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SFI CASA-researchers shared a wide variety of news with global industry players at the LS-DYNA conference.
More than 830 participants joined this year’s conference, which also was the first-ever hybrid conference. In total, 600 of the participants joined online. LS-DYNA is a multi-physics software package capable of simulating the complex deformation behaviour of structures.
Postdoctor Karoline Osnes (photo right) is SFI CASA’s expert on the behaviour of glass under extreme impact. The backdrop for the study she presented, is that more than half of all road fatalities involve vulnerable road users, such as pedestrians and cyclists. In a car crash, the head is particularly susceptible to injuries, and the level of injury can be estimated by a head impact test.
HEAD IMPACT ON CAR WINDSHIELDS
The Euro NCAP head impact test only considers pedestrians. However, from 2022, the test will also include cyclists. In this scenario, there is an increased risk of hitting the windshield of the car.
The title of the study presented in Ulm, is «Modelling of Fracture initiation and Post-Fracture Behaviour of Head Impact on Car Windshields». The objective has been to recreate the acceleration-time history of two impact tests on windshields through Finite Element Simulations in LS-DYNA.
Postdoctor Osnes and Professor Tore Børvik have collaborated with research fellows at CASA’s partner BMW Group. The impact tests for the study were performed at BMWs research and innovation centre in Munich in 2019.
You can download the full conference paper here
THE COMPLEX CONCRETE
The LS-DYNA software is a standard tool in the automotive and aerospace industry and construction, civil engineering, military, manufacturing, and bioengineering. Postdoc Andria Antoniou is one of SFI CASA’s experts on ballistic impact on concrete.
She presented a new survey of four material models for ballistic simulations of high-strength concrete. Three of these are available as standard models in LS-DYNA.
The protection of critical infrastructure against ballistic impact scenarios is crucial for the safety of the public. Concrete is the most common material in shielding barriers, but the design poses significant challenges. Thus, there is a great demand for accurate numerical models, especially for conditions involving high strain rates, high triaxial pressures and complicated fracture modes.
EVALUATING THE MOST-USED MODELS
According to Antoniou, accurate data reflecting the material’s behaviour under the aforementioned conditions are rare – and difficult to produce. Three of the most used concrete models are available in LS-DYNA, where there is an option to automatically generate the model. The primary motivation behind the new study is to investigate the accuracy of the default material cards to predict the ballistic impact response of concrete slabs.
Antoniou explained how they evaluated them in uniaxial compression, tension, triaxial hydrostatic compression, and ballistic impact experiments. The postdoc and her fellow researchers Professor Tore Børvik and Researcher Martin Kristoffersen, performed the laboratory experiments with a C75 high-strength concrete in SIMLab test facilities.
You can read about the results and download the full study here.
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THE GROWING PROBLEM OF SPACE DEBRIS
PhD candidate Rannveig Færgestad presented work on Modelling and simulation of hypervelocity impact against debris shields for spacecraft protection.She introduced the LS-DYNA audience to the growing and challenging space debris problem and stated that Low Earth orbit is full of it. Micro-meteoroids or fragments from colliding satellites transform into millions of flying projectiles, posing a significant threat to current and future space missions. Experimental hypervelocity impacts (HVI) are expensive and can only be performed at a few laboratories worldwide. Therefore, spacecraft shielding is vital for future space exploration efforts. Thus, numerical simulations are essential tools in the development and design of debris shields.
ACCURATE MODELS ENSURE SAFETY AND SUSTAINABILITY
Accurate and reliable models of debris impact at hypervelocity are crucial to ensure safety and sustainability in space. In her presentation, Færgestad showed photos of hypervelocity impacts on the International Space Station. She also presented some quite disturbing figures on the fast-growing numbers of different flying object types. You can download the study here.
Rannveig Færgestad started on her PhD studies at SFI CASA this autumn. She has a team of supervisors: Professor Tore Børvik and Researcher Jens Kristian Holmen from SimLab, Tiziana Cardone from the European Space Agency and Kenneth Ford from National Aeronautics and Space Administration, NASA.
PhD candidate Victor André works on modelling techniques for multilayered joints. His approach is that machine learning could increase the accuracy of joint models in FE analyses. Read more on Andrés presentation at LS-DYNA here:
Training Neural Networks to Predict the Behaviour of Mechanical Joints.
Also, three former PhD students at SFI CASA, Henrik Granum. Jens Kristian Holmen and Joakim Johnsen, gave technical presentations at LS-DYNA. They are all employed by the spin off-company Enodo AS.