Reasonable Design And Finite Element Analysis Of Small-diameter Finger Jointed Plates

In order to make high-value-added use of a large number of thin-cut timber and small-diameter timber in China’s artificial fast-growing forests,realize the large-scale use of small timber,and ease the supply and demand pressure of high-quality timber.In this paper,for the purpose of horizontally joining large-scale panels with small diameter timber,Eucalyptus(Eucalyptus)in fast-growing timber is used as a raw material,and its mechanical properties are layered to establish a more accurate log model;the finite element analysis method is used The material was subjected to LS-DYNA display dynamic fracture simulation to determine its fracture position and flexural strength.Select the horizontal fingering method that meets the requirements to design reasonable finger parameters,and use ABAQUS finite element software to load simulation experiments on 36 different finger shapes.Analyze the influence of finger shape,material properties,plate length,combination method,etc.on the bending strength of finger joint materials,and preliminarily infer the finger joint fracture mechanism.According to the fracture mechanism,the finger shape is optimized,and the ABAQUS software is used to perform static loading simulation comparison experiments on the finger joint materials before and after optimization to verify the accuracy of the fracture mechanism.The main research results include the following aspects:(1)There is a difference in the Young’s modulus of the grain along the radial direction of the wood.After the stabilization treatment,the diameter of the eucalyptus small diameter 144 mm is found to still exist;the difference still exists;the Young’s modulus becomes larger along with the increase of the radius,the heart 30.6% difference from the edge.(2)In the LS-DYNA display dynamics finite element analysis software,using * MATORTHOTROPIC＿SIMPLIFIED＿DAMAGE(* MAT＿221)simple failure anisotropic constitutive model,using the failure strain of the material in the X axis direction as the failure criterion,the finger joint material is broken Simulation calculations were conducted;it was found that the flexural capacity of the eucalyptus small-diameter finger joint plates from strong to weak is as follows: longitudinally long feather type> longitudinally long embedded type> transversely wide embedded type> transversely wide airfoil.The ultimate reaction force of the indenter,that is,the failure load is: 2260 N,1610 N,637 N,and 571 N,and the fracture first occurs at the root of the central convex finger of the span.The fracture position is the same as the experimental result,which proves that the model has a good correlation,and this simulation method is feasible.(3)The ABAQUS static finite element simulation software was used for loading experiments on 36 kinds of finger joint plates.The cloud map generated by the software and the stress and strain values of nodes in each layer of the overall model were used to predict the failure mechanism of the finger joint material: Occurrence can hinder stress transmission,and stress concentration is easy to occur in the gap,and the size of the gap has little effect.Moderate gaps can hinder stress transmission while reducing deformation.(2)The more symmetrical the two plates for finger jointing,the more uniform the stress distribution.When the two plates are different in length,the stress concentration position tends to the center of the two plates rather than the finger joint position.(3)At the finger joint position,the staggered connection of two materials with different properties can effectively hinder the transmission of stress.(4)The stress of finger joints is inversely proportional to the amount of deformation.To avoid damage to the overall balance and dimensional stability,it is not advisable to select the outermost or innermost wood to point to each other.Combining the difference of wood’s own elastic modulus and the fracture mechanism,two combinations with the best overall performance are obtained.(4)Moderately change the angle of the overall finger shape of the finger joint material,make the gap in the fitting position symmetrical,and change the tenon shoulder to a 45-degree miter joint,which can save the processing cost and make the shape of the finger joint plate.The maximum stress experienced is reduced by nearly 30%.