Experiment # 06
Explain the Universal vibration machine, components and its working with the help of pictures.
Objective:
To study the working principle and behavior of the Universal Vibration Machine (UVM) by:
Observing the generation and transmission of mechanical vibrations through a test specimen.
Measuring the vibration parameters such as frequency, amplitude, and acceleration using sensors.
Understanding the effect of mass, stiffness, and damping on the vibrational response.
Validating theoretical vibration models with experimental data using real-time control and feedback.
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Introduction:
A Universal Vibration Machine (UVM) is a precision electromechanical system designed to
generate controlled mechanical vibrations for experimental, diagnostic, and qualification
purposes. It simulates real-world vibrational environments to study the dynamic response of
materials, components, and systems.
Key Components of the Universal Vibration Machine
A well-designed UVM integrates mechanical and electronic subsystems. Below is a breakdown
of the critical components and their functional synergy.
1. Vibration Platform (Table)
The base or platform on which the test specimen is mounted. It transmits vibration to the device
under test (DUT). Typically made of aluminum or magnesium alloy for high stiffness-to-weight
ratio; may include T-slots or threaded holes for mounting.
2. Motor or Electromagnetic Exciter
Electromagnetic shaker (voice coil or moving coil) – for precise sinusoidal or random
vibrations. Unbalanced motor (rotating mass) – simpler and common in industrial setups
Generates the primary vibrational force by converting electrical energy into mechanical
oscillations.
Input Control: Signal generator feeds a waveform to modulate the vibration frequency (ω) and
amplitude (A).
3. Springs and Dampers (Suspension System)
Isolate the exciter and table from the base and allow for single-degree-of-freedom (SDOF) or
multi-DOF motion.
Types:
o Helical springs or elastomeric mounts
o Viscous dampers or magnetic dampers
4. Control Unit
Modifies input waveform (sinusoidal, triangular, random). Sets excitation parameters (frequency
f, amplitude A, duty cycle). Monitors real-time data and implements safety cut-offs
5. Sensors (e.g., Accelerometers, Displacement Sensors)
Measure vibration parameters such as: Acceleration (a): using piezoelectric accelerometers
Velocity (v): via integration or laser vibrometers Displacement (x): through LVDTs or
capacitive sensors Role in Feedback Loop: These provide data to the controller to maintain
desired vibration characteristics.
6. Mounting Fixtures
Secure test objects in place without influencing vibration behavior Design Criteria: Must ensure
rigid coupling, mass balance, and minimal interference with vibrational modes.
Working Principle
Let’s now dissect the operational mechanics of the UVM.
1. Vibration Generation
Excitation force (F) is generated by: Electromagnetic coil: 𝐹(𝑡) = 𝐵 ⋅ 𝐼(𝑡) ⋅ 𝐿, where B is
magnetic flux, I(t) is current, L is wire length. Unbalanced rotating mass: Periodic centrifugal
force 𝐹(𝑡) = 𝑚 ⋅ 𝑟 ⋅ 𝜔2 ⋅ cos(𝜔𝑡)
2. Vibration Transmission
Force is transmitted through the exciter into the vibration table and into the test specimen. The
table vibrates in sinusoidal, random, or custom waveforms based on system programming.
3. Role of Frequency, Amplitude, and Damping
Frequency (f): Impacts resonance. Important in modal testing.
Amplitude (A): Determines energy transfer. High amplitude → fatigue testing.
Damping (ζ): Influences energy dissipation and response sharpness.
The response 𝑥(𝑡) of the test object is typically modeled using:
¨ ˙
𝑚𝑥 + 𝑐𝑥 + 𝑘𝑥 = 𝐹(𝑡)
4. Feedback and Control Systems
Closed-loop system uses real-time sensor data to:
o Maintain precise output levels
o Adjust driving signal for changing test conditions
o Prevent overloading or resonance beyond safe levels
Advantages and Limitations
Advantages
Precise control over vibration frequency and amplitude
Supports a wide range of vibration profiles (harmonic, random, shock)
Modular and adaptable for different testing standards (e.g., ISO, MIL-STD, ASTM)
Enhances product reliability and safety during design validation
Limitations
High initial cost and maintenance for electromagnetic systems
Requires vibration isolation setup to avoid environmental interference
Complex signal processing and calibration needed for accurate feedback
Potential for nonlinear behavior or fixture influence in high-amplitude scenarios
Conclusion:
The Universal Vibration Machine serves as a cornerstone in mechanical systems testing and
development. By combining dynamic excitation, precise control, and real-time feedback, it
enables engineers to replicate field conditions, verify system robustness, and enhance the
reliability of components ranging from MEMS sensors to automotive suspensions.
Applications
Example 1: Vibration Testing of Automotive Components
Objective: Ensure dashboard assemblies or engine mounts can withstand road-induced
vibrations.
Process: Component is mounted on UVM; excitation simulates real driving vibrations;
fatigue life is assessed.
Example 2: PCB Testing in Electronics
Purpose: To verify that solder joints and microchips remain intact under vibrational
loads during transport.
A random vibration profile derived from ASTM or MIL-STD specs is applied, and
failure modes are recorded.
