补偿导线的测量误差

目前，热电偶还是工业上广泛使用的测温元件，它能将温度信号转换成电势信号，同时配以测量仪表，便可以实现温度的测量。但是由热电偶的工作原理可知，只有当热电偶的冷端温度保持不变时，热电偶才是被测温度的单值函数。在实际测温时，由于热电偶的热端与冷端离的很近，...     

热电偶补偿导线的校准方法

热电偶用补偿导线指在一定温度范围内(包括常温)具有与所配的热电偶的热电动势的标称值相同的一对带有绝缘层的导线,用它们连接热电偶与测量装置,以补偿它们与热电偶连接处的温度变化所产生的误差。所以热电偶补偿导线的准确性直接影响到与热电偶整体测温的准确。     

补偿导线的鉴别和应用

连接热电偶与二次仪表的热电偶补偿导线在测温时起着重要的作用,所以必须重视对导线的正确鉴别和正确使用。在此谈谈有关的几个问题。 1.在一定的温度范围内,补偿导线与热电偶的热电性能应相同,即不同分度号的热电偶一定要配用相应型号的补偿导线。 2.使用补偿导线时,切勿将其极性接反。在热电偶的输出端或二次仪表的输入端,补偿导线的正负极必须与热电偶或二次仪表的极性对应连接,若接错将会产生很大的误差。 3.由于补偿导线是作为热电偶的延长线将参比端移至远方,故要求补偿导线在热电偶接线柱的两接点处温度相同。     

S型热电偶用新型廉价补偿导线合金丝的研究

测温用热电偶大多使用贵重金属,热电偶需要与测量仪表相连,连接线使用补偿导线,补偿导线用材料一般为较廉价的金属,价格比热电偶材料低得多,补偿导线产生的热电势必须与热电偶材料相匹配才能     

K型热电偶冷端补偿研究

针对在热试验过程中应用K型热电偶出现温度测量异常的情况进行研究分析,确认测量异常的原因是冷端补偿出现问题.从温度测量的原理入手进行分析,通过理论与试验相结合的方式阐述了冷端补偿的重要性.     

如何正确使用热电偶补偿导线

热电偶补偿导线已经广泛用于热电偶温度测量中。如果了解了热电偶补偿导线的原理、功能、作用方法和注意事项,就能充分发挥热电偶补偿导线的作用,否则适得其反。     

使用测温补偿导线应注意的问题

测温补偿导线实际上是一对在规定范围内 ( 0～ 10 0℃ )使用的热电偶丝。它的热电性能与热电偶的热电性能相似 ,通常用于热电偶与一次仪表的连接。使用补偿导线时 ,应注意几个问题。( 1)不能超出其规定温度范围使用一般情况下 ,只有在 0～ 10 0℃之间 ,补偿导线才有与热电偶一致的热电特性。如果与热电偶连接端高于 10 0℃或二次仪表端低于 0℃ ,就会使补偿线性能遭破坏。所以要注意观察其环境温度 ,以免造成损失。( 2 )补偿导线极性不能接反接反会造成热电偶产生的热电动势被补偿线的热电动势抵消一部分 ,使测量结果偏低。判别补偿导线极性…     

一种Ni-Cr-Mo镍基合金焊丝凝固过程元素偏析及相转变规律研究

为了对Ni-Cr-Mo镍基合金焊丝进行成分优化设计,本文通过热力学模拟计算方法研究了镍基合金焊丝凝固过程元素的偏析规律,并分析了合金元素对析出相的影响.研究表明:镍基合金焊丝平衡态主要的析出相为γ、M6C、P和μ相;在非平衡凝固状态下,随着凝固过程的推进从液相中析出M6C、P和σ相;随着Cr含量的增加,μ相的初始析出温...     

Anisotropic orthodontic force from the hollow super-elastic Ti-Ni alloy wire by transforming the wire cross-section

The purpose of this research was to devise a method for transforming the cross-section of the hollow super-elastic Ti-Ni alloy round wire and to examine the changes in its bending properties for clinical orthodontic application. The specimen wires were pressed with the use of heated pliers to transform the cross-sectional shape. As a result, transformation of the wire cross-section with super-elasticity was possible. As a verified by cantilever test and three-point bending test of the transformed specimens, a two-dimensional orthodontic force, which was different in each bending direction, was obtained. The hollow wire showed considerably high load level in the long axis along with markedly low load level in the short axis, which was mainly caused by the change in the moment of inertia by transforming the cross-section. It was revealed that, by transforming the wire cross-section of the hollow super-elastic Ti-Ni alloy round wires, anisotropic orthodontic force in bending properties could be obtained with super-elasticity.     

