A hypodermic pressure manometer utilizing the bonded wire resistance strain gauge.
The recent development of the bonded resistance wire strain gauge has led to its use as a device for measuring physiological pressure phenomena. Further application of the strain gauge has been as an instrument for measuring intravascular blood pressures and other pressure phenomena in biology and medicine.
A new transducer for measuring small pressure differences at high absolute pressure
The design, construction and use of a novel differential pressure transducer is described. It consists of four gages mounted on a steel diaphragm and connected to form a Wheatstone-bridge circuit. The line pressure, maximum 10,000 psi, acts directly on the gages. The response of the transducer is independent of the line pressure and temperature and is linear up to 350-psi pressure differential. The probable error is less than one percent of the full-scale differential.
Numerical analysis of surface crack propagation in flexible pavements using XFEM and cohesive zone model
Surface initiated (top-down) cracking in the longitudinal direction of pavements has become a predominant mode of failure in thick asphalt pavements. Most previous researchers studied crack propagation using the traditional Linear Elastic Fracture Mechanics (LEFM) method by calculating the stress intensity factor around the crack tip. In this paper, Extended Finite Element Method (XFEM) was used to study the key factors causing surface initiated crack propagation under surface tension and/or shear. A two-dimensional (2-D) finite element (FE) model for a two-lane flexible pavement was built to predict pavement responses and crack propagation potential under various scenarios. It was found that surface tension is the major driving force for crack propagation when the crack is at some distance away from tire loading. The results show that the distance from the location of crack to tire loading, the depth and direction of the crack, and the modulus ratio between the hot-mix asphalt (HMA) layer and the base layer have significant influences on crack propagation under surface tension. On the other hand, this study shows that shear stress can induce surface initiated crack propagation near the loading area as the shear resistance of material becomes low at the high temperature.