peteroznewman
Subscriber
nA mesh refinement study should be done before any results are obtained from the model to know that the result value is stable. That means solve the model multiple times with smaller and smaller element sizes in the area of interest and plot maximum stress vs elements size. Changing the element size by a constant factor such as 1.5 is ideal. For example, the initial mesh has elements that are about 1.5 mm thick and wide and there are 4 elements across the width. The table below shows how you could lay out that study. Note that these sizes are for the local area of concern and are not global element sizes. If you are using ANSYS Student and are limited to 32,000 nodes, then you may not be able to do this study.nWithout doing that study, there are indications that the initial mesh is inadequate to study Frictional Stress. The Display Option is Averaged. The maximum is 142.5 MPa.nNow plot the Unaveraged, it shows a maximum nodal value of 209 MPa that is being averaged with a much smaller value from the adjacent element.nPlot the Nodal Difference. The difference is 133 MPa. So the adjacent element was 209-133 = 76. If you average 209 and 76, you get 142.5 MPa. nAs the elements get smaller and smaller, the Nodal Difference will go down and the elements next to each other will have similar values. You can imagine that with large elements, it will be difficult to see small differences due to something like the contact width that is changing with the cam opening angle when there are such large differences in adjacent elements. nWhy do you even care about Frictional Stress? It is smaller than Equivalent Stress, but again, the elements are too large to get an accurate maximum value. With the initial mesh, the value drops to about half over one element thickness. That is too large of a change to have good accuracy in the maximum value.nWith smaller elements, the true maximum stress will be shown below the surface as the Hertz contact theory predicts.nWhat is the goal of your study? What is the problem with the current cam design that needs improvement? What failure modes are of concern?n