NTS News Center

Latest News in Testing, Inspection and Certification

NTS News Center - Latest News in Testing, Inspection and Certification

Coming soon – The “Monster Machine” Massive Wave Simulator

From our underwater shot test quarry facility in Virginia to our 25 foot centrifuge in California, NTS has a tradition of “going big” when it comes to new test equipment. The engineers at our Hunstville, Alabama facility are keeping up with this tradition as they take delivery and work on the installation of their newest equipment, appropriately dubbed “the Monster Machine”.

The Monster Machine is a 20 foot tall, 32 foot wide, 16 foot deep wave simulation machine capable of supporting 30,000 pounds on a 14 foot square test table. Equipment under test will be subjected to 360 degree rotation at 6 RPM! The table can be adjusted to various radii enabling the center of rotation to be matched to the test article over a large range of adjustments. The large test table allows NTS to configure to test article as a package on the ground. Setup, calibration and pre-test is all done prior to lifting the package 12 feet in the air, eliminating physical hazards and making test article changes more efficient and expedient.

Will Roberts PE, Engineering Manager and his team have finished the primary installation and painting, the motor which will operate this machine is being installed now.  Contact the team in Huntsville to discuss this and other test capabilities.

Left to right on the floor: Will Roberts, Engineering Manager, Glenn Kalte, Chief Designer, Jim Birkholz, Senior Engineer-Drive Systems, Domenico Monastero , Senior Mechanical Engineer. On the Platform, Blake Rees – Test Engineer.

What the FOD? Foreign Object Debris Testing at NTS

“As defined in AC 150/5210-24, Foreign Object Debris (FOD) Management, FOD is any object, live or not, located in an inappropriate location in the airport environment that has the capacity to injure airport or air carrier personnel and damage aircraft.” via https://www.faa.gov/airports/airport_safety/fod/

FOD can be a tool left behind, a piece of debris from a plane that recently departed, or a flock of geese. The presence of FOD is a significant concern for the safety of air travel. Airports, Airlines and manufacturers all play a part in the avoidance and minimization of FOD.

Testing systems and materials to determine their ability to withstand FOD is a key part of the development of safe airplanes. NTS conducts FOD testing at a number of our laboratories, including Tinton Falls, NJ.

The video below shows a 0.75 inch steel ball traveling at 187 mph hitting a 0.085 thick aluminum plate. The takeoff speed of the Airbus A340 and the Boeing 747 is 180 mph. The result is the 0.26 inch deep dent in the plate. The 747 outer skin, made out of aluminum alloy, is just 5 millimeters (0.2 inches) thick. Installed between it and the internal panels are soundproof and heat-resistant insulation materials. The wall is 19 centimeters (7.5 inches) thick.

Increasing Vibration Capabilities in Boxborough, MA

The already extensive dynamics testing capabilities at our Boxborough, MA location are about to get even better!

We are eagerly awaiting the arrival of our new Unholtz Dickie T2000 – 3 – PB. This new shaker has a 3 inch stroke and a rating of 25,000 force pounds for sine vibration, 23,000 force pounds for random vibration, and 67,000 force pounds for shock. It has a F2000 Field Power Supply and Heat Exchanger with 2 bays, and series/parallel stators for high SRS shock.

This will be the eighth T2000 for NTS across the US, our other T2000 shakers are in Fullerton and Los Angeles, CA, Chicago and Rockford, IL, Camden, AR and in Plano, TX (above on installation day in 2016).

Contact us today to get your vibration testing scheduled! The schedule will fill up fast! Request a quote here, or contact the Boxborough team today!

New and Upgraded Aerospace Test Capabilities in Santa Clarita

As part of our continual effort of improvement, the Santa Clarita laboratory has just opened a revamped acoustic test facility along with a brand new vibration facility. It features two oversized doors to easily accommodate large test items and staging/prep area with an 8 ton crane.

