Personal tools

Session 17

Simulation of ice action loads on off shore structures
During the last years, there has been an increasing amount of work published regarding simulation of ice action on structures using finite element models of the ice. The effect of ice fracture is in these models approximated using cohesive elements. In this article we give an overview of the cohesive element method for ice modelling including recent improvements made by the authors. A description is given of the implementation of the cohesive element method for modelling floating ice sheets in LS- DYNA including effects such as buoyancy. To demonstrate the performance and robustness of the implementation, numerical results are presented from a full scale simulation of an ice sheet impacting an offshore structure.
Orion space craft water and land landing system simulation; An injury case study
NASA’s return to moon program had kept the NESC (NASA Engineering and Safety Center) busy for the past several years. The NESC was charged to come up with a safe landing for the Orion capsule. Water and land landing is considered for the Orion capsule. The NESC took major initiative to come up with recommendation to the program. Part of this initiative is to come up with Injury criteria recommendation during the landing of the Orion capsule. Impact simulation is used to assess the injury and pulse responses of the Orion during landing. Major tasks were under taken to validate the steps of the impact simulations. The models used in water landing, soil landing, and the finite element dummies were validated through experimental testing. In here some of the validation is presented. The paper finally compares the injury values of the astronauts during water and land landing.
Hail Impact Simulation on CFC Covers of a Transport Aircraft
Due to increasing weight saving requirements in new aircraft, structures traditionally built from aluminium alloys are increasingly replaced by carbon fibre reinforced Composites (CFC). For the preliminary flight clearance hail imact si- mulations were perfomed on CFC covers. For the composite material the authors applied a user- defined material. Behaviour of ice / hail stone was modeled through fitting of parameters for the Johnson–Cook material model to appropriate test data. While the precision of simulations was sufficient for a preliminary assessment, further tests will be necessary for permanent approval as well as for refinement of numerical models.
Development of a water filled fender system for off-shore installations
In order to extend the life and productivity of an off-shore oil and gas platform an new installation has been proposed to provide a compression unit. The existing platform is already extensively occupied, having been in existence for over 25 years, and a new approach was required to facilitate the compression unit. This additional facility is an addition outside the existing envelope of the platform and in line with requirements it must withstand a direct ship impact of given mass and velocity. It has been proposed that a fender system be designed that will absorb the energy from the ship impact allowing time to facilitate repair of the platform extension without the need to stop production from the platform. LS-DYNA has been used to model the platform, the proposed extension and the fender system to determine the effects of the ship impact. As with all projects the requirements have changed during the investigation and this paper only represents some of the investigation in to suitability and design of a proposed fender system
An airbag application for the ALAR incidences for the Passenger Aircrafts
The airbag system can be designed to reduce the damage on the fuselage during an Approach and Landing Accident Reduction (ALAR) situations as well as ditching in the water for the transcontinental flights. Minimum hull damage protects the passengers in deep waters. A preliminary investigation for this end is performed in this paper. A simple model under 10000 elements is used to investigate the problem. The findings of the LS-DYNA finite element simulation are reported in this paper. It also shows a filtering effect on the impact pulse on the structure. The spikes on the deceleration pulse can create injury to the occupants. The airbag filters the pulse thus reducing various injuries to the occupant apart from hull protection. The most useful feature is its automatic deployment at the most critical moment. This is also useful for the small and mid-size aircrafts to survive various ALAR incidences. It saves life as well as property in case of the small crafts.