Examples using winLIFE

Automotive

A lot of winLIFE-users come from the automotive industry. The following typical applications are:

Driveline

Clutches, torque-converters, retarders, housings of gearboxes, shafts, planetary gears, and torsional springs for passenger cars, trucks and agricultural vehicles. Measurements on real tracks have been done to take into account real conditions. A race track in Germany, the famous “Nürburgring” was measured in detail and fatigue predictions were done for the driveline. The measured Torque versus load for a Mercedes S500 with a 7 speed automatic gear is shown in the figure.

7-speed automatic gear box of Daimler AG
Dwelling time of the output torque versus speed of for an s-speed automatic gearbox on the race track Nürburgring
Distribution of the stress amplitudes and S-N curve of a gear wheel compared between computer simulation and test rig (DV-Steuerung, WV-Steuerung)

Suspension

winLIFE is used for the design and test of military vehicles. Suspensions, axles, springs are calculated. Measurements on different road types are used to determine the specific input loading from the road.  A comparison between damage on the vehicle, test rig results and simulation showed a good correlation.

military vehicle Fennek, which was calculated with winLIFE
Rim including forces coming from the tire
wheel and the fatigue analysed hub
results of calculation of Fennek on different road types and missions

Plane Applications

The moving of airplanes at an airport is more efficient if pulling trucks are used. The truck is mounted to the front landing gear and the question arose whether there might be a problem in fatigue life. 

On the front landing gear strain gauges were applied and the strain during the truck pulling at the airport and during the landing was measured.

A fatigue life analysis was done and a comparison between landing and truck pulling showed under which conditions the system can be used. 

Plane that was used for measurement
Landing gear with strain gauges

As a result the fatigue life for the landing procedure and truck pulling could be calculated and a relation between the load cases could be found.

Wind Turbines

We have to prove that the life of a wind turbine has a fatigue life of 20 years. Measured load histories are used, each representing a time section of 10 minutes. The measured load sizes are the generator moment and the deformation of the machine foundation. Furthermore, the pre-stressing of the bolts including the contact and non-linearity and the bending moment resulting from the weight of the machinery itself were taken into account. 

The fatigue life calculation is carried out using the stress results of the static Finite Element Analysis standard load cases which have been gauged by scaling with the measured loads using the results of the standard load cases. Stress S-N curves according to the guidelines set by Germanischer Lloyd were generated and used.

The following two figures show the life-results from winLIFE and FEMAP calculations for a planet carrier. The rules of the Germanischer Lloyd were followed for these calculations.

Planet carrier of an Off-Shore wind turbine (left FEA-model), right: fatigue life results calculated with 122 load scenarios which were scaled to a life of 20 years

 

The following figure shows results for a gearbox-housing from Zollern Company, which was calculated with ANSYS and winLIFE (damage is shown).

Housing of a gearbox for a wind turbine with fatigue life results calculated with winLIFE using an ANSYS-FEA-model

Seam Welding calculation

Hot-Spot Search (Example from Ship Construction)

An important characteristic of this process is that for welded sheet metal, which has been modelled with plate elements, the elements can be found automatically at the plate joins which is where the welds usually are. For the fatigue life calculation we use the element stresses projected perpendicularly to the weld toe notch. Since only one element is used for the fatigue life prediction, the increased stress in the weld notch is only recorded to a limited degree of reality and the quality of the prediction is therefore not as good as with a structure stress concept. The critical points of a structure can be found, however, using this method. If required, the hot spots found can then be re-calculated to increase the quality of the prediction. This procedure enables the user to investigate huge structures with hundreds or more weldings in a short calculation time.

non-deformed structure without load
Loaded structure including deformation
Results of a fatigue calculation according to the hot spot concept
results of a fatigue calculation according to the structural concept

Notch Stress Concept R1 (Lorry trailer axle)

Trailer axle using elastic notch stress concept (r1)

This example shows the interaction between FEMAP and winLIFE. The welded joints of a complex component, a rear axle, are calculated with the r1-concept.

