mode-I Loading Research Articles

Stress Field near Crack Tips in Pressurized Thick-Walled Cylinders with Single and Multiple Cracks in Linear Elastic Fracture Mechanics: Analytical and Numerical Analysis of Stress Field and Crack Behavior

<div>Arrays of radial cracks often appear at the bore of pressurized cylinders, posing potential safety risks and leading to possible structural failures. This article presents an analytical approach to evaluate the stress field arising from single or multiple uniform radial cracks in thick-walled pressurized cylinders within the context of linear elastic fracture mechanics (LEFM) under mode-I loading. This formulation is based on the fundamental equations of elasticity and approximations of stress intensity factors (SIF) reported in the literature. Hence, the SIF were revisited and their range of validity was highlighted. The study considers two types of internal pressure loading: one applied only to the cylinder’s inner surface with no pressure on the crack faces and another applied to both the inner surface and the crack faces. The influence of the number and length of cracks relative to cylinder thickness on the stress field is analyzed. A finite element model of the pressurized vessel is constructed to verify the proposed analytical solution, showing good agreement with numerical results for a limited number of cracks.</div>

A closed form expression of stress intensity factor for an arbitrarily shaped planar crack in 3-D under tensile loading

A closed-form equation was developed in this work to quantify the stress intensity factor (SIF) along an arbitrarily shaped planar crack under mode-I loading by substituting the ellipse-related parameters in Irwin’s solution with geometry-related parameters fi of the crack. This allowed incorporation of the local crack curvature effect on SIF at each discrete point along the crack front and its relative weighted contribution to SIF of the neighboring crack point i, where either stress concentration or shielding took place, into computation of the SIF distribution along the crack front. Good agreement was obtained between the KI values derived in the current work and previous numerical simulation-based studies. The current method could capture the KI distributions for surface and embedded cracks having the same shape, with their maximum values being consistent with Murakami’s area method. This solution of KI allows for highly efficient calculation of ΔKI for quantification of the 3D growth behaviors of a fatigue crack with a complex shape, paving the way for studying the statistical nature of short fatigue crack growth.

Effects of temperature on pure mode-I and mode-Ⅱ fracture behaviors and acoustic emission characteristics of granite using a grain-based model

To investigate the effects of thermally induced microcracks on the pure mode-I and mode-Ⅱ fracture behaviors of the granite, a Grain-based model (GBM) was used to build cracked straight-through Brazilian disc (CSTBD) granite specimens. Splitting tests were conducted on the CSTBD specimens treated at various temperatures under pure mode-I and mode-Ⅱ loadings, and the moment tensor algorithm was utilized to record the acoustic emission (AE) events generated by fracture during loading. The results indicate that thermally induced microcracks predominantly consist of intergranular and intragranular tensile cracks, with quartz phase transition significantly increasing the number of intragranular tensile cracks. With the increase in heat-treatment temperature, thermally induced microcracks gradually guide the initiation direction of load-induced cracks, making the crack propagation path more tortuous. The AE characteristics reveal that the fracture behavior of the CSTBD specimen heat-treated at 600 ℃ transitions from brittle to ductile. Furthermore, thermally induced microcracks can constrain the propagation distance of load-induced cracks, increasing the small-scale AE events and the b-value, thereby reducing the AE magnitude during failure.

Experimental Study on Fracture Behavior of Adhesive-Bonded Structure with V-notch Based on Digital Gradient Sensing Method.

In this paper, a comparative study of the mode-I fracture behaviors of two types of specimens with a V-notch defect under plane stress conditions was performed using the digital gradient sensing (DGS) method. First, two types of specimens (namely one-piece specimen and bonded specimen) with the same V-notch defect were both made of polymethyl methacrylate (PMMA), and three different V-notch angles' defect were considered for each type of specimen. Then, three-point bending tests were performed on both types of specimens. The angular deflection field of light near the V-notch region was recorded using a CCD during the experiments. Finally, by utilizing the relationship between the stress gradient and angular deflection as established by the elasto-optic effect, in conjunction with the principles of linear elastic fracture mechanics theory, the stress intensity factors (SIFs) of two types of specimens under different stress conditions were calculated using the least square method. According to the experimental results, the influence of V-notch angle on fracture load and fracture toughness of two kinds of specimens was discussed. Meanwhile, the experimental results show the significant differences in the fracture behaviors of the two types of specimens under mode-I loading conditions.

