This work describes the thread rolling as a real object and its physical and mathematical modelling. An incremental modelling and numerical solution of the contact problem between movable elastic or rigid tool and elastic/visco-plastic bodies developed in [ is adopted to the numerical simulation of thread rolling process for the case of rigid tool (threading head) and elastic/visco-plastic body (pipe or bar). An update Lagrangian formulation was used to describe nonlinear phenomena on a typical incremental step. For solution of discrete equations of motions and deformations of the object the explicit integration method was applied. The algorithm and application of 3D numerical analysis in ANSYS program were elaborated. This algorithm let for determination of influence of friction coefficient, initial yield stress and plastic hardening modulus. This factors influence will be carried out with 5 levels rotary experiment plan, which let for elaboration of regression equation to describe this relationship. Exemplary results of 3D numerical analysis of displacement and strain in thread for different conditions of rolling process are presented.

The increase of requirements concerning the accuracy of numerical analysis of technological processes with nonlinear contact such as drawing, cutting, embossing, burnishing rolling, thread rolling and machine cutting involves the extension of accuracy in determining workability parameters: initial yield stress σY0, plastic hardening modulus ET and true failure strain φf. Currently, those parameters are often determined in uniaxial tensile testing. Determination of the strain and stress states after the exceedance of ultimate tensile strength of the material, in the moment of stability loss (creation of the neck) constitutes the basic issue. Appearance of characteristic necking disturbs uniform, uniaxial state of stress. In the smallest intersection of the specimen there additionally appear radial stress and circumferential stress - three-dimensional state of stress is obtained. Currently used methods: Birdgman, Davidenkov-Spiridonova or Siebel do not allow calculating the values of those stress precisely enough. The paper concerns the new hybrid method of evaluating stress and strain states in the cylindrical specimen during of tension with the use of Finite Element Method (FEM).

In this study the process of burnishing rolling is considered as a geometrical and physical boundary and initial value problem, with unknown boundary conditions in the contact area. 3D dynamic explicit method for burnishing rolling process with taking into account surface after turning (as previous treatment) under ANSYS/LS-DYNA environment was established. The analysis covered surfaces characterized by vertical angles of the asperities in range: 60°÷150°. The simulation results (i.e. surface deformation, states of strain and stresses, depth of stress deposition) were evaluated. The influence of vertical angle of the asperities after turning process on the states of stress and strain and the depth of its deposition are presented.

No abstract

No abstract