Case Studies

In this project the goal was to maximise the torsional stiffness of an SUV body structure by the replacement of a pair of C-pillar reinforcement panels.  The new composite parts would replace aluminium pressings but had to remain at the same weight and crucially be cost competitive.
 
The developed solution was a short fibre carbon filled PA6 injection moulding which incorporated local continuous fibre reinforcements.  Predictive analysis was used to optimise the location, extent and layup (fibre direction) of the reinforcements so that the minimum amount of ‘premium’ material was used whilst achieving a significant performance uplift.
 
The result was an improvement of 7% on the overall torsional stiffness of the vehicle body structure.  With the new parts and process, production rates were achievable, cost was comparable, and there was no weight penalty.

Working with BAC, this project aimed to re-engineer the Mono supercar’s space frame, tubular chassis using a niobium enhanced steel. Engenuity started with data acquisition, instrumenting the car during high speed testing to benchmark existing chassis performance. 

Using Engenuity’s on site material laboratory, the niobium microalloyed steel was characterised with material cards generated for accurate simulation. Engenuity’s engineering team then used their decades of experience of race car and supercar development to optimise the chassis against multiple load cases. This expertise led to a mass reduction of 18% from a chassis that had already been designed for minimal weight by automotive experts. Achieved working within strict constraints in terms of packaging and manufacturing tooling, the new chassis also maintained durability and torsional stiffness while improving roll over protection. 

Engenuity’s FiRMA (Failure in Random Material Architectures) design and analysis software allows structural components to be made using chopped and recycled material with confidence, whilst maintaining weight saving potential.

SMC (Sheet Moulding Compound) benefits from low cost constituents (including recycled fibre) coupled with a high production volume ability and part reproducibility. It allows for the design of components with more complex geometry.

The traditional design and analysis methods applied to SMC component development is pessimistic and incompatible with the nature of the material and its random structural characteristics. This leads to over-weight components and higher costs due to a lack of real part performance prediction.

The superior FiRMA method introduces a method of material characterisation coupled with stochastic analysis that generates a realistic part performance distribution. This permits a better understanding of part performance and leads to reduced weight and cost.

Styling is all about detail but so is fatigue. Alloy wheels are a particular example of where the two are intertwined; where the styled structure is on show but must deliver on performance – often with neither analyst or stylist willing to budge. Fortunately, small changes to radii and sweeps can significantly influence fatigue life avoiding the need to compromise the concept form. However, to achieve this whilst ensuring a product doesn’t enter the market under engineered, an accurate approach to fatigue prediction is needed. A wheel undergoes non-trivial cyclic stresses with every revolution (see below) that cannot be accurately predicted without detailed FEA (Finite Element Analysis). Coupled with a variety of loading scenarios, the envelope of stresses that any particular point on the wheel experiences in its life are diverse.

One of the first projects Engenuity undertook, after its formation in ‘93, was the analysis of the Lister Storm wheel set and since then, Engenuity have evolved and refined their approach to wheel fatigue in order to calculate the most accurate fatigue damages. Track day racing; A and B road day to day riding; rider only or rider and pillion – any combination of pressure, contact patch and brake/acceleration loads can be simulated and fatigue damages calculated.

In order to maximize the accuracy of this approach, fatigue curves are determined using our state-of-the-art inhouse materials test laboratory accounting for cast and machined finishes.

Methodology: 

– Material selection and development to maximise tank w/w efficiency

– Material testing for processability

– Material characterization to allow accurate simulation

– Structural simulation and layup optimization

– Process development

– Prototype tank manufacture

– Testing and model correlation

– Engenuity create and analyse P-type finite element models with no de-featuring from the CAD geometry. This enables accurate stress recovery in the small features (i.e. internal fillet radii of a casting) likely to be crack initiation sites.

– Fillet weld geometry is explicitly modelled to ensure fidelic load transfer between parts. Fatigue calculations based upon BS7608 standards provide unrivalled fatigue life predictions – correlated with physical test results across many applications.

– Information from the analyses quickly focusses the structural design of the component. Iterations devised in collaboration with the client to ensure factors such as manufacturability are not overlooked, are used to develop the design – increasing fatigue performance and reducing weight by elimination of redundant material.

Modal development controls resonant behaviour

This processing screen uses an eccentric shaft at a fixed running speed to excite the aggregate material. For extended life it is critical that the natural modes of vibration do not coincide with the driven frequency.

APPROACH:

Engenuity built detailed finite element analysis models and conducted design iterations to optimise the stiffness of the structure .

RESULT:

Prototype testing revealed that the resonant frequency was within 1% of that predicted.