scholarly journals Experimental Method for Plotting S-N Curve with a Small Number of Specimens

2016 ◽  
Vol 23 (4) ◽  
pp. 129-137 ◽  
Author(s):  
Przemysław Strzelecki ◽  
Janusz Sempruch
Keyword(s):  
Fatigue Life ◽  
Least Squares Method ◽  
Experimental Results ◽  
Bending Test ◽  
Likelihood Method ◽  
Staircase Method ◽  
Random Occurrence ◽  
Straight Line ◽  
Standard Documents ◽  
Time Required

Abstract The study presents two approaches to plotting an S-N curve based on the experimental results. The first approach is commonly used by researchers and presented in detail in many studies and standard documents. The model uses a linear regression whose parameters are estimated by using the least squares method. A staircase method is used for an unlimited fatigue life criterion. The second model combines the S-N curve defined as a straight line and the record of random occurrence of the fatigue limit. A maximum likelihood method is used to estimate the S-N curve parameters. Fatigue data for C45+C steel obtained in the torsional bending test were used to compare the estimated S-N curves. For pseudo-random numbers generated by using the Mersenne Twister algorithm, the estimated S-N curve for 10 experimental results plotted by using the second model, estimates the fatigue life in the scatter band of the factor 3. The result gives good approximation, especially regarding the time required to plot the S-N curve.

scholarly journals Analysis of selected mathematical models of high-cycle S-N characteristics

2017 ◽  
Vol 3 (20) ◽  
pp. 227-240
Author(s):  
Przemysław Strzelecki ◽  
Janusz Sempruch ◽  
Tomasz Tomaszewski
Keyword(s):  
Fatigue Life ◽  
Maximum Likelihood ◽  
Maximum Likelihood Method ◽  
Least Squares Method ◽  
Construction Materials ◽  
The Other ◽  
Likelihood Method ◽  
Staircase Method ◽  
Aisi 1045 ◽  
Fatigue Characteristics

The paper presents two approaches of determining S-N fatigue characteristics. The first is a commonly used and well-documented approach based on the least squares method and staircase method for limited fatigue life and fatigue limit, accordingly. The other approach employs the maximum likelihood method. The analysis of the parameters obtained through both approaches exhibited minor differences. The analysis was performed for four steel construction materials, i.e. C45+C, 45, SUS630 and AISI 1045. It should be noted that the quantity of samples required in the second approach is significantly smaller than with the first approach, which translates into lower duration and costs of tests.

Modification of MnS inclusion by tellurium in 38MnVS6 micro-alloyed steel

2020 ◽  
Vol 117 (6) ◽  
pp. 615
Author(s):  
Ping Shen ◽  
Lei Zhou ◽  
Qiankun Yang ◽  
Zhiqi Zeng ◽  
Kenan Ai ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aspect Ratio ◽  
Strong Influence ◽  
Experimental Results ◽  
Alloyed Steel ◽  
Equivalent Diameter ◽  
Small Aspect Ratio ◽  
Steel Quality ◽  
Eds Analysis ◽  
Micro Alloyed Steel

In 38MnVS6 steel, the morphology of sulfide inclusion has a strong influence on the fatigue life and machinability of the steel. In most cases, the MnS inclusions show strip morphology after rolling, which significantly affects the steel quality. Usually, the MnS inclusion with a spherical morphology is the best morphology for the steel quality. In the present work, tellurium was applied to 38MnVS6 micro-alloyed steel to control the MnS inclusion. Trace tellurium was added into 38MnVS6 steel and the effect of Te on the morphology, composition, size and distribution of MnS inclusions were investigated. Experimental results show that with the increase of Te content, the equivalent diameter and the aspect ratio of inclusion decrease strikingly, and the number of inclusions with small aspect ratio increases. The inclusions are dissociated and spherized. The SEM-EDS analysis indicates that the trace Te mainly dissolves in MnS inclusion. Once the MnS is saturated with Te, MnTe starts to generate and wraps MnS. The critical Te/S value for the formation of MnTe in the 38MnV6 steel is determined to be approximately 0.075. With the increase of Te/S ratio, the aspect ratio of MnS inclusion decreases and gradually reaches a constant level. The Te/S value in the 38MnVS6 steel corresponding to the change of aspect ratio from decreasing to constant ranges from 0.096 to 0.255. This is most likely to be caused by the saturation of Te in the MnS inclusion. After adding Te in the steel, rod-like MnS inclusion is modified to small inclusion and the smaller the MnS inclusion, the lower the aspect ratio.

Theoretical accuracy of the last squares method in the isotope dilution analysis

1984 ◽  
Vol 49 (4) ◽  
pp. 805-820
Author(s):  
Ján Klas
Keyword(s):  
Least Squares ◽  
Isotope Dilution ◽  
Least Squares Method ◽  
Isotope Dilution Analysis ◽  
Straight Line ◽  
The One ◽  
Two Parameter ◽  
Theoretical Accuracy

The accuracy of the least squares method in the isotope dilution analysis is studied using two models, viz a model of a two-parameter straight line and a model of a one-parameter straight line.The equations for the direct and the inverse isotope dilution methods are transformed into linear coordinates, and the intercept and slope of the two-parameter straight line and the slope of the one-parameter straight line are evaluated and treated.

