壁板结构热屈曲后模态特性试验

高速飞行器在服役期间面临着严酷的气动加热效应,热载荷会引起材料性能变化,会在结构内部产生热应力、热变形及热屈曲,从而改变结构的有效刚度,影响其动力学特性。针对铝合金壁板结构开展热屈曲后模态特性的试验,采用石英灯辐射加热方法模拟气动加热,利用热应变与温度的关系,获得了壁板结构热屈曲临近温度,进而选取屈曲前、屈曲后一系列温度状态开展热模态试验。试验结果表明,模态频率随加热温度的增加先降低,在临近屈曲温度附近达到最低值,热屈曲后随着温度增加又逐渐增加。由于不同阶模态对热载荷的敏感程度不一样,第3阶和第4阶模态在加热过程中发生交换,而模态阻尼随着加热温度的增加呈现增加的趋势。     

Analysis of tool temperature fluctuation in interrupted cutting

A unidimensional model for temperature distribution in the tool during intermittent cutting is presented. The tool-chip interface heating is approximated by a periodic rectangular heat flux. The effects of cutting time ratio, frequency of temperature fluctuation and thermal diffusivity of the tool material on internal temperature distribution and on thermal stresses developed in the tool have been discussed. With increasing cutting frequency, the temperature gradient in the cutting zone increases, but with higher thermal diffusivity of the tool material, it diminishes. The magnitude of thermal stresses increases with increase in amplitude of temperature fluctuation     

干式地板辐射供暖系统特性的试验研究

对干式地板辐射供暖系统进行了连续供暖和变供水工况测试,分析和评价了干式系统的供暖性能和热舒适性,并与湿式系统进行了比较。试验结果表明:干式系统稳定运行时,室内空气温度在水平和竖直方向分布均匀,热稳定性和热舒适性好。辐射换热量约占总换热量的65.6%,总换热量能够满足大部分建筑冬季供暖需求。干式系统在35~40℃区间内调节供水温度,可明显改变室内温度,而调节供水流量对室内温度影响不大。与湿式系统相比,干式系统预热时间短,对供水温度要求低,供暖能力强,更适用于需要间歇供暖的场所,但其蓄热能力差。结果将为干式系统的设计及其应用提供试验数据支撑。     

热辐射处理制备VC涂层的温度-应力场有限元分析

利用ANSYS有限元软件对热辐射处理制备VC(碳化钒)涂层进行建模,分析了涂层厚度、加热温度及加热时间对VC涂层温度场-应力场的影响规律。结果表明,不同温度下涂层沿x轴方向温度变化的趋势均呈上升趋势;涂层最高温度(837℃)与加热温度(850℃)相差15℃左右,温度差值约1.52%;不同厚度下温度的变化趋势均为递减,当厚度为6μm时,温度递减的趋势较平稳,未出现峰值,当涂层厚度增加时,应力值先增加然后减小,在厚度为6.3μm时发生突变,而后呈递增趋势;考虑应力、厚度因素对涂层性能的影响,涂层最佳厚度应为5～6μm。     

车灯起雾原因及解决方案探讨

水蒸气遇冷在灯罩内表面凝结形成雾气,不仅严重影响车灯的外观,而且给汽车行驶带来安全隐患。对车灯起雾的原因进行分析,指出车灯起雾与灯内湿度、温度场分布及凝结核密切相关,并由此提出应对措施,为解决车灯起雾问题提供参考。     

金属辐射板与双冷源新风机组联合运行供暖特性试验研究

针对目前对双冷源新风机组与辐射板联合运行供暖系统应用于办公室的运行特性的研究很少的现状,搭建了金属辐射板与双冷源新风机组系统测试平台,测试了金属辐射板与双冷源新风机组空调系统供暖运行状态,以及双冷源新风机组供热性能、空气源热泵制热性能以及室内温度分布特性和室内空气品质.结果表明,金属辐射板与双冷源新风机组空调系统冬季供...     

