基于STEP-NC的CAD/CAPP/CAM/NC集成系统研究

介绍以ISO14649中STEP-NC为基础的集产品设计、工艺设计、加工制造为一体的新CAD/CAPP/CAM/NC体系结构,研究联结产品设计和STEP-NC加工制造的工艺设计步骤,着重分析设计特征和制造特征的转换、制造特征分解、零件工艺信息模型及制造特征排序的机制。在Pro/E设计特征系统的支持下先进行CAD设计,然后通过Pro/TOOLK IT提取制造特征,建立零件工艺信息模型,再根据特征组工艺库、知识库和制造资源库对工艺方案进行整理,最后生成STEP-NC文件。     

并行设计思想在开发CAPP中的应用

探讨并行设计环境下基于特征模型的工艺设计过程,提出通过关联特征的约束推理和特征分组,实现加工工艺方案优化的方法,分析引起产品制造问题的原因,提供产品设计上的改进意见,或对设计知识规则进行更新,实现产品设计与工艺设计的双向动态控制和并行求解。     

基于产品特征表达的集成化制造系统的研究

提出了一种并行工程环境下基于特征表达的产品设计和制造的集成化方法。该系统提供了用于工艺规划和可制造性评估的工艺知识库,可以被产品设计的各个阶段所共享,能够确定加工特征组合和加工顺序安排。还提出了一种确定多加工方向的加工特征组合方法,用于加方向的合理选择和特征集合的最少化,获得最优化的加工效率。另外还探讨了特征干涉对加工效率和加工质量的影响,提出了新的特征干涉分类、解决方法和特征干涉条件下加工效率的优化算法。     

自定义加工特征的船用柴油机箱体件CAD/CAPP/CAM集成系统

为解决当前船用柴油机箱体类零件设计制造集成度不高、信息传递不顺畅等问题,提出基于自定义加工特征的方法来构建此类零件的CAD/CAPP/CAM集成系统。该方法依据成组技术和知识工程的原理,根据其形状特点和刀具轨迹形式将零件的各个加工特征进行分类,构建自定义加工特征库。在加工特征表述中,使用属性和标注进行表示,可实现基于加工特征的集成模式下的工艺决策和数控编程。采用自定义加工特征方法能够大大减少人工交互操作,提高工艺决策和数控编程的准确性和自动化程度。     

传动箱体零件YRX-CAD/CAPP系统特征工艺模块设计

针对传动箱体零件工艺设计的复杂性,提出基于特征工艺实例的工艺设计方法,在进行特征造型的同时,快速生成特征加工链,实现CAD/CAPP集成。     

基于设计特征的机电产品低碳设计方法

为支持在产品设计阶段进行生命周期碳足迹评估以及设计方案低碳优化,提出一种基于设计特征的产品低碳设计方法。构建产品设计方案特征表达模型,来表征与产品生命周期碳足迹相关设计信息;通过分析产品设计特征与生命周期碳足迹的关联映射关系,提出基于设计特征的产品碳足迹评估方法;建立基于差分算法的低碳优化模型,以生命周期碳足迹最小为目标优化设计特征,获取低碳性能最优的设计方案;以某冰箱作为研究对象进行低碳设计,验证所提方法的可行性和有效性。     

基于CAD/CAM技术切削刀具加工辅助工艺系统开发

分析了切削刀具加工工艺流程,确定了切削刀具加工辅助工艺设计软件的特征与功能。根据工艺设计软件的特征与功能,进行了加工工艺卡的编制与操作。建立了各类材料库、机床库、刀具库、切削用量库、设计和制造特征数据库等,解决了产品技术准备阶段的信息集成与共享问题,实现了工艺卡自动生成。     

面向设计制造的船用柴油机零件全三维数字化定义研究

基于全三维的数字化定义是产品设计制造一体化的发展趋势,针对船用柴油机零件结构复杂等特点,实施全三维数字化定义方法.采用基于特征的三维标注技术和数据管理技术,同时将设计信息、加工制造信息和工艺信息依据制造工序进行合理组织与管理,置于三维软件平台中.在制造时,直接在三维模型上识别加工制造信息和工艺信息,摆脱二维图纸束缚.实验表明,采取该方法可以实现基于全三维模型的统一数据源,满足设计制造对全三维数字化模型的要求.     

面向CAD/CAPP/PDM系统的数据集成

为了解决传统工艺设计过程中,零件工艺特征信息获取效率低的问题。提出了在产品设计BOM的基础上构建面向自制件工艺的扩展设计BOM。定义了扩展设计BOM的信息结构模型和数据结构模型,并提出了工艺特征信息的标注和提取方式。     

并行工程下CAPP工艺决策加工元模型研究

提出了面向并行工程下产品设计的ＣＡＰＰ工艺决策加工元模型,并讨论了基于该模型的零件加工工艺性分析问题。应用该模型、可以将工艺决策与产品设计有机结合且符合工艺设计分阶段、分层次,从局部到全局,从主要到次要的渐进循环规律。     

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites

The domain structures of Zn₃B₇O₁₃Cl, Zn₃B₇O₁₃Br and Zn₃B₇O₁₃I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 °C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as‐grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X‐ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.     

