Newsletter Artikel

Preview FEMFAT 5.3

During the course of the successive expansion of the range of functions in SPECTRAL, the exceptionally well-proven notch stress concept in the time domain has been successfully applied to the frequency domain.

The greatest challenge in doing so was posed by the definition of a suitable equivalent stress PSD. The known methods in the time domain (e.g. DIN 15018, BS7608, …) are naturally based on parameters which are largely time dependent (notch factors). Starting with the calculation of the damage over the degree of utilization in the time domain, it was possible to develop an equivalent calculation method in the frequency domain in the context of an internal research project. Consequently, as of FEMFAT 5.3, the base material and the
welds can be analyzed in SPECTRAL during one and the same calculation run – which clearly underscores and further enhances the leading position of SPECTRAL in the area of
frequency-based fatigue analysis.

Figure 1: Weld für SPECTRAL - weld Definition

Figure 2: Weld for SPECTRAL - weld results


SPOT database
The new FEMFAT version also provides numerous improvements for SPOT. Most notable here is certainly the switch to the new, more flexible SPOT database. The first thing you notice is that the previous SPOT database has been replaced by an xml file. It now allows flexible definition of FEMFAT spot connections, e.g. the use of different types of connections
(spot welds, rivets) and equivalent stresses in one and the same calculation run or separate material assignments for each sheet of a connection, etc. Moreover, especially for the analysis of bolt connections, nugget elements with a total of three rows can be created (Remesher or ANSA) and analyzed.

Figure 3: Spot Weld

Flexible definition of the S/N curve slope
A customer wish that was expressed repeatedly in the past concerned the user-defined specification of the S/N curve slope k2 after the inclination point. Consequently, we are especially pleased to be able to meet this request by and large with FEMFAT 5.3. Starting with the slope k1 in the finite-life domain, the slope after the inclination point is calculated by
k2=a*k1+b. When doing so, a and b are user-presettable constants with the well-known default values of a=2 and b=-1 for “Miner modified.”

Further FEMFAT features

  • MAX: new, improved cutting plane filter
  • Indicator for the local mesh quality
    • element search
    • highlighting of welds
    • improved weld definition
  • Analysis of adhesive connections
  • Node-averaged stresses from MEDINA can be imported
  • The range of dispersion can be specified separately for boundary layer models
  • ALTAIR H3D: a tabular format is supported
  • Piecewise definition of the support number in dependence on the relative stress gradient
  • ADVC interface: effective immediately, the solver (which is especially widespread in Japan) is now supported