焊后热处理对ASTM4130钢焊接粗晶区韧性的影响

采用焊接热模拟试验研究了焊后热处理不同保温时间对ASTM4130钢焊接粗晶区组织和韧性的影响,同时分析了预热温度对粗晶区焊后热处理效果的影响。试验结果表明,经640℃不同保温时间的焊后热处理,ASTM4130钢粗晶区未发现再热脆化现象;随着保温时间的延长,冲击功先升高后降低,在保温时间为2．0h时达到峰值;在焊后热处理工艺相同的情况下,提高预热温度冲击功却稍有降低。试验证明：预热温度200℃,焊后热处理工艺为640℃×1．5h,粗晶区可获得良好的强韧性匹配。     

薄膜厚度对直流脉冲磁控溅射Mo薄膜光电性能的影响

采用直流脉冲磁控溅射方法在SLG衬底上沉积CIGS太阳电池背接触Mo薄膜,研究了薄膜的光学和电学性能随厚度的变化关系。结果表明,随着薄膜厚度的增加,薄膜的电阻率先降低后增加,在厚度284.3nm处电阻率最低,为7.3×10-4Ω.cm。不同厚度的Mo薄膜在各个波长处(200~840nm)反射率都随波长的增加而增大。随着薄膜厚度的增加,平均反射率总的呈下降趋势,在薄膜厚度284.3nm时出现一反射率高峰,其在200~840nm波长范围内的平均反射率达43.33%。     

Performance evaluation of a water-to-water heat pump with a floor panel heating system

The performance of heat pump is severely degraded as the temperature of the heat source is decreased. For air source heat pumps, this results in a serious mismatch of heat pump output and space heating demand. Although the outdoor temperature is below 0°C, the use of a water-to-water heat pump with a floor panel heating system can operate for extended periods of time without frost-defrost cycling and therefore at a high seasonal efficiency. This paper focuses on the performance of a water-to-water heat pump that uses well water as a heat source and a floor panel heating system as a sink.     

Temperature analysis for the point-cell source in the vapor deposition process

The information indicating device plays an important part in the information times. Recently, the classical CRT (Cathod Ray Tube) display is getting transferred to the LCD (Liquid Crystal Display) one which is a kind of the FPDs (Flat Panel Displays). The OLED (Organic Light Emitting Diodes) display of the FPDs has many advantages for the low power consumption, the luminescence in itself, the light weight, the thin thickness, the wide view angle, the fast response and so on as compared with the LCD one. The OLED has lately attracted considerable attention as the next generation device for the information indicators. And also it has already been applied for the outside panel of a mobile phone, and its demand will be gradually increased in the various fields. It is manufactured by the vapor deposition method in the vacuum state, and the uniformity of thin film on the substrate depends on the temperature distribution in the point-cell source. This paper describes the basic concepts that are obtained to design the point-cell source using the computational temperature analysis. The grids are generated using the module of AUTOHEXA in the ICEM CFD program and the temperature distributions are numerically obtained using the STAR-CD program. The temperature profiles are calculated for four cases, i.e., the charge rate for the source in the crucible, the ratio of diameter to height of the crucible, the ratio of interval to height of the heating bands, and the geometry modification for the basic crucible. As a result, the blowout phenomenon can be shown when the charge rate for the source increases. The temperature variation in the radial direction is decreased as the ratio of diameter to height is decreased and it is suggested that the thin film thickness can be uniformed. In case of using one heating band, the blowout can be shown as the higher temperature distribution in the center part of the source, and the clogging can appear in the top end of the crucible in the lower temperature. The phenomena of both the blowout and the clogging in the modified crucible with the nozzle-diffuser can be prevented because the temperature in the upper part of the crucible is higher than that of other parts and the temperature variation in the radial direction becomes small.     

