US Government As Represented by the Secretary of the Army

Bridgestone Corporation

Wsl Institute for Snow and Avalanche Research Slf

Martin Schneebeli

Eisuke Seta

Tatsuya Nakai

Jerome B Johnson

Denes Szabo

Henning Loewe

Martin Heggli

Felix Hempel

Matthias Jaggi

Jorg Graupeter

Disclosed is a method for predicting tire performance in which a tire model, which comprises a tread pattern capable of imparting deformation by means of ground contact and/or transfer, and a snow model, in which a snow-covered road surface that comes into contact with the tire model is represented, are used to predict tire performance on the snow-covered road surface on the basis of physical quantities that occur in at least either of the tire model and the snow model. The snow model is modeled as an elasto-plastic body or an elastic body, the nonlinearity of the volume compression property of snow is represented by the relationship between the density or volume strain of the snow and the pressure of the snow, and the shear property of the snow is represented by the relationship between the yield stress of the snow and the pressure of the snow.

Tire performance prediction method and method of designing tire

The snow penetrometer apparatus with data acquisition hardware measure force required to push a small dimension tip member into a snow surface at constant speed that: i) is less than 5 mm in diameter or cross-sectional width, ii) has up to a 90.degree. included angle; iii) has a flared tip and iv) is extended beyond a penetrating head. The penetrometer tip member has a high elastic modulus and is attached through a connecting rod to a stiff penetrating head that is in turn attached to a driving rod. The penetrometer tip member acts through a force sensing transducer. The driving rods are a meter in sectional length that can be joined together for snow penetration up to several meters. The depth of snow penetration is determined by measuring movement of a drive motor or drive rods. The penetrometer tip member is driven downward by a constant speed rotary or linear motor. Two different penetrating head designs are used. The first penetrating head design has a diameter slightly larger than the driving rod to reduce sidewall friction. The second penetrating head design has the same diameter as the driving rod to reduce the volume of influence ahead of the penetrating head. Both heads are low included angle of 30.degree. or less. A measured event of the penetrometer tip encountered force is recorded and correlated with depth of penetration for later analysis to determine its mean value and variation about this mean value to obtain an index measure of inter-grain bonding and snow grain size.

Snow strength penetrometer

Growing community of inventors

Davos Dorf, Switzerland

Martin Schneebeli