Name: application of design aspects in uniaxial loading machine development
Uploaded: 2018-09-19T14:00:00
Description: Watch this Scientific Journal Video about Application of Design Aspects in Uniaxial Loading Machine Development at JoVE.com

This work was supported by the National Institutes Health NIDCR [DE022664].

NOTE: The finished device is shown in Figure 2. The device enables pure uniaxial testing of specimens in a horizontal position.
1. Component Parts
<ol>
	<li>Prepare two programmable actuators with a 30 mm (1.2 in) travel per actuator capable of spanning 60 mm (2.3 in) when programmed to pull/push together. To accommodate a variety of potential uses, select actuators having a reasonable force capacity [67 N (15 lb)], peak thrust [58 N (13 lb)], speed resolution [...

<ol>
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Standard practice for torque calibration of testing machines Available from: <a target="_blank" href="https://www.astm.org/Standard/standards-and-publications.html">https://www.astm.org/Standard/standards-and-publications.html</a> (2017)</li><li>. ASTM C39 &#8211; Standard test method for compressive strength of cylindrical concrete specimens Available from: <a target="_blank" href="https://www.astm.org/Standard/standards-and-publications.html">https://www.astm.org/Standard/standards-and-publications.html</a> (2018)</li><li>. ASTM A370-17a. Standard test methods and definitions for mechanical testing of steel products Available from: <a target="_blank" href="https://www.astm.org/Standard/standards-and-publications.html">https://www.astm.org/Standard/standards-and-publications.html</a> (2017)</li><li>. ASTM D4761-13. Standard test methods for mechanical properties of lumber and wood-base structural material Available from: <a target="_blank" href="https://www.astm.org/Standard/standards-and-publications.html">https://www.astm.org/Standard/standards-and-publications.html</a> (2013)</li><li>Green, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+cheese,+cheese+analogues+and+protein+gels+in+relation+to+composition+and+microstructure.">Mechanical properties of cheese, cheese analogues and protein gels in relation to composition and microstructure.</a> Food Structure. 5 (1), 169-192 (1986).</li><li>. ASTM D76/D76M-11. Standard specification for tensile testing machines for textiles Available from: <a target="_blank" href="https://www.astm.org/Standard/standards-and-publications.html">https://www.astm.org/Standard/standards-and-publications.html</a> (2011)</li><li>Papini, M., Zdero, R., Schemitsch, E. H., Zalzal, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biomechanics+of+human+femurs+in+axial+and+torsional+loading:+comparison+of+finite+element+analysis,+human+cadaveric+femurs,+and+synthetic+femurs.">The biomechanics of human femurs in axial and torsional loading: comparison of finite element analysis, human cadaveric femurs, and synthetic femurs.</a> Journal of Biomechanical Engineering. 129 (1), 12-19 (2007).</li><li>Poulet, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intermittent+applied+mechanical+loading+induces+subchondral+bone+thickening+that+may+be+intensified+locally+by+contiguous+articular+cartilage+lesions.">Intermittent applied mechanical loading induces subchondral bone thickening that may be intensified locally by contiguous articular cartilage lesions.</a> Osteoarthritis and Cartilage. 23 (6), 940-948 (2015).</li><li>Li, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoblasts+subjected+to+mechanical+strain+inhibit+osteoclastic+differentiation+and+bone+resorption+in+a+co-culture+system.">Osteoblasts subjected to mechanical strain inhibit osteoclastic differentiation and bone resorption in a co-culture system.</a> Annals of Biomedical Engineering. 41 (10), 2056-2066 (2013).</li><li>Huang, A. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptation+of+a+planar+microbiaxial+optomechanical+device+for+the+tubular+biaxial+microstructural+and+macroscopic+characterization+of+small+vascular+tissues.">Adaptation of a planar microbiaxial optomechanical device for the tubular biaxial microstructural and macroscopic characterization of small vascular tissues.</a> Journal of Biomechanical Engineering. 133 (7), 075001 (2011).</li><li>Brown, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Techniques+for+mechanical+stimulation+of+cells+in+vitro:+A+review.">Techniques for mechanical stimulation of cells in vitro: A review.</a> Journal of Biomechanics. 33 (1), 3-14 (2000).</li><li>. Zaber Console software download Available from: <a target="_blank" href="https://www.zaber.com/zaber-software">https://www.zaber.com/zaber-software</a> (2018)</li><li>King, J. D., York, S. L., Saunders, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design,+fabrication+and+characterization+of+a+pure+uniaxial+microloading+system+for+biologic+testing.">Design, fabrication and characterization of a pure uniaxial microloading system for biologic testing.</a> Medical Engineering and Physics. 38 (4), 411-416 (2016).</li><li>Saunders, M. M., Donahue, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+cost-effective+loading+machine+for+biomechanical+evaluation+of+mouse+transgenic+models.">Development of a cost-effective loading machine for biomechanical evaluation of mouse transgenic models.</a> Medical Engineering and Physics. 26 (7), 595-603 (2004).</li></ol>