Evaluating the bonding effectiveness of CFRP patches in strengthening concrete structures

This study offers a thorough analysis of the efficiency of adhesively bonded Carbon Fiber-Reinforced Polymer (CFRP) patches in reinforcing concrete structures. In the dynamic field of civil engineering and infrastructure maintenance, utilizing modern materials and innovative techniques is crucial. Given the diverse stresses on concrete structures, sustainable reinforcement strategies like CFRP patching are vital. CFRP patches, with their high tensile strength and lightweight properties, reinforce concrete, enhancing its load-bearing capacity. The study reviews extensive literature on CFRP use, emphasizing its effectiveness in various environments. However, prevailing analyses often overlook shear-induced failures at the interface of bonded CFRP patches. To address this, the study introduces a novel fracture analytical technique, consolidating material parameters for assessing CFRP patch bonding efficiency. Experimental investigations compare epoxy, polyurethane, and silyl-modified polymers under mode-I loading conditions, revealing performance variations. The study underscores the importance of adhesive selection, advocating for a balance between strength and fracture energy absorption for optimal CFRP patch performance in concrete structures. It urges future design applications to consider these findings for enhanced selection and application of CFRP patches.

Effect of heat treatment on microcracking behaviors and Mode-I fracture characteristics of granite: An experimental and numerical investigation

Combining thermal stimulation and tensile fracture induced by cold water injection can synergistically enhance hydraulic fracturing, improving geothermal reservoir connectivity. To investigate the heat effect on the Mode-I fracture characteristics of granite, notched semi-circular bend (SCB) granite specimens were prepared and heat-treated at five temperatures ranging from 25 to 600 ℃. Mineralogical analysis and three-point bending tests were performed on the SCB specimens, and a grain-based model (GBM) incorporating four types of mineral particles was developed. The model was simulated for heat treatment and Mode-I loading and then validated against experimental results. The behavior and evolution of intra- and intergranular microcracks in the SCB specimens during heating, cooling, and mechanical loading were analyzed. Moreover, the fracture surface morphology and microcracking mechanisms observed in the SCB specimens at different heat-treatment temperatures were discussed. The results reveal a nonlinear trend in the Mode-I fracture toughness of the SCB specimens, initially increasing and then decreasing with heat-treatment temperature. The number of thermally induced cracks escalates with increasing heat-treatment temperature, predominantly as intergranular tensile cracks, followed by intragranular tensile cracks. Under Mode-I loading, the SCB specimens heat-treated below 450 ℃ predominantly exhibit intergranular cracks, while intragranular tensile cracks become more prevalent at 600 ℃. Thermally induced cracks can alter the propagation direction and path of mechanically induced cracks, causing macrocracks to deviate from the initial straight propagation path. Scanning electron microscope (SEM) analysis illustrates that at 300 ℃ and above, the fracture surface morphology becomes more fragmented and longer microcracks appear.

Microcracking in On-Chip Interconnect Stacks: FEM Simulation and Concept for Fatigue Test

The semiconductor industry is continuing the scaling down of both device and on-chip interconnect features, for performance and economic reasons. This trend has implications for the design of guard ring structures, i.e. metallic non-functional structures in the back-end-of-line (BEoL) stack designed to be efficient to stop microcracks. In this work, we present a sample design for an in situ experiment to study mechanical degradation and failure mechanisms of crack stop structures in the BEoL stack, to ensure the mechanical robustness of microchips for future technology nodes. Additional finite element method (FEM) simulations provide supplementary understanding of the crack kinetics. To examine the effects of mechanical loading on crack stop elements of the BEoL stack, a novel sample geometry for an in situ fatigue experiment using x-ray microscopy was developed. The x-ray microscope (ZEISS Xradia 800 Ultra) enables high-resolution imaging of the 3D-patterned sample structures and defects such as microcracks. The tailored sample geometry allows the application of a tensile load to a BEoL specimen by a lever mechanism. The feasibility of the sample design is shown by mode-I loading of a pure interconnect sample. Post-mortem analysis by scanning electron microscopy (SEM), confirming planar microcrack propagation from the notch through the dielectric layer with small deflections of the crack path near cone shaped copper vias. FEM simulations focusing on the stress-strain fields around a crack tip indicate the beginning of copper plasticity as major mechanism starting the redirection of cracks due to resulting material compression in front of the obstacle.