沉船重油电磁感应加热仿真与实验研究

针对沉船水下抽油过程中重油加热的需求,提出一种基于电磁感应原理利用油舱外板加热重油的方法,根据电磁理论及热传导理论建立了加热过程的数学模型,使用有限元软件进行数值模拟,得出重油加热过程温度衰减规律,利用油舱模型进行重油加热模拟实验,测量油舱加热过程重油温度变化及衰减规律。通过模型进行重油水下电磁加热的验证可知,实验结果与数值仿真重油加热温度变化规律有良好的匹配性。该电磁加热重油技术设备简单、加热效率较高,在防止沉船燃油泄漏领域具有较好的应用前景。     

球化孕育处理工艺对下贝氏体铸铁组织特性及力学性能的影响

采用真空中频感应炉,通过改变球化孕育处理工艺获得具有不同形态石墨的铸造试样,将铸件加热到860 ℃保温2 h,使用20 ℃的硝酸钠、亚硝酸钠饱和溶液将其连续冷却至室温,并在250 ℃低温回火2 h后空冷,获得具有不同形态石墨的下贝氏体基体组织。研究了球化孕育处理工艺对石墨球化效果的影响,以及石墨形态对热处理显微组织和力学性能的影响。结果表明：球化处理温度及时间对铸铁中的镁吸收率有显著影响,超过1 500 ℃时,镁烧损加剧,当球化处理温度为1 450 ℃,镁吸收率达到64.2%;孕育剂添加工艺也是影响铸铁中石墨的形态和分布的重要因素,当一次孕育和二次孕育添加量分别为0.8%和1.2%时,石墨的形态以球状为主,尺寸细小且分布均匀,石墨的球化率为93%,球化级别达到2级,尺寸级别为9级;另外,均匀分布的球状石墨有利于提高热处理后下贝氏体铸铁的综合力学性能。     

粗糙液膜机械密封液汽相变研究

以逆向重构的确定性粗糙表面机械密封模型为依据，建立机械密封微间隙三维粗糙液膜流动计算模型；联立黏温效应与流体物性参数，对比光滑模型和粗糙模型的流速、端面压力、温度和相态规律；研究粗糙模型在不同载荷和转速下对液膜密封汽化相变特性以及密封性能关键参数的影响。研究结果表明：粗糙模型受温度变化程度更大，从478 K增加到了493 K;相态分布均随温度的升高而增大，其中同一温度下，粗糙模型的汽相分布更多，且在493 K之后出口相变程度就达到了100%,最大相体积分数增加11.73%。从而推断出：随着压力升高，端面汽相占比逐渐降低，而转速增加促进了汽化的发生。     

感应加热对激光增材修复高温合金DZ125L组织和力学性能的影响

通过研究感应加热条件下激光增材修复高温合金DZ125L的组织和显微硬度分布规律,揭示了感应加热对高温合金修复层附近组织与性能的调控机制。结果表明,与无感应加热样品相比,1 000℃感应加热可以有效降低温度梯度,进而导致修复层枝晶间距由3.8 μm增加到7.2 μm,γ'强化相尺寸从19.8 nm增加到74.0 nm,热影响区范围由200 μm增加至500 μm。在热影响区中,显微硬度持续增加,并在修复层维持恒定。热影响区硬度值的连续增加主要与一次γ'和二次γ'的体积分数变化有关,而修复层硬化机制主要与不同尺寸γ'的强化效果有关。     

氧化条件及合金成分对铜锌合金颜色的影响

用分光光度计测定铜锌合金表面对不同波长光波的反射率，根据光谱波长及范围与颜色的关系给出了不同反射区域所对应的铜锌合金表面颜色，结合能带理论分析了加热时间、加热温度及合金成分对合金颜色的影响。结果表明：升高加热温度或延长加热时间，合金表面色相中的黄色和红色部分会增多，并且锌的加入可明显提高紫铜的黄度。     

