Radioss

Altair Radioss is a multidisciplinary finite element solver developed by Altair Engineering.^[1] It includes implicit and explicit time integration schemes for the solution of engineering problems, from linear statics and linear dynamics to non-linear transient dynamics and mechanical systems. The multidisciplinary solver has its main strengths in durability, NVH, crash, safety, manufacturability, and fluid-structure interaction.

Radioss/OpenRadioss
Developers	Altair Engineering, open source
Stable release	2025.1 (Radioss) stable build 20250925 (OpenRadioss) / 2025 (Radioss) 25 september 2025 (stable version of OpenRadios)
Written in	Fortran
Operating system	Linux and Microsoft Windows
Type	FEM software
License	proprietary (Altair Radioss), GNU AGPL (OpenRadioss)
Website	www.altair.com/radioss/ www.openradioss.org

Since the 2021 release, Radioss has supported input in the LS-DYNA input format as well as the Radioss 'Block' Format ^[2]

OpenRadioss, an open-source version of Radioss under the GNU AGPL license. OpenRadioss shares the capabilities, input and output formats of Altair Radioss. OpenRadioss was released on September the 8th 2022.^[3] OpenRadioss uses an external library that is partly provided in binary form. This external library contains open-source software like lapack and C++ Mathematical Expression Toolkit Library. But also free software like md5, zlib, and Altair's library for their h3d extension.^[4][5]

History

Radioss originated from the 3D FEA program DYNA3D. DYNA3D was originally developed by Dr. John O. Hallquist at Lawrence Livermore National Laboratory (LLNL) in 1976. DYNA3D was publicly released upon a request of France.^[6] After DYNA3D was released, the ESI Group developed Pam-Crash. Some time later, Radioss splitted from Pam-Crash.^[7] This means that the LS-DYNA, Pam-Crash and Radioss all originate from the same base code. Abaqus, Pronto-3D, MSC DYNA, and DYTRAN also originate from DYNA3D.^[8]

In september 2022, Altair made the decision to release Radioss also under the open-source GNU AGPL license.^[9] This means that Radioss is available both with a commercial license and an open-source license. OpenRadioss allows academia to implement new features in OpenRadioss which later can be ported to Radioss. This means that developments in academia go quicker to a commercial FEA program. Altair also has appointed a director of the OpenRadioss community, Marian Bulla. Besides this, OpenRadioss also has a steering committee with 13 members that include people from industry and academia.^[10]

Disciplines

• Linear static analysis
• Non-linear explicit dynamic analysis
• Non-linear implicit quasi-static analysis
• Normal modes analysis for real and complex eigenvalues
• Linear buckling analysis
• Frequency response analysis
• Random response analysis
• Linear transient response analysis
• Linear coupled fluid-structure (acoustic) analysis
• Linear steady-state heat transfer analysis coupled with static analysis
• Explicit Arbitrary Eulerian-Lagrangian (ALE) formulation
• Explicit Computational Fluid Dynamics (CFD)
• Smoothed-particle hydrodynamics (SPH)
• One-step (inverse) and incremental sheet metal stamping analysis

Material models

Some of the material models available in Radioss are:

• gases
• Metals
• Plastics
• Glass
• Foams
• Fabrics
• Rubbers
• Elastomers
• Polymers
• Honeycombs
• Concrete & soils
• turbulent and/or Viscous fluids
• Detonation products of high explosives
• porous material
• Springs
• Composite materials
• Glues
• User-defined materials

Element library

Some of the element types available in Radioss are:

• Beams (standard, integrated-beam, trusses, discrete, cables, and welds)
• Discrete Elements (Springs and Dampers)
• Lumped Masses
• Accelerometers
• Sensors
• Seat Belts
• Shells (3, 4-node) (with 3 shell element formulations, namely, Belytschko-Tsay, Batoz-Dhatt and Zeng-Combescure^[11]) but also shells for composites or sandwich materials.
• Solids
• SPH Elements
• Arbitrary Lagrangian Eulerian (ALE)
• Thick Shells (8-node)
• void (nothing)

Difference between Radioss and OpenRadioss

Radioss and OpenRadioss are very similar to each other but there are some small differences. The differences are mostly relevant for the automotive industry. These are: ^[12][13]

• OpenRadioss does not have the encryption keyword which is used to read-in encrypted commercial crash test dummies.
• OpenRadioss does not have some airbag keywords.
• OpenRadioss does not have the interface with MADYMO, which is also commonly used for commercial crash test dummies.

Other features of Radioss and OpenRadioss are nearly identical. OpenRadioss is the code that developers work actively on.^[14] This means that OpenRadioss commonly is ahead of Radioss but Radioss is tested better by Altair.