Hounsfield Balanced Impact Machine (HBIM)
The operating manual for the Hounsfield can be found here.
The Hounsfield Balanced Impact Machine (HBIM) strikes a specimen, held in place with a spring forced wedge to secure the steel, with its pendulum arms; allowing energy to transfer to the specimen and causing failure. It can transfer a maximum of 65Nm. The machine works by securing the arms on tups on the top of the structure, then a small hammer is flicked to actuate the tups. This releases the arms, and the pendulum motion occurs to break the specimen. Releasing the arms in this method makes sure that hands, fingers and any other breakable appendages are out of the way of the moving parts. After the swing of the pendulum arms, they secure via finely geared teeth and lock into place. A lever then has to be turned to allow the arms to come down to the neutral position, again a safety measure to be sure that hands are out of the way of swinging pendulums. The HBIM is secured to a wooden platform, which is clamped to a table for the duration of the experiments.
The HBIM was selected for its compact size and manageable weight, its availability, its ease of loading samples, and the ease to machine specimens in the available workshop. The Hounsfield uses round bar steel machined into 1¾” (44.5mm) long and (7.9mm) diameter samples. A small notch is made in the specimen to act as a stress concentrator to break the sample more easily and consistently.
Hounsfield Balanced Impact Machine
Impact tests were taken over a range of temperatures to give a full range of operating temperatures for which information can be compared, in the form of a Brittle Ductile Temperature Graph. The below table shows what substances were used to get the specimens to the correct temperature, before placing them into the HBIM.
There is more information on the handling of these substances in the report.
Additionally, impact tests create an impact surface which would allow fractographic analysis on specimen failure using a Scanning Electron Microscope (SEM). However this project was unable to conduct SEM analysis.
Specimens before fracture, post quenching
