of proposed fatigue damage model, the predictions of proposed model and cited models from the literature are discussed and compared. Furthermore, experimental results from literatures were adopted to verify the accuracy of the proposed model. The results showed that the proposed model is applicable to predict both residual stiffness and residual strength throughout fatigue life cycle and has a better accuracy than models from the literature. Moreover, the three-stage degradation can be observed from the degradation processes of stiffness and strength at each stress level.

Estimation of the Minimum Canopy Resistance for Croplands and Grasslands Using Data from the 2002 International H2O Project

2008 ◽  
Vol 136 (11) ◽  
pp. 4452-4469 ◽  
Author(s):  
Joseph G. Alfieri ◽  
Dev Niyogi ◽  
Peter D. Blanken ◽  
Fei Chen ◽  
Margaret A. LeMone ◽  
...  
Keyword(s):  
Land Surface ◽  
Prediction Models ◽  
Weather Prediction ◽  
Moisture Flux ◽  
Mean Value ◽  
Surface Model ◽  
Canopy Resistance ◽  
Land Surface Models ◽  
Surface Models ◽  
The Mean

Abstract Vegetated surfaces, such as grasslands and croplands, constitute a significant portion of the earth’s surface and play an important role in land–atmosphere exchange processes. This study focuses on one important parameter used in describing the exchange of moisture from vegetated surfaces: the minimum canopy resistance (rcmin). This parameter is used in the Jarvis canopy resistance scheme that is incorporated into the Noah and many other land surface models. By using an inverted form of the Jarvis scheme, rcmin is determined from observational data collected during the 2002 International H2O Project (IHOP_2002). The results indicate that rcmin is highly variable both site to site and over diurnal and longer time scales. The mean value at the grassland sites in this study is 96 s m−1 while the mean value for the cropland (winter wheat) sites is one-fourth that value at 24 s m−1. The mean rcmin for all the sites is 72 s m−1 with a standard deviation of 39 s m−1. This variability is due to both the empirical nature of the Jarvis scheme and a combination of changing environmental conditions, such as plant physiology and plant species composition, that are not explicitly considered by the scheme. This variability in rcmin has important implications for land surface modeling where rcmin is often parameterized as a constant. For example, the Noah land surface model parameterizes rcmin for the grasslands and croplands types in this study as 40 s m−1. Tests with the coupled Weather Research and Forecasting (WRF)–Noah model indicate that the using the modified values of rcmin from this study improves the estimates of latent heat flux; the difference between the observed and modeled moisture flux decreased by 50% or more. While land surface models that estimate transpiration using Jarvis-type relationships may be improved by revising the rcmin values for grasslands and croplands, updating the rcmin will not fully account for the variability in rcmin observed in this study. As such, it may be necessary to replace the Jarvis scheme currently used in many land surface and numerical weather prediction models with a physiologically based estimate of the canopy resistance.

High-Cycle Fatigue Behavior of Type 4340 Steel Pressurized Blocks Including Mean Stress Effect

2019 ◽  
Author(s):  
Elie A. Badr ◽  
Joanne Ishak
Keyword(s):  
Stress Ratio ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Ultimate Stress ◽  
Stress Effect ◽  
Mean Stress ◽  
Test Results ◽  
Linear Correction ◽  
The Mean

Abstract Mean stress effects in pressurized steel blocks were examined under constant amplitude fatigue loading. The tests were performed to provide experimental data needed to study the effect of mean stress on fatigue lives of subject specimen, and to substantiate the use of analytical expressions to account for the mean stress. The mean stress was the result of subjecting the specimens to an autofrettage pressure which induced compressive residual stresses at the crossbore intersection of the specimens. Fatigue tests were carried out under both tensile and compressive mean stress levels. Test results were compared to several mean stress accounting relationships such as the Smith-Watson Topper, Bergmann and Seeger, modified Goodman, Gerber and Soderberg. Test results indicated that the modified Goodman equation is favorable in accounting for the effect of both tensile and compressive mean stresses on fatigue life (up to a compressive mean stress to ultimate stress ratio of −0.2). The behavior under compressive mean stress to ultimate stress ratio of less than −0.2 indicated that a linear correction relationship was required.

