Computer model calculation
A pick with two tiny cracks (arrows), danger of breakage on the next long ice climbing.
Noticeable crack that was discovered by the owner just before the next ice tour.
Pick fractures do not occur when they are impacted, i. e. not when the pick is set in the ice with a strong impact, not even when it hits rock, nor during the subsequent load of the body weight. Pick fractures occur when releasing the ice tool from the ice.
They are fatigue fractures, as they occur also with crampons. When removing from the ice, flat picks are subject to torsional loads, and semi-circular picks to bending loads which, depending on how extreme the loads are, can lead to overstressing. Over time, it comes to tiny cracks in the tooth base, which slowly become larger and larger with further loads, until it finally comes to a break.
Endangered is always only the area of the tooth base, because in this area is the smallest pick cross-section; a crack cannot originate from the tooth itself. Therefore, the tooth base of all teeth - especially the edges - should be visually checked after each ice tour, especially in the front pick area.
Source: bergundsteigen 4/03
In order to reduce the stress peaks at the critical points, we have developed compensation openings, which serve
for longer life of the pick.
Stress history can be estimated from main stress or "Von Mises stress" using Pro-ENGINEER computer modeling software.
Aim of the investigation:
To determine whether metal stresses are evenly distributed in the test specimen under lateral torsion stress or whether certain areas are particularly stressed.
For a better overview, two identical ice picks are calculated with and without openings.
Bergsport-Steinle 18NOMV5-E icepick for Petzl Nomic / Quark / Ergonomic axes
Ice pick top (17NOMV1-E) is fixed in the solid body.
Force F = 10 kg (in normal cases, very rare side load when ice climbing) is initiated at the pick grip. Stress in the test piece is calculated and displayed as a color scheme.
Test result after a few calculation minutes:
Ice pick completely closed
Ice pick with openings
Stress peaks at the critical points. (Red color representation)
Evaluation of Results:
When calculating the picks, that should serve as a practical example for the introduction in the GSA (Generative Structural Analysis), it was found that the critical stresses are distributed at the several points from the expansion chuck to the tip of the pick.
*The illustrated graphics show the critical stress nodes that does not occur in classic mountaineering