热双金属片挠度值测量精度分析

热双金属片挠度值测量是检测其热弯曲一致性及稳定性的重要指标。介绍了热双金属片工作原理,分析悬臂梁法热双金属片热弯曲变形过程中产生的水平位移对各点挠度值测量精度的影响。利用CCD激光位移传感器非接触测量热双金属片被测面各点挠度值,通过补偿水平位移误差提高热双金属片各点挠度值测量精度,并实验验证各点挠度测量值的准确性。     

双金属片无废料冲模

热继电器双金属片是用媒、铬金属制成。冬宾'为了节约我国稀缺余叹挨、井誉j一制造成功一付双金属无废料冲模,本模用于热继电器双金属片户;无废漓冲裁角:过去对丫_;是单。!1模一次一片,而且有废料现用模后,一次冲10片无废料,_、提高工效6倍。节约双金属片20撼以_卜。     

直片式双金属片在断路器中的设计

微型断路器是具有过载保护、短路保护等功能的一种终端保护电器,针对微型断路器热过载保护元件双金属片的设计进行分析,从双金属片的材料选用、工作计算和设计校验等几个部分探讨了双金属片的整个设计过程。     

局部受损预载结构屈曲强度和后屈曲承载能力评估和预报

项目负责人:沈惠申所在单位:上海交通大学项目批准号:59975058项目简介本课题主要涉及结构非线性稳定理论及其应用。以研究复合材料层合剪切板壳结构在复杂环境和复杂荷载作用下的屈曲强度和后屈曲承载能力为主要目标。复合材料层合板壳结构通常承受机械荷载和热荷载的共同作用,而预加热荷载或机械荷载往往会降低板壳结构的屈曲荷载（或临界温度）和后屈曲/热后屈曲承载能力。复合材料的力学性能对于外部环境有着很大的依赖性。外部环境的两种效应可以造成很大的内应变,从而影响屈曲荷载。这两种效应是吸湿效应和热效应。水     

ATZ—8型双面度盘秤示值误差在—20～40℃范围内的补偿

ＡＴＺ－８型双面度盘秤在－２０￣４０℃温区内的示值误差采用热双金属片进行补偿，使之达到国家标准所规定的允差限内。本文提出先测秤用弹簧的温度系数，再计算改变杠杆比所需双金属的变形量，最后由变形量计算出热双金属片的热物性参数，由此确定热双金属的牌号。本文的理论计算与实验结果是吻合的。     

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。     

一种新型片状式蒸汽疏水阀结构设计分析

针对浮球式蒸汽疏水阀蒸汽泄露严重、浮球损坏严重问题,根据杠杆原理、双金属片热变形原理,提出一种新型片状式蒸汽疏水阀设计方案,通过对双金属片在不同温度下的热变形分析,达到了疏水阀的设计使用需求,实现了疏水过程中水、汽的分离排放,与常用的浮球式蒸汽疏水阀相比,不仅可以简化结构,还可以延长其使用寿命.     

高温管道的热后屈曲分析

基于弹性杆件轴向可伸长假设,应用势能最低原理,分析两端铰支约束管道在直埋和架空条件下的热后屈曲特性,获得管端约束力、管道规格、最大变形和管内流体最高温度之间的关系方程。求解方程解析解发现,直埋管道的屈曲特性与失稳模态、材料特性、几何尺寸和温度等多种因素有关,架空管道的屈曲特性仅取决于管径、长度、壁厚和温度,与模态无关。通过分析数据,证明管道热屈曲的非突发性,并探讨Euler解的意义。采用热后屈曲理论,对比适当许可变形条件下,管道规格与管内流体温度之间关系解析解与欧拉解的差异。     

变厚度多孔梯度材料圆板的热后屈曲分析

为分析多孔梯度材料圆板在非均匀温度场中的热后屈曲响应,基于经典板理论和物理中面概念建立了梯度多孔材料圆板在热载荷作用下的控制微分方程,其中假设厚度变化沿半径为二次抛物线型且板在其厚度上具有对称和非对称的非均匀孔隙率分布。采用打靶法数值求解了问题的屈曲和后屈曲响应,给出了均匀升温和热传导下的梯度多孔非线性变厚度圆板后屈曲平衡路径。结果显示：变厚度系数、孔隙率系数、孔隙分布方式以及温度场对板的临界载荷和后屈曲平衡路径均有影响;在不同温度场中孔隙率系数越大,屈曲时的临界载荷越小;孔隙率对称分布下的临界载荷大于非对称情况下的。     