scholarly journals Numerical simulation model of vertical velocity distribution in a channel with artificial floating bed

2020 ◽  
Vol 20 (5) ◽  
pp. 1922-1932
Author(s):  
Yu Bai ◽  
Yonggang Duan ◽  
Wenjun Yue
Keyword(s):  
Turbulent Flows ◽  
Vertical Velocity ◽  
Velocity Model ◽  
Mean Value ◽  
Coefficient Of Determination ◽  
Eddy Simulation ◽  
Proposed Model ◽  
Large Eddy ◽  
The Mean ◽  
Boltzmann Method

Abstract Artificial floating bed (AFB), as a novel type of ecological drainage ditch, is extensively used worldwide. To more effectively design the structure of the project, an accurate velocity model is required. In this study, a two-dimensional Lattice Boltzmann method (LBM) was employed for the simulation of the vertical velocity in a channel with AFB. The large eddy simulation (LES) was conducted to simulate turbulent flows, while the drag force of AFB was discretized with a centered scheme. Two sets of experimental data were used to verify the model, the mean value of root mean square error (RMSE) and coefficient of determination (R2) are 0.93 and 1.84, respectively. This proved that the proposed model is more effective to simulate the vertical velocity in a channel with AFB.

Modeling of the stress-strain relationship for specimens made of S355J0 steel subjected to bending block loading with mean load

2017 ◽  
Author(s):  
R. Pawliczek ◽  
C.T Lachowicz
Keyword(s):  
Damage Accumulation ◽  
Stress Amplitude ◽  
Constitutive Models ◽  
Hysteresis Loops ◽  
Block Sequence ◽  
Stress History ◽  
Block Loading ◽  
Proposed Model ◽  
Strain Relationship ◽  
The Mean

The paper presents results of calculation for modelling of the stressstrain relationship in the case of block loads with mean load value. A model, based on the stable hysteresis loops, was assumed and modified to use for block loading analysis. For stress history calculation, the proposed model and two other constitutive models were used. Results of fatigue test of specimens made of S355J0 steel subjected to bending block loading with mean load value are presented and used to verify the proposed model. In the tests, the mean load was increased and decreased in subsequent blocks. The changes of strain recorded during the tests shown in the paper indicate a different behavior of the material. Damage accumulation degree for block sequence was used to compare the results of calculations. It was shown, that stress history parameters (stress amplitude and mean stress value in this case) are similar for all investigated models.

The Effect of Inclusions on Mechanical Behaviour in Ultra-High Strength Alloy Steels

2010 ◽  
Vol 654-656 ◽  
pp. 51-56 ◽  
Author(s):  
Xi Shan Xie ◽  
Yan Ping Zeng
Keyword(s):  
Harmful Effect ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Small Particles ◽  
Early Failure ◽  
The Matrix ◽  
Alloy Steels ◽  
Strength Alloy

Inclusions are un-avoidable even in super-clean engineering alloy steels because of the necessary melting process. These inclusions (such as TiN, AlN etc) are considered as harmful phases especially for ultra-high strength alloy steels. The unique experiments (in-situ tension and in-situ fatigue tests) have been conducted in a loading chamber of scanning electron microscope. TiN often characterizes with large blocky cubic morphology. Cracks easily initiate at the sharp corners of TiN cubic particles or sometimes directly initiate in TiN particles because of its brittleness. These cracks propagate to the matrix and to introduce early failure. AlN small particles (in several microns) often distribute as inclusion chains in steels. At tensile and fatigue tests cracks very often initiate at the inclusion chains among AlN small particles and line up to develop voids, which rapidly propagate to the matrix till early failure. These important results reveal the harmful effect of inclusions in micro-scale and can be connected with tensile and fatigue loading processes for understanding the early failure mechanisms.

scholarly journals The Effect of Mean Load for S355J0 Steel with Increased Strength

