Temperature Dependence Of Toughness Research Articles

The Effect of Oxygen on the Brittle-to-Ductile Transition in Silicon Single Crystals

The brittle-to-ductile transition (BDT) in Czochralski (CZ) grown silicon single crystals and floating-zone (FZ) grown silicon single crystals was investigated by three-point bending. The temperature dependence of the apparent fracture toughness was measured in three different cross-head speeds. It was found that the BDT temperature in the CZ silicon crystal was higher than that in FZ silicon crystal, suggesting that the solute oxygen decreases dislocation mobility. However, the activation energies obtained from the strain rate dependence of the BDT temperatures were nearly the same in both the CZ and FZ silicon crystals, indicating that the dislocation mobility is not influenced by the solute oxygen. In this paper, the origin of the difference in the BDT temperature is discussed, focusing the role of the solute oxygen on the dislocation glide.

The Effect of Size of Testing Samples on Notch Toughness of Structural Steels

We analyze notch toughness assessment of full scale testing samples (FS) form the upper bound toughness of sub-sized (SS) samples of structural carbon-manganese steels. The relations proposed by Schindler (2000) are in good agreement with experimental data. Empirical proportionality constant q* = 0.54 between notch toughness of full scale and sub-sized samples of studied structural steels agrees well with theoretically estimated constant q* = 0.50-0.54. More precise knowledge of the size effect of testing samples on temperature dependence of notch toughness requires an analysis of scatter in experimental data.

Fracture process of a low carbon low alloy steel relevant to charpy toughness at ductile-brittle fracture transition region

The fracture process that determines the Charpy energy at the ductile-brittle transition region was investigated by means of the instrumented Charpy test and fractographic analysis with a low carbon low alloy steel subjected to different control-rolling conditions. The decomposition of a Charpy energy into the energies dissipated in the course of the notch-tip blunting, stable crack growth, and brittle crack propagation is unique irrespective of the testing temperatures and specimen series. Toughness level can be divided into four regions according to the pre-dominating fracture process. The temperature dependence of toughness and effects of the an-isotropy of a specimen originates in the brittle fracture initiation stage rather than the resistance against the notch-tip blunting or stable crack growth. From fractographic examination referring to the stress analyses, it is discussed that the brittle fracture initiation is controlled by the local deformation microstructures in the plastic zone together with the stress field ahead of the notch or the stable crack front.

Temperature dependence of the dynamic fracture toughness of the alloy incoloy 800 after Cold work

Temperaturabhangigkeit der dynamischen Bruchzahigkeit an der Legierung Incoloy 800 nach Kaltverformung Angerissen ISO-V-Proben der Eisen-Nickel-Basis-Legierung Incoloy 800 im Anlieferungszustand und nach Kaltverformung wurden mit Hilfe eines instrumentierten Pendelschlagwerkes im Temperaturintervall 293 ≤ T/K ≤ 1223 untersucht. Die spezifischen Schlagenergien wurden mit Hilfe des Schleppzeigers, der Integration des Kraft-Zeit-und des Kraft-Weg-Diagrammes ermittelt. In allen Fallen war die Ubereinstimmung ausgezeichnet. Die spezifischen Schlagenergien und die Impulse wurden sowohl mit der Versuchstemperatur als auch mit dem Verformungsgrad korreliert. Die dynamische Bruchzahigkeit wurde mit Hilfe der aquivalenten Energie-Naherung ermittelt. In allen Fallen wurde ein deutliches Absinken der mechanischen Eigenschaften zwischen dem Anlieferungszustand und 5% Kaltverformung gefunden. Die Temperaturabhangigkeit der Schlagenergien zeigt einen deutlichen Anstieg der Werte zwischen Reumtemperatur und 673 K. Dieser Anstieg wird nach Kaltverformung deutlich reduziert. Die dynamische Bruchzahigkeit sinkt mit steigender Temperatur. Die Bruchflachen zeigen klar das elasto-plastische Bruchverhalten des Materials im untersuchten Temperaturbereich.

Low temperature and strain rate dependence of fracture stress and fracture toughness on thin Fe40Ni40B20 amorphous ribbon

Low temperature and strain rate dependence of fracture stress and fracture toughness on thin Fe40Ni40B20 amorphous ribbon

A533B鋼の延・脆性遷移温度域破壊における靱性のばらつきと温度依存性

A533B鋼の延・脆性遷移温度域破壊における靱性のばらつきと温度依存性

Temperature dependence of impact toughness in Al–Li–Cu–Mg–Zr alloys

AbstractThe dependence on temperature of the impact toughness in Al–Li–Cu–Mg–Zr alloys was investigated focusing on the low temperature impact toughness. The impact toughness of Al–Li–Cu–Mg–Zr alloys in the low temperature region (≤ 423 K) increased with decreasing temperature. Laminated cracks, the number of which increased with the increase in impact toughness in the low temperature region, were observed and it was suggested that the appearance of these cracks resulted in part of the increase of the impact toughness of this alloy. The spectra of potassium and sodium were detected from the fracture surface of a specimen tested at room temperature. This indicates that a low melting point metal phase seems to affect the impact toughness near room temperature, i.e. this phase seems to produce the liquid metal embrittlement locally at the grain boundary.MST/787

Kinetics of thermal aging and its effect on the proneness of hull steels to brittle failure

1. The hull steels 10GN2MFA and 15Kh2NMFA-A have little proneness to aging) this is in keeping with the requirements that modern shell materials have to fulfill. 2. The activation energy of the process of thermal aging (Q=70–80 kJ/mole) is close to the activation energy of diffusion of carbon in ferrite. The magnitude of the activation energy, and also the nature of the change of strength and fracture toughness make it reasonable to assume that in the steels 15Kh2NMFA-A and 10GN2MFA the aging process is determined by the state of the carbide phase. 3. The use of the constant in the Khollomon equation (α=3.5–4.5), which was experimentally established for the temperature range 250–400°C, and 10GN2MFA upon aging. 4. Aging for up to 6500 h causes a shift of the temperature dependence of the fracture toughness of steel 15Kh2NMFA-A into the range of higher temperatures, and it also increases fracture toughness at low temperatures (below −100°C).

ガラスマット強化プラスチックの動的破壊じん性

The dynamic fracture toughness values of glass mat reinforced polyester laminates were compared with the analytical values of dynamic stress intensity factor, and their temperature dependence was discussed using instrumented Charpy test results. The results obtained are as follows:(1) The ratio of dynamic fracture toughness KId to the static one KIS, which was obtained by the finite element method, decreased with time by oscillating around one, when the load increased at a constant rate. The ratio of KId/KIS was between 0.99 and 1.1, when the loading speed was about 0.55kgf/μs and KIS was greater than 30kgf/mm3/2 for EW test specimens, and when the speed was about 0.35kgf/μs and KIS was greater than 20kgf/mm3/2 for FW test specimens. The difference between the dynamic fracture toughness values obtained by the static K-calibration using the maximum load and by the dynamic K-calibration was smaller than the variation of measured values.(2) The dynamic fracture toughness values of EW specimens decreased slowly as the temperature became higher, while those of FW specimens were about constant at temperatures below 60°C. The toughness values of both specimens decreased rapidly as the temperature became higher than the thermal deformation temperature of resin (about 90°C). This temperature dependence of toughness was different from that of specific absorbed energy.