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Structural safety of means of transport under fast transients

Objective

Specific Objectives

The project addresses the following policy issues related to prenormative and standardization Commission actions:
- Crash worthiness of vehicles for occupants;
- Pedestrian safety (normative action under preparation);
- Safety of road equipment;
- Safety of industrial installations against accidents (explosions, impact);
- Structural aspects of nuclear safety.

In addition, expertise and coordination of expertise are developed in the following areas of structural dynamics:

- Safety of civil structures and material response under impact or blast loading;
- Provision at European level of reference measurement tests for material and large component behaviour in high strain-rate range;
- Safety prediction of industrial installations involving fluid-structure interaction in fast transient regime;
- Safety of structural components under repeated loading.

For 2002 the activities will entail:
- Continuation of precision impact tests on real size road safety barriers using the Large Dynamic Test Facility, with validation of relevant FEM codes predictions. Emphasis will be also placed on biomechanical aspects. Materials and road barrier geometries causing reduced injury levels to the vehicle passengers will be sought and dynamically tested;
- Precision Impact testing on the front part of a RENAULT CLIO car will resume (phase II of DG-ENTR project); agreement with numerical simulation results will be examined;
- Validation of strain-rate sensitive material laws from Hopkinson bar experiments. Particular attention will be given to foams, which show good energy absorption capabilities and may be potentially employed for improving the pedestrian friendliness of the car fronts;
- Developments into the EUROPLEXUS code environment: improvement of data structure, model development according to internal needs (support to LDTF experiments) and external requirements (partnership).
Planned Deliverables

Specific deliverables to DGs:

To DG ENTR:

- Further input for directives EC 96/27 and 96/79 on crashworthiness of vehicles; particular attention will be given to the validation of computer codes for producing reliable simulation results;
- Support in the development of a new normative action on pedestrian safety. The participation of the JRC as a member of a Monitoring Committee will be pursued. The committee is to be set up by the Commission in order to follow the implementation of the eventual Agreement (together with representatives of the automobile industry);
- Technology transfer: final phase of the industrialisation of finite element software for fluid-structure interaction; exploitation of patents of machines for material dynamic testing by a spin-off company.

To DG RTD and ENTR:

- Input for standards EN1317 1,2 on road safety barriers, where apart from the issue of computer code validations, biomechanics and enhanced protection of the vehicle passengers are also introduced.

As a result of the research:

Scientific knowledge is produced of interest to the policies of the DGs involved and to the several standardization bodies: EEVC (European Enhanced Vehicle-Safety Committee), ACEA (Association des Constructeurs Europeens d'Automobiles), CEN/TC226 (for road safety barriers), CEN/TC250 and RILEM (for concrete and anchors construction standards).This includes both experimental and modelling contributions. The experimental work under fast dynamic loading comprises:

- Dynamic mechanical characterisation of materials (steel, aluminium, concrete) for the calibration of constitutive laws; biaxial testing is included.

Measurement of energy absorption of passive safety structural components.
- Validation of predictive computer models by precision structural tests ranging from impacting automotive components to dynamic pull-out of anchors from concrete;
- Provision of reference measurement tests for material and large component behaviour in high strain-rate range: LDTF continuously participates in SCA projects together with the major European nuclear organizations.

The modelling and simulations work, regarding the safety prediction of industrial installations involving fluid-structure interaction in fast transient regime currently comprises:
- The industrialisation of the finite-element based fluid-structure interaction software PLEXIS- 3C (technology transfer);
- A collaboration with CEA and a network of major partners (ENEL, EDF, SNECMA, SAMTECH) on the development of an integrated, new generation software (EUROPLEXUS) for fast transient dynamics industrial problems;
- The implementation of innovative ideas of fatigue life models for structural components (mainly supported through SCA projects).