A modified tangent-gas approximation for two-dimensional steady flow

1958 ◽  
Vol 4 (6) ◽  
pp. 600-606 ◽  
Author(s):  
G. Power ◽  
P. Smith
Keyword(s):  
Least Squares ◽  
Steady Flow ◽  
Variational Approach ◽  
Least Squares Method ◽  
Two Dimensional ◽  
Subsonic Flows ◽  
Von Karman ◽  
Straight Line ◽  
Volume Relationship ◽  
Pressure Volume Relationship

A set of two-dimensional subsonic flows past certain cylinders is obtained using hodograph methods, in which the true pressure-volume relationship is replaced by various straight-line approximations. It is found that the approximation obtained by a least-squares method possibly gives best results. Comparison is made with values obtained by using the von Kármán-Tsien approximation and also with results obtained by the variational approach of Lush & Cherry (1956).

Image Reconstruction on Quincunx Patterned Green Channel

2013 ◽  
Vol 717 ◽  
pp. 493-496
Author(s):  
Gwang Gil Jeon
Keyword(s):  
Image Reconstruction ◽  
Least Squares ◽  
Least Squares Method ◽  
Interpolation Method ◽  
Experimental Results ◽  
Color Filter ◽  
Image Artifacts ◽  
Green Channel ◽  
Filter Array ◽  
Single Sensor

This paper addresses the issue of the quincunx patterned green channel interpolation method that is obtained by single sensor cameras. Our goal is to reconstruct the green channel in Bayer color filter array (CFA) data. We present a new filter-based method for the reduction of image artifacts in green channel. To reconstruct green channel, we trained a filter using least squares method. Experimental results confirm the effectiveness of the proposed method. Compared to other bilinear and bicubic filters, the improvement in quality has been achieved.

Experimental and numerical investigation of the thermomechanical load on a turbine housing in a radial turbocharger

2021 ◽  
pp. 095440702110521
Author(s):  
Shaolin Chen ◽  
Hong Zhang ◽  
Liaoping Hu ◽  
Guangqing He ◽  
Fen Lei ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Fatigue Life ◽  
Simulation Analysis ◽  
Simulation Method ◽  
Testing Temperature ◽  
Experimental Results ◽  
Maximum Temperature ◽  
Monitoring Point ◽  
Turbine Housing

The fatigue life of turbine housing is an important index to measure the reliability of a radial turbocharger. The increase in turbine inlet temperatures in the last few years has resulted in a decrease in the fatigue life of turbine housing. A simulation method and experimental verification are required to predict the life of a turbine housing in the early design and development process precisely. The temperature field distribution of the turbine housing is calculated using the steady-state bidirectional coupled conjugate heat transfer method. Next, the temperature field results are considered as the boundary for calculating the turbine housing temperature and thermomechanical strain, and then, the thermomechanical strain of the turbine housing is determined. Infrared and digital image correlations are used to measure the turbine housing surface temperature and total thermomechanical strain. Compared to the numerical solution, the maximum temperature RMS (Root Mean Square) error of the monitoring point in the monitoring area is only 3.5%; the maximum strain RMS error reached 11%. Experimental results of temperature field test and strain measurement test show that the testing temperature and total strain results are approximately equal to the solution of the numerical simulation. Based on the comparison between the numerical calculation and experimental results, the numerical simulation and test results were found to be in good agreement. The experimental and simulation results of this method can be used as the temperature and strain (stress) boundaries for subsequent thermomechanical fatigue (TMF) simulation analysis of the turbine housing.

The Use of Strain Energy and Fracture Correlation to Determine Life Expectancy for Notched Components

2009 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross ◽  
M.-H. Herman Shen
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Cross Section ◽  
Strain Energy ◽  
Notch Root ◽  
Stress Gradient ◽  
Strain Curve ◽  
Experimental Results ◽  
Cyclic Process ◽  
Notched Components

An energy-based method for predicting fatigue life of half-circle notched specimens, based on the nominal applied stress amplitude, has been developed. This developed method is based on the understanding that the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where the density of each can be determined by measuring the area underneath the monotonic true stress-strain curve and measuring the sum of the area within each Hysteresis loop in the cyclic process, respectively. Using this understanding, the criterion for determining fatigue life prediction of half-circle notched components is constructed by incorporating the stress gradient effect through the notch root cross-section. Though fatigue at a notch root is a local phenomenon, evaluation of the stress gradient through the notch root cross-section is essential for incorporating this method into finite element analysis minimum potential energy process. The validation of this method was carried out by comparison with both notched and unnnotched experimental fatigue life of Aluminum 6061-T6 (Al 6061-T6) specimens under tension/compression loading at the theoretical notch fatigue stress concentration factor of 1.75. The comparison initially showed a slight deviation between prediction and experimental results. This led to the analysis of strain energy density per cycle up to failure, and an improved Hysteresis representation for the energy-based prediction analysis. With the newly developed Hysteresis representation, the energy-based prediction comparison shows encouraging agreement with unnotched experimental results and a theoretical notch stress concentration value.

scholarly journals A New Method for the Extraction of Diode Parameters Using a Single Exponential Model

2000 ◽  
Vol 22 (3) ◽  
pp. 157-163 ◽  
Author(s):  
S. Dib ◽  
M. De La Bardonnie ◽  
A. Khoury ◽  
F. Pelanchon ◽  
P. Mialhe
Keyword(s):  
Least Squares Method ◽  
Exponential Model ◽  
New Method ◽  
Ordinate Axis ◽  
Straight Line ◽  
Current Voltage ◽  
Method Approach ◽  
Single Exponential

A new method for extracting junction parameters of the single diode model is presented. A least squares method approach considers the deviation ∆V=f(I) between the experimental current-voltage (I-V) characteristic and a theoretical arbitrary characteristic. A specific case- the ∆V graph reducing to a straight line–is identified and the knowledge of the slope and of the intercept with the ordinate axis leads to the determination of the junction parameters. The method is applied to the characterization of the emitter-base junction of transistors and the results are discussed.

Sign in / Sign up

Export Citation Format

Share Document