Material Failure Research Articles

Surrogate PHFGMC micromechanical models for multiscale analysis: AI-enhanced low-velocity impact analysis of hat-stiffened composite panels

The Parametric High-Fidelity Generalized Method of Cells (PHFGMC) has been established as an advanced micromechanical approach well-suited for analyzing the material nonlinearity and failure behavior of diverse periodic composite materials. In order to overcome the prohibitive computational cost of integrating micromechanical models into multiscale structural analyses as constitutive models, a proxy-surrogate modeling approach has been proposed by implementing a reduction modeling approach with deep Artificial Neural Networks (DNNs or ANNs). The PHFGMC-ANN approach has been employed to investigate the low velocity impact (LVI) analyses of hat-stiffened laminated composite panels under impact loading at various locations and energies with two different support conditions. Subsequent analysis of stiffened panels under compression loading has been conducted to understand the failure behavior of impacted panels. Further investigation was conducted into the separation between the skin and the stiffener, focusing on a single hat-stiffened coupon subjected to LVI. The analysis results have been compared against the experimental tests, and the comparison of interlaminar delamination has been used to demonstrate the efficacy of the new framework in integrating refined nonlinear micromechanical models within a multiscale analysis.

The Anti/Deicing Performance of the Low Interfacial Toughness Coating Is Enhanced: Induced Ice Crack Generation and Its Extension.

The low interfacial toughness of the material surface is important for crack initiation and expansion of the ice layer as it remains an effective method for large-scale deicing. However, there are challenges, such as a large critical icing size and incomplete shedding of the ice layer. Adjusting the interfacial forces to make the ice more prone to cracking, expanding, and shedding is advantageous in addressing the problem of anti-icing failure in materials with low interfacial toughness. Therefore, we propose a deicing strategy that combines porous PDMS (polydimethylsiloxane) coatings with low interfacial toughness and piezoelectric vibration. A series of hydrophobic porous PDMS coatings with different porosities were prepared on the surface of an aluminum alloy substrate through curing and phase separation. The elastic modulus of the coatings decreased from 1465 to 509 kPa as the coating porosity increased, revealing the mechanism behind the improvement in mechanical properties. The key to promoting ice fracture on porous PDMS coatings lies in the synergistic effect of the out-of-plane shear stress and microcracks at the solid-ice interface. This work focuses on exploring the characteristics of interfacial forces by combining the intrinsic mechanical properties of coatings with external forces, providing new insights for designing low interfacial toughness anti-icing materials.

Retraction: “Breaking Stress Criterion That Changes Everything We Know about Materials Failure”

Retraction: “Breaking Stress Criterion That Changes Everything We Know about Materials Failure”

Bifunctional electrolyte additive enabling long cycle life of vanadium-based cathode aqueous zinc ion batteries

Aqueous zinc ion batteries have received extensive attention due to their many advantages, but they still face problems such as dendrite growth and interface reaction of Zn anode and collapse of vanadium-based cathode structure. Here, a bifunctional electrolyte additive Methionine (MET) is proposed, which exhibits a unique role in inducing uniform deposition of zinc anode and inhibiting the failure of vanadium-based cathode materials. MET affects the solvated structure of the electrolyte to inhibit water activity and reduce HER and other related parasitic reactions. At the same time, it regulates the flux of Zn2+, improves the deposition kinetics of Zn2+ on the zinc anode side, and induces the preferential growth of the Zn (1 0 1) crystal plane to promote ordered Zn deposition. In particular, MET can in-situ generate a CEI containing such as ZnF2 on the surface of the vanadium-based cathode to inhibit the failure of the vanadium-based cathode, while adjusting the surface electronic state and Zn2+ diffusion behavior, and reducing the structural damage of the vanadium-based cathode caused by the Zn2+ intercalation process by inducing a strengthened surface pseudocapacitive reaction. Compared with the bare electrolyte, the capacity retention rate of the K2V8O21||Zn full-cell with OTF-M50 electrolyte increased from 10.2 % to 99.8 % after 800 cycles at a low current density of 1 A/g. Therefore, MET exhibits considerable application prospects as a bifunctional additive that can improve the stability of vanadium-based cathode and promote the stable deposition of zinc anode.

