Material characterization, constitutive modeling and validation in hot stretch bending of Ti–6Al–4V profile

Abstract

Ti–6Al–4V, as one of the most frequently used titanium alloy in aerospace applications, is characterized by its excellent mechanical and corrosion properties. However, it is well known that Ti–6Al–4V is difficult to be formed at room temperature. Therefore, hot stretch bending has been used to improve formability and reduce springback in forming Ti–6Al–4V profile. In the virtual development of designing suitable hot stretch bending processes for Ti–6Al–4V, numerical simulations are considered desirable. However, the reliability of numerical simulations depends on the models and methods used as well as the accuracy of material data. In this work, a set of uniaxial tension tests was performed on Ti–6Al–4V at the temperatures ranging from 923 to 1023 K and strain rate from 0.005 to 0.05 s−1. Moreover, a set of stress relaxation tests was conducted on Ti–6Al–4V at the temperature range between 773 and 973 K and pre-stretch elongation ranging from 0.7% to 10%. The Johnson–Cook and Arrhenius models were used to characterize the uniaxial tension and the stress relaxation behavior, respectively. Finite element model of hot stretch bending was created according to the laboratorial experiment setup in ABAQUS based on the constitutive models calculated above. The finite element simulation indicates that the residual stress in the profile decreases greatly in the secondary stage of hot stretch bending due to the stress relaxation behavior. The predicted springback shows promising agreement with the corresponding experimental observations.

Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets

“…The rate of the force decrease, i.e., the stress decrease with time during the stress relaxation tests depends on the temperature, time, and initial loading, i.e., strain level. The influence of the temperature and time on the rate of stress relaxation is greater than the strain level, which was also concluded by Deng et al [11]. Finding the global minima, a unique solution to an optimization problem such as in the inverse modelling procedure to identify the stress relaxation model parameters, is a difficult task.…”

“…Although numerous studies have been performed to understand and model the mechanical behavior of Ti-6Al-4V at different temperatures and strain rates, e.g., [7][8][9][10][11][12][13], and several studies related to hot forming of titanium alloys exists [14][15][16][17][18][19][20][21][22][23][24], further knowledge and understanding of the material behavior under hot forming conditions is essential to the exploration and success of industrial implementation of hot forming technologies in the future. In the design of new manufacturing techniques and competitive forming procedures for fabricated titanium sub-structures, a crucial task is obtaining reliable numerical predictions using the finite element method (FEM).…”

Numerical Simulation and Process Optimization on Hot Twist-Stretch Straightening of Ti-6Al-4V Alloy Profile

“…The stress was significantly reduced and homogenized after creep forming. Deng et al [15,16] established the constitutive modeling of OT4 and Ti-6Al-4V alloy, then created the hot stretch bending and creep forming FE model of the L profile. The stress distribution and deformation springback of the profile were predicted and verified.…”

Influence of movement tracks on the forming quality of profiles fabricated by flexible stretch bending of multi-point roller dies technology

“…Muranaka et al 12 proposed a new ''rubber-assisted stretch bending method'' for uniform bending of profiles with a constant radius of curvature. Deng et al 13 studied the material characterization and constitutive model of titanium alloy in uniaxial tension and stress relaxation. A heatable stretch-bending process was proposed to improve the forming stability of titanium alloy profiles and reduce springback.…”