Extremely low cycle fatigue tests on structural carbon steel and stainless steel

NUREG/CR-6909 of USA and JSME of Japan proposed new rules for evaluating environmental effects in fatigue analyses of reactors components. These rules were established from a lot of fatigue data with polished specimens under simple loading condition. The effects of surface finish or complex loading condition were reported in some papers, but these data were obtained with the simple shaped specimens. In order to evaluate the effects of surface finish and loading condition and to confirm the applicability of the proposed rules to actual components, Low Cycle Fatigue tests are performed in PWR environment with the specimens cut from 316 austenitic stainless steel welded piping. The pipes are machined to have three levels of surface finish condition and the load pattern simulating the thermal stress is applied to specimens. In this study, the effect of surface finish on fatigue life is included to be small for 316 austenitic stainless steel welded piping. Considering the insensitive region in the current evaluation rule, predicted accuracy is increased and possibility of improving the current rule is indicated.

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Parameters influencing the low-cycle fatigue life of materials in pressure water reactor nuclear power plants / Parametry ovlivòující únavové chování materiálù pro tlakovodní jaderné reaktory v režimu nízkocyklové únavy

Koroze a ochrana materialu ◽

10.1515/kom-2015-0016 ◽

2015 ◽

Vol 59 (3) ◽

pp. 91-98

Author(s):

V. Šefl

Keyword(s):

Stainless Steel ◽

Fatigue Life ◽

Carbon Steel ◽

Austenitic Stainless Steel ◽

Literature Review ◽

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Low Cycle Fatigue ◽

Cycle Fatigue

Abstract In this literature review we identify and quantify the parameters influencing the low-cycle fatigue life of materials commonly used in nuclear power plants. The parameters are divided into several groups and individually described. The main groups are material properties, mode of cycling and environment parameters. The groups are further divided by the material type - some parameters influence only certain kind of material, e.g. sulfur content may decreases fatigue life of carbon steel, but is not relevant for austenitic stainless steel; austenitic stainless steel is more sensitive to concentration of dissolved oxygen in the environment compared to the carbon steel. The combination of parameters i.e. conjoint action of several detrimental parameters is discussed. It is also noted that for certain parameters to decrease fatigue life, it is necessary for other parameter to reach certain threshold value. Two different approaches have been suggested in literature to describe this complex problem - the Fen factor and development of new design fatigue curves. The threshold values and examples of commonly used relationships for calculation of fatigue lives are included. This work is valuable because it provides the reader with long-term literature review with focus on real effect of environmental parameters on fatigue life of nuclear power plant materials.

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Low-Cycle-Fatigue Properties of a 17-4 PH Stainless Steel Manufactured via Selective Laser Melting

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.877.55 ◽

2021 ◽

Vol 877 ◽

pp. 55-60

Author(s):

Lorenzo Maccioni ◽

Eleonora Rampazzo ◽

Filippo Nalli ◽

Yuri Borgianni ◽

Franco Concli

Keyword(s):

Stainless Steel ◽

Selective Laser Melting ◽

Low Cycle Fatigue ◽

Fatigue Tests ◽

Fatigue Properties ◽

Cycle Fatigue ◽

Laser Melting ◽

Softening Behavior ◽

The One ◽

Cylindrical Samples

In this paper, the static and low-cycle-fatigue (LCF) behavior of wrought samples of 17-4 PH stainless steel (SS) manufactured via Selective Laser Melting (SLM) are presented. On the one hand, several scholars have studied SLM materials and literature reports a huge amount of data as for the high-cycle-fatigue (HCF) behavior. On the other hand, few are the data available on the LCF behavior of those materials. The aim of the present research is to provide reliable data for an as-build 17-4 PH steel manufactured via SLM techniques. Only with quantitative data, indeed, it is possible to exploit all the advantages that this technology can offer. In this regard, both quasi-static (QS) and low-cycle-fatigue tests were performed on Additive Manufacturing (AM) cylindrical samples. Through QS tests, the constitutive low has been defined. Strain-controlled fatigue tests on an electromechanical machine were performed on 12 samples designed according to the ASTM standard. Tests were continued also after the stabilization was reached (needed for the cyclic curve described with the Ramberg-Osgood equation) to obtain also the fatigue (ε-N) curve. Results show that the material has a softening behavior. The Basquin-Coffin-Manson (BCM) parameters were tuned on the basis of the ε-N combinations after rupture.

