Release Notes 2020 R2

Virtual ICE Development - Durability and NVH

An Update to the AVL Simulation Solution for IC Engine Development

At AVL we continually update and improve our products and services, in order to address the evolving needs of our customers and the changing automotive landscape. Below you will find some of the highlights of the latest release in our solution area ICE Durability and NVH.

Lubricated Sliding Contact Analysis

General FE Node Distribution in Contact Area of Bearings and Pistons

For the elastohydrodynamic radial slider bearing and piston joints of AVL EXCITE™ Power Unit, it is now possible to have a general FE mesh with an arbitrary node distribution for the surface contact. This is especially helpful for non-rectangular contact geometries as is usually the case for pistons but for example, also for camshaft bearings.

This innovative tool automatically detects the outer boundaries of the FE geometry and sets the boundary condition accordingly. The used FE mesh can also feature holes like a bore or groove. For an easy and fast definition of the boundary condition for these inner holes, their geometry is automatically outputted to the 'simulation.out' file. This means it can directly be used for setting up the boundary condition.

You can now directly couple the elements used that are linear tetrahedron or linear hexahedron. In case of second order tetrahedron or hexahedron elements, you should use a membrane, consisting of linear triangular or linear quad elements, and a tied constraint.

Figure 1: Irregular FE mesh at surface contact of a piston with different geometry on thrust and anti-thrust side

Piston Ring Analysis – Significantly Improved Solver Performance

The core computational kernel of EXCITE™ Piston&Rings has been restructured and considerably enhanced with respect to performance in general as well as stability regarding simulation models reacting sensitively on solver settings.

Depending on the piston ring model type and the dynamics calculation approach used, the calculation time is up to twice as fast compared to the previous version.

Figure 2: Performance improvement of a 3D piston ring analysis

Piston Ring Wear Analysis

The former script-based piston ring flank wear evaluation is now an integrated part of EXCITE™ Piston&Rings. This provides more efficient accumulated wear load, wear depth and final flank profile results. For easy access all 2D piston ring wear results – including the one for the running face – are now part of the result tree.

Figure 3: Top ring running face wear load of a truck diesel engine after 10 hours

Piston Ring Dynamics and Tribology

A new feature in EXCITE™ Piston&Rings enables model gas to flow through the holes in the head of the piston from the combustion chamber to the grooves of the first ring.

Figure 4: Interring pressures with gas flow through piston holes

We have also implemented an optional definition of a 2D (axial and circumferential) liner surface temperature profile to allow for a more accurate calculation of the oil viscosity on the liner surface and the oil evaporation mass flow. For that purpose, the 3D ring LOC results are now available via a new introduced result creation task, including 2D fringe diagrams of oil evaporation related results.

Figure 5: Liner temperature distribution in axial and circumferential direction


NVH Analysis of IC Engines and Power Units

Tooth Deflection for Inner Gear Wheels

Until now, tooth deflections, such as contact flattening and tooth bending/tipping were only supported by AVL EXCITE™ Power Unit for external toothed gears with the advanced gear model.
For internal toothed ring gears you had to specify the meshing stiffness.

With the new version, the computation of tooth deflections is now possible for internal (ring) gears as well. It also allows you to consider the meshing stiffness contributions due to flank contact (Hertz-Peterson) as well as tooth bending (Weber/Banaschek).

Regarding the deformation of the ring (annulus), we have implemented the method proposed by Chen/Shao. With new options for the ring gears, it is now possible to consider all the relevant deformation contributions coming from the flank contact, the tooth bending and the ring bending in order to achieve more realistic results for the predicted mesh stiffness.

Figure 6: Meshing stiffness depending on the position of the planet relative to the support points of the ring

Improved Contact Approach for Rolling Element Bearings

We have implemented an improved contact approach for rolling element bearings for cylindrical and tapered rolling elements. As an extension of the existing classical Palmgren/Lundberg/ Führmann power-law, which is based on the full contact length of the rolling element, now the effective contact length can be defined depending on the penetration depth. With this approach you can consider the effect of reduced bearing stiffness due to rolling element crowning more realistically.

Below figure outlines how the value of the effective contact length varied over the penetration depth (positive depth indicates contact) and consequently influences the computation of the contact stiffness between rings and rolling elements.

Figure 7: Contact length changing with penetration depth for different rolling elements

Load Data Extension for e-Motor NVH and Multipurpose Use

You now have extended import possibilities in the ‘Load Data’ dialog including the option to replicate load items. We provide two loops for data import to generate multiple load items from a specified base item. With this, it is possible to import data, for example, for multiple operation points and a set of nodes. You can also replicate the definition of body loads analogously. This automates the workflow to import stator tooth forces for NVH analysis of electric motors for different operation points.

The AVL E-Motor tool completes this feature with automated electromagnetic analysis for stator tooth forces at arbitrary operation points from CAD or geometry templates for permanent-magnet synchronous machines. It thus provides the necessary electro-magnetic input for NVH analysis of electrified powertrains with the EXCITE™ Power Unit. You can also import force/torque data from third party tools in an appropriate file structure and format.

Sound Radiation Calculation – Reduced Memory Demand

The new feature - use of Predefined FE Nodes - of EXCITE™ Acoustics has the benefit of decreasing the memory demand, the simulation time, and the hard disc space. To which extend dependents on the main dimensions of the structural mesh, the size of the final acoustic mesh, and the frequency range of interest.

Figure 8: Gearbox example with and without predefined FE Nodes


Concept Analysis

Torsional Vibration Damper - Temperature Calculation

The COMPOSE™ App for TVD temperature calculations, based on an EXCITE™ Designer model, has been extended to cover also double-ring dampers. In case a double-ring damper is defined within EXCITE™ Designer crankshaft model, it will be automatically recognized by the App, which will show a second tab containing the similar input data and results tree.

Figure 9: Extension for double-ring TVD


Link to MATLAB® Interface

We have introduced a new “Link to MATLAB®“ interface for co-simulations with MATLAB® Simulink models, using a unified user interface like the FMU interface. Here, the user has more flexibility in defining input and output ports, as you can select each desired quantity individually. Additionally, we provide a template Simulink model as a starting point for creating the Simulink model for the co-simulation.

The following components are available:
• “Link to MATLAB® Joint C-C” component to connect two bodies
• “Link to MATLAB® Load (Force)” component to apply an external force on one body


Figure 10: Link to MATLAB®

New Condensation App (COMPOSE™)

A new, user-friendly condensation App for defining and running a FE condensation analysis is part of the latest release. Overall, the App enables you to specify the FE solver, version and solver options, plus options for the substructure generation, the retained degrees-of-freedom and the number of retained modes. Furthermore, the APP also allows the generation of a full or partial recovery matrix as well as modal stress or strain matrix.

If the user has direct access to the FE solver installation, the job will be submitted by the App. If not, you can operate all the corresponding input files manually. FE solvers are supported: Abaqus, Ansys (MSC|NX Nastran, OptiStruct and PERMAS will be added in subsequent releases).

FE Analysis: Linear Static Stress Analysis Task for PERMAS

The FE Analysis Task - Linear Static Stress Analysis - is now fully functional for the FE solver PERMAS. The user can either generate PERMAS input files containing nodal forces or prescribed nodal displacements to perform a stress analysis. Additionally, you can now apply pressure and inertia loads on the original FE model.