Fatigue crack growth behavior and mechanism of closed‐cell PVC foam

The applicability of linear‐elastic fracture mechanics parameters (ΔK and K_max), elastic–plastic fracture mechanics parameter (ΔJ), and time‐dependent fracture mechanics parameter (C*) to characterize fatigue crack growth (FCG) rate of closed‐cell polyvinyl chloride foam was investigated in the present work. The effect of stress ratios (R = 0.1 and 0.4) on FCGs was observed when the ΔK, K_max and ΔJ were used as fracture mechanics parameters. As a fracture mechanics parameter that combines ΔK and K_max, the K* successfully characterized FCGs (da/dN) at R = 0.1 and 0.4. While, a time‐dependent fracture mechanics parameter (C*) successfully correlated da/dt of creep crack growth (CCG) test, but it failed to correlate da/dt of FCG tests. The FCGs at both R = 0.1 and 0.4 were cyclic dependent, while the CCG was time dependent. For cyclic‐dependent crack growth, the interaction between polymer‐chain scission and small scale crack‐tip blunting was the main mechanism, whereas the interaction between polymer‐chain pullout and large scale crack‐tip blunting dominated fracture process for time‐dependent crack growth. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Microstructure and Mechanical Properties of Resistance Spot Welding Joints of Carbonitrided Low-Carbon Steels

Metallurgical and Materials Transactions B - Carbonitrided low-carbon steels are resistance welded in various engineering components. However, there are no reports on the microstructure and...