Mechanical behaviors of quasi-ordered entangled aluminum alloy wire material

Quasi-ordered entangled aluminum alloy wire materials with nominal porosity of 57–77% have been fabricated by assembling a set of aluminum alloy wires with diameter of 0.28 mm. The as-prepared materials display three-stage stress–strain behavior under uniaxial compressive loading, i.e., initial nonlinear ‘quasi-elastic’ deformation, strain-hardening ‘pseudo-platform’ stage, and the final densifying stage. The experiment indicates that the structural deformation mechanism dominates the initial stress–strain behavior. At the elastic stage, the materials reveal a significant ‘strain-hysteresis effect’. The compressive yield strength and the elastic modulus exhibit a significant dependence of porosity, i.e., both decrease as the porosity increases. The data obey the typical power law relationship suggested by Gibson–Ashby.     

接触线用铜合金剥层磨损行为

对高速电气化铁路接触线用Cu-Cr-Zr合金电磨损性能和磨损机制进行了研究.结果表明,在试验条件下,在合金接触线-黄铜粉末冶金滑块系统的电磨损过程中, Cu-Cr-Zr合金接触线的电磨损率随电流强度升高显著加强,由加载较小电流引起的磨损份额为0.16%～0.34%上升至电流强度较大时的7.82%～17.21%;未加载电流时,剥层磨损的体积损失在总磨损体积损失中所占比例高达94.70%,表明该机制为合金接触线主要机械磨损机制.     

高强度Fe-Ni膨胀合金丝材时效工艺研究

采用性能测试和显微组织分析手段，探讨了高强度低膨胀Fe—Ni合金丝材时效处理对合金膨胀系数及强度的影响规律。试验结果表明，采用较高温度时效（475℃），能够使碳化物能够呈弥散状析出，将有利于合金膨胀系数的控制，及合金强度的提高；而较低的时效温度（425℃）下，碳化物呈不均匀状析出，合金强化效果不明显，同时不利于膨胀系数的控制。     

柔索驱动并联机器人定位误差的柔性补偿法

提出了用人工神经元网络(ANN)补偿大射电望远镜(LT)中柔索驱动并联机器人(WDPR)系统动平台位姿误差的方法.为了提高WDPR的运动精度,建立了3种可行的误差补偿方案,并运用Levenberg-Marquart(L-M)算法训练了相应的3个神经元网络.标定仿真显示,基于索长补偿的柔性标定方案比基于动平台位姿补偿的标定方案好.研究结果为提高LT舱索系统的控制精度奠定了理论基础.     

Experimental investigation on the debonding strength in shape memory alloy wire reinforced polymers

The interfacial shear strength between the shape memory alloy (SMA) wire and epoxy matrix was evaluated experimentally using a single wire pull-out test. Moreover, the effect of pre-strain in SMA wires on the interfacial behavior was studied by pre-straining the SMA wires to 2% and 4% pre-strains. Experiments were conducted in both martensite and austenite phases of SMA. Results showed that pre-straining SMA wire in the martensite phase caused enhancement in interfacial shear strength due to recovery force generation. Further, 9.7% and 33% improvements in the interfacial shear strength were achieved at 2% and 4% of SMA pre-strain, respectively. However, the enhancement of interface behavior did not occur, when the SMA wires were subjected to pre-strain in the austenite phase.     

Experimental studies on electrical discharge wire cutting of Ni-rich NiTi shape memory alloy

The experimental investigation explores the effect of electrical discharge wire cutting (EDWC) variable parameters such as spark gap voltage, wire tension, pulse off time, wire feed rate, and pulse on time on the surface roughness, average cutting rate, and metallographic changes of Ni_55.95Ti_44.05 shape memory alloy (SMA). The spark gap voltage, pulse off time, and pulse on time have the significant effect on the surface roughness and average cutting rate, whereas wire tension and wire feed rate have the trifling effect. Ni_55.95Ti_44.05 SMA’s surface after EDWC is characterized by many discharge craters, microcracks, voids, and white layer of resolidified molten material. The elemental composition analysis of white layer using energy-dispersive spectroscopy divulges the deposition of the foreign element from the brass wire as well as the dielectric on the surface after EDWC. The machined surface as well as the wire electrode surface consists of various compounds of Ti, Ni, Zn, and Cu which have been identified by X-ray diffraction peak analysis.