基于路面使用性能评价的车辙指标研究

文章基于现有沥青路面使用性能评价规范和标准,运用简化的车辙积水模型,围绕高速公路沥青路面车辙深度主观评价标准,针对现有车辙评价模型的不足,通过采用Sigmoid函数,主要探索了车辙深度指数RDI评价模型。结果表明:结合求解的车辙内不致积水的临界车辙深度,将路面车辙深度等级划分为更精细的"轻、中、重"三个等级更加合理;优化的沥青路面车辙深度指数RDI评价模型弥补了现有车辙评价指标的不合理性;在保留现有车辙深度指数评价模型的同时,通过分析路面车辙槽的几何特征增加了车辙的其他指标,初步构建了车辙综合评价模型,对全面评价车辙的危害性及进行路面车辙的养护管理更具有实际意义。     

开采沉陷中采深偏移系数的性质分析

在处理倾斜煤层的开采沉陷数据时,往往采用平均采深代替走向主断面实际开采深度,此时存在着采深偏移系数的情况,不可避免地造成了开采沉陷预测的不准确性.为了提高开采沉陷预测精度,通过理论推导,给出了采深偏移系数计算公式,分析了上覆岩层岩性、煤层倾角、松散层厚度等地质采矿条件对采深偏移系数的影响.同时,结合11个矿区的开采工作面资料,求取了以平均采深代替走向主断面实际采深时各地表移动变形值的偏差.结果表明,采深偏移系数随着覆岩强度和煤层倾角的增加而增加,随基深比的减小而减小.当煤层倾角达到20°以上时,应该考虑采深偏移系数对各移动变形值造成的影响,为矿山开采沉陷准确预测提供参考.     

Investigation of Creep Feed Grinding Parameters and Heat treatment Effects on the Nickel-base Superalloys

The Nickel base Superalloys are the most famous complicated and useable of Superalloys to make hot zone components of the gas turbines. The complicated dimensional tolerances, specially at the root of the blade show importance of grinding processes at the production of blades root. The prediction of the effect of machining parameters on the soundness of component surface strengthening for reaching to a suitable surface finishing and avoiding from crack formation at the work part during machining operation often is not easy and feasible so needs to more industrial investigation.This research is about frame 5 blade designed by GE and made from Superalloy IN738LC has been investigated. The formation of a plastically deformed and heat affected zone during grinding of Superalloy IN738LC with a high depth of cut but slow work speed (creep feed grinding) was investigated. Parameters such as work speed, depth of cut and radial dressing speed have been considered as variables and their effects have been studied. During experimental performed, the voltage and current of motor measured and power and special energy calculated.Some samples heat-treated (of the 1176℃ for 1 hr under neutral argon gas and cooling rate of 15℃/min up to 537℃ and then air cooling) to study grains recrystallization. Other samples have been created from the roots of blades and then coated by Nickel to measure boundary layer micro-hardness. The results show that increasing work speed leads to increasing the use power. Increasing the depth of cut, by increasing material removal rate, and the radial dressing speed, by decreasing power, lead to decreasing special energy. The temperature created by grinding lead to decreasing plastic deformation and boundary layer formation. When the radial dressing speed changes from 1 to 0.6μm/rev and other parameters are kept unchanged the roughness of surface increases and the special energy decreases. Sufficient dressing is very essential in limiting the width of the molten zone to few micrometers. As a result, it was found that local melting at contact spots to be a rather common mechanism during grinding of superalloys, lead to so-called white layers which can easily be observed on metallographic cross sections.     

TIG焊和PAW焊中活性剂对焊缝熔深的影响

针对常规TIG焊生产效率低、熔深小等问题，研究了TIG焊和PAW焊中应用活性剂对焊缝熔深的影响。结果表明，应用活性剂后，在同样的参数下，同传统TIG相比，活性剂能够大幅度提高不锈钢、铝合金和钛合金的焊缝熔深。对于PAW焊，熔深也有增加，但是增加的幅度不如TIG效果明显，但对焊缝成形有很好的改善。同时，活性剂对铝合金焊接背面能够起到保护作用。对于钛合金，活性剂除了增加焊缝的熔深外，还能够大幅度地消减焊缝产生的气孔。     

