Correlation between Thermal Behaviour of AA5754-H111 during Fatigue Loading and Fatigue Strength at Fixed Number of Cycles

Abstract

The characterization of the fatigue behaviour of aluminium alloys is still capturing the attention of researchers. As it is well known in literature, for certain alloys, in a specific range of cycles number, the S-N curves do not present any asymptote. So that, problems result in the assessment of the fatigue life. In these conditions, the concept of the fatigue limit has to be replaced by the fatigue strength at a fixed number of loading cycles. Temperature acquisitions during fatigue tests allow for a specific analysis that can support the researchers in understanding the complex processes that are involved in fatigue and their influence on fatigue life, even for aluminium alloys. In fact, the analysis of the surface temperature signal that was detected during a self-heating test provides a curve that is characterized by a distinct slope-change point at a specific stress value. Even though researchers have been investigating fatigue life characterisation and temperature variations for more than a decade, it is not clear what this point represents in terms of fatigue strength. The aim of the present paper is to find out a possible correlation between the thermal behaviour of AA5754-H111 undergoing self-heating testing procedure and fatigue strength at a specific loading cycles.

Fatigue limit estimation of metals based on the thermographic methods: A comprehensive review

“…For the first block, it is suggested that the maximum stress should be 20%-30% of the ultimate tensile strength of the material to ensure collecting enough data below the fatigue limit. 142 The stress increment between each block can be varied but should be set such that the total test duration remains practical while still collecting a satisfactory number of data points around the fatigue limit. 119 During each block, thermographic acquisitions are performed for a predefined time period and sampling frequency.…”

“…As mentioned before, each block includes a specific number of cycles, and after completing each block, the stress is increased until the material fails. For the first block, it is suggested that the maximum stress should be 20%–30% of the ultimate tensile strength of the material to ensure collecting enough data below the fatigue limit 142 . The stress increment between each block can be varied but should be set such that the total test duration remains practical while still collecting a satisfactory number of data points around the fatigue limit 119 …”

“… can be related to various factors including the loss of the adiabatic condition, plastic deformation, damage, and surface treatment. The change of these parameters with respect to the stress amplitude was used to probe into the thermoelastic and plastic behavior of the material, the fatigue behavior of materials 148 especially with high diffusive behavior like aluminum, 142 and estimating the fatigue limit 26,111 …”

Fatigue Life Improvement of Cracked Aluminum 6061-T6 Plates Repaired by Composite Patches

“…Traditional methods of repairing aluminum alloys, for instance, mechanical fastening, could lead to new defects. Composite patches, unlike traditional methods, do not cause any damage to the parent plate and can be replaced several times [ 1 , 2 , 3 , 4 , 5 , 6 ]. Fiber-reinforced polymer composites are the right choice for being used as a patch since these materials have a high stiffness-to-weight ratio, good fatigue resistance, and excellent corrosion resistance [ 7 , 8 , 9 , 10 ].…”

Fatigue Limit Evaluation of AZ31B Magnesium Alloy Based on Temperature Distribution Analysis

“…The accurate assessment of fatigue performance is important for the design and use of engineering structures [1]. In recent decades, a fatigue performance assessment method based on the temperature rise of materials or components under fatigue loading has been developed and applied [2][3][4]. The temperature increase of the material during fatigue comes from the increase of internal energy generated by mechanical work conversion [5,6], which is so-called fatigue self-heating.…”