A method for predicting ultra-high cycle fatigue life of high-strength titanium alloy electron beam welded joints

Abstract

The invention discloses a method for predicting the ultra-high cycle fatigue life of a high-strength titanium alloy electron beam welded structure. Ultrasonic fatigue tests are used to obtain the ultra-high cycle fatigue performance of high-strength titanium alloy electron beam welded joints. Based on the nano-crack propagation theory, electron beam welding defects are introduced. Size parameters, establish the ultra-high cycle fatigue life loss equation, and quantitatively predict the ultra-high cycle fatigue life of high-strength titanium alloy welded structures with different electron beam welding defects. The invention establishes the ultra-high cycle fatigue life loss equation including the size parameters of electron beam welding defects through ultrasonic fatigue tests; it only needs to obtain the size of electron beam welding defects through metallographic section or non-destructive testing, and can quantitatively predict different electron beam welding defects Ultra-high cycle fatigue life of high-strength titanium alloy welded structures. This method avoids a large number of ultra-high cycle fatigue tests of electron beam welded joints, and can complete the evaluation of ultra-high cycle fatigue life, which has the advantages of simplicity, speed and economy.

Description

technical field [0001] The invention belongs to the technical field of non-ferrous metals, in particular to a method for predicting the ultra-high cycle fatigue life of a high-strength titanium alloy electron beam welded joint. Background technique [0002] High-strength titanium alloy has the advantages of high strength, light weight, high temperature resistance, corrosion resistance and excellent formability, and is widely used in aeronautical structures, aeroengine compressor blades, steam turbine blades and other fields. Titanium alloy structural components are often formed by electron beam welding, which can withstand high-frequency vibration fatigue loads during high-speed operation, and can withstand cyclic loads of up to 10 during long-term service. 9 Week times, that is, ultra-high cycle fatigue. This welding method has a high specific energy and a small heat-affected zone of the weld, but defects such as welding pores are still unavoidable, and ultra-high cycle fa...

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Problems solved by technology

[0003] For ultra-high-cycle fatigue of high-strength titanium alloy electron beam welded joints, ultra-high-cycle fatigue cracks initiate in welding pores, expand discontinuously at the nanoscale, and form fine-grained regions. Fatigue damage is a nonlinear damage feature, but the current nonlinear life The loss equation is mainly phenomenological and does not directly reflect the size of electron beam welding defects. Therefore, the current life model cannot accurately predict the ultra-high cycle fatigue life of high-strength titanium alloy electron beam welding structures.

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