Shrink Fit / Press Fit Analysis
Shrink Fit / Press Fit: Theoretical Foundations
What is Press-fit?
Professor, what is press-fit analysis?
Press-fit (interference fit) is a fastening method where a negative clearance (interference amount) is provided between a shaft and a hole. During assembly, the shaft is pressed into the hole, or the hole is heated to expand before inserting the shaft.
Setting Interference Amount in FEM
Two approaches:
1. Geometrically Overlapping Mesh — Arrange the shaft and hole meshes to overlap by the interference amount. The contact resolves the interference.
2. Initial Clearance Adjustment — Use *CLEARANCE ADJUSTMENT in the contact definition to numerically specify the interference amount.
Can it calculate even with overlapping meshes?
The penalty method in contact "pushes back" the interference, generating physically correct contact pressure. Abaqus's *SURFACE INTERACTION + OVERCLOSURE=ADJUST is convenient.
Summary
Key points:
- Set interference amount in contact definition — Geometric overlap or CLEARANCE ADJUSTMENT
- Contact pressure = Compare with Lamé's thick-walled cylinder formula — Verify with $p = \delta E^* / D$
- Bearing press-fit, gear hub-shaft, camshaft — Main applications
Press-fit in the Steam Engine Era
The industrial origin of press-fit/shrink-fit dates back to steam locomotives in the 1820s. In George Stephenson's Rocket (1829), a method of heating and expanding iron wheels to fit them onto axles was adopted. The precision at that time was about ±0.1mm, which is considered one of the first industrial design cases theoretically supported by the elastic solution for thick-walled cylinders (Lamé solution) established by Lamé (1852).
Computational Methods for Shrink Fit / Press Fit
FEM Settings for Press-fit
```
*CONTACT PAIR
shaft_outer, hub_inner
*SURFACE BEHAVIOR, PENALTY
*SURFACE INTERACTION, NAME=interference
*CLEARANCE, OVERCLOSURE=ADJUST, VALUE=-0.05 $ Interference amount 0.05mm
```
Introducing interference gradually (starting from zero interference → gradually reaching target interference) improves convergence.
Summary
Lamé Solution and FEM Correction
The stress distribution of a press-fit can be calculated quite accurately with Lamé's (1852) analytical solution, but FEM correction becomes necessary at hole edges or steps. ABAQUS adopts an algorithm that specifies the interference amount with the INTERFERENCE FIT option, treating it as uniform penetration in the first increment before converging the contact forces. This allows reproducing the stress concentration factor for a shaft-hub joint with 100μm interference within ±5% of measured values.
Shrink Fit / Press Fit in Practice
Press-fit in Practice
Used for bearing press-fit, gear hub-shaft fastening, flywheel press-fit.
Practical Checklist
Shinkansen Axle Press-fit Analysis
Since the 2010s, JR East has utilized ABAQUS Standard for fatigue crack propagation analysis in the axle-wheel press-fit sections of Shinkansen bogies. Starting from the contact pressure distribution equivalent to 0.3mm interference, they calculate the stress intensity factor KI using XFEM under repeated running loads, providing a numerical basis for reviewing conventional ultrasonic flaw detection inspection intervals (running distance of 600,000 km). The analysis results were published as a joint study with the Railway Technical Research Institute.
Shrink Fit / Press Fit: Software & Solver Comparison
Tools for Press-fit
Selection Guide
History of Dedicated Interference Fit Solvers
Dedicated press-fit analysis features were first commercially organized in MSC Nastran's SOL 601 (nonlinear static analysis) as V2004. The ability to simply specify the interference amount in the CONTACT DIRECTIVE and automatically calculate prestress was well-received in practice. Around 2012, Simulia began providing an INTERFERENCE FIT wizard in the ABAQUS/CAE GUI, establishing a workflow to directly input interference amounts from drawings.
Advanced Technology
Advanced Research in Press-fit
Advanced Press-fit Phenomena in High-speed Machinery
In high-speed turbomachinery, creep relaxation of the shrink-fit interference can significantly reduce holding force at elevated temperatures. Modern aircraft engine designs incorporate residual stress mapping using ABAQUS to account for both elastic and plastic deformation during the shrink-fit process, with post-interference simulations validating holding force retention across the operational temperature envelope of -55°C to +120°C.