Mechanical shock testing
With over 50 years of experience, TNO provides both experimental and theoretical shock expertise for a world-wide customer base. The TNO shock facilities have been developed to simulate the effect of...
After the immediate effects, the ship may suffer additional damage due to fire and flooding, or loss of self-defence resources. For a resilient ship design an integrated approach is required based smart design, test and analysis methods and facilities. For over 40 years, TNO has been playing a leading role in the development and application of these measures and tools.
A well-designed surface ship or submarine should be able to withstand weapon damage while retaining sufficient fighting, sailing or floating capability. If, in the early design phases, sufficient attention is paid to enhancing ship survivability, large cost and weight penalties in a later stage can be avoided.
Survivability increasing measures can take on many forms. Structural elements can be modified to reduce the transmission of loads to sensitive areas. For the same reason equipment shock mounts may be implemented. Important spaces can be protected by blast resistant doors and bulkheads. TNO is developing low weight, affordable fragment protection for bulkheads. A smart system lay-out will help to achieve a graceful degradation. The expected damage to the ship’s structure can inspire design changes that improve the residual strength. Fire safety engineering will result in safer ships and crews. TNO has investigated and developed structures and systems that are implemented in warships for the navies of the Netherlands, the UK, Norway and other countries.
The shock wave due to an underwater explosions produces a first dynamic load on the ship. Moments later, the collapse of cavitation areas induces a secondary loading. The expansion, contraction and motion of the fume gas bubble causes a third type of dynamic load (whipping). Close-proximity explosions exhibit yet another major damage potential to the hull (jetting). TNO has developed several very efficient models and tools for describing these phenomena. They are validated and improved by using e.g. over 170 acceleration signals from the shock trial of the Air Defence Command Frigate. For qualification or validation purposes, we can subject equipment and research test structures also to prescribed pulses on our three shock testing machines. The use of these facilities and software has resulted in shock resistant designs for the Royal Netherlands Navy, foreign navies and international equipment manufacturers.
The complexities of submarine pressure hulls or (damaged) surface ships exposed to extreme sea conditions show that even steel naval structures still pose a serious challenge to the designer. Composite ship structures exhibit improved weight, cost and ‘stealth‘ properties, but the initiation and progression of failure, especially in joints, is very complex. TNO has developed unique and validated failure prediction tools for both steel and composite structures during the last 15 years.
A calamity on a ship in the wake of an incident unfolds in phases. Six mitigation concepts applied over time will ensure that the ship's operational readiness is restored as quickly and to as high a level as possible: (1) a ship design that is less vulnerable to weapon effects; (2) automated restoration measures; (3) escalation reduction measures in the design; (4) automated escalation reduction; (5) escalation reduction by means of human action; (6) functionality restored by human action.
Our expertise is valuable in both the early design phase and for evaluation of ships as-built: