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How to simulate an experiment

Experimenter
I have to make an experiment.
on a handlebar at bar-ends, i have to apply fully reversed forces of 270 N at a position 50 mm from the free end each side of the handlebar for 100 000 cycles, with the forces at each end of the handlebar being out of phase with each other and parallel to the axis of handlebar stem
as shown in attached Figure , the maximum test frequency shall be 25 Hz.

The first problem is that i can't decide which solver to choose, the second is how to define the forces in order to change the direction.

thank you

Re: How to simulate an experiment

Siemens Phenom

You can simulate this using a linear statics solution and the durability product in NX. It is assumed that your material properties include all of the required strength and fatigue properties necessary for the durability calculations mentioned below. Here is what I did in NX using the library material AISI_Steel_4340.

1. Define a linear statics solution with loads defined in your first configuration
2. Solve the model and request stress and strain output
3. Create a durability solution process and a durability static event
4. Define a full unit cycle pattern type excitation
1. This is a saw tooth type pattern in which the load goes from zero to max amplitude to zero to negative max amplitude and back to zero for a single cycle
5. Solve the durability event

By default you will get the following output:

1. Fatigue life as number of cycles to failure. It is calculated using Smith Watson Topper
1. Compare this against your 100000 cycles requirement
2. Fatigue safety factor results calculated using Goodman
3. Strength safety factor based upon ultimate stress (UltimateStress/VonMisesStress)

The event has options for fatigue life criterion, safety factors, cyclic stress-strain models, strength criterion (ultimate or yield), and others. The details of your analysis dictate which methods you’d want to use for an event. For example, if your linear statics results exceed the strength criterion anywhere on the model, then there is local plasticity and a strain-life approach with nonlinear strain results would be more appropriate. Alternatively for the same situation you could use the linear static results with a notch correction included. Fatigue safety results only apply to elastically loaded situations.

The NX online help includes several articles related to the durability product, including an overview of what material properties are required for specific calculation methods.

Regards,

Mark

Mark Lamping

Simulation Product Management

Product Engineering Software

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

mark.lamping@siemens.com