09 Jan Acceptance Criteria
When a physical test or a FE analysis has been performed, the results are usually compared to an acceptance criterion to determine if the design is suitable. Acceptance criteria can either be defined by the end user or from relevant engineering standards (BSEN, ASME, etc).
An acceptance criterion is usually set as an allowable below or above which all relevant results should be. Suitable acceptance criteria must be quantifiable and testable (e.g. ‘FoS [https://fea-solutions.co.uk/factor-of-safety/] of greater than 1.0′ vs ‘does not break’).
It is important to consider local material properties when defining acceptance criteria. For instance, different acceptance criteria may be required in the heat affected zone of a weld [https://www.fea-solutions.co.uk/heat-affected-zone/], or if a part was at elevated temperatures. All acceptance criteria should be clearly agreed to prior to the FE analysis being run.
Examples of common acceptance criteria include:
Metals: FoS of greater than 1.5 on yield strength for von-Mises stress.
Composites and ceramics: FoS of greater than 1.5 on yield strength for maximum principle stress.
Buckling: Buckling load multiplier should not exceed 2 (PD5500 Standard)[https://www.fea-solutions.co.uk/linear-buckling-analysis/]
Thermal: Temperatures not exceeding a given value (EN 1993-1-2 (Steel Structures – Fire Design).
Vibration: Natural frequencies must avoid certain critical ranges to prevent resonance [https://fea-solutions.co.uk/resonance/]. For example, BSEN 1991 states walkways must avoid a minimum natural frequency to avoid excitation from pedestrian traffic. If the frequency is below that value, then a more detailed check must be performed to evaluate the response.
It is important to note that some acceptance criterion are enforced by law, whereas some are recommendations. Not complying with standards such as national building regulations (e.g. UK Building Regulations 2010) and EU statutory instruments (e.g. Pressure Equipment Safety Regulations) can lead to prosecution.
Although standards such as Eurocodes (EN 1990 – 1999) are not laws by themselves, they often become de facto legal requirements due to contractual agreements or if compliance is claimed.
Please call us today on +44 (0)1202 798991 for any engineering analysis requirements you might have.