scholarly journals Application of a √ area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1033 ◽  
Author(s):  
Roman Aigner ◽  
Christian Garb ◽  
Martin Leitner ◽  
Michael Stoschka ◽  
Florian Grün
Keyword(s):  
Elevated Temperature ◽  
Fatigue Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Damage Mechanism ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Cast Aluminum ◽  
Fatigue Assessment ◽  
Cast Aluminum Alloys

This paper contributes to the effect of elevated temperature on the fatigue strength of common aluminum cast alloys EN AC-46200 and EN AC-45500. The examination covers both static as well as cyclic fatigue investigations to study the damage mechanism of the as-cast and post-heat-treated alloys. The investigated fracture surfaces suggest a change in crack origin at elevated temperature of 150 ∘ C. At room temperature, most fatigue tests reveal shrinkage-based micro pores as their crack initiation, whereas large slipping areas occur at elevated temperature. Finally, a modified a r e a -based fatigue strength model for elevated temperatures is proposed. The original a r e a model was developed by Murakami and uses the square root of the projected area of fatigue fracture-initiating defects to correlate with the fatigue strength at room temperature. The adopted concept reveals a proper fit for the fatigue assessment of cast Al-Si materials at elevated temperatures; in detail, the slope of the original model according to Murakami should be decreased at higher temperatures as the spatial extent of casting imperfections becomes less dominant at elevated temperatures. This goes along with the increased long crack threshold at higher operating temperature conditions.

Elucidation of the High Cycle Fatigue Damage Mechanism of Modified 9Cr-1Mo Steel at Elevated Temperature

2015 ◽  
Author(s):  
Takuya Murakoshi ◽  
Motoyuki Ochi ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Surface Hardness ◽  
Diffraction Method ◽  
Fatigue Loading ◽  
Damage Mechanism ◽  
Fatigue Tests ◽  
Electron Back Scatter Diffraction ◽  
Cycle Fatigue

Modified 9Cr-1Mo steel is one of the heat-resistant steels developed for steam generator in a FBR (Fast Breeder Reactor). When it is used in a FBR, the lifetime of the steel under HCF (High Cycle Fatigue) and V-HCF (Very-High Cycle Fatigue) caused by flow-induced vibration has to be considered for assuring its long-term reliability up to 1011 cycles. Since previous studies showed that the fatigue limit did not appear up to 108 cycles, it is necessary to investigate the fatigue strength of this alloy in cycles higher than 108 cycles. In this study, in order to clarify high cycle fatigue strength and fracture mechanism of the modified 9Cr-1Mo steel, the change of the lath martensitic strengthening structure was observed in detail on the surface of specimens fractured by rotary bending fatigue tests by using EBSD (Electron Back-Scatter Diffraction) method. The Kernel Average Misorientation (KAM) value obtained from the EBSD analysis was used for the quantitative evaluation of the change of the lath martensitic texture. It was found that the average KAM values clearly decreased on the surface areas of the fractured specimens after the application of 107-108 cycles of fatigue loading at temperatures higher than 550°C. This result indicates that degradation of the lath martensitic texture occurred around the surface of specimens tested at the temperature higher than 550°C. In order to quantitatively evaluate the decrease of its strength, a hardness test was performed at room temperature by using a nanoindentation method. It was confirmed that the surface hardness of specimens decreased drastically in the specimens fractured at temperatures higher than 550°C. From these results, it was concluded that the effective 0.2%-proof stress decreased during the fatigue tests by the degradation of the lath martensitic texture caused by the fatigue loading at elevated temperatures. Further analyses are indispensable for explicating the damage mechanism more in detail.

Fatigue Strength of Maraging Steel at Elevated Temperatures

2008 ◽  
Vol 385-387 ◽  
pp. 161-164 ◽  
Author(s):  
T. Iwamoto ◽  
Norio Kawagoishi ◽  
Nu Yan ◽  
Eiji Kondo ◽  
Kazuhiro Morino
Keyword(s):  
Elevated Temperature ◽  
Fatigue Strength ◽  
Maraging Steel ◽  
Fracture Mechanism ◽  
Elevated Temperatures ◽  
Surface Oxidation ◽  
Fatigue Tests ◽  
Age Hardening ◽  
Effect Of Temperature ◽  
Rotating Bending Fatigue