Summary of 2001 Deliverables: 31/12/2001

- A series of impact tests of road safety barriers (standard EN1317 1,2) have been performed with several barrier systems of European manufactures. The activity included laboratory precision tests at the LDTF and standard field tests at LIER in Lyon. Comparisons of experimental results and numerical simulations, carried out by the Spanish LABEIN, have been made. The final report of this Supp. Com. Project has been delivered to DG-ENTR.
- The final reports concerning structural safety of concrete, anchors in concrete and nuclear steels under explosion and blast conditions have been delivered to DG RTD.
- The integration of current capabilities in fast transient dynamics and fluid structure interaction into EUROPLEXUS software is completed. An agreement for the development and marketing of EUROPLEXUS software between JRC, CEA and a software company is under final negotiation;
- Technical support has been provided to DG-ENTR on pedestrian friendliness o cars during the Commission college hearing on the subject in Feb. 2001 (voluntary agreement versus directive options).

Output Indicators and Impact

As stated above, the basic objective of this project is the assessment of structural safety under fast dynamic loads via reliable software tools based on Finite Element techniques. This in turn requires validated material and structural models, which only precision testing can provide. All these aspects of the problem are being adequately and effectively achieved:

- Publications have been produced in the form of technical notes, conference papers and papers in refereed scientific journals;

- The industrialisation of the JRC finite-element based fluid-structure interaction software PLEXIS-3C is proceeding to its final phase in collaboration with CEA. Indicative of the validity of the product is the fact that a major private software house (SAMTECH) is leading this action, and a network of major partners (ENEL, EDF, SNECMA) has informally been formed;

- Due to its established expertise in the Transient Dynamics field, the sector has been continuously invited to participate to SCA projects together with major European organizations, such as CEA, FZK, FRAMATOME, MPA, EDF, SIEMENS, ENEA, ENSA;

- Finally, and most importantly, a major part of the work bears impact and is oriented towards scientifically supporting Commission policies. In fact, some of it is funded within DG-ENTR Support Com. projects.

As mentioned above such policies are:
- directives EC 96/27 and 96/79 on crashworthiness of vehicles;
- ongoing normative action on pedestrian safety (EEVC European Enhanced Vehicle-Safety Committee and ACEA Association des Constructeurs Europeens d'Automobiles);
-standards EN1317 1,2 on road safety barriers (CEN/TC226).
Summary of the project

Project 33 aims at validating the safety of various structural systems (mainly in transport, energy production and industrial plants) under fast transients (such as crash, impact, blast and explosion). It involves the integrated use of Computational Mechanics (CM) methods for theoretical prediction and of experimental validation through the use of the Large Dynamic Test Facility (LDTF) and of the Dynamic Material Properties Laboratory. An important part of the project aims at developing software to verify the safety of structures operating in a highly non-linear regime and to validate the models that are generally used for the safety assessment of industrial structural systems. It also aims at developing numerical models to study structures interacting with a fluid environment (fluid/structure interaction) as encountered in various engineering fields. The experimental part of the research is mainly focused towards transport safety and is essentially devoted to crash worthiness prediction of structures, characterisation of structural and material behaviour under impact conditions, energy absorption through structural deformation, pedestrian friendliness of car fronts.

Rationale

Structural safety under fast transients is a major concern of the modern society for the life protection of citizens since it concerns: industry and energy production infrastructures; automotive, aeronautical and water transportation systems, civil structures under accidental or perpetrated attacks. Both numerical modelling and experimental testing play an essential role in the context of structural safety assessment.
In all industrial applications, the increased severity of safety standards puts serious constraints on the behaviour of structural systems. As an example, the forthcoming normative action on pedestrian friendliness of front car bodies puts new, very stringent requirements on car design and material selection. These should be satisfied without reduction of safety standards regarding frontal crash safety as well as other performance criteria.
More generally, the project aims thus at providing to the competent authorities and to the scientific community the support of advanced research in the field of structural safety under fast, transient loading. This research makes use of the computational mechanics expertise and of the unique dynamic testing facilities available at JRC.

Coordinator

Institute for the Protection and Security of the Citizen
Address

Ispra
Italy