<![CDATA[Understanding material dynamic behavior is crucial for designing structures subject to vibration. While static properties are often emphasized in engineering education, dynamic properties such as natural frequency and damping ratio are less frequently measured. This work presents an ultrasonic-sensor-based apparatus for measuring these dynamic properties of cantilever beam specimens. The prototype uses an HC-SR04 ultrasonic time-of-flight sensor and an Arduino microcontroller to record beam vibration. An exponential decay envelope analysis is applied to the displacement time history to determine the damping ratio. A piezoelectric accelerometer provides reference measurements for validation. Experimental tests on aluminum and 3D-printed PLA beams were conducted, and the measured frequencies and calculated damping ratios closely matched analytical and finite-element predictions. Sensor calibration was performed, yielding a correction factor of ~0.887 to improve accuracy. After calibration, frequency errors were below 5%. The apparatus reliably determines natural frequency and damping ratio, offering a simple, low-cost alternative to conventional methods. This system can serve as an effective educational tool for demonstrating vibration measurement and material dynamic behavior.]]>
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