Structural Mechanics Module

Software for Performing Structural Mechanics Analyses

Structural Mechanics Module

Eigenfrequency analysis of a conrod showing the torsion angle along the conrod at the lowest eigenfrequency.

Static, Transient, and Frequency-Domain Structural Analysis

The Structural Mechanics Module is dedicated to the analysis of mechanical structures that are subject to static or dynamic loads. You can use this software for a wide range of analysis types, including stationary, transient, eigenmode/modal, parametric, quasi-static, frequency-response, buckling, and prestressed analyses.

Add-on Products Augment and Supplement Your Structural Analyses

The Structural Mechanics Module provides user interfaces for analyses in 2D, 2D axisymmetry, and 3D coordinate systems for solids, shells (3D), plates (2D), trusses (2D, 3D), membranes (2D axisymmetry, 3D), and beams (2D, 3D). These allow for large deformation analysis with geometrical nonlinearity, mechanical contact, thermal strain, piezoelectric materials, and fluid-structure interaction (FSI). If you are looking to perform nonlinear materials analysis, there are two add-on products available to you – the Nonlinear Structural Materials Module and the Geomechanics Module. For fatigue life evaluation, you can leverage the add-on Fatigue Module, while if you are looking to model flexible and rigid body dynamics, the add-on Multibody Dynamics Module is for you. The Structural Mechanics Module also works in tandem with COMSOL Multiphysics and the other application-specific modules to couple structural analysis with a wide range of multiphysics phenomena, including the interaction of mechanical structures with electromagnetic fields, fluid flow, and chemical reactions.


Additional images:

  • An eigenfrequency analysis of an impeller is achieved through performing the simulation on just one of the blades and using in-built periodic boundary conditions. An eigenfrequency analysis of an impeller is achieved through performing the simulation on just one of the blades and using in-built periodic boundary conditions.
  • Transient structural analysis of a damper made from a viscoelastic material. Transient structural analysis of a damper made from a viscoelastic material.
  • Prestressed bolts introduces tensile forces and thus stresses in a flange. Prestressed bolts introduces tensile forces and thus stresses in a flange.
  • FSI - A solar panel subjected to a wind load demonstrates a coupled fluid and structural analysis. FSI - A solar panel subjected to a wind load demonstrates a coupled fluid and structural analysis.
  • Contact between the ball bearings, cage, and large deformation on the rubber seal of a constant velocity (CV) joint. Model courtesy of Fabio Gatelli, Metelli S.p.A., Cologne, Italy. Contact between the ball bearings, cage, and large deformation on the rubber seal of a constant velocity (CV) joint. Model courtesy of Fabio Gatelli, Metelli S.p.A., Cologne, Italy.
  • Study of a rotating blade shows how the combined effect from stress stiffening and spin softening affects the fundamental eigenfrequency Study of a rotating blade shows how the combined effect from stress stiffening and spin softening affects the fundamental eigenfrequency

Material Models

The constitutive models of the Structural Mechanics Module include linear elastic and viscoelastic material models, as well as orthotropic materials and materials with damping. The included set of material models can be expanded by adding the Nonlinear Structural Materials Module and Geomechanics Module, which allow for the analysis of large strain plastic deformation, hyperelastic materials, plasticity, creep, viscoplasticity, rocks, concrete, and soil. There is great flexibility in entering user-defined materials, which is where the equation-friendly user interfaces of COMSOL software come into play. For a large number of cases, the traditional user-subroutine approach can be replaced by just entering the constitutive equations directly into the user interface as mathematical expressions in field variables, stress and strain invariants, and derived quantities. For example, Young's modulus does not have to be a constant, but can be a function of any field variable and its derivatives. Material properties can vary in space or time, or be described using complex valued expressions.

