TNO & Royal Netherlands International Defense Research Program

DTRL contributed to an anti air missile defense project carried out for TNO within an International Defense Research Program. Feasibility of Post-Intercept Spectral Analysis (PISA) is investigated by hypervelocity impact experiments of aluminum cylindrical projectiles on target plates of various materials. Hydrocode simulations of some experiments have been performed, based on the SPH technique and utilizing the Tillotson metallic equation of state for hypervelocity impact. P-V diagrams visualize sublimation of the material into the gas phase and temperatures are predicted up to 3500 K.  Future work will focus on the prediction of emission spectra based on present simulation results. 

 

 

TNO – BASF Ludwigshafen

The mechanical response of process piping loaded by an internal moving gas detonation has been investigated by DTRL, supporting the TNO Flow and Structural Dynamics section in a research project with BASF Ludwigshafen. Combined analytical and numerical methods have been explored in order to gain insight in the dynamic pipe response at high strain rate loading and elastic-plastic deformation. Special attention has been paid to the influence of:

• Detonation (critical) velocity
• Material properties
• Limited plasticity and strain rate effects
• Pipe bends, dead ends & T-sections
• Pipe corrosion & assymetric loading
• Detonation decay time
• Mode coupling
• Reflected flexural waves

Used Methods/Software:

• Matcad / Maple / LS-Dyna
• Analytical & numerical modelling
• Comparison with experiments

Results have been published in:

J.P.M. Smeulers, G. Pape, Design Rules for Pipe Systems Subject to Internal Explosions, PVP2010-25695 (Part 1) & PVP2010-26177 (Part 2), Proceedings of the 2010 Pressure Vessel & Piping Conference, Bellevue, Washington.

J.P.M. Smeulers, G. Pape,  N.E. Ligterink, Modeling of the Effect of Plasticity on the Response of Pipe Systems to Internal Explosions, PVP2012-78482, Proceedings of the 2012 Pressure Vessels & Piping Conference, Toronto, Canada.

H.P. Schildberg, J.P.M. Smeulers, G. Pape,  Experimental Determination of the Static Equivalent Pressures of Gas Phase Detonations in Pipes and Comparison with Numerical Models, PVP2013-97677, Proceedings of the 2013 Pressure Vessels & Piping Conference, Paris, France.

TNO – Royal Netherlands Air Force

For the TNO Defence and Safety department a failure model has been developed for aluminium aircraft structures being loaded by fragments and blast from missiles. The fragments penetrate the structure and subsequent blast causes deformation and failure of e.g. fuselage and wings. Combined experimental and numerical methods have been explored in order to gain insight in the failure behaviour of the aircraft materials at high strain rate loading and deformation. Special attention has been paid to influences of:

• Different aluminium alloys
• Bending and tensile deformation
• Strain rate effects
• Perforation size

A significant number of experiments have been carried out focusing on aforementioned effects. Experiments and simulations are applied to define a numerical failure model  that was implemented in the finite element code LS-Dyna, allowing for variations of aforementioned parameters. A specialised shell element subroutine provides a failure prediction based on a single element strain data. In this way, the model remains simple and has no effect on the calculation effort for a failure analysis.

The model can be applied in predicting missile effects on aircrafts, residual strength of aluminium structures after missile attack, effects of terroristic threat on structures, etc.

Applied methods & software:

• Abaqus / LS-Dyna, subroutine programming in Fortran
• Experiments on (perforated) samples from F16 fighterjet

TNO – European Launch Vehicle (ELV)

DTRL has analysed the Vega launcher interface of the third solid propulsion stage and the liquid propulsion upper module in collaboration with TNO. A non-lineair FEM model was applied that provided detailled insight into the slip and deformation at the interface during flight. Analyses of different load-cases as well as parametric studies have been performed in order to investigate the effect of mechanical and contact properties tolerances. The results have been used in the launcher design process and subsequent tests were carried out by ELV to verify the numerical results.

Applied software:

• Matlab
• Abaqus implicit

Province of Zeeland – Vopak Terminal Vlissingen

Wind energy is gaining popularity also in the Netherlands. Government’s attention is being attracted by the possibility of accidents by placement of (large) wind turbines close to industrialised or populated regions. For a case in the south-west of the Netherlands, more insight had to be gained on the risk of a wind turbine placement close to a liquid gas transfer station. A study has been performed in order to assess the effect of a wind turbine blade failure and subsequent blade crash onto a nearby liquid gas tank wagons, with risk  of a BLEVE and/or sympathetic detonation.
A literature study provided sufficient information on related subjects such as tank wagon crash studies and failure assessment. In a preliminary study the structural properties, i.e. geometry and material, of the concerning structures have been retrieved from general sources and manufacturers. Data sheets and manufacturers info provided useful information on different operating conditions. An explicit finite element analysis has been performed of a wind turbine blade impact onto the liquid gas filled tank wagon, taking into account the variations in operating conditions. A simple fracture criterion, distinguishing between different material properties of the pressure vessel steel and the welds, indicated fracture initiation and onset of leakage of the tank wagon. Subsequent effects have not been regarded. Resulting graphs showed the relation of the internal tank pressure and colliding mass at a given velocity, for the condition of failure initiation in the pressure vessel steel and in the weld.
The results of this study have been applied in decision-making with respect to the request for building activity of a specific wind turbine close to a liquid gas transfer station.

Applied methods / software:

• Abaqus explicit

TNO – Defence Materiel Organisation

Increasing demands on ship explosion resistance require adequate modelling of the deformation and fracture behaviour of the ship structure at internal explosion loads. A large project (including a PhD project) is being performed in order to test and model the welded ship structure under explosion loading. Tensile tests at a velocity of 1,000 mm/s have been performed on large welded plate specimens. Modelling of the experiments including strain rate effects and material transitions at the welds, provides numerical predictions of ductile fracture.

Applied methods & software:

• Abaqus / LS-Dyna
• Materials testing at static & high strain rates
• Experiments on welded plates
• Full scale experiments of explosion loaded ship bulkheads

 

TNO – Delft University of Technology

During a PhD project the fracture behaviour of ship steel was investigated at low and high strain rates. A high strain rate experimental facility was developed including high speed film analysis. Both the deformation and fracture behaviour of ship steel Fe E 355 E KN EU 156 Mod have been analysed and numerical models were evaluated for ductile failure predictions including strain rate effects.

Applied methods & software:

• Abaqus / Marc-Mentat
• Material experiments stiatic / high strain rate
• High speed film analysis
• Microscopy (SEM, optical)
• Chemical composition analysis

The pictures show SEM microscopy images of ferrite-perlite material structure and fracture surfaces. A manganese inclusion as initiatior of microsopic holes is shown as well as a cross section with hole distribution at large strains prior to fracture of a tensile sample.