Rotating bending fatigue tests were carried out to investigate the effects of temperature on the fatigue strength and the fracture mechanism of an 18 % Ni maraging steel at room and elevated temperatures of 473K and 673K. Fatigue strength was higher at elevated temperatures than at room temperature, though static strength was decreased by softening at elevated temperature. There was no effect of temperature on crack morphology and fracture mechanism. On the other hand, during fatigue process at elevated temperature, the specimen was age-hardened and the specimen surface was oxide. That is, the increase in fatigue strength at elevated temperature was mainly caused by the increase in hardness due to age-hardening and suppression of a crack initiation due to surface oxidation.

FATIGUE STRENGTH IMPROVEMENT BY PEENING TREATMENT IN DEGASSING PROCESSED CAST ALUMINUM ALLOYS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3593-3598 ◽  
Author(s):  
YASUO OCHI ◽  
KIYOTAKA MASAKI ◽  
TAKASHI MATSUMURA ◽  
YOHEI KUMAGAI ◽  
TATSUHIKO HAMAGUCHI ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Aluminum Alloys ◽  
Shot Peening ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Cast Aluminum ◽  
Cast Aluminum Alloys ◽  
Rotating Bending Fatigue ◽  
Cast Alloys

Rotating bending fatigue tests were carried out in order to investigate effects of shot peening and laser peening treatment on fatigue properties of degassing processed cast aluminum alloys. Degassing was useful for decreasing cast defects and increasing the range of fatigue life and fatigue strength at 107 cycles compared with those of non-degassed cast alloys. The shot peening and the laser peening treatments also showed remarkable effects for increasing the resistance of crack propagation behaviors and improving the fatigue strength of the degassing processed cast aluminum alloys.

Preliminary Fatigue Tests on Concrete Exposure to Temperature of up to 300°C

2002 ◽  
Vol 4 (4) ◽  
pp. 197-201 ◽  
Author(s):  
Xingang Zhou ◽  
John Zhang
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Test Results ◽  
Micro Cracks ◽  
Compressive Strength Of Concrete ◽  
Repeated Load

Micro-cracks in the vicinity of paste-aggregate interfaces and in the paste itself can be induced when concrete is exposed to elevated temperatures in the range 100°C-300°C. Although with increase of temperature, the strength of concrete becomes more and more influenced by the growing number of micro-cracks, the compressive strength of concrete at an elevated temperature lower than 300°C is almost the same of concrete at room temperature. Under repeated load, those microcracks caused by temperature would propagate, enlarge and become linked up, as a result, the fatigue behavior of concrete would decrease. In this paper, tests have been carried out to study the fatigue behavior of concrete after exposure to elevated temperatures of up to 300°C. Test results have shown that the reduction of fatigue strength of concrete is remarkable.

Elevated Temperature Fatigue Life Investigation of Aluminium Alloy based on the Predicted S-N Curve

2013 ◽  
Vol 63 (1) ◽  
Author(s):  
K. A. Zakaria ◽  
S. Abdullah ◽  
M. J. Ghazali
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Fatigue Tests ◽  
Maximum Temperature ◽  
Stress Control ◽  
Temperature Regimes ◽  
Engine Mount ◽  
Load Sequence

This paper discusses a methodology used to predict the stress-life (S-N) curve at elevated temperatures based on the normal S-N curve. Fatigue tests were performed under stress control at room temperature in accordance with the ASTM E466 standard to obtain a normal S-N curve. In addition, the tests were performed at both room and elevated temperatures using constant-amplitude, high-to-low sequence, and low-to-high sequence loadings to investigate the effect of the load sequence at elevated temperatures on fatigue life. Three elevated temperature regimes at 70 to 250°C were chosen based on the maximum temperature of the engine mount bracket and the cylinder head that can be reached during normal service. The results show that the fatigue lives were significantly affected by the load sequences at both room and elevated temperatures. Furthermore, the existing fatigue data obtained at elevated temperatures can be used to predict the corresponding S-N curves. 

