Once the gear data are defined in the *.ISP property file you are ready to preprocess gear tooth FE model to get tooth flank contact surfaces and stiffness matrix for Gear AT contact simulation. The Figure 398 shows how to access Gear AT Mesher interface to preprocess your gear before you could define Gear AT Element in Adams model. The data flow involved in the mesh is depicted on Figure 399.

 

FE preprocessing starts by launching Gear AT mesher (orange color; see Figure 399) with input data from *.ISP file prepared in the Gear AT Advanced Shape Definition step and *.opt file which consists of data you input in the FE Data tab of the mesher dialog box. Output of the mesher is Adams geometry *.shl file, flank contact surface for rigid contact modeling in *.ISS file and updated *.ISP file by inertia data of the gear. In order to include gear tooth flexibility in contact simulation, Nastran SOL 101 needs to be executed (green color). The Gear AT op2_reader extends the content of *.ISS file with results from Nastran run.

 

 

The tab options of Create Gear AT Mesh dialog box are

 

 

 

The general tab (Figure 400) displays some parameters of the spline shaft / hub, which are stored in the *.isp file. However, none of them are editable as the tooth profile was defined in the Gear AT Advanced Shape Definition step already.

 

 

You can control resolution of FE mesh and contact mesh of flexible tooth as well as resolution of Adams shell graphics thus performance of the model.

 

 

The parameters for the meshing are stored in a file with the extension *.opt. If this file exists, you can retrieve this data through the Import *.opt toggle.

 

 

Make your choice about Update mass with FE calculation option. In case you select Yes the Gear AT Element mass properties will correspond to the gear ring only, what is effectively the mass of solid represented by the shell graphics. It is assumed you will define the mass properties of the gear wheel body by the shaft part to which you attach the Gear AT Element. In case you defined mass by User Input in Mass tab of the Gear AT Advanced Shape Definition dialog box you should opt for No to not Update mass with FE calculation, hence the Gear AT Element you will define later on will represent mass properties of the gear ring and gear wheel body. In case of Full Flex Gear the mass properties of flexible body are comprised in MNF file, hence the data from the MASS data block of CGP file are not used.

Choose from Coarse, Moderate, Fine, and Ultra options, which are predefined options to control FE mesh and load mesh division over the tooth flank. You can switch on the toggle More to manually enter all input parameters.

 

It defines the number of finite elements along the contact line (involute curve of tooth profile); see Figure 402 and Figure 403. The contact line represents portion of the tooth active profile (flank), where contact is assumed which is bounded by start contact and end contact. The start contact is close to the root for external and internal gears. Valid input entries for mesh density are 2 to 5, representing 24,32,40 or 48 elements along the contact line. For stress post-processing, the mesh density is always set to 5, thus ensure good quality of results for stress computations in Adams/Durability.

This input parameter allows you to select the preference with respect to accuracy versus CPU-time. A low value for mesh density will result in a coarser Nastran model, what gives generally a short CPU-time. One has to keep in mind, that a coarse model is generally slightly stiffer.

The accuracy of the contact computations in Adams by the Gear AT force is not influenced strongly in quality and in CPU-time by mesh density, as the contact algorithm uses constant mesh division along contact line thus ensure accurate definition of the tooth flank surface.

It defines division of the tooth width into a number of equidistant sections in lead direction; see Figure 403. It is suggested, that one uses a similar distance between the contact planes for the mating gears defined in Gear AT Force.

Contact between gear wheels is checked at each contact plane of wheel 1 of the Gear AT force. Having too small number of contact planes may leads to some numerical noise. The amount of CPU time increases with increasing number of contact planes. You need to verify the appropriateness of your selection.

Following default values are implemented:

number contact planes = 20 * ( 1 - u ) + 30 * u

where:

u = width / ( 2 * module * 10 )

It defines the number of finite elements in lead direction per section (between adjacent contact planes); see Figure 403. The length of the section is given by the face width divided by number of contact planes. You can select a value between 1 and 5, where for instance, 2 means there are 2 elements between the contact planes.

A larger number of this input will increase the size of the FE-mesh and hence the CPU-time of the Nastran analysis. However, it does not influence the value of Computed Number of LoadCases.

 

 

This field returns the number of load cases that are calculated in the Nastran Solution 101 what is proportional to the rank of tooth stiffness matrix. This number is proportional to the value of Mesh density and Number of Contact Planes.

Say, for Mesh Density = 2 there are 24 load elements along involute; let’s take 20 Number of Contact Planes =>

(24+1) * (20 + 1) = 525 load cases

It controls resolution of geometrical representation of a gear element in Adams View. It defines the number of FE elements per one shell geometry element in lead direction. The input value of 1 means fine, 2 is for normal and 3 for coarse resolution for the shell graphics.

 

It controls resolution of geometrical representation of a gear element in Adams View. It defines the number of FE elements per one shell geometry element along involute direction. The input value of 1 means fine, 2 is for normal and 3 for coarse resolution for the shell graphics.

It defines the number of teeth to be created for shell geometry. The purpose of this entry is to define segment of the gear wheel.

 

The Gear AT Mesh will be started and you will see the echo of the input data (contents of the *.opt file and *.ISP file) and the start of the actual meshing as shown in Figure 405. The option 'quiet' suppresses the output to the screen. The *.ISS file contains all information about the geometry of the tooth. If a flexible tooth has been requested, the *.ISS file will be expanded by the op2-reader with results from Nastran.

The file name of the *.ISS file and bulk data file of the gear tooth is composed as *_xxx_yy_zz.ISS and *_xxx_yy_zz.dat where:

The filename of the *.shl file is composed as *_xxx_yy_zz.shl where:

 

Gear AT mesh also reports the results of the curve-fitting as shown in Figure 406; 'difference' shows the distance between the input point and its curve-fitted location. These values should be generally very small. Figure 407 shows the successful termination of the Gear AT Mesh.

 

 

If you requested generation of a flexible tooth, Nastran or ViewFlex will be launched (Figure 399 and Figure 408). Please be reminded, that the CPU-time for Nastran increases with increasing number of contact planes, mesh density and load element size.

 

 

 

The process of Figure 408 proceeds by execution of Gear AT op2-reader; see Figure 409. This processor reads the data stored by Nastran in the *.op2 file and appends retrieved data to the *.ISS file.

 

 

If Nastran computation was not successful, Gear AT op2-reader should issue an information message and indicate unsuccessful termination. Please check the *.f06 file and mesher.log file; there you should find a hint about the cause of the abort by Nastran.

 

The button (on Figure 401) displays the content of the *.ISP file.

 

The button (on Figure 401) opens the Nastran bulk data file in Apex. Please make sure you opt to Keep FE Mesh file in order to preserve Nastran input deck (*.bdf, *.dat) file. Figure 410 shows the example of mesh for a tooth.