The upgraded acoustic facility features:

  • 5,000 cubic foot Reverb Chamber
  • 1,400 square foot High Bay
  • Class 100k (ISO Class 8) Clean Room
  • M+P and PAK Closed Loop Control Systems
  • 100+ Instrumentation Channels (Microphones Accelerometers, Force Sensors, Strain Gages)

The new vibration facility features:

  • 2,500 square foot Vibration Facility
  • 15 Ton Crane
  • 2 Ling 340 Shakers 30,000 lbf ea.
  • Class 100k (ISO Class 8) Clean Room
  • Closed Loop Control Systems
  • 100+ Instrumentation Channels

NTS Santa Clarita is one of the largest test facilities in the U.S., covering over 150 acres. Whether you require small component level testing or massive complex system simulation, our mission is to streamline testing, verification and evaluation processes to reduce cycle time and bring your product to market faster.

Our technical experts have extensive experience providing a variety of complex test setups gained from our experience with major aerospace and defense related programs over the last 55+years. Click the here to request a quick quote and let us help you expedite your next project!

Methodology for Transient Thermal Analysis of Machine Gun Barrels Subjected to Burst Firing Schedules

Authors: Ryan Hill and Logan McLeod

This work presents a method for simulating the heating of machine gun barrels during burst firings. The method utilizes a two-dimensional axisymmetric finite element model which solves the highly transient convection input on the bore wall, conduction through the barrel, and convective and radiative cooling on the outside wall. The transient input is derived from a coupling of a lumped-parameter interior ballistics code with a one-dimensional compressible flow model which includes the discharge of the combustion product gas behind the projectile. This transient convective boundary condition can be repeated as desired for arbitrary firing schedules. Finally, an example simulation is performed on a small caliber machine gun and compared with experimental data.

Fill out the form below to download a PDF version of this white paper.

Analysis of Inter-Chamber Energy and Mass Transport in High-Low Pressure Gun Systems

Authors: Ryan Hill and Logan McLeod
Two assumptions are often made by lumped-parameter codes in the analysis of dual-chamber guns: (1) that the gas enters the large chamber at the propellant flame temperature, and (2) that the flow between the chambers is that of an ideal gas. An investigation on the effects of these two assumptions was performed by creating three lumped-parameter codes: one that maintains the two assumptions above, and two that conserve flow energy of the gas instead of maintaining a constant temperature. Of the latter two models, one uses an ideal gas and the other uses a noble-abel gas for the flow calculations. In this work, the noble-abel gas equation of state will be discussed in detail as well as its implications to the gas flow. Then, descriptions of the three approaches to the gas flow model will be presented, followed finally by a comparison of simulation results from the three models.

Fill out the form below to download a PDF version of this white paper.

Modeling of Ordnance-Induced Pyrotechnic Shock Testing

pyro shock plateAuthors: Logan McLeod and Santina Tatum

Design of an ordnance-induced pyrotechnic shock test to meet a specific acceleration based Shock Response Spectrum (SRS) test requirement for a given test article has traditionally been an empirical process. Based on experience, the test engineer will determine a potential test configuration and then, through a trial-and-error process, modify the test parameters and configuration until acceptable SRS levels have been achieved. As a complement to this approach, National Technical Systems (NTS) has developed an explicit finite element based modeling approach to simulate an ordnance-induced pyrotechnic shock test. This tool may be used to assist with test configuration design for particularly challenging test requirements or to streamline the process of arriving at acceptable test levels during the calibration phase of a test program.

While others have recognized the value of modeling ordnance-induced pyrotechnic shock, the majority of these efforts have utilized more traditional linear implicit finite element based approaches. The implicit approach suffers from two major challenges: determining a suitable spatio-temporal force/pressure distribution on the resonating plate induced by the explosive charge detonation; and accounting for non-linear material response such as plastic deformation in the primary resonating plate which commonly occurs during an ordnance-induced pyrotechnic shock event. The explicit approach inherently overcomes both of these challenges.

