The Initiation and Propagation of Ductile Fracture in Low Strength Steels

1976 ◽  
Vol 98 (1) ◽  
pp. 37-46 ◽  
Author(s):  
G. Green ◽  
J. F. Knott
Keyword(s):  
Ductile Fracture ◽  
Work Hardening ◽  
Inclusion Content ◽  
Initiation And Propagation ◽  
Ductile Fractures ◽  
Work Hardening Rate ◽  
Low Strength ◽  
The Difference

The effects of work hardening rate and inclusion content on the initiation and propagation of ductile fracture in low strength steels have been investigated. A model has been proposed based on these results, which describes the difference between the energy required for initiation and propagation of ductile fractures in such steels.

scholarly journals A Strategy for Dimensionality Reduction and Data Analysis Applied to Microstructure–Property Relationships of Nanoporous Metals

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1822
Author(s):  
Norbert Huber
Keyword(s):  
Machine Learning ◽  
Dimensionality Reduction ◽  
Work Hardening ◽  
Large Range ◽  
Scaling Law ◽  
Principal Component ◽  
Underlying Structure ◽  
Structure Property ◽  
Work Hardening Rate ◽  
Nanoporous Metals

Nanoporous metals, with their complex microstructure, represent an ideal candidate for the development of methods that combine physics, data, and machine learning. The preparation of nanporous metals via dealloying allows for tuning of the microstructure and macroscopic mechanical properties within a large design space, dependent on the chosen dealloying conditions. Specifically, it is possible to define the solid fraction, ligament size, and connectivity density within a large range. These microstructural parameters have a large impact on the macroscopic mechanical behavior. This makes this class of materials an ideal science case for the development of strategies for dimensionality reduction, supporting the analysis and visualization of the underlying structure–property relationships. Efficient finite element beam modeling techniques were used to generate ~200 data sets for macroscopic compression and nanoindentation of open pore nanofoams. A strategy consisting of dimensional analysis, principal component analysis, and machine learning allowed for data mining of the microstructure–property relationships. It turned out that the scaling law of the work hardening rate has the same exponent as the Young’s modulus. Simple linear relationships are derived for the normalized work hardening rate and hardness. The hardness to yield stress ratio is not limited to 1, as commonly assumed for foams, but spreads over a large range of values from 0.5 to 3.

Effect of Flaw Dimensions on Ductile Fracture Behavior of Non-Aligned Multiple Flaws in a Plate

2011 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Koichi Saito
Keyword(s):  
Ductile Fracture ◽  
Flat Plate ◽  
Fracture Behavior ◽  
Maximum Load ◽  
Surface Flaws ◽  
Fracture Tests ◽  
The Difference ◽  
Almost All ◽  
Maximum Minimum

The fitness-for-service codes require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw proximity rule. Worldwide, almost all such codes provide their own proximity rule, often with unclear technical bases of the application of proximity rule to ductile or fully plastic fracture. In particular, the effect of flaw dimensions of multiple surface flaws on fully plastic fracture of non-aligned multiple flaws had not been clear. To clarify the effect of the difference of part through-wall and through-wall flaws on the behavior of fully plastic fracture, the fracture tests of flat plate specimens with non-aligned multiple part through-wall flaws were conducted. When the flaw depth a was shallow with 0.4 in ratio of a to thickness t, the maximum load Pmax occurred at penetration of multiple flaws and the effect of vertical distance of non-aligned multiple flaws H on Pmax was not so significant. However, when flaw depth was deep with 0.8 in a/t, Pmax occurred after penetration of flaws and the effect of H on Pmax could be seen clearly. It was judged that the through-wall flaw tests were appropriate for discussion of the effect of H on Pmax and the alignment rule of multiple flaws. In addition, in order to clarify the appropriate length parameter to estimate Pmax of test specimens with dissimilar non-aligned through-wall multiple flaws, the fracture tests of plate specimens were also conducted. The effect of different flaw length on Pmax was discussed with maximum, minimum and averages of dissimilar non-aligned multiple flaw lengths. Experimental results showed that the maximum length lmax would be an appropriate length parameter to estimate Pmax, when the non-aligned multiple through-wall flaws were dissimilar.

