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The Chalice Engineering Newsletter - No. 3 October 2004 |
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This newsletter replaces the CADtips newsletter and is distributed on an 'opt-in' basis. If you wish to unsubscribe, please email, requesting your removal from the mail list. |
In this issue:
Case Study - Using FE Models In Conjunction With Codes of Practice
We recently completed an analysis of a welded steel 'Sliding Frame' for Saxlund International Ltd of Southampton. This patented design is the principal part of a hydraulically operated silo discharge machine. Starting with the companies 2D drawings, we built a 3D model of the structure, from which we generated a suitable finite element mesh, applied the loads and solved for stresses. The results from the model were used in conjunction with BS 7608 (Code of Practice for Fatigue Design and Assessment of Steel Structures) to determine if the welds were adequate.
Although obtaining stresses from a linear static analysis like this is normally straightforward, evaluating them for a welded structure often is not. Weld fatigue strength is usually specified in standards or codes of practice like BS 7608, BS 8118 (aluminium) and BS PD 5500 (pressure vessels). Using FE stress results in conjunction with these codes requires an appropriate scheme for choosing the correct type and location of the stresses in the model in order that they can be legitimately compared with the allowable stresses from the codes.
We carried out several analyses as the design evolved during the course of the project. The final design included several improvements identified from the analysis of preceding designs and this was subject to a final analysis.
One of the features in the design of the sliding frame was a scalloping or removal of material from one side of the rectangular cross-sections from which the frame is made. As shown below, high stresses occurred where this feature extended into the weld region, where the allowable values, as dictated by BS 7608, are reduced well below that of the parent material. Consequently, one of our recommendations was to reduce the length of this scallop feature so that it avoided the weld region.
If you are concerned about the integrity of your welded or bolted structure, contact us to discuss how we can help.
Company News
ISO9001:2000 Certification - Chalice has continually improved and updated its quality management system for analysis, which is based on NAFEMS' (www.nafems.org) interpretation of the previous quality standard, ISO9000. We are now commencing the process of obtaining full ISO9001:2000 certification for all our business activities. We hope to attain accreditation within the next 9 months. Subsequent newsletters will discuss our progress.
Professional Indemnity Insurance - Chalice has re-acquired £1m Professional Indemnity cover through Randell Dorling Ltd, London.
Improving Productivity for Manufacturing Companies - As a DTI Centre of Excellence in Manufacture (CEM), we are currently undertaking subsidised design projects for two local manufacturing companies, to help improve their product's design. If you are a manufacturing company based in Yorkshire and Humber, read more about how CEMs like Chalice may be able to help your company here.
This is the third newsletter provided by Chalice Engineering, which has now changed to a quarterly frequency. This was formerly the CADtips newsletter but has now changed to the current format.
Acknowledgements: Our thanks to Frank Boyles of Saxlund International, for permission to reproduce the details of their product in the foregoing case study.
Chalice Engineering Simulation Ltd, The Red House, 70 Gledhow Wood Ave, Leeds LS8 1NX
T 0113 266 7884
F 0113 266 7913
E mark.chillery@chalice-engineering.com
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