Material characteristics

  • characteristics of the material to be straightened
  • material characteristics
  • material parameters
  • material quality
  • wire characteristics

Mechanical material characteristics describe a process material and largely determine its forming behavior. The modulus of elasticity, elongation or stretching limit, modulus of hardening, carbon content and the parameters of alternating forming used to derive the Bauschinger effect are the most important characteristics in connection with elastic-plastic cold forming.

Material model/material behavior

  • material model/material behavior

With a material model based on mathematical and physical laws it is possible to produce a virtual image of a process material's behavior. Creation and development of the model are accompanied by tests aimed at its verification. A material model can be used, for example, to forecast the stresses arising in the process material in reaction to an applied forming force of a specific magnitude. A material model is essential for the simulation of processes such as the straightening process.

Mechanical model / straightening

  • end-fixed beam
  • mechanical substitute system
  • mechanical model / straightening
  • straightening triangle
  • straightening force

For considerations and calculations concerning the product to be straightened it is an advantage to set up a mechanical model (a level substitute model) of the real straightening process. It is then possible to make (simplified) calculations and predictions.

The definition of straightening refers to three straightening rolls as a straightening triangle. The product to be straightened can be idealized as an end-fixed beam. In addition to the forces applied, bending moments (clamping moments M) are transmitted via both supports. As these forces and moments are not equal to zero, the result is a three-component statically indeterminate system. Mechanical variables are a central force (corresponding to the straightening force), two vertical supporting forces (FV), two horizontal longitudinal forces (FH) and two clamping moments. The product to be straightened bends as the result of the applied straightening force (FR).

Modulus of elasticity

  • elastic characteristics
  • elastic limit
  • elastic straight line
  • Hooke's straight line
  • modulus of elasticity

The modulus of elasticity is a characteristic material parameter determined from the data collected in a tensile test. From the beginning of the tensile up to a specific load, steel deforms elastically, i.e. its length changes proportionally to the load. This proportionality is known as Hooke's law, and in connection with the stress-strain diagram we talk about Hooke's straight line or the elastic straight line. If the load is removed after purely elastic loading of the material or tensile test-piece, the Iatter will readopt its original shape.

The modulus of elasticity varies in size from material to material, but it is also dependent on the material's processing condition and production process. While hot-rolled steels generally have a modulus of elasticity of 210,000 MPa, this value is never reached by drawn wire.

Drawing speeds, cross sectional reductions and other factors have a major impact on the modulus of elasticity of steel wires.