

May 27, 2024 at 7:04 pmjavat33489Bbp_participantHi all.I've done a fatigue test and have questions.I model a tungsten carbide drill tip that drills an SPG die, with a ring of solid body around the die for securing. The material of the die and ring is MoraColumba concrete.The units I use are: GPa, mm, ms.The rotation of the drill is set at a speed of rad/ms.I did a short calculation (2 hours), the drill rotated about 30 degrees during this time (the total solution to the problem was 60 hours).I checked the d3plot file. Adequate stress:Next, I decided to do a fatigue analysis to check what it would look like.I got inadequate results:1. The cumulative damage ratio is too high.2. Expected Fatigue Life  too small, the elements will only last 235 seconds under load? But they drill with such a drill for many hours or even the whole day. Tungsten carbide is a very durable material with high density.3. Expected fatigue cycles are generally empty. Why?Help me understand the results, what could I have done wrong?I also apply some basic fatigue tinctures:SN curve for drill:I also got this warning when I increased the starting point in the SN curve, I got the following results:The damage has become less, it is gone, but the lifespan is still short.PS. To reduce calculation time, I increased the density of the die, ring and drill by 4e10, can this make a difference?Please, help. Thank you.

May 28, 2024 at 5:29 pmjavat33489Bbp_participantColleagues.I figured out one question regarding "1. The cumulative damage ratio is too high". The problem was in the material, I specified the compressive strength and removed the tangential modulus, because... it is unknown and the value was tested in detail.But problems 2 and 3 remain:2.Expected Fatigue Life  too small.3.Expected fatigue cycles are generally empty.Why is Expected Fatigue Life so small? Tungsten carbide is a very durable material. Compressive strength 6 GPa. The maximum stress according to calculations (d3plot) is 1 GPa.There are no Expected fatigue cycles at all, why? Am I missing something?Please, help.

May 30, 2024 at 6:58 pmjavat33489Bbp_participant
HELP PLEASE

May 31, 2024 at 6:18 pmjavat33489Bbp_participant

June 3, 2024 at 8:46 pmigandikoAnsys Employee
Hello, how do the element stress results compare to the SN curve? Do the elements showing low fatigue life have higher stresses/high damage ratio?
The expected fatigue life is computed as exposure time (in time domain, it is defined by termination time by *CONTROL_TERMINATION, also see texpo paramter) divided by cumulative damage ratio.
Regarding your question 3, expected fatigue cycles are computed as "expected fatigue life" times “zerocrossing frequency with positive slope”. For d3ftg generated in a time domain fatigue analysis, only cumulative damage ratio and expected fatigue life are provided. There is no “zerocrossing frequency” so no “expected fatigue cycle” is provided.

June 4, 2024 at 4:26 pmjavat33489Bbp_participantHello, how do the element stress results compare to the SN curve? Do the elements showing low fatigue life have higher stresses/high damage ratio? Sir, I have modified and simplified the SN curve for the test in this way, from the tensile strength of the material:Mises stress:*CONTROL_TERMINATION, also see texpo parameter Sir, there is no such parameterRegarding your question 3, expected fatigue cycles are computed as “expected fatigue life” times “zerocrossing frequency with positive slope”. For d3ftg generated in a time domain fatigue analysis, only cumulative damage ratio and expected fatigue life are provided. There is no “zerocrossing frequency” so no “expected fatigue cycle” is provided. I understand sir, there will be no cycles. How then can I check the load, for example, for a task I will drill 10 mm, but I need to check the strength at 1000, how can I scale this? what maps or settings?___PSMaybe I can upload a Kfile here? Can you watch it?



June 3, 2024 at 4:58 pmjavat33489Bbp_participant
HELP PLEASE!

 You must be logged in to reply to this topic.
 Error messages ‘The demanded solver was not found in the specified path’
 CESE Chemistry solver fails in 2D Axisymmetric case
 Problems with fatigue calculations
 Prepost repeated crashing: any advice?
 How start learning LSDyna
 Setting up contacts between an ALE body and a Lagrange body
 Fatigue calculation scaling solution
 A question about quasistatic loading and oscillating response
 Successful explicit analysis
 LSDyna Restart

341

160

130

107

99
© 2024 Copyright ANSYS, Inc. All rights reserved.