Abstract
An evaluation model of aluminum alloy welded joint low-cycle fatigue data based on information entropy is proposed. Through calculating and analyzing the information entropy of decision attributes, quantitative contribution of stress concentration, plate thickness, and loading mode to the fatigue destruction are researched. Results reveal that the total information entropy of the fatigue data based on nominal stress, structural stress and equivalent structural stress are, respectively, 0.9702, 0.8881, and 0.8294. There is consistency between the reducing trend of the weight-based information entropy and the smaller and smaller standard deviation of the S-N curves. In the structural stress based S-N curve, total stress concentration factor is crucial for the distribution of the fatigue data and the weight based information entropy of membrane stress concentration factor is 0.6754, which illustrates that stress concentration is a key issue of welded structure to which ought to be attached great importance. Subsequently, in the equivalent structural stress-based S-N curve, the weight based information entropy of stress ratio is 0.5759, which plays an important role in the distribution of fatigue data. With the importance level of the attributes on the S-N curves investigated, the correction of R in the equivalent structural stress based master S-N curve method should be carried out to make the welding fatigue prediction much more accurate.
Highlights
At present, the widely-applied welding fatigue design and prediction are mainly based on nominal stress (NS) approach, hot spot stress (HSS) approach, and the master S-N curve approach [1].As is well-known, the nominal stress method was firstly proposed and used maturely for the fatigue analysis of welded structures [2]
Three S-N curves for aluminum alloy welded joints are established based on nominal stress, structural stress, and equivalent structural welded are established on nominal structural stress, life anddata equivalent structural stress stress injoints the master
Three S-N curves for aluminum alloy welded joints are established based on nominal stress, structural stress, and equivalent structural stress by means of the least square method
Summary
The widely-applied welding fatigue design and prediction are mainly based on nominal stress (NS) approach, hot spot stress (HSS) approach, and the master S-N curve approach [1].As is well-known, the nominal stress method was firstly proposed and used maturely for the fatigue analysis of welded structures [2]. Afterwards, in order to obtain the accurate stress in the welding toe, the hot spot stress (HSS) method that is extrapolated based on the nominal stress was first proposed by Niemi [6] It characterizes the stress condition in the weld toe by taking the effects of geometry structure into account so that hot spot stress can be extrapolated through an extrapolation formula indirectly in complex welded structures [7]. This solves some problems existing in the nominal stress method, it is difficult to establish a uniform hot spot type and extrapolation formula for various welding types, which limits its engineering applications
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