Bolts Assesment GUI¶

CASSY allows to perform the assessment of one or more flanged connections (i.e. collections of bolts) at the same time. The inputs for the assessment are the geometrical parameters of the bolts and the forces and moments acting on them (actions).

The actions file¶

One action file must be specified for each flanged connection/model to be assessed. This file will contain the actions used to create load combinations. All the actions at all loadsteps and analyses of interest are included here for all the bolts of the model.

The columns of the csv file are:

• boltID: ID of the bolt
• analysis: name of the analysis from which the actions are extracted from
• loadstep: loadstep of the analysis from which the actions are extracted from
• Fx: Fx shear force acting on the bolt section
• Fy: Fy shear force acting on the bolt section
• Fz: Fz normal force acting on the bolt section
• Mz: Mz moment action on the bolt section
• Mx: Mx moment action on the bolt section
• My: My moment action on the bolt section

Any other column in the file is ignored.

CASSY is FEM code agnostic, but a collection of script to extract data from different workflows (e.g., APDL, Mechanical, ABAQUS, etc.) in a suitable format ready to be used in CASSY can be found here.

General Tab¶

Once the csv files are ready, the GUI can be opened using:

python -m cassy --boltsgui

The GUI will open on the General Tab where the main run options can be set:

• Fatigue assessment, controls if the fatigue assessment is performed or not
• Generate Word recap, if unchecked only the Excel results are written (faster)
• Merge repeated cells in Word tables, makes the Word tables more readable but is slower
• Assess only bolts (skip inserts), skip the assessment of the base material threads
• Locations CSV, optional, coordinates of the bolts of all the flanges, used only to show where they are in the HTML report of the trace. See 3D location map.
• Additional materials folder, allows the user to point to folder that can contain additional material files that are not included in CASSY default library. These must be in yaml format, see materials.
• Output root folder, browse to a destination folder where to output all CASSY results

Geometries Tab¶

Here you can build/modify the geometry library for bolts and inserts dimensions.These libraries can be used cross projects and can be exported and imported as json files using the Export library and Import library buttons.

When adding a new bolt, an ID (usually something like 'M16') a material, and a number of geometrical parameters will need to be provided. Users can insert all of them or just the minimum set that allows to compute the remaining ones using ISO formulas. This can be done using the Auto-compute button in the pop-up dialogue that opens when adding a new bolt geometry.

Base material threads also have to be checked. At the end of the pop-up dialogue the user can mark the has dedicated insert geometry which will allow to define geometrical properties of an insert (if present). If no insert is defined, the base material threads are assumed to have the same geometry of the bolts one. If an insert is provided, the base material thread geometry will be the same as the outer threads of the insert.

Flanges Tab¶

In this tab, all flanges/submodels will need to be defined. The GUI will ask for: * Name, name of the submodel that will be used in the outputs * Design Code, drop-down menu that allows you to select one of the available design codes. * Stress tensor CSV, browse to link each submodel with its forces and moments input .csv as discussed above. * Geometry (STL), optional, used only to show where the bolts are in the HTML report of the trace, together with the locations CSV of the General tab. See 3D location map.

Bolts Specs Tab¶

For each of the flanges/submodel, a number of bolts to assess needs to be defined. For each bolt an ID (use progressive integers), a geometry and a preload value must be assigned.

Ref. Events tab¶

Once the single loads have been defined, Reference Events (i.e. load combinations) can be built. For each reference event, the following data is specified:

• RE ID, identifier for the reference event.
• Service Level, either "A", "C" or "D".
• Load Ctg. loading category for the event (eg. I, II, ...) it is not mandatory for the assessment, it will only be used in reporting.
• Operating Conditions, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• Initiating Event, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• Concatenated Event, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• Primary Action, linear combination of actions giving the primary loads (see load combinations).
• All Loads Action, linear combination of actions giving all loads (see load combinations).

Load combinations¶

Each action is defined as a list of terms, added with the + Add term button. Every term requires a sign (+ or -), an analysis and a step, which must match the analysis and loadstep columns of the actions .csv file. Terms can come from different analyses, e.g. + X:1 and - Y:5 computes step 1 of analysis X minus step 5 of analysis Y.

Fat. Ref. Event tab¶

Similarly to what is done for regular reference events, fatigue ones also have to be defined:

• RE ID, identifier for the reference event.
• Service Level, either "A", "C" or "D".
• Load Ctg. loading category for the event (eg. I, II, ...) it is not mandatory for the assessment, it will only be used in reporting.
• Operating Conditions, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• Initiating Event, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• Concatenated Event, description of the event, it is not mandatory for the assessment, it will only be used in reporting.
• N cycles, number of cycles to be considered for the specific load combination.
• Delta sigma+, Delta sigma-, the load combinations that compose the delta of the actions. The resulting cyclic actions are computed as sigma+ - sigma-.
• Sigma sustained, optional load combination giving the sustained primary actions.

T & DPA Tab¶

For each combination of Reference Event, submodel and bolt, a temperature and DPA value must be associated. Once all the previous configurations have been set, click on Refresh grid to compute the grid that needs to be filled.