Effect of Layer Thickness on the Physical and Mechanical Properties of Sand Powder 3D Printing Specimens

Qing Xu,Xinzhe Wang,Changqing Ma,Lishuai Jiang,Qingjia Niu

doi:10.3389/feart.2021.763202

Abstract

The application of sand powder three-dimensional (3D) printing technology in the field of rock mechanics and mining engineering has tremendous potential, but it is still in the preliminary exploration stage. This study investigated the effect of printing layer thickness on the physical and mechanical properties of rock-like specimens with sand powder 3D printing. Quartz sand powder was used as the printing material, and the specimens were prepared with three different layer thicknesses of 0.2, 0.3, and 0.4 mm. Uniaxial compression tests with a combination of digital image correlation (DIC), acoustic emission (AE) and 3D microscope observations were performed to analyze the mechanical properties and failure patterns of the specimens during loading. Experimental findings showed that increasing the layer thickness from 0.2 to 0.4 mm would result in a decrease in the weight, density, uniaxial compression strength, and elastic modulus of the specimens. The stress-strain curve, deformation and failure patterns, crack growth process, and AE characteristics of the specimens with a layer thickness of 0.2 mm are similar to the AE characteristics of rock-like material, whereas the specimens with layer thicknesses of 0.3 and 0.4 mm deform like a ductile material, which is not appropriate for simulation of coal or rock mass. In future studies, rock-like specimens should be prepared with a small layer thickness.

Highlights

In the field of rock mechanics and engineering, experimental research is a fundamental methodology that is capable of revealing the mechanical properties and behaviors and providing important guidance for parameter calibration in analytical and numerical studies
Lu et al (2009) printed 3D network structures with alloy powder with different particle sizes and found that specimens with minimum particle sizes have high strength Vaezi et al (2011) investigated the influence of printing layer thickness and binder saturation on the mechanical properties of specimens with plaster-based powder, and the results showed that the layer thickness and binder saturation were negatively and positively correlated with the specimen strength, respectively
In the process of specimen printing, the amount of binder sprayed at each surface is the same, whereas T-0.2 sprayed 500 times, T0.3 sprayed 334 times, and T-0.4 sprayed 250 times, so the total ink jet is reducing with layer thickness increasing, resulting in the differences in physical properties

Summary

Introduction

In the field of rock mechanics and engineering, experimental research is a fundamental methodology that is capable of revealing the mechanical properties and behaviors and providing important guidance for parameter calibration in analytical and numerical studies. One of the most notable difficulties in rock mechanics and engineering is that rock differs from most other engineering materials in that it contains joints, which render its structure discontinuous. The presence of joints or other kinds of discontinuities of different scales (faults, fractures, cracks, bedding planes, etc.) has a dominant effect on the mechanical behaviors and stability of rock masses and hereby has a fundamental influence on rock engineering design. Because of the sedimentary effect of coal seams and other strata, the rocks surrounding coal mines are relatively weak and fractured compared to other underground engineering projects (Zuo et al, 2019). The stability of coal mine openings (preparation entries, roadways, chambers, etc.) has always been a major concern of researchers and engineers.

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