Effect of constraint on fracture performance of Ti6Al4V alloy fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is increasingly being used as an alternative to traditional manufacturing in the aerospace and biomedical industries. The effect of constraint on fracture performance is a crucial issue in assessing the integrity of engineering applications. This paper aims to better understand the fracture performance of Ti6Al4V components with different constraint levels produced by LPBF. Fracture toughness tests were performed on compact tensile (CT) specimens with varying crack length and specimen thickness. The results show that the fracture toughness decreases with increasing crack length, while the fracture toughness shows a large fluctuation with specimen thickness because of LPBF manufacturing defects. Both in-plane and out-of-plane constraint effects of a crack subjected to mode-I loading are analyzed by three-parameter K-T11-T33 method. A correlation line between fracture toughness and normalized T11 stress is established, which can be used to transform fracture properties of specimens with different constraint levels.

Failure analysis of curved interface in pultruded fiber-reinforced polymer laminations using phase-field approach

Pultruded fiber-reinforced polymer (FRP) composites frequently encounter fabric misalignment perpendicular to the pultrusion direction, resulting in the formation of a curved interface. For predicting delamination in pultruded fabric with curved interfaces, the phase field model is employed in the commercial software ABAQUS® through the UMAT and HETVAL subroutines. In this study, the Mode-I, Mode-II, and mixed-Mode delamination behavior are successfully simulated to validate the efficiency of the proposed phase field method. A parametric study is conducted to investigate the impact of mesh size and phase field length on the simulation results. The recommended mesh size and interface length of the phase-field model are given. Finally, the validated phase-field model is used to predict the delamination behavior exposed to Mode-I, Mode-II, and mixed-Mode loading for the curved interface. The results indicate that specimens with a curved interface exhibit greater bearing capacity compared to those with a planar interface.

Meso-scale size effects of material heterogeneities on crack propagation in brittle solids: Perspectives from phase-field simulations

Brittle solids are often toughened by adding a second-phase material. This practice often results in composites with material heterogeneities on the meso scale: large compared to the scale of the fracture process zone but small compared to that of the application. The specific configuration (both geometrical and mechanical) of this mesoscale heterogeneity is generally recognized as important in controlling crack propagation behavior and, subsequently, the (effective) toughness of the composite. Here, we systematically investigate how dynamic brittle fracture navigates through a linear array of mesoscale inclusions. Using a variational phase-field (PF) approach, we compute the apparent crack speed and fracture energy dissipation rate to compare crack propagation (and the resulting toughening) under Mode-I loading for various configurations of inclusions. We identify an interplay between the size of inclusion and that of the K-dominant zone in the presence of elastic heterogeneity: matching these two sizes gives rise to the best toughening outcome for a given area fraction of inclusions. We discuss mechanisms that rationalize this observation and the importance of the length scale parameter used in PF models in interpreting simulation results. Our work sheds physical insight into the interaction between size effects and material properties, thereby opening a venue for the rational design of functional (architected) composites for dynamic fracture applications.

Investigating the ductile to brittle transition phenomenon in binary Fe-Ni systems using molecular dynamics simulation

Ductile to brittle transition (DBT) phenomenon is commonly observed in BCC Fe-based systems, which significantly deteriorates their low temperature fracture toughness. Ni is known to be an effective alloying element to improve the low temperature toughness by reducing the ductile to brittle transition temperature (DBTT). The present article investigates the role of Ni in tailoring the DBT curve of BCC Fe by employing molecular dynamics (MD) simulation. Here, we performed mode-I loading of different pre-cracked systems (pure Fe, Fe-2 wt% Ni and Fe-4 wt% Ni alloys) over a temperature range of 1–800 K to construct their DBT curves. The DBT curves are subsequently correlated with the temperature sensitivity of fracture stress, which is estimated using the concept of critical strain energy release rate (GIC). The role of Ni in reducing the fracture stress sensitivity is responsible for decreasing the DBTT as well as the slope of the DBT region. The underlying mechanism is discussed in terms of the crack blunting effect of Ni which effectively increases the GIC and hence the fracture stress, particularly at the low temperature regimes. Besides, the significantly large strain rate imposed in MD simulation is mainly responsible for the higher DBTT values when compared with the experimental results. The present paper tackles this strain rate issue by using an appropriate strain rate sensitivity factor to rescale the simulated DBTT values down to the experimental ones, resulting in a good match between the simulated and experimental DBTT.

