Finite Element Analysis (FEA) of pipe intersections in ABAQUS requires careful consideration of element types. Specifically, both hexahedral (hex) and shell elements offer distinct advantages and limitations. Therefore, this study compares the two approaches to guide engineers in selecting the most suitable element type for accurate and efficient simulations.

Study Overview

For pipe intersection analysis:

• Solid (Hex) elements are preferred for geometrically non-linear analyses, accommodating large displacements, rotations, and shearing.

• They include initial stress stiffness and surface load stiffness, allowing accurate modeling under pressure loads.

• When finite strains are considered, the formulation uses true stress per unit area and the integrated rate of deformation as the strain measure.

Boundary Conditions:

• Material: AISI 4130

• Force: 1000 N applied

• Constraints: Clamps at both open ends to lock DOFs

Hexahedral Elements (C3D8R)

Definition:

• C – Continuum

• 3D – Three-dimensional

• 8 – Nodes per element

• R – Reduced Integration

Global element type selection in Mechanical scenario creation app on 3DExperience Platform. (Figure 1)

 Representation of the hex mesh at the junction of intersection of the pipes. (Figure 2)

Representation of the mesh on the face of the pipe (Figure 3)

Sweep mesh specs (Figure 4)

Results:

• Maximum displacement: 5.24 mm

Displacement with C3D8R elements  (Figure 5)

• Von Mises stress distribution shown in figures

Von mises stress with C3D8R elements (Figure 6)

Advantages:

• Moreover, hex elements provide an accurate representation of complex 3D geometry; in particular, they excel at modeling pipe intersections.
• Additionally, they are less prone to shear locking, which enhances numerical stability.
• Furthermore, fewer elements are needed to achieve converged solutions, improving computational efficiency.

Disadvantages:

• However, hex elements are more challenging to mesh, especially for complex geometries.
• In addition, they incur a higher computational cost due to the greater number of nodes per element.

Linear Shell Elements (S4R)

Definition:

• S – Shell

• 4 – Nodes per element

• R – Reduced Integration

 Global element type selection in Mechanical scenario creation app on 3DExperience Platform (Figure 7)

Representation of the shell mesh on the face of the pipe. (Figure 8)

Representation of the hex mesh at the junction of the intersection of the pipes. (Figure 9)

Results:

• Maximum displacement: 4.97 mm

Displacement with S4R elements (Figure 10)

• Von Mises stress distribution shown in figures

Von Mises stress with S4R elements (Figure 11)

Advantages:

• Firstly, shell elements are easier to mesh, even for complex geometries.

• Moreover, they are more efficient for simpler analyses, reducing setup time.

Disadvantages:

• However, shell elements are less accurate at complex intersections compared to hex elements.

• In addition, they are more prone to shear locking, which can affect results.

• Furthermore, achieving comparable accuracy may require additional elements, such as wedges at junctions.

Non-Linear Shell Elements (S8R)

Definition:

• S – Shell

• 8 – Nodes per element

• R – Reduced Integration

Shows the global element type selection in the Mechanical Scenario Creation app on the 3DEXPERIENCE Platform.(Figure 12)

Illustrates the shell mesh on the face of the pipe. (Figure 13)

Depicts the hex mesh at the junction of the pipe intersection.(Figure 14)

Results:

• Maximum displacement: 8.41 mm

Displacement with S8R elements (Figure 15)

• Von Mises stress distribution shown in figures

Von Mises stress with S8R elements (Figure 16)

And the maximum displacement: 5.25mm

S4R

It can be noted that the maximum Von Mises Stress for S4R ( linear shell elements) were

and the maximum displacement: 4.97mm

It can be noted that the maximum Von Mises Stress for S8R (non-linear shell elements) were

and the maximum displacement: 8.24mm 

Conclusion

• Geometry Complexity: For simple intersections, shell elements are sufficient; for complex curved intersections or branches, hex elements provide better accuracy.

• Type of Analysis: Linear static analysis can use shell elements; non-linear analyses with large deformations or contact benefit from hex elements.

• Meshing Experience: Shell elements are easier for beginners; with practice, hex elements can be efficiently meshed.

Selecting the right element type balances accuracy, computational cost, and ease of meshing. Understanding the strengths and limitations of each element ensures reliable results for pipe intersection simulations in ABAQUS.

• Author
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Debaditya Chakraborty

Industry Process Consultant at Dassault Systèmes

Industry Process Consultant at Dassault Systèmes. Debaditya is passionate about innovation in multi-body dynamics, CAD, and FEA, specializing in multi-link mechanism design using data-driven methods. He has experience in Metal Additive Manufacturing simulations, ship structural analysis, and FEA process automation.

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