Loads, Constraints, and Specialized High-Performance Modeling Tools

A great variety of loads and constraints are available to you. These include total force, pressure loads, follower loads, springs and dampers, added mass, prescribed displacement, velocity, and acceleration. For modeling thin elastic parts, you may use the special Thin Elastic Layer interface. Furthermore, specialized Rigid Domain and Rigid Boundary conditions are available for mixing rigid and flexible structures with more capabilities offered by the Multibody Dynamics Module. When modeling a smaller structure embedded in, or situated on top of, a large substrate of elastic material, a designated Infinite Element domain property is available to you. This simulates the absorption of stress that decays slowly, and allows for a truncated smaller domain to be simulated without loss of accuracy, while allowing for highly efficient simulations of the larger structure.

Solid Mechanics

The Solid Mechanics interfaces of the Structural Mechanics Module define the quantities and features for stress analysis and general linear and nonlinear solid mechanics, solving for the displacements. Linear Elastic Material is the default material model. Other material models are hyperelasticity (requires the Nonlinear Structural Materials Module) and linear viscoelastic material models. In addition, the elastic material model can be extended with thermal expansion, damping, and initial stress and strain features. General inelastic strains can easily be defined by entering them as additional initial strain contributions and can even be functions of any other physics fields spanning electromagnetics to fluid flow. The description of elastic materials in the module includes isotropic, orthotropic, and fully anisotropic materials. Each material coefficient can be described by a constant, variables, look-up tables, and composite and nonlinear expressions that can vary in space and time. COMSOL Multiphysics has the ability to interpret any and all expressions, which allows you to stay within the COMSOL Desktop® environment for advanced modeling tasks, without resorting to programming.

Large Deformations and Mechanical Contact

The Structural Mechanics Module enables you to model large deformation with geometric nonlinearity and follower loads. Loads can be distributed and may also depend on other physics, such as electromagnetic or fluid flow forces. Mechanical contact is of course available and is multiphysics enabled. You can, for example, allow for heat flux (requires the Heat Transfer Module) or electric currents (requires the AC/DC Module) across boundaries that are in contact, and make use of contact stresses to simulate the extent of current or heat transfer.

Shells, Plates, and Membranes

Shells, based on the Mindlin-Reissner formulation, are available for the structural analysis of thin-walled structures, where transverse shear deformations are accounted for so that you can simulate thick shells as well. It is also possible to prescribe an offset in the direction normal to a selected surface. The Shell interface also includes other features such as damping, thermal expansion, and initial stresses and strains. The preset studies available are the same as for the Solid Mechanics interface. Similar to the Shell interface, the Plate interface acts in a single plane, but usually only with out-of-plane loads.

The Membrane interface models curved plane stress elements in 3D, which have the possibility to deform both in the in-plane and out-of-plane directions. The difference between a shell and a membrane is that the membrane does not have any bending stiffness. This interface is suited for modeling structures like thin films and fabric.

Vibrations, Acoustics, and Elastic Waves

A range of capabilities are available for vibration analysis with optional couplings to acoustics together with the Acoustics Module. When combining the Structural Mechanics Module and the Acoustics Module, you are granted access to a dedicated tool for acoustic-shell interactions. The Acoustics Module has additional physics interfaces for solid-acoustic and piezo-acoustic interactions. For elastic waves propagating in a material, the Structural Mechanics Module offers low-reflecting boundaries and perfectly matched layers where outgoing elastic waves are simulated as being absorbed. This functionality makes it easy to model waves propagating outwards from a vibrating structure in relatively large or infinite media.

Fatigue Evaluation

By adding the Fatigue Module to your structural mechanics analyses, you can perform structural fatigue life computations. Both high-cycle and low-cycle fatigue methods, and cumulative damage analysis are available. The Fatigue Module is tightly integrated with the Structural Mechanics Module and you remain in the COMSOL Desktop® environment for the structural mechanics and for fatigue computations. The Fatigue Module can be used together with the Solid Mechanics, Shell, Plate, and Multibody Dynamics interfaces as well as for the physics interfaces that simulate thermal stresses, joule heating together with thermal expansion, and piezoelectric devices.