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Improvement of Thermomechanical Fatigue Life in Nitrogen Alloyed 316 Stainless Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.1429 ◽

2005 ◽

Vol 475-479 ◽

pp. 1429-1432 ◽

Cited By ~ 4

Author(s):

Dae Whan Kim ◽

Chang Hee Han ◽

Woo Seog Ryu

Keyword(s):

Stainless Steel ◽

Fatigue Life ◽

Temperature Change ◽

Low Cycle Fatigue ◽

Strain Range ◽

Thermomechanical Fatigue ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Phase Condition ◽

Higher Temperature

Fatigue tests of type 316 and 316LN stainless steel were conducted at RT and 600ı, 0.8~1.5% strain range for low cycle fatigue (LCF), 300~600ı, 0% strain range for thermal fatigue (TF) and 300~600ı, 2% strain range, in-phase or out-of-phase for thermomechanical fatigue (TMF). LCF, TF, and TMF lives were increased but saturation stresses were decreased with the addition of nitrogen. The higher temperature was the lower TF life at a same temperature change. The minimum temperature change for TF failure was more than 100ı. TMF life was higher at inphase condition than at out-of-phase condition. Fracture mode was transgranular for LCF and outof- phase of TMF and almost transgranular and small intergranular for TF and in-phase TMF.

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Initial Aspects of Low-Cycle Fatigue Fracture of Martensitic Steels

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.385 ◽

2007 ◽

Vol 348-349 ◽

pp. 385-388 ◽

Cited By ~ 3

Author(s):

Tamaz Eterashvili ◽

T. Dzigrashvili ◽

M. Vardosanidze

Keyword(s):

Plastic Deformation ◽

Stainless Steel ◽

Plastic Zone ◽

Fatigue Fracture ◽

Main Crack ◽

Low Cycle Fatigue ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Slip Bands ◽

Number Of Cycles

This study deals with the SEM and optical microscopic characterization of fatigue plastic deformation process during fatigue crack initiation to understand where, why and how cracks initiate under conditions of low cycle fatigue. Samples were prepared from the 13Х11Н2В2МФ high-chromium stainless steel used for fusion power applications. The low-cycle tests were conducted at room temperature with the standard V-notched samples prepared from conventional stainless steel. The following characteristics were studied during fatigue tests: 1 macrocrack propagation, 2. interaction between macrocrack and isolated microcracks, 3. interaction between macrocrack and slip bands, 4. interaction between macrocrack and microstructure elements of the steel. The above experiments show that during macrocrack propagation a plastic zone is formed around it, where isolated microcracks and slip bands of 2-3 different directions are observed. Measurement of plastic zone dimensions after different number of cycles of deformation show that plastic zone size increases during the first stage of cyclic deformation (until definite number of cycles are completed), and then remains unchanged. The observations show that main crack is composed of individual micro-components, the lengths of which are in a good correlation with the dimensions of microstructure elements of the steel (former austenite grains, martensite crystals). It was revealed that during growth, as a rule, macrocrack rarely propagates along isolated microcracks and slip bands. Direction of macrocrack propagation changes while passing from one microstructure element to another, so that main direction is the same. No preferable transcrystalline or intercrystalline propagation of macrocrack has been observed in the investigated steel. It is shown that after subsequent fatigue tests, dimensions of the previously created slip bands increase, and additional new slip band are also formed. The sites and frequency of slip bands’ formation in plastic zone are also studied. It was observed that the boundaries and mainly the sites of intersection of martensite crystals are the sites of isolated (rough) microcracks’ formation. The dimensions of slip bands are comparable with those of martensite crystals. The angles between the main crack propagation direction and slip bands varied from 30o to 60o, however, most of the slip bands were oriented at 45o to the main crack. Based on the obtained results a conclusion is made that plastic deformation in samples go inhomogeneously. In plastic zones, along with the heavily deformed areas, almost non-deformed areas are also observed. The speed of fatigue fracture increases with the increase in frequency and amplitude of deformations. Generally, the annealed samples are destructed prematurely in comparison with non-annealed ones of the investigated steel.

