Low-cycle Fatigue Behavior Of Type Research Articles

Thermo-Mechanical and Isothermal Low-Cycle Fatigue Behavior of Type 316L Stainless Steel in High-Temperature Water and Air

Two unique facilities for isothermal low-cycle fatigue (LCF) and in-phase (IP) or out-of-phase (OP) thermo-mechanical fatigue (TMF) testing of tubular specimens under boiling water reactor (BWR) and pressurized water reactor (PWR) coolant conditions were set up and successfully tested. The systems allow both strain- and stress-controlled fatigue experiments with very small strain amplitudes or complex stress/strain profiles with superimposed rather rapid temperature changes (100°C to 340°C) under flowing conditions. The present article introduces the new test facility and briefly discusses the first results of these experiments. In contrast to air, a strong effect of temperature on LCF and TMF lives was observed in deoxygenated and hydrogenated high-temperature water environment, where both lives decrease with increasing temperature above 100°C. The TMF life is between that of the isothermal LCF tests at minimum and maximum temperature. The IP TMF life is shorter than that of OP TMF and close to the LCF l...

Effects of hold time and neutron irradiation on the low-cycle fatigue behaviour of type 316-CL and their consideration in a damage model

The creep fatigue behaviour of AISI type 316 L(N) plate material has been investigated in the temperature range of 450–750 °C by performing axial strain controlled tests with GRIM specimens. The creep and creep fatigue behaviour of austenitic stainless steel material is known to be prone to neutron irradiation-induced embrittlement. Therefore, the irradiation behaviour was studied by performing irradiation experiments in the High Flux Reactor (HFR) of Petten at 550 °C. A newly developed damage model for time-dependent damage was applied to describe the failure behaviour of AISI 316 L(N) in the cyclic tests performed.

A comparative evaluation of low-cycle fatigue behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joint

A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 × 10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance of the coarse-grained region in the heat-affected zone.

An assessment of cold work effects on strain-controlled low-cycle fatigue behavior of type 304 stainless steel: Rao, K.B.S., Valsan, M., Sandhya, R., Mannan, S.L. and Rodriguez, P. Metall. Trans. A (Apr. 1993) 24A (4), 913–924

An assessment of cold work effects on strain-controlled low-cycle fatigue behavior of type 304 stainless steel: Rao, K.B.S., Valsan, M., Sandhya, R., Mannan, S.L. and Rodriguez, P. Metall. Trans. A (Apr. 1993) 24A (4), 913–924

A review of fatigue crack growth in steels under mixed mode I and II loading: Bold, P. E., Brown, M. W. and Allen, R. J. Fatigue Fract. Eng. Mater. Struct. (Oct. 1992 15 (10) 965–977

The effects of hold condition (tension-only, compression-only and tension-plus-compression holds of 1 min duration) and hold time (up to 10 min in tension) on the low-cycle fatigue behaviour of type 304 stainless steel base metal and type 308 stainless steel all-weld metal were investigated at 923 K. All the tests were performed in total axial strain control in air, employing a strain range of 1.0%. The welds were prepared by a submerged metal arc welding process. The microstructure of the base metal and the weld consisted of gamma phase and duplex gamma-delta ferrite respectively. The results clearly indicated a reduction in continuous cycling as well as creep-fatigue interaction life of type 308 SS weld metal compared with type 304 SS base metal under identical testing conditions. Hold times displayed an effect on life that was dependent not only on material condition but also on the position of the hold in the cycle. Fatigue lives recorded for type 308 SS weld in the 1 min hold-time tests were in the order: compression hold → continuous cycling → tension-plus-compression hold → tension hold. Fatique lives of 304 SS were in the order: continuous cycling → compression hold → tension-plus-compression hold → tension hold. A significant reduction in the life of the weld metal was noted on increasing the duration of tension hold time to 10 min. 308 SS weld metal exhibited cyclic softening whereas 304 SS base metal showed rapid initial hardening followed by a saturation stage. The observed variations in life are explained on the basis of crack initiation and propagation modes and microstructural changes that occured during low-cycle fatigue and creep-fatigue interaction testing.

Creep-fatigue interaction behaviour of type 308 stainless steel weld metal and type 304 stainless steel base metal

The effects of hold condition (tension-only, compression-only and tension-plus-compression holds of 1 min duration) and hold time (up to 10 min in tension) on the low-cycle fatigue behaviour of type 304 stainless steel base metal and type 308 stainless steel all-weld metal were investigated at 923 K. All the tests were performed in total axial strain control in air, employing a strain range of 1.0%. The welds were prepared by a submerged metal arc welding process. The microstructure of the base metal and the weld consisted of gamma phase and duplex gamma-delta ferrite respectively. The results clearly indicated a reduction in continuous cycling as well as creep-fatigue interaction life of type 308 SS weld metal compared with type 304 SS base metal under identical testing conditions. Hold times displayed an effect on life that was dependent not only on material condition but also on the position of the hold in the cycle. Fatigue lives recorded for type 308 SS weld in the 1 min hold-time tests were in the order: compression hold → continuous cycling → tension-plus-compression hold → tension hold. Fatique lives of 304 SS were in the order: continuous cycling → compression hold → tension-plus-compression hold → tension hold. A significant reduction in the life of the weld metal was noted on increasing the duration of tension hold time to 10 min. 308 SS weld metal exhibited cyclic softening whereas 304 SS base metal showed rapid initial hardening followed by a saturation stage. The observed variations in life are explained on the basis of crack initiation and propagation modes and microstructural changes that occured during low-cycle fatigue and creep-fatigue interaction testing.

