Tensile Testing Fixtures

In my 2023 summer internship at Cruise, my main internship project was to conduct tensile strength testing for different assemblies of materials, inserts and screws. For this project, I was to test two different materials, two different inserts and a control tapped hole, two different insert depths, and two different screw lengths. To conduct these tests, I would be using an Intron machine to pull on the assembly until failure. The project consisted of the following phases:

• Test Design

  • First I had to decide how I wanted to run my tests. For each of the configurations I ran 5 tests of each. Each material would be a small cube, with the insert installed into one face, and the screw screwed into the insert. From there, each of these assemblies would need to be help in place, with the screw attached to the intron machine that they could be pulled apart. However, the screws would not easily interface with the head of the intron machine, and some fixture would also be needed to hold the assembly in place. This leads to the next part of my project, designing the tests fixtures.

• Test Fixture Design

  • My first step for designing my test fixtures was to get measurements of all the relevant parts of the machine and start making some sketches. Then, I worked on designing models in CAD and iterated on those designs with feedback from my team until I settled on a final design. Once I had designed my test fixtures I created dimensioned engineering drawings of the test fixtures and sent those to the in house machine shop to have them manufactured for my testing.​

• Test Simulations

  • Once I had designed parts, I decided to run FEA simulations of the parts to know if they were both resilient enough for my tests and to get an idea of how my samples would perform when I run my tests. 

• Running the Tests

  • Once I had all of my test fixtures and I had orderer of all the materials needed for my test samples, I then began to run my tests. I set up each test with the machine and increased until force, recording test data as I went. 

• Data Analysis

  • The machine output all of the test data as csv files, sampling force and displacement every two milliseconds. In each of these files, there were tens of thousands of samples, resulting in an overwhelming amount of data to be analyzed. To speed up this process, I decided to write a python script to automate my data analysis. I imported NumPy to parse the csv files and then wrote code to get the average maximum force for each set of tests for each configurations. 

Below are images of the test fixtures that I designed, the machine that the fixtures were designed for, and some of the test samples.