Manufacturing Engineer and Factory Safety Engineer Discusses Bungee Cords

Manufacturing engineer discusses bungee cord safety from a safety engineering view point. Stretching a bungee cord imparts a significant amount of potential energy into the system that can be released and make the end hook a dangerous projectile. There are safety warnings on most cords; however, these are often ignored or torn off. It has been suggested to limit the extension (to 50%) to limit the danger. Streth tests were performed (upper left photo). to examine the difference between a limited bungee cord and one without limits. The bungees were stretched and the force-distance data ploted (upper right figure) The area under each curve is the stored potential energy. This is converted to kinetic energy (KE). From the KE the hook velocity can be calculated. The unlimited bungee generated a maximum hook velocity of 100mph. The maximum hook velocity for the limited bungee is 70mph. Both bungees can still be dangerous.

It appears that the limited bungee was made more robust to increase the holding force for 50% elongation. This has a negative effect on this cord's safe use.

Manufacturing Engineer and Safety Engineer Discusses Crane Safety

Manufacturing Engineer and Safety Engineer advises, for factory safety, that if a crane is being used to lift objects over and into baths that contain harmful liquids such as acids, caustics and high temperature liquids. the event should be treated as a "lock out tag out" type of event. All personnel should be cleared from the area, and the crane operator should be behind an appropriate protective screen. If there is a crane malfunction and a splash occurs, no one will get hurt.

Glass Failure Analysis of Swimming Pool Tiles

Glass failure analysis expert performs a failure analysis of cracked glass swimming pool tiles. The photo on the upper left is of one of the cracked tiles. This is a clear glass tile made from re-cycled glass. The failure analysis, photo on the upper right, shows that these tiles were cracking from the backside of the tile. In this particular pool, only the clear glass tiles cracked. The colored tiles in the same pool did not crack. Light transmission measurements showed that the clear tiles transmitted more infra red light. The present hypothesis is that the infra red light passed through the clear tiles and preferrentially heated the mortar on the tile backside. The heating created tensile stresses and cracking on the tile backsides. The heating was more intense for the clear tiles; this is why they cracked.

Glass Bottle Failure Analysis

Glass failure analysis expert performed a root cause failure analysis on a bottle failure. The cap on this bottle had not been removed. The failure analysis revealed a manufacturing defect on the bottle interior. On the upper left photo is a 30X photomicrograph of a portion of the origin on the fracture surface. The arrows show the travel direction of the crack exiting the origin. On the upper right is a 30X photonicrograph of the origin as it appears on the interior surface of the bottle. There is a "chip" associated with the origin; therefore, this is a product defect on the bottle interior.