An assessment of cold work effects on strain-controlled low-cycle fatigue behavior of type 304 stainless steel

The influence of prior cold work (PCW) on low-cycle fatigue (LCF) behavior of type 304 stainless steel has been studied at 300, 823, 923, and 1023 K by conducting total axial strain-controlled tests in solution annealed (SA, 0 pct PCW) condition and on specimens having three levels of PCW, namely, 10, 20, and 30 pct. A triangular waveform with a constant frequency of 0.1 Hz was employed for all of the tests performed over strain amplitudes in the range of ±0.25 to ± 1.25 pct. These studies have revealed that fatigue life is strongly dependent on PCW, temperature, and strain amplitude employed in testing. The SA material generally displayed better endurance in terms of total and plastic strain amplitudes than the material in 10, 20, and 30 pct PCW conditions at all of the temperatures. However, at 300 K at very low strain amplitudes, PCW material exhibited better total strain fatigue resistance. At 823 K, LCF life decreased with increasing PCW, whereas at 923 K, 10 pct PCW displayed the lowest life. An improvement in life occurred for prior deformations exceeding 10 pct at all strain amplitudes at 923 K. Fatigue life showed a noticeable decrease with increasing temperature up to 1023 K in PCW state. On the other hand, SA material displayed a minimum in fatigue life at 923 K. The fatigue life results of SA as well as all of the PCW conditions obeyed the Basquin and Coffin-Manson relationships at 300, 823, and 923 K. The constants and exponents in these equations were found to depend on the test temperature and prior metallurgical state of the material. A study is made of cyclic stress-strain behavior in SA and PCW states and the relationship between the cyclic strain-hardening exponent and fatigue behavior at different temperatures has been explored. The influence of environment on fatigue crack initiation and propagation behavior has been examined.

Strain-controlled low-cycle fatigue behaviour of type 304 stainless-steel-based material, type 308 stainless-steel weld metal and 304–308 stainless-steel weldments: Sankara Rao, K. Bhanu, Valsan, M. and Mannan, S.L. Mater. Sci. Eng. A Nov. 1990 A130 (1), 67–82

Strain-controlled low-cycle fatigue behaviour of type 304 stainless-steel-based material, type 308 stainless-steel weld metal and 304–308 stainless-steel weldments: Sankara Rao, K. Bhanu, Valsan, M. and Mannan, S.L. Mater. Sci. Eng. A Nov. 1990 A130 (1), 67–82

オーステナイト系ステンレス鋼SUS 304, 321の高温低サイクル疲労に及ぼす長時間時効の影響

オーステナイト系ステンレス鋼SUS 304, 321の高温低サイクル疲労に及ぼす長時間時効の影響

オーステナイト系ステンレス鋼SUS 304, 321の高温低サイクル疲労に及ぼすひずみ波形の影響

オーステナイト系ステンレス鋼SUS 304, 321の高温低サイクル疲労に及ぼすひずみ波形の影響

Effects of surface roughness and strain range on the low-cycle fatigue behavior of type 304 stainless steel

The low-cycle fatigue behavior of steel specimens having well-characterized surface properties introduced in smooth specimens by a SiC technique was studied. It was found that by introducing an initial surface roughness, the percent of life in crack initiation decreases from 46 to 26 percent at the largest strain range and from 91 to 75 percent at the smallest strain range investigated. The significant point of this comparison is that at lower strain ranges, even when the surface contains irregularities of the kind described, crack initiation occupies a major portion of total life. (JRD)

Considerations of crack initiation and crack propagation in low-cycle fatigue

The low-cycle fatigue behavior of Type 304 stainless steel at 593/sup 0/C is examined along with aspects of crack propagation in smooth specimens. Results show that the number of cycles to initiate cracks in smooth specimens decreases as the strain range increases. Crack-initiation life can be directly determined from plots of strain cycles vs crack length. (JRD)

Summary of a theory for void nucleation during irradiation in terms of brownian motion of vacancy-gas atoms

The low-cycle fatigue behavior of Type 304 stainless steel at 593/sup 0/C is examined along with the crack-initiation and crack propagation aspects of the fatigue life in smooth specimens. It is noted that at present, no method is available that has the capability of predicting the crack-initiation life. Only when the variables affecting crack initiation are quantitatively investigated will it be possible to achieve an understanding of the effect of a specific variable on fatigue life. (JRD)

Effect of surface roughness on low-cycle fatigue behavior of type 304 stainless steel

The effects of surface roughness on the low-cycle fatigue life of Type 304 stainless steel at 593°C in air have been investigated. It is observed that, at a strain rate of 4 × 10−3 s−1 and a total strain range of 1 pct, the fatigue life (Nf cycles) decreases with an increase in surface roughness. Information on crack growthvs strain cycles has been generated, as a function of surface roughness, by the measurement of striation spacing on fractured surfaces of specimens tested to failure. Crack propagation follows the Ina ∞N (wherea is the crack length afterN strain cycles) relation for longer specimen fatigue lives (Nf > 2700 cycles) and departs from Ina ∞N for shorter fatigue lives. A quantitative estimate is made of the number of cycles No(r) to generate a crack length equal to 0.1 mm (≈ 1 grain diam). The initial surface roughness significantly affects only the initiation component of specimen life time. The effect of roughness on crack initiation is described byN0(R) = 1012R−0.21, whereR is the surface roughness (root-mean-square value) in microns.