管道缺陷宽度对涡流检测信号影响的仿真研究

检测实践中金属构件缺陷成因各异,宽度相差较大,为了实现涡流检测的可靠性评价,建立了含矩形槽和梯形槽的管道二维轴对称有限元模型,计算了槽深和槽宽变化时信号相位和幅值结果.仿真结果表明:当矩形槽宽度一定时,信号相位与槽深规律性较强;而槽深固定,在槽宽较小时相位和幅值随槽宽有较大变化,槽宽较大时信号比较稳定;梯形槽的槽宽对信...     

Application of statistical methodology for the evaluation of mechanically activated phase transformation in nanocrystalline TiO2

Response surface methodology was employed to study the effect of three factors, namely as milling time, milling speed and ball to powder weight ratio, on the mechanical activation of polymorphic phase transformation in nanocrystalline TiO₂ powder and identify the probable interactions between these factors. The response was the rutile percentage after annealing the samples. Based on the statistical analysis, ball to powder weight ratio was found as the most effective factor and just one statistically significant interaction was found between milling speed and ball to powder ratio. It was also shown that increasing the milling time has no significant effect on the phase transformation since the required activation energy for the phase transformation is unattainable under these conditions. The rutile percentage was calculated from X-ray diffraction patterns of the samples via Rietveld refinement method. Raman spectroscopy was employed to verify the phase composition analysis based on X-ray diffraction results.     

核电站冷却剂主管道奥氏体-铁素体双相不锈钢铸件铁素体含量检测方法研究与实践

核电站冷却剂主管道奥氏体-铁素体双相不锈钢铸件中铁素体含量对主管道的使用性能具有重要影响,因此,铁素体含量的检测具有重要意义.本文以主管道90°弯管铸件为例,介绍了铁素体含量检测的各种试验方法,阐明了各种方法的检测原理、检测时机和具体步骤,简要分析了不同检测方法所检测结果的差异和原因,指出了各种方法的适用范围.     

低碳微合金钢的组织结构对强度的影响

利用扫描电镜、透射电镜及能量损失谱仪对不同强度的低碳微合金钢的组织结构进行了观察分析。结果表明:不同强度试验钢的析出相均以大量30～80nm的球形和矩形颗粒相为主,类型相同,尺寸相近,强化效果相当;试验钢组织均为贝氏体+M/A岛,但贝氏体类型和M/A岛尺寸差别明显;具有板条贝氏体及细小M/A岛的轧态组织强度高,冲击韧性好;粒状贝氏体及粗大M/A岛组织显著降低钢的屈服强度和抗张强度。     

Analytical determination of mesh phase relations in general compound planetary gears

This paper systematically studies the mesh phase relations of general compound planetary gears. The mesh phase relations are described by the relative phases between mesh tooth variation functions of all gear meshes. The analysis allows for compound planetary gears having multiple mesh periods. A numbering method is proposed for accurate definition of the relative phases in a general compound planetary gear. By introducing the concepts of system-level, stage-level, and train-level relative phases, the relative phases between any two gear meshes in a compound planetary gear are calculated systematically. Important relations among these relative phases are derived. The results from this study are necessary for analytical or computational multibody studies on the static or dynamic response of general compound planetary gears.     

From Allan Variance to Phase Noise: A New Conversion Approach

A new mathematical method is proposed to convert the oscillator instability parameters from Allan variance to Spectrum Density(SD)of random phase fluctuations,which is the inversion of the classic transformation formula from SD to Allan variance.Due to the fact that Allan variance does not always determine a unique SD function,power-law model of the SD of oscillator phase fluctuations is introduced to the translating algorithm and a constrained maximum likelihood solution is presented.Considering that the inversion is an ill-posed problem,a regularization method is brought forward in the process.Simulation results show that the converted SD of phase fluctuations from Allan variance parameters agrees well with the real SD function.Furthermore,the effects of the selected regularization factors and the input Allan variances are analyzed in detail.     

风电场无功补偿装置改造方案

对内蒙古太旗贡宝拉格风电场的无功功率特性进行了研究并取得如下成果:计算风电场无功损耗以及风电并网运行后的系统潮流,确定风电场由于损耗所需要安装的无功补偿容量;研究治理三相不平衡所需要的无功补偿容量和装置类型;根据实际情况确定风电场综合无功补偿配置,提出综合无功补偿的调节策略.实践表明,该方案有效地解决了风电场无功损耗和三相不平衡问题,具有较高的理论价值.     

电厂锅炉钢集箱分离器焊缝中黑色条纹分析

采用扫描电镜观察和能谱分析、显微组织检验、显微硬度和冲击韧性检验等方法对焊缝黑色条纹组织进行分析.结果表明:焊缝中看到的黑色条纹是密集颗粒状和条状碳化物偏析以及微裂纹所致.该组织的存在,对焊缝室温冲击韧性有一定的影响.     

生鲜牛乳中氯化物的测定

本试验采用间接沉淀滴定法测定生鲜牛乳中的氯化钠含量,试液经酸化后,加入过量的硝酸银溶液,以硫酸铁铵为指示剂,用硫氰酸钾标准溶液滴定过量的硝酸银,根据硫氰酸钾溶液的消耗量,计算生鲜牛乳中氯化钠的含量。     

移相器的原理及制作

移相器是用以调节交流电压相位的装置.着重论述了六边形移相器的原理、电路及制作.所设计制作的移相器能够在0°～360°.范围内达到任意角度的超前或滞后移相,并具有波形畸变系数小、无噪声、无振动、调节性能好等优点.实际应用证明了该设计制作的合理性和可行性.