GMW 14909 Radial Fatigue Test of Wheels

In the GMW 14909 standard, developed by General Motors, a test method is defined to determine the fatigue strength of passenger car and light truck wheels when subjected to radial fatigue loads.

GMW 14909 Radial Fatigue Test of Wheels

The purpose of radial fatigue testing is to find out the structural properties of wheels that are normally used on roads in passenger cars, light trucks and utility vehicles. In order for a wheel to pass the test, it must be subjected to a certain number of repeated radial loads.

The fatigue life of a wheel subjected to repetitive loads is calculated based on the stress values obtained from the static analysis. The accuracy of stress values depends on various parameters, such as tire modeling, simulation methods, load application, etc.

The vertical stiffness of the tire plays a crucial role in the radial test as the tire transfers the load from the drive drum to the wheel. Tire vertical spring rate testing is generally performed in accordance with the SAE J2704 standard developed by the Society of Automotive Engineers (SAE J2704 Tire Normal Force/Deflection and Total Footprint Size Test). Adjust the tire material properties to fit the vertical hardness test curve. Radial fatigue testing is simulated under static conditions using an approved tire model (SAE J328 Wheels - Performance Requirements and Test Procedures for Passenger Cars and Light Trucks) in accordance with the SAE J328 standard. It gives you the confidence to get simulated stress values close to the measurements of your laboratory strain gauges to estimate wheel life.

The tires are designed and manufactured to fit standard rims, and when fitted to the correct rims, the tires perform at the desired level. Needless to say, if the tire is mounted on an unsuitable rim, the life of the tire will be shortened. Essentially, wheels must pass three tests before they can go into production: a turning fatigue test, a radial fatigue test, and an impact test. In simple terms, the radial fatigue test is to find out the number of cycles in which the wheel fails.

 Test equipment

ISO 18164 Passenger car truck, bus and motorcycle tyres — Methods of measuring rolling resistance

Wheel Radial Load Fatigue Testing Machines (UT1015)

5.1 Drum specifications
5.1.1 Diameter
The test dynamometer shall have a cylindrical flywheel (drum)
 with a diameter of at least 1,5 m (reference drum diameter: 1,7 m) for passenger car and motorcycle
tyres;
 with a diameter of at least 1,7 m for truck/bus tyres.
It should be noted that the results are different for different diameters; see 9.3 for drum diameter correction for
comparisons, if necessary.
NOTE Historically, the measurement of the fore and aft (longitudinal) force on a flat surface machine has been shown
to be quite difficult since this force is very small relative to other forces being measured. If a flat surface machine is used,
care should be taken to correlate the data with the reference drum diameter in order to assure accurate results.
5.1.2 Surface
The surface of the drum shall be smooth steel or textured and shall be kept clean. For the textured drum
surface, see B.4.
5.1.3 Width
The width of the drum test surface shall exceed the width of the test tyre tread.
5.2 Test rim
The tyre shall be mounted on a test rim, as specified in Annex C.
5.3 Load, alignment, control and instrumentation accuracies
Measurement of these pa