A Review on Damage Mechanisms, Models and Calibration Methods under Various Deformation Conditions

Abstract

The development of microdamage under the deformation conditions of high temperature creep, cold metal forming, superplastic forming, and hot metal forming has been reviewed and discussed, and typical constitutive equations developed to model the individual damage mechanisms are summarized. Based on the microstructural analysis of the key damage features for metallic materials under a wide range of deformation conditions, a set of schematic diagrams is designed to illustrate the major types of damage mechanisms. This helps researchers and engineers to understand the major cause of failure of materials under different deformation conditions and to select simple and appropriate mechanism-based damage equations to predict the damage evolution. Further discussions are carried out on the dominant damage mechanisms in hot metal forming conditions and it is concluded that the dominant damage mechanism can be 'grain boundary (creeptype) damage' or 'plasticity-induced (ductile) damage' depending on the material microstructure and deformation rate. In the case of grain boundary damage in hot forming, the shape of microdefects is different from those in high temperature creep and superplastic forming although all of those result in intergranular failure of materials. Furthermore, damage calibration techniques for different conditions of plastic deformation are summarized and discussed.KEY WORDS: damage mechanisms, damage calibrations, creep and viscoplasticity, cold and hot metal forming.

Deformation behaviour of laser-welded tube blank of TA15 Ti-alloy for gas forming at elevated temperature

“…Figure 7(a) shows the microstructure of basal material specimen after failure and the picture was taken near the fracture surfaces. One can see that lots of voids formed in the triple point of grain boundaries, which was considered to be the results from grain boundary sliding (GBS) [14,15]. The deformation mechanisms of SPF were well studied [14], and it was GBS accompanied with dynamic recrystallization (DRV) in our case [12].…”

Experimental and Numerical Studies on the Formability of Materials in Hot Stamping and Cold Die Quenching Processes

“…In these equations, hardening of a material during viscoplastic deformation is modelled according to the accumulation of plastic strains only [6][7][8] .Recently dislocation-based hardening constitutive equations have been developed by Lin et al 9 , where the recovery of dislocations due to annealing and recrystallisation in hot forming conditions is included. Based on the previous work, a new set of unified viscoplastic damage constitutive equations for boron steel and aluminium alloy has been formed and is given below:…”

“…The initiation of localized necking during the deformation process is due to the process of void nucleation and growth, which in turn determines the formability limit in sheet metal that precedes fracture 7 . It is well known that non-metallic inclusions and second phase particles play a fundamental role in the ductile fracture of metal alloys.…”

Micromechanical modelling of nanocrystalline and ultrafine grained metals: A short overview

“…Comparing several damage criteria for ductile materials (critical plastic strain, Rice-Tracey void formation, etc. [110,111]), the demonstrated the dislocation based creep damage model developed by Li and colleagues [112,113] allows describing the damage initiation in nanocrystalline titanium well. Figure 3 shows the damage distribution in the multigrain model of ultrafine grained titanium with precipitates in grains and grain boundaries, obtained using this model [31].…”