Structural components in the fields of aviation,aerospace,weapons,and energy are often subjected to repeated impacts of small loads(or low energy).This type of load is different from the single-pulse impact of high energy and the conventional low-strain-rate fatigue,which is called impact fatigue.Because the energy-based impact fatigue test methods can only detect the relation between impact energy and fatigue life,the industrial application of impact fatigue test results in structural design and perform-ance evaluation has been limited.Therefore,this paper focuses on exploring a new impact fatigue loading method.First,based on a brief review of the development of existing impact fatigue test methods,this pa-per affirms the superiority of the stress wave method based on the Hopkinson bar principle,and raises the problem of non-constant amplitude loading in impact fatigue tests.The waveform generated by the Hop-kinson bar is controllable and measurable,which is beneficial to realizing constant-amplitude cyclic load-ing.Then,three impact fatigue loading techniques(namely the one-wave,two-wave,and three-wave techniques)based on the Hopkinson bar are proposed.The feasibility of these methods is verified through experiments,focusing on studying whether there is a non-constant amplitude loading problem caused by secondary loading.The three-wave technique is found to be the most effective impact fatigue loading meth-od because it can achieve constant amplitude loading and obtain comprehensive test data.Finally,a con-stant-amplitude dynamic shear fatigue test method is developed using the three-wave technique.Impact fa-tigue performance tests are carried out on the TC4 titanium alloy.The test loading frequency is 0.1 Hz,and the test strain rate ranges from 6800/s to 8400/s.It is proved that this method can realize dynamic shear fatigue testing of metal materials at the strain rate level of 103/s.This study provides a new idea for the constant-amplitude impact fatigue test.By changing the forms of the specimen and the loading bars,the impact fatigue loading in other loading modes(such as tension,compression,etc.)can also be real-ized.
impact fatigueHopkinson barstress waveconstant amplitudedynamic test techniques
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