高速飞行器网格翼型结构热屈曲及热模态分析

翼片结构在高速飞行过程中会承受比较大的气动力和气动热形成的复合载荷。为研究网格翼结构的工作热屈曲和热模态特性,进行了理论分析和有限元计算;得到了结构的热屈曲临界温度、均匀及非均匀温度载荷下的热模态参数;发现网格翼结构的热屈曲临界温度要高于相同外形和材料的实体平板翼结构,且高温下结构材料热物理参数对热模态的影响要大于材料弹性参数,非均匀温度载荷下的网格翼结构热模态固有频率数值与均匀温度载荷下有一定区别。     

Structural behaviour of endodontically treated teeth under thermomechanical loading

Choosing the optimal combination of post construction and restorative materials to minimize thermomechanical stresses in endodontically post-restored teeth is a very challenging task. In fact, while thermal properties of metallic alloys used for endodontic posts are rather similar to those of natural dental tissues, composite restorative materials used for constructing post and postcore usually possess better mechanical properties than metallic alloys. This may make it very difficult to evaluate directly thermomechanical stresses in the restored tooth. Therefore, this paper presents a detailed analysis of the structural behaviour of several post-endodontic restorations submitted to different combinations of thermomechanical load. The aim of the study is to compare the relative merits of different restoration concepts. Three-dimensional finite element method (FE) analysis is carried out for an upper incisor restored with composite as well as metallic post systems. Furthermore, customized and standard post constructions are compared. Two loading cases are considered: (a) exposure to cold irritants in absence of mastication; (b) mastication of cold or hot foods. Effects of thermal field inhomogeneity and occlusal force magnitude are also included in the analysis. Because of the transient nature of thermal loads, relative performance of different restorations is investigated as the thermal perturbation spreads through the restored tooth. Results indicate that composite post systems are globally more efficient than restorations including a metallic alloy post when thermal cycles and mastication act together. However, relative performance of different restoration concepts in the absence of mastication may depend strongly on the time of exposure to thermal irritants.     

Determining the effects of thermal conductivity on epoxy molds using profiled cooling channels with metal inserts

Polymer injection molds are generally manufactured with metallic materials, such as tool steel, which provide reliable working of molds and extended service life. The manufacture of injection molds with steel is a prolonged process because of the strength of steel. For a short prototype production run, one of the suitable choices could be the use of aluminum-filled epoxy material, which can produce a functional mold in a short time as compared with a conventionally machined tool. Aluminum-filled epoxy tooling is a good choice for short production runs for engineering applications, yet works best for relatively simple shapes. The advantages in relation to the fabrication of injection molds with epoxy-based materials include time saving in producing the mold, epoxy curing at ambient temperature, and ease of machining and post processing. Nevertheless, one major drawback of epoxy material is its poor thermal conductivity, which results in a relatively longer cooling time for epoxy injection molds. This study investigates some of the innovative ideas for enhancing the thermal conductivity for epoxy molds. The basic concept behind these ideas was to embed a highly thermally conductive metal insert within the mold between cavities with an innovative design of cooling channels called profiled cooling channels. This technique will increase the effective thermal conductivity of the epoxy mold, leading to the reduction in cooling time for the injection molded polymer part. Experimental analysis conducted in the current study also verified that the mold with profiled cooling channels and embedded metal insert has significantly reduced the cooling time.     

芯片用金刚石增强金属基复合材料研究进展

随着电子设备集成化程度越来越高,对高导热封装材料的需求也越来越大,金刚石增强金属基复合材料凭借其高导热性能成为研究焦点。然而,由于金刚石颗粒与金属基体之间的不润湿特性,具有高导热性的金刚石增强金属基复合材料难以制备。文中综述了金刚石增强金属基复合材料的研究进展,包括界面改性、工艺参数优化和复合材料制备方法,并指出了金刚石增强金属基复合材料目前存在的问题和今后的研究方向。     

