The Bending Process Of Catalpa

Softening and drying stereotypes are key processes of solid wood bending. This study used ovata catalpa wood as the basic material, and explored softening effects of urea and water soaking ovata catalpa wood when it under microwave treatment. The influences of microwave processing time、wood moisture content and microwave power on the effects of ovate catalpa wood softening was discussed. A quadratic regression model was established with Response Surface Methodology based on single factor experiment, and the process was optimized. The bending properties of ovata catalpa wood was verifed under this optimization scheme. A seres of conclusion based on the experiment results and its analysis are as follows:1) When microwave power (P value) is530w, the bending performance index(h/r value) of urea and water soaking ovata catalpa wood reaches the maximum value, and when the value of P increased or decreased, the bending performance index value decreased. From the experiment result of softening performance determination, the expression of urea soaking ovata catalpa wood between P value and bending performance index is Y=-7X2+0.0008X+0.009-7.9E, and the correlation coefficient R2=0.9939; and the expression of water soaking ovata catalpa wood between P value and bending performance index is Y=-7X2+0.0005X+0.044-4.3E, the correlation coefficient R2=0.9535.2) With the increase of microwave treatment time (T value), the bending performance index(h/r value) of urea and water soaking ovata catalpa wood were both increased firstly, and then both decreased, when the microwave processing time is2min, both the two kinds material reach the best softening performance, and at that time the maximum bending performance index of urea soaking ovata catalpa wood is21%higher then water soaking one. From the experiment result of softening performance determination, the expression of urea soaking ovata catalpa wood between T value and bending performance index is Y=-0.0374X2+0.1383X+0.0662, correlation coefficient R2=0.9795; and the expression of water soaking ovata catalpa wood between P value and bending performance index is Y=-0.03X2+0.121X+0.038, correlation coefficient R2=0.9875. 3)The initial moisture content (M value) have a significant impact on the catalpa wood bending softening effect. When the initial moisture content is40%, the bending performance index(h/r value) of urea soaked material reaches the maximum value, increase or decrease the value of M, bending performance index will reduced. From the experiment result of softening performance determination, the expression of urea soaking ovata catalpa wood between M value and bending performance index is: Y=-0.0001X2+0.012X-0.072, the correlation coefficient R2=0.9764; when the initial moisture content is30%, the bending performance index(h/r value) of water soaked material reaches the maximum value, and the bending performance index change trends with M value of water soaked material is almost like urea soaking material. From the experiment result of softening performance determination, the expression of water soaking ovata catalpa wood between M value and bending performance index is Y=-5X2+0.0062X+0.041-8.2E, the correlation coefficient R2=0.9444.4) The results of response surface optimization analysis of urea soaked material softening process showed that:the softening performance the best under the condition that when the microwave processing time is2min, the wood moisture content is44%and the microwave power is530W. the experiment result of softening performance determination also showed that steel Strip has a significant impact on the quality of bending parts. Under the treatment of optimum microwave processing, the minimum bend radius ratio (h/r value) of bending parts under the condition of steel strip can reach1/6, and the yield of nearly get90%.the minimum bend radius ratio increase a lot compared with the condition that without using steel strip.5)In the drying stereotypes treatment process, process factors as the final moisture contents stabilization time and drying speed have a significant effect on the dimensional stability of bending parts. The experiment result of bending parts dimensional stability determination also showed that:When final moisture content of10%, the best assembly time is4h, the drying temperature is50℃, the rate of change of chord bending parts is ideal.