The goal of this work was to design and fabricate a cost-effective and reliable uniaxial loader for its use with small-scale specimens such as tissue and fibers. A device was constructed that met the requirements set forth while also being flexible enough in design to allow for new attachments to be fabricated as the user needs grow. For example, the device will allow for the testing of dry and wet specimens in a uniaxial or fixed-end configuration.
Critical steps in the design and fabrication...

Mechanical testing has an interesting history that can be traced back to hardness testing equipment developed by Stanley Rockwell in the early in the twentieth century. While technology has grown to the extent that standard, documented practices guide everything from the verification of machine performance to the guidelines for carrying out specific tests1,2,3,4. Today, mechanical tests are conducted on everything from building materials such as concrete, steel, and wood to food and textile products5,6,7,8,9. Given that the fields of biomedical engineering and, more specifically, biomechanics utilize mechanical testing, loading machines are commonplace in biomechanics labs.
Loading machines run the range of scale in biomechanics. As an example, larger loading machines can be used to conduct full-body impact studies or determine human femoral mechanical properties, while smaller loading machines can be used to test murine bones or stimulate cells10,11,12,13,14. Two types of loading machines are found in the testing laboratory; those that are purchased commercially and those that are built by the user. Loading machines developed in-house are often favored for their personalization and customization options15.
In testing, a specimen is secured in the machine so that a displacement can be applied, generating a measurable force. If the load is used as the driving feedback, the test is load-controlled; if the displacement is used as the driving feedback, the test is displacement-controlled. Loading machines, in general, are built upon a frame that connects a mover to a fixed support. As such, testing generally involves one end of the specimen being moved while the other end remains fixed.
Shown in Figure 1 is a sketch of a simple loading machine demonstrating its basic components. Fundamental to all loading machines is a base or frame. Whereas the vast majority of commercial brands utilize a fixed base, the drawing depicts a platform that allows planar (XY) movement. The mover, in this case, is the upper arm that holds a load cell and is driven by a stepper motor. Attached to the frame are the fixtures which hold the specimen and dictate the type of test that is run. Shown in the drawing are three-point bend fixtures. The top fixture (the single contact) is mounted to the moving arm; the bottom fixture (the double contact) is mounted to the stationary base. During testing, the motor drives the upper fixture downward to where the center contact engages the specimen. As the contact engages the specimen, the load cell records the increase in resistance or the force placed upon the specimen.
There are occasions where machines are designed and built in-house to accomplish a motion not attainable with the existing machines in the laboratory. Here we describe in detail one such device. It is a loading platform that enables pure uniaxial specimen loading or equal and opposite motion at both ends. The device incorporates commercial load cells and actuators (movers); a frame is machined to hold the commercial parts and loading fixtures for specimen testing. Understanding the basic principles of testing machine construction can aid in the design of one&#39;s own machine. We have provided the drawing files we created as a starting point to assist researchers with their own machine development. The video will focus on the assembly of the device and the application of mechanical design principles to ensure alignment and reliable testing.

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application of design aspects in uniaxial loading machine development

In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be cost-prohibitive, often priced in the $100,000 - $200,000 price range. At the other extreme are stand-alone manual devices that often lack repeatability and accuracy (e.g., a manual crank device). However, if a single use is indicated, it is over-engineering to design and machine something overly elaborate. Nonetheless, there are occasions where machines are designed and built in-house to accomplish a motion not attainable with the existing machines in the laboratory. Described in detail here is one such device. It is a loading platform that enables pure uniaxial loading. Standard loading machines typically are biaxial in that linear loading occurs along the axis and rotary loading occurs about the axis. During testing with these machines, a load is applied to one end of the specimen while the other end remains fixed. These systems are not capable of conducting pure axial testing in which tension/compression is applied equally to the specimen ends. The platform developed in this paper enables the equal and opposite loading of specimens. While it can be used for compression, here the focus is on its use in pure tensile loading. The device incorporates commercial load cells and actuators (movers) and, as is the case with machines built in-house, a frame is machined to hold the commercial parts and fixtures for testing.

