Fatigue Life of CrMoV Steel after Long Term Service

2014 ◽  
Vol 224 ◽  
pp. 57-62
Author(s):  
Stanisław Mroziński ◽  
Grzegorz Golański ◽  
Jacek Słania
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Hysteresis Loop ◽  
Steam Pressure ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Constant Amplitude ◽  
Bainitic Microstructure ◽  
Stress Cycles

The paper presents the results of research on the microstructure and mechanical properties of 12HMF steel after long-term service. The investigated material was taken from a pipe after service at the temperature of 490°C, steam pressure of 8 MPa and service time of 419 988 hours. Performed research has shown that the 12HMF steel after service was characterized by ferritic-bainitic microstructure without any visible advanced processes of its degradation, a typical microstructure for this grade of steel. The tests of mechanical properties have proved that the examined steel after service was characterized by very low impact strength KV, and yield strength lower than the required minimum. Performed fatigue tests of constant amplitude, as well as the programmed ones, have shown that the investigated steel after service is characterized by cyclic softening without a clear period of stabilization of the parameters of hysteresis loop. Moreover, it has been proved that slight changes in the hysteresis loop parameters, as a function of the number of stress cycles, have a significant influence on the obtained material data used when calculating the life.

scholarly journals Microstructure and Mechanical Properties of CrMoV Steel after Long-Term Service

2016 ◽  
Vol 61 (1) ◽  
pp. 51-54 ◽  
Author(s):  
G. Golański ◽  
I. Pietryka ◽  
J. Słania ◽  
S. Mroziński ◽  
J. Jasak
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elevated Temperature ◽  
Yield Strength ◽  
Impact Energy ◽  
Welded Joint ◽  
Steam Pressure ◽  
Microstructure And Mechanical Properties ◽  
Bainitic Microstructure

The paper presents the results of research on the microstructure and mechanical properties of 12HMF steel after longterm service. The investigated material was taken from a pipeline with circumferential welded joint after 419 988 hours of service at the temperature of 490°C, steam pressure 8 MPa. Performed research has shown that the 12HMF steel after service was characterized by a typical microstructure for this grade of steel, that is a ferritic-bainitic microstructure without any visible advanced processes of its degradation. The investigation of mechanical properties has shown that the examined steel after service was characterized by a very low impact energy KV, and yield strength lower than the required minimum. Whilst tensile strength and yield strength determined at elevated temperature was higher and similar to the standard requirements, respectively. It has been proved that the main cause of an increase in brittleness and a decrease in yield strength of the examined steel should be seen in the segregation of phosphorus to grain boundaries and the formation of precipitate free zones near the boundaries.

Cyclic Mechanical Properties of 16MnR Welded Joint under Constant

2011 ◽  
Vol 197-198 ◽  
pp. 1658-1661
Author(s):  
Ying Xiong ◽  
Han Ying Zheng
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Endurance Limit ◽  
Welded Joint ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Test Results ◽  
Control Test ◽  
Strain Control ◽  
Fatigue Endurance

Fatigue tests are carried out for 16MnR welded joint under constant strain control. Test results reveal that 16MnR weld metal exhibits characteristic of cyclic softening and non-masing obviously. The strain–life curve can be best described by the three-parameter equation. It shows the fatigue endurance limit in the heat-affecting zone (HAZ) of welded joint is lower than that in the weld metal.

scholarly journals Changing in Fatigue Life of 300 M Bainitic Steel After Laser Carburizing and Plasma Nitriding

2018 ◽  
Vol 165 ◽  
pp. 21002 ◽  
Author(s):  
Antonio J. Abdalla ◽  
Douglas Santos ◽  
Getúlio Vasconcelos ◽  
Vladimir H. Baggio-Scheid ◽  
Deivid F. Silva
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
High Strength ◽  
Tensile Tests ◽  
Steel Sample ◽  
Fatigue Tests ◽  
300M Steel ◽  
Structural Applications

In this work 300M steel samples is used. This high-strength steel is used in aeronautic and aerospace industry and other structural applications. Initially the 300 M steel sample was submitted to a heat treatment to obtain a bainític structure. It was heated at 850 °C for 30 minutes and after that, cooled at 300 °C for 60 minutes. Afterwards two types of surface treatments have been employed: (a) using low-power laser CO2 (125 W) for introducing carbon into the surface and (b) plasma nitriding at a temperature of 500° C for 3 hours. After surface treatment, the metallographic preparation was carried out and the observations with optical and electronic microscopy have been made. The analysis of the coating showed an increase in the hardness of layer formed on the surface, mainly, among the nitriding layers. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests were strongly affected by the bainitic microstructure. The steel that received the nitriding surface by plasma treatment showed better fatigue behavior. The results are very promising because the layer formed on steel surface, in addition to improving the fatigue life, still improves protection against corrosion and wear.

scholarly journals Effects of Actual Marine Atmospheric Pre-Corrosion and Pre-Fatigue on the Fatigue Property of 7085 Aluminum Alloy

