Fatigue Crack Initiation and Early Propagation in Polycrystalline Copper

Polák, Jaroslav; Liškutín, P.; Vašek, A.

doi:10.1007/978-94-009-3459-7_16

Cited by 2 publications

(1 citation statement)

References 5 publications

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“…The crack growth rates of the four longest cracks were evaluated and in Figs 5(b), 6(b) and 7(b) they are plotted vs crack length a. There is an appreciable scatter of the data and therefore we have used the simplest approximation to fit the data based on the premise that the initial crack growth rate in constant strain amplitude loading is independent of the crack length (see also [3,181).…”

Section: Densitymentioning

confidence: 99%

Low Cycle Fatigue Damage Accumulation in Armco‐iron

Vašek

Polák

1991

Fatigue Fract Eng Mat Struct

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A study has been performed relating to fatigue damage accumulation in Armco-iron with a mean ferrite grain size of 40 pm. Two constant strain amplitudes, L, = 1 x (N, = 250,000 cycles) and t, = 6 x lo-' (N,= 3050 cycles) were employed to derive base data for cumulative fatigue loading where unit blocks of low (1000 cycles) and high (10 cycles) strains were mixed until failure occurred. Observations in a scanning electron microscope permitted a periodic evaluation of surface damage to be recorded. Two regimes of damage were noted. During the early crack initiation phase, crack density increased and crack growth rate was constant. During the later phase, or crack propagation stage, new cracks did not nucleate, the smallest cracks arrested, crack density decreased, and the largest cracks grew in an exponential manner, which included linkage with smaller cracks. A damage accumulation model is presented which permits a prediction of fatigue lifetime under variable amplitude loading.

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Section: Densitymentioning

confidence: 99%

Low Cycle Fatigue Damage Accumulation in Armco‐iron

Vašek

Polák

1991

Fatigue Fract Eng Mat Struct

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CYCLIC MECHANICAL BEHAVIOR AND MICROSTRUCTURE OF A 12Cr‐Mo‐V MARTENSITIC STAINLESS STEEL

Vogt

DeCallaix

Foct

1988

Fatigue Fract Eng Mat Struct

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The low cycle fatigue properties of a I2Cr-I M e V martensitic stainless steel are investigated at room temperature and correlated with its microstructure. The mechanical test results show that the behavior of this steel depends on the applied strain level. The SEM and TEM studies bring out the role of ferrite islands embedded in a tempered martensite lath matrix. Plastic deformation is essentially accommodated by ferrite: this results in extrusion formation on the surface specimen and a cellular dislocation structure. When the strain level is high, it requires a greater contribution of the tempered martensite, ferrite alone being unable to accomplish all the plastic deformation. 1NTRODUCTION12Cr stainless steels are widely used for machine components, such as turbine blades, subjected to stresses at high temperature [I]. For this reason, high temperature data are available concerning creep fracture [2], low cycle fatigue damage [3], and precipitation [4].The I2Cr-IM-V steel is commonly used in a normalized and tempered condition, involving diffusionless transformation of the austenite to martensite and precipitation reactions during tempering accompanied by recovery processes. The physical metallurgy of this alloy is therefore very complex.The objective of the present paper is to correlate the cyclic behavior with the microstructure in order to gain a better understanding of fatigue micromechanisms in this kind of alloy. Indeed if crack initiation mechanisms are well developed and clearly understood for pure materials, this aspect is less well-known for engineering materials, except austenitic stainless steels. Therefore this remains of prime interest especially for practical cases. In the present investigation, only room temperature behaviour is considered in order to eliminate oxydation and temperature effects. EXPERIMENTSThe material investigated in this work is a type DIN X20CrMoV12-1 steel. Its chemical composition by weight YO is: 0.21 C, 0.006 S, 0.017 P, 0.24 Si, 0.60 Mn, 0.02 Cu, 11.3 Cr, 0.62 Ni, 0.85 Mo, 0.36 V, 0.03 W remainder Fe. The heat treatment of the as-received material consists of austenizing at 1050°C for 1 h followed by air cooling to room temperature and tempering at 760°C for 2 h, also followed by air cooling.Tensile and low cycle fatigue tests are performed at room temperature on a 100 kN servohydraulic push-pull MTS machine. Cylindrical (10 mm diameter and 10 mm gauge length) and button-headed samples are machined from a 24/34 cm diameter pipe. Before testing, the reduced 435

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Fatigue Crack Initiation and Early Propagation in Polycrystalline Copper

Cited by 2 publications

References 5 publications

Low Cycle Fatigue Damage Accumulation in Armco‐iron

Low Cycle Fatigue Damage Accumulation in Armco‐iron

CYCLIC MECHANICAL BEHAVIOR AND MICROSTRUCTURE OF A 12Cr‐Mo‐V MARTENSITIC STAINLESS STEEL

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