T92/12Cr1MoV异种钢焊接温度场的数值模拟

重点介绍T92/12Cr1MoV焊接过程的三维有限元分析模型,得到了多层焊温度场的分布规律,同时通过有限元分析中的关键问题判断和检测,得出如下实验结果：距离焊缝越近的点,加热及冷却速度越快;预热温度提高,加热速度及高温停留时间变化不大,但峰值温度升高,且相变温度以上停留时间变长;焊接线能量增加,t8/5延长,而t8/5过长,促进晶粒长大,使韧性降低,t8/5过短,易生成淬硬组织,因此应严格控制焊接线能量。     

小尺度蒸发器的数值模拟及优化研究

为了使差示扫描量热仪中加热炉快速的从400℃以上的高温冷却到室温,设计了一套采用小尺度蒸发器的单级制冷系统。为保证冷却过程中蒸发器内部温度场的均匀性及冷却效果,利用CFD商业软件,对该蒸发器内部流体的温度场进行数值模拟,并对蒸发器表面温度进行了试验测量。试验结果表明,蒸发器内壁面温度达到设计要求(-35℃);蒸发器整体温度分布均匀,轴向温差小于1℃;模拟结果与试验测量结果基本吻合。在此基础上进一步对该蒸发器进行了优化设计,将其内壁面改为波纹面,采用波纹面的蒸发器与加热炉的换热空间内,被冷却空气的比例增大,空气出口温度明显降低,冷却效果增强。     

Experimental Study of Lubricant Depletion in Heat-Assisted Magnetic Recording: Effect of the Duration of One Laser Heating

Heat-assisted magnetic recording (HAMR) is a technique to overcome the superparamagnetic limit and enabling large increases in the storage density of hard disk drives. The performance of lubricant on disk surface under the high temperature in the heating assisted writing process is a big concern. Laser heating in HAMR is quite different from conventional slow heating. Laser heating duration in one heating and cooling process in HAMR is as short as 1?ns. It is believed that lubricant depletion caused by the nano-second pulse laser heating in HAMR is much less severe than that caused by long time continuous laser heating. In this study, a method to compare the laser heating temperature at different laser heating conditions is developed. Lubricant depletion caused by nano-second and continuous laser heating in one heating and cooling cycle in HAMR is determined quantitatively based on test results. It is found that laser heating duration in one heating and cooling cycle in HAMR is not important to lubricant depletion. No matter laser heating is in nano-second or continuous in one heating and cooling cycle, lubricant depletion caused by the laser heating is comparable provided that the laser heating temperature is comparable.     

可降解秸秆花盆压制模具瞬态热分析

针对某型号花盆实验压制模具加热需要较长时间,模芯周围温度分布不均匀等问题,本文运用三维建模软件UG对模具进行实体建模,并运用ANSYS对花盆模具加热过程进行瞬态热分析,得出模具加热到正常工作温度所需时间和正常工作时花盆模具的温度分布云图,为缩短花盆模具的加热时间及模具电热管分布等问题提供了参考依据。     

Optimal design of medium channels for water-assisted rapid thermal cycle mold using multi-objective evolutionary algorithm and multi-attribute decision-making method

Rapid heat cycle molding technology developed recently is a novel polymer injection molding process. In this study, a new water-assisted rapid heat cycle molding (WRHCM) mold used for producing a large-size air-conditioning plastic panel was investigated. Aiming at improving heating efficiency and temperature distribution uniformity of the mold cavity surface, a two-stage optimization approach was proposed to determine the optimal design parameters of medium channels for the WRHCM mold. First of all, the non-dominated sorting genetic algorithm-II (NSGA-II) combined with surrogate models was employed to search the Pareto-optimal solutions. Subsequently, the Technique for Order Preference by Similarity to Ideal Solution was adopted as a multi-attribute decision-making method to determine the best compromise solution from the Pareto set. Then, the layout of the medium channels for this air-conditioning panel WRHCM mold was optimized based on the developed optimization method. It was indicated that the heating efficiency and temperature distribution uniformity on the mold cavity surface were greatly improved by using the optimal design results. Furthermore, the effectiveness of the optimization method proposed in this study was validated by an industrial application.