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Internal Crack Initiation in Low-Cycle Fatigue of Stainless Steel

ASME 2010 Pressure Vessels and Piping Conference: Volume 3 ◽

10.1115/pvp2010-25507 ◽

2010 ◽

Author(s):

Masayuki Kamaya ◽

Masahiro Kawakubo

Keyword(s):

Stainless Steel ◽

Crack Initiation ◽

Strain Amplitude ◽

Low Cycle Fatigue ◽

Fatigue Tests ◽

Internal Crack ◽

Surface Cracks ◽

Cycle Fatigue ◽

Type Specimens ◽

316 Stainless Steel

Internal cracks were observed on the fracture surface of Type 316 stainless steel specimens subjected to a low-cycle fatigue test, in which the strain amplitude was more than 1%. In some cases the specimens fractured due to these internal cracks. In this study, the reason and conditions for the internal crack initiation were examined. Fatigue experiments were conducted using Type 316 stainless steel. In order to enhance the internal crack initiation, the specimens were subjected to pre-damaging and surface cracks were removed before the start of the fatigue tests. It was shown that specimens fractured due to internal cracks when the strain amplitude of pre-damaging was more than 1% and hourglass-type specimens were used. The fatigue life was reduced largely due to the internal cracks and the magnitude of reduction was more significant for the smaller strain amplitude of the fatigue tests. Inclusions were observed at the origin of some internal cracks. It was deduced that the hourglass geometry of the specimen enhanced the internal crack initiation. Namely, the multi-axial field was one of the factors promoting the internal crack initiation.

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The effects of robot welding and manual welding on the low- and high-cycle fatigue lives of SM50A carbon steel weld zones

Advances in Mechanical Engineering ◽

10.1177/1687814019828266 ◽

2019 ◽

Vol 11 (3) ◽

pp. 168781401982826

Author(s):

Changwan Han ◽

Changhwan Yang ◽

Hanjong Kim ◽

Seonghun Park

Keyword(s):

Grain Size ◽

Carbon Steel ◽

Arc Welding ◽

High Cycle Fatigue ◽

Low Cycle Fatigue ◽

Weld Zone ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Three Point Bending ◽

Robot Welding

The purpose of this study is to analyze the differences between the effects of robot welding and manual welding on the low- and high-cycle fatigue lives of the weld zones for T-shaped weld structures fabricated from SM50A carbon steel using a CO2 gas arc welding method. Fatigue tests were conducted using a three-point bending method, and the S-N curves of the manual welding and robot welding crossed each other at approximately 3 × 104 cycles. The robot welding weld zone had better high-cycle fatigue lives than the manual welding. The results are attributable to the fact that the more uniform and higher welding speed of the robot welding leads to smaller weld zone area (i.e. ~12% smaller than the manual welding) and also smaller grain size than the manual welding. Because a smaller grain size in the robot welding weld zone results in a higher hardness than the manual welding and material brittleness increases with increasing hardness, the robot welding weld zone shows better high-cycle fatigue lives but poorer low-cycle fatigue lives than the manual welding.

