Xiufang CHEN
材料科学技术（英文）
Three main machining processes of large-diameter 6H-SiC wafers were introduced in this paper. These processes include cutting, lapping and polishing. Lapping causes great residual stresses and deep damage layer which can be reduced gradually with subsequent polishing processes. Surfaces prepared by mechanical polishing (MP) appeared a large number of scratches with depth of 5~8 nm. These scratches can be effectively removed by chemo-mechanical polishing (CMP). After CMP, extremely smooth and low damage layer surface with roughness Ra=0.3 nm was obtained. Atomic force microscopy (AFM) and optical microscopy were used to observe the surface morphology of samples and a high resolution X-ray diffractometer (HRXRD) was used for the crystal lattice perfection of the subsurface region. Changes of surface residual stresses during machining processes were investigated by HRXRD.
关键词:
6H-SiC
,
MP
,
CMP
,
roughness
姚雪蕾
,
袁成清
,
赵相宽
,
白秀琴
表面技术
doi:10.16490/j.cnki.issn.1001-3660.2017.06.005
目的 研究船体表面粗糙度及污损附着在不同航速下对航行阻力的影响.方法 参考船体粗糙表面条件下的阻力估算方法,并通过目检法对船舶污底分级,由船体附着的生物类型判断此时污损附着的严重程度.划分三种不同的船体表面条件,对应建立三种模型,采用计算流体力学(CFD)方法,使用FLUENT软件进行数值模拟.将仿真结果与经验结论进行对比,分析阻力的增长情况与阻力性质.结果 船体表面条件越差,增加的航行阻力越大.同一表面条件下,增加的航行阻力随航速的增大而增大.在粗糙度(包含轻度污底)和中度污底情况下,增加的航行阻力主要为摩擦阻力;重度污底情况下,增加的航行阻力不再以摩擦阻力为主,粘压阻力、兴波阻力所占比例会增大.结论 在重度污底的情况下,经验推荐的摩擦补贴系数已不适用于实际情况,数值模拟方法的计算结果可供参考.通过降低航速来减少增阻适用于任何表面条件.
关键词:
粗糙度
,
污底
,
船舶阻力
,
摩擦阻力补偿系数
,
FLUENT
,
数值模拟
