Partial stretch behavior analysis of single crease origami unit

The deformation of single crease origami units under partial stretch loads along the crease extension direction is influenced by their plates’ bending stiffness. For their application, it is of great significance to analyze the non-uniform deformation pattern of origami units and clarify the efficiency of partial driving on global unfolding. In this paper, the unfolding behavior of single crease origami units under partial stretch is systematically investigated. From the bending phenomenon of paper models, a parametrical simulation analysis is performed to analyze deformation patterns and virtual crease distribution. Furthermore, the overall uniform motion efficiency of origami units with local driving is discussed, while the criterion of uniform unfolding motion of the crease is defined. The feasible ranges of partial load factors corresponding to single crease origami units with different initial crease angles are also clarified under the constraint of the required uniform motion range. Mechanical and kinematic models are also established based on equivalent rigid plate nonlinear crease elements and equivalent single-vertex six-crease patterns, which can accurately identify the deformation characteristics of the single-crease origami unit under partial stretch. Furthermore, the flattening analysis of derived single-vertex six-crease origami units and their arrays is also carried out to investigate the influence of sector angles and crease rotation stiffness. Two different decay characteristics are observed, corresponding to the fully flattened planar state and the non-fully flattened planar state, respectively. A motion snap that occurs before the fully flattened planar state is also identified. The findings can be regarded as the research basis for the complex mechanical behavior of origami structures composed of single crease origami units.