# Practical Modelling of Joints & Connections

## Course Overview

Most structures involve some form of jointing or connection. Traditional fabricated structures have used many thousands of bolts and rivets to connect components together in a continuous manner, in the case of ships and aircraft the total can run into millions.

Even today many structures rely on this type of technology – for example, the use of spot welds in a modern road vehicle. Significant discrete load paths are formed by lugs and pins, clips or similar connectors in many structures across a wide range of industries. Alternative forms of connection are welds joints and bonded joints. These may well exist as the sole means of load transfer or be supplemented by mechanical connections such as bolts or rivets.

The engineer is faced with an often difficult decision when attempting to simulate such connections and joints within a Finite Element Analysis (FEA). In many cases, the details of each individual connection can be ignored if an overall stiffness or strength assessment is to be made and the connection is assumed reasonably continuous. However, there may be doubts about the local flexibility and load paths developed with this assumption. It may be that the assessment of the local behavior of the connector is essential to the safety case. This would certainly be the case with main attachment fittings for example. In some cases, the interaction between the connectors and the surrounding structure is critical, as in the case of pre-loaded bolts and inter-rivet buckling.

Modeling of weld features to get a reasonable estimate of stress concentrations at the weld toe can be problematic; do we model with a fine detailed 3D model, or use a ‘hot spot’ type of approach?

The objective of this course is to review the various connection and joint technologies in use, give an overview of the physics involved and show how to successfully implement practical solutions using Finite Element Analysis.

### The course is completely code independent. No software is required.

Each topic in the class is treated as a building block and is presented using an overview of the physics and theory involved. The math is kept simple and the emphasis is on practical examples from real life to illustrate the topic. The mapping to Finite Element analysis techniques is shown with numerous workshops.

## Course Contents

### Bolts and Rivets

Overview

• Review of practical designs and applications

Finite Element Modeling Methods

• Bolt and Rivet Groups
• Rigid and flexible spider elements used in bolt and rivet loading distribution

• Single bolts/rivets

•  Overall Stiffness and load path assumptions
•  Influence of clamped structure
•  Different approaches between rivets and bolts
•  Line element representation with spider
•  Shell element representation with spider
•  Solid element representation with spider (nugget or bolt section)

• Inter-rivet buckling and other instabilities

• Internal forces directly applied
•  ‘freezing’ of elements to induce pre-strain

• Usage with linear and nonlinear contact surfaces
•  Overview of application and methodology
•  Types of Linear Contact
•  Nonlinear Contact Issues
•  Interference Fit

• Detailed modeling of bolts and rivets in linear and nonlinear analysis
•  Full 3D simulation
•  Axisymmetric Idealization
•  Nonlinear Effects
•  Frictional effects

• Fatigue and Fracture Mechanics of bolts and rivets

### Lugs

Overview

• Review of practical designs and applications
• Traditional lug failure modes and calculations
• Bearing Distribution assumptions

FE Modeling Methods

• 2D Shell modeling
• 3D Solid modeling
• Linear and Nonlinear Contact methods
• Interference fits
• Fatigue and Fracture Mechanics

### Welds

Overview

• Review of practical designs and applications
• Traditional welding classifications and calculations

FE Modeling Methods

• Weld simulation with 2D shell models
• Weld simulation with 3D solid models
• Weld Toe stress concentrations
• Hot Spot methods

### Bonded Joints

Overview

• Review of practical designs and applications

FE Modeling Methods

• 2D thin shell models
• 2D plane strain methods
• 3D solid models
• Cohesive Zone Failure Modeling
• VCCT Failure Modeling

## PSE Competencies addressed by this training course

 ID Competence Statement BMPSev2 Select suitable idealisations for welded, bonded, riveted and bolted joints in fabricated plate/shell structures.