مقايسه روش هاي متفاوت براي پيش بيني اثر فاق بر روي عمر خستگي فولاد HSLA100 و مقايسه با داده هاي تجربي

چكيده انگليسي :

78 Assessment of Different Methods for Notch Effect Prediction on Fatigue Life of HSLA100 Steel and Comparison with Experimental Results Javad Amirian j amirian@me iut ac ir 13th September 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Mehran Moradi moradi@cc iut ac ir Mehdi Shirani shirani@cc iut ac irAbstractA part with an unchanging cross sectional area under the load has uniform and homogeneous stress and straindistribution Any type of notch existence or sudden changes in cross section causes inhomogeneousdistribution of stress and strain Typically fatigue failure of an element arises where the stress level rises dueto the stress concentration effect such as a notch on a surface Notch is usually defined as a geometricdiscontinuity Notch may be introduced either by design or by the manufacturing process A hole in acomponent is an example of a design notch Material and fabrication defects such as weld defects inclusions casting defects or machining marks are notches which are introduced due to the manufacturing process Thepresent paper investigates the effect of notch on the fatigue life of the HSLA100 steel which is widelyapplicable in the marine industry HSLA is a type of alloy steel that provides better mechanical properties orgreater resistance to corrosion compared to carbon steel HSLA steels are not made to meet a specificchemical composition but rather to specific mechanical properties and as a result they are different fromother kinds of steels The main goal of this research is to compare different methods of predicting fatigue lifeof notched HSLA100 specimens and find which ones yield better results Experimental were conducted onthe smooth and notched specimen and mechanical properties and S N curve were obtained Rotating bendingfatigue tests were conducted on cylindrical specimens according to ASTM E 466 A constant load is appliedperpendicular to the specimens which is rotated at 50 Hz Fourteen smooth specimens and twelve notchedspecimens were tested The finite element software used in the present investigation was not capable ofdirectly modelling the stress amplitude distribution in an axisymmetric specimen under rotating bending However by superimposing suitably weighted FEA stress distributions from bending about the y and z axes the stress amplitude distribution in rotating bending can be readily obtained Based on the obtainedexperimental S N curve for smooth specimens and modelling the stress amplitude distribution of rotatingcylindrical notched specimen S N curves for notched specimens were predicted by Weibull s weakest link Peterson Neuber stress gradient and critical distance methods The S N curves and fatigue stressconcentration factor were obtained of all methods and compared with experimental result and weakest linktheory was selected best method in terms of the availability of the required materials data the predictivecapability and the compatibility with FEA stresses Key wordsFatigue life Weakest link theory Notch Steel HSLA100 Modelling Predictive capability

اميريان، جواد

مقايسه روش هاي متفاوت براي پيش بيني اثر فاق بر روي عمر خستگي فولاد HSLA100 و مقايسه با داده هاي تجربي