Assessing critical fracture energy in mode I for bonded composite joints: A numerical–experimental approach with uncertainty analysis

The manufacturing process of composite structural components involves the assembly of composite parts using adhesives, which introduces variations in the geometrical and mechanical properties of bonded joints. The fracture energy under mode-I loading ( G I c) is a parameter used to predict crack propagation and evaluate the residual strength of the joint. This work proposes a numerical-experimental procedure to determine G I c in mode I, while considering the uncertainties inherent in the manufacturing process of bonded joints. The proposed procedure employs a three-dimensional finite element model to simulate a double cantilever beam test, using finite element commercial software. The cohesive zone model is applied to simulate the mechanical behavior of the adhesive, and experimental data are used to feed the computational model. A Plackett-Burman design is performed to reduce the number of experiments and evaluate the effect of the main influence parameters. Force-displacement curves are obtained, the compliance-based beam method is applied to determine G I c in mode I, employing both trapezoidal and triangular traction-separation laws. The results are thoroughly examined, taking into account the potential strengths and limitations of the proposed procedure, particularly in its application to predicting the behavior of bonded composite joints under mode I loading conditions. The proposed approach can help to understand the uncertainties effect related to the manufacturing process of bonded joints on G I c values, and improve the reliability of predicting crack propagation and residual strength assessment in bonded joints.

Experimental study on the mixed mode debonding by using a modified CFRP-to-steel double strap joint

The bond response of CFRP-to-steel joints in mixed mode-I/ΙΙ is a big concern since the loads consistent with mode-I may decrease the shear load capacity of the joints. For this motive, the current work introduces a modified CFRP-to-steel double strap bonded joint in which different initial peeling angles can be created. The specimens were monotonically loaded with a tensile machine until failure that subjected the CFRP-to-steel joint to a pull-pull condition. Although the specimens were geometrically symmetric throughout their length, the results showed that the initial debonding only occurred on one side of the two bonded CFRP strips. The side that initially debonded showed an interfacial failure between the CFRP strip and the adhesive, while the other side showed a CFRP delamination. The increase of the peeling angle significantly affected the initial shear load capacity, which decreased from the baseline 0° by 50% and 70% when 2° and 3° were adopted, respectively. Moreover, a peeling angle of 4º was found to be the critical peeling angle for the adopted CFRP-to-steel joints, i.e. the angle beyond which the specimens debond when subjected to pure mode-I loading even before any loads consistent with pure mode-II were applied to the bonded joints. The initial debonding induced a quick increase in the global slip and lower stiffness in the load-slip relationship. For the bonded region near the CFRP-loaded end, the maximum bond shear stress decreased from 20 to 7.5 MPa when the initial peeling angle varied from 0º-3º. To represent these effects on the local bond behavior, a new nonlinear bond-slip relationship is proposed and adjusted with the Integrate Absolute Errors (IAE) to the experimental results, which was achieved with IAE values lower than 4%. The results show, therefore, a high precision and versatility of the model to locally represent the bond behavior of the present CFRP-to-steel joints with different initial peeling angles.

The thickness effect of rubbery nanofibrous mat on modes I–II fracture mechanism of composite laminates

This study investigates the effect of the interleaving nanofibers, made of NBR/PCL blend, on the interlaminar fracture toughness of carbon/epoxy laminates. Different nanomat thicknesses, ranging from 20 μm to 120 μm, were tested at Mode-I and mode-II and results were compared to the non-modified laminates. Acoustic Emission (AE) technique was used to assess the influence of interleaving nanofibers on dominant damage modes of the specimens, i.e., matrix cracking, fiber/matrix debonding, and fiber breakage. Moreover, the damage mechanism and the nanofiber toughening contribution were investigated by means of crack path and surface analysis. Results indicated that the optimum nanomat thickness for mode-I is 40 μm (GI,R = + 333 %), while for mode-II is 20 μm (GII,R = + 43 %). The study also confirmed by AE the significant impact of nanofibers on various damage modes, especially during mode-I loading.

