Measuring the hardness of automotive seat bolsters,in a non-destructive way,can be a difficult task.Current methods use small indenters penetrating shallow depths on curved surfaces,resulting in varying results.Hand held devices are quick and easy to use,but results may vary between operators.Also,different techniques used by technicians during the test will impact the results.Automated machine testing can eliminate the variations obtained with hand held devices.Although automated machine testing is repeatable and quite reliable,it can be difficult to set up,requiring proper positioning of the cushion to get consistent readings.Proper indexing and positioning of the cushion is necessary to test the correct spot on the bolster.If the angle at which the indenter contacts the surface of the bolster is not the same each time,the results will not be accurate.Whether a handheld or an automated machine is used,the area of testing is so limited,any imperfection in the surface or underlying structure will result in an incorrect reading of the actual hardness.Increasing the surface area of the test will give more accurate results by lessening the effect of these imperfections.This paper investigates the accuracy of a typical bolster testing method and proposes ways for obtaining accurate results by using different methods to measure the hardness of curved surfaces as is the case with automotive seat bolsters.
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