Protection Engineering Consultants (PEC) employs experimental testing to verify our designs and to generate high quality data for model creation as well as validation and verification. We typically subcontract the testing to trusted laboratories with whom we have long-running relationships.
Many of our clients are interested in novel materials, that are typically ductile and absorb significant energy before failure. Large strain rates and high temperatures have also been an interest area of most of our customers. PEC works with state-of-the-art material testing laboratories and has developed specialized test equipment for specific projects. We manage the experimental testing process from start to finish — specifying the instrumentation and data processing techniques, analyzing resulting data, and piping these results into our numerical modeling and analytical models.
PEC evaluates components and systems, for static, dynamic, and very high-rate loadings. In these scenarios, we take responsibility for setting the test goals, designing the test frames and connections, defining the loading conditions, writing the test plan, and overseeing the test effort. As many of these are challenging and typically expensive tests, we work closely with our clients to ensure meaningful data and appropriate data is produced.
Test
In many projects that we work on, novel materials are developed and employed for unique purposes. PEC works with a set of trusted laboratories to test these materials under unique loading conditions. We consider complex stress states, large deformations to failure, strain rate effects, temperature, and environmental exposure. Where necessary, we devise our own test fixtures, instrumentation, signal analysis and image processing techniques. Examples of our work in the materials space are listed below.
Materials
In many projects that we work on, novel materials are developed and employed for unique purposes. PEC works with a set of trusted laboratories to test these materials under unique loading conditions. We consider complex stress states, large deformations to failure, strain rate effects, temperature, and environmental exposure. Where necessary, we devise our own test fixtures, instrumentation, signal analysis and image processing techniques. Examples of our work in the materials space are listed below.
PEC designed, modeled, built, and tested aircraft arrestor beds that use granular foam glass aggregates. To predict performance of the arrestor bed, PEC required specific material properties which were obtained in tests designed by PEC and executed by material testing laboratories.
To reduce lower extremity injuries of warfighters in armored vehicles subjected to landmine, energy absorbing mats, foams and crushable glass products are placed on the floor. To model personnel vulnerabilities, constitutive properties for these materials at high load rates are needed. PEC devised a series of tests that were performed by separate material laboratories and extracted the necessary material constants for finite element modeling.
PEC has worked with a San Antonio laboratory to test metals at extremely high strain rates, up to 107 s-1, using laser ablation to create small flyer plates moving at many kilometers per second. Photon Doppler Velocimetry (PDV) sensors were used to measure the motion of the back face of the target material. This data required the development of new signal processing algorithms combined with novel data preparation and form recognition procedures. We are applying these techniques to the testing and analysis of carbon-carbon materials for hypersonic applications.
Components
PEC designs numerous components for protection applications, such as blast-resistant windows, vehicle armor panels, and retrofit devices for blast-loaded buildings. For protective window evaluation, we perform simulated explosive tests at nearby shock tube facilities. For wall retrofits, we have hired testing laboratories to perform full-scale explosive field tests. As protective components must also meet other design requirements, we have performed wind tunnel tests of coil curtains that must resist blast as well as be designed for wind loads; environmental tests are also routinely performed.
A critical component of vehicle armored panels is the connection to the vehicle structure; bolts and welds are typically used but their performance under direct blast and vehicle-transmitted shock was unknown. PEC worked with a local laboratory to perform pendulum impact tests on representative armor panel connections and used the data to develop improved modeling capabilities.
Systems
We have tested systems that include multi-story steel-framed buildings, rail side safety devices, frangible window and wall systems, runway engineering material arrestor systems (EMASs), and live-fire testing of armored wheeled tactical vehicles. These are complicated and expensive tests in terms of the target, instrumentation, load application and data processing/interpretation. Tight and continual coordination between the client, testing laboratory and PEC are used to guarantee the quality of the results and reduce the possibility of data loss.
Visualization, Data Acquisition and Signal Processing
PEC performs basic and applied research related to defense and anti-terrorism. We have developed novel capabilities in several experimental areas to support specialized testing. To determine the equation of state, Hugoniot, and spall strength of metals at extremely high strain rates, PEC has teamed with a testing laboratory to perform flyer plate impact tests. The signals from the Photon Doppler Velocimetry (PDV) gages required that state-of-the-art signal analysis techniques be developed, including Short-Time Fourier Transform, Hilbert Transform, and Short-Time Auto Regression.
Visualization of high speed events provides key information on the physics and mechanics of the phenomena. PEC used high speed cameras to image the size, shape and direction of glass shards created by bullet impact on a ballistic-resistant window. Specialized fragment tracking software was developed and employed, as well as advanced scene setting. This technology was extended to high-speed footage of debris from shock-loaded construction materials in tests to simulate loads from a nuclear weapon detonation. This software was further improved for tracking fragments in arena tests of asymmetric warheads used in hypersonic weapons. New challenges and improvements for this software are currently underway.
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