Eatec has undertaken a large number of assessments of designs to confirm whether they will comply with their specifications and have an acceptable performance and life. Where necessary, Eatec has worked with the client to optimise the design such that it would provide the required performance. Brief details of some projects are given below
Assessment and optimisation of bearing housing castings
A number of bearing housings used on rail vehicles have been analysed to confirm that extreme and fatigue loadings will not cause failure of the castings. Designing the housings is challenging, as the space available is limited, the loads are relatively high, and the weight must be minimised. Therefore, the castings are generally complex in shape and the required degree of accuracy in the calculated stress levels can only be achieved by the use of finite element modelling. In order that the analyses provided accurate results, contact surfaces and preloaded bolts were used to ensure the interaction of the components which make up the assembly were represented correctly.
A large number of extreme loadcases and fatigue load cycles were considered in each assessment. Some of the fatigue life assessments were performed using fe-safe, (fatigue life prediction software), and others were performed using the relevant FKM Guidelines.
Generally, the designs met the requirements for the extreme loadcases, but in order to achieve the required fatigue life, optimisations of the main casting were necessary in many of the projects. The results from the finite element analyses were accepted by the regulator without any physical testing being performed on the bearing housings for many of the projects.
Assessment and optimisation of a plastic moulding
A high volume plastic snap-on top for a pharmaceutical product had to be able to accommodate significant variations in the local geometry of the top of a glass bottle without experiencing excessive stress levels. A non-linear finite element analysis was performed, modelling the interaction with the bottle and the assembly tooling.
The analysis showed that the initial snap-on top design could not tolerate the full range of variations in the bottle geometries, and hence an optimisation exercise was undertaken to improve its performance.
Assessment of a pontoon
A pontoon was designed to be used in the decommissioning of submarines. In-service, the pontoons will experience high localised loads applied by the strops which pass under the submarine. An assessment was required to determine the peak stress levels which would occur in the pontoon under the most onerous loading case, and whether buckling of local sections would occur.
A detailed finite element model of one half of the pontoon was generated using shell elements. The assessment showed that the majority of the structure experienced stresses which were below the allowable value, but that stiffening was required in local regions to prevent excessive stress levels and buckling from occurring.