To simulate the crack growth and study the catastrophic fracture mechanisms of metal films, a computational methodology is developed to simulate the failure process from damage initiation to crack growth and eventually to rupture. In the computational methodology, a procedure is developed based on beam lattice model for considering the coupling interactions among damage and crack evolution. To verify the effectiveness of the developed computational methodology, fracture process of two copper film specimens were simulated and compared with the corresponding experimental results. The results show that the developed methodology is effective, and can be used to simulate the catastrophic fracture process of metal films. From the simulation results, we can find out that the fracture of metal films with initial flaws belongs to brittle fracture, and the regular lattice model can affect the crack path prediction, and random and irregular lattice model is more suitable to simulate crack growth in the developed computational methodology.

In order to enhance the wear resistance and toughness of the material surface, Ni-P-Al$_2$O$_3$-PTFE nanocomposite coatings were prepared by pulsed jet electrodeposition technology, and the effect of duty ratio on the comprehensive properties of the nanocomposite coatings was studied. The surface morphology, microstructure and mechanical properties of the nanocomposite coatings were analysed by X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer and nanoindenter. The results show that compared with direct-current deposition, the application of pulse current plays a positive role in the preparation process of jet electrodeposition, and with the increase of the duty ratio, the surface quality and comprehensive properties of the nanocomposite coatings first improve and then reduce. When the duty ratio is 40%, the surface morphology and particle distribution of the composite coating are uniform and dense, the content of Al and F elements reaches the maximum value of 1.12 and 0.76 wt%, the microhardness reaches the maximum value of 540 HV, the average friction coefficient and wear scar width reach the minimum value of 0.1205 and 125.04 lm, the elastic recovery ratio ($h_e$/$h_{max}$) reaches the maximum value of 0.40, and the ratio of microhardness to Young’s modulus (H$^3$/E$^2$) reaches the maximum value of 0.057. At this point, the nanocomposite coating exhibits excellent wear resistance and toughness. The development of this work will promote the application of nanocomposite coatings in the field of material surface protection and strengthening.