Thermal optimization of robotic piezoelectric osteotomy motion in porcine trabecular bone

BackgroundPiezoelectric osteotomy represents a potentially viable alternative to conventional techniques for preparing pilot holes for bone screws. However, piezoelectric osteotomes have demonstrated the potential to heat bone beyond 47 °C, which induces necrosis that could contribute to screw loosening, resulting in osteosynthetic material failure and pseudarthrosis. Thus, we sought to determine the working movements of a piezoelectric drill that resulted in the lowest maximum bone temperatures while ensuring that this optimal drilling motion resulted in temperatures below 47 °C. MethodsVertebrae samples were obtained fresh from a local abattoir. A robot was used to drill 15 mm holes through the vertebrae bodies parallel to a sectioned viewing surface, observed with a thermal camera. We tested three significant aspects of the osteotome's movement: the feed rate, retraction speed and working cycle to see which combination resulted in the lowest maximum temperatures. Each factor combination was tested three times for a total of 24 trials. FindingsA feed rate of 2 mm/s, a retraction speed of 2 mm/s and a novel working cycle termed “multi-pass” were found to generate the lowest maximum temperatures (41.5 °C, σ = 1.91 °C). The factors of retraction speed and working cycle demonstrated statistical significance through analysis of variance, with ordinary least squares regression indicating their optimal settings resulted in reductions in maximum temperatures of 4.95 °C and 5.63 °C, respectively. InterpretationRobotic piezoelectric osteotomy appears to represent a safe method of pedicle screw pilot hole preparation from a thermal perspective when using the optimal methods found in this study.

Strain learning in protein-based mechanical metamaterials

Mechanical deformation of polymer networks causes molecular-level motion and bond scission that ultimately lead to material failure. Mitigating this strain-induced loss in mechanical integrity is a significant challenge, especially in the development of active and shape-memory materials. We report the additive manufacturing of mechanical metamaterials made with a protein-based polymer that undergo a unique stiffening and strengthening behavior after shape recovery cycles. We utilize a bovine serum albumin-based polymer and show that cyclic tension and recovery experiments on the neat resin lead to a ~60% increase in the strength and stiffness of the material. This is attributed to the release of stored length in the protein mechanophores during plastic deformation that is preserved after the recovery cycle, thereby leading to a "strain learning" behavior. We perform compression experiments on three-dimensionally printed lattice metamaterials made from this protein-based polymer and find that, in certain lattices, the strain learning effect is not only preserved but amplified, causing up to a 2.5× increase in the stiffness of the recovered metamaterial. These protein-polymer strain learning metamaterials offer a unique platform for materials that can autonomously remodel after being deformed, mimicking the remodeling processes that occur in natural materials.

Charge-Compensation-Driven Failure Mechanism of Ni Redox in Fe-Rich Ni/Fe/Mn-Based O3-Type Layered Oxide Sodium-Ion Cathodes.

For cathode materials of sodium-ion batteries, O3-type Ni/Fe/Mn-based (Na-NFM) layered oxides have garnered extensive attention because of high economic viability, environmental friendliness, and the potential for high energy density. Among them, Fe-rich compositions exhibit higher initial charge capacity and lower bill-of-material costs, while they fade rapidly and exhibit low initial coulombic efficiency, hindering their commercialization prospects. In this work, we investigate the failure of Fe-rich Na-NFM materials through X-ray absorption spectroscopy methods. The results reveal a combined failure mechanism that encompasses not only the conventional theory of Fe migration but also an abnormal Ni-redox deterioration, which has not yet been reported. More factors related to the failure of Fe-rich Na-NFM layered oxides are discussed in detail. These findings are expected to inspire targeted research efforts toward Fe-rich Na-NFM materials, thereby accelerating the practical application of sodium-ion batteries.

Fiber-Reinforced Flexible Self-Healing Strain Sensor with Failure-Improving Sensitivity Recovery.

In this work, we address the inherent limitations of porous, flexible, fibrous, and self-healing strain sensors. Specifically, we tackle issues such as the fatigue failure of carbon-fibrous materials and the long-term flow and low mechanical stability of self-healing materials. We achieve this by combining self-healing carbon/PBS blends with fibrous materials, creating a fiber-reinforced self-healing composite. The self-healing carbon/PBS blends provide strain sensitivity and the ability to recover after fatigue and impact failure, while the fibers prevent the long-term flow of material and the scattering of pieces during impact and fatigue failure within the elastic deformation regime, enabling shape recovery. We fabricated composite wearable strain sensors with a viscoelastic functional layer composed of two continuous phases: (i) a self-healing polymer-carbon blend and (ii) long electrospun fibers of commercial polyurethane. This setup also eliminates the other drawbacks of bulk materials, such as nonlinearity of volt-ampere characteristics, irreversibility of deformation, and a low working factor, and allows improvement of the working factor after failure and healing. Most importantly, we discovered that hindered self-healing, like in the case of the MWCNT/PBS system, enables improvement of sensor sensitivity after large strains and failure, which is due to partial failure of the network formed by conductive particles.

