The following is an excerpt.

CASA’s experts on ballistic impact and their fellow researchers at partner Norwegian Defence Estates Agency investigate the ballistic perforation resistance of concrete slabs. Watch Martin Kristoffersen´s presentation on YouTube.

 

Recently, Researcher Martin Kristoffersen shared news from their research on the 13th International Conference on Mechanical and Physical behaviour of Materials under Dynamic Loading (DYMAT) in Madrid, Spain. 

PROJECTILE AND FRAGMENT IMPACT 
The project’s backdrop is the frequent use of concrete for fortification installations and protective structures. The material is versatile, cheap, and abundant – and possesses high compressive strength. These properties make it the most widely used construction material in the world. 
Potential sources of impact hazards could be impact from projectiles or fragment impact from a nearby blast load. The study Martin Kristoffersen presented at DYMAT aims to determine how three different commercially produced concretes behave under such impact. 

WATCH: This 1-minute Video Shows the Point of Studying Projectile Impact on Concrete

Sumita Dey & Oda Toreskås
Sumita Dey (left) and Oda Toreskås

BEHAVIOUR UNDER IMPACT
Kristoffersen and Professor Tore Børvik are CASA’s ballistic impact experts. In the project presented at DYMAT, they collaborate with researchers Sumita Dey and Oda L. Toreskås at the Norwegian Defence Estates Agency. The presentation summarises a study titled «Ballistic perforation resistance of thin concrete slabs impacted by ogive-nose steel projectiles» published in the International Journal of Impact Engineering earlier this year (IJIE 2021;156:103957).  
After casting and curing the 50 mm thick concrete slabs, the researchers performed ballistic impact tests in the gas gun facility of SIMLab. Here, they determined the ballistic limit curve and velocity for each concrete type. Alongside the impact tests, the team conducted material tests to assess the mechanical properties. 

READ MORE: Partner NDEA Access Labs to Study Impact and Blast Load on Concrete

Portrait of a man with protective glasses
Researcher Martin Kristoffersen.

TO BE CONTINUED
Martin Kristoffersen (photo left), Tore Børvik and their NDEA colleagues predicted the constitutive behaviour of the three concrete types by a modified version of the Holmquist-Johnson-Cook (MHJC) model, previously published by SIMLab researchers (IJIE 2008;35:290-303). The main objective was to reveal the accuracy of the MHJC model for this particular kind of impact. The CASA/NDEA study shows good agreement between the numerical simulations and the experimental data.
There is still ongoing work on the project. Further investigations include perforation tests on thicker slabs (100 mm) and reinforced slabs. According to Kristoffersen, they also aim to investigate other material models’ performance and extend simulations to full 3D. 

4 CASA-RESEARCHERS PRESENTED NOVEL WORK
DYMAT organized The 13th International DYMAT Conference in Madrid, Spain, 20-24 September. The organisation aims to bring together engineers and scientists working on the dynamic behaviour of materials. This research field is relevant in multiple applications, such as 

  • Crashworthiness in transport
  • Terminal ballistics related to defence, shielding of satellites, of turbine blades and discs
  • Blast effects due to industrial explosions and terrorist attacks
  • Material processing such as high-speed shaping of metals

Including Martin Kristoffersen, 4 CASA’ researchers presented novel research at this year’s conference: 

Karoline Osnes: An Alternative Approach to Modelling Ballistic Impact on Laminated Glass
Vegard Aune: Into the Physics of Extreme Blast-structure Interaction Benjamin S. Elveli: About Blasting Steel Plates and Why Material Properties Matter