地表积水对煤矿安全开采影响的数值模拟

为了探讨煤矿地表积水对煤炭地下开采的影响,采用数值模拟与理论计算相结合的研究方法,确定导水裂隙带高度.以地表积水渗流规律与之比对,判定该积水对煤矿开采的影响状况.该研究方法对煤矿水害防治具有积极的指导和借鉴作用.     

核电项目管理水平提升措施

文章围绕正确应用能级原则进行组织机构设置,做好有效制度的建立和管理,建立8项切实可行的管理制度,加大并做好人才的培养及管理工作,做好建设管理各个系统的经验反馈工作,积极开展施工技术及管理技术交流,全员参与安全管理,采用KPI体制对干系人进行考核的项目管理方法等方面,运用PDCA循环进行持续改进,为保证核电项目顺利进展提出了提升管理水平的措施,管理理论的提出与推广可为各核电项目的建设提供借鉴作用,促进工程建设的顺利进行。     

气相色谱串接质谱快速检测植物油中邻苯二甲酸酯

建立了气相色谱-串接质谱联用检测植物油中16种邻苯二甲酸酯类塑化剂的方法。采用乙腈直接萃取,固相萃取柱净化、洗脱,洗脱液经浓缩后,直接用气相色谱-串接质谱仪测定,内标法定量。结果显示,16种邻苯二甲酸酯类塑化剂的线性关系较好,方法检测限范围在0.004～0.01 mg/kg。在高、中、低3个水平下进行植物油加标实验,平均回收率为67.5%～117%,相对标准偏差小于15%(n=6)。方法简便快速,整个分析流程可在1 h之内完成,溶剂消耗量小,且应用串接质谱更好地消除了基质效应的干扰,灵敏度高,定性更为准确。     

秦山核电二期扩建工程不锈钢厚壁管的焊接施工技术

从焊前准备、产品焊接以及焊接过程中焊接应力、焊接变形的控制等方面,系统地介绍了秦山核电二期扩建工程不锈钢厚壁管的焊接技术。针对安装过程中出现的各类影响焊接质量的主要因素进行了系统的分析,提出解决焊接变形、错边变形、加工坡口不均匀等质量问题的办法,采用合理的焊接顺序、焊接见证件管理技术及模拟焊接技术和局部挖补促进应力分布,可有效保证焊接质量,从而更好地促进厚壁管焊接技术的发展。     

核电厂不锈钢覆面带垫板焊缝中焊接缺陷的RT定位检测技术

论述了核电厂不锈钢覆面衬里的带垫板焊缝中的焊接缺陷的RT定位检测方法,总结了其检测重点。采取二次联合曝光方法,并运用几何作图法进行缺陷的准确定位,以判断缺陷的埋藏深度,为建造阶段缩短判定周期,指导工程的正常进行提供依据。同时,对于焊件中的缺陷给出了一种立体拍片定位方法,可准确判定缺陷的位置。该技术的应用,可适用于各类钢结构中带垫板的焊接接头的缺陷定位,更利于压力容器、锅炉的封口焊缝的缺陷定位,减少不必要的返修,缩短生产周期。     

Preparation of SiC/SiC composites with high toughness by reaction of the SiCP+C double-cladding layer with liquid silicon

SiC/SiC composites prepared by liquid silicon infiltration (LSI) have the advantages of high densification, matrix cracking stress and ultimate tensile strength, but the toughness is usually insufficient. Relieving the residual microstress in fiber and interphase, dissipating crack propagation energy, and improving the crystallization degree of interphase can effectively increase the toughness of the composites. In this work, a special SiC particles and C (SiC_P +C) double-cladding layer is designed and prepared via the infiltration of SiC_P slurry and chemical vapor infiltration (CVI) of C in the porous SiC/SiC composites prepared by CVI. After LSI, the SiC generated by the reaction of C with molten Si combines with the SiC_P to form a layered structure matrix, which can effectually relieve residual microstress in fiber and interphase and dissipate crack propagation energy. The crystallization degree of BN interphase is increased under the effects of C-Si reaction exotherm. The as-received SiC/SiC composites possess a density of 2.64 g/cm³ and a porosity of 6.1%. The flexural strength of the SiC/SiC composites with layered structure matrix and highly crystalline BN interphase is 577 MPa, and the fracture toughness reaches up to 37 MPa·m^1/2. The microstructure and properties of four groups of SiC/SiC composites prepared by different processes are also investigated and compared to demonstrate the effectiveness of the SiC_P +C double-cladding layer design, which offers a strategy for developing the SiC/SiC composites with high performance.     

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.     

A progressive damage model for ceramic matrix mini-composites with thick interphases

Toughness enhancement in ceramic matrix composites (CMCs) with brittle matrix and fiber phases is often accomplished by introducing a weak finite-thickness interphase between the fiber and matrix. The current work presents a progressive damage model to predict the tensile response of single tow CMCs (mini-composite) representative of a unidirectional composite at the microscale. Implementation of a 3-phase shear-lag model for a geometrically accurate representation of the underlying microstructure in CMCs with finite thickness interphase has been highlighted. A probabilistic progressive modeling approach has been adopted, accounting for multiple matrix cracking, interfacial debonding, and fiber failure in 3-phase mini-composites. The predicted tensile response of CMCs from the progressive damage modeling approach agrees with experimental results obtained for C/BN/SiC mini-composites validating the approach.     

石家庄市地下管线数据动态更新

为确保城市地下管线信息系统数据的现势性、准确性,保证地下管线的安全运行,为市政规划建设管理及应急抢险提供数据支撑,管线数据动态更新势在必行.结合石家庄市地下管线动态更新维护工作,梳理管线定线、管线验槽、管线探测、数据入库等工作,总结经验教训,提出覆土前测绘、外业巡视、实时更新等有效措施,具有参考和推广价值.     

Rapid and low-cost carbon/carbon composites by using graphite slurry impregnated prepregs

A rapid and low-cost carbon/carbon (C/C) composites preparation method is proposed: graphite prepreg-coated carbon fiber fabric (CFF) is formed by hot pressing, followed by hot isostatic pressing and high temperature graphitization, to prepare C/C composite with low porosity and high crystallinity. In this method, the carbon fiber (CF) mass fraction can be precisely regulated in the range of 40–95% by the impregnation process conditions of CFF in graphite prepreg. The graphite particles in the preform were graphitized and bonded with CFF by high temperature graphitization. Finally, a ZrO₂ anti-ablative layer was applied using sol-gel method. The results show that when the CF mass fraction is 50%, the C/C composite with a crystallinity of 92.21 and a porosity of 3.47% can be obtained, with mass ablation rate of 0.23 mg/s and density of 1.62 g/m³. The method can prepare C/C composites with uniform density and high ablation resistance.