Joints Properties Of Double Dowel Of Medium Density Fiberboard(MDF)Components

This paper has discussed the effects of dowel diameter,the tolerance parameter between dowel and mortise,the center distance of two dowels and the curing time of adhesive on joints properties of 18mm MDF components which are jointed by two dowels.By finite element analysis on ANSYS,the results are more credible,and obtaining the following results:(1)When the dowel diameter(R)values 10mm,the anti-pull force achieves the maximum value namely 1573.6N;and the ultimate flexural strength of T-junctions and L-junctions respectively achieve the maximum value namely 250.28N and 214.51N.However,the components joints showed severe damage when R values 10mm,and it's best when R values 8mm.By testing experiments,we obtain the relational expression between R and the ultimate pullout capacity(P):P=159.77R+11.057;the relational expression between R and the ultimate flexural strength(P):in the T-junctions,the expression is:P=30.7R-58.21;in the L-junctions,the expression is:P=25.488R-41.047.(2)When the curing time(T)values 168h,the ultimate flexural strength of T-junctions and L-junctions respectively achieve the maximum value namely 194.72N and 166.22N.It is suggested that the curing time in practical production should be longer than 72 h.By testing experiments,we obtain the relational expression between T and the ultimate flexural strength(P):in the T-junctions,the expression is:P=-0.003T2+0.6837T+164.17;in the L-junctions,the expression is:P=-0.0032T2+0.7467T+132.02.(3)When the tolerance parameter between dowel and mortise(C)values 0.2mm,the anti-pull force achieves the maximum value namely 1603N;and the ultimate flexural strength of T-junctions and L-junctions respectively achieve the maximum value namely 207.58N and 176.73N.However,it is recommended that clearance fit is better in production practice with a relatively stable mechanical structure and a crackless surface.What's more,it's difficult to assemble the components when C values greater than or equal to 0.1mm.By testing experiments,we obtain the relational expression between C and the ultimate pullout capacity(P):P=-3674.8C2+1346.6C+1440.8;the relational expression between C and the ultimate flexural strength(P):in the T-junctions,the expression is:P=-479.5C2+186.68C+190.05;in the L-junctions,the expression is:P=-324.61C2+133.46C+163.72.(4)When the center distance(D)between two dowels values 32mm,the anti-pull force achieves the maximum value namely 1603N;and when 48mm,the ultimate flexural strength of T-junctions and L-junctions respectively achieve the maximum value namely 194.72N and 166.22N.Besides,it is also proved that 48mm is the best distance by the finite element analysis on ANSYS.The dowels should be far away from the weak edge of components and the center distance should be less than 80mm.By testing experiments,we obtain the relational expression between D and the ultimate pullout capacity(P):P=-0.9599D2+49.429D+999.58;the relational expression between D and the ultimate flexural strength(P):in the T-junctions,the expression is:P=-0.0278D2+2.7303D+126.22;in the L-junctions,the expression is:P=-0.026D2+2.4823D+107.97.(5)By testing experiments,it is concluded that L-junctions show more severe damage than T-junctions,while the T-junctions have a relatively stable structure and a better flexural strength.It is recommended that we choose T-junctions as far as possible during the actual production and processing,so that furniture will be more stable and durable.