A comparative study of the effect of various surface treatments on the fracture behavior of aluminum adhesive joints under mode I loading

This study investigates the effect of different surface treatments on the fracture behavior of epoxy-aluminum joints under mode-I loading. Six surface treatments including degreasing, abrasion with varying grit sizes, alkaline etching, acid etching, a combination of alkaline and acid etching, and a combination of abrasion and acid etching were applied to aluminum surfaces before bonding. Surface morphology, roughness parameters, total surface free energy, contact angle, and elemental composition were analyzed. Results showed that the ultimate fracture load and fracture energy initially increased and then decreased with increasing surface roughness. The most effective treatments were found to be acidic etching in combination with alkaline etching and abrasion due to their synergetic effects. These treatments removed the natural oxide layer and created a porous oxide layer, enhancing surface roughness, increasing adhesive-substrate contact areas, and providing more sites for mechanical interlocking. Compared to the degreased specimens, significant improvements were observed, including a 40% and 31% increase in maximum fracture load, a 74% and 53% increase in initiation fracture energy, and a 65% and 47% increase in propagation fracture energy, respectively. Etching treatments demonstrated superior effects on the fracture behavior of aluminum adhesive joints compared to abrasion methods, leading to cohesive failure after etching treatments.

Effect of Shape and Distribution of Secondary Voids on Ductile Crack Path

Ductile fracture in structural metals and alloys comprises of three distinct stages: namely nucleation, growth, and coalescence of voids. In this failure mode voids, either pre-existing in the material or nucleated during deformation grow until they coalesce to form a continuous fracture path. The larger voids nucleating early in the deformation history are often referred to as the primary voids whereas the smaller ones (typically around 0.1 to 0.01 times the size of the primary voids) nucleate much later and are described as the secondary voids. As the imposed deformation increases, voids grow, and the ductile crack path is influenced by the interaction and coalescence of the two-scale voids. The present work numerically models the interaction between the two populations of pre-existing voids lying ahead of the crack tip. The influence of secondary voids attributes, in particular, the shape and distribution of secondary voids on ductile crack propagation is analysed. A plane-strain modified boundary layer (MBL) model, under small-scale yielding condition, subjected to remote mode-I loading is analysed. Both primary and secondary voids lying near the crack tip are modelled explicitly. In the absence of secondary voids, as expected, the crack path is controlled by the distribution of primary voids. The presence of small secondary voids, however, influences the crack growth and, hence, the crack driving force. Various initial configurations of secondary voids are modelled and some details of crack propagation and the numerically computed driving force versus crack extension (J-Δa) curves are presented.

A new pore-strength model for the quantitative strength prediction of ceramics under mode-I loading

Strength prediction under the action of pores is crucial for the safety of ceramics. Here, a quantitative prediction model of pore-strength response under mode-I loading was developed based on the new mapping relationship between stress intensity factor and tip radius. The new model was proved to have great application after comparison and analysis of the pore-strength test data of three typical ceramics as well as the pertinent data as-reported in the literature. Results indicated that when the tip radius of pore (ρ) exceeds the critical value (ρc = KIc2/(πσ02)), the stress intensity factor increases as a power function with increasing ρ, at which point the strength decay is significantly weakened, and when the ρ is lower than the ρc, the pore can be equated to a crack problem. This work can not only forecast and assess the failure strength of ceramics containing pores, but also provide guidance for the design of extremely dependable ceramics.

Effect of freezing and thawing process on fracturing mechanism and acoustic emission characteristics of notched semi-circular bend specimens of red sandstone

Understanding the effect of freeze-thaw (F-T) cycles on the fracture mechanism of rocks under mode-I loading is exceptionally prominent in addressing the underlying factors of rock engineering under a frosty environment. A three-point bending test was carried out on sandstone specimens exposed to 0, 10, 20,40, 60 and 80F-T cycles to achieve the fracture parameters. Moreover, the digital image correlation (DIC) and acoustic emission (AE) methods were employed to reveal the progressive failure in different loading stages. The results divulged that the F-T cycles significantly influenced the fracture parameters, including fracture toughness (KIC) and fracture energy (Gf). The average KIC values have given a negative linear relation with increasing F-T cycles. The percentage of KIC drop with F-T cycles is 9.78 %, 12.20%, 18.56%, 27.2%, and 31.60% for samples treated with 10, 20, 40, 60, and 80 cycles, respectively, while the fracture energy (Gf) gives a decline-rise trend from 0 to 10 and 20 to 80 cycles. The AE signals have demonstrated an apparent stage characteristics, and a sudden rise has occurred in the AE count rate at peak loading, revealing the fracture zone of rock under loading. The DIC effectively revealed the progressive failure pattern, especially at the later loading stages. When the load progressed to around 80–90% of maximum loading, a diverse high-strain region appeared at the tipping point, and the high-strain area continued to develop. The results of this study can effectively address the complex fracturing phenomenon of rocks and provide valuable insights into construction and engineering operations in cold climates.