Oxidation behavior of 2.25Cr-1Mo steel with prior tempering at different temperatures

The oxidation behavior of a normalized 2.25Cr-1Mo steel tempered previously for 10 hr at different temperatures between 873 and 1023 K has been studied up to a maximum duration of 1000 hr in air at 773–973 K. The oxidation resistance of the steel was found to decrease significantly with the temperature of tempering. Tempering of this steel is reported to cause microstructural changes involving precipitation of Cr as carbides and a decrease in the effective (free) Cr contents, that could influence the oxidation resistance of the Cr-containing alloys. Relative compositions across the thickness of the oxide scales, as analyzed by SEM/EDX and SIMS, suggest that a less Cr-rich (and less protective) and thicker scale on the steel formed because previous tempering caused extensive depletion of free Cr.     

Thin-skin analysis technique for interaction of arbitrary-shape inducer field with long cracks in ferromagnetic metals

In using the AC field measurement (ACFM) technique for non-destructive evaluation (NDE) of metals, a current-carrying wire structure is used to induce eddy current within a thin layer of the metal and a magnetic field sensor to measure the field perturbations in the vicinity of the metal. The sensitivity of ACFM crack detection and sizing relies on an appropriate design of the wire structure geometry together with a dully placement of the sensor. This paper presents an analytical modeling technique for evaluating the electromagnetic field interaction of an ACFM probe with a long uniform crack in a ferromagnetic metallic slab. The probe in the proposed model can have an arbitrary-shape wire inducer with no restrictions on its relative sensor position. The technique is accurate and very efficient computationally. It first uses the two-dimensional Fourier transform to obtain the field distribution at the metal surface. The Laplacian field distribution above the metal is then determined by satisfying the so-obtained boundary condition at air–metal interface. To demonstrate the accuracy of the model, we consider the special case of a rhombic wire inducer. The comparison of our results with those obtained using the conventional algorithm in the literature validates the accuracy of the model introduced in this paper. To show the generality of the model, we also present theoretical and experimental results associated with a solenoid inducer with a three-dimensional geometry for which no analytical solution is available in the literature. The theoretical prediction of crack signal supported by experimental results is used to develop a model-based method for inverting crack signal into crack depth.     

硬质合金磨削温度的实验研究

采用半人工和人工热电偶法，对硬质合金YG6和YT30平面磨削的磨削温度进行了实验研究。并对磨削参数与磨削温度的关系，进行了理论分析及实验验证。结果表明：磨削深度和工作台速度增加，磨削温度升高，但工作台速度的改变，对磨削温度的影响较小．     

影响冷硬铸铁轧辊白口层深度主要因素的回归分析

探讨了影响冷硬铸铁轧辊白口层深度的主要因素。运用数理统计回归分析方法对大量原始生产数据进行处理 ,求得生产条件下冷硬铸铁轧辊白口层深度与主要工艺参数之间的线性关系 ,并进行了理论分析     

缺陷深度脉冲热像检测新方法

介绍脉冲热像检测中由峰值时间求缺陷深度的方法，对热传导性能好的材料，从红外热像时间序列难以捕捉到峰值时间。为此提出了一个既能避开峰值时间又能被红外热像仪探测和记录的新参数，从而达到测量缺陷深度的目的。     

Effects of temperature and current density on the surface hardness and tribological properties of Ti-6Al-4V alloy by molten salt carburization

Surface hardening of Ti-6Al-4V alloy was achieved by carburization in a molten salt bath containing BaCO₃ as the carbon-yielding agent with electrolysis within the temperature range 790–930°C. The hardness of the total carburizing layer (TCD) is influenced by the bath temperature, the applied current density and the carburizing period. The major hardening effect is considered to be the formation of a solid solution of carbon in -Ti. The oxide film wrapping at the outermost surface of cathodically charged specimens, identified to be mainly BaTiO₃, was formed irrespective of the bath temperature during the quenching process and has no effect on the surface hardening. The optimal carburizing parameters obtained in this study for surface hardening are carburizing at 930±10°C (bath temperature) and 0.3 A/Cm² (applied current density) for 90 min (carburizing period), while those for tribological properties improvement are carburizing at 860±5°C and 0.3 A/Cm² for 90 min.