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NX 11 What's New Expressions

Pioneer
Pioneer

Sir

 

i want to write an expression for force applied on a beam, It is uniformly varying load i.e 0 at length zero and maximum at length x , plz help me and i have gone through the help of nx and i am having lot of confusion in writing, if u have some tutorial regarding the expression plz can u share

 

thank you

1 REPLY

Re: NX 11 What's New Expressions

Siemens Phenom Siemens Phenom
Siemens Phenom

Karthik,

 

Here is an example of a formula based expression used to linearly ramp a load along a beam from 0 to its maximum value. It has the added complexity of having the span of the load vary from one subcase to the next. That is, the start and end points of the load is different for each subcase, while the expression is the same. This may be more complex than your situation, but it gives you an idea for what can be done. Here are some key points to this example.

 

The pressure is based upon two fields

The first field (CSPressureRamp) defines the pressure ramp as a function of location along the Z axis

The second field (CSPressureLoad) uses an IF statement to bound the evaluation of the first field to a sub-region of the length along the Z axis

Both fields use expressions defined in a condition sequence. A condition sequence is generally used to define load parameters in a transient analysis, but in this example I used it to define parameters that change between subcases in a linear statics solution. The parameters are interpreted in the fields as being related to Z coordinates.

Since condition sequences are transient in nature, I assigned unique Evaluation Times to each subcase. This led to the load parameters being able to change from one subcase to the next.

 

CSPressureRamp  is a 4D pressure field dependent on time, and X, Y, and Z location. In actuality, it is dependent on time through the condition sequence and only Z through its formula. Here is its formula.

 

PressureMax*(z-CSLoadStart)/CSHeightDifference

 

That by itself is a good way to define a pressure ramp as a formula. One could edit the model’s geometry to assure that the pressure is applied to only the area of interest. Or you could get more complicated as is done next. The ramp in this example is controlled by an IF statement in the load’s field CSPressureLoad.

 

if(z>CSLoadStart && z<CSLoadEnd) then fd("CSPressureRamp") else 0.0

 

CSLoadStart and CSLoadEnd are condition parameters that vary with time. Evaluation times are assigned to each subcase to mimic a transient condition in this linear statics, multiple subcase solution. Here the same load is applied in each subcase, but the evaluation of the load changes due to its dependence on time. The following table shows how CSLoadStart and CSLoadEnd vary with time.

 

Time

CSLoadStart

CSLoadEnd

CSHeightDifference

1

20

100

80

2

50

150

100

3

50

200

150

 

Along with the model is an AVI showing the features of the model’s load. You may need to install the CAMTASIA CODEC to view the AVI.

 

If you only want to study a single ramp over your model, then you could also define a table field in terms of a single coordinate value. You can pick points on your model to assign pressure values and have the field evaluated through table field interpolation methods.

 

Regards,

Mark

 

 

Mark Lamping

Simulation Product Management

Simulation and Test Solutions

 

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

mark.lamping@siemens.com

www.siemens.com/plm