Numerical simulation of multi-layer 3D concrete printing

This paper presents a computational fluid dynamics model fit for multi-layer 3D Concrete Printing. The numerical model utilizes an elasto-visco-plastic constitutive model to mimic the flow behaviour of the cementitious material. To validate the model, simulation data is compared to experimental data from 3D printed walls. The obtained results show that the numerical model can reproduce the experimental results with high accuracy and quantify the extrusion load imposed upon the layers. Such load is found to exceed the material’s yields stress in certain regions of previously printed layers, leading to layer deformation/flow. The developed and validated numerical model can assist in identifying optimal printing strategies, reducing the number of costly experimental print failures and human-process interaction. By doing so, the findings of this paper helps 3D Concrete Printing move a step closer to a truly digital fabrication process.

EFFECT RESEARCH OF SURFACE DEFORMATION IMPACT AND THERMAL TREATMENT AT MULTI-LAYER WELD DEPOSITION UPON MECHANICAL PROPERTIES AND POROSITY OF ALUMINUM ALLOY 1580

The experimental research of mechanical properties and porosity of samples made of experimental high-strength magnesium-scandium aluminum alloy 1580 obtained through the method of multi-layer weld deposition including the application of deformation strengthening and also the further thermal treatment is carried out. There is investigated the impact of layer-by-layer deformation strengthening with the further thermal treatment upon mechanical properties and porosity of the samples of experimental high-strength aluminum alloy 1580 having magnesium-scandium during multi-layer weld deposition. There are shown the values of mechanical properties and porosity of samples subject to modes of deformation strengthening and thermal treatment. A possibility of the impact of deformation effect and thermal treatment upon porosity and mechanical properties of products made of aluminum alloys containing magnesium-scandium obtained during multi-layer SMT weld deposition is checked up. According to the results of the investigation there are drawn conclusions: it is determined that for porosity decrease in metal deposited there are required higher values of efforts of the deformation impact and a weld deposition mode selection excluding product over-heating influencing porosity of metal deposited; thermal treatment impact upon porosity of the metal deposited is not defined; the samples obtained with the use of deformation impact and long annealing with the duration more than six hours have higher mechanical properties.

CALCULATION OF BENDING ELEMENTS OF WOOD AFTER THE ACTION OF LOW-CYCLE REPEATED LOADS ON THE CRITERION OF DEFORMATION DESTRUCTION

Existing norms of design for wooden constructions valid in different countries including Ukraine entirely disregard the effect of low-cycle repeated loadings during the operation of buildings and structures. The article deals with development of the bearing capacity computation of the bending elements manufactured from solid and glue-laminated wood exposed to repeated loadings in accordance with the deformation model.Equilibrium equations for computing the bending element made of wood after being exposed to repeated loadings are presented in the article. The deformation method is proposed for the computation of the rectangular wooden beams manufactured from solid and glued laminated wood with allowance for the occurrence of folds in the compression zone.The results of the research allow designing the solid and glue-laminated wooden constructions taking into consideration the possibilities of the material and peculiar features of the performance of the element, which in turn will allow choosing the cross-section of the elements of building structures more economically.On the basis of the study of the process of layer deformation by section height and the determination of the characteristics of the stress-strain state of these layers under the effect of repeated loading, it is possible to fulfill more accurate computation of the elements manufactured from wood at different stages of the stress-strain state through destruction.

Газофазная эпитаксия слоев AlN на темплейте AlN/Si(111), синтезированном методом реактивного магнетронного распыления

Epitaxial layers of AlN were grown on a Si(111) substrate using several sequential methods: reactive magnetron sputtering (up to a thickness of 20 nm), MOCVD (up to a thickness of 450 nm), and HVPE (up to a thickness of 2 microns).The formation of AlN by this combined method provides a significant reduction in layer deformation and suppression of crack formation.