MESHFREE VISCOELASTIC MODELING: TOWARD NUMERICAL SIMULATION OF PRINTING CONCRETE STRUCTURES
Open Access
- Author:
- Chen, Guang
- Graduate Program:
- Civil Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 02, 2019
- Committee Members:
- Michael Charles Hillman, Thesis Advisor/Co-Advisor
- Keywords:
- Reproducing Kernel Particle Method
viscoelastic modeling
Meshfree methods
3D printing - Abstract:
- The conventional way of construction in building industry has many disadvantages, for example, the environmental pollution, massive energy consumption, less customization, and the intense human labor involved. A new, more efficient way of manufacturing construction materials could reduce time, cost and labor intensity, while providing design freedom for complex architectural forms. Towards this end, three dimensional (3D) printing, or additive manufacturing of concrete structures offers great potential. This technology however is still in its relative infancy, and further research is needed in order to bring this technology to the market. Specifically, the materials aspect of 3D printing pose many open research questions, such as rheological properties of the concrete that enabling effective pumping and printing, while also hardening quickly enough to support the weight of subsequent layers. In order to address these questions, two approaches can be employed: experiment and mathematical modeling. While an experiment approach alone is time consuming and costly, numerical simulation properly validated with experiments offers a far less costly and more effective alternative. To numerically model the behavior of concrete at fresh or solidified state, a viscoelastic constitutive law for both small-strain and finite-strain are introduced based on the generalized Maxwell model. In the solidified state, a small strain version of the viscoelastic constitutive relation can be used to model phenomena like stress relaxation and creep. While for fresh state mixture, the large strain version can model the finite deformation present in the deposition process, and interface evolution in 3D printing. However, careful selection of a numerical framework is necessary, since in the traditional finite element approach, large deformations can cause mesh distortion and entanglement, and topological changes in the domain (free surface formation, closure) require computationally intensive remeshing. Meshfree methods on the other hand, do not require mesh and can deal with these aforementioned problems easily. A numerical framework based on the meshfree reproducing kernel particle method (RKPM) is developed in this work to model the deposition process. Several numerical examples are tested to verify the developed computational framework. It is observed that the numerical results agree well with reference results, which indicates a strong potential for the effectiveness of the numerical framework for viscoelastic modeling of extremely large deformation problems such as deposition of concrete.