How to realize mechanical butterfly-like shell and design efficient construction details for resembling, posed problems and challenges to the design and construction of a large 3D printing work. Firstly, through analysis of the synergetic mechanism of butterfly-like morphology and structural mechanic of Hypar shell, digital design methods and adjusting modes were well studied. Secondly, based on the features of additive manufacturing, adaptive methods of unit division and construction were proposed and discussed. Moreover, changing modes of lights were tested through the combination of photoelectric numerical control and corresponding details design. As a result, not only the construction of 3D printing work of large scale butterfly-like shell, but also more than 100 new changing patterns of lights were realized.

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The brittle coal failure behavior under various axial strain rates from 10 À3 to 10 À2 s À1 is experimentally and numerically studied. The numerical microscale finite difference model is built on the accurate X-ray microcomputed tomography images, which provides a ground-breaking and bottom-up approach to investigate the effects of microstructure on coal failure under various strain rates. Experimentally, prior to loading, the coal sample is scanned, and the three-dimensional coal structure model is constructed. The microheterogeneous structures are incorporated in the model, which facilitates the deformation and failure mechanism analysis under different loading conditions. The results reveal that the microheterogeneous structures significantly affect the evolution of stress concentrations and deformation behaviors in the sample. The coal tends to fail in the shear mode before the peak strength, since the shear zone is created with high displacements. However, tensile failure ultimately controls the failure process after the peak strength. Notably, the strain rate dependence of coal strength is observed, and an empirical relationship is proposed to describe the dynamic strength of the coal under various loading strain rates. Importantly, the coal strengthens with an increase in strain rate. For brittle material, such as coal, the strength and failure mechanism are strain rate and microstructure dependent. The strain rate-dependent coal strength index (n) is found to be a dynamic parameter in the range of strain rate from 10 À3 to 10 À2 s À1, and this finding may extend the concept of strain rate dependence over a broader range of loading conditions.

a b s t r a c tAn elastoplastic damage model is developed for fractured porous media. The elastic-plastic response of stress-strain is captured by a bounding surface plasticity within the critical state framework, while the damage evolution due to hydro-mechanical effects is addressed using a continuum damage model that is distinguished from the existing models by accounting for the plastic hardening parameter, stress ratio, confining pressure and strain rate. The coupling between the elastic-plastic response and damage is established by accounting for the effects of plastic volumetric strain and the damage parameter on the hardening of the bounding surface. The model is applied to different rocks subjected to isotropic and deviatoric loading in drained and undrained conditions. A good agreement is obtained between the numerical and experimental results demonstrating the ability of the model to capture the essential features of deformation in fractured porous media.

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