UAH

Lab Update - May 2013

Research and Reliability Testing Update:

    This month we have performed some materials testing using our Instron Axial, Tension, and Compression Fatigue Test System and our Satec Axial, Tension, Torsion, and Compression Fatigue Test System. The test subjects were a series of different size padlocks constructed from different material compounds; all were heat hardened boron alloys. The project goal was to determine the amount of force required to cut the shackles on these padlocks. The ASTM Standard ASTM F883-09 was used as a guide and starting point for the Design of Experiment. The outcome analysis for this test was to determine mathematically the force required on a set of lock cutters to cut the locks.

lockcutters

lockcutterFormula

    Using the ASTM F883-09 Standard it was determined that a 3-Point Bending Test would produce the maximum for load, at the center load introduction. As you will see in the following pictures we constructed our test fixtures using tungsten carbide chisels. The tungsten carbide has a hardness value of 9 on the Mohs.

    The Instron 8801 has the ability to supply 100 kN / 22,500 lbf of force to an object. For this test we constructed a test fixture that would hold a carbide tip chisel in each of the grips to act as the cutting head.

instron grips lab news

    For some of the lock shackles, we had to use the Satec Fatigue system, which required a different fixture configuration.

satec lab news

    While in compression mode we were able to use the load cell measurement on the Intron and the Satec to plot the force applied to the lock shackle. We imported the data collected from the Instron and Satec into Microsoft Excel for report generation. This is an example of the type of data we can present from this type of testing.


lock-test graph lab newslocktest table results lab news

    As shown in the figure above we can supply the Mean, Standard Error, Median, Mode, Standard Deviation, Sample Variance, Kurtosis, Skewness, and the Confidence Level. With the results from this test we can now calculate the force required on the lock cutters at the handle to cut the shackle.

    The following is an example of the skills that our team of Engineering staff and students employed on this project:

  • Material Properties studies
    • Understanding the properties of the boron alloy vs. tungsten carbide using the Mohs Scale
  • Fixture Modeling
    • ProE
  • Fixture Design
    • CAD Drawings
    • ProE
  • Fixture Construction
    • Computer Numerical Control (CNC) Milling Machine
  • Reliability Analysis

    During conversations with the customer about project goals, we recommended a Failure Modes, Effects and Criticality Analysis (FMECA). You can purchase the strongest lock available but until a FMECA is conducted to understand the Failure Modes and Mechanisms of the system as a whole, the lock may not be the most critical item in the system. Once a FMECA is conducted a Critical Items List (CIL) can be produced showing which items should be addressed as a Failure Mode or a Failure Mechanism. At that time a ranking system is put into place and the CIL will be the guide.

   

I would welcome you to visit our lab and see our capabilities in person.
Please contact me to schedule a tour of our facility or for assistance with any of your reliability needs.

Mark Gauldin
UAHuntsville Reliability and Failure Analysis Lab Manager

Contact me

(256) 824-2685