Papers by Keyword: S-N Curve

Abstract: The wear resistance diagram (WRD) is a useful tool for quantitatively estimating the life span of a tribological system in sheet metal forming at different load levels. However, the WRD derived from the authors’ previous research consists merely of scattered points, which make it difficult to reliably estimate the life span and its uncertainties at all load levels. Therefore, a wear resistance curve (WRC) that encompasses the life spans of all load levels is required for a broader scope of application of wear resistance estimation. In this paper, different models for the estimation of the S-N curve describing the fatigue behavior are tested to investigate their applicability in the estimation of wear resistance curves (WRC) in sheet metal forming. WRDs of different tribological systems are investigated and the results of curve fitting are evaluated. Besides the median of the estimated life spans, the WRCs of different confidence levels are also derived quantile calculation to estimate the load dependent uncertainties of tool life spans. Moreover, due to the time-consuming experiments to determine tool life, it is necessary to discuss possibilities for achieving a satisfactory estimation with the smallest possible number of tests. Therefore, the minimal number of tests and the suitable load levels for a satisfactory estimation will be discussed. After the study, several findings have been obtained:Compared to other models, Hwang and Han’s model for estimating fatigue life of composite material shows good applicability and the highest accuracy in estimating the WRC of uncoated tools.In terms of damage development, the fatigue damage of the composite material and the damage caused by wear on uncoated tools have similarities, which explains the applicability of Hwang and Han’s model for the estimation of WRC.Both higher and lower life wear data are the prerequisite for satisfactory wear estimation.

Abstract: Prototyping a product using 3D (three-dimensional) printing process has been widely used. One of the materials commonly used is ABS (Acrylonitrile Butadiene Styrene). Currently, research did not refer to ASTM E-466 and tested specimens at 75% infill density without endurance limit analysis. The purpose of this research was to analyse the fatigue strength of 3D printed ABS material with infill density 100% due to rotating bending load according to ASTM E-466 standard, compare it with the 75% infill density test result and determine the value of its endurance limit. The research method used is experimental research by testing the fatigue strength of a number of ABS material specimens with four rotating bending load conditions until the specimen fails. The obtained result of the research is a S-N curve with maximum average cycle of 143702 at a stress of 26.87 MPa and minimum average cycle of 145 at a stress of 35.71 MPa. The shaft fatigue strength of ABS 3D printed with infill density 100% material has higher cycles at stresses below 37.1 MPa and lower cycles at stresses above 37.1 MPa compared to 75% infill density. The endurance limit obtained from the regression of the S-N curve is 16.25 MPa.

Abstract: The study of fatigue behavior of aluminum alloy 6063 exposed to periodic fatigue stresses was studied in laboratory conditions under the two conditions of the presence of the first indentation in the first test, then the presence of the phenomenon of erosion in the second test resulting from the projection of pure water Jet on samples of the same metal used in The first test. The purpose of these tests was to estimate the practical life of these samples and the resulting accumulation by using upward and downward variable stresses. A mathematical model was built to calculate the life of the samples in the above conditions, and the results of the estimated life of the samples calculated by the model showed a large convergence with the results of the estimated life of the samples practically calculated. So this mathematical model can be used to estimate the life of samples made of different minerals under these same conditions, after knowing the (S-N) curve for each metal and the amount of the value of the fatigue notch factor (Kf), which can be calculated from special tables without referring to performing practical tests for them.

Abstract: Pressure vessels are subjected to repeated loads during use and charging, which can causefine physical damage even in the elastic region. If the load is repeated under stress conditions belowthe yield strength, internal damage accumulates. Fatigue life evaluation of the structure of thepressure vessel using finite element analysis (FEA) is used to evaluate the life cycle of the structuraldesign based on finite element method (FEM) technology. This technique is more advanced thanfatigue life prediction that uses relational equations. This study describes fatigue analysis to predictthe fatigue life of a pressure vessel using stress data obtained from FEA. The life prediction results areuseful for improving the component design at a very early development stage. The fatigue life of thepressure vessel is calculated for each node on the model, and cumulative damage theory is used tocalculate the fatigue life. Then, the fatigue life is calculated from this information using the FEanalysis software ADINA and the fatigue life calculation program WINLIFE.

Abstract: With the material testing machine of electro-hydraulic servo, fatigue test have been carried out on coarse aggregate concrete with pre-crack .The fatigue life and fatigue strength of the concrete have been measured under tension and compression loading. The effect of pre-crack on concrete fatigue behavior has been analyzed based on the test results. Having regression treatment, obtained the concrete S-N curve and S-lgN curve of fatigue life. Mean-while, applying ANSYS finite element software, analysis and comparison of the fatigue behavior have been performed. The results show that pre-crack has a great influence on the fatigue behavior of concrete, and the fatigue life is reduced for 75%~80%.

Abstract: Because titanium alloy Ti6Al4V features low density, good corrosion resistance and biocompatibility, it a metal of choice for medicine, used in orthopedics, accident surgery and dentistry. The insertion of elements such as nitrogen, carbon, hydrogen, iron or oxygen improve fatigue strength of this material. This paper presents certain basic fatigue and monotonic tests performed on the alloy. We have proposed a unique sample geometry and sample dimensions smaller than the reference ones. The dimensions of the working part of the sample correspond to the geometry of a dental implant connector. This part of the implant has to withstand stresses that are both intricate and variable in time. We performed monotonic tensile strength tests and uniaxial fatigue tests using the Instron 8874 machine. Then, we examined the samples under a stereoscopic microscope and measured the fracture development angle.

Abstract: This paper presents two methods for estimating the S-N fatigue curve. The first is the traditional linear regression and staircase method. The other, alternative, method is based on random fatigue life, fatigue limit and probability. The both methods provide similar results but the latter one requires fewer test samples

Abstract: The paper presents a new thermographic method that enables simultaneous accelerated determination of the fatigue limit and the S-N curve. In the presented method, the fatigue limit was determined assuming a constant rate of temperature rise occurring in the second phase of a specimen fatigue life. The S-N curve was developed based on energy-related parameter with the assumption of its dependency on the stress amplitude. The tests made on C45 steel under reversed bending revealed that the fatigue limit value obtained from accelerated thermographic tests as compared to the value obtained using Staircase method differs by 10.0% maximum.The S-N curve obtained by accelerated thermographic method fits inside 95% confidence interval for the S-N curve obtained from the full test.

Abstract: The rotating bending fatigue properties of Ti65 titanium alloy blisk forging was studied in the present investigation. The smooth and notched specimens were prepared to test the fatigue properties at room temperature and 650°C. Meanwhile, the influences on rotating bending fatigue of temperature and type were analyzed. Furthermore, the fractural morphology was observed through scanning electron microscopy. The results showed that the medium fatigue strength of Ti65 titanium alloy decreased at 650°C compared with that at room temperature, and the fatigue strength of notched specimens indicated the same significant declination at different temperatures compared with smooth specimens. At room temperature the medium fatigue strength of smooth and notched are 473MPa and 173MPa, respectively, and the fatigue notch sensitive coefficient was 0.87. At 650°C the medium fatigue strength of smooth and notched specimens are 427MPa and 168MPa, where the fatigue notch sensitive coefficient was 0.78.

Abstract: This article describes load capacity of dynamically loaded gears, more precisely describes the mechanical pulsation tests of carburized gears with different thickness of case-hardened depth and case-hardening technology, i.e. addition or removal of certain steps during the case-hardening process of the tooth flank and foot root. The comparison was made on six different process chemical-heat treatment, in two thicknesses of case-hardened depth and two pressure angles. Results are shown and compared in a Wöhler’s curve.