Vibration is the alternating movement of a body around its equilibrium position. These vibrations are useful during vibration testing.
There are other concepts related to vibration:
- The amplitude of a vibration quantifies its level. The amplitude can be expressed as root mean square (RMS), average, peak, or peak-to-peak values. The crest factor is the ratio between the peak value and the RMS value of a signal. For a sinusoidal signal, the crest factor is equal to √2.
- Power Spectral Density (PSD), expressed in g2/Hz, quantifies the power of a random signal within a frequency band. PSD is obtained by calculating the ratio between the square of the RMS acceleration and the frequency bandwidth. PSD is used in vibration testing according to ASTM, ISTA, and ISO standards.
- Harmonics are multiples of the fundamental frequency of a periodic signal.
- An octave is the interval between two frequencies with a ratio of 2.
- The force required for a vibration test is the product of the total moving mass (sample, fixture, etc.) and the required maximum acceleration.
- RMS (Root Mean Square) is the square root of the average of the squared values. It is used to calculate the effective value of a signal. In vibration testing, we refer to G rms.
- Resonance is the maximum response of a system to a constant excitation. Anti-resonance occurs when the system response is at a minimum with constant excitation.
- Velocity is expressed in meters per second or millimeters per second. Vibrational velocity is the derivative of displacement. Acceleration is the derivative of vibrational velocity. Acceleration units are in m/s2 or g (1 g = 9.81 m/s2).
- A periodic signal repeats itself identically, and its values can be predicted in advance. This is the case, for example, with a sinusoidal signal.
- Decibels (dB) are used to evaluate the increase or decrease in the amplitude of a signal based on a logarithmic ratio.
- A subharmonic is a frequency component that is a submultiple of the fundamental frequency of a periodic signal.
In the packaging industry, understanding vibrations is imperative to ensure product protection during transportation and storage. Vibrations can cause direct damage to products or affect the stability and integrity of packaging. Analyzing different types of vibrations, their causes, and effects helps design more resilient and secure packaging solutions.
Types of vibrations in packaging
1. Transient vibrations: These include shocks and impacts experienced during transportation, such as during loading or unloading of goods.
2. Random vibrations: Represent vibrations due to varied road conditions, air turbulence, or maritime movements. They are unpredictable and can vary in amplitude and frequency.
3. Sinusoidal vibrations: Typically generated by rotating or vibrating equipment during transportation. They have specific frequency and amplitude and are more predictable.
Causes of Vibrations
- Transport and handling: The mode of transportation (road, air, maritime) and quality of handling can introduce different levels of vibrations.
- Packaging design: Inadequate design can make packaging more susceptible to the adverse effects of vibrations.
- Environmental conditions: Temperature, humidity, and atmospheric pressure variations can affect the resistance of packaging materials and exacerbate the effects of vibrations.
Effects of vibrations on packaging
- Physical Damage: Breakage, deformations, or deterioration of the product and packaging.
- Label Detachment, Abrasion: Can cause loss of crucial product information.
- Quality Alteration: For sensitive products like electronic components, medical devices, medications, luxury goods, wine and spirits, or food products, vibrations can alter quality.
Vibrations mitigation strategies
- Simulation tests: Conduct vibration tests in the laboratory to simulate transportation conditions and adapt packaging designs accordingly.
- Shock-absorbing and vibration-damping materials: Use packaging materials that can absorb or attenuate vibrations, such as expanded polystyrene or polyurethane foam.
- Structural design: Reinforce packaging structures to withstand vibrations without compromising product protection.
To summarize
Vibrations pose a significant challenge in the design and selection of packaging solutions. By understanding the types of vibrations, their causes, and effects, designers and engineers can develop more robust and secure packaging, thus ensuring better product protection throughout the logistics chain. The key lies in anticipating transportation conditions and strategically using suitable materials and designs to mitigate the adverse effects of vibrations.