Conversion of short fatigue cracks into a long crack

This paper presents a method for the statistical processing of results of initiation and propagation of short fatigue cracks. The distribution of the lengths of these cracks followed a Weibull distribution function. The value of the size parameter of this distribution grows with the number of cycles, but the value of the shape parameter declines as the number of cycles increases. A study of the modal value of fatigue crack lengths as a function of the number of cycles yielded a statistical criterion defining the conversion of the short fatigue crack initiation and propagation stage into the long fatigue crack propagation stage. One condition for this conversion is a zero magnitude of the first derivative of the modal value of fatigue crack lengths by the number of cycles. When the dependence of the Weibull distribution shape parameter and size parameter upon the number of cycles was inserted in this condition, solution of the resultant expression revealed the critical number of cycles that is necessary for the formation of a long fatigue crack

Research on the detection of methane concentration using sensor with supporter catalyst filled element on constant temperature

Based on the basic principle of sensors with supporter filled element that measures the methane concentration, a method for designing Weston bridge by using the sensor and the reference element is proposed and the mathematical model of the automatic temperature control and the measurement of methane concentration is developed. The measurement results show that this design expands the measuring range, reduces burning-knot and vaporization of catalyst and extends the service life of the supporter catalyst filled element.link_to_subscribed_fulltex