梯温法测定超薄玻璃液相线温度影响因素研究

液相线温度是玻璃制造工艺的重要参数,对评估玻璃配方的稳定性至关重要。基于梯温法探究保温时间、样品形态及观察位置等因素对测量超薄无碱玻璃液相线温度精确性的影响。结果显示,保温时间为24 h,采用棒状样品,从玻璃样品内部观测到的玻璃液相线温度较为准确。该研究为精准测量玻璃液相线温度提供参考,进而为设计玻璃配方与工业生产提供技术支撑。

定向晶化材料中的微观择优取向

文章概述了定向凝固和梯温升温以及恒温条件下的不同晶化取向现象。定向凝固条件下,晶体沿晶格常数最大的分向向低温方向生长,容易形成枝晶和片层状结构;梯温升温条件下,晶体沿晶格常数最小的方向生长,不容易形成枝晶;恒温条件下的择优取向则取决于晶核和晶体的晶格匹配。并应用超微颗粒物理得出了定向凝固和梯温升温条件下的两种相应的择优取向原理。

微晶玻璃的定向晶化

本文根据超微颗粒的晶化特征分析和阐明了梯温场中发生定向晶化的机制。指出了这种方法不仅与温度梯度有关而且与升温速度有关，并揭示了它在实际应用中的可能性。

Numerical investigation of temperature gradient-induced thermal stress for steel–concrete composite bridge deck in suspension bridges

A3D finite element model(FEM)with realistic field measurements of temperature distributions is proposed to investigate the thermal stress variation in the steel–concrete composite bridge deck system.First,a brief literaturereview indicates that traditional thermal stress calculation in suspension bridges is based on the2D plane structure with simplified temperature profiles on bridges.Thus,a3D FEM is proposed for accurate stress analysis.The focus is on the incorporation of full field arbitrary temperature profile for the stress analysis.Following this,the effect of realistic temperature distribution on the structure is investigated in detail and an example using field measurements of Aizhai Bridge is integrated with the proposed3D FEM model.Parametric studies are used to illustrate the effect of different parameters on the thermal stress distribution in the bridge structure.Next,the discussion and comparison of the proposed methodology and simplified calculation method in the standard is given.The calculation difference and their potential impact on the structure are shown in detail.Finally,some conclusions and recommendations for future bridge analysis and design are given based on the proposed study.

Microstructural evolution and mechanical properties of Ti-5Al-5Mo-5V-3Cr alloy by heat treatment with continuous temperature gradient

A new high throughput heat-treatment method with a continuous temperature gradient between 600 and 700 ？C was utilized on the Ti-5553 alloy（Ti-5 Al-5 Mo-5 V-3 Cr, mass fraction, %）. The temperature gradient was induced by the variation of the axial section of sample, which was heated by the direct current. The variation of continuous cooling rates on the treated sample was realized by using the end quenching method. The microstructural evolution and mechanical properties under different heat treatment conditions were evaluated. The results show that the pseudo-spinodal decomposition of the alloy occurs at（617±1） ？C, and the size of the precipitated α phase is around 300 nm. Moreover, the highest microhardness is obtained after the heat treatment at the pseudo-spinodal decomposition temperature for 4 h. These indicate that the high throughput method is efficient and fast to determine the phase transformation temperature and corresponding microstructural evolution of alloys.

Development of a Methodology for Determination and Analysis of Thermal Displacements of Machine Tools Using Finite Elements Method and Artificial Neural Network

In the processes of manufacturing, MT （machine tools） plays an important role in the manufacture of work pieces with complex and high dimensional and geometric accuracy. Much of the errors of a machine tool are those which are thermally induced which are from internal and external heat sources acting on the machine. In this paper, a methodology for determining and analyzing the thermal deformation of machine tools using FEM （finite element method） and ANN （artificial neural networks） is presented. After modeling the machine using FEM is defined the location of the heat sources, it is possible to obtain the temperature gradient and the corresponding thermal deformation at predetermined periods. Results obtained with simulations using the software NX.7.5 showed that this methodology is an effective tool in determining the thermal deformation of the machine, correlating the temperature reading at strategic points with volumetric deformation at the tool tip. Therefore, the thermal analysis of the errors in the pair tool part can be established. After training and validation process, the network will be able to make the prediction of thermal errors just stating the temperature values of specific points of each heat source, providing a way for compensation of thermally induced errors.

Effects of additive boron on HPHT diamond single crystals grown by TGM

In this work, under pressure 5.4 GPa and temperature 1250-1400°C, large gem-diamond single crystals with perfect shape and different content of additive boron were synthesized using temperature gradient method. High-purity boron powders were added as boron source into the graphite powder, and the effects of additive boron on crystal growth habit were investigated in detail. The relationship between the growth rate and the amount of additive boron was studied. The scanning electron microscopy was employed to study the morphology of boron-doped diamond crystals. Raman spectroscopy and Hall measurements were used to investigate the crystal structures and the carrier concentration, respectively. The results show that with the increase of the content of boron added into graphite powder, the crystal growth rate and the carrier concentration increase firstly, and decrease afterwards, and the zone-center phonon line at 1332 cm 1 has small shift to lower energy. The defects occur on the crystal surface when excessive boron is added in the synthesis system.