scholarly journals Mechanisms of Oxidation Degradation of Cr12 Roller Steel during Thermal Fatigue Tests

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 450 ◽  
Author(s):  
David Bombač ◽  
Marius Gintalas ◽  
Goran Kugler ◽  
Milan Terčelj
Keyword(s):  
Surface Layer ◽  
Thermal Stress ◽  
Thermal Fatigue ◽  
Thermal Load ◽  
Oxidation Behavior ◽  
Fatigue Tests ◽  
Qualitative Assessment ◽  
Propagation Mode ◽  
Roll Surface ◽  
Oxidation Degradation

Degradation by the penetration of oxidation into the Cr12 roller steel is evaluated during thermal fatigue tests in the laboratory in the temperature range of 500–700 °C. A qualitative assessment is carried out with regard to the thermal load, the microstructure and the test temperature. The results show that the specific properties of the microstructure with respect to thermal stress and temperature have a significant influence on the oxidation behavior as well as on the crack propagation mode and crack growth. The conditions that lead to an increase in the oxidation rate and thus to premature and sudden local chipping of the roll surface layer are analyzed and explained.

Induction of preset thermally stressed states in thermal fatigue tests: Choice of testing conditions and geometry of specimens

1997 ◽  
Vol 29 (4) ◽  
pp. 369-379
Author(s):  
G. N. Tretyachenko ◽  
B. S. Karpinos ◽  
V. G. Barilo ◽  
N. G. Solovyeva
Keyword(s):  
Thermal Fatigue ◽  
Fatigue Tests ◽  
Testing Conditions ◽  
Thermally Stressed

Mechanism of crack initiation and propagation of re-entrant auxetic honeycombs under thermal shock

2021 ◽  
pp. 1-13
Author(s):  
Zheng Li ◽  
B.L. Wang ◽  
Kaifa Wang
Keyword(s):  
Cell Wall ◽  
Thermal Stress ◽  
Crack Initiation ◽  
Thermal Shock ◽  
Thermal Load ◽  
Continuum Model ◽  
Micro Model ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Critical Thermal Load

Abstract Thermal shock multiple cracking behaviors of re-entrant auxetic honeycombs with a negative Poisson's ratio are investigated, and the crack initiation and propagation behavior are discussed. An effective macro continuum model is developed to detect the effects of cracking density and microstructures of auxetic honeycombs on the thermal stress and intensity. The microscale tensile stresses in the struts ahead of the crack as functions of the corresponding thermal stress intensity factor (SIF) at the macroscale are evaluated by employing a macro-micro model. Then, a lower-bound method is proposed to assess the critical thermal load of auxetic honeycombs by combining the macro-micro model and the macro continuum model. A significant increase in both transient thermal stress and intensity as the growing cell-wall angle is demonstrated. Results for the maximum thermal SIF as well as the maximum tensile stress in the middle of cracks are calculated as functions of crack density and length. With the identical SIF, the microscale tensile stresses ahead of the crack in honeycombs with smaller cell-wall angles are greater than that in mediums with larger angles due to the more significant crack tip opening displacement. Critical thermal load prediction reveals that the honeycombs with smaller cell-wall angles generally possess more excellent thermal shock resistance. Also, the varying failure modes of different auxetic honeycomb strips under specific thermal load are predicted. The corresponding crack initiation and propagation mechanisms are revealed.

Fatigue/Creep Interactions in Ni3Al-Base Alloys

1988 ◽  
Vol 133 ◽  
Author(s):  
G. M. Camus ◽  
D. J. Duquette ◽  
N. S. Stoloff
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Frequency Effect ◽  
Propagation Mode ◽  
Crack Blunting ◽  
Fatigue Crack Growth Test

ABSTRACTStress-controlled fatigue tests and fatigue crack growth rate tests respectively have been carried out on two Ni3Al Cr/Zr alloys, IC 218 at 600°C and 800°C, and IC 221 at 800°C, in vacuum, at various test frequencies. Decreasing the test frequency and/or increasing the temperature leads to a decrease in the number of cycles to failure, and a gradual disappearance of a fatigue fracture zone. In fatigue crack propagation tests, the crack growth rate only decreases at the lowest frequency and remains constant in the major part of the frequency range investigated. The fatigue propagation mode in all cases is intergranular. These trends are shown in both cases to be related to a true creep component but, under fatigue crack growth test conditions, crack blunting intervenes gradually as the frequency is decreased, leading therefore to a less severe frequency effect.

Thermal Fatigue Characteristics of Heat-Resisting Stainless Steel for Automotive Exhaust

2007 ◽  
Vol 539-543 ◽  
pp. 4944-4949 ◽  
Author(s):  
Tae Kwon Ha ◽  
Hwan Jin Sung
Keyword(s):  
Thermal Fatigue ◽  
Stainless Steels ◽  
Fatigue Property ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Automotive Exhaust ◽  
Load Relaxation ◽  
Temperature Ranges ◽  
Fatigue Characteristics ◽  
Efficiency And Reliability

Thermal fatigue is a complex phenomenon encountered in materials exposed to cyclically varying temperatures in the presence or absence of external load. Continually increasing working temperature and growing need for greater efficiency and reliability of automotive exhaust require immediate investigation into the thermal fatigue properties especially of high temperature stainless steels. In this study, thermal fatigue properties of 304 and 429EM stainless steels have been evaluated in the temperature ranges of 200-800oC and 200-900oC. Systematic methods for control of temperatures within the predetermined range and measurement of load applied to specimens as a function of temperature during thermal cycles have been established. Thermal fatigue tests were conducted under fully constrained condition, where both ends of specimens were completely fixed. Thermal fatigue property of STS 304 was superior to that of STS 429EM. Load relaxation behavior at the temperatures of thermal cycle was closely related with the thermal fatigue property.