Stepwise warm rolling for synergistic strength and ductility enhancement in heterolamellar medium-Mn steel

Medium manganese steel represents a promising third-generation advanced high-strength steel. However, achieving excellent plasticity in high-yield-strength medium manganese steel remains challenging, particularly with lower alloying element contents. In this study, we employed an innovative stepwise warm rolling process on 5Mn medium manganese steel, developing a heterolamellar microstructure along the rolling direction. The resulting steel exhibited a yield strength exceeding 1.5 GPa while maintaining a uniform elongation of approximately 29%. The high yield strength is attributed to fine lamellar grains with high dislocation density, while the excellent uniform elongation is due to the synergistic effect of multiple plastic deformation mechanisms, which promoted prolonged strain hardening and delayed the onset of necking. These mechanisms include hetero-deformation induced (HDI) hardening generated during the early deformation of the heterolamellar structure, transformation induced plasticity (TRIP) effect-induced work hardening, and delamination cracking that alleviates interface strain concentration and delays material failure. Collectively, these mechanisms enabled the material to achieve an exceptionally high product of yield strength and uniform elongation of 45 GPa·%. This work provides new insights into the design of high-strength, ductile medium manganese steels, advancing the application of high-performance medium manganese steels.

Investigations of strength and quality of clinched joints using digital image correlation

ABSTRACT This study examines the impact of processing conditions on joint strength and the effectiveness of digital image correlation (DIC) in detecting failure points in clinched joints. Mechanical tests, including single-lap shear and pull-out tests, were conducted using DIC to evaluate joint quality in various clinched configurations. The results showed frequent failures at the neck rejoin in clinched joints between mild steel and aluminum sheets, particularly when thinner sheets were positioned on the punch side and softer materials on the die side. DIC effectively identified defects and failure locations, offering insights into material combinations, sheet positioning, and failure modes. Although DIC was useful in detecting defects in both elastic and destructive regions, its ability to distinguish specific defect types from strain contour maps was limited. The study highlights the need for further research to extend DIC’s application to other mechanical joining systems and advocates for its proactive use in refining designs and manufacturing processes.

An alternative finite element formulation to predict ductile fracture in highly deformable materials

Abstract An alternative finite element formulation to predict ductile damage and fracture in highly deformable materials is presented. For this purpose, a finite-strain elastoplastic model based on the Gurson-Tvergaard-Needleman (GTN) formulation is employed, in which the level of damage is described by the void volume fraction (or porosity). The model accounts for large strains, associative plasticity and isotropic hardening, as well as void nucleation, coalescence and material failure. To avoid severe damage localization, a nonlocal enrichment is adopted, resulting in a mixed finite element whose degrees of freedom are the current positions and nonlocal porosity at the nodes. In this work, 2D triangular elements of linear-order and plane-stress conditions are used. Two systems of equations have to be solved: the global variables system, involving the degrees of freedom; and the internal variables system, including the damage and plastic variables. To this end, a new numerical strategy has been developed, in which the change in material stiffness due to the evolution of internal variables is embedded in the consistent tangent operator regarding the global system. The performance of the proposed formulation is assessed by three numerical examples involving large elastoplastic strains and ductile fracture. Results confirm that the present formulation is capable of reproducing fracture initiation and evolution, as well as necking instability. Convergence analysis is also performed in order to evaluate the effect of mesh refinement on the mechanical response. In addition, it is demonstrated that the nonlocal parameter alleviates damage localization, providing smoother porosity fields.

Fatigue life modeling for a low alloy steel after long-term thermal aging

Fatigue failure of materials has a considerable impact on the safety of equipment in service. In this study, axially tensile and low cycle fatigue tests were conducted on a low alloy steel after accelerated thermal aged at 450 °C for 10,000 h. The experimental results indicate that the ultimate and yield strengths increase moderately, while the fatigue life of specimens experience a slight decrease in this circumstance. The fracture analysis demonstrates that the bainite breaking facilitates the fatigue crack initiation and propagation after thermal aging, which is accompanied by a decrease in plastic strain amplitude. Therefore, the plastic strain amplitude is considered as an indicator of thermal aging in fatigue life modeling for the low alloy steel. Finally, a novel life model that incorporates both aging time and temperature was proposed for rapid prediction of low cycle fatigue life. It is assumed that this model promotes reliable fatigue life prediction in low alloy steels under various thermal aging circumstances, as well as the extrapolation of fatigue performance of the material in service.