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

Experimental Study on the Mechanical Property and Forming Limit of Magnesium Sheet at Elevated Temperatures

2009 ◽  
Author(s):  
Y. Huang ◽  
J. Huang ◽  
J. Cao
Keyword(s):  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Tensile Tests ◽  
Alloy Sheet ◽  
Dome Height ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Magnesium Sheet

Magnesium alloy sheet has received increasing attention in automotive and aerospace industries. It is widely recognized that magnesium sheet has a poor formability at room temperature. While at elevated temperature, its formability can be dramatically improved. Most of work in the field has been working with the magnesium sheet after annealed around 350°C. In this paper, the as-received commercial magnesium sheet (AZ31B-H24) with thickness of 2mm has been experimentally studied without any special heat treatment. Uniaxial tensile tests at room temperature and elevated temperature were first conducted to have a better understanding of the material properties of magnesium sheet (AZ31B-H24). Then, limit dome height (LDH) tests were conducted to capture forming limits of magnesium sheet (AZ31B-H24) at elevated temperatures. An optical method has been introduced to obtain the stress-strain curve at elevated temperatures. Experimental results of the LDH tests were presented.

Fatigue Behavior of a 22Cr-20Ni-18Co-Fe Alloy at Elevated Temperatures

1994 ◽  
Vol 116 (1) ◽  
pp. 54-61 ◽  
Author(s):  
T. H. Krukemyer ◽  
A. Fatemi ◽  
R. W. Swindeman
Keyword(s):  
Experimental Investigation ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Frequency Separation ◽  
Isothermal Fatigue ◽  
Deformation Properties ◽  
Fatigue Data ◽  
Haynes Alloy

An experimental investigation was conducted on Haynes Alloy 556 to study the fatigue behavior of the material at elevated temperatures. Fatigue tests were run at constant temperatures ranging from room temperature to 871°C with strain ranges from 0.265 to 1.5 percent resulting in lives between 102 and 106 cycles. Cyclic deformation properties were evaluated based on the fatigue data. Three fatigue life models were evaluated for their ability to predict the isothermal fatigue lives of the material. These included the Ostergren, Frequency Separation and Stress-Strain-Time models. Strengths and weaknesses of each model are discussed based on the experimental results.

Sliding Behavior of Alumina/Nickel and Alumina/Nickel Aluminide Couples at Room and Elevated Temperature

1988 ◽  
Vol 110 (4) ◽  
pp. 646-652 ◽  
Author(s):  
Peter J. Blau ◽  
Charles E. DeVore
Keyword(s):  
Elevated Temperature ◽  
Friction Coefficient ◽  
Nickel Aluminide ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Sliding Friction ◽  
Surface Damage ◽  
Polycrystalline Alumina ◽  
Ordered Intermetallic ◽  
Pin On Disk

Nickel aluminide alloys are ordered intermetallic compounds which show promise for elevated temperature applications, some of which involve sliding contact. The present investigation was conducted to develop an initial understanding of the unlubricated sliding behavior of a nickel aluminide alloy at room and elevated temperatures. In particular, the variations in the friction coefficient and the wear track morphology during the break-in stage and subsequent transitions were studied. Pin-on-disk experiments were conducted at room temperature and at 650° C (923° K) in air using fixed 9.5 mm diameter polycrystalline alumina balls as the pin material. To provide a comparison in behavior, nickel (Ni-200) disks were tested under the same conditions. The sliding friction coefficient of alumina on nickel aluminide was considerably higher than that for alumina on nickel at room temperature, but it was only slightly higher at 650° C. The wear was similar for both materials at room temperature, but the nickel aluminide exhibited relatively mild wear at 650° C, displaying less severe surface damage than the nickel. Work on identifying key friction and wear mechanisms and on evaluating the temperature limitations for future applications will continue.

Fatigue Properties of Aluminium Alloys for Uniaxial Cyclic Loads

2014 ◽  
Vol 598 ◽  
pp. 13-19
Author(s):  
Ewelina Böhm ◽  
Tadeusz Łagoda
Keyword(s):  
Fatigue Strength ◽  
Chemical Composition ◽  
Aluminium Alloys ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cyclic Loads ◽  
Fatigue Characteristics

The paper presents an analysis of aluminium and its alloys in terms of fatigue strength. The paper contains information in terms of cyclic fatigue tests of aluminium alloys. On the basis of available literature data, Basquin fatigue characteristics have been designated. On their basis a comparison between chosen fatigue characteristics of aluminium alloys with different chemical composition and element percentage in the substance have been done.

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