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Surface Force Pressure

A tire tread exerts force on the surface of the road. As a result Surface Force Pressure is present between the surface of the road and the tread. The amount of this pressure depends upon the weight of the truck or automobile, the number of axels and tires, tire inflation pressure, tire tread design, and the material and surface characteristics of the road.

The surface force pressure can be measured and mapped using Fujifilm Prescale, Pressure Indicating Film. Fujifilm Prescale is a Mylar-based film that contains a layer of tiny microcapsules. The application of force upon the film causes the microcapsules to rupture, producing an instantaneous and permanent high-resolution topographical image of pressure variation across the contact area.

Simply place Fujifilm Prescale between any two surfaces that touch, mate or impact. Then, apply pressure and remove it. Immediately, the film reveals the distribution of surface force pressure between the two surfaces. Conceptually similar to Litmus paper, the color intensity of Fujifilm Prescale is directly proportional to the amount of pressure applied to it.

Figure 1 shows the surface force pressure impression of a tire tread on Fujifilm Prescale film. The darker red areas indicate higher surface force pressure, and the white areas indicate the absence of pressure. Engineers can discern the precise pressure distribution by comparing the results to a color correlation chart shown in Figure 2.

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Fig 1: Surface Force Pressure Impression of Tire Tread on Fujifilm Prescale Film

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Fig 2: Fujifilm Prescale Color Correlation Chart

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Fig 3: Surface Force Pressure Impression after Topaq Analysis

Sensor Products provides an additional, resource to customers needing statistical data and enhanced digital visuals of their Fujifilm Prescale films. This service is called Topaq, which is an imaging analysis system that can be bought or leased. The staff at Sensor Products also will perform the imaging on an as-needed basis. Topaq consists of a calibrated, densitometric scanner and user-friendly Windows-based software. Figure 3 shows the results of a Topaq analysis on the impression in Figure 1.

First, the Fujifilm Prescale image was scanned into a PC. Then, the Topaq software interpreted the stress marks on the film to render high-resolution, color images of the surface force pressure. Topaq also provides a wealth of statistical information in easy-to-read formats. A single keystroke generates a histogram report that reveals the statistical distribution of pressure levels throughout the image. Furthermore, histograms can be produced for any user-defined region of interest. Typical screenshots from the Topaq software are shown in Figure 4.

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Fig 4: Typical Screenshots from the Topaq Software