Contact electric resistance testing

There has been much corrosion coupon testing in kraft and soda liquors. Electrochemical polarization, linear polarization resistance testing, and contact electrical resistance testing have also been used. 

The extent of galvanic action in atmospheric exposure may also be restricted by the development of corrosion products of high electrical resistance between the contacting surfaces — this is especially likely to occur if one of the metals in the couple is an iron or steel that will rust. In long-time tests such possible interruptions in the galvanic circuit should be checked by resistance measurements from time to time so as to determine the actual periods in which galvanic effects could operate. 

There is a curious anomaly in the performance of these materials which may be related to the complex effects of purity and temperature reviewed in Chapter 4. Niobium diselenide (Nb 862) is a better conductor than molybdenum disulphide, but apart from one report in which the test conditions were unconventional , compacts containing molybdenum disulphide have generally performed better than those containing niobium diselenide, in terms of wear, electrical resistance and electrical noise. Apart from the compacts listed in Table 12.13, the superiority of molybdenum disulphide was also confirmed in contacts with silver and graphite . 

The same membranous material as mentioned in 1) having a thickness of 100 jjl was set in a reactor of the design which would allow only one surface of the membrane to contact with reaction reagents. Thereafter, the reactor compartment was filled with vapour of phosphorous pentachloride ( at 170°C for an hour ) to have one surface of the membrane reacted. The reflective infrared spectrum and dyeing test respectively showed that the membrane had sulfonyl chloride groups and that approximately 5 JJL of non-dyed layer was stratified at the membrane surface where phosphorous pentachloride had contacted. The electric resistance of this membrane was about 1500 ft- cm2 in a 1.0 N hydrochloric acid solution at 25°C when measured by 1000 cycle A.C. The electric resistance of the same membrane before the reaction with phosphorous pentachloride was only 0.38ft - cm2 under the same conditions. 

The Universal Nano-i-Micro Materials Tester (UNMT) has been developed to perform a variety of the common adhesion tests [2]. During any of them, it can simultaneously measure contact or surface electrical resistance displacement, deformation, or depth of penetration contact acoustic emission temperature forces in all three directions and digital video of the contact area. This report covers evaluation of the adhesion and delamination properties of coatings by the scratch test. 

In addition, the efficiency of electric contact between bipolar plates and gas diffusion layers was measured using special test station comprising a hydraulic press with a temperature control, current supply and control systems. The purpose of provided measurements is the comparative analysis of parameters of different bipolar plates and gas diffusion layers, and also obtaining of the necessary data for use in calculations on mathematical model. Resistance tests of gas diffusion layers and bipolar plates were performed both in a longitudinal direction (four-contact method) and in a transverse direction. 

Insulation resistance n. (1) The electrical resistance between two conductors or systems of conductors separated only by an insulating material. The resistance of a particular insulation may be measured by dividing the voltage difference applied to two electrodes in contact with, or embedded in a unit area of the specimen by the current flowing between the electrodes. Tests for thermoplastics include ASTM D 2633, section 10.02. (2) See thermal resistance. 

EIA 364-B, Low Level Contact Resistance Test Procedure for Electrical Connectors, Electronic Industries Alliance, 1990. 

Electrical testing is another class of reliability testing. The function of a solderjoint formed with the surface finish can be measured by burn-in testing, electrical functional tests, and/or high-current-density application for extended periods. The contact resistance of an unassembled surface finish is an important measurement. The PCB finish, when exposed to heat and humidity metrics, as well as environmental exposure, may need to pass a sensitive four-point probe contact resistance check. 

Furthennore, some materials, including medical textiles, have the potential to cause allergy or irritation. The sensitization potential of the material is therefore required to be tested. The ISO 10993-10 assesses the possible contact hazards from chemicals released from the devices, which may produce skin, mucosal, or eye irritation and skin sensitization. Currently, there has been no satisfactory in vitro test to eliminate the requirement for in vivo testing to evaluate irritation. However, the rat skin Transcutaneous Electrical Resistance (TER) test and the human skin model test have been internationally validated and accepted as alternative tests to assess the skin corrosion with chemicals (OECD, 2009a,b). To perform the test, an animal (rabbit) with the healthy intact skin needs to be used and the fur on the back of animal is clipped 24-4h of testing with approximate size of 10cmX 15 cm and then 0.5g or 0.5 mL of materials apply to the site and then the application site is covered with... 

The direct measuremoit of the sq>aration between two bearing surfeces of metal-on-metal hip implants tested in a hip simulator under normal walking conditions was carried out by Dowson et al (2000) using the above electrical resistance technique. The mode of lubrication in flieir experimental study was mixed, with some periods of very effective surface separatioi and others of metal-on-metal contact in each simulated walking cycle. Using the same technique, Smith et al (2001a) have demonstrated surface separation of the femoral head and acetabular cup by a lubricating film in ceramic-on-ceramic hip implants. However, it was not clear whether protein films enhanced the sur ce separation in both of these studies. 

Generally, having a nonsolder surface finish to bond a conductive adhesive improves contact resistance [49]. For example, conductive adhesives perform well with palladium-based terminated components. Lead-free board finishes such as nickel/gold and copper/palladium have been evaluated. Failures at the interface between component terminations and conductive adhesives is a typical failure mode observed in durabiUty tests, and also the cause of an increase in electrical resistance. Oxidation and corrosion of Sn-Pb finishes take place at the interface [21]. 

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