New ductile fracture criterion for prediction of fracture forming limit diagrams of sheet metals

Modeling of shear ductile fracture considering a changeable cut-off value for stress triaxiality

A macroscopic ductile fracture criterion is proposed based on micro-mechanism analysis of nucleation, growth and shear coalescence of voids from experimental observation of fracture surfaces. The proposed ductile fracture model endows a changeable cut-off value for the stress triaxiality to represent effect of micro-structures, the Lode parameter, temperature, and strain rate on ductility of metals. The proposed model is used to construct fracture loci of AA 2024-T351. The constructed fracture loci are compared with experimental data covering wide stress triaxiality ranging between −0.5 and 1.0. The comparison suggests that the proposed model can provide a satisfactory prediction of ductile fracture for metals from compressive upsetting tests to plane strain tension with slanted fracture surfaces. Moreover, it is expected that the proposed model reasonably describes ductile fracture behavior in high velocity perforation simulation since a reasonable cut-off value for the stress triaxiality is coupled with the proposed ductile fracture criterion.

Prediction of ductile fracture for advanced high strength steel with a new criterion: Experiments and simulation

Extension of a shear-controlled ductile fracture model considering the stress triaxiality and the Lode parameter

Prediction of fracture in hub-hole expanding process using a new ductile fracture criterion

This paper is concerned with hole flangeability of steel sheet, which is evaluated by experiment and finite element analysis with respect to the hole processing condition. The hole flangeability of a material as a forming limit needs to be verified to predict and prevent the undesirable fracture during a flanging process. Hole expanding tests are carried out to identify the effect of hole processing conditions on the hole expanding ratio (HER), which is an indicator of the hole flangeability. Specimens with two different hole conditions are prepared: one is produced with punching process; and the other is reamed after punching to get smoother hole surface. Experimental results show that the facture mechanism and the HER are quite different with respect to the hole conditions. Thorough investigation of those effects is carried out with tensile tests of a specimen with notches. From the experiments, the fracture strain is obtained with different hole conditions and is used to determine the material constants of a new proposed ductile fracture criterion which is applied to finite element analyses of the hole flanging process for prediction of the HER. The experimental results are confirmed and reevaluated by the finite element analysis with the ductile fracture criterion.

Evaluation of Hole Flangeability of Steel Sheet with Respect to the Hole Processing Condition

A cutting apparatus includes: a supply part for supplying an object to be cut; a first cutting part for cutting the object to be cut, provided from the supply part; a carrying part arranged to be consecutive to the first cutting part to carry an intermediate cut object, cut by the first cutting part; and a second cutting part arranged to be consecutive to the carrying part to receive and cut the intermediate cut object from the carrying part, wherein the first and second cutting parts comprise saw blade parts movably and rotatably configured to cut the object to be cut or the intermediate cut object, and the saw blade part has a rotary shaft formed on the upper side of the object to be cut or the intermediate cut object.

Hong-ki Kim

Papers

Prediction of fracture in hub-hole expanding process using a new ductile fracture criterion

Evaluation of Hole Flangeability of Steel Sheet with Respect to the Hole Processing Condition

Cutting apparatus and cutting method