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Abstract:The dynamic fracture behaviour of cylindrical shell preformed by localized melting technology was studied experimentally, and the microstructure and performance of melted layers were also analyzed in this paper. The results reveal that the microstructure of melted layer is predominantly needle type and refined martensite by the melted-solidification process. With the increase of hardness and decrease of impact energy absorbed, the embrittlement tendency of localized melting sample is obviously. Compared with natural fragmentation, the fragments of shell after melting are more regular, and the proportion of effective fragments is high. Due to the sensitivity of shear bands of melted layers, fracture can easily take place along the melting trajectory subjected to internal explosive loading.

Using a nondestructive testing method based on hysteresis behavior, the structural-mechanical dependence of the coercive force of 35CrMo steel components was compared with that of standard specimens. As described in the magnetic Jiles–Atherton model, the magnetic coercive force of the cylinders was inversely proportional to the grain refinement, which was validated by means of metallographic examination and hardness tests. Simultaneously, this study presented an experimental validation by destructive testing for determining the relationship between the measured magnetic parameter and the property of concern and a linear correlation between coercive force and hardness. These observations provide a method to quickly and nondestructively evaluate the mechanical properties of steel components.

The volume absorptions and the interface absorptions of SiO2 and HfO2 single layers are studied using the thermal lens method. Based on the fact that electric field distributions in single layers are different when the films are illuminated from the coating side and substrate side, an equation is given to calculate volume and interface absorptions of single layers. Half wave HfO2 and SiO2 single layers are prepared by electron beam evaporation method. With the absorption data measured by thermal lens technique, we separate the volume absoption from the interface absorption for these two single layers. The results show that interface absorption is non negligible when the absorption of film approaches to a ppm level. Additionally, the HfO2 single layer shows bigger volume and interface absorptions than SiO2 single layer.