Vibration and its Damaging Effects?

In layman’s terms; vibration testing is the shaking of a product or package to determine its ability to survive in real world conditions. Technically, Vibration refers to mechanical oscillations about an equilibrium or center point. The oscillations may be periodic such as the motion of a pendulum, or random such as the movement of a tire over a highway or an aircraft on the runway at takeoff.  In the testing world, we deal with random vibrations; as in the movement of lading in trucks over the road or in aircraft.

Vibration is present in all modes of transportation.  All products are subjected to vibration during shipment.  It is not feasible to completely eliminate the sources of vibration in the transportation environment.  Consequently, it is necessary to design products and packaging to withstand those vibration sources.  The forcing frequencies or sources of vibration are passed on by the wheels of the moving vehicle, the structure and drive train, and the suspension system.  These frequencies vary depending on continuing changes in surface condition, grade, joints in concrete and rails, and from other similar recurring discontinuities in road beds.  Vibration affects all items.  This includes individual components in a product, the product itself, the product combined with packaging, and packages stacked together to form unitized loads.

Typical failure modes due to vibration include contact damage, breakage or abrasion to components, abrasion of sterile barrier systems, and fatigue damage.  Contact damage results when a component of the product yields enough to strike another component resulting in either breakage of the yielding component; breakage of the struck component or abrading or chipping of either component.  Critical damage to the sterile barrier system results when packages constantly rub against one another inside the shelf box or shipping container and cause cause breakage in the materials.  Fatigue damage occurs when the constant yielding such as bending of flexible materials, leads to cumulative damage over time. The end result is the creation of pinholes in the material causing a loss of sterile integrity for the product.  Vibration also frequently causes cosmetic damage to packages and products, rendering a product unacceptable and unsalable. The nebulous aspect of vibration is that most of the damage caused by vibration forces is not known to have occurred until the product is delivered and about to be used for its intended use.