Lecture 7: Shell Elements

What is a key requirement for solving thin components in FEA?

At least two elements must be across the thickness.

What type of element is used when one dimension is significantly smaller than the other two?

Shell elements.

What is a Plane Stress Element used for?

Modeling parts where the dimensions are significantly larger in one direction, with normal and shear stress perpendicular to the plane being zero.

What is a Plane Strain Element?

An element used for thick models where the strain in the direction perpendicular to the plane is assumed to be zero.

What is the purpose of Axisymmetric Elements?

To model axially symmetric structures such as storage tanks and nozzles.

What are the limitations of external loads in shell element analysis?

Cannot split the surface or apply certain types of loads like Remote load or Distributed Load.

What is the difference between First Order and Second Order Shell Elements?

First Order Shell Elements use linear triangular shell elements while Second Order Shell Elements use parabolic triangular shell elements.

How many degrees of freedom exist for both First and Second Order shell elements?

Six degrees of freedom.

What is the significance of the Aspect Ratio in shell elements?

An aspect ratio greater than 10 may indicate that a shell element is appropriate for modeling.

What is the recommended modeling approach for bending problems in shell analysis?

Use a Thin Shell model when bending is predominant and shear is negligible.

What happens if the aspect ratio is less than 10 in shell element analysis?

The solid element is generally recommended for modeling.

What is the function of the mid-surface in SolidWorks for shell modeling?

It allows solid models to be converted to shell models by creating a mid-surface between the inner and outer surfaces.

What is a key characteristic of shell elements compared to solid elements?

Shell elements are more efficient for modeling thin-walled structures with uniform thickness.

What is the main disadvantage of using shell elements for detailed stress analysis?

They cannot provide detailed stress analysis required to investigate contact between parts in assembly FEA.

What are the three ways to create a shell model in SolidWorks Simulation?

Using Sheet Metal tools, defining shell by selected faces, or inserting a mid-surface.

What should be considered when deciding between solid and shell models?

If unsure which method to use, compare results from both models if resources allow.

What is the significance of nodal displacements in 3D elements?

They include three translations and three rotations in the x, y, and z directions.

What is the general recommendation for thick shell modeling?

Thick shell modeling is recommended for more accurate results, even for thin shell bending problems.

What is the behavior of thin shells in terms of bending and shear?

Thin shells behave like membrane structures where bending is predominant and shear effects are negligible.

What is the role of fixtures in shell element analysis?

Fixtures are similar to other types of analysis but have restrictions on surface splitting and certain load applications.

What is the outcome of using a shell element for a structure with an aspect ratio greater than 10?

It may be an appropriate option for modeling.

What is a common example of an axially symmetric model?

Storage tanks and nozzles.

What is the effect of using a solid model instead of a shell model?

Solid models provide detailed analysis but may be less efficient for thin-walled structures.