Evaluation of the fatigue properties of high-temperature materials. Communication 2. Determination of fatigue limit for high-temperature alloys over a wide temperature range

1984 ◽  
Vol 16 (6) ◽  
pp. 854-858 ◽  
Author(s):  
A. D. Pogrebnyak ◽  
A. V. Zheldubovskii
Keyword(s):  
High Temperature ◽  
Fatigue Limit ◽  
Wide Temperature Range ◽  
Fatigue Properties ◽  
Temperature Range ◽  
High Temperature Materials ◽  
High Temperature Alloys

Comparison of High Temperature Mechanical Behaviour and Microstructure of the New Gamma–TiAl8Ta with Gamma-TiAl8Nb Alloy

2010 ◽  
Vol 72 ◽  
pp. 40-45
Author(s):  
Giuliano Angella ◽  
Valentino Lupinc ◽  
Maurizio Maldini ◽  
Giovanni Onofrio
Keyword(s):  
High Temperature ◽  
Mechanical Behaviour ◽  
Low Cycle Fatigue ◽  
Fatigue Properties ◽  
Stress Intensity Factor Range ◽  
Fatigue Crack Propagation Rate ◽  
Difference Threshold ◽  
Temperature Range ◽  
R Ratio ◽  
Significant Difference

The high temperature creep and fatigue properties of two  -TiAl base intermetallic alloys, for gas turbine components, have been investigated within the Integrated European project IMPRESS. The alloys contain 8% at. of Ta or Nb, respectively. The microstructure of both alloys was cross convoluted lamellar rather than the well known conventional lamellar, typical of the usual -TiAl. The microstructure of the Ta containing alloy was homogeneous in all the analyzed batches whilst that of the Nb alloy appeared significantly spread out from specimen to specimen. The creep properties of the alloys were investigated in the temperature range 700-850°C with applied stresses in order to have times to rupture up to about 3,000 h. The creep behaviour presented no steady state regimes, but only minima of the creep rates between significant decelerating and accelerating regimes. The minimum creep rates of the Ta alloy resulted to be significantly slower than the Niobium alloy at the same creep conditions. In low cycle fatigue at 650 and 700°C the Ta  -TiAl showed longer lives than the Nb alloy, whilst the fatigue crack propagation rate in the same temperature range did not show any significant difference. Threshold values of stress intensity factor range were accurately measured at different R ratio. The microstructures of the two alloys were analysed by scanning microscopy in order to rationalise the different mechanical behaviour.

CMOS Circuits on Silicon Carbide for High Temperature Operation

2014 ◽  
Vol 1693 ◽  
Author(s):  
David T. Clark ◽  
Robin F. Thompson ◽  
Aled E. Murphy ◽  
David A. Smith ◽  
Ewan P. Ramsay ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Wide Temperature Range ◽  
Integrated Circuit ◽  
Elevated Temperatures ◽  
Logic Circuits ◽  
Digital Logic ◽  
Cmos Integrated Circuit ◽  
Temperature Range ◽  
Simple Logic

ABSTRACTWe present the characteristics of a high temperature CMOS integrated circuit process based on 4H silicon carbide designed to operate at temperatures beyond 300°C. N-channel and P-channel transistor characteristics at room and elevated temperatures are presented. Both channel types show the expected low values of field effect mobility well known in SiC MOSFETS. However the performance achieved is easily capable of exploitation in CMOS digital logic circuits and certain analogue circuits, over a wide temperature range.Data is also presented for the performance of digital logic demonstrator circuits, in particular a 4 to 1 analogue multiplexer and a configurable timer operating over a wide temperature range. Devices are packaged in high temperature ceramic dual in line (DIL) packages, which are capable of greater than 300°C operation. A high temperature “micro-oven” system has been designed and built to enable testing and stressing of units assembled in these package types. This system heats a group of devices together to temperatures of up to 300°C while keeping the electrical connections at much lower temperatures. In addition, long term reliability data for some structures such as contact chains to n-type and p-type SiC and simple logic circuits is summarized.

scholarly journals Rapid determination of the high cycle fatigue properties of high temperature aeronautical alloys by self-heating measurements

2018 ◽  
Vol 165 ◽  
pp. 22022
Author(s):  
Vincent Roué ◽  
Cédric Doudard ◽  
Sylvain Calloch ◽  
Frédéric Montel ◽  
Quentin Pujol D’Andrebo ◽  
...  
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
High Cycle Fatigue ◽  
Rapid Determination ◽  
The Self ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Heating Method ◽  
Self Heating

The determination of high cycle fatigue (HCF) properties of a material with standard method requires a lot of specimens, and could be really time consuming. The self-heating method has been developed in order to predict S–N–P curves (i.e., amplitude stress – number of cycles to failure – probability of failure) with only a few specimens. So the time-saving advantage of this method has been demonstrated on several materials, at room temperature. In order to reduce the cost and time of fatigue characterization at high temperature, the self-heating method is adapted to characterize HCF properties of a titanium alloy, the Ti-6Al-4V (TA6V), at different temperatures. So the self-heating procedure is adjusted to conduct tests with a furnace. Two dissipative phenomena can be observed on self-heating curves. Because of this, a two-scale probabilistic model with two dissipative mechanisms is used to describe them. The first one is observed for low amplitudes of cyclic loading, under the fatigue limit, and the second one for higher amplitudes where the mechanisms of fatigue damage are activated and are dissipating more energy. This model was developed on steel at room temperature. Even so, it is used to describe the self-heating curves of the TA6V at several temperatures.

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