While joining tolerances, and therefore forces, are known in the assembly process, the determination of disassembly forces is not possible. This is caused by changes of the product properties during the product operation, which has multiple reasons like thermal or mechanical stress on the product. Regarding the planning of disassembly tasks, disassembly times and tools cannot be planned properly. They have to be determined in the process or stay undefined, which can result in damaging of the product. This article shows an approach to describe the necessary disassembly forces without having to investigate the complex physical influences caused by the usage of the product. A solidifying force that has to be overcome in the disassembly process is defined. To make the solidifying force transferable within the huge amounts of individual products, it is split into a usage factor (e.g. hours of operation) and a product specific factor (e.g. geometry of connection), which specify the influences on the joint properties. The transferability of usage factor to product variants is investigated using a FEM-Simulation.