Numerrical Model And Experimental Research On The Interactive Problem Of Aluminum Alloy Honeycomb Plate And Bars

In a single-layer aluminum alloy composite reticulated shell structure in where the aluminum alloy honeycomb plate participates in the joint work of the aluminum alloy bar,the convenient and reliable connection mode and the connection performance between the plate and the bar are the key factor in whether the plate-bar structure can truly work together.They are also the important assurance to ensure that its bearing capacity is significantly better than the general reticulated shell structure.According to the above,a “pipe tapping unilateral bolt” connection method is proposed to solve the problem that the nut can not be placed inside the aluminum alloy square pipe,which can achieve an effective “tight fit” connection between the plate and bar.Through the connection performance test and the FEM simulation analysis,the characteristics of force transmission,the failure mechanism of the connection performance,and the reasonable simulation methods of the working states between the plate and bar are grasped.The following main conclusions were obtained as following.(1)Through the test of the bearing capacity of the combination structure of three groups of 1.5m×3m aluminum alloy honeycomb panels and rectangular pipe,the mechanical characteristics and failure mechanism of this type of structure were ascertained.The test results show that the "wall tapping unilateral bolt" connection between the plate and the bar can ensure the effective force transmission between the plate bars under the action of the shear force.The two work together in good condition,and its failure mode is mainly manifested as: Shear failure of the connecting bolts and crushing damage of the bolt hole wall,and failure of the tripping due to insufficient thread strength under tension.According to the results measured of the three test-pieces,the connection performance of the connector directly determines the ultimate bearing capacity of the plate-bar structure.(2)Since the dimensions of the connecting bolts are much smaller than the connected honeycomb panels and aluminum alloy square tubes,to avoid the large scale of the finite element analysis model due to the division of the matching elements,the honeycomb panels must be equivalent to anisotropic homogenous board.In this paper,the experimental data of aluminum alloy bars and honeycomb panels is adopted to verify the reliability of the improved results of the existing equivalent simulation methods based on three equivalent theories.(3)In order to effectively simulate the complex contact state between the aluminum alloy honeycomb panel and the bar,a "simplified model"(according to the "sandwich panel theory",the aluminum alloy honeycomb panel is equivalently divided into shell elements without the physical modeling of the bolts for the coupled finite element analysis)and the "solid model"(the equivalent of a honeycomb plate and the bolts are divided into solid element for simulation with the hexahedral linear reduction integral)are relatively established for finite element analysis,considering the tangential and normal contact behavior of the honeycomb plate and bar which are in bolted joints.The analysis results show that due to the different types and quantities of units of the two models,the calculation workload varies greatly while the displacement and stress calculation results of the two models are not much different,and they are all close to the measured values of the test.Therefore,it is recommended that the engineering structure can be considered as the “simplified model” to analyze and design,and the friction coefficient at the connection boundary is taken as 0.25.(4)The connection performance test and finite element analysis results in this paper show that the “wall tapping unilateral bolts” between honeycomb panels and square tubes are mainly subjected to tensile and shear force.Through finite element parameter analysis of 30 sets of connection models of different thread depths and bolts diameters and spaces,the simplified calculation formula of bearing capacity of unilateral bolts is fitted,which provides a certain reference for future revision of the design specification of the connection performance of aluminum alloy honeycomb plate-bar composite structure.