ENERGY OF CRACK NUCLEATION AND PROPAGATION IN CHARPY

Drop-weight impact testing machine Schematic of logging data on specimen loading in impact three-point

Standard Charpy specimen a b A typical P(t) plot for steel 45 in the

1) a 2) b A typical P(t) plot for steel 45 in the ductile-brittle

b a P(t) plots for steel St. 3 at the loading rate of 4.

Estimation of the crack propagation velocity - V Estimation of crack length - L

$Velocity of brittle fracture propagation for different steels: 1 – St. 3 (■), 2$

$Temperature dependences of the total deformation and fracture energy at different rates of deformation$

$а b Temperature dependences of the crack nucleation energy Ei (▼) , ductile fracture$

$Temperature dependences of the total fracture energy Et(▲) and of partial energies of crack$

Conclusions ü An experimental technique was developed and Charpy impact tests of steels with

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ENERGY OF CRACK NUCLEATION AND PROPAGATION IN CHARPY SPECIMENS DEPENDING ON THE TEST TEMPERATURE AND LOADING RATE E. A. Kondriakov and V. V. Kharchenko G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

Drop-weight impact testing machine Schematic of logging data on specimen loading in impact three-point bend tests G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

Standard Charpy specimen a b A typical P(t) plot for steel 45 in the ductile-brittle transition region at V 0 =2 m/s, T = 20°C (a) and the signal variation during the brittle crack jump using a time scale magnification (b). G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

1) a 2) b A typical P(t) plot for steel 45 in the ductile-brittle transition region at V 0 =2 m/s, T = 20°C (a) and the signal variation during the brittle crack jump using a time scale magnification (b). G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

b a P(t) plots for steel St. 3 at the loading rate of 4. 4 (a) and 1 m/s (b): (1) T = -5°C; (2) T = 20°C; (3) T = 30°C; (4) T = 40°С; (5) T = 50°; (6) T = -20°C; (7) T = 0°C; (8) T = 10°C; (9) T = 20°C; (10) T = 55°C. a b P(t) plots for steel 15 Kh 2 NMFA at the loading rate of 4. 4 (a) and 5 m/s (b): (1)T = 20°C; (2) T = -11°C; (3) T = 0°C; (4) T = 10°С; (5) T = 35°; (6) T = 50°C; (7) T=100°C. G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

Estimation of the crack propagation velocity - V Estimation of crack length - L Estimation of fracture time - t zone of ductile crack propagation а) zone of brittle crack jump zone of ductile fracture b) zone of brittle crack jump c) Macroview of fracture surfaces for steel 45: a) – T=20°C, b) – T=0°C, c) – T=-50°C. G. S. Pisarenko Institute for Problems of Strength V = L/t http: //www. ipp. kiev. ua

$Velocity of brittle fracture propagation for different steels: 1 – St. 3 (■), 2$

Velocity of brittle fracture propagation for different steels: 1 – St. 3 (■), 2 – steel 45 (●), 3 – steel 15 Kh 2 NMFA (▲). G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

$Temperature dependences of the total deformation and fracture energy at different rates of deformation$

Temperature dependences of the total deformation and fracture energy at different rates of deformation of Charpy specimens from steel 45: (1) V 0 =4. 4 m/s; (2) V 0 =2 m/s. Variation in the total fracture energy of steel 45 with the loading rate at = 10°C (1) and -20°C (2). G. S. Pisarenko Institute for Problems of Strength T http: //www. ipp. kiev. ua

$а b Temperature dependences of the crack nucleation energy Ei (▼) , ductile fracture$

а b Temperature dependences of the crack nucleation energy Ei (▼) , ductile fracture energy Ed (●), brittle fracture energy Eb (■ ) , and total energy of deformation and fracture Et (▲) at V 0 =2 m/s (a) and V 0 = 4. 4 m/s (b) for steel 45. G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

$Temperature dependences of the total fracture energy Et(▲) and of partial energies of crack$

Temperature dependences of the total fracture energy Et(▲) and of partial energies of crack nucleation Ei (▼), ductile fracture Ed (●) and brittle fracture Eb (■) for steel 15 Kh 2 NMFA. ь A high sensitivity of the digital signal recording system has enable to evaluate the values of brittle fracture energy. ь As follows from these diagrams the most part of the energy is spent for ductile fracture, whereas the energy spent for brittle fracture is small. Meanwhile the brittle energy practically has no changes with the temperature change. ь The values of brittle energy are about 2 J, whereas the values of ductile fracture come up to 150 J. ь The behavior of total energy of deformation and fracture and its components is similar for various steels. G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua

Conclusions ü An experimental technique was developed and Charpy impact tests of steels with use of instrumented drop weight impact tester were carried out ü The Charpy impact tests performed using an instrumented vertical impact testing machine have enabled us to obtain the temperature dependences of the crack initiation and propagation energy in steels at the loading rates over the range from 1 to 5 m/s. ü It has been demonstrated that in ductile fracture, the crack propagation velocity in Charpy specimens is about 1 to 20 m/s, whereas in brittle fracture, it is 50 to 600 m/s. ü The brittle energy practically has no changes with the temperature change. The values of brittle energy are about 2 J, whereas the values of ductile fracture come up to 150 J. The behavior of total energy of deformation and fracture and its components is similar for various steels. G. S. Pisarenko Institute for Problems of Strength http: //www. ipp. kiev. ua