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 81
Author(s):  
Laixin Shi ◽  
Lin Xiang ◽  
Jianquan Tao ◽  
Jun Liu ◽  
Qiang Chen ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Pitting Corrosion ◽  
Atmospheric Corrosion ◽  
Fatigue Property ◽  
Outdoor Exposure ◽  
Fatigue Tests ◽  
Constant Amplitude ◽  
Fatigue Fractography ◽  
Corrosion Mode

Effects of actual marine atmospheric precorrosion and prefatigue on the fatigue property of 7085-T7452 aluminum alloy were investigated by using the methods of marine atmospheric outdoor exposure tests and constant amplitude axial fatigue tests. Marine atmospheric corrosion morphologies, fatigue life, and fatigue fractography were analyzed. After three months of outdoor exposure, both pitting corrosion and intergranular corrosion (IGC) occurred, while the latter was the dominant marine atmospheric corrosion mode. Marine atmospheric precorrosion could result in a dramatical decrease in the fatigue life of the as-received 7085-T7452 aluminum alloy, while selective prefatigue can improve the total fatigue life of the precorroded specimen. The mechanism of the actual marine atmospheric corrosion and its effects on the fatigue life of the 7085-T7452 aluminum alloy were also discussed.

The Effects of Periodic High Loads on Fretting Fatigue

1981 ◽  
Vol 103 (3) ◽  
pp. 223-228 ◽  
Author(s):  
A. Kantimathi ◽  
J. A. Alic
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Growth Retardation ◽  
Fretting Fatigue ◽  
Fatigue Tests ◽  
Constant Amplitude ◽  
Axial Loads ◽  
Prolonged Fatigue ◽  
Stress Ratios ◽  
Crack Growth Retardation

Fretting fatigue tests have been conducted on 7075-T7351 aluminum alloy coupons with fretting pads of the same material. Three different stress ratios were used, the otherwise constant amplitude axial loads being interrupted every 1000 cycles by either tensile overloads to 400 MPa or compressive underloads to −200 MPa. Tensile overloads greatly prolonged fatigue life for low stresses where the overload ratios were 1.6 and above; compressive underloads had comparatively little effect. The results are discussed in terms of crack growth retardation phenomena.

Applicability of Equivalent Constant Amplitude Loading for Assessing the Fatigue Life of Pipelines and Risers and the Influence of Compressive Stress Cycles

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri
Keyword(s):  
Experimental Investigation ◽  
Fatigue Life ◽  
Compressive Stress ◽  
Time History ◽  
Life Assessment ◽  
Constant Amplitude ◽  
Safety Factors ◽  
Variable Amplitude ◽  
Fatigue Life Assessment ◽  
Stress Cycles

Fatigue life assessment of pipelines and risers is a complex process, involving various uncertainties. The selection of an appropriate fatigue model is important for establishing the inspection intervals and maintenance criteria. In offshore structures, the vortex-induced vibration (VIV) could cause severe fatigue damage in risers and pipelines, resulting in leakage or even catastrophic failure. The industry has customarily used simple fatigue models for fatigue life assessment of pipelines and risers (such as the Paris or Walker models); however, these models were developed based on constant amplitude loading scenarios. In contrast, VIV-induced stress-time history has a variable amplitude nature. The use of the simplified approach (which is inherently non conservative), has necessitated the implementation of large safety factors for fatigue design of pipelines and risers. Moreover, most of the experimental investigations conducted to date with the aim of characterizing the fatigue response of pipelines and risers have been done based on incorporation of constant amplitude loading (CAL) scenarios (which is unrealistic), or converting the variable amplitude loading (VAL) scenarios to an equivalent CAL. This study demonstrates that the use of such approaches would not be lead to accurate assessment of the fatigue response of risers subject to VIV-induced VAL. The experimental investigation performed in this study will also clarify the underlying reasons for the use of large safety factors by the industry when assessing the fatigue life of pipelines and risers. In addition, an experimental investigation was also conducted to highlight the influence of the compressive portion of VIV stress-time history on the fatigue life of such components. It is shown that the compressive stress cycles significantly influence the fatigue crack growth response of risers, and their presence should not be ignored.

