'Snap_Fit_Design_challenge_2017' simulation project by hur_rehman


#1

I created a new simulation project called 'Snap_Fit_Design_challenge_2017':

Validation of FE model with experimental results Nonlinear high strain loading Challenge is to produce a simulation based tool for snap fit deign. With the help of research material different geometries have been prepared in Onshape and brought in here for analysis. Multiple simulation runs were evaluated to get to the converged results for straight cantilever beams (straight beam cantilever ex 1, 2). Two different cases have been evaluated for the straight cantilever beam like the shape factor analysis. The correct strain level has been achieved in both the situations but there is huge difference in extracting the force value from the simulation this needs to be further analyzed. Similarly U shaped beams (U snap ex 1 non Linear) are also simulated for which 41 percent of error is observed in displacement of end point, this could further be improvised by more different filleting options, they might be having an impact on some strains... over all the simulation is mesh independent as different meshing have been done to see if there is any huge result change, but not observed.


More of my public projects can be found here.


#2

Project Description:

Validation of FE model with experimental results Nonlinear high strain loading Challenge is to produce a simulation based tool for snap fit deign. With the help of research material different geometries have been prepared in Onshape and brought in here for analysis.

Project requirements:

• Validated model of snap joint in simscale with reference material
• Flexibility given in being able to model different geometries
• Non-linear analysis.

Model preparation:

Onshape is a very powerful 3D CAD tool, and it has strong affiliation with simscale too, which makes it a perfect platform to create multiple cad models of the snap joints to be simulated and imported into the simscale.


Figure 1 geometric modeling, parametric modeling strategy has been used

Meshing:

Meshing is the most critical part of the FE analysis, getting a perfect and minimal mesh is the ultimate goal. Different meshing strategies have been used here to mesh our snap joints. Filleted areas have been meshed more finely and overall different meshes have been created to perform mesh independent study for U shaped snaps.


Figure 2 meshing for U shaped beam has been shown as coarse and fine for cantilever beam two different models are shown with mesh refinement at fillets

Simulation parameters:

For cantilever beam snaps a contact analysis has been setup to simulate the snapping effect, physical frictional contact has been established between two sliding parts, with penalty algorithm. It was experimentally determined to raise the penalty coefficient to “1000000000000”. Material model was defined by the young’s modulus as in reference paper with a general plastic poison’s ratio “0.34”.
The locking side has been fixed and beam is moved towards it as distance traveled over time, MUMPS chosen as the solver b/c of the nonlinear problem.

Post Processing:


• For the first example in “snap fit design” the force is coming out to be 76 N while from our simulation its 11.1262 N. the difference is about 14.63 %.
• For the second example in “snap fit design” the strain is coming out to be 0.015, while analytically it was 0.062 the whole difference is about 24.19 %.

POSSIBLE REASONS FOR ERROR

The analytical solution assumes the 100 % load transfer as if the load applying surface is rigid but in finite element analysis here the load is applied by deformable lock which absorbs some of the forces as strain, and also the support of the snap is deformable which takes up some loading, and there are fillets in the FE simulation, while analytically fillets are not considered.

• For the U shaped beam example one, results are found to be 39.94 % of track.

POSSIBLE REASONS FOR ERROR

Again the reason could possibly be the fact that the foundation that we have used in simulation is flexible and is also deflecting so the deflection of the free end is affected by it. Another cause as figures out is fillets in FE simulation.


#3

@bdelatti please have a look.


#4

@hur_rehman please see email


#5

Yup, noticed will do the need full.