X-RAI system

Since version 9 the X-RAI system (exterior rigid assembly investigation) to evaluate load paths through the dummy is available. The X-RAI comes as a separate include and can easily be included or excluded from the dummy. The X-RAI has no influence on the performance of the dummy. There are 21 assemblies defined for the X-RAI system to be evaluated:

Validation process

To match the defined assemblies several parts needed to be split. In addition several *CONTACT_FORCE_TRANSDUCERs, *DATABASE_HISTORY_DISCRETEs, *DATABSE_HISTORY_NODEs and *DATABASE_CROSS_SECTIONs were added to track forces.
For the X-RAI to work properly FTALL needs to be set to 1 in *CONTROL_CONTACT. Otherwise not all contact forces might be tracked by the force transducers.

The X-RAI system was validated with the performance sled tests. The validation report is available as a separate file in the delivery package named “es2_v*_X RAI_validation_report.pdf”. In this manual the principle of the validation process is shown.

For the validation of the X-RAI the following equation was considered:

Meaning the mass m_i of assembly i times the acceleration of the initial center of gravity a_cog,i of assembly i needs to be the same as the sum of all forces F_n,i acting on assembly i at each time step.

The masses of the assemblies were calculated with the help of *DATABASE_SSSTAT_MASS_PROPERTIES and the assembly part sets.
The X-RAI nodes to track the accelerations of the 21 assemblies are shown in the table below. Each of these nodes is constrained to a part belonging to the same assembly with *CONTRAINED_EXTRA_NODES or *CONSTRAINED_INTERPOLATION. The nodes are located in the main dummy include.

Forces tracked by X-RAI include

The sum of forces for each assembly consist of *DATABASE_CROSS_SECTION, *DATABASE_HISTORY_DISCRETE, *CONTACT_FORCE_TRANSDUCER_PENALTY.
All of the following definitions for the dummy itself are available in the X-RAI include. Contacts to the environment have to be defined by the user on its own. They are shown later.

The below table shows the available force transducers of the X-RAI include. Each contact is defined between two assemblies which may come into contact. All of the labels begin with “IC_FORCE_TRANSDUCER_”. To make it more clear the beginning of the labels is not shown in the table. The rest of the labels consist of the slave of the contact, the number “2” and the master of the contact (for example HEAD2JACKET: slave is head – master is jacket). The interface numbers can be found in the rcforc output.

The available cross sections are listed below. The cross section output can be found in the secforc output.

The discrete history outputs are listed below. The discrete outputs can be found in deforc.

Additional contact force transducers

Only for the internal interactions the force transducer contacts are directly available in the dummy model with the X-RAI include. All the force transducers for the contact with the environment need to be added by the user.
The delivery package contains an example file with predefined force transducers to environment (”X-RAI_DUMMY2BARRIER_FORCE_TRANSDUCERS”). Within this file fourteen additional force transducer contacts to the environment (barrier) are defined. The slave side of these contacts contains the X-RAI assembly part set (f.e. head) coming into contact with the environment, the master side contains the barrier with part set id #10000.
If there is not just one barrier set available which might come into contact with the dummy, additional contact force transducers have to be defined by the user accordingly to this example file.

Evaluation

The delivery package includes a standard evaluation hypergraph template (es2_v*_X-RAI_S*.tpl) for evaluation. This template contains all outputs needed for the validation process described earlier. For the dummy to environment interactions the template will use the contacts of the example file.