ESPEC’s Qualmark brand systems are designed to provide extreme thermal and vibration stresses that will rapidly and effectively expose weaknesses in a product’s design or manufacture. Typically, reliability engineers think of electrodynamic (ED) vibration systems for delivering vibration stress. The stresses and fatigue induced by ED shaker vibration are well understood. However, in highly accelerated life testing (HALT) and highly accelerated stress screening (HASS), repetitive shock (RS) vibration is used.

An RS vibration system consists of a semi-rigid table, mounted on springs, that is driven by the multiple strikes from several pneumatic hammers, or actuators, that are mounted to the underside of the table. When using an ED shaker, the table vibration is the only mechanical stress delivered to the product. The final excitation to the product is the table top vibration, filtered by the fixture and product response. With an RS vibration system, the product is excited not only by the vibration of the table, but also by the shocks transmitted to the product. The shocks cause all components in the product to ring at their own resonant frequencies where fatigue accumulates fastest. These shocks, and the resultant resonant excitation, are what makes RS vibration so effective for rapidly fatiguing product. The shocks produce excitation in all three axes simultaneously, across a wide frequency range. The real-time acceleration response from the product clearly shows high acceleration stresses, with peak accelerations that are much higher than are possible using an ED shaker. However, this complex and random product motion can make it difficult to intuitively understand the effects of the shocks on a product. This video, taken with a high-speed camera, makes the effects of these shocks much clearer, and the information gained by using motion analysis software further deepens the analysis and proves the theory and results behind RS vibration. Watch closely to verify for yourself.

Alas, by using this high-speed video analysis, the dramatically fatiguing nature of the shocks used in Repetitive Shock vibration becomes clear. With every component, board, subassembly and assembly responding at their own resonant frequencies in all three axes, as well as the rotations around those axes, simultaneously, any mechanical defect or weakness in the device will be forced to rapidly fail. By using HALT and HASS with repetitive shock vibration to find these weaknesses and take corrective action, your final product will be more robust and more reliable, resulting in lower warranty costs and delighted customers. Learn how ESPEC can put the power of RS vibration to work for you.