In order to verify the use of the system, actuator speed and performance tests were conducted17. These tests consisted of measuring the actuator speed and distance in comparison to the input values. To verify the sample travel distance accuracy, arbitrary travel distances along the shaft between 254 - 2540 &#181;m (0.01 - 0.10 in) were selected. The device was run to these distances and compared to the actual distance measured using combinations of gauge blocks and...

Watch this Scientific Journal Video about Application of Design Aspects in Uniaxial Loading Machine Development at JoVE.com

Application of Design Aspects in Uniaxial Loading Machine Development

Here we present a protocol to develop a pure uniaxial loading machine. Critical design aspects are employed to ensure accurate and reproducible testing results.

In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be ...

The information in this video is aimed at explaining some of the more important aspects of developing mechanical loading platforms. The information is intended for researchers who may be interested in developing their own platforms, but unfamiliar with some of the basic principles involved. This video is intended to demonstrate the two key features involved in developing a reliable testing platform, specifically, reproducible assembly and disassembly, and accurate alignment.Demonstrating the assembly of the platform will be Mr.Robby Thoerner. Robby Thoerner recently received his undergraduate degree at the University of Akron, from our department of biomedical engineering in the biomechanics track. The goal is to assemble the testing device.Here is an example of an assembled device which has two actuators, load cells, and a frame to support them. Gather the parts to construct the device. Use two programmable actuators, each with 30 millimeters travel, 60 millimeters when working together.Daisy chain the actuators to sync them for equal extension and retraction. Next, prepare two load cells suitable for confined spaces. To support the actuators, prepare one carriage for each of them along with a rail.Create the base from aluminum stock. Cut a piece to the appropriate size and use a mill to machine the plate accordingly to specifications. Machine two side plates according to specifications.The two should mirror one another, and each should have a slot and drilled holes to accommodate the rail. Drill and tap the bottom faces of the side plates. Mount the side plates in the track on the base.Be sure the mount points for the rail are near each other. Fasten the side plates to the base plate from underneath. Next, fasten the rail to the track using its clearance holes and the drilled holes in each side plate.When done, the rail connects the two side plates and carriages slide onto the rail. Move on to work with the mounts for the actuators. Use L-shaped stock to machine a rear mount attachment and a bar to attach to the bottom of the mount.This creates a key for alignment in the track. Screw the bar into the bottom of the mount. At this point, get the selected actuator for the experiment.Attach the rear mount to the body of the actuator using the hole pattern in the actuator. The series of holes in the side plate allow the mount position to be adjusted. Slot the base of the mount to the frame to attach the rear actuator.Use two screws to secure it. Duplicate the steps to mount an actuator on each of the side plates. Get the parts for supporting the front of the actuator.One part is an L-shaped piece with a hole for a tapered connector. On its side is a track to accommodate a plate. The plate for this track also has a track to accommodate fixtures and ensure alignment.Machine an aluminum cylindrical part to connect the load cell and actuator. Machine an aluminum tapered cylindrical part to connect the load cell to the fixture and carriage. Pass the cylinder into the hole of the front actuator mount and use a set screw to anchor the cylinder end.Now, work with the fixtures for the front mounts. For vertical adjustments, machine a central vertical slot in the fixture holder. Attach the actuator front mount to the rectangular side plate, with the vertically aligned holes in its center.Here is the completed assembly for the front mount on one side. Duplicate the steps to mount both the left and the right actuators of the device. These are representative data sets from load testing knotted 25.4 millimeter 2-0 sutures until failure.The gray dash curve represents results from the device described in this protocol, using a loading rate of 0.61 millimeters per second. The black curve represents results from a fixed-end device using a double loading rate, or 1.22 millimeters per second. In all tests, failure occurred at the knot, and measurements showed no statistical difference between the devices.In designing a loading machine, it is always important to design keeping alignment in mind. Focusing on alignment will make sure that your results are reproducible and accurate and that you're testing your specimens appropriately. In this video, we've tried to demonstrate some of the more important aspects of designing loading machines.If you understand some of these basic principles, you can apply them in developing platforms for you own testing needs.

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