286
Y. Yuan et al.
Among them, the tensile time of the sample without pre-defect is much longer than
that of the pre-made defect sample, and the tensile time of the preset round notch
sample is longer than the preset V-shaped notch sample.
It can be clearly seen from the load-time relationship diagram that the tensile
process of sample without pre-defects is divided into four stages: elastic deformation
stage, yield stage, plastic deformation and fracture stage. The duration of the tensile
process of the sample without pre-defects is 3000 s, and the plastic deformation stage,
which is a “smooth line” in the figure, lasts for nearly 2600 s and the maximum force
is 1.11 kN; The tensile process of the sample with the preset round notch is also
the same that divided into four stages. The duration of the whole tensile process is
600 s, the maximum force is 1.11 kN, and the plastic deformation stage is relatively
short. For the sample with preset V-shaped notch, the elastic stage and yield stage are
obvious, the plastic deformation stage is very short, the maximum force is 0.49 kN,
the duration of the tensile process is 120 s.
It can also be seen from Fig. 24.8 that during the tensile process, all three samples
occurr plastic deformation. The entire parallel section of sample A occurs plastic
deformation, and sample B occurs plastic deformation at the round notch section 8
× 17 × 2.2 mm only, and the sample C occurs only at the V joint which is 2 × 2 ×
2.2 mm.
The mechanical properties of the samples are shown in Table 24.3. Yield strength
refers to the maximum stress value of the material. Due to the different cross-sectional
areas of the three samples, the V-shaped notch sample is the smallest, the round notch
sample is the second, and the sample without pre-defect is the largest, resulting in
the opposite relationship of yield strength. It can be seen from Fig. 24.8 and Table
24.3 that the yield strength of the sample with preset defects becomes larger, and the
elongation and elongation rate become smaller.
Fig. 24.8 Three broken
samples
Table 24.3 The mechanical properties of the samples
Sample type
Elongation/mm Elongation rate/% Yield strength/MPa
Sample without pre-defects (A)
165
55
253
Preset round notch sample (B)
24
8
3710
Preset V-shaped notch sample (C) 12
4
55,682
Y. Yuan et al.
Among them, the tensile time of the sample without pre-defect is much longer than
that of the pre-made defect sample, and the tensile time of the preset round notch
sample is longer than the preset V-shaped notch sample.
It can be clearly seen from the load-time relationship diagram that the tensile
process of sample without pre-defects is divided into four stages: elastic deformation
stage, yield stage, plastic deformation and fracture stage. The duration of the tensile
process of the sample without pre-defects is 3000 s, and the plastic deformation stage,
which is a “smooth line” in the figure, lasts for nearly 2600 s and the maximum force
is 1.11 kN; The tensile process of the sample with the preset round notch is also
the same that divided into four stages. The duration of the whole tensile process is
600 s, the maximum force is 1.11 kN, and the plastic deformation stage is relatively
short. For the sample with preset V-shaped notch, the elastic stage and yield stage are
obvious, the plastic deformation stage is very short, the maximum force is 0.49 kN,
the duration of the tensile process is 120 s.
It can also be seen from Fig. 24.8 that during the tensile process, all three samples
occurr plastic deformation. The entire parallel section of sample A occurs plastic
deformation, and sample B occurs plastic deformation at the round notch section 8
× 17 × 2.2 mm only, and the sample C occurs only at the V joint which is 2 × 2 ×
2.2 mm.
The mechanical properties of the samples are shown in Table 24.3. Yield strength
refers to the maximum stress value of the material. Due to the different cross-sectional
areas of the three samples, the V-shaped notch sample is the smallest, the round notch
sample is the second, and the sample without pre-defect is the largest, resulting in
the opposite relationship of yield strength. It can be seen from Fig. 24.8 and Table
24.3 that the yield strength of the sample with preset defects becomes larger, and the
elongation and elongation rate become smaller.
Fig. 24.8 Three broken
samples
Table 24.3 The mechanical properties of the samples
Sample type
Elongation/mm Elongation rate/% Yield strength/MPa
Sample without pre-defects (A)
165
55
253
Preset round notch sample (B)
24
8
3710
Preset V-shaped notch sample (C) 12
4
55,682