The NTS-developed explicit finite element modeling approach for ordnance-induced pyrotechnic shock testing will be presented along with model predictions for specific test configurations. Predicted results will include the acceleration-time history and corresponding SRS levels for a given location on the mounting shelf. Test data for these test configurations will be presented for comparison with model predictions. Post-processing of the model results in order to facilitate comparison with measured test data will also be discussed.

Fill out the form below to download a PDF version of this white paper.

Explicit Finite Element Modeling Capability Enables Pyrotechnic Shock Test Design at NTS

For our customers in the space launch industry the requirement to perform pyrotechnic shock testing in the course of qualifying major subsystems and critical components of a space craft or payload is often a daunting prospect. This is due to the uncertainty associated with achieving specified shock levels (expressed in terms of an acceleration based shock response spectrum, or SRS) in traditional ordnance induced tests.

Historically, NTS and its competitors have performed iterative “equalization” tests using mass models of the product to be tested, or non-functional parts, to arrive at a test design that is acceptable to both the testing facility and the customer prior to running the shock test on the hardware to be qualified. This can involve significant expenditure of both test scheduling resources and consumption of test fixture hardware until a test design is agreed upon. There is also the resulting problem of significant over-testing across wide frequency ranges to insure the chances of an under-test are minimized.

Ordnance induced pyrotechnic shock testing is performed using a small explosive charge to impart an intense and very short (microseconds in duration) impulse to a resonating plate. The resonating plate responds to this impulsive load by propagating elastic stress waves (while some localized plastic deformation on the plate beneath the explosive charge does occur) throughout its volume which then reflects off free surfaces creating a very complex three dimensional transient stress field. It is this complex transient stress field that imparts the shock acceleration time history to the shelf or other test fixture structure acting as the interface between the resonating plate and the unit being tested as shown in Figure 1 below.

PyroTesting_Figure1

Figure 1. Response of Pyroshock Test Resonating Plate to Explosive Charge Detonation

For the last couple of years, the engineering services group at NTS Dana Point, CA, in partnership with our test facilities that perform pyrotechnic shock testing, has employed an explicit finite element solver, LS-DYNA, to perform design and analysis of pyrotechnic shock testing for various customers. This approach allows NTS to evaluate a wide range of pyrotechnic shock test fixture design options, explosive charge quantity and placement, in combination with basic mass properties models of the customer’s test article, without consuming any hardware resources.

Recently, this unique capability was recognized by the selection of the NTS paper, “Modeling of Ordnance-Induced Pyrotechnic Shock Testing,” for the Henry Pusey Award (best paper) at the 84th Shock & Vibration Symposium in Atlanta, GA in 2013.  As shown in Figure 2 below, excellent agreement has been achieved between the modeling and simulation results.

Pyro Shock Testing Comparison Model

Figure 2. Comparison of Explicit FEA Predicted SRS with Test Data

Although the commercially available explicit finite element solver, LS-DYNA, is a great resource for performing the required analyses, the key enabler of this capability has been the rapid evolution in computing power at the PC desktop workstation level. For the modeling approach to serve in the role as a functional replacement for performance of iterative equalization testing to evaluate a variety of test fixture design concepts and explosive charge size and placement, the turn-around time for performing each test fixture design iteration using the explicit finite element based modeling approach must be on the scale of 30 minutes or less of wall clock time. Run times on this scale for these models are now routinely achieved at our facility in Dana Point, CA. This approach also allows for a considerably wider range of test fixture design concepts to be evaluated without any risk to the customer furnished test hardware, as the additional cost and schedule associated with fabricating and assembling each test fixture design iteration is absent.

Explicit finite element modeling techniques have traditionally served in the role of weapons design codes for the US DOD and DOE. It is now being recognized that these same techniques have wider application to non-defense industries ranging from automotive and aircraft crash test analysis to safety barrier design and aerospace pyrotechnic shock testing design may now be added to this list.

NTS Dana Point specializes in engineering services to a range of industries in the defense and commercial sectors. More information can be found on the NTS Dana Point webpage, or by calling 949.429.8602.