RETRACTED: The Nonlinear Compressive Response and Deformation of an Auxetic Cellular Structure under In-Plane Loading
Authors: Zhang Wei , Hou Wenbin , Hu Ping , Ma Zhengdong 
Published: March 2015

At the request of the Author, the following article Zhang, W, Hou, W, Hu, Ping and Ma, Z (2014) The Nonlinear Compressive Response and Deformation of an Auxetic Cellular Structure under In-Plane Loading Advances in Mechanical Engineering published 17 November 2014. doi: 10.1155/2014/214681has been retracted due to errors discovered by the authors. On Page 3, the definition of component force in Equation 4 is incorrect. (2) On Page 4, the definition of component force in Equation 11 is incorrect. Moreover this equation should not have parameterM(length of cell wall), because a mistake was made in the process of calculation. Because of the above reasons, the conclusion obtained from the mechanical model is incorrect and should instead state that the Elastic Buckling and Plastic Collapse are both yield modes of this structure (3) On Page 5, the FEA model used in this article is not appropriate, because the deformation of single cell is not homogeneous, which means that the geometrical non-linear effect on single cell model is greater. So in the actual whole structure we may not obtain the results that were described in Page 6 Paragraph 2. (4) The data in figures 8 (page 6) and 9 (page 7) is incorrect and the values of effective Young’s modulus and plateau stress are much larger than reasonable values. The definition of effective stress is wrong in the FEA model, which means the effective stress should be calculated by the total width of cell instead of length of horizontal cell wall. For example, in Figure 8, the plateau stress can reach 140Mpa, this is not reasonable because there are many holes in this cellular structure, and its mechanical properties should be much lower than material properties of cell wall. The reasonable plateau stress should be around 2Mpa. The authors takes responsibility for these errors and regret the publication of invalid results. The nonlinear compressive response and deformation of an auxetic cellular structure that has periodic negative Poisson's ratio (NPR) cell were studied through theoretical and numerical method. The in-plane deformation and process of absorbing energy of this NPR cellular structure were discussed. The relative density of NPR cell was determined by geometric parameters and a theoretical approach to the strength of NPR cell was carried out to analyze the failure process under in-plane compression. Thus, to prove the effective of unit cell mechanical model, the size effect of this NPR cellular structure was discussed. The simulations of two different NPR cellular structures under in-plane compression were generated and their effective properties, strain-stress curves, and absorbed energy were analyzed. It can be concluded that the NPR cell that has lower relative density may have better capability of absorbing energy with enhanced Young's modulus. Finally the parametric analyses related to relative density were presented with NPR unit cell model and a set of quasistatic compressive experiments was carried out, which can be used to reveal the nonlinear properties of NPR cellular structure and to prove the effectiveness of theoretical method.