Beams and Trusses

Beam elements in the Structural Mechanics Module are intended for the analysis of slender structures (beams) that can be fully described by cross section properties, such as areas and moments of inertia. They simulate frame structures, both planar and in 3D, and can be coupled with other element types, such as for analyzing reinforcements of solid and shell structures. The Beam interface includes a library for rectangular, box, circular, pipe, H-profile, U-profile, and T-profile beam sections. Additional features include damping, thermal expansion, and initial stresses and strains. A separate 2D physics interface, called Beam Cross Sections, can be used to evaluate cross section properties for arbitrary 2D cross sections to use as inputs in beam analyses.

The Truss interface can be used to model slender structures that can only sustain axial forces. Trusses allow specification of small strains as well as large deformation strains. Examples of truss structures are truss works with straight edges and cables exposed to gravity forces (sagging cables). Additional features include damping, thermal expansion, and initial stresses and strains.

Thermal Stress

While the Structural Mechanics Module works together with COMSOL Multiphysics, and can be integrated with other add-on modules to model many different multiphysics applications, it does include a number of tailor-made multiphysics interfaces. For instance, the Thermal Stress interface is similar to the Solid Mechanics interface with the addition of a thermal linear elastic material model. It can be used in combination with various Heat Transfer interfaces to couple the temperature field to a structure’s (material) expansion. A special Joule Heating and Thermal Expansion multiphysics interface combines Thermal Stress with Joule Heating and describes the conduction of electric current in a structure, the subsequent electric heating caused by the ohmic losses in the structure, and the thermal stresses induced by the temperature field.

Additional Mechanical Modeling Capabilities in Other Modules

The MEMS Module provides dedicated tools for structural simulations specific to micromechanical systems. It offers physics interfaces for piezoresistivity, electromechanical deflection, thermoelastic vibration, and more advanced modeling tools for analyzing piezoelectric devices. From a mechanical analysis perspective, the Acoustics Module covers structural vibration in combination with acoustic pressure waves and elastic and poroelastic wave propagation. The Subsurface Flow Module enhances the Solid Mechanics interfaces with poroelasticity in combination with porous media flow.

CAD and Optimization

The CAD Import Module provides the ability to import a range of industry-standard CAD formats, including geometry clean-up and repair operations for preparing CAD models for meshing and analysis. The CAD Import Module also provides the well-known Parasolid® geometry kernel for more advanced solid operations than what is supported with the COMSOL native kernel. For mechanical simulation of electronics structures, the ECAD Import Module offers electronic layout import. When analyzing a mechanical part or assembly, it is vital to keep the CAD-native parametric model so that parameter studies and optimization can be performed without having to reconstruct model parameters. This is made possible by using the LiveLink products for CAD that are available for several leading CAD systems: SOLIDWORKS®, s, Inventor®, AutoCAD®, PTC® Creo® Parametric, PTC® Pro/ENGINEER®, and Solid Edge®. These products offer simultaneous updates of geometry parameters in the CAD system and COMSOL, and allow for parametric sweeps and optimization over several different modeling parameters. By including the Optimization Module, automated optimization is possible for geometric dimensions, boundary loads, or material properties.

Piezoelectric Devices

The Piezoelectric Devices interface combines COMSOL's Solid Mechanics and Electrostatics modeling capabilities into a fully coupled tool for modeling piezoelectric materials. The piezoelectric coupling can be in stress-charge or strain-charge form with fully coupled frequency-sweep, eigenmode, and transient computations. All solid mechanics and electrostatics functionality is accessible through this physics interface, to model the surrounding linear elastic solids or air domains as well as dielectric layers, for example.

Fluid-Structure Interaction (FSI)

The Fluid-Structure Interaction (FSI) multiphysics interface combines fluid flow with solid mechanics to capture the interaction between the fluid and the solid structure. Solid Mechanics and Laminar Flow interfaces model the solid and the fluid, respectively. The FSI couplings appear on the boundaries between the fluid and the solid, and can include both fluid pressure and viscous forces, as well as momentum transfer from the solid to the fluid – bidirectional FSI. The method used for FSI is known as an arbitrary Lagrangian-Eulerian (ALE).

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