Test Introduction

Our sample will be evaluated in accordance with (IAW) ASTM Standards D618 - 13 (Standard Practice for Conditioning Plastics for Testing), D638-14 (Standard Test Method for Tensile Properties of Plastics), and D5947-18 (Standard Test Methods for Physical Dimensions of Solid Plastics Specimens).

This test is designed to evaluate the characteristics of a given material under tensile loading. To that end, the test involves extending a pre-defined sample at a rate that will cause it to fracture in approximately 3 to 5 minutes. During this elongation, the following data will be collected at each timestep:

• Force applied
• Gage extension
• Gage extension rate
• Crosshead travel
• Time

Required Materials

• 5 - Type V sample, XY orientation, produced using Stratasys ABSplus
• 5 - Type V sample, XZ orientation, produced using Stratasys ABSplus
• 5 - Type V sample, ZX orientation, produced using Stratasys ABSplus
• 1 - Machinist's micrometer caliper with calibrated ratchet or friction thimble

or

• 1- Machinist's micrometer without a ratchet

or

• 1 - Manually operated thickness gauge

or

• 1 - Automatically-operated thickness gauge

Required Facility Conditions

Testing and conditioning will occur at the conditions described below, IAW ASTM D618 and D638:

• Temperature: 23° C
• Relative Humidity: 50% ± 10%

Sample Conditioning

Prior to testing, all samples will be conditioned IAW ASTM D618:

• All samples will be stored in the facility defined above for a minimum of 40 hours.

Sample Measurement

Prior to testing, the thickness and width of each sample must be tested and recorded IAW ASTM D5947 (note that the steps below assume the use of machinist's micrometer caliper with calibrated ratchet or friction thimble):

• Close the micrometer on an area of the sample slightly away from the gage marks, but still within the narrow section of the sample
• Close the micrometer at a rate of approximately 50 µm/s.
• When the ratchet clicks three times, or the friction thimble slips, observe the indicated dimension
• Correct the indicated dimension using the calibration chart defined by ASTM D5947
• Move the specimen to another measurement position
• Repeat all steps above so that each dimension of each sample is measured at least 3 times
• Record the mean of each dimension for use during testing

Testing

Tensile testing will be conducted IAW ASTM D638:

• Load one sample into the upper gripper of the apparatus
• Lock the upper gripper jaws using the attached handwheel
• Secure the bottom end of the sample in the lower gripper using the attached handwheel
• In the testing software, enter the sample orientation, thickness and width
• Select "Begin Test" in the software
• The sample will now be extended at a rate of 1 mm/min until fracture
• Once fractured, the motor will automatically disengage
• Take hold of the lower sample and loosen the jaws of the lower gripper, freeing it
• Take hold of the upper sample and loosen the jaws of the upper gripper, freeing it
• Repeat the steps above for all samples
• Once all testing is complete, select the "Export Data" button in software to collate all datapoints into a single .csv

Machine Evaluation

Final validation of our design will be accomplished through implementation of a testing procedure comprised of three phases:

• subsystem-level validation
• system-level validation
• comparison of representative results to known standard

Phase I: Subsystem-Level Validation

Subsystem-level validation is intended to verify that each subsystem is capable of satisfying its specifications, with a focus on the following specific areas:

• Gripper: elongation under worst-case load, resistance to translation of sample under worst-case load
• Frame: elongation, bending under worst-case load
• Screw: elongation, bending under worst-case load, backlash, susceptibility to backdrive
• Motor / controller: force applied at max required angular velocity, responsiveness & precision of controller
• Sensor suite: resolution and precision of sensing elements

Phase II: System-level Validation

With each subsystem proven functional, we now test the aggregate system to verify adherence to specifications. Specific focus of testing will include:

• Compound system elongation under worst-case load
• Compound system extension rate with worst case sample, test duration
• Travel distance with worst case sample
• Sensor precision when integrated with full system

Phase III: Comparison with Known Standard

With a valid system, we will finally compare our system's performance to a known valid device. Based on required statistical significance, we will print a number of samples in each of the three orientations to be tested. Half of these samples will be tested via the "known" implement, and the other half will be tested via our prototype. All tests will be conducted IAW ASTM D638. Results from each machine will be compared to establish variance from a commercially-proven device. If this variance is within a previously defined acceptable range, our design will be considered finalized. If this variance exceeds allowable standards, we will continue to iterate.