Natural coil springs: Biomechanics and morphology of the coiled tendrils of the climbing passion flower Passiflora discophora

Tendrils of climbing plants possess a striking spring-like structure characterized by a minimum of two helices of opposite handedness connected by a perversion. By performing tensile experiments and morphological measurements on tendrils of the climbing passion flower Passiflora discophora, we show that these tendril springs act as coil springs within the plant's attachment system and resemble technical coil springs. However, tendril springs have a low spring index and a high pitch angle compared with typical metal coil springs resulting in a more complex loading situation in the plant tendrils. Moreover, the tendrils undergo a drastic shift from the fresh turgescent stage to a dried-off and dead senescent stage. This entails changes in material properties (elastic modulus in tension), morphology (tendril and helix diameter, number of windings), anatomy (tissue composition), and failure behavior (susceptibility to delamination) and reduces the degree of elasticity and strain at failure of the tendrils. Nevertheless, senescent tendrils remain functional as springs and maintain high energy dissipation capacity and high break force. This renders the system highly energy efficient, as the plant no longer needs to metabolically sustain the died-back tendrils. Because of its energy-storing spring system, its high energy dissipation and high safety factor, the attachment system can be considered a ‘fail-safe’ system. Statement of significanceThe use of coil springs as mechanical devices is not restricted to man-made machinery; striking spring structures can also be found within the attachment systems of climbing plants. Passiflora discophora climbs by using long thin tendrils with adhesive pads at their tips. Once the pads have attached to a support, the tendrils coil and form a spring-like structure. Here, we analyze the form and mechanics of these ‘tendril springs’, compare them with conventional technical coil springs, and discuss changes in the tendril springs during plant development. We reveal the main features of the attachment system, which might inspire new artificial attachment devices within the emerging field of plant-inspired soft-robotics.

Size Selection of Crack Front Defects: Multiple Fracture-Plane Interactions and Intrinsic Length Scales.

Material failure is mediated by the propagation of cracks which, in realistic 3D materials, typically involves multiple coexisting fracture planes. Multiple fracture-plane interactions create poorly understood out-of-plane crack structures, such as step defects on tensile fracture surfaces. Steps form once a slowly moving, distorted crack front segments into disconnected overlapping fracture planes separated by a stabilizing distance h_{max}. Our experiments on numerous brittle hydrogels reveal that h_{max} varies linearly with both a nonlinear elastic length Γ(v)/μ and a dissipation length ξ. Here, Γ(v) is the measured crack velocity v-dependent fracture energy, and μ is the shear modulus. These intrinsic length scales point the way to a fundamental understanding of multiple-crack interactions in 3D that lead to the formation of stable out-of-plane fracture structures.

On the nature of nano twin-induced shear band formation in a dispersion strengthened copper alloy under micro-mechanical loading

A key challenge in metallic alloys with high ductility is understanding how microstructural inhomogeneities influence shear localization, leading to localized plastic deformation and material failure. In this study, we explore the phenomenon of shear localization in coarse-grained copper, a material traditionally regarded as having low susceptibility to such behavior. Contrary to conventional understanding, our findings reveal that microstructural inhomogeneities play a pivotal role in inducing extensive strain localization during low strain rate micro-mechanical loading. The presence of fine precipitate particles leads to strain localization at small strains and low strain rates by activating shear localization driven by void formation mechanisms. Furthermore, nanoscale precipitates act as sites for dislocation pile-up within deformed structures of shear bands, leading to the formation of nano twins within these bands. Consequently, precipitate particles serve a dual role: contributing to strain localization and potential cracking, while also enhancing the alloy’s strength and ductility through nano-twinning mechanisms. This investigation offers a novel perspective on the interplay between material microstructure and deformation behavior, challenging existing paradigms in materials science.

