Wood heat treatment has increased signifi- cantly in recent years and is still growing as an industrial process to improve some wood properties. We studied the change of swellingand surface roughness of common alder ...Wood heat treatment has increased signifi- cantly in recent years and is still growing as an industrial process to improve some wood properties. We studied the change of swellingand surface roughness of common alder （Alnus glutinosa （L.） Gaertn. ssp.glutinosa） and wych elm （Ulmus glabra Huds.） woods after heat treatment at two different temperatures and durations. The temperatures were 180 and 200 ℃ and the durations were 2 and 4 h. A stylus method was employed to evaluate the surface char- acteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber on the wood surface. Four main roughness parameters, mean arithmetic deviation of profile （Ra）, mean peak-to-valley height （Rz）, root mean square roughness （Rq）, and maximum roughness （Ry） were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Swelling and surface roughness parameters （Ra, Rz, Ry, and Rq） differed significantly for two temper- atures and two durations of heat treatment. Swelling and surface roughness values decreased with increasing treat- ment temperature and treatment times.展开更多
考察脉宽t ON、峰值电流I IP、脉冲间隙调整MA、脉冲间隙t OFF对PDC加工精度和加工效率的影响.通过正交试验确定其最佳电加工工艺参数为:t ON 2μs、I IP 10 A、MA 1倍和t OFF 4μs,其加工时间为458 s;加工后YG层的表面粗糙度R a1为1.04...考察脉宽t ON、峰值电流I IP、脉冲间隙调整MA、脉冲间隙t OFF对PDC加工精度和加工效率的影响.通过正交试验确定其最佳电加工工艺参数为:t ON 2μs、I IP 10 A、MA 1倍和t OFF 4μs,其加工时间为458 s;加工后YG层的表面粗糙度R a1为1.04μm,PCD层的表面粗糙度R a2为0.59μm.在此基础上,通过单因素试验和分割试验进一步考察PIKADEN高压脉冲控制P P和高压辅助电源H P对电加工精度和效率的影响.结果发现:当P P设定为11、H P设定为013,即追加1.5 A高压辅助电流时,PDC的最佳电加工工艺参数为:t ON 4μs、I IP 10 A、MA 1倍和t OFF 4μs,其加工时间最短,为130 s;加工精度较高,加工后YG层的R a1为1.30μm、PCD层的R a2为0.56μm.与正交试验确立的最佳工艺参数相比,其加工精度相差不大,但加工效率提高了3.5倍.展开更多
文摘Wood heat treatment has increased signifi- cantly in recent years and is still growing as an industrial process to improve some wood properties. We studied the change of swellingand surface roughness of common alder （Alnus glutinosa （L.） Gaertn. ssp.glutinosa） and wych elm （Ulmus glabra Huds.） woods after heat treatment at two different temperatures and durations. The temperatures were 180 and 200 ℃ and the durations were 2 and 4 h. A stylus method was employed to evaluate the surface char- acteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber on the wood surface. Four main roughness parameters, mean arithmetic deviation of profile （Ra）, mean peak-to-valley height （Rz）, root mean square roughness （Rq）, and maximum roughness （Ry） were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Swelling and surface roughness parameters （Ra, Rz, Ry, and Rq） differed significantly for two temper- atures and two durations of heat treatment. Swelling and surface roughness values decreased with increasing treat- ment temperature and treatment times.
