Date of Award


Degree Type

Capstone Project

First Advisor

Bahram Nassersharif


The main focus of the design was to create a variable force mechanical stabber and slasher for Dr. Nassersharif for testing material sample developed by Team 20 and other departments at the University of Rhode Island (URI). The table was designed to deliver impact energies ranging from 0 to 165 Joules (J). The variable force is created through compressing a spring mechanically and measuring the velocity at impact on a test specimen. The spring propels a cart on a track system to constrain the movement of the attack in a specific direction. The system uses software to determine the initial compression based on user inputted impact energy. Velocity and acceleration data is acquired and read by the software to determine the kinetic energy and impact force. Testing of the system was performed and the results analyzed to determine future work and improvements.

Desmark/Amerisewn is a local company that is based in Cranston, Rhode Island and manufactures protective clothing for law enforcement, correctional officers, and mental health professionals. Those industries require workers to wear protective clothing that must be certified through the National Institute of Justice (NIJ). Non-balistic protective clothing is certified through professionally through the NIJ for impact energies ranging from 24 J to 65 J.

The current design achieves several design specifications such as a spring being able to achieve 40000 cycle before failure while the goal was 5000 cycles. The spring can also deliver impacts that achieve the NIJ tests standards. Another main requirement was obtaining impact kinetic energies that could achieve exceed the maximum NIJ test by 2.5 times. The robustness of the spring means that it is not compressed its full length in order to do so. The machine can also simulate a slash with a self centering swivel vice that has the angle of attack adjusted simply if the tester desires. Additionally, a linear relationship between the spring compression and release velocity was established for testing.


Sponsor: Deskmark Industries/Amerisewn