Abstract:A small sample bending fatigue test device was improved.Aiming at the low frequency, small amplitude and unaccurate vibration displacement acquisition data of the original test device, the best speaker caliber was determined, simulation analysis for the stress at the edge of the sample hole was done.The mixer with a pure power amplifier was used as a power system to replace the original test machine power source.The 24-bit highprecision USB data acquisition card was used to collect sample vibration displacement data more accurately.The finite element was used to analyze the relationship between the specimen gap and the stress at the edge.The optimal diameter of the loudspeaker was determined by continuous repeat test.The results show that the excitation frequency of the improved test device is increased from 260 Hz to 500 Hz, and the amplitude can be adjusted among 0~5 mm when the excitation frequency is 500 Hz;sample vibration displacement can be accurate to 0.000 01 mm;the best speaker caliber is 165 mm;the specimen gap stress is 1.65 times the edge.Therefore, the use of the test machine can short the test time of microbrittle material fatigue testing.