Page 43 - MetalForming November 2022

Cutting Edge
UE
UNIFORM DEFORMATION (stable flow)
STRAIN HARDENING EXPONENT
(n)
PEd
PE1
Fig. 3—An extensometer can provide a hardening curve until the end of uniform elongation (before diffuse necking); a 2D DIC can provide data until the localized neck; and a 3D DIC can provide the full curve.
and 1122 MPa).
MF
Raw Data Ludwik
Swift
Ghosh Hockett-Sherby Swift/HS Yoshida Median
1000 900 800 700 600 500 400 300 200 100 0
1140
1120
1100
DIC vs. Extensometer, Repetitions = 1
DIC Tests Tensile until Ag Tensile after Ag
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
True Plastic Strain (ɛp) [-]
Model Fits at εp = 1.0
DIFFUSE NECKING
DIFFUSE NECKING (quasi-stable flow)
STRAIN RATE SENSITIVITY
(m)
LOCALIZED NECKING
LOCALIZED NECKING (instable flow)
GEOMETRY OF SPECIMEN
minimum and maximum values are recorded to determine the error margin. Furthermore, the code provides filtered raw data until the end of experimental data—in our case, the beginning of the local neck—and then continues extrapolating with (almost) no interruption.
Fig. 4 shows DP590 tensile-test data with and without DIC. The DIC data then fit in the Table 1 and 2 equations. With the developed method, for DP590 steel, the true stress at 1.0 true plastic strain was estimated at 1112 MPa with an error margin of less than 1 percent (between 1108
True Stress (ơ) [MPa]
True Stress (ơ) [MPa]
Fig. 4—True stress-true strain curves of DP590 with and without DIC (left), with several model fits shown (right) until reaching 1.0 true plastic strain.
NETWORK.
PMA membership provides access to a network of more than 850 member companies. The wide variety of networking opportunities and platforms allow you to make meaningful connections and foster valuable business relationships.
LEARN.
PMA membership allows you to share best practices and learn about emerging industry technologies through PMA’s executive-level conferences, training programs, exclusive plant tours and local district meetings.
LEAD.
PMA actively leads the charge for small and medium-sized manufacturers on policies that strengthen manufacturing in America. Benefit from the association’s lobbying and media-relations efforts in support of pro-manufacturing issues.
Join today at pma.org/membership
40 MetalForming/November 2022 www.metalformingmagazine.com
1080
0.99 0.992 0.994 0.996 0.998 1
True Plastic Strain (ɛp) [-]