Fatigue tests with solid round bar specimens were carried out to investigate the effect of stress amplitude ratio on the axial-torsion fatigue failure of low carbon steel under a certain equivalent stress. The processing of surface short cracks initiation and propagation were recorded by replica technology. It is observed that all the crack propagation curves based on the criterion of dominant effective short fatigue crack (DESFC) clearly exhibits a similar oscillations tendency caused by the microstructure. In addition, the fatigue life, fracture angle and crack source vary with the value of stress amplitude ratio. Hence, a short crack model incorporating the effects of stress amplitude ratio was used to simulate the short crack growth rate, and the model can directly estimate the biaxial short cracks growth rate under different stress amplitude ratios according to the experimental data of uniaxial short cracks. A good agreement is achieved between simulation results and experimental data.
To study the compressive mechanical properties of a new type of brazed aluminum honeycomb plate (BAHP), tensile tests on single- and brazed-cell walls as well as compression tests in the out-of-plane, in-plane longitudinal, and transverse directions were conducted. Compared to the material properties of a traditional glued aluminum honeycomb plate (GAHP), those of the single- and brazed-cell walls of the BAHP are entirely different. Therefore, their characteristics should be considered separately when performing theoretical and simulation analysis. Under out-of-plane compression, the core of the BAHP did not debond, owing to its higher strength than that of the GAHP. In comparison, under in-plane compression in the longitudinal and transverse directions, the load–displacement characteristics, ultimate load, and failure modes also differed, and there was no large-scale cracking. Considering the characteristics of the BAHP, a strength prediction method was proposed. The simulation results demonstrated that the model built based on the new method was highly consistent with the experimental results.