The Effect of Manufacturing Defects on the Fatigue Behaviour of Ti-6Al-4V Specimens Fabricated Using Selective Laser Melting

2014 ◽  
Vol 891-892 ◽  
pp. 1519-1524 ◽  
Author(s):  
Qian Chu Liu ◽  
Joe Elambasseril ◽  
Shou Jin Sun ◽  
Martin Leary ◽  
Milan Brandt ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Selective Laser Melting ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Metallic Materials ◽  
Laser Melting ◽  
Manufacturing Defects ◽  
Materials Properties

Additive Manufacturing (AM) technologies are considered revolutionary because they could fundamentally change the way products are designed. Selective Laser Melting (SLM) is a metal based AM process with significant and growing potential for the manufacture of aerospace components. Traditionally a material needs to be listed in the Metallic Materials Properties Development and Standardization (MMPDS) handbook if it is to be considered certified. However, this requires a considerable amount of test data to be generated on the materials mechanical properties. Therefore, the MMPDS certification process does not lend itself easily to the certification of AM components as the final component can have similar mechanical properties to wrought alloys combined with the defects associated with traditional casting and welding technologies. These defects can substantially decrease the fatigue life of a fabricated component. The primary purpose of this investigation was to study the fatigue behaviour of as-built Ti-6Al-4V (Ti64) samples. Fatigue tests were performed on the Ti-6Al-4V specimens built using SLM with a variety of layer thicknesses and build (vertical or horizontal) directions. Fractography revealed the presence of a range of manufacturing defects located at or near the surface of the specimens. The experimental results indicated that Lack-of-Fusion (LOF) defects were primarily responsible for fatigue crack initiation. The reduction in fatigue life appeared to be affected by the location, size and shape of the LOF defect.

Multiaxial Fatigue of 6061-T6 Aluminum Alloy under Corrosive Environment

2016 ◽  
Vol 853 ◽  
pp. 77-82
Author(s):  
Xu Chen ◽  
Rui Si Xing ◽  
Xiao Peng Liu
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Plastic Strain Amplitude ◽  
Multiaxial Fatigue ◽  
Corrosive Environment

Aluminium alloys are widely used in the fields of automobile, machinery and naval construction. To investigate the effect of non-proportional loadings and corrosive environment on the fatigue resistance of 6061-T6 aluminum alloy, a set of uniaxial and multiaxial low cycle fatigue tests were carried out. Firstly, the results of uniaxial tests showed that the alloy exhibited cyclic hardening then cyclic softening. With the increase of stress amplitude the cyclic softening became pronounced. The increasing of plastic deformation was basically cyclically stable with small plastic strain amplitude accumulation when the stress amplitude was lower than 200MPa ,while it was increasing rapidly when the stress amplitude was higher than 220MPa. Secondly, it was observed that non-proportional cycle additional hardening of 6061-T6 aluminum alloy was little. While the fatigue life was badly affected by the loading paths. Thirdly ,the fatigue corrosion interactions were also talked about in details by performing the tests under the same loading conditions with corrosive environment. The experiment proved that the seawater corrosion has huge impact on fatigue life under pH 3. Finally, a multi-axial fatigue life prediction model was used to predict the fatigue life with or without the corrosive environment which showed a good agreement with experimental data.

scholarly journals Impact of Long-Term Operation on the Reliability and Durability of Transit Gas Pipelines

2020 ◽  
Vol 70 (1) ◽  
pp. 115-126
Author(s):  
Okipnyi Igor ◽  
Poberezhny Lyubomyr ◽  
Zapukhliak Vasyl ◽  
Hrytsanchuk Andrii ◽  
Poberezhna Liubov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Fatigue ◽  
Static Loading ◽  
Physical And Mechanical Properties ◽  
Fatigue Tests ◽  
Gas Pipelines ◽  
Term Operation ◽  
Full Capacity ◽  
Corrosive Environments

AbstractCorrosion and corrosion-fatigue tests of the material of the pipeline, which was in operation for 41 years. It has been shown that prolonged operation reduces the parameters of resistance to fatigue and prolonged static loading in corrosive environments. It was established that the degradation of physical and mechanical properties is insignificant, Ukraine’s main gas pipelines are ready to operate at full capacity provided that timely monitoring measures are carried out.

Comparison Research on Mechanical Properties of Stainless Steel after Laser Peened and Ultrasonically Peened

2013 ◽  
Vol 690-693 ◽  
pp. 2107-2111
Author(s):  
Cheng Wang ◽  
Zhi Lin Lai ◽  
Dong Sun ◽  
Liu Cheng Zhou ◽  
Zhi Bin An
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Laser Peening ◽  
Comparison Research ◽  
Vibration Fatigue ◽  
Ultrasonic Shot Peening ◽  
Processing Techniques ◽  
Compressive Residual Stresses

The mechanical properties of 1Cr11Ni2W2MoV stainless steel after laser peening (LP) and ultrasonic shot peening (USP) were examined and compared. The stainless steel specimens were treated with the two different surface processing techniques. X-ray diffractometry (XRD), scanning electron microscope (SEM), microhardness tester were used to investigate microstructure and mechanical properties. Vibration fatigue tests of untreated, LPed and USPed samples were also conducted. The results indicated that LP treatment can improved the fatigue life of 1Cr11Ni2W2MoV stainless steel more effectively. The increases of the compressive residual stress depth and microhardness in surface layer after LP were greater than that of USP. The SEM studies showed that USP treatment had an advantage in microstructure refinement. The compressive residual stresses make great contributions to the superiority of LP in the improvement of fatigue life of 1Cr11Ni2W2MoV stainless steel to USP.

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