It is shown the entire modelling and the use of sub-structures. The load results from three measured load-time-functions. There are three unit load cases in direction of the wheel-forces calculated in FEMAP and transferred to winLIFE. The results of the fatigue life calculation are returned to FEMAP and then displayed.

overall view of the calculated shaft of Kögel Company
results of damage in the welding
Tools for analysis of fatigue calculation in winLIFE

Trailer hitch using structure stress concept

For the ball head trailer hitch shown here, weld seams are to be calculated according to the structure stress concept. In this example we only take into account the left hand fillet weld between the U-profile and the angle profile (see figure below).

Geometry of the trailer hitch

 

The model consists mainly of tetrahedron elements. The areas of the weld seam to be examined are meshed with hexahedron elements. For the structure stress concept with linear extrapolation, we keep to the defined distances between the node-rows of the fillet weld, as shown by the nodes in the diagram marked in yellow.

The distance of node line 1 is 0.4 x the thickness of the steel of the weld seam and the distance of node line 2 is 1 x the thickness of the steel of the weld seam. With the steel thickness of the rectangle profile at 7.1mm, node line 1 is therefore 2.84mm and the node line 2 accordingly 7.1mm away from the fillet weld.

Node line at the fillet weld for the structure stress concept

 

Two load cases have an effect on the ball head: These are first of all shown separately. In the following winLIFE fatigue life calculation the two load cases are acting simultaneously.

The ends of the U-Profile are fixed in the area of the drillings.

Load case No.

Type of Load

Load

1

Side load

 

Pull force  in y-direction   Fy = 20000 N

2

Vertical- und Horizontal load

Pull force  in x-direction   Fx = 21700 N

and

pushing force  in z-direction von  Fz = -12000

 

Trailer Hitch affected by a side load (Load case no. 1)
Trailer Hitch affected by vertical and horizontal loads (Load case no. 2)

 

The fatigue life of the complete ball head trailer hitch is now to be analysed in a simple way.  To do this, steel in its basic state is used for the whole model, including the weldings.

The result is the damage sum, the equivalent amplitude and the degree of utilization as shown in the following diagrams. As you can see, the geometry of the weld seam is enough to cause an increase in damage in the corner area between the U-profile and the rectangle profile. As already mentioned, with these results for the whole structure, the decrease in the strength of the material in the welds has not been taken into consideration. 

Damage Sum whole Model
Equivalent Amplitude

 

The degree of utilisation is shown in the following diagram. A degree of utilisation of 0.178 means a 17.8%- usage of the endurance limit.

Degree of Utilisation of the Fillet Weld

combinded Multi Body / FEA simulation of a Digger arm

To investigate fatigue life of a digger arm a multi body simulation was done using Recurdyn. The result of the time dependend stresses were imported from Recurdyn into wnLIFE for fatigue analysis.

Digger with meshed arm for simulation

 

For each node of the structure a stress time history is got and the number of repetations until crack initiation was calculated. Variations of the acceleration showed the influence of the service conditins.

Equivalent stress history for the most damaged node.

Universities

Many universities use winLIFE for their courses. A special university edition is available to meet the demand for a greater number of installations. winLIFE is simple to use and it has the functionality necessary to demonstrate fatigue behaviour in high level lectures.

Simple to use does not mean that you do not need an understanding of the theory. But winLIFE is a well-documented tool that enables the user to understand what he is doing and we presume that our users want to understand what they are doing.  To be successful in fatigue prediction you need an extensive understanding of the theory and a student can learn this using winLIFE.

The university version includes a full, unlimited version including all tools and one hardlock for the professor. He can use winLIFE on his own laptop with the hardlock. A floating license is included enabling 10 students to use the winLIFE BASIC version. This student version is slightly limited but quite sufficient for academic use.

interactive simulation of stress and strain. Load step, resulting stress strain path and damage are shown in one picture and can be added interactively by the user. In this way Masing and memory are demonstrated and can be checked.
Animation of Neuber`s rule. Starting point, resulting stress and strain and the hyperbola are animated by moving the mouse. Different types of Neuber modifications can be shown. This helps to understand the effects.
to understand stress and strain state Mohr’s circle can be shown for each time step. A deep understanding and analysis of the problem is possible.
yielding model according to Mrosz