Using LabVIEW and PXI to Measure Field Blasts

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"Because of the integration of LabVIEW and the NI PXI-8110 quad-core controller, we efficiently captured millions of synchronized data points."

- Mohammed Alias Yusof, National Defense University Malaysia

The Challenge:
Designing a field blast measurement system to test the response of concrete panels subjected to explosive loading.

The Solution:
Using strain gages, pressure sensors, accelerometers, shockwave probes, NI LabVIEW software, and PXI hardware to record the load data from explosive tests conducted on a concrete structure, and to directly display those measurements.

Author(s):
Mohammed Alias Yusof - National Defense University Malaysia
Norazman Mohamad Nor -
Ariffin Ismail -
Risby Mohd Sohaimi -
Nik Ghazali Nik Daud -
Ng Choy Peng -
Mohd Shazlan Anwar -

Preparing for a Blast Test

We conduct field blast tests on concrete panels to investigate how the materials behave under explosive loading. The preparation for a field blast test involves preparing the test specimens, predicting the explosive load, and validating the experiment. Measuring shock waves, displacement, and strain is important in field blast testing to test concrete’s performance and structural response to various types of explosive blasts. We measure these parameters using a high-speed data acquisition system that includes software, a signal conditioner, sensors, transducers, and cables that are connected to test specimens.

For our experiment, we placed concrete panels in a steel-frame testing rig and suspended explosives near the rig. Figures 1 and 2 show our field blast setup.

Figure 1. Concrete Test Panel

Figure 2. Typical Field Blast Test Setup

We then placed an accelerometer at the center of the concrete slab, facing away from the explosive. The accelerometer can measure shocks of up to 10,000 g to effectively measure the maximum impact felt by the test specimen. We installed another pressure sensor on the mounting rig, facing the explosive, to quantify the maximum pressure at the concrete slab. We also mounted two manganin-type strain gages in the concrete to provide the bending response of the slab during the test. We used manganin-type strain gages to achieve the very short response time required to capture the blast curve. Lastly, we used three blast pressure pencil probes to measure the generated and reflected shock waves from the blast.

Capturing the Data With LabVIEW and PXI

To capture the data from the sensors, we used PXI instrumentation, including a Tetra RPC PXI chassis from Logic Instruments, an NI PXI-8110 embedded controller, and an NI PXI-6133 multifunction DAQ device. We used LabVIEW to program the system and display test results.


We used the Tetra RPC PXI chassis from Logic Instruments because it could withstand the extreme demands of our harsh test environment. The chassis meets the MIL-STD-810E and ensures that all connectors and input/output ports are enclosed and protected. We selected the NI PXI-6133 S Series data acquisition modules because they address our high sampling rate requirements. We connected the modules to an SCXI system to provide the signal conditioning required for the strain gages and ICP sensors. Figure 3 shows the systems. In addition to the modules, we selected our sensors specifically to ensure that they can respond and provide signals within the microseconds range. In order to capture and manage the data and subsequently view and analyze the signals from all seven sensors, we made the most of the NI PXI-8110 controller and its 4 GB of RAM.

We selected LabVIEW for the heart of our system because of its inherent ability to take full advantage of the PXI controller’s quad-core capabilities. Because of the integration of LabVIEW and the NI PXI-8110 quad-core controller, we efficiently captured millions of synchronized data points from both PXI-6133 modules and delegated preprocessing tasks to all four cores.

Prior to displaying all this data, we first saved it into our solid-state SATA hard disk to minimize the possibilities of losing valuable data. Figure 3 shows a screenshot of our program.

Figure 3. NI System and Program Screenshot Used during the Test

We then processed and compared the captured data with other data. Figure 4 shows an example of how the data looks. In addition to comparing the data, we used other postprocessing methods to extract the structural response information of the concrete slab. We performed all these tasks in LabVIEW.

 

Figure 4. Example of the data from pencil probe

Conclusion

Using LabVIEW and PXI instrumentation, we efficiently obtained field blast testing measurement results. Our tests also proved that a high-speed data acquisition system is a useful tool to assess the behavior of concrete panels subjected to explosive loading. Because of this finding, this system will be incorporated into the blast testing program of the National Defense University of Malaysia.

Author Information:
Mohammed Alias Yusof
National Defense University Malaysia
Faculty of Engineering Sungai Besi Military Camp
5700 Kuala Lumpu
Malaysia
Tel: 603 90513400
Fax: 603 90574291
alias @upnm.edu.my

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