The mechanism of work-hardening and slip-band formation

1957 ◽  
Vol 242 (1229) ◽  
pp. 147-159 ◽  
Keyword(s):  
Single Crystals ◽  
Slip Band ◽  
Work Hardening ◽  
Stage I ◽  
Polycrystalline Materials ◽  
Temperature Dependent ◽  
Band Formation ◽  
Slip Bands ◽  
Three Stages ◽  
The Difference

A summary is given of some present ideas on the mechanism of work-hardening of single crystals and polycrystalline materials. In particular, the difference is stressed between the three stages of hardening: stage I, or easy glide; stage II, the region of rapid hardening accompanied by short slip lines; and stage III, the region of slow or parabolic hardening which is temperature-dependent and in which long slip bands are formed.

New method for measuring the non-elastic work-hardening rate of solid polymers

1992 ◽  
Vol 27 (8) ◽  
pp. 2173-2179 ◽  
Author(s):  
Ph. Fran�ois ◽  
D. Melot ◽  
J. M. Lefebvre ◽  
B. Escaig
Keyword(s):  
Work Hardening ◽  
New Method ◽  
Solid Polymers ◽  
Work Hardening Rate

Recent Results on the Elasticity Theory of Inclusions

1994 ◽  
Vol 47 (1S) ◽  
pp. S10-S17 ◽  
Author(s):  
Jin H. Huang ◽  
T. Mura
Keyword(s):  
Composite Materials ◽  
Work Hardening ◽  
Strain Energy ◽  
Volume Fraction ◽  
Exact Formula ◽  
Stress And Strain ◽  
Inclusion Problems ◽  
Elastic Fields ◽  
Work Hardening Rate ◽  
Minimum Strain Energy

A method drawing from variational method is presented for the purpose of investigating the behavior of inclusions and inhomogeneities embedded in composite materials. The extended Hamilton’s principle is applied to solve many problems pertaining to composite materials such as constitutive equations, fracture mechanics, dislocation theory, overall elastic moduli, work hardening and sliding inclusions. Especially, elastic fields of sliding inclusions and workhardening rate of composite materials are presented in closed forms. For sliding inclusion problems, the sliding is modeled by adding the Somigliana dislocations along a matrix-inclusion interface. Exact formula are exploited for both Burgers vector and the disturbances in stress and strain due to sliding. The resulting expressions are obtained by utilizing the principle of minimum strain energy. Finally, explicit expressions are obtained for work-hardening rate of composite materials. It is verified that the work-hardening rate and yielding stress are independent on the size of inclusions but are dependent on the shape and the volume fraction of inclusions.

Effect of Hot Extrusion on the Flow Behaviour of a Nickel-Based P/M Superalloy

2019 ◽  
Vol 298 ◽  
pp. 43-51
Author(s):  
Jia Yong Si ◽  
Song Hao Liu ◽  
Long Chen
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
Hot Extrusion ◽  
Turbine Disk ◽  
Flow Behaviour ◽  
Strain Rates ◽  
Work Hardening Rate

This research investigated the effect of hot extrusion on the flow behaviour of nickel-based superalloy FGH4096 by hot compression experiments in the temperature range from 1020 to 1110 °C and strain rates ranging from 0.1 to 0.001 s-1. The influence of the hot extrusion on the initial microstructures, work hardening rate, strain rate sensitivity, and activation energy of deformation were discussed. The results show that the extruded microstructure is constituted by the fine dynamic recrystallisation of grains. The true strain-true stress curves show that the as-HIPed and as-HEXed FGH4096 superalloy present double flow stress peaks and discontinuous flow softening. The as-HEXed FGH4096 is easily dynamically softened at high temperatures and high strain rates compared with as-HIPed microstructures. As for the work hardening rate, the as-HEXed FGH4096 exhibits higher θ values than that of as-HIPed. It is beneficial to the homogenous deformation and grain refinement during subsequent turbine disk forging. Comparing to as-HIPed FGH4096, the highest strain rate sensitivity value of as-HEXed is 0.306 at 1110 °C. The isothermal superplastic forging of a P/M turbine disk may be carried out at this temperature. The deformation activation energy value of the as-HIPed FGH4096 is lower which means that dislocation sliding and climbing can be easily initiated in the as-HIPed alloy.