Cylindrical specimens for KIC of rocks

Stress intensity factors for pairs of diametrically opposite radial cracks on the inside of a jacketed pressurized hole in a thick cylinder have been calculated by using finite element technique. Burst tests on thick cylinder rock samples under above conditions have been performed and the K_IC values for Antrim Shale and Limestone determined. The method is very convenient for rocks whose samples are often available in form of cylindrical bars drawn as cores from underground drilling.     

GT/CAD/CAPP/PDM/ERP系统集成研究

研究ETO生产方式下以成组技术为基础的CAD/CAPP/PDM/ERP的集成方法,包括面向CAD/CAPP/PDM/ERP的集成的成组信息编码,基于成组编码的CAD/PDM集成、CAPP/PDM集成和PDM/ERP集成.提出了基于成组技术的CAD/CAPP/PDM/ERP集成框架,研究了贯穿于CAD、CAPP、PDM与ERP系统的统一的成组编码方案和信息编码方案.     

基于太赫兹光谱的人参和西洋参鉴别

为了快速区分人参和西洋参,依据两者所含的人参皂苷在太赫兹波段具有不同指纹光谱,提出了一种基于人参皂苷的太赫兹光谱鉴别人参和西洋参的方法。采用MATLAB软件识别人参和西洋参的太赫兹光谱,同时根据太赫兹光谱特征并通过标准的主成分分析(PCA)区分出人参、西洋参。实验结果表明,基于太赫兹光谱的主成分分析可精确区分出人参、西洋参,并且还可以应用于其他类似物质的区分中。     

Analysis of the Rk surface roughness parameter proposals

European manufacturers have proposed a set of surface roughness parameters based on an examination of the variation in slope of the bearing ratio curve of a surface profile. It is shown, that the proposed procedure provides no useful information, and indeed is misleading, since the bearing ratio curve of even a normally-distributed random surface profile exhibits the expected variation in slope when plotted on rectangular coordinates. On the other hand, the desired information is readily obtained by a similar examination of the cumulative height distribution of a surface profile (the unity complement of the bearing ratio) when it is plotted on normal probability coordinates.     

永磁同步电机积分滑模观测器控制

对永磁同步电机观测器控制进行研究,针对传统滑模观测器存在控制精度低、系统抖振较大的不足,设计了一种永磁同步电机积分滑模观测器控制。积分滑模控制具有控制精度高、系统抖振小的特点。积分滑模观测器可以有效提高电机控制精度,增强控制系统抗干扰能力。采用饱和函数代替符号函数进行滑模控制律设计,降低控制系统固有抖振,使滑模控制动态性能提高。通过仿真验证了积分滑模观测器控制策略的可行性。     

Characterization of cast Al86Mn3Be11 alloy

An Al₈₆Mn₃Be₁₁ alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be₄AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be₄AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al₅₂Mn₁₈Be₃₀, containing an appreciable amount of Be. The average composition of the hexagonal phase was Al₆₆Mn₂₁Be₁₃. Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be₄AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be₄AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be₄AlMn phase.     

Investigation on the impact behavior of Al2O3-SiC-MgO nanoceramic/metal laminated composite

Lightweight laminated composites containing a ceramic front layer and a metallic backing layer were used in order to protect people, moving equipment, and mobile vehicles from high velocity impact and the increased mobility of mobile vehicles. In this study, by adding10 vol% SiC and 500 ppm MgO nanoscale particles on the microstructure of Al ₂ O ₃ matrix and applying optimum sintering conditions, ceramic performance against high-speed projectile impact was improved. To perform this investigation, a number of target samples with two different types of front layers (alumina and Al ₂ O ₃-SiC-MgO nanocomposite ceramic) were produced. Impact tests were conducted on these samples using 7.62 mm projectiles with a velocity of 820 ± 15 m/s. The amount of bulge and bending of the backing layer caused by impact tests was measured. The results of the impact tests on the samples made of Al ₂ O ₃-SiC-MgO nanocomposite ceramics and alumina were also compared and analyzed. The results indicate that the substitution of Al ₂ O ₃-SiC-MgO ceramic layer — which is proffered in this paper — instead of pure alumina ceramic layer, decreases the areal-density of the samples by at least 30% and improves mechanical properties by about a 60% increase in flexural strength and 100% growth of the energy distribution factor, which impressively increases impact energy absorption.     

Electron microscopy of crack/particle interactions in Al2O3/SiC nanocomposites

Crack/particle interactions in alumina/silicon carbide nanocomposites have been investigated by scanning electron microscopy and transmission electron microscopy, with cracks induced by Vickers microindentation. Intergranular cracks are frequently deflected into grains by SiC particles on grain boundaries inclined to the average direction of crack propagation. This mechanism is proposed to explain the change in the fracture mode from intergranular fracture for monolithic alumina to predominantly transgranular fracture for the nanocomposites. Neither stress-induced microcracking around SiC particles nor significant crack deflection by intragranular particles was found to occur in the nanocomposites. It is argued that an addition of nanoparticles may not be a promising approach for increasing the toughness of alumina.     

Near-field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1–xO3 thin films

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZr _x Ti_{1– x} O₃ thin films in the 0 <  x  < 0.4 range. Comparison of the near-field optical images and the results of atomic force microscopy and X-ray diffraction studies show that an optical resolution of the order of 100 nm is achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment is demonstrated.