Introduction to the Finite Element Method Practical II Assignment 2026 | University of Twente

Introduction to the Finite Element Method Practical II Assignment 

Practical Exercise 2:

Designing a Table with Optimised Rib Placement

Assignment

Plastic products often require increased stiffness to withstand peak loads and minimise displacements. To achieve this, rib supports are commonly used to enhance the product’s structural integrity. The incorporation of rib supports in a plastic product not only improves its mechanical performance but also brings economic benefits. By appropriately designing a product with rib supports, the amount of required material can be reduced, resulting in decreased material costs and ultimately lowering the sales price. However, it’s essential to consider that rib supports can have aesthetic disadvantages as they can impact the overall appearance of the product.

Design a lightweight table that can withstand applied loads while minimising deflection. A technical drawing with the complete set of dimensions for the initial design is attached in Appendix A. The design improvement process will involve determining an adequate rib support structure under the table plate. You are free to adapt the placement and cross-section of the rib supports. Keep the dimensions of the table plate and legs (including their thicknesses) as they are in Appendix A.

Requirements

The designed table has to satisfy the following properties.

• The table must handle a distributed load of 2.5 kPa.
• Maximum deflection should not exceed 5 mm.
• The material’s yield strength must not be exceeded.
• Optimise material cost.

Material Properties

The material used in this assignment is PA6+GF15 (Polyamide 6 with 15% Glass Reinforced, UV Stabilised). This material is not present in the standard database of ANSYS workbench; therefore, you need to create it yourself. First, duplicate the properties of polyethene (in General Materials) and then modify it toward PA6+GF15. You should not enter the plastic properties into your ANSYS material model. Instead, use them only to evaluate if the stresses observed in your elastic analysis surpass the material's yield strength. Entering the plastic properties into Ansys will lead to follow-up questions like hardening, etc., which we do not consider here. The properties are as follows:

Approach

The approach to designing the table includes a series of steps in ANSYS Workbench, from creating a geometry without rib supports to optimising the rib placement. Detailed steps include:

• Static Structural Analysis: Start by modelling the initial table geometry without rib supports.
• Material Assignment: Assign and modify the material properties based on PA6+GF15.
• Mesh Generation: Generate and refine the mesh to ensure accurate simulation results.
• Boundary Conditions and Loads: Apply realistic boundary conditions and simulate the loading conditions expected in real-world use.
• Simulation and Analysis: Perform the finite element analysis and post-process the results to evaluate stress, deflection, and overall structural integrity.
• Optimisation: Adjust the rib support to optimise the table’s structural performance and material usage. Note that in the example shown in Fig. 2(a), an isolated region in the middle of the table is strengthened. Think about smarter ways to design the support. Ultimately, the imposed force must be transmitted all the way to the floor, through the table legs. The weakest link in that force transmission can have a major influence on the total deflection of the structure.

You can adjust the layout and connectivity of the rib support and its cross-section. Variable cross sections are also allowed, which you can use to form arches. Ensure the design remains consistent with what would be expected of a consumer product.

Report

Your report should document all steps, calculations, and optimizations. It should also include detailed descriptions of your methodology, assumptions, and findings.

Conclusion

Summarise the effectiveness of the rib support design in enhancing the table’s performance, discuss the balance between structural integrity and aesthetic implications, and consider potential improvements or alternative designs.

Submission

Submit the final report electronically, ensuring all figures and tables are well-documented and referenced.

Appendix A: Design Visualisations