COF Testing Machine of Frictional Forces

Coefficient of friction, the ratio of your frictional force resisting the motion of two surfaces to get in touch with towards the regular force pressing the two surfaces with each other.

The coefficient of friction has distinctive values for static friction and kinetic friction. In static friction, the frictional force resists force that may be applied to an object, as well as the object remains at rest till the force of static friction is overcome. In kinetic friction, the frictional force resists the motion of an object. For the case of a brick sliding on a clean wooden table, the coefficient of kinetic friction is about 0.5, which implies that a force equal to half the weight on the bricks is expected simply to overcome friction in maintaining the bricks moving along at a continuous speed, as well as the coefficient of static friction is about 0.6. The frictional force itself is directed oppositely towards the motion of the object.

Measuring the coefficient of friction

You'll find two forms of machines that may measure static COF -- permanent laboratory models and transportable field models which can be generally known as pull meters.

Probably the most typical process of measuring slip resistance utilizes a 50-pound weight placed flat on a Neolite shoe heel, that is then placed flat around the stone surface becoming tested. The heel-and-weight assembly is pulled across the stone having a spring or electronic scale. The maximum level of force (pounds) necessary to begin the assembly in motion is recorded. This measurement is divided by the weight (50 pounds) and yields the coefficient of friction worth.

Measurement of Slip Resistance

Tests to measure slip resistance had been created mainly for man-made supplies, together with the earliest in the 1940s, when Sidney James carried out experiments to price floor polishes along with other floor upkeep chemical compounds for Underwriters Laboratories. From these experiments came the COF testing machine James Machine (ASTM D-2047) as well as the 0.five static coefficient of friction because of the threshold of security for standard ambulation. In contrast to other test solutions, the James Machine can only be applied within a laboratory for testing smooth, dry surfaces, and test benefits can't be when compared with these of other test strategies.

The two most typical tests for measuring the static coefficient of friction are the COF testing machine C-1028 and D-2047. The solutions and final results of those two tests are extremely distinct and can't be compared. D-2047 makes use of the James Machine inside a controlled laboratory atmosphere that measures on dry, smooth surfaces and can't be employed within the field on current flooring surfaces. Due to the consistency in the testing process of your James Machine, it can be deemed to supply one of the most precise and trustworthy measurements of SCOF for smooth, dry surfaces. The COF testing machine C-1028 is really a transportable field test process that makes use of a horizontal pull meter. It might be utilized on wet or dry too as smooth or textured flooring surfaces. Due to the environmental variables related to tests utilizing transportable pull meters, the outcomes are inconsistent from the surface to surface, along with the reliability is low.

You'll find transportable slip meters in the marketplace which claim to measure the static COF. When buying slip meters, be certain they comply with all the ASTM needs for the applicable test process.