Research On The Joint Performance Of Staple For Sofa Frame

Air nail connection is a relatively common connection method in sofa frames at present,but the use of air nails is quite different from conventional screw connection and tenon-and-mortise connection,and it is also different from other materials in the production process.The research on the key parts of the air nail connection nodes in the frame not only helps to strengthen the cognition of the use of air nails,thereby improving the mechanical strength of the nodes,but also provides a certain theoretical basis for the actual production and application of enterprises.Through the actual investigation of the factory of H enterprise and the collection of relevant research papers at home and abroad,this paper takes the common connection nodes and main stress methods in the sofa frame as the starting point,and studies the number of air nails,the length of air nails,the wood material,the air pressure The influence of the strength and the material change of the air nail itself on the tensile and shear strength of the joint,and the effect of the number of air nails on the tensile and shear strength of the joint was simulated and analyzed by finite element software,and the following conclusions were drawn:（1）Through factory research and literature research,it is found that the main damage forms of the sofa frame are:load-bearing wood fracture,multi-layer board cracking,multi-layer board with wood connection nodes fracture.Among them,the main problems existing in the use of air nails in the sofa frame:the number of air nails is messy,the angle of the air nails is messy,and the air gun air pressure lacks standards.（2）By studying the influence of the density change of the multilayer board on the tensile and shear strength of the joint,it is found that the density change has a high impact on the tensile strength,while the impact on the shear strength is small.The density of 0.59g/cm³of eucalyptus multilayer The tensile strength of the board is 21%higher than that of the poplar multi-layer board with a specific density of 0.51g/cm³,and 32%higher than that of the poplar multi-layer board with a specific density of 0.53g/cm³.Eucalyptus plywood is 12%lower and 10%lower than poplar plywood.The relational formula P=917N^0.389between the number of air nails and the tensile strength in this experiment is deduced;and the estimated equation P=4.6D^2.12N^3.7for the shear strength and material density and the number of gun nails.（3）In terms of the influence of the material change of the air nail itself on the mechanical strength of the joint,from the perspective of price,CY>XY>MT,MT is 16%cheaper than XY and 63%cheaper than CY,and MT>XY>CY from the yield strength of the material itself,From the test results of mechanical strength,the tensile strength of CY brand air nails is 7%higher than that of MT,25%higher than the maximum tensile strength of XY brand air nails,and the shear strength is 8%lower than that of MT,which is no different from XY.Significant differences.（4）In terms of the influence of the change of air pressure strength on the mechanical strength of the joint,it is found that the tensile and shear strength of the 30mm long air nail is the largest when the air pressure is 0.4MPa.After that,the mechanical strength will continue to decrease with the increase of the air pressure strength.When the air pressure is 0.4MPa,the tensile strength is 16%higher than that of 0.6MPa,and the shear strength is 16%higher.The tensile strength under air pressure is 3%lower than that at 0.6MPa,and the shear strength is 8%higher;the tensile strength of the 40mm air nail joint is not significantly different at 0.5 and0.6MPa air pressure.Compared with 0.4MPa air pressure,The tensile strength is increased by7%,and the shear strength is increased by 32%.Compared with the 0.75MPa air pressure,the tensile strength is increased by 12%,and the shear strength is almost the same.With the help of design expert software,the response surface analysis and derivation are used to estimate the equation,tensile strength equation:y=1380.89-9.5a+238.83b+70.75ab+5.17a²+6.17b²;shear strength equation:y=1691.33+88.67a+18.5b+162ab-159a²-26.5b².（5）The influence of the change of the number of air nails on the mechanical strength of the joint is analyzed through ANSYS finite element simulation,and it is compared with the experiment.In terms of tensile simulation,from the point of view of the damage situation,the main damage form of the finite element simulation is gas.The nails were pulled out,but in the experiment,except for the nodes with 1 or 2 air nails that were directly pulled out,the failure modes of the nodes with 3 or 4 air nails were all multi-layer boards were damaged.In terms of strength before tensile strength,it is found that when the number of air nails is 1,2,and 3,respectively,the finite element analysis results of the nodes are similar to the experimental results,but when the number of air nails is 4,the results are quite different;in the shear simulation In terms of failure mode,the main failure mode of the finite element simulation is nail bending,which is similar to the experimental results.In terms of shear strength,when the number of air nails is 1,2,and 3,the analysis results are similar to those of the experimental results.The experimental results are very similar,but when there are 4 nails,there is a big difference.Therefore,in the comprehensive tensile and shear analysis,the finite element can play an auxiliary role,and it can play a role in predicting the approximate range of the experimental results in 1,2,and 3 nails,but there will be a big difference in the prediction when there are 4nails.