Abstract• Additive Manufacturing has the ability to create complex, monolithic

parts with internal geometries• Ability to control porosity to create sacrificial mechanical fuses and

shear pins designed to fail in certain location to protect more expensive parts

• Design of specimen using Materialise Magics and a Renishaw AM250 Selective Laser Melting platform is discussed

• Tensile Test specimen were designed with sections of increased porosity inside the gage length by altering the hatch spacing

• The produced tensile bars are tested on an Instron 5969 which reveals the designed-porosity parts fails consistently at the designed location. Motivation

References and Sources[1] ASTM E8/E8M-15a Standard Test Methods for Tension Testing of Metallic Materials, ASTM International, West Conshohocken, PA, 2015, <http://dx.doi.org/10.1520/E0008_E0008M-15A>[2] Karnati, S. et al. “Investigation of Tensile Properties of Bulk and SLM Fabricated 304L Stainless Steel Using Various Gage Length Specimen”, SFF Symposium, Austin, Texas, 08/08/2016.[3] ©Johnson Manufacturing Company, Inc. <http://www.johnsonmfg.com/temp/Img00150.JPG> [4] © Power Equipment Direct, Inc. <http://www.snowblowersdirect.com/product-images/product_7414_225.jpg> [5] Hodakaguyadv, “How To - KTM 450-530 Won't Start With E-start Problem - Torque Limiter Fix!” <http://ridedualsport.com/forum/index.php?topic=2327.0>[6] Sears Parts Direct, “How to Replace Snow blower Shear Pins” <https://www.youtube.com/watch?v=pXpzUHH6bBM>All other images © Nick Pashos 2016

Experimental Setup

Method of Sectioning Parts in CAD

• Selective Laser Melting (SLM) is an Additive Manufacturing process that uses a laser to melt layers of metal powder into a solid to form parts.

• Research was conducted with the Renishaw AM250 Laser Melting Machine.

• The Renishaw AM 250 uses a laser point exposure scan pattern, where a single point is exposed, the laser is turned off, repositioned, and then the next point is exposed

• User defined process parameters have been optimized to achieve near full density on parts made of 304L Stainless Steel

1) Create CAD model

2) Orient 3) Support

4) Slice and Hatch5) Build

CAD Software Materialise Magics

Build Processor Renishaw AM250

Import

Output

Upload

1) Design part 2) Section part 3) Save “Die” 4) Save “Casting”

5) Import parts to Magics

6) Align Parts 7) Set Parameters

Work Flow for the Renishaw AM250

Process ParametersPower (Watt) 200Exposure Time (µs) 75Point Distance (µm)

60

Hatch Spacing (µm)

85

Creating Localized Porosity• Experimental build contained thee 1inch blocks• Blocks were sectioned in 5mm layers starting from the top• Porosity was created by increasing the hatch spacing from the nominal

85microns (orange sections) to 150 microns (yellow sections)

1 in.

85 micron hatch150micron hatch

Increased porosity

Mechanical Fuse Concept Experiment• Designed an experiment to

determine if porosity can be used to create failure points in parts without changing that geometry

• Tested three different levels of porosity by varying hatch spacing (85, 120, 150µm)

• Tested porosity at three locations in gage length (Top, Middle, Bottom)

ASTM E8 Rectangular Subsize Specimen [1]

Control Sectioned Varied hatch

distance

Results

YS02 (MPa)

YS05 (MPa)

UTS (MPa)

85µm hatch [2]

378.9 380.3 556.0

120µm hatch 364.9 377.7 530.0150µm hatch 328.1 351.1 436.5

Fracture Surfaces of 150µm hatch (left) and 120µm hatch (right)

Averages of 0.2% Offset Yield Strength (YS02), Yield Strength at 0.5% Strain (YS05), and Ultimate Tensile Strength (UTS)

Build Configuration of Tensile Test Specimen, colors indicate hatch

spacing: (nominal) white - 85µm, blue - 150µm, red - 120µm

Detail view of gage length showing locations of

porosity

Sections of porosity

Shear pins

Torque Limiter[3]

Shear pin in snow blower auger [6]

Shear pin [4]

Torque Limiter

Torque Limiter in Motor Bike gearbox [5]

Design Methodology and Experimental Proof of Concept for Additively Manufactured Mechanical Fuses

Nicholas A. Pashos, Patrick M. Sammons, Douglas A. Bristow, Robert G. LandersMechanical and Aerospace Engineering Department, Missouri University of Science and Technology

AcknowledgementsNational Science Foundation, Honeywell, National Security Campus, Dr. Edward Kinzel, Sreekar Karnati, Austin Sutton, Baily Thomas

150µm hatch spacing – Fails at designed location

A B C A B C 120µm hatch spacing – Porosity

not sufficient for fracture propagation

D E F D E F

A B C D E F

1) Import parts to Magics

2) Cut & Punch Sections

3) Set Parameters

Pros and Cons of CAD Slicing Method• Ability to make complex shapes• Tedious to save and import each section• Difficult to achieve correct alignment on build plate

Method of Sectioning Parts in Magics

Pros and Cons of Magics Sectioning Method• Ability to quickly section parts• No need to realign parts• Limited to sectioning parts along XY, YZ, and XZ planes