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The quantification of contact area and pressure distribution in a bolted joint is essential information, as it determines the integrity of the coupling. Current bolted joint design standards are based on analytical solutions of the pressure distribution, which, due to the inherent assumptions, frequently do not accurately represent the real conditions in a joint.This study uses a non-intrusive ultrasonic technique to quantify the contact pressure distribution in a bolted connection. The advantage of this experimental technique is that the effect of actual contact conditions can be determined. An ultrasonic wave is focused onto the clamped interface, and the reflected sound signal recorded. In areas where the contact pressure is high, most of the ultrasound is transmitted, and the reflected sound signal is weak. Whereas, when the contact pressure is low the vast majority of the ultrasound is reflected back. A parallel experimental calibration is then used to find the relationship between the reflected sound signal and contact pressure. In this way the pressure distribution in a clamped interface is determined for a series of different bolt torques. 1Two different interfaces were investigated; the first consisted of two ground surfaces clamped together, and the second a turned profile pressed against a ground surface. The effect of a washer underneath the bolt head was also considered. The turned profile was found to cause the contact to spread; there was also a certain degree of fragmentation leading to higher peak pressures than in the ground interface case. With a washer positioned under the bolt head for the turned case, the clamping performance of the bolt was improved.

No abstract

A large percentage of apples are wasted each year due to damage such as bruising. The apple journey from orchard to supermarket is very complex and apples are subjected to a variety of static and dynamic loads that could result in this damage occurring. The aim of this work was to use a novel ultrasonic technique to study apple contact areas and stresses under static loading that may occur, for example, in bulk storage bins used during harvesting. These results were used to identify load thresholds above which unacceptable damage occurs. They were also used to validate output from a finite element model, which will ultimately be developed into a packaging design tool to help reduce the likelihood of apple damage occurring.

No abstract