Papers by Keyword: Fatigue Design

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 study discusses the issue of determining the accuracy of fatigue characteristics in a high-cycle fatigue range using analytical-experimental methods. The analytical-experimental methods are defined as a characteristic curve obtained using an analytical method and additional experiment aimed to increase its accuracy. The higher the amount of data the higher the characteristic curve accuracy. The study aims to address the question “what values should be determined experimentally to obtain an S-N curve in a high-cycle fatigue range with a satisfactory estimation of the fatigue life.

Abstract: The results of linear elastic finite element analyses of stress concentration factor (SCF) and through-thickness stress distribution for 80 weld toe T-butt plate geometries are presented in parametric form for tension (membrane) loading. The closed-form solutions, which describe the stress state of the two-dimensional plane stress models studied in terms of weldment angle, weld toe radius, weld attachment width and plate thickness, are accurate and wide ranging. The SCF is presented in full parametric form and also as a simple reduced expression, quantifying the degree of error from raw data in each case. An expression for the stress distribution through the potential Mode I crack plane of the uncracked geometries is also presented in full parametric form. It is anticipated that these HBC equations will be particularly useful in the calculation of weight functions for stress intensity factors (SIFs) of fatigue cracks emanating from weld toes in T-butt welded joints, especially in the presence of known residual stresses, or those resulting from peening.

Abstract: This study presents definitions of principal stress/strain range and mean stress/strain introduced by utilizing Itoh-Sakane criterion for multiaxial loading including non-proportional loading, and shows the method of calculating the non-proportional factor which expresses the severity of non-proportional loading under the multiaxial 3D loading. This paper also shows a method of visually presenting the stress/strain, the non-proportionality of loading and the damage evaluation.

Abstract: The paper presents the analytical method of determining the S-N curve based on the static material properties. To verify the procedure algorithm, an experiment has been carried out to define the reference fatigue characteristics of material 42CrMo4. The research was performed with the use of the rotary-bending test stand made according to ones own design. The proper operation of the material testing machine was verified compliant with the ISO 1143 standard and presented in the previous paper [7]. To compare the proposed method, different characteristics according to analytical methods from literature have been determined. To verify this approach, statistical calculation has been performed. Statistical method was derived from paper [3]. The best results were achieved by the proposed method. As analytical method can lead to large error, which was presented in the papers [4,7,8], it was decided to use hybrid method. That method is based on analytical method supported by a simple experiment. Verification of this approach has produced satisfactory results.

Abstract: The paper presents accelerated methods for determining the fatigue curve in high cycle fatigue. The estimated fatigue characteristics using these algorithms always show an error, however the applicable literature does not seem to specify how accurate the methods are, which calls for their further examination. To verify the approximation methods, material C45+C was tested to provide reference characteristics. For the experimental results to be received, the test equipment developed applying own design was used. The analysis of the data has confirmed a good operation of the testing machine. To verify the accelerated methods, there was applied the statistics method to compare the coefficients of the regression curve from the experimental data and the coefficients of the analytical regression method. Using that comparison method, it can be assumed that only the estimated curve applying the algorithm by Strzelecki P. & Sempruch J. demonstrates the factors equal to the empirical line.

Abstract: The paper presents method for determined S-N curve used only static properties of material. To verified this algorithm, material C45+C was tested to provide reference fatigue characteristics. Tests was carrying out with rotating bending by equipment own design. Test machine was checked for correct working according standard ISO 1143. Verification of analytical method has been realized by statistical calculation assume null hypothesis that coefficient of slope of straight line and absolute term estimated by proposed algorithm is equal to coefficient of slope and absolute term estimated from experimental data. Calculated value of statistics has shown that there is no reason to reject null hypothesis for proposed method.

Abstract: The prevention of fatigue failure is an important consideration in the design of aeroengine shafts. In this paper, based on the elastic and elstic-plastic finite element analyses, for a series of small-scale hollow shafts with transverse holes, the maximum princple stress and von Mises stresss around the hole have been obtained. Hence, using McDiarmid and Von Mises criteria, the fatigue crack initiation site and life can be determined. The hoop stress, which is the driving force for the Mode I growth of short cracks initiated around the hole, has been characterised as well.

Abstract: The study of Low-Cycle fatigue showed that strain is more important parameter than stress for describing fatigue property of materials .Exactly obtaining regional strain of the structure by analysis is key in fatigue design of complex structure .Therefore, the analysis and solution by finite element is very necessary. The maximum elastic and plastic strain at the nozzle junction of a pressure vessel under several loadings are calculated by using ANSYS software .Then crack forming life is calculated by using the N.E.Dowling formula .

Abstract: This paper presents an original approach in mechanical design to integrate the manufacturing constraints in the final CAD model. A specific user-interface is proposed to integrate manufacturing constraints (for example tolerances) and manufacturing consequences (for example roughness or hardening) into the model. One of the important consequences of manufacturing processes is the generation of residual stresses into the part. An appropriate tool has been developed and used as a design tool to manage the global evolution of residual stresses in the mechanical part and to obtain the deformed geometry resulting from the applied manufacturing plan. These results could eventually be used in fatigue simulation. To support the model, a database is used for the integration of residual stresses from stored experimental results, analytical or numerical calculations. An example of a metal sheet, laminated and deformed by shot peening is given, the deformed geometry is rebuilt and compared to the experimental results.