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Product Modifications: Changing the Stress Load

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Product Modifications: Changing the Stress Load

On the Scene E-Newsletter, Edition 157, April 3, 2012

skateboard 000005584385Every day, as consumers, we are bombarded with advertising trying to sell end users products and services to help make our lives easier or to enhance an existing product to add additional features and services.  Sometimes though when end users try to install or apply these accessories, the modifications can make these products potentially unsafe or in a use that was not intended in the design.  Take for example a designer metal plate that attaches to a skateboard body for aesthetic qualities but the end user attaches the plate by drilling a few holes through the body of the skateboard.  From a design aspect, the modification could have disastrous results.

Products using materials have what is called a “stress load”.  A stress load is the amount of load or weight that the material can withstand in the design of a product.  For example, step ladders have a weight capacity and warn consumers of not using the top step as the stress load on the material cannot support this weight.  Stress loads are also applicable to building products where trusses and other structural materials can sometimes be modified to where the weight of the snow on the house can make the structure collapse.

In the skateboard example, the user is riding down a steep hill and gaining speed and the user performs a trick by jumping two feet in the air and lands back on the body of the skateboard and the skateboard collapses causing severe injury to the rider.  After the accident, the question becomes:  Did the modification of the product cause a lower stress load for failure and was the action of the rider an unintended use?

This is where CED can help shed some light on the contributory factors for the failure.  The CED engineers would first look at the design of the skateboard and the application of the modification.  Were the directions followed?  Were there adequate warnings?  Was the use of the rider prior to the accident a usual application?  All of these would set the basis for product failure analysis but the real examination would come from the CED Materials Science group.

CED’s Materials Science group has a background in all sorts of materials from wood to composites, metal, glass, steel and many other materials.  The CED Materials Science group would first examine the skateboard under our high powered microscope and other precise equipment to determine if the product failure was from a defect in the material, fatigue or a stress load.  If the determination was a stress load; the Materials Science group along with other CED engineers would then test an exemplar using the same modifications and stress loads to see if in fact the modification was the contributing factor.

Product modifications can make products more useful and customized, but they can also contribute to an accident whether the accident involves a bicycle, vehicle, house, consumer products or other products.  CED has experience and education in determining failure with modified products and can be a great asset. To find out more about how CED engineers follow the evidence and perform forensic engineering, call 800.780.4221 today to speak with an engineer about your case or claim.

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