# Lattice – static CAD analysis

This project was carried out in the context of the ELISAVA I simulation course. It is a task carried out with my colleague Claudia Hidalgo. The objectives of the project were to make a comparison of static analyses between different geometries using the Lattice tool of the CREO Ptc software, to determine which would be the most efficient one.

In our case, we decided to study which structure would be more efficient to design a mobile cover that would resist an impact. Below are the analyses and results of the geometry that obtained the best results.

Hypothesis 1

The first hypothesis shows a case that usually happens every day. We propose an impact that occurs when a smartphone falls to the floor. To imitate this case, we choose one of the corners where a force is concentrated.

Pre-analysis data

Resulting force = 11,18 N
Restrictions: fixed transfers and free rotations
Material: PLA

Results

a) Von mises stress [MPa]:

At the time of carrying out the analysis, a more efficient distribution of stresses is observed in comparison with the analyses of the previous cases. Even so, we have observed that the maximum stress is 18.41MPa, being this a singularity.

These singularities tend to appear when the analyzed geometry presents sharp edges and the possible solutions are either to modify the geometry (rounding off these edges), or to interpret these stress peaks as errors. In our example, we had to interpret the results, since the lattice tool (in its first version) of CREO ptc did not allow us this modification and its use was a requirement for the project.

As far as the highest stresses located in the impact zone are concerned, they do not reach 10MPa, a fact that allows us to obtain a SF of 2.3.

b) Displacement [mm]

As far as displacement is concerned, we find a maximum of 0.75mm at the point of the impact. In order to understand this displacement we’ve made a sequence of three images
which shows us, first of all, a side view of the workpiece with the represented displacement by using a colour scale. Secondly, we have represented the deformed geometry on a real scale. Finally we observe the deformed geometry using a
scale factor of 10%.

Hypothesis 2

In the approach of the second hypothesis, we analyze a case by three points. In this case, we put a force in the center of the piece and two rectritions in both sides.

Pre-analysis data

Force: Z = 8 N
Restrictions: fixed transfers and free rotations
Material: PLA

Results

c) Von mises stress [MPa]: a distribution of tensions is observed as efficient as in the first hypothesis and the same SF, of 2.3.

d) Displacement [mm]: We observe displacements of 0.5mm, due to the rigidity of the material.