Abstract

During suction blow molding process, the extruded parison undergoes twisting deformation within the mold cavity, as the air drawing flow around the deforming parison exerts non-uniform shear stresses on its surface. This research is devoted in developing a fluid-structure interaction model for predicting parison deformation during suction blow molding process, with a specific emphasis on the suction stage. A fluid flow model, based on Hele-Shaw approximations, is formulated to simulate the air drag force exerted on the parison surface. The rheology of the polymer during suction is assumed to obey the K-BKZ integral viscoelastic model. The numerical results of this study allowed identifying a clear correlation between the twisting deformation undergone by the parison during the suction stage, also observed experimentally and the design parameters, namely, the air suction speed, the geometry of the duct mold cavity, and the parison/mold eccentricity.

Abstract

This work presents a numerical framework for long dynamic simulations of structures made of multiple thin shells undergoing large deformations. The C1-continuity requirement of the KirchhoffLove theory is met in the interior of patches by cubic NURBS approximation functions with membrane locking avoided by patch-wise reduced integration. A simple penalty approach for coupling adjacent patches, applicable also to non-smooth interfaces and non-matching discretization is adopted to impose translational and rotational continuity. A time-stepping scheme is proposed to achieve energy conservation and unconditional stability for general nonlinear strain measures and penalty coupling terms, like the nonlinear rotational one for thin shells. The method is a modified mid-point rule with the internal forces evaluated using the average value of the stress at the step end-points and an integral mean of the strain-displacement tangent operator over the step computed by time integration points.

Abstract

Within a 3D concrete printing process, concrete is still fresh and possible collapse may occur due to its own weight and lack of formwork. On the other hand, the mechanical characteristics of the material are continuously evolving due to hydration during curing. Withina predictive theory, the constitutive relation of the early age concrete is to be defined in rate form. In this contribution, and due to the soft nature of the problem at hand, a finite strainincremental viscoelastic modeling is adopted. A generalized Maxwell rheological model is used together with a Saint-Venant-like incremental elasticity. A parametric study is conducted on simulated slump-tests to highlight the abilities of the present framework. Clearly, the early age rheology and mechanical properties have a great impact on the buildability of the fresh concrete. A set of simulations is then given for the purpose of demonstration.