This paper reports on electrical resistance vs. aging time for the response of polyaniline films under exposure to water, ethanol and nitric acid (HNO3) solution. Camphor sulfonic acid-doped polyaniline films were prepared by a "doping-dedoping-redoping" method, the morphology and microstructures of the films were characterized by a scanning electron microscope and an x-ray diffractometer, the electrical resistance was measured by a four-probe method. It was found that a lower amount of water molecules infiltrating the film can decrease the film's resistance possibly due to an enhancement of charge carrier transfer between polyaniline chains, whereas excessive water molecules can swell inter-chain distances and result in a quick increase of resistance. The resistance of the film under exposure to ethanol increases and becomes much larger than the original value. However, HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid. These results can help to understand the conduction mechanism in polyaniline films, and also indicate that the films have potential application in chemical sensors.
In the elastoplastic fracture analysis for pipelines steel X60,J-A2 two parameter approach was adopted to predict the failure pressures of pipelines with surface cracks.In order to apply the experimental JR-Δa curves measured by standard laboratory specimens of steel X60 to real cracked components,the finite element analyses were performed for a single edge notched compact tension(CT) specimen and pipelines with axial surface crack.The J-A2 solution was used to quantify the constraint condition in the crack-tip fields.It shows that the inner crack-tip constraint levels of pipelines are close to the exterior ones with the same crack depth.The inner crack-tip constraint levels are slightly higher relatively.But their crack-tip constraint levels are lower than CT specimen.From the result of finite element analysis for pipelines,the fracture failure pressures of pipelines were predicted.The fracture failure pressures with fracture mechanics analyses are lower than those with PCORRC for pipelines steel X60.
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