Analysis of a Stiffened Access Panel

Learning Outcome

Set up and validate an efficient and accurate FE model of a complex engineering component, assembly or structure under non-linear and/or dynamic loading.

Critically evaluate the output from non-linear and general dynamics FE analysis.

Detail of the task

Figure 1 shows details of a stiffened (the stiffening ribs are 50mm deep) access panel. The panel forms part of a large pressure containment and is used to provide access to load components into the containment. When closed it can be considered to be firmly clamped all around its outer circumference.

The panel is fabricated from 6mm thick 316L stainless steel with the following material properties:

- Young's Modulus, E=200GPa
- Poisson's Ratio, ν=0.3
- Density, ρ=7800kg/m³

Under normal operating conditions the panel is subjected to the following two loading conditions:

- A constant pressure on the non-stiffened side of 5kPa (5000N/m²)
- A pressure pulse on the non-stiffened side of 5kPa (5000N/m²) which varies with time according to figure 2

You are required to undertake a finite element analysis of the plate to assess its suitability by performing the following studies:

- A static study to determine the deflection of the centre of the plate and to examine the stresses in the plate due to the first loading condition
- A modal analysis (frequency analysis in ABAQUS) to determine the natural frequencies of vibration of the plate

- A linear dynamics study (modal dynamics in ABAQUS) to determine the motion of the centre of the plate and examine the stresses in the plate due to the second loading condition
- A general implicit dynamics study to determine the motion of the centre of the plate and examine the stresses in the plate due to the second loading condition

For the two dynamic analyses you should consider first the undamped behaviour of the plate and then assuming a damping coefficient (direct modal in ABAQUS for linear dynamics) of 0.05, you will need to convert this into Rayleigh damping for the general dynamics study, in this case you should assume only mass proportional damping, i.e. that β=0. An analysis duration of 0.5s will be sufficient.

In addition to the normal operating conditions defined above you also need to consider a potential fault condition where the pulse pressure defined in figure 2 increases from 5kPa to 100kPa (100,000N/m2). In order to do this you should perform an explicit dynamics analysis for the damped case (using the Rayleigh damping defined above) to determine the motion of the centre of the plate and examine the stresses in the plate. For this analysis you may assume the following plastic material properties:

What you should hand in

You should submit a report which is between 1000 words and 1500 words in length together with appropriate hand calculations, diagrams, contour plots, graphs etc. Note your report should be no more than 1500 words in length.

The structure of the report should be as follows:

- Finite element modelling - this section should describe the modelling strategy adopted to determine the static and dynamic performance of the plate, i.e. element type, loading, boundary conditions, definition of solution controls for each analysis procedure

- Results - this section should contain a full description of the results obtained together with appropriate contour plots and graphs, for example, mode shapes and centre point displacement for each analysis procedure.
- Results verification - this section should contain an assessment of the accuracy of the results obtained by the application of robust validation checks.
- Discussion - this section should contain a full discussion of the results obtained.
- Conclusions