A new simulation approach for crack initiation, propagation and arrest in hollow cylinders under thermal shock based on XFEM

It is well known that a series of cracks running perpendicular to the cutting edge are sometimes formed on the rake face of brittle cutting tools during intermittent cutting. The cutting tool is exposed to elevated temperatures during the periods of cutting and is cooled quickly during noncutting times. It has been suggested that repeated thermal shocks to the tool during intermittent cutting generate thermal fatigue and result in the observed thermal cracks. Recently, a high speed machining technique has attracted attention. The tool temperature during the period of cutting corresponds to the cutting speed. In addition, the cooling and lubricating conditions affect the tool temperature during noncutting times. The thermal shock applied to the tool increases with increasing cutting speed and cooling conditions. Therefore, to achieve high-speed cutting, the evaluation of the thermal shock and thermal crack resistance of the cutting tool is important. In this study, as a basis for improving the thermal shock resistance of brittle cutting tools during high-speed intermittent cutting from the viewpoint of cutting conditions, we focused on the cooling conditions of the cutting operation. An experimental study was conducted to examine the effects of noncutting time on thermal crack initiation. Thermal crack initiation was found to be restrained by reducing the noncutting time. In the turning experiments, when the noncutting time was less than 10 ms, thermal crack initiation was remarkably decreased even for a cutting speed of 500 m/min. In the milling operation, the number of cutting cycles before thermal crack initiation decreased with increasing cutting speed under conditions where the cutting speed was less than 500 m/min. However, when the cutting speed was greater than 600 m/min, thermal crack initiation was restrained. We applied the minimal quantity lubrication (MQL) coolant supply to the intermittent cutting operation. The experimental results showed that the MQL diminished tool wear compared with that under the dry cutting condition and inhibited thermal crack initiation compared with that under the wet cutting condition.

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Prediction of suitable heat treatment for H13 tool steels by application of thermal shock fatigue cycle

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/13506501211011808 ◽

2021 ◽

pp. 135065012110118

Author(s):

Palani Karthikeyan ◽

Sumit Pramanik

Keyword(s):

Heat Treatment ◽

Crack Initiation ◽

Thermal Shock ◽

Tool Steel ◽

Treatment Method ◽

Industrial Applications ◽

Tool Steels ◽

H13 Steel ◽

H13 Tool Steel ◽

Cyclic Treatment

In industry, thermally shocked components lead to early failures and unexpected breakdowns during production resulting in huge losses in profit. Thus, the present study investigates the as-received, hardened and hardened and nitrogen treated H13 tool steels subjected to a thermal shock gradient similar to the actual industrial applications. The thermal shock gradients were created by using an in-house-built thermal shock fatigue cyclic treatment machine. The effect of thermal shock fatigue cyclic treatments at 1000 and 2000 thermal shock cycles in hot and molten metal chambers was noticed. All the thermal shock fatigue cyclic-treated samples were analysed by hardness, X-ray diffraction, microscopy and magnetic tests. The interesting changes in hardness, distorted crystal structure and crack initiation were found to be different for differently treated H13 tool steel specimens. The molten aluminium was more prone to stick to the surface of as-received as well as hardened and nitrogen treated steel compared to the hardened H13 steel specimens, which would delay the crack initiation. The wear resistance properties of the hardened H13 steel specimens were found to be higher than as-received and hardened and nitrogen treated H13 steel specimens after thermal shock fatigue cyclic treatment. The loss in magnetic properties was significant for the hardened and hardened and nitrogen treated samples compared to as-received H13 tool steel specimens. Therefore, the present 1000 and 2000 thermal fatigue cycles for 30 s at 670 °C would be worthy to predict the proper heat treatment method to design the parameters as well as the life of die-casting components and to help in the economical production of casting.

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Thermoelectroelastic Responses in Orthotropic Piezoelectric Hollow Cylinders Subjected to Thermal Shock and Electric Excitation

Journal of Reinforced Plastics and Composites ◽

10.1177/0731684405048834 ◽

2005 ◽

Vol 24 (10) ◽

pp. 1085-1103 ◽

Cited By ~ 5

Author(s):

H. L. Dai ◽

X. Wang ◽

Q. H. Dai

Keyword(s):

Thermal Shock ◽

Electric Excitation ◽

Hollow Cylinders

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

Journal of Applied Mechanics ◽

10.1115/1.4051592 ◽

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.

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Probabilistic Structural Integrity Analysis of Reactor Pressure Vessels During Pressurized Thermal Shock Events

Journal of Pressure Vessel Technology ◽

10.1115/1.4025615 ◽

2013 ◽

Vol 136 (1) ◽

Author(s):

Koichi Masaki ◽

Jinya Katsuyama ◽

Kunio Onizawa

Keyword(s):

Crack Initiation ◽

Thermal Shock ◽

Structural Integrity ◽

Fracture Probability ◽

Pressure Vessels ◽

Sensitivity Analyses ◽

Conditional Probabilities ◽

Integrity Assessment ◽

Pressurized Thermal Shock ◽

Reactor Pressure

To apply a probabilistic fracture mechanics (PFM) analysis to the structural integrity assessment of a reactor pressure vessel (RPV), a PFM analysis code has been developed at JAEA. Using this PFM analysis code, pascal version 3, the conditional probabilities of crack initiation (CPIs) and fracture for an RPV during pressurized thermal shock (PTS) events have been analyzed. Sensitivity analyses on certain input parameters were performed to clarify their effect on the conditional fracture probability. Comparisons between the conditional probabilities and the temperature margin (ΔTm) based on the current deterministic analysis method were made for various model plant conditions for typical domestic older types of RPVs. From the analyses, a good correlation between ΔTm and the conditional probability of crack initiation was obtained.

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Crack initiation and propagation in thermal shock fatigue of stainless steel.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.52.672 ◽

1986 ◽

Vol 52 (475) ◽

pp. 672-676

Author(s):

Junichi OKAMOTO ◽

Masao SHIMIZU

Keyword(s):

Stainless Steel ◽

Crack Initiation ◽

Thermal Shock ◽

Crack Initiation And Propagation ◽

Initiation And Propagation

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Geometry Effect on the Thermal Shock Response of Al2O3/ZrO2 Multilayered Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.333.251 ◽

2007 ◽

Vol 333 ◽

pp. 251-254

Author(s):

Raúl Bermejo ◽

Peter Supancic ◽

Tanja Lube

Keyword(s):

Crack Initiation ◽

Thermal Shock ◽

Architectural Design ◽

Thermal Stresses ◽

Slip Casting ◽

Experimental Tests ◽

Element Model ◽

Distribution Profile ◽

Geometry Effect ◽

Shock Response

In this work, the geometry effect on the thermal shock behaviour of a nine layered Al2O3- 5%tZrO2/Al2O3-30%mZrO2 ceramic fabricated by slip casting has been studied. A finite element model has been used to estimate the magnitude and location of the maximum thermal stresses in the layered material as well as the influence of the variation of this layered architectural design in the thermal shock crack initiation and extend throughout the specimens of study. Experimental tests on various samples have been carried out to validate the model. The residual stress distribution profile in the laminate, due to the elastic mismatch of the different layers along with the zirconia phase transformation on the Al2O3-30%mZrO2 layers, conditions the thermal shock response of the material. It is demonstrated how the variation of the outer most layer thickness in the laminates modifies the stress state in the surface, affecting the thermal shock crack initiation.

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