This paper seeks to build a mathematical model to deduct the twists distribution in the slub‐yarn.
The model, considering the shearing modulus and polar moment of inertia of the yarn, influenced by the yarn density, is established based on the bar torsion model. The twists distribution in the slub‐yarn is concluded based on the analysis of the results. The rules were verified via an indirect method, by testing the breaking strength of the slub‐yarn.
The results of the analysis showed that twists in every section of the slub‐yarn are in inverse proportion to the square of the line density of the corresponding section. Slub length is a key factor to the twist in the base yarn, and the increase of the slub length will increase the twist; while the multiple is the key factor to the slub twist, and the enhancement of the multiple will decrease the twist significantly.
The analysis cannot be verified via a direct method. A new, more conceivable direct method should be utilized to test the result.
The paper builds a base for the research of the mechanical properties of slub‐yarn and gives directions to the slub‐yarn production.
