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X.E.2.3 One using the Cauchy stress tensor

The module “Post_Cauchy” performs the post-processing of Results corresponding to the Cauchy stress tensor. Presently, three criteria corresponding to the stress tensor are available: an “Airbus” criterion for the calculation of honeycomb, a “MaxShear” criterion for the calculation of honeycomb, and a “VonMises” criterion for the calculation of metallic parts.

X.E.2.3.1 Member data

The class has three member data:

X.E.2.3.2 “calcOneGroup” method

This method has one more argument than the corresponding method in “Post_Connect” module:

   def Post_Cauchy::calcOneGroup(db,lcName,scName,paramsMethod)

“paramsMethod” is the method to be called when one wishes to retrieve calculation parameters.

“calcOneGroup” performs the building of “stressTensor” member data by retrieving the corresponding Results. The first operations performed by the method are programmed as follows:

      grp = db.getGroupCopy(@@groupName)  
 
      params = paramsMethod.call(nil)  
      interpolation = params["interpolation"]  
      layers = params["layers"]  
      criteriaList=params["criteriaList"]  
 
      @@stressTensor=db.getResultCopy(lcName,scName,'  
         "Stress Tensor",interpolation,grp,layers)

So far, the method is not very different than the corresponding method of “Post_Connect” module. Just note the way the parameters method is called.

The rest of the method is similar too:

      criteriaList.each do |critName|  
         case critName  
         when "airbus" then  
            crit_HoneyAirbus(db,lcName,scName,paramsMethod)  
         when "maxShear" then  
            crit_HoneyMaxShear(db,lcName,scName,paramsMethod)  
         when "vonMises" then  
            crit_VonMises(db,lcName,scName,paramsMethod)  
         end  
      end

The different methods that performs the criteria calculations are called if necessary. Note that the method to be called to retrieve parameters is passed as argument to the different criteria methods.

X.E.2.3.3 Airbus criterion

This criterion, defined by “crit_HoneyAirbus” method is used to calculate margins of safety in the honeycomb with the following expression:

MoS = 1 FoSτL σL 2 + τW σW 2 - 1,

in which τL and τL are the honeycomb longitudinal and transversal shear components of Cauchy stress tensor and σL and σW the corresponding allowables.

As the programming of the criterion is not more complicated than the programming of “Post_Connect” module criteria, one does not describe the instructions.

X.E.2.3.4 MaxShear criterion

This criterion, defined by “crit_HoneyMaxShear” method is used to calculate margins of safety in the honeycomb with the following expression:

MoS = σW FoS * τ - 1,

in which τ is the maximum shear stress and σW the transverse shear allowable.

X.E.2.3.5 Von Mises criterion

This criterion, defined by “crit_VonMises” method is used to calculate margins of safety in the metallic parts with the following expression:

MoS = Ft FoS * σV M - 1,

in which σV M is the Von Mises equivalent stress and Ft the material tensile allowable.

X.E.2.3.6 “Post_honeycomb” specialization module

This module includes “Post_Cauchy” module:

module Post_honeycomb  
 
   include Post_Cauchy  
 
   ...

This means that the methods of “Post_Cauchy” module are now visible in “Post_honeycomb”. In this example, the module has two specific methods:

1.
“calcAll” defines the list of Groups on which honeycomb margins are calculated. Then, a loop on this list is done and the “calcOneGroup” of “Post_Cauchy”
      list = ["pan_MX_Honey_50", "pan_MY_Honey_50", "pan_PX_Honey_50",  
              "pan_PY_Honey_50", "pan_PZ_Honey_72", "pan_SUP_Honey_50"]  
 
      list.each do |groupName|  
         @@groupName=groupName  
         Post_Cauchy::calcOneGroup(db,lcName,scName,method(:getParameters))  
      end

Note that the call to “calcOneGroup” has a fourth parameter: the method that shall be called to retrieve the necessary data.

2.
This method “getParameters” is the second method defined in “Post_honeycomb” module. This method is similar to the corresponding method in “Post_Connect” module.

X.E.2.3.7 “Post_skins” specialization module

This module is very similar to ‘Post_honeycomb” module.