Northrop Grumman Shock
Air Strike is a desktop mechanical shock test apparatus capable of delivering controlled, repeatable, mechanical shocks of up to 4500 g’s to a 6" x 9" printed circuit board. Air Strike delivers a shock to the circuit board along three perpendicular axes, and only requires one user to operate. The main purpose of Air Strike is to assist engineers at Northrop Grumman in testing the durability of their circuit boards in a time-efficient manner. This test apparatus is a self-calibrating system that decreases testing time from months to less than an hour, and this is possible due to its exciting ability to self-calibrate. The LabVIEW program controlling the apparatus receives an input from the accelerometers on the circuit board after an initial shock, and adjusts the air pressure accordingly which varies the shock level in the following test.
The biggest initial obstacle of this project was designing an apparatus that delivers a shock, and not an impact. During an impact test, an external object strikes the test object or the resting surface the test object is attached to. This is essentially the opposite of a shock test, during which the test object is accelerated into an external object like a wall, which is more difficult to design. However, distinguishing between these two is critical because delivering an impact creates "ringing" in the plate that is difficult to control and read peak acceleration values, while delivering a shock yields a clean, repeatable half sine wave.
Another challenge this project presented stems from the heavy reliance on electrical control, both to deliver the shock and to provide a fast and reliable method of calibration. Many of the key components of Air Strike are controlled by a LabVIEW program, and the software for these components must all be compatible. As a team of mechanical engineers with limited experience implementing electronic components, this challenge provided a great opportunity for growth in knowledge and competence in an integral component for nearly every mechanical engineering project.
Air Strike was designed and manufactured to decrease the amount of time required to obtain the required data for a circuit board, and to increase the safety of the process. The current testing method at Northrop Grumman involves a large pendulum that strikes a plate that the circuit board is attached to. This requires one person to drop the pendulum, and another person to catch the pendulum weight so that the circuit board is not impacted twice. This clearly introduces many issues with safety to the operators, with the reliability of the calibration, and the time required for the whole process. Air Strike uses a LabVIEW controlled calibration system that eliminates the need for the operator to carry this out, which increases reliability and drastically decreases the time to obtain a data point. Air Strike is also encased in a compact, secured outer housing, which completely removes the operator from interacting with any moving parts. This is especially important with the metal-on-metal collisions and high forces generated by the presence of up to 4500 g's.
This innovative shock test apparatus incorporates complex electronics with innovative LabVIEW programming and high-performing mechanical components to deliver an innovative, effective, efficient, and safe solution to a real problem in industry.