Experimental Study on Low Temperature Sn-Bi Solder Paste

2014 ◽  
Vol 543-547 ◽  
pp. 3806-3809
Author(s):  
Yan Jiang ◽  
Li Da Sun ◽  
Zi Jing Li ◽  
Zhao Long Huang

For lack of existing low temperature solder paste , developed a low-temperature Sn-Bi solder paste, focused on finding the optimal formula , at the same time on the flux of the solder paste, is printing performance and wettability can be tested through performance test to find the optimal flux formula.

Author(s):  
Е.В. Волкова

В данной статье обсуждается вопрос о возможности удачного обжига практически сырых глиняных сосудов в примитивных обжигательных устройствах: кострищах и очагах. Для исследования этого вопроса был поставлен эксперимент. Сосуды из трех разных формовочных масс с разной степенью высушености были обожжены в углубленном в грунт очаге в восстановительной среде длительное время (проведено 3 обжига) и в наземном очаге в полувосстановительной среде с использованием навоза коровы в качестве единственного топлива (1 обжиг). В результате автором были получены следующие выводы. Вопервых, для обжига в очаге с навозом в качестве основного топлива вполне пригодны сосуды 2 дневной сушки, т. е. практически сырые. Наилучшим образом обожглись сосуды, сделанные из глины и шамота. Для сосудов, слепленых из чистой глины и глины с навозом, имевший место подъем температуры был слишком резким и привел к образованию трещин. Возможно, при обжиге только во влажном навозе с более медленным подъемом температуры без трещин оказались бы все сосуды. Во вторых, можно считать почти установленным, что сосуды после 2 дневной сушки вполне пригодны для длительного низкотемпературного обжига в восстановительной среде. Но для полной веренности в этом необходимо проведение ряда дополнительных экспериментов. В третьих, оптимальным для обжига недосушенных сосудов является рецепт глина навоз шамот . The paper explores options for successful firing of basically wet clay vessels in primitive firing constructions such as fire pits and hearths. An experiment was carried out to study this issue. Vessels from three different masses of clay with different degrees of dryness were fired in a hearth sunk into soil in a reducing environment for a long time (three firings) and in a surface hearth in a partly reducing environment with the use of cattle manure as the only fuel (one firing). The following conclusions were derived. Firstly, firing in a hearth with manure as main fuel is quite suitable for vessels that were dried for two days, i. e. basically wet vessels. The best result from firing was obtained for vessels made from clay and chamotte. The increase in temperature was too steep for vessels made from pure clay and clay with manure resulting in cracks. Maybe, there would have been no cracks in any vessels in case of firing in wet manure with a more gradual increase in temperature. Secondly, it was established that, after two days of drying, vessels were quite ready for lengthy low temperature firing in a reducing environment. However, to be absolutely sure in this, additional experiments are needed. Thirdly, an optimal formula for firing underdried vessels is as follows: clay mature chamotte.


Machines ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
Jing Wang ◽  
Zhihua Wan ◽  
Zhurong Dong ◽  
Zhengguo Li

The harmonic reducer, with its advantages of high precision, low noise, light weight, and high speed ratio, has been widely used in aerospace solar wing deployment mechanisms, antenna pointing mechanisms, robot joints, and other precision transmission fields. Accurately predicting the performance of the harmonic reducer under various application conditions is of great significance to the high reliability and long life of the harmonic reducer. In this paper, a set of automatic harmonic reducer performance test systems is designed. By using the CANOpen bus interface to control the servo motor as the drive motor, through accurately controlling the motor speed and rotation angle, collecting the angle, torque, and current in real time, the life cycle test of space harmonic reducer was carried out in high vacuum and low temperature environment on the ground. Then, the collected data were automatically analyzed and calculated. The test data of the transmission accuracy, backlash, and transmission efficiency of the space harmonic reducer were obtained. It is proven by experiments that the performance data of the harmonic reducer in space work can be more accurately obtained by using the test system mentioned in this paper, which is convenient for further research on related lubricating materials.


Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2249
Author(s):  
Bei Chen ◽  
Fuqiang Dong ◽  
Xin Yu ◽  
Changjiang Zheng

In order to solve the problems caused by asphalt diseases and prolong the life cycle of asphalt pavement, many studies on the properties of modified asphalt have been conducted, especially polyurethane (PU) modified asphalt. This study is to replace part of the styrene-butadiene-styrene (SBS) modifier with waste polyurethane (WP), for preparing WP/SBS composite modified asphalt, as well as exploring its properties and microstructure. On this basis, this paper studied the basic performance of WP/SBS composite modified asphalt with a conventional performance test, to analyze the high- and low-temperature rheological properties, permanent deformation resistance and storage stability of WP/SBS composite modified asphalt by dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The microstructure of WP/SBS composite modified asphalt was also observed by fluorescence microscope (FM) and Fourier transform infrared spectroscopy (FTIR), as well as the reaction between WP and asphalt. According to the results of this study, WP can replace SBS as a modifier to prepare WP/SBS composite modified asphalt with good low-temperature resistance, whose high-temperature performance will be lower than that of SBS modified asphalt. After comprehensive consideration, 4% SBS content and 15% WPU content (4 S/15 W) are determined as the suitable types of WPU/SBS composite modified asphalt.


Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 98
Author(s):  
Chao-Yong Shen ◽  
Xiang-Yun Huang ◽  
Yang-Yang Chen ◽  
Yu-Hong Ma

In this research we conducted a sensitivity experimental study where we explored the dependency of the shear strain on the seismic properties of bearings, namely lead rubber bearing (LRB) and super high damping rubber bearing (SHDR). The factors studied were vertical pressure, temperature, shear modulus of the inner rubber (G value), loading frequency, and loading sequence. Six specimens were adopted, i.e., three LRBs and three SHDR bearings. A series of test plans were designed. The seismic characteristics of the bearings were captured through a cyclic loading test, which included post-yield stiffness, characteristic strength, area of a single cycle of the hysteretic loop, equivalent stiffness, and equivalent damping ratio. A whole analysis of variances was then conducted. At the same time, to explore certain phenomena caused by the factors, an extended discussion was carried out. Test results showed that the temperature is the most dominant feature, whereas the G value is the least contributing factor, with the effect of the loading frequency and the loading sequence found between these two. The increment of the post-yielded stiffness for LRB from 100% to 25% is a significant reduction from a low temperature to high one. The slope of the characteristic strength versus the shear strain for LRB under high temperature is larger than the one under low temperature.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Xiao Guo ◽  
Wen Xu ◽  
Shi Wang

Taking the construction of a concrete-filled steel tube (CFST) arch bridge (part of the Sichuan-Tibet Railway) in low temperatures as the test site, firstly the deformation performance test of concrete was carried out. Following this initial testing, measurement of compressive strength and shrinkage performance was conducted in large-diameter CFSTs under a variety of curing conditions. Experimental results showed that the expansion effect of Ca-Mg composite expansive agent in concrete was better than that of other expansive agents at any stage. Under low-temperature curing (0°C), the sampling strength of the large-diameter CFSTs reached 73.5% of the design strength at 28 d in the presence of a nonthermal curing system. The design strength itself was reached, when a curing system involving a thermal insulation film was applied, and use of this film also led to improvements in concrete shrinkage. The results suggested that a Ca-Mg composite expansive agent, combined with an insulation film curing system, should be the technique selected for concrete pumping construction of CFST arch bridges in Tibet.


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