Simulating Mechanical Joining

Management Summary

The Mechanical Joining module is specifically designed for the simulation of mechanical joining processes. It allows for the numerical computation of technologies primarily based on joining-based forming. Therefore, various riveting procedures, such as punch riveting, self-piercing riveting or blind riveting, can be analyzed. It is also possible to simulate the connection formation in diverse joining by shearing and upsetting or clinching technologies with a fixed or an opening die. Furthermore, special effects such as high joining speed (e.g., when setting bolts) or a high momentum (e.g. flow-drill screws) can be taken into account. An analysis of adhesives in the joining zone is also feasible.

Simufact Forming Mechanical Joining contains a library of CAD descriptions of your joining tools and elements and automatically calculates the specific connection parameters. Furthermore, this module offers a specially adjusted simulation set-up.

Take advantage of Simufact Forming for your mechanical joining processes

 

When your joining specialists perform robust and high-performance simulations with experimentally validated results, you are able to:

  • Predict the characteristic of joining parameters (e.g. interlock) with variable joining set-up and behavior under load
  • Evaluate the effect on robustness from deviations in material thickness, material properties, lubrication or press properties
  • Reduce expenses substantially  
    • Fewer experimental tests
    • Fewer cross-section preparations and connection parameter measurements
    • Lower resources (time, staff, presses) for experimental analysis and evaluations
  • Gain significant process expertise
    • Determine the behavior of rivets and materials during joining
    • Increase the stability of the joints and the process
    • Predict failure for tools or rivets

 

 

Simufact - Simulation Flowdrill-Screwing
Flowdrill-Screwing

Modeling Entire Process Chains (Virtual Joining Factory)

Simufact Forming Mechanical Joining is a tool that enables you to simulate an entire virtual process chain. Both the manufacturing of the joining elements themselves, as well as the forming of metal sheets, can be accounted for in the joining simulation, in effect providing a Virtual Joining Factory.

Simulation of self-piercing riveting with Simufact Forming

Application of the module Mechanical Joining

Primary Considerations

All mechanical joining techniques are characterized by a large number of parameters that influence both the quality of the joining results and each other. Experiments alone are not adequate to analyze and quantify these parameters. Through numerical simulation you are offered a range of diverse and unique opportunities for choosing the appropriate technique and its set-up.

Apart from calculating the properties that define quality, it is also possible to visualize material flow during manufacturing, as well as to compute the necessary joining force.

 

Apart from calculating the properties that define quality, it is also possible to visualize material flow during manufacturing, as well as to compute the necessary joining force.

The simulation can indicate tension states that form in the tool during joining, which allows you to estimate tool durability.

It is also possible to examine the influence exerted by high speeds and adhesives as demonstrated by the example of the RIVTAC® process.

Multiple Point Considerations

In the past, two-dimensional calculations sufficed because mechanical joining was primarily a question of axial symmetry. However, for joining requiring several joining points, three-dimensional models must be constructed and calculated. With three-dimensional simulation it is possible to examine the interdependency of joining points, to optimize the sequence of joining, to analyze element distortion and to minimize its effects.

Multi-point consideration of clinching
Shown: flange, die, punch and blank-holder
Simulation: 3D, 180° (quantity: degree of forming)
Result: material flow analysis to review the formation of the joining and the behaviour of the material between joining points

Additionally, the calculation of process-related effects during joining also becomes feasible. For example, differing stiffnesses of the C-frame leads to spring back during the joining process, which can significantly affect the results. The eccentricity of the joining punch or a joining element in relation to the die, or die tilt, influences the formation of the connection, but can be predicted by three-dimensional analysis.

Simulation Videos Mechanical Joining

Punch Bolting
Shown: circular blanks, punching bolt, die, punch, blank-holder
Simulation: 3D, connection of material and bolt
Result: behavior of the material flow for the technological analysis of the joining process

Self-piercing riveting with adhesive
Shown: circular blanks, adhesive between them, die, rivet, punch and blank-holder
Simulation: 2D, materials and rivet, punch, die, blank-holder
Result: material flow analysis to examine the formation of the joining and pocket formation

Modeling Entire Process Chains

Virtual Joining Factory

Simufact Forming Mechanical Joining allows you to work from the results of previous virtual processing steps. This enables you to account for previous changes to the material, such as residual stresses. The option to simulate the whole process chain greatly increases the quality and usefulness of the predictions made about the manufactured results.

