Dynamic Fracture Toughness Evaluation of Structural Steels Based on the Local Approach

Minami, Fumiyoshi; Hashida, Tomoyuki; Toyoda, Masao; Morikawa, Jun; Ohmura, Takeshi; Arimochi, Kazushige; Konda, Noboru

doi:10.2534/jjasnaoe1968.1998.184_453

Cited by 16 publications

(7 citation statements)

References 5 publications

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“…Here, decreasing R means increasing ε or decreasing T, or both. This result is consistent with previous research reports on steels and ductile cast iron 27,28) . However, σ b,max becomes smaller below the critical value R σ for 3.7 and 4%Si irons, because completely brittle fracture occurs below R σ .…”

Section: Application Of Strain Rate-temperature Parameter Tosupporting

confidence: 94%

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Influence of Silicon Content, Strain Rate and Temperature on Toughness and Strength of Solid Solution Strengthened Ferritic Ductile Cast Iron

Ikeda¹,

Umetani²,

Kai³

et al. 2016

Mater. Trans.

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High Silicon Solid Solution Strengthened Ferritic Ductile Cast Iron possesses advantages, such as better combination of strength-elongation, higher fatigue strength, smaller section thickness sensitivity, higher machinability etc., over conventional ferrite-pearlite type ductile cast iron. However, industrial application of high Si ductile cast iron is still very limited, because of the lower Charpy impact value at room temperature. As the toughness of iron strongly depends on the strain rate as well as temperature, dynamic three-point bending tests are conducted on 3 4%Si ferritic ductile cast iron at stroke speed of 10 −3 10 2 mm/s, and at −20 22 C. The relations of the crack initiation energy E i , the crack propagation energy E p , the total absorbed energy E t and the maximum bending stress σ b,max to the strain rate show abrupt dropping of these characteristic values at critical strain rate, depending on silicon content and test temperature. σ b,max keeps increasing with increasing strain rate ε as far as the fracture origin is ductile, it slightly decreases over ε σ = ε f D where the dimple fracture completely disappears. σ b,max , E t and E i of each silicon iron is well expressed in relation to strain rate-temperature parameter R, T ln(A/ε ). The critical R values for E t , E i , and σ b,max (R t , R i and R σ ) decrease linearly with decreasing the silicon content of iron. The critical value for σ b,max (R σ ) is lowest, indicating R σ gives a wider design tolerance.

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Section: Application Of Strain Rate-temperature Parameter Tosupporting

confidence: 94%

“…(3), has been introduced to explain the in uence of ε and T on the tensile strength as well as yield stress of steel [25][26][27] , where T = temperature, A = 10 8 s…”

Section: Application Of Strain Rate-temperature Parameter Tomentioning

confidence: 99%

Influence of Silicon Content, Strain Rate and Temperature on Toughness and Strength of Solid Solution Strengthened Ferritic Ductile Cast Iron

Ikeda¹,

Umetani²,

Kai³

et al. 2016

Mater. Trans.

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“…APPROACH FOR FRACTURE UNDER DYNAMIC LOADING [26] It is common that dynamic fracture toughness obtained by test under high speed loading deteriorates, compared with the ordinal static fracture toughness. Fig.…”

Section: Applicability Of the Weibull Stressmentioning

confidence: 99%

“…Fig. 13 gives typical examples of the effect of strain rate on critical CTODs obtained by CT-type CTOD tests under static and dynamic loading [26]. The reason for the deterioration is mainly due to the increase in strength of steels under dynamic loading, which brings about an increase in stress level in the vicinity of the crack tip.…”

Section: Applicability Of the Weibull Stressmentioning

confidence: 99%

Transferability of fracture mechanics parameters to fracture performance evaluation of welds with mismatching

Toyoda

2002

Progress Structural Eng Maths

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In order to evaluate fracture performance of steel welded structures, the fracture mechanics approach has been adopted. However, it has frequently been pointed out that conventional fracture mechanics parameters are not necessarily applicable to all cases. This inconsistency is due to the difference of stress-strain behaviour depending on plastic constraints in the vicinity of a crack tip between the fracture toughness testing specimen and the practical structures. Accordingly, the transferability of the fracture-controlling parameter and a new appropriate procedure is discussed.In the welded joint, moreover, the mismatching of metallurgical/mechanical properties inevitably exists. Mismatching in strength also results in considerable change in plastic constraints. It is very important that the combined consideration of both strength mismatching and transferability for critical assessment of the structural integrity with regard to the unstable fracture of steel welded structures.The present paper summarizes the recent activities on transferability of fracture toughness data to fracture assessment in structural welded joints, with particular reference to mechanical heterogeneity observed in welded joints.

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“…C：Specific heat, ρ：Density, λ：Thermal conductivity, α L ：Coefficient of liner expansion It is reported that the critical Weibull stress is independent of the specimen type, size 12) , loading rate 13) and strength mismatch in 3PB specimen 4) . On the basis of these features, V E and δ cr for joint specimen were evaluated by the following procedure:…”

Section: Strength Mismatch Effect On Toughness Valuesmentioning

confidence: 99%

Strength Mismatch Effects on Charpy Absorbed Energy and CTOD Fracture Toughness

Ito

Takashima

Minami

2017

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY

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In order to examine the difference between the sensitivity of Charpy absorbed energy, V E, and critical CTOD, δ cr , to strength mismatch in welds, the numerical analysis was conducted. This study adopted the evaluation method based on the Weibull stress criterion for calculation of V E and δ cr assuming that the critical Weibull stress at brittle fracture is independent of the strength mismatch as well as the loading rate. This analysis showed that the V E and δ cr decreased as the location of the V-notch or crack approached welded interface. The change in V E was larger than that in δ cr , because the strength mismatch caused acceleration of strain rate and decrease in temperature rise near the V-notch as well as plastic constraint. This result indicates that the sensitivity of the V E and δ cr to strength mismatch is different depending on the loading rate.

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Dynamic Fracture Toughness Evaluation of Structural Steels Based on the Local Approach

Cited by 16 publications

References 5 publications

Influence of Silicon Content, Strain Rate and Temperature on Toughness and Strength of Solid Solution Strengthened Ferritic Ductile Cast Iron

Influence of Silicon Content, Strain Rate and Temperature on Toughness and Strength of Solid Solution Strengthened Ferritic Ductile Cast Iron

Transferability of fracture mechanics parameters to fracture performance evaluation of welds with mismatching

Strength Mismatch Effects on Charpy Absorbed Energy and CTOD Fracture Toughness

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