Characterisation of fatigue delamination growth in plain woven hybrid laminated composites subjected to Mode-I loading

Effect of similar and dissimilar crack plane interface configuration on fatigue delamination growth in plain woven hybrid composite laminates under Mode-I has been investigated. Constant displacement amplitude fatigue testing with displacement ratio of 0.1 was carried out on 3 configurations of plain woven glass/carbon epoxy composite laminates. A power law like fit between recorded delamination length and corresponding cycle was used to predict crack length for each of the cycle. Delamination growth rate,da/dN is computed by differentiating the expression of power-law like fit.The obtained crack growth rate for each of the specimens were plotted with respect to two normalised functions, G^Imax=GImax(a)/GIR(a) where GImax is maximum mode-I energy release rate and GIR(a) is the interlaminar fracture toughness resistance and ΔG^Ieff=G^Imax-G^Imin2 as crack driving parameters computed on the basis of Modified Beam Theory (MBT) and Valvo’s mode partition method (MPV) are used in Paris relation to quantify delamination propagation. It is observed that the exponent values predicted by MBT method for G^Imax is lower as compared to ΔG^Ieff. Whereas, exponent values predicted for G^Imax is higher as compared to ΔG^Ieff predicted by MPV method. The higher the exponent value, the higher is the sensitivity of the model leading to uncertainties in the crack growth prediction. Also, it is to be noted that cyclic loading effect is when both GImax and GImin is considered, the use of ΔG^Ieff as crack driving parameter to quantify delamination propagation is justified. Secondly, MBT method does not account for the mode-mixity arising due to hybrid material configuration as in the case of Local Symmetry Fatigue (LSF) and Asymmetry Fatigue (ASF) specimens. Hence, results in higher exponent as compared to MPV method. On the other side, the G^Imax and ΔG^Ieff computed on the basis of MPV method is the pure Mode-I component deduced from the total energy release rate of mode-mixity.The equations of curve fitting is very much the same for Simple Symmetry Fatigue (SSF) specimens indicating that MBT and MPV methods predict pure Mode-I behaviour for symmetric configuration for delamination growth under fatigue Mode-I loading. From the composite laminate configuration point of view, LSF specimens have higher exponents as compared to ASF and SSF specimens indicating, local symmetry configuration laminates are highly sensitive to the small uncertainties and results in unstable crack growth.Comparison of results of all hybrid composite laminates shows that the normalised functions of G^Imax and ΔG^Ieff as crack driving parameters computed on the basis of MPV method is able to capture the effect of interlayers and stacking effect on the delamination growth in hybrid plain woven composites in fatigue loading and MPV method is found to be not sensitive to G^Imax and ΔG^Ieff for displacement ratio of 0.1.

Atomistic fracture in bcc iron revealed by active learning of Gaussian approximation potential

The prediction of atomistic fracture mechanisms in body-centred cubic (bcc) iron is essential for understanding its semi-brittle nature. Existing atomistic simulations of the crack-tip under mode-I loading based on empirical interatomic potentials yield contradicting predictions and artificial mechanisms. To enable fracture prediction with quantum accuracy, we develop a Gaussian approximation potential (GAP) using an active learning strategy by extending a density functional theory (DFT) database of ferromagnetic bcc iron. We apply the active learning algorithm and obtain a Fe GAP model with a converged model uncertainty over a broad range of stress intensity factors (SIFs) and for four crack systems. The learning efficiency of the approach is analysed, and the predicted critical SIFs are compared with Griffith and Rice theories. The simulations reveal that cleavage along the original crack plane is the atomistic fracture mechanism for {100} and {110} crack planes at T = 0 K, thus settling a long-standing issue. Our work also highlights the need for a multiscale approach to predicting fracture and intrinsic ductility, whereby finite temperature, finite loading rate effects and pre-existing defects (e.g., nanovoids, dislocations) should be taken explicitly into account.