Miner⁺: VHCF Strength Potentials

Motivation

The research objective of the project lies in the development and mathematical description of the scientifically recognized strength potential of variable loads in the range of very high numbers of cycles. This so-called “Miner⁺ phenomenon“ describes a lifetime extension or threshold value increase of variable load amplitudes compared to a single-stage load and thus contradicts the currently widespread Miner rules of damage accumulation. With the help of the project, the current uncertainty about the occurrence and characteristics of the effect is to be reduced and a direct usability of the previously untapped strength potential, especially for steel materials, is to be made possible.
 

Project Goals

As a result of the investigations, a supplement to the calculated strength verification for machine components guideline “Computational strength verification for machine components“ is to be prepared, in which a new calculation algorithm for the utilization of the Miner⁺ effect is described and from which concrete procedural instructions for experimental validation emerge. The planned validation will ensure that the previously unusable strength reserves are utilized while maintaining a conservative component design at all times.

In addition, a recommendation for action is drawn up as a decision-making aid, which describes the conditions under which a Miner⁺ effect is to be expected and the new design method thus leads to improved utilization of the strength potential. This document also contains an explicit description of the possibilities and limitations of the Miner⁺ effect.

This planned integration of the research results into the industrially widespread FKM guideline enables kmU to make direct industrial use of the project results.
 

Focal Points of the Project

• Greater utilization of the strength potential by exploiting material strength reserves while maintaining a conservative component design
• Ensure transferability of the Miner⁺ effect (material, heat treatment condition, surface condition, notch shape number K_t, load)
• Development of a basic understanding of the Miner⁺ effect in terms of material physics and the relationships between material behavior under quasi-static and cyclic loading
• Preparation of a supplement for steel materials of the FKM guideline “Computational strength verification for machine components“ for the verification and use of the strength potential