scholarly journals The mechanism of the initiation and propagation of detonation in solid explosives

1932 ◽  
Vol 138 (834) ◽  
pp. 92-116 ◽  
Keyword(s):  
High Explosive ◽  
A Priori ◽  
Small Samples ◽  
Weight Of Evidence ◽  
Theoretical Treatment ◽  
Mechanical Shock ◽  
Initiation And Propagation ◽  
Solid Explosives ◽  
Velocity Of Propagation ◽  
The Difference

Although half a century has elapsed since the publication of the classical treatise of Berthelot upon explosives, the detailed mechanism of the initiation and propagation of detonation in liquid and solid explosives is still obscure. Detonation is a phenomenon exhibiting a number of specific characteristics which differentiate it quite definitely from the explosive combustions of such substances as gunpowder and cordite. It is well known that the latter are governed by laws relating the rate of reaction to the surface area, the temperature and pressure of the surrounding gases, etc., and that heat is the chief medium of initiation and propagation, whereas in the case of detonation, the reaction wave-front travels directly through the explosive medium in the same sense as does a sound wave, and the velocity of propagation is a very definite characteristic of the phenomenon. This stability of the detonation velocity is well demonstrated for solid explosives by the photographs in a recent paper by E. Jones ; the speeds are usually much greater than any exhibited by explosive combustions, and range from 1500 to 10,000 metres per second. Finally, the initiation and propagation of detonation appear to be associated much more intimately with mechanical shock than with flame. The weight of evidence strongly indicates that the difference between detonation and explosive combustion is fundamental and not merely of degree, and the term “high explosive” is reserved for substances capable of the former property. The theoretical treatment of detonation as a shock wave traversing the medium and maintained by the accompanying chemical reactions has been developed by several investigators. These writers have built up a quantitative theory from thermodynamical reasoning and have been able to calculate velocities of propagation, which in some cases are correct, but in practice it has been found that the thermodynamical conditions, while necessary, are not sufficient. Thus, a great number of compositions possessing all the thermodynamical qualifications of a high explosive cannot be made to detonate; others permit detonation to be initiated successfully but without propagation, and the reaction degenerates into a mere deflagration, or even dies out completely. It is indeed very difficult to judge whether a particular composition is a true detonating explosive without the opportunity to test the sample in reasonable quantity. The violent decompositions of small samples or single crystals furnishes no a priori evidence of detonation, and innumerable examples may be quoted of such material in bulk being unable to propagate the local and violent initial activity.

Plastic deformation and fracture characteristics of Hadfield steel subjected to high-velocity impact loading

2002 ◽  
Vol 216 (10) ◽  
pp. 971-982 ◽  
Author(s):  
W-S Lee ◽  
T-H Chen
Keyword(s):  
Strain Rate ◽  
Work Hardening ◽  
Shear Bands ◽  
Rate Sensitivity ◽  
Constitutive Law ◽  
Hadfield Steel ◽  
Flow Strength ◽  
Rate Dependent ◽  
Work Hardening Rate ◽  
The Impact

Investigation of the impact behaviour of Hadfield steel has been carried out in a broad range of strain rates from 10−3 to 9 × 103s−1 by means of a servo-hydraulic machine and a compressive split Hopkinson bar. The effects of strain rate on the impact properties, substructure evolution and fracture resistance have been evaluated. The observed stress-strain response is influenced greatly by strain rate, resulting in obvious changes of work hardening rate, strain rate sensitivity and activation volume. This rate-dependent behaviour is in good agreement with model predictions using the Zerilli-Armstrong constitutive law. Dislocation tangle and deformation twin substructures are also found to develop as a function of strain rate. Increasing dislocation and twin densities enhance the work hardening rate and flow strength. Catastrophic failure at high rates results from the formation of localized shear bands. With increasing strain rate, there is an increase in brittle cleavage microfracture, resulting in ductility loss. Microcracking initiates at grain boundaries due to the presence of carbide precipitates.

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