DBC, Damage Boundary Curve, and can also be called Shock Fragility Test. The purpose is to find the structural strength of the product through mechanical shock test.

In the life cycle of consumer products, there are usually two situations that will be impacted. One is bump and bounce caused by vehicles on bumpy roads during transportation, and the other is product impacted by falling to the ground, when user moves around. For portable products (such as mobile phones, tablet, wearable devices, etc.) , when they are not protected by cushioning materials, the impact of the drop will cause direct and stressful damage to the product. For electronic products installed on the vehicle, it is even more important, since the environment is harsher than general commercial application; especially the product is installed in tires, doors, or trunks and structural strength must be higher. Therefore, during the product design stage, the Shock Fragility Test can be used to quickly verify the structural strength level and determine whether the packaging cushioning design is appropriate.

The following stress is normally used for Damage Boundary Curve validation:
  • Product’s Critical Velocity (ΔVc)
This method is to simulate the end user accidentally dropping the product when it is unpacked. This is usually an instant pulse (ASTM D3332 recommended pulse time <3ms). The product is given a half-sine wave with low impact velocity by the mechanical shock machine, accompanied by a short impulse time (normally less than 3ms). After the first impact, following is inspection on the appearance and functionality of product. If no abnormal is found, a second impact is performed with the identical impulse time and a slightly increased impact velocity step by step until the product is damaged. This damaged point is the critical design velocity(ΔVc) of the product. In the end, the sustainable impact velocity and the maximum height of drop test can be determined for the product with unpacked scenario.

 
  • Product's critical Acceleration (ΔAc)
This test method is to simulate the products subjected to mechanical shocks or free fall drops during transportation, and determine the most acceptable cushion design of the packaged product. The unpackaged product is given a low acceleration trapezoid wave(or square wave). After one shock, the product is visually inspected and checked for any malfunctions carefully. If there is no defect or malfunction, then the product is given a slightly higher acceleration shock step by step until product failure occurs. This testing result is the product's critical acceleration (ΔAc). This data is not only given to package designers to improve the design with its best protection, but also used for package drop test in the design validation stage.

 
<Damage Boundary Curve Concept>


Ref. standards: ASTM D3332, DELL Packaging Test Plan, HP Testing Procedure.
 

 

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