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Experimental Stress Analysis for Four 24-in. ANSI Standard B16.9 Tees

Journal of Pressure Vessel Technology ◽

10.1115/1.3454572 ◽

1977 ◽

Vol 99 (4) ◽

pp. 537-552 ◽

Cited By ~ 2

Author(s):

J. K. Hayes ◽

S. E. Moore

Keyword(s):

Carbon Steel ◽

Nuclear Power ◽

Low Cycle Fatigue ◽

Branch Pipe ◽

Fatigue Tests ◽

Elastic Response ◽

Experimental Stress ◽

Stress Distributions ◽

Cycle Fatigue ◽

Experimental Stress Analysis

This paper describes the experimental stress analysis of low cycle fatigue tests of four tees tested by Combustion Engineering, Inc. (C-E) under subcontract to Union Carbide Nuclear Division. These tests are part of the ORNL Design Criteria for Piping and Nozzles Program which is being conducted for the development of design criteria for nuclear power plant service piping components. The test assemblies were fabricated at C-E from commercially obtained ANSI B16.9 tees and matching diameter steel pipes welded to the tees, with suitable end closures and fixtures for applying the loads. The tees tested and discussed in this report are described in the following: Tee Number/Material/Nominal Size: T–11/carbon steel/24″×24″×24″ sch 160; T–12/carbon steel/24″×24″×10″ sch 40; T–13/carbon steel/24″×24″×10″ sch 160; T–16/stainless steel/24″×24″×24″ sch 10. Each tee test assembly was instrumented with approximately 240 rectangular strain gage rosettes for determining elastic stress distributions, and six linear variable displacement transducers for determining flexibility factors. Elastic-response tests were conducted for 12 loading conditions consisting of internal pressure, pure bending and torsional moments and direct force loads applied individually to the branch pipe extension and to one end of the run pipe. The other run pipe extension was fixed rigidly to the loading frame. Automatic data handling equipment and data reduction techniques were used to process the strain gage readings. For each loading condition, stress distributions were determined and the locations and magnitudes of the maximum stresses were identified. Test results are presented and compared with appropriate design formulas of the ASME Boiler and Pressure Vessel Code, Section III. After the elastic-response tests were completed, three of the tees were low-cycle fatigue tested by pressure cycling using transformer oil. The T-11 and T-13 tees were pressure cycled for 100 psig (790 kPa) to 7000 psig (48 360 kPa); whereas, the T-12 tee was pressure cycled from 0 psig (100 kPa) to 1800 psig (12 510 kPa). A low-cycle fatigue test was performed on the T-16 tee assembly by applying a bending moment to the branch pipe in the plane of the tee with the tee pressurized to a constant internal pressure of 300 psig (2170 kPa). All low-cycle fatigue tests were performed until a through-the-wall fatigue crack occurred as evidenced by a leak. Subparagraph NB-3653.6 of ASME Code, Section III, Division I, Nuclear Power Plant Components was used to calculate the fatigue design life and comparisons were made with the experimentally determined fatigue life.

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An Energy-Based Unified Approach to Predict the Low-Cycle Fatigue Life of Type 316L Stainless Steel under Various Temperatures and Strain-Rates

Materials ◽

10.3390/ma12071090 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1090 ◽

Cited By ~ 2

Author(s):

Nae Tak ◽

Jung-Seok Kim ◽

Jae-Yong Lim

Keyword(s):

Stainless Steel ◽

Strain Rate ◽

316L Stainless Steel ◽

Low Cycle Fatigue ◽

Tensile Tests ◽

Fatigue Tests ◽

Strain Rates ◽

Cycle Fatigue ◽

Type 316L ◽

Type 316L Stainless Steel

An energy-based low-cycle fatigue model was proposed for applications at a range of temperatures. An existing model was extended to the integrated approach, incorporating the simultaneous effects of strain rate and temperature. A favored material at high temperature, type 316L stainless steel, was selected in this study and its material characteristics were investigated. Tensile tests and low-cycle fatigue tests were performed using several strain rates at a temperature ranging from room temperature to 650 °C. Material properties were obtained in terms of temperature using the displacement-controlled tensile tests and further material response were investigated using strain-controlled tensile tests. Consequently, no pronounced reduction in strengths occurred at temperatures between 300 and 550 °C, and a negative strain rate response was observed in the temperature range. Based on the low-cycle fatigue tests by varying strain rates and temperature, it was found that a normalized plastic strain energy density and a strain-rate modified cycle were successfully correlated. The accuracy of the model was discussed by comparing between predicted and experimental lives.

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