Uniaxial ratcheting behavior and fatigue life models of commercial pure titanium

Abstract

The uniaxial fatigue and ratcheting behavior of commercial pure titanium (CP‐Ti) was investigated by asymmetric cyclic stress‐controlled experiments at room temperature. The effects of mean stress, stress amplitude, stress ratio, and peak stress on ratcheting behavior and fatigue life were discussed. It was found that increasing mean stress, stress amplitude, and peak stress or decreasing stress ratio reduced fatigue life and promoted ratcheting behavior. The applicability of different fatigue life models was analyzed, and a new stress ratio‐related failure model was proposed based on the exponential increase of fatigue life with stress ratio. Among all the models investigated in this study, the exponential stress ratio‐related model has more advantage in fatigue life predictions for CP‐Ti under ratcheting‐fatigue interaction.

In‐plane biaxial ratcheting effect and low‐cycle fatigue behavior of CP‐Ti based on DIC method

“…This means that the average tensile stress present in the test load will result in the accumulation of strain in the tensile direction. 16,29 In order to analyze the ratcheting strain evolution, Figure 5A shows the variation of ratcheting strain in the X-direction and Y-direction with the number of cycles for different load ratios. The ratcheting strain for biaxial loading conditions is defined as follows: 7,16,30 where ε max and ε min represent the maximum strain and minimum strain in the cyclic period.…”

“…Furthermore, the use of DIC also helps to provide a step-bystep understanding of crack emergence and extension. 16 The left-hand portion of Figure 8 shows the actual camera record of crack initiation. It can be seen that all crack initiation occurs in the central area of the specimen.…”

“…[9][10][11][12][13][14] The uniaxial fatigue and ratcheting behavior of CP-Ti under different loading conditions were researched by Le. 15,16 It was found that increasing mean stress, stress amplitude, and peak stress or decreasing stress ratio reduced fatigue life and promoted ratcheting behavior. A new stress ratio-related failure model was proposed based on the exponential increase of fatigue life with stress ratio.…”

“…The ratcheting effect depends on many factors, such as average stress, stress amplitude, frequency, loading history, and microstructure characteristics 9–14 . The uniaxial fatigue and ratcheting behavior of CP‐Ti under different loading conditions were researched by Le 15,16 . It was found that increasing mean stress, stress amplitude, and peak stress or decreasing stress ratio reduced fatigue life and promoted ratcheting behavior.…”

Prediction of asymmetric cyclic‐plastic behaviour for cyclically stable non‐ferrous materials

“…The phenomenon of ratcheting severely influences the fatigue life of engineering components, especially for structures subjected to low cycle fatigue . Experimental studies on cyclic‐plastic behaviour of ferrous and non‐ferrous materials by numerous investigators have revealed the influence of mean stress, stress amplitude, and nature of loading on ratcheting behaviour of materials, and there exists several reports on modelling the cyclic‐plastic behaviour of materials. The existing constitutive models are popularly focused towards predicting the ratcheting behaviour of ferrous materials.…”