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1.
针对车身三维模型中焊枪头与焊点附近的钣金件之间空间间隙检查过程复杂、检查结果不准确等问题,提出了焊枪头与钣金件空间间隙的自动检查方法。在特征识别算法和包围盒技术的基础上获得焊点特征、钣金件特征和螺母特征等分析要素;基于三维模型的投影算法和距离测量算法计算钣金件的拓扑面与虚拟焊枪之间的距离,与安全阈值比较,筛选出与焊枪发生干涉的危险平面、孔和螺母;对焊接空间不足的焊点进行标注并截图。利用二次开发环境所提供的函数库编程实现了上述算法,通过运行实例以及企业的实际使用,验证了自动检查系统的可行性。  相似文献   
2.
通过按照相关标准设计并制作校准试块及认证试块,研发针对船体结构焊缝的检测工艺,实现对船体结构焊缝的检测。通过同RT对比结果表明,PAUT技术检测结果与传统RT检测结果相对应,无漏检情况发生,且检测精度较高。该成果可对今后船体结构焊缝的检测提供技术支持,降低辐射风险,提高作业效率。  相似文献   
3.
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5-benzimidazole)s are rigid-rod polymers to show ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole-co-amide)s are synthesized from two biobased monomers, 3,4-diaminobenzoic acid and a semirigid comonomer, 4-aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high-performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc.  相似文献   
4.
In the past decades, pyrochlores, such as Gd2Zr2O7, have demonstrated great potential to immobilize nuclear wastes such as Pu, which results in the production of Pu2Zr2O7. Due to the high radioactivity of Pu, it is difficult to investigate the radiation response behavior of Pu2Zr2O7 and its physical properties of the damaged state experimentally. Consequently, few related data have been reported in the literature thus far. In this study, first-principles calculations have been carried out to investigate the defect formation and its effect on the thermodynamic properties of Pu2Zr2O7. It reveals that PuZr antisite and O8a interstitial defects are very easy to form in Pu2Zr2O7. In particular, the O8a interstitial defect can be formed spontaneously, while it is mechanically unstable. When vacancy, interstitial or antisite defects are formed in Pu2Zr2O7, and the elastic moduli and Debye temperature are decreased. Besides, better ductility is resulted. As compared with other zirconate pyrochlores, such as Gd2Zr2O7, the Pu2Zr2O7 is suggested to be less resistant to radiation-induced amorphization. This study demonstrates that the created defects due to self-radiation from actinide decay have remarkable influences on the thermophysical properties of Pu2Zr2O7.  相似文献   
5.
C/SiC composites prepared by chemical vapor infiltration technique (CVI) have been regarded as thermal structural materials widely. However, these composites still suffer from poor functional properties like low thermal conductivity, especially in thickness direction of the composites, limiting their large-scale applications. Herein, mesophase pitch based carbon fiber (MPCF) and continuous wave laser machining were utilized to construct highly effective heat conductive micro-pipelines within CVI C/SiC composite. The effect of initial density on the final density and thermal conductivity of the as-obtained MPCF-C/SiC composites were investigated. The results revealed that higher initial density would directly enhance the thermal conductivity and reduce the negative impact of the bottle-neck effect. At temperatures between 100°C and 500°C, MPCF-C/SiC composites preserved more than threefold of the thermal conductivity (340%) when compared to reference C/SiC composites. This work provides a highly effective route for enhancing the thermal conductivity of C/SiC, which would broaden their future applications.  相似文献   
6.
Due to the growing energy requirements, the proportion of external thermal insulation composite systems (ETICS) installed has increased significantly during the past 50 years. Due to the longevity of these systems, ETICS waste is currently accumulating. Owing to the complex construction as well as a multitude of differently installed materials and substances of the past generations, there are many uncertainties and problems with the clean and low-pollutant processing of such systems. In the frame of this work, the ETICS were processed and sorted before being screened for ingredients or pollutants as well as for the purity of the recovered material fractions.  相似文献   
7.
介绍了高分子材料导热性能影响因素研究进展,重点阐释了聚合物基体的结构特性(链结构、分子间相互作用、取向、结晶度等)、导热填料(种类、含量、形态、尺寸等)以及制备方法等对高分子材料导热性能的影响。  相似文献   
8.
以热膨胀仪判定建窑黑瓷烧成温度的研究为例,综合运用多种测试方法对建窑黑瓷标本进行了系统研究,探讨如何从建窑黑瓷胎体重烧热膨胀曲线中筛选有效转折点的问题及其转折点的形成原因。研究表明:(1)建窑黑瓷胎体重烧热膨胀曲线上有三个转折点,分别为收缩转折点、膨胀转折点和急剧收缩点。其中第一个收缩转折点是判定其古代烧成温度的关键点。(2)建窑黑瓷胎体重烧热膨胀曲线上膨胀转折点和急剧收缩点的形成皆与其胎体中大量Fe_2O_3在高温下发生分解反应有关。该研究不仅为热膨胀仪测定建窑黑瓷烧成温度的应用研究提供判定依据,也将为科学认识古陶瓷胎体重烧热膨胀曲线上多个转折点的形成机理提供数据支持。  相似文献   
9.
Barium strontium alumino silicate (BSAS); (Ba0.6Sr0.4Al2Si2O8) was synthesized through solid state reaction between BaCO3, SrCO3, Al2O3 and SiO2 subjected to wet milling in isopropanol for about 24 h. The sequence of the solid state reaction was studied by subjecting to DG/DTG from room temperature to 1550 °C. The crystallographic phase evolution was confirmed by X-ray diffraction of the powders calcined in the range 1000 to 1300 °C for 2 h. The monoclinic celsian phase obtained at 1300 °C, pelletized through uniaxial pressing was sinterable to 67 to 78% density in the temperature range of 1300 to 1500 °C. The density improved to 75 to 94% after ball milling for 76 h, while ZrO2 addition further improved the density by 2%. The celcian phase of BSAS was dispersed in isopropyl alcohol, milled for about 24 h and spray coated on to plain SiC and mullite precoated SiC substrates. Sintering of coated samples and characterization for weight gain/loss, microstructure, scratch test prove that mullite + BSAS coating is more effective than single layer coating of BSAS on SiC substrates.  相似文献   
10.
LiNbO3 crystals activated by Sm3+ and co-doped with Zr4+ (Sm:Zr:LN) or Hf4+ (Sm:Hf:LN) were prepared by the Czochralski method. Detailed investigation on spectroscopic properties was conducted on the frame of Judd-Ofelt (J-O) theory. The J-O intensity parameters Ωi (i = 2, 4, 6), fluorescence branching ratios and radiative lifetime of excited level 4G5/2 were determined. Furthermore, the thermal stability of the strong orange-red emissions obtained under near-UV excitation in both crystals was evaluated. As high as 100% and 97% of integrated intensities at room temperature in Sm:Zr:LN and Sm:Hf:LN respectively were retained at 423 K, demonstrating the suppressed thermal attenuation. The temperature sensing performance based on fluorescence intensity ratio strategy was degraded at higher temperatures with relatively low sensitivities, while the shift of CIE chromaticity coordinates of Sm:Zr:LN and Sm:Hf:LN in the orange-red region was insignificant, demonstrating the color constancy with increasing temperature. With the efficient and thermally stable orange-red luminescence, Sm:Zr:LN and Sm:Hf:LN could serve as promising candidate materials for near-UV excited white light-emitting diodes.  相似文献   
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