G-max Impact Testing
Artificial Turf
Impact Testing
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Gmax,Underfoot Performance, and Head to Surface Impact
Another common misconception is the ASTM F355A Gmax can be used to indicate underfoot performance and field speed of play. Unfortunately this is simply not the case. The pressures applied to the surface and the way the data is analyzed and expressed by the ASTM F355A Gmax device is not sufficient for looking at underfoot performance. Each type (underfoot, head/body, etc) of impact interacts with different system layers making the resulting impact characteristics closely dependent on the "force" of impact. Please see the figure below.
Fortunately, there is a device intended to quantify underfoot performance, the Advanced Artificial Athlete (AAA). This device provides the important underfoot pliability values: force reduction, vertical deformation, and energy restitution. Below is a classic example of how ASTM F33-A does not correlate with underfoot performance .
A minimum G-max should NEVER be specificed
Example of how G-max and Underfoot performance do not correlate
Although the underfoot performance (force reduction, vertical deformation & energy restitution) is similar for Turf A both with and without underlayment, the g-max value is dramatically larger for Turf A without underlayment. Therefore, the underfoot performance and Gmax performance do not correlate.
Example of the results from Gmax testing versus the results of vertical deformation testing on six different surfaces. The results of the Gmax testing do not correlate to the results from the vertical deformation testing,which can be seen by comparing Turf C over stone and Natural Turf. These samples have similar vertical deformations but completly different Gmax results.
Types of impact forms
In the test method F355, the "procedure" (A,D, or E) refers to different impact forms. Each impact form is used to represent different types of impacts that occur, requiring unique and specific test methods for each form. The image below shows three of the impacting forms listed in F355.
Gmax & HIC values from different impact forms do NOT relate to each other. Impact forms and devices can NOT be used interchangeably
Hemispherical "E" headform
In the test method F355, the "procedure" (A,D, or E) refers to different impact forms. Each impact form is used to represent different types of impacts that occur, requiring unique and specific test methods for each form. The image below shows three of the impacting forms listed in F355.
In the test method F355, the "procedure" (A,D, or E) refers to different impact forms. Each impact form is used to represent different types of impacts that occur, requiring unique and specific test methods for each form. The image below shows three of the impacting forms listed in F355.
Natural turf and artificial turf athletic fields for impact safety ONLY.
NOT for.... natural turf and artificial turf athletic field performance
NOT for.... determining turf underfoot stability or surface "speed"
NOT for.... turf in playground areas
HIC? A Colloquialism & unit of measure
In the test method F355, the "procedure" (A,D, or E) refers to different impact forms. Each impact form is used to represent different types of impacts that occur, requiring unique and specific test methods for each form. The image below shows three of the impacting forms listed in F355.
Choosing a testing company
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