Thermal-fatigue tests of restraned combustor-cooling tubes

1967 ◽  
Vol 7 (6) ◽  
pp. 256-264 ◽  
Author(s):  
L. R. Avery ◽  
G. S. Carayanis ◽  
G. L. Michky
Keyword(s):  
Thermal Fatigue ◽  
Fatigue Tests

scholarly journals Simulation of Thermal Stress and Fatigue Life Prediction of High Speed Steel Work Roll during Hot Rolling Considering the Initial Residual Stress

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 966 ◽  
Author(s):  
Kejun Hu ◽  
Fuxian Zhu ◽  
Jufang Chen ◽  
Nao-Aki Noda ◽  
Wenqin Han ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Fatigue Life ◽  
Hot Rolling ◽  
Work Roll ◽  
Roll Surface ◽  
Initial Residual Stress ◽  
Thermal Fatigue Life ◽  
Cooling Conditions ◽  
Roll Temperature

Considerable residual stress is produced during heat treatment. Compressive residual stress at the shell is conductive to improving the thermal fatigue life of a work roll, while tensile stress in the core could cause thermal breakage. In hot rolling, thermal stress occurs under the heating-cooling cycles over the roll surface due to the contact with the hot strip and water spray cooling. The combination of thermal stress and residual stress remarkably influences the life of a work roll. In this paper, finite element method (FEM) simulation of hot rolling is performed by treating the residual stress as the initial stress. Afterwards, the effects of the initial roll temperature and cooling conditions on thermal stress considering the initial residual stress are discussed. Lastly, the thermal fatigue life of a work roll is estimated based on the strain life model. The higher initial roll temperature causes a higher temperature but a lower compressive thermal stress at the roll surface. The surface temperature and compressive stress increase significantly in the insufficient cooling conditions, as well as the center tensile stress. The calculation of the fatigue life of a work roll based on the universal slopes model according to the 10% rule and 20% rule is reasonable compared with experimental results.

scholarly journals Characterization of Roll Bite Heat Transfers in Hot Steel Strip Rolling and their Influence on Roll Thermal Fatigue Degradation

2013 ◽  
Vol 554-557 ◽  
pp. 1555-1569 ◽  
Author(s):  
Nicolas Legrand ◽  
Daniel Weisz-Patrault ◽  
Jaroslav Horský ◽  
Tomáš Luks ◽  
Nathalie Labbe ◽  
...  
Keyword(s):  
Heat Flux ◽  
Transfer Coefficient ◽  
Thermal Fatigue ◽  
Hot Rolling ◽  
Temperature Sensor ◽  
Roll Surface ◽  
Degradation Model ◽  
Heat Transfers ◽  
Hot Rolling Conditions ◽  
Roll Bite

A temperature sensor with a thermocouple placed at ~0.5 mm from roll surface is used in hot rolling conditions to evaluate by inverse calculation heat transfers in the roll bite. Simulation analysis in industrial hot rolling conditions with short contact lengths (e.g. short contact times) and high rolling speeds (7 m./sec.) show that the temperature sensor + inverse analysis with a high acquisition frequency (> 1000 Hz) is capable to predict with a good accuracy (5 to 10% error) the roll bite peak of temperature as well as the roll surface temperature evolution all around the roll rotation. However as heat flux is more sensitive to noise measurement, the peak of heat flux in the bite is strongly under-estimated (40% error) by the inverse calculation and thus only an average roll bite heat flux could be expected from the sensor (these simulation results will be verified with an industrial trial that is being prepared). Rolling tests on a pilot mill with low rolling speeds (from 0.3 to 1.5 m./sec.) and strip reductions varying from 10 to 40% have been performed with the temperature sensor. Analysis of the tests by inverse calculation show that at low speed (<0.5 m="" sec="" and="" large="" contact="" lengths="" reduction:="" 30="" to="" 40="" the="" roll="" bite="" peak="" of="" heat="" flux="" reconstructed="" by="" inverse="" calculation="" is="" correct="" at="" higher="" speeds="" 1="" 5="" smaller="" reduction="" :="" 10-20="" reconstruction="" incorrect:="" in="" under-estimated="" though="" its="" average="" value="" analysis="" reveals="" also="" that="" transfer="" coefficient="" htc="" sub="">roll-bite (characterizing heat transfers between roll and strip in the bite) is not uniform along the roll bite but is proportional to the local rolling pressure. Finally, based on the above results, simulations with a roll thermal fatigue degradation model in industrial hot rolling conditions show that the non uniform roll bite Heat Transfer Coefficient HTCroll-bite may have in certain rolling conditions a stronger influence on roll thermal fatigue degradation than the equivalent (e.g. same average) HTCroll-bite taken uniform along the bite. Consequently, to be realistic the roll thermal fatigue degradation model has to incorporate this non uniform HTCroll-bite.

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