Research On The Compressive Strength Of Corrugated Box Based On The Theory Of Structural Stability

As an important load-bearing container in logistics transportation,the consumption of corrugated box has always been the first of all kinds of packaging products.Among the various benchmarks of inspecting and evaluating the quality of corrugated boxes,compressive strength is the most important technical indicator.At this stage,the calculation of compressive strength is based on empirical formulas.There are few theoretical studies on the compressive process of carton boxes.On the basis of the structural stability theory,studying the deformation and stress of cartons is helpful to find the carton instability mechanism and is of great significance to optimize the carton structure.At the same time,there are many researches on methods to improve the compressive strength,but most of them increase the fabrication costs and storage costs.It is difficult to balance economical expenditure and the compressive strength of cartons.Therefore,it is significant to find a new improving method that does not increase the cost of making boxes.In this paper,the 0201 box was used as the research object,and the compressive strength of the corrugated box was studied with three methods of theoretical calculation,experiment,and finite element analysis.The buckling equation and the finite element analysis model were established,and a new method to enhance the compressive strength of the box was proposed.The main research contents are listed as follows:(1)Based on the theory of structural stability,a differential equation for buckling of corrugated boxes was established.In this paper,the orthotropic corrugated board was equivalent to an isotropic sheet and the functional equation of the corrugated board was derived with the energy method.The differential equation for buckling of the corrugated box was established,and the critical buckling load of the box was calculated.Through these,a new method for calculating the compressive strength of a carton was derived,which provided the basis for the theoretical study on the compressive strength of the corrugated carton.(2)The performance parameters of paper and paperboard were obtained by experiments.Tensile test of corrugated medium was carried out,and the elastic parameters of corrugated cardboard were calculated.The edge crush test,edgewise crush test and bursting test were performed to obtain the parameters of the board,which laid the foundation for the following theoretical calculation and finite element analysis.(3)The effect of indentation shapes on the compressive strength of corrugated boxes was experimentally studied.By analyzing the I-shaped deformation of the carton after the compression test,rhombus indentation cartons,one-line indentation cartons,unclosed rhombus indentation cartons,vertical-line indentation cartons,triangle indentation cartons,and cross indentation cartons were designed inside the carton.The compression tests were carried out respectively,and the test results were compared with the non-indentation cartons.The result showed that the compressive strength of the carton was affected by the indentation on its sides.The effect of different indentation shapes was various,among which rhombus indentation and cross indentation had the greatest effect.Rhombus indentation provided a significant enhancement with an increase of about 10%,while the cross indentation was close to the deformation track when cartons fail,which aggravated the deformation of the carton and reduced the compressive strength(48%).Based on these,it is concluded that rhombus indentation improved the compressive strength of corrugated box by hindering the original deformation trend of the box.A new method to enhance the compressive strength of corrugated box was obtained without changing the appearance of the carton,increasing the cost of raw materials and additional process cost.That is of great significance on production.(4)The buckling load of corrugated box was analyzed by finite element method.The finite element models of the non-indentation carton and rhombus indentation cartons were established.The nonlinear static analysis,eigenvalue buckling analysis,and post-buckling analysis were performed to obtain the critical buckling load of non-indention and rhombus indentation carton.The comparative test results proved the reliability of the two models and verified the feasibility of corrugated box buckling analysis.In conclusion,based on the structural stability theory,the buckling differential equation of corrugated cardboard was established,the critical buckling load of the carton was obtained,and a new idea for the theoretical calculation of the compressive strength of the corrugated box was provided.At the same time,a new method to enhance the compressive strength of corrugated boxes was proposed without changing the appearance of the carton,increasing raw material costs and extra process costs in the carton manufacturing process.That is beneficial to the practical application of carton boxes.