上切牙金属桩冠根折原因分析

目的分析上切牙金属桩冠修复患者根折的原因。方法对2008~2011年上切牙桩冠因根折而拔除金属桩冠及牙根的368例病例进行回顾性分析,按照根桩与牙根长度关系和冠修复方式进行分析。结果金属桩在骨内的长度小于牙根在牙槽骨总长度的1/2牙折病例数多于金属桩在骨内的长度大于牙根在牙槽骨总长度的1/2牙折病例数,单个桩冠根折病例数多于联冠桩冠根折病例数。结论金属桩核冠修复中除要保证桩的长度不短于临床冠的高度外,桩在骨内的长度是否达到牙根在牙槽骨总长度的1/2,单冠相对于联冠修复均可能是根折发生的相关因素。     

温度对机械密封金属波纹管力学性能的影响

为了研究温度对机械密封金属波纹管力学性能的影响,建立高温泵用机械密封焊接金属波纹管计算模型,利用ANSYS软件计算波片的温度场,并通过间接耦合法计算不同介质温度下的热应力与热应变场,得到温度对波纹管力学性能的影响规律.计算结果表明:在高温工况下波纹管波片内产生了较大的热应力和热应变,增大了波纹管断裂、失弹等形式的失效的危险,在设计和使用过程中必须对此引起足够重视;在高温工况下波纹管波片等效热应力、热应变的最大值均出现在波片波谷处.     

火电厂锅炉结焦的成因及防治

主要通过对锅炉结焦的原因、危害、对策等问题详细探讨，得出解决火电厂锅炉结焦问题的有效措施，经火电厂综合防治后燃烧效率得到提升，为锅炉功能改造提出切实可行的指导意见。     

SIMULTANEOUS MEASUREMENT OF THE THERMAL AND TRIBOLOGICAL EFFECTS OF CUTTING FLUID

The use of cutting fluids in industrial machining is widespread, while scientific research of the performance of cutting fluids lags behind. While much has been documented about the beneficial mechanisms of tool-chip lubricity and heat transfer from varying fluid types and applications, an accurate, flexible, and expedient method for investigating cutting fluid performance lies beyond the scope of modern experimental methods. This paper proposes an experimental system and methodology that aims to simultaneously quantify the effectiveness of cutting fluid in thermal (cooling characteristics) and mechanical (frictional effects) terms. The system acquires cutting force measurements with a piezoelectric tool post dynamometer to gauge the mechanical effectiveness of the cutting fluid through the variation in friction coefficient. Thermal effectiveness is examined by comparison of thermal images of the tool flank face obtained through the use of full-field infrared imaging and a point temperature obtained from a single type-K microthermocouple embedded below the insert rake face. The system's uniqueness lies both in its ability to obtain simultaneous and real-time mechanical and thermal data, and in its application of infrared imaging technology to metal cutting in the presence of cutting fluid. Proof of concept testing was done by examining orthogonal end-turning of Al 6061-T6 with both high speed steel and carbide inserts with and without overhead application of a hybrid cutting fluid over a range of cutting conditions.     

Mullitef／M124F复合材料的热膨胀细观模型

文中结合细观力学的方法,在纤维和基体结合良好的基础上,根据理想化的假设提出了计算金属基复合材料的一种热膨胀表达式,用Mullitef／M124F金属基复合材料的热膨胀系数的实验结果进行了初步的验证。     

加氢反应器堆焊层裂纹的成因与对使用的影响

分析了加氢反应器堆焊层裂纹的成因与对使用的影响。由于加氢反应器焊后热处理时不锈钢σ相脆化与使用时的氢脆可使堆焊层金属的塑性降到很低值,使得堆焊层的高应力部位萌生开裂。由于壳体基材有高的断裂韧性,堆焊层裂纹不会扩展到壳体基材,堆焊层裂纹不影响加氢反应器的使用性。     

A method for determining the thermal EMF and thermal conductivity

A method for measuring the thermal emf and thermal conductivity of conducting samples is described. After the temperature and potential differences are measured between the sample’s ends, on which metal contacts are deposited, at a specified direct current, the current is turned off, and instantaneous values of the integral thermal emf are measured directly at the metal contacts. Using the results from measuring the temperature and potential differences during passage of the direct current, the electrical and thermal conductivities of the sample are calculated. A specific feature of this technique is the use of additional thick metal layers being in contact with the surfaces of the metal contacts at the sample’s ends, which are aimed at stabilizing the temperature gradient along the sample when the current source is switched off.