采用TC4钛合金薄板防屈曲装置,在不同扭矩(1.5~2.5 N·m)和不同应变水平(0.25%~1.0%)下对SAPH440钢薄板试样进行拉压疲劳试验,研究了摩擦力对薄板试样疲劳寿命的影响,验证了防屈曲装置的适用性。结果表明:在以弹性应变为主导的低应变水平(0.25%)下,试样的疲劳寿命随摩擦力的增大而略微降低;在以塑性应变为主导的中高应变水平(0.5%~1.0%)下,试样的疲劳寿命随摩擦力的增大而增大;应变水平为0.25%,0.5%时试样裂纹扩展区中段疲劳辉纹间距均值分别为0.45,0.86 μm,随着应变水平继续增大,疲劳辉纹变得不明显,出现了较为明显的二次裂纹。

Tensile and compressive fatigue tests were carried out on SAPH440 steel sheet specimen with TC4 titanium alloy sheet anti-buckling device under different torques (1.5-2.5 N·m) and different strain levels (0.25%-1.0%). The effect of friction force on the fatigue life of the sheet specimen was studied, and the applicability of the anti-buckling device was verified. The results show that under the low strain level (0.25%) dominated by elastic strain, the fatigue life of the specimen decreased slightly with the increase of friction force. Under the medium and high strain levels (0.5%-1.0%) dominated by plastic strain, the fatigue life of the specimen increased with the increase of friction force. When the strain levels were 0.25% and 0.5%, the average distance between fatigue striations in the middle section of the crack propagation zone of the specimen was 0.45 μm and 0.86 μm, respectively. As the strain level continued to increase, the fatigue striations became less obvious, and more obvious secondary cracks appeared.