Dog-Bone specimen for Universal Testing Machine (UTM)

This project involved designing and fabricating a Dog-Bone tensile test specimen for use with a Universal Testing Machine (UTM). The design followed industry standards to ensure accurate tensile, elongation, and failure point measurements. Multiple materials were tested to compare performance:

PLA+ (generic brand)
PLA+ from Anker
Special TPU from Smart Materials, intended for use in medical casts.

Project 3D Model

The 3D model was created to precisely meet UTM specimen standard dimensions, ensuring compatibility and reliable results. Features include:

Accurate gauge length and width for consistent strain measurement.
Smooth curvature transitions to reduce stress concentration points outside the gauge section.
Optimized printing orientation to maintain dimensional accuracy and surface quality.

Challenges and Solutions

Challenge 1: Maintaining strict dimensional tolerances during 3D printing.
Solution: Used fine layer height and controlled cooling settings to prevent warping and dimensional drift.

Challenge 2: Material comparison for different mechanical properties.
Solution: Tested three different filament types under identical print parameters and UTM conditions to isolate material behavior differences.

Challenge 3: Printing TPU without deformation or stringing.
Solution: Adjusted extrusion temperature, print speed, and retraction settings to ensure smooth, dimensionally accurate TPU prints suitable for tensile testing.

Final Product

PLA+ specimens: Rigid, high-strength, low flexibility — suitable for structural applications.
PLA+ Anker specimens: Slightly improved surface quality and tensile strength over generic PLA+.
TPU specimens: Highly elastic and flexible, simulating properties required for medical cast applications.
The final series of specimens allowed for direct mechanical performance comparison between rigid and flexible polymers, providing valuable data for material selection in future product development.