Papers and Publications referencing OpenRadioss

This paper presents the re-implementation of a well-established compaction and shear strength model, originally available in AUTODYN and widely cited in the literature, into OpenRadioss, an open-source explicit solver for broad range of applications, including shock and impact simulations. The objective is to enhance ground shock predictions by accurately capturing the compaction behavior and shear strength of dry sand. The study focuses on Sjöbo sand, a well-characterized quartz sand, with mechanical properties determined through triaxial compression tests under isotropic consolidation. A porous equation of state (EOS) was developed based on volumetric compression data, while shear wave and longitudinal wave velocity measurements provided estimates of bulk sound speed and shear modulus over a range of pressures. The in situ dry density of the sand was approximately 1574 kg/m³, with an average water content of 6.57%. The reimplementation ensures consistency with previous AUTODYN models while leveraging OpenRadioss’ open-source capabilities for broader accessibility and further development. An improved approach for interpolating the unloading behavior from compaction curves was incorporated, ensuring accurate energy dissipation in high-pressure release scenarios. The implementation is validated through single-element tests and particle velocity impact simulations, providing a benchmark for further studies on granular materials under dynamic loading. As a successor to previous research efforts, this work aims to support the OpenRadioss community by providing a validated dry sand material model, enhancing the simulation of granular materials and facilitating further development in open-source computational mechanics.

The aim of this report is to investigate OPENRADIOSS as a (partial) alternative for LSDYNA. LS-DYNA is intensively used in the Naval & Offshore Structures department of TNO (TNO-NOS) to do structural analysis. LS-DYNA is used to calculate mainly the structural response of highly non-linear and dynamic phenomena. The two main motivations for changing from LS-DYNA to OPENRADIOSS are firstly the fact that OPENRADIOSS is open source which means no licenses are required and the code is accessible by TNO (without restrictions). Secondly, OPENRADIOSS has developers supporting users and an open-source community where questions and problems can be asked and discussed. The investigation in this report is mainly focused on the different element formulations and applying these to simulations for which an analytical solution is known. This is done to verify OPENRADIOSS and find any potential problems and bugs such that they can be fixed and made aware of. While investigating OPENRADIOSS the support of the OPENRADIOSS community is also considered.

Safety is a major concern for Li-ion batteries in Electric Vehicles (EVs). Internal fracture of a battery cell may lead to a short circuit, and in extreme cases, cause thermal runaway and explosion. Consequently, heavy protective structures are used around EV battery packs to ensure zero deformation in the event of a vehicle crash. Having a universal failure model for battery short circuits can enable better prediction of imminent safety concerns and provide a tool for designing optimized protective structures. In this work, a failure and short circuit model titled the “Sahraei Failure Criterion” derived from simulations of the microstructure of the electrode-separator assembly, is developed and employed to predict cell failures for two types of cylindrical cells and one pouch cell. The failure model, in combination with a homogenized cell model, is validated in predicting all major loading scenarios, including local hemispherical and rod indentations, three-point bending and in-plane loading. This failure model defines the jellyroll’s in-plane failure strain values as a function of the ratio of through-thickness compressive strain to in-plane tensile strain. A user-defined FORTRAN code has been used to implement the Sahraei failure criterion in RADIOSS. This universal failure model predicts the onset of internal fracture of the jellyroll under all available types of loadings with a single calibrated input curve. The model is also now programmed in the commercial software Altair RADIOSS (and OpenRadioss) as /FAIL/SAHRAEI criteria and is currently being implemented in Ansys LS-DYNA under the *MAT_MODIFIED_HONEYCOMB keyword to be available for users of both software.

The mechanical integrity of two commercially available lithium-ion battery separators was investigated under uniaxial and biaxial loading conditions. Two dry-processed microporous films with polypropylene (PP)/polyethylene (PE)/polypropylene (PP) compositions were studied: Celgard H2010 Trilayer and Celgard Q20S1HX Ceramic-Coated Trilayer. The uniaxial tests were carried out along the machine direction (MD), transverse direction (TD), and diagonal direction (DD). In order to generate a state of in-plane biaxial tension, a pneumatic bulge test setup was prioritized over the commonly performed punch test in an attempt to eliminate the effects of contact friction. The biaxial flow stress–strain behavior of the membranes was deduced via the Panknin–Kruglov method coupled with a 3D Digital Image Correlation (DIC) technique. The findings demonstrate a high degree of in-plane anisotropy in both membranes. The ceramic coating was found to negatively affect the mechanical performance of the trilayer microporous separator, compromising its strength and stretchability, while preserving its failure mode. Derived from experimentally calibrated constitutive models, a finite element model was developed using the explicit solver OpenRadioss. The numerical model was capable of predicting the biaxial deformation of the semicrystalline membranes up until failure, showing a fairly good correlation with the experimental observations.