App. Virtual Joining Factory
Virtual Joining Factory

3D Model for Load Tests

The Mechanical Joining application module can generate a 3D model of the virtual joining point for different load cases (e.g. lap shear, coach peel and cross tension) with only a few clicks.

Application spectrum for Simufact Forming Mechanical Joining

Procedures

The software covers a broad range of joining procedures, among them:

  • Joining by forming
  • Riveting
  • Punch riveting
  • Self-piercing riveting
  • Blind riveting
  • Clinching, joining by shearing and upsetting
  • Flow-drill screws
  • High-speed joining (applications: Rivtac®, Impact®)
  • Lock bolting
  • Crimping
  • Punch bolting

Materials

  • Steel
  • Nonferrous metals such as titanium, aluminum and copper alloys
  • Depending on the process, plastics and fiber-reinforced plastics are possible

Boundary Conditions

For a realistic simulation of mechanical joining processes, this module takes into account the typical conditions of each specific process:

  • Open and fixed dies
  • Force-dependent, pressure-dependent, or speed-dependent press control
  • Spring coupling or separate control of the blank-holder
  • C-frame springback
  • Eccentricities between punch and die

Optimization targets

Reach your optimization targets with Simufact Forming Mechanical Joining

  1. Choice of appropriate joining technique
  2. Choice of appropriate process variants
  3. Adjustment of joining elements in relation to dies or tools
  4. Punch force, blank holder force
  5. Systematic consideration of variations in material thickness, material strength, lubrication improves robustness
  6. Understanding die loads and die life leads to reductions in down-time
  7. Reduced damage (joining elements, material) during joining process (results in reduction in reworking)
  8. Resistance of connections to static and dynamic loads
  9. Influence of adhesives on the connection formation
  10. Influence of material strain-hardening on the connection formation
  11. Understand influence of C-frame spring-back and eccentricity
  12. Develop of new joining technologies
  13. Sequential arrangement to minimize assembly distortion
  14. Minimize joining point distance
  15. Span the virtual process chain of car body components: manufacturing of the joining elements – to mechanical joining – to the crash simulation

Functional Highlights

Utilize the functional advantages of Simufact Forming Mechanical Joining

  • Precise results from hexahedron and tetrahedron elements
  • Special meshing algorithms and strategies for mechanical joining
  • Highly accurate description of the stress-strain state, the internal stress and the characteristic connection parameters from elasto-plastic and thermo mechanical coupling in the material model
  • Damage criteria based material separation (also in 3D)
  • Efficient software user interface allows model definition familiar to production engineers
  • Accurate modeling of the tribology through innovative friction models
  • Numerically robust description of the contact through the use of the Segment-to-Segment method
  • Special simulation configurations for friction, material separation and contact enable realistic simulation results
  • Easy to define complex processes with no limit to the number of tools, the number of degrees of movement and boundary conditions
  • High efficiency and accuracy of results from 2D axial symmetry
  • Fast 3D modeling and simulation
  • Automatic interlinking of all process steps including the 2D to 3D transition

 

 

Comparison of Cross-Sections

A comparison of cross-sections, from experiments and simulations, show a precise match between the virtual prediction and reality.

This striking illustration was calculated with just a few iterations. Afterwards, numerical variants can be calculated with the same high-quality simulation without further comparison to a real-life experiment.

Cross-section of a punch rivet: reality and simulation
Cross-section of a punch rivet: reality and simulation

References Mechanical Joining

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A short case study with Eckold provides some insights:

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A large number of users, leading automotive OEMs among them, trust the simulation technology of Simufact. Project partners and customers of Simufact Forming Mechanical Joining include among others:

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