Crash Analysis: Tibia Index (ChnTICalc)

[gemu]

Hello,

I have some questions to the DIAdem (2010/2012/2014)  Tibia Index calculation (ChnTICalc)

The DIAdem (2014)  Help tells me in "Dialog Boxes > DIAdem ANALYSIS > Crash Analysis > Crash Analysis (TI):

Moment Mx Specifies the CFC600-filtered data channel ...
Moment My Specifies the CFC600-filtered data channel ...
Compression force Fz Specifies the CFC600-filtered data channel ...

On the other hand in "Programming Reference > Alphabetical Programming Reference > Commands and Functions > Command: ChnTICalc"

Note  The input channels must be filtered with CFC600.

Question 1: Does ChnTICalc expect the unfiltered or the CFC600 prefiltered channels?

DIAdem (2014)  help tells me in "Basics > DIAdem ANALYSIS > Crash Analysis Criteria > Abdominal Criteria > TI"

Note  For the calculation only the axial compression forces are used. The tensile forces must be set to the value 0.

Question 2: Does ChnTICalc set the tensile force to the value 0?

ChnTICalc calculates the TI result channel and returns the maximum in the TIres variable.

I need this channel for an report plot together with limiting curves

Question 3: Is it possible to keep the whole TI result channel?

Thanks

gemu

[SAndreas]

Hi gemu

Answer 1: Do have seen there is a note in CHnTICal. The note says that all input channels have to be CFC600 prefiltered.

=> So the function expects CFC 600 prefiltered channels.

Command: ChnTICalc

http://zone-test.ni.com/reference/en-XX/help/370858M-01/comoff/chnticalc/

Answer 2: The note is linked to the input channels. You have to filter the axial compression force with CFC600. Is there a tensile force

(which I guess would be shown negative) you have to clamp those values to 0.

Answer 3: You want to have a running TI value or just the returned value in an own channel for plotting?

[gemu]

Hi Andreas,

thanks for your annotations to Q1 and Q2

I will take the prefiltered channels and cut off the tensile part.

Q3: Yes,  I want to have a running TI.

My customers want to see the TI curve together with some Euro NCAP limiting curves.

Regards

gemu

[SAndreas]

Hi gemu

I would say the function returns you just the maximum and you can't change that.

I would say you have two workarounds.

- You could implement the calculation by your own.

- You split the channels in sub channels of minimum 3 samples. With 3 Sample a TI calculation should be possible. Then iterate thru your data channels and calculate TI values. Extract the TI value into a separate result channels.

I hope one of those two workarounds helps you.

[gemu · Accepted solution]

Hi Andreas,

thanks for your workarounds.

I have implemented the calculation by my own.

See the code below. Maybe somebody else needs the TI-curve.

Dim oAg, oTI
Set oAg = Data.Root.ActiveChannelGroup.Channels
Set oTI = ChnTICalcObj(oAg("11TIBILEUPH3MOXB"), oAg("11TIBILEUPH3MOYB"), oAG("11TIBILEUPH3FOZB"), _
                            225.0, 35.9, "11TIINLEUPH3000B", "Tibia Index Curve")

msgbox oTI.Properties.Item("Maximum").Value

Function ChnTICalcObj (ByVal MxObj_Nm, _
                       ByVal MyObj_Nm, _
                       ByVal FzObj_kN, _
                       ByVal Mcr_Nm, _
                       ByVal Fcz_kN, _
                       ByVal sTI_ResultName, _
                       ByVal sTI_ResultDescription)

                        
  Set ChnTICalcObj = MxObj_Nm.ChannelGroup.Channels.Add(sTI_ResultName, DataTypeFloat64)
  With ChnTICalcObj
    .Name = sTI_ResultName
    .Properties.Item("unit_string").Value = ""
    .Properties.Item("description").Value = sTI_ResultDescription
  End With                        
                       
  Dim sFormula, aSymbols(5), aValues(5)

  sFormula = "TI = Abs(Sqr(Mx^2 + My^2) / Mcr) + Abs((-Fz * (Fz < 0.0)) / Fcz)"
  
  aSymbols(0) = "TI"
  aSymbols(1) = "Mx"
  aSymbols(2) = "My"
  aSymbols(3) = "Fz"
  aSymbols(4) = "Mcr"
  aSymbols(5) = "Fcz"

  Set aValues(0) = ChnTICalcObj
  Set aValues(1) = MxObj_Nm
  Set aValues(2) = MyObj_Nm
  Set aValues(3) = FzObj_kN
      aValues(4) = Mcr_Nm
      aValues(5) = Fcz_kN
  
  Call Calculate(sFormula, aSymbols, aValues)
End Function

Regards

gemu