Implosion may occur when a hollow pressure structure with geometric imperfections works in deep-sea environments. Therefore, the implosion phenomenon and failure mechanisms of a titanium alloy spherical pressure hull are investigated by experiments and developed numerical methods in ultra-high-pressure water conditions. Firstly, the experiments were conducted using a full-ocean-depth sea environment simulator. Then the validity of the numerical analysis were demonstrated by comparing the shock wave of fluid and destroyed fragments of structure. Finally, the characteristics of underwater implosion were examined under different hydrostatic pressures, including the propagation of shock waves, high-speed motion of the compressible flow, nonlinear deformation of the spherical pressure hull, and energy balance and evolution. The results showed that the vertical impact effect occurs during the underwater implosion of a metallic sphere. Moreover, the shock wave emerges earlier and the cracks break into smaller fragments with the increase of hydrostatic pressure. Besides, the smaller volume of the air cavity is compressed and the larger amplitude of potential energy is dropped when the hydrostatic pressure is larger. Meanwhile, the internal energy of air and structure increases, while the internal and kinetic energy of air oscillates slightly due to the pulsation characteristics of the air cavity.

The need for higher capacity battery cells has increased significantly during the past years. Therefore, the subject of this study is to investigate the behavior of high performance 21700 Lithium-Ion cylindric battery cells under several abuse conditions, represented by high mechanical loads with different velocities and states of charge (SoC), and to develop a finite element analysis (FEA) model, using the OpenRadioss’ explicit solver capabilities. The present study is focused on the investigation of the behavior of these cells under high mechanical loads with different loading velocities and different states of charge. The aim of the study is to provide a tool to predict the point of an internal short circuit in FEA, with a very good approximation. Experiments were completed using a hydraulic flat-compression test, set up at four different states of charge, 40%, 60%, 80% and 100%, and three different loading velocities of 10 mm/s, 100 mm/s and 1000 mm/s. A homogenized FEA model is developed to predict the internal damage of the separator, which can lead to a short circuit with a possible thermal runaway under abusive load conditions. The present model, in combination with well identified material and fracture parameters, succeeded in the prediction of the mechanical behavior at various states of charge and mechanical loading conditions; it can also be used for further crashworthiness analysis within a full-car FEA model. This accurate cell model will be the first building block to optimize the protective structures of batteries in electric vehicles, and reduce their weight through a deeper understanding of their overall behavior during the different crash cases.

The present study is focused on the development of a material model where the orthotropicvisco-elastic and orthotropic-visco-plastic mechanical behavior of a polymeric material is considered. The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage of electric powered drive systems using Lithium-ion (Li-ion) batteries. For the safety and crashworthiness investigations, a deeper understanding of the mechanical behavior under high and dynamic loads is needed. In order to prevent internal short circuits and thermal runaways within a Li-ion battery, the separator plays a crucial role. Based on results of material tests, a novel material model for finite element analysis (FEA) is developed using the explicit solver Altair Radioss. Based on this model, the visco-elastic-orthotropic, as well as the visco-plastic-orthotropic, behavior until failure can be modeled. Finally, a FE simulation model of the separator material is performed, using the results of different tensile tests conducted at three different velocities, 0.1 mm/s, 1.0 mm/s and 10.0 mm/s and different orientations of the specimen. The purpose is to predict the anisotropic, rate-dependent stiffness behavior of separator materials in order to improve FE simulations of the mechanical behavior of batteries and therefore reduce the development time of electrically powered vehicles and consumer goods. The present novel material model in combination with a well-suited failure criterion, which considers the different states of stress and anisotropic-visco-dependent failure limits, can be applied for crashworthiness FE analysis. The model succeeded in predicting anisotropic, visco-elastic orthotropic and visco-plastic orthotropic stiffness behavior up to failure.

The implosion will occur when the pressure hulls have a geometric imperfection or are impacted from the outside, which could cause the collapse of submerged vessels. In this work, the open-source finite element solver OpenRadioss is used to analyze the implosion caused by the failure of the spherical pressure hull and the interference with the adjacent cylindrical shell in the double-hulled cabin of a submarine. Firstly, the implosions of the cylindrical tube and destruction of the spherical pressure hull are compared with experimental results. Secondly, the underwater implosion of the sphere is analyzed inside a cylinder with local impacts in different induced directions. The results found the flow field and structural deformation show obvious directivity, in which the deformations of the cylindrical shell are mainly caused by the absorption action instead of the shock wave effect when implosions occur in the direction closer to the cylinder. Finally, the dynamic responses of implosions are discussed under different triggering modes and hydrostatic pressures. We found that the structural deformation and energy evolution are similar when the sphere is subjected to a collapse load. However, the effect of triggering modes gradually becomes larger with the increase of hydrostatic pressure.