SolverOrAgL

Nonlinear structural dynamics

Friction, contact, vibration. Precisely computed.

OrAgL is the specialised solver for structures whose vibration behaviour depends on friction, contact and amplitude. It computes periodic responses in the frequency domain and transient behaviour in the time domain, including for large, reduced FE models.

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Harmonic BalanceFrictional ContactTime DomainModel ReductionContinuation

Nonlinear structural dynamics

𝐌 \ddot{𝐮} + 𝐃 \dot{𝐮} + 𝐊 𝐮 + 𝐟_{nl} (𝐮, \dot{𝐮}) = 𝐟_{ext} (t)

Schematic, not solver output: harmonic balance of a single-degree-of-freedom oscillator, linear, with frictional contact and with a contact that closes a gap. The stiffening branch overhangs; between the turning points the solution is unstable and the response jumps (arrows).

Capabilities

What OrAgL computes for you.

Focused on the physics that linear models miss: amplitude-dependent stiffness and damping caused by friction and contact, in the frequency and the time domain.

Harmonic balance

Periodic vibration responses computed efficiently in the frequency domain, with a selectable number of harmonics.

*HBM

Nonlinear frequency response

Forced responses across a frequency range, with a linearised reference for direct comparison.

*FRF · *LINEARIZED FRF

Nonlinear modal analysis

Amplitude-dependent natural frequencies and damping as a compact description of system behaviour.

*NMA

Contact & friction

Stick, slip and lift-off at coupling interfaces, with friction coefficient, contact stiffness and preload.

*SURFACE INTERACTION

Model reduction

Reduce large FE models to the relevant degrees of freedom by component mode synthesis (Craig-Bampton).

*ROM

Path continuation

Predictor-corrector continuation with adaptive step size follows the response curve across the entire frequency range.

*CONTINUATION CONTROLS

Time domain

Transient responses to periodic excitation and frequency sweeps, limit cycles and tori, and impacts at rigid contacts.

*NOSTIA · *FSWEEP · *MWF

Cyclic symmetry & mistuning

From a sector model to the full wheel, with nodal diameters and mistuned blades.

*CYCLIC SYMMETRY MODEL · *MISTUNING

Published OrAgL study

From simulation model to measurement.

The peer-reviewed paper “Rig and Engine Validation …” compares nonlinear vibration responses computed with OrAgL with measurements on a rotating test rig and in the engine.

Read the publication

2019 · OrAgL validation · ASME

Rig and Engine Validation of the Nonlinear Forced Response Analysis Performed by the Tool OrAgL

Andreas Hartung, Hans-Peter Hackenberg, Malte Krack, Johann Gross, Torsten Heinze, Lars Panning-von Scheidt · Journal of Engineering for Gas Turbines and Power 141(2), 021019

A published comparison is a starting point. We assess suitability for your geometry, contacts and load cases on a representative model.

Applications

Where OrAgL plays to its strengths.

Wherever local nonlinearities govern the global vibration behaviour. All applications

Turbomachinery

Friction dampers and coupling interfaces of bladed structures, using cyclic symmetry to go from one sector to the full wheel.

Gearboxes

Tooth contact with backlash: lift-off and impacts, in the frequency and the time domain.

Bolted joints

Interfaces that stick, slip or separate, and their influence on stiffness and damping.

Solver + interface

OrAgL computes. ARGUS connects.

The solver handles the numerics. In ARGUS, you edit the input, keep track of runs and keep working with the results, all the way to an animated mode shape.

See the ARGUS workflow

Comparison of several OrAgL runs in ARGUS JSAT

Next step

Is OrAgL right for your problem?

Let’s discuss your model, nonlinearities and the results you need. Together we define a meaningful evaluation case.

Discuss an evaluation