Mechanical Shock -DBC test/ Shock Fragility Test
Consumer products usually encounter shocks in two conditions in the lifespan; one is Bumps and Bounces caused by a vehicle on bumpy roads during the transportation, the other is drops caused by human negligence in handling the goods. Hand-held products such as cell phones and PDAs are more vulnerable to dropping impacts when no buffer protection is provided. Automotive electronics work in a much adverse environment than consumer products; especially when they are installed at tires, doors or trunks that sustain to more severe vibrations.
Mechanical Shock Test, which offers prompt verification of structural strength in the product design stage for deciding whether proper buffering is required in the packing design, is one of the crucial items for validating the design.
The following stresses are normally used for performing Damage Boundary Curve Tests:
The 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 lab generates a half-sine wave with low impact velocity by the mechanical impact machine, accompanied by a short impulse time (normally less than 3ms), upon the product.
On completion of the first impact, a thorough inspection takes place on the appearance and functionality of the product. If abnormal is found, a second impact is performed with the identical impulse time and a slightly increased impact velocity. The test goes on in this manner with gradually increased impact velocities until the product is damaged (which gives the critical design velocity ΔVc of the product). In the end, the sustainable impact velocity and the limit height of drop test can be determined for the product in the unpacked condition.
The 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 cost of the packaged product. The unpackaged product is given a low acceleration trapezoid. After one shock, the product is visually inspected and checked for any malfunctions carefully. If there are no defects or malfunctions, then the product is given a slightly higher acceleration shock. This is conducted repeatedly until the product fails to find the product's critical acceleration (ΔAc). This data will be given to package designers to improve the packaging design for its best protection and will be used for reference during the packaged drop test.
Standards: ASTM D3332, DELL Packaging Test Plan- 45785 , HP 398129 X6