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 209 ◽  
Author(s):  
Roland Pawliczek ◽  
Dariusz Rozumek
Keyword(s):  
Fatigue Life ◽  
Mean Value ◽  
Mean Stress ◽  
Good Compliance ◽  
New Model ◽  
Proposed Model ◽  
Calculation Results ◽  
The Mean ◽  
Increased Strength ◽  
The Impact

The paper presents an algorithm for calculating the fatigue life of S355J0 steel specimens subjected to cyclic bending, cyclic torsion, and a combination of bending and torsion using mean stress values. The method of transforming cycle amplitudes with a non-zero mean value into fatigue equivalent cycles with increased amplitude and zero mean value was used. Commonly known and used transformation dependencies were used and a new model of the impact of the mean stress value on the fatigue life of the material was proposed. The life calculated based on the proposed algorithm was compared with the experimental life. It has been shown that the proposed model finds the widest application in the load cases studied, giving good compliance of the calculation results with the experimental results.

scholarly journals Assessment of Validity of Selected Criteria of Fatigue Life Prediction

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2310 ◽  
Author(s):  
Krzysztof Kluger ◽  
Roland Pawliczek
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Mean Value ◽  
Material Behavior ◽  
Density Parameter ◽  
Test Results ◽  
Critical Plane Approach ◽  
Calculation Results ◽  
The Mean ◽  
Number Of Cycles

The paper reports on the results of a comparison involving mathematical models applied for fatigue life calculations where the mean load value is taken into account. Several models based on the critical plane approach and energy density parameter were tested and analyzed. A fatigue test results for three types of materials are presented in this paper. The specimens were subjected to bending, torsion and a combination of bending with torsion with mean value of the load. Analysis of the calculation results show that the best fatigue life estimations are obtained by using models that are sensitive to the changes of material behavior under fatigue loading in relation to the specified number of cycles of the load.

Probabilistic Properties of Steel for Nuclear Piping

2018 ◽  
Author(s):  
Kleio Avrithi
Keyword(s):  
Mean Value ◽  
Background Information ◽  
Low Alloy Steels ◽  
Target Reliability Index ◽  
Alloy Steels ◽  
Factor Design ◽  
The Mean ◽  
Materials Used ◽  
Load And Resistance Factor ◽  
The Impact

For the development of design rules for nuclear piping using the Load and Resistance Factor Design (LRFD) method, the probabilistic properties of steel, namely, the mean value, bias, coefficient of variation, and probability distribution are needed. The paper presents background information for the existing material tables in the ASME Boiler and Pressure Vessel Code, Section II. Then it investigates the probabilistic properties for the most representative materials used for nuclear piping such as a carbon, stainless austenitic, and low alloy steels. Properties up to temperature 700°F are examined through a review of studies for the mechanical behavior of these materials. The paper discusses approaches for grouping materials in broader categories than the consideration of each type of steel separately. The impact of the steel probabilistic properties on the development of LRFD equations and the associated target reliability index is provided.

New models for depicting corrosion fatigue behaviour and calendar life of metallic structural component

2016 ◽  
Vol 231 (2) ◽  
pp. 207-222 ◽  
Author(s):  
Yu Fu ◽  
Junjiang Xiong ◽  
R Ajit Shenoi
Keyword(s):  
Corrosion Fatigue ◽  
Structural Component ◽  
Damage Model ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Surface Model ◽  
Proposed Model ◽  
New Models ◽  
Best Fitting ◽  
New Formula

New [Formula: see text] surface model is proposed for depicting corrosion fatigue behaviour and novel formulae are derived to estimate the parameters of proposed model by best fitting from a minimal experimental dataset of corrosion fatigue tests. From the Palmgren–Miner rule, a cumulative damage model for the alternation between corrosion and fatigue is developed to evaluate calendar life of metallic structural component. Corrosion tests are conducted on unnotched and notched specimens from LD10CS aluminium alloy and 15CrMnMoVA alloy steel in artificial corrosion environments. Fatigue tests are also performed on corroded specimens subjected to constant amplitude loading and the interaction mechanisms between corrosion and fatigue are deduced from fractographic studies. The applicability of the new models has been shown for experimental datasets for depicting corrosion fatigue behaviour and for evaluating calendar life of motor brace rod in helicopter.

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