Learning Forum

[AndreaAyala]

Hello dear community!

I need a little help, I modeled a simplified system of two tires joined by an axle. I used a joint translational and a force applied to the axle to move the system.

Initially when the entire system and base were made of steel, the wheels turned and displaced. However when I changed the materials like elastomer sample (defined by Ansys) for the wheel surface, aluminum for the padding and axle, and concrete for the base, the wheels were slipping but no longer turning.

• I used frictional contact with a friction coefficient of 0.8 between the base and the tires
• Frictionless contact between the padding and the axle
• For the area between the padding and the tire I used the share topology in the Space Claim

I need the wheels to roll and turn, I have tried to change the friction parameters but cannot find the problem.

Thanks in advance

[AdrianGZ]

n

[peteroznewman]

nOn the frictional contacts that are Near Open, change the Interface Treatment to Adjust to Touch.n

[AndreaAyala]

Hi Peter,nI made the change but tires are slipping and not spinningnn

[AndreaAyala]

nCan you help me please?nI don't know what else is failing in my modeln

[peteroznewman]

nI have a long list of changes to your model, but I first want to know what is the purpose of the model? What question will this model answer? Why have you chosen Transient Structural?nThe reason the tire doesn't turn is because there is zero normal force between the tire and the base.n

[AndreaAyala]

nThe self weight of the system doesn´t act as a normal force?nThe model is a simplification of a wheelchair, first I am working with a flat surface but the goal is to make the system move on a ramp and then I will calibrate it using the attached article for the angles of 2.7 ° and 7.1 ° (the weight of the system according to the article must be approx 100kg)nI have tried to move the system with a force on the axle to test but in reality I need them to be tangential forces that are applied to the wheels such as the magnitudes highlighted in the article.nThe reason for using Transient Structural is that there is a push and rest time, in the first step set 0.48 seconds and in the second 0.59 seconds for example and then repeat that setting.nThe way to calibrate the system will be obtaining a constant speed of 1.17m / s because that was the speed that was used for article essays. Once it is calibrated, the objective is to obtain stress results for different slopes by parameterizing the angle of the ramp.nThose are the details but for now I need to get the system to move and the wheels turn across the surface using a force, for now as a test in my model I am using aluminum and other materials that make it heavier with 200kg so it needs more tangential force, about 50N considering the 0 ° slope.nI would appreciate it very much if you could help menn

[AndreaAyala]

nThe self weight of the system doesn´t act as a normal force?nThe model is a simplification of a wheelchair, first I am working with a flat surface but the goal is to make the system move on a ramp and then I will calibrate it using the attached article for the angles of 2.7 ° and 7.1 ° (the weight of the system according to the article must be approx 100kg)nI have tried to move the system with a force on the axle to test but in reality I need them to be tangential forces that are applied to the wheels such as the magnitudes highlighted in the article.nThe reason for using Transient Structural is that there is a push and rest time, in the first step set 0.48 seconds and in the second 0.59 seconds for example and then repeat that setting.nThe way to calibrate the system will be obtaining a constant speed of 1.17m / s because that was the speed that was used for article essays. Once it is calibrated, the objective is to obtain stress results for different slopes by parameterizing the angle of the ramp.nThose are the details but for now I need to get the system to move and the wheels turn across the surface using a force, for now as a test in my model I am using aluminum and other materials that make it heavier with 200kg so it needs more tangential force, about 50N considering the 0 ° slope.nI would appreciate it very much if you could help menn

[peteroznewman]

nThe self weight of the parts can act as a normal force, but that is not in the model. You have to add the Inertial load called Standard Earth Gravity to the model. nIf you add gravity to this model, it won't help because the Translational Joint Ground to Axle would support the weight instead of the tires pressing on the base.nOne way to fix that is to replace the Fixed Support on the base with a Translational Joint to Ground with the Joint axis in the Y direction. You could apply a Joint Load of 9800 N upward to simulate 100 kg subject to gravity, without actually adding gravity to the model.nHow much do the parts minus the base weigh? You should add a Point Mass to the system to reach 100 kg. You will need that mass to prevent very large accelerations from developing from the applied force.nWhat is adjusted to get the system to a constant speed of 1.17 m/s?nWhy does the speed affect the stress in the tire?nWhere are the Total and Tangential Force being measured? Maybe a diagram would help.nWhat is the Contact Angle? Maybe you could attach the article or a link to the article. This site allows zip files to be attached.n

[peteroznewman]

nI'm wondering what is the purpose of the channel in the tire?nI typed an extra zero on the weight of 100 kg acting on the base. That should be 980 N.n