Tech Briefs
Direct Femap Interface to ADINA — the 3Dbolt
In ADINA the 3Dbolt element is available for accurate modeling of bolts. A bolt is modeled by 3D solid elements with the options of boltforce or boltshortening as specified in a table. Contact can also be modeled on the boundaries of the 3Dbolt.
In this Brief, we demonstrate the use of the Direct Femap Interface to ADINA to perform a nonlinear static analysis of a bracket with a bolt, modeled with 3D elements, followed by a restart to a frequency analysis.
Figure 1 shows the geometry of the bracket assemblage. The upper and lower brackets are held together by a bolt and nut.
Figure 1 Bracket assemblage analyzed
In the finite element model, we use tetrahedral solid elements with an elastic material model for the whole bracket assemblage. Initially, the two parts of the bracket are bolted together by a 2000 N bolt tension force. A pressure load of 1 MPa is then applied to the top of the upper bracket as shown in Figure 2. Figure 3 shows the connections (contact surfaces) defined between the bolt, the lower bracket and the upper bracket.
Figure 2 Finite element model of bracket assemblage
Figure 3 Connections in bracket assemblage
Using the ADINA 3Dbolt element, users can specify various modeling options as shown in Figure 4. In Figure 5, we show how the 3Dbolt plane and bolt loading sequence is defined.
Figure 4 Defining the 3Dbolt element in TRANSOR for Femap
(a) 
(b) 

Figure 5 Defining (a) the 3Dbolt plane and (b) bolt loading sequence in TRANSOR for Femap 
Figure 6 shows the effect of the bolt pretension and applied pressure with a band plot of the von Mises stress.
Figure 6 Deformation of bracket assemblage showing von Mises stress
Subsequent to the above static analysis, a frequency analysis is performed in the deformed configuration corresponding to the bolt load, applied pressure and contact conditions. The first mode shape with a band plot of the total displacement is depicted in the movie above.
The entire analysis, from preprocessing to postprocessing, is performed within the Femap environment using the direct Femap interface to ADINA. Thus, users already familiar with Femap can use the advanced capabilities of ADINA easily and effectively.
Keywords:
Femap, Nastran, preprocessor, postprocessor, bolt, contact, frequency analysis, CAD, CAE