STUDY ON THE INFLUENCE OF 1 AND 15μm PITCH VALUES ON THE APPARENT NANOMECHANICAL PROPERTIES OF LASER POWDER BED FUSION-PRODUCED CuCrZr ALLOY

Material deformation due to nanoindentation is well known. However, the deformation of a material, indentation cavity, and piled-up region drastically increases and nanohardness significantly decreases if the nanoindentation is performed in such a way that the deformation of one nanoindentation affects the others. This situation arises in various materials when they are subjected to tribological application such as pantograph assembly in electric trains and contact between the electrical power supply plug and pins. This situation has been addressed in this study and the quantitative reduction in nanohardness has been evaluated in detail. In this work, the nanoindentation was performed on the laser powder bed fusion (LPBF) CuCrZr alloy specimen under a load condition of 4500[Formula: see text][Formula: see text]N. This test was conducted at 100 points with an array of [Formula: see text] at a 1[Formula: see text][Formula: see text]m pitch value. Two significant findings were identified in this work. First, the indentation impression was smaller and the corresponding nanohardness and contact stiffness values were higher in the first column of 10 nanoindentations and the first row of 10 nanoindentations. The remaining 80 nanoindentations displayed contrasting behavior compared to the initial 20 nanoindentations due to the prior deformation of nearer regions. Nanohardness value decreased parabolically from the low deformation to the high deformation region. This finding was validated by increasing the pitch to 15[Formula: see text][Formula: see text]m under the 4500[Formula: see text][Formula: see text]N load conditions. The piled-up region around the impression of indentation changed from a semi-circular shape at a 15[Formula: see text][Formula: see text]m pitch value to a cone shape at a 1[Formula: see text][Formula: see text]m pitch value. These findings will be beneficial for industries during the design of materials and will help reduce material failures resulting from tribological activities.

Enhancing the Mechanical Properties of Injectable Nanocomposite Hydrogels by Adding Boronic Acid/Boronate Ester Dynamic Bonds at the Nanoparticle-Polymer Interface.

Incorporating nanoparticles into injectable hydrogels is a well-known technique for improving the mechanical properties of these materials. However, significant differences in the mechanical properties of the polymer matrix and the nanoparticles can result in localized stress concentrations at the polymer-nanoparticle interface. This situation can lead to problems such as particle-matrix debonding, void formation, and material failure. This work introduces boronic acid/boronate ester dynamic covalent bonds (DCBs) as energy dissipation sites to mitigate stress concentrations at the polymer-nanoparticle interface. Once boronic acid groups were immobilized on the surface of SiO2 nanoparticles (SiO2-BA) and incorporated into an alginate matrix, the nanocomposite hydrogels exhibited enhanced viscoelastic properties. Compared to unmodified SiO2 nanoparticles, introducing SiO2 nanoparticles with boronic acid on their surface improved the structural integrity and stability of the hydrogel. In addition, nanoparticle-reinforced hydrogels showed increased stiffness and deformation resistance compared to controls. These properties were dependent on nanoparticle concentration. Injectability tests showed shear-thinning behavior for the modified hydrogels with injection force within clinically acceptable ranges and superior recovery.

Cavitation damage in rubber-like silicone adhesives

In this work, the failure of rubber-like materials by cavitation is investigated. Under local triaxial loading states, as they can occur in confined geometries of adhesive bonds, the instantaneous formation of voids can be observed. Analytical results of cavitation in a commercial silicone adhesive are provided. The results show that cavitation voids can be distinguished from manufacturing voids by the inner surface of the void. The surface of the cavitation void is rugged and shows a complex fracture pattern. Pancake experiments have been conducted for different ratios of radius and thickness. To assess the fracture process of cavitation onset one macroscopic and two asymptotic solutions of the energy release rate of cavitation voids are proposed. The solutions are compared and their limitations for the analysis of cavitation onset are discussed.

Inflammation-responsive PCL/gelatin microfiber scaffold with sustained nitric oxide generation and heparin release for blood-contacting implants

Delayed endothelialization, the excessive proliferation of smooth muscle cells (SMCs), and persistent inflammation are the main reasons for the implantation failure of blood-contacting materials. To overcome this problem, an inflammation-responsive, core-shell structured microfiber scaffold is developed using polycaprolactone (PCL), selenocystamine-modified gelatin (Gel-Se), L-ascorbyl 6-palmitate (AP), and dexamethasone as the fiber shell, with poly (l-lysine) (PLL) and heparin incorporated in the fiber core. Superhydrophilic microfiber scaffolds exhibit antifouling properties that inhibit protein adsorption and blood cell adhesion, thereby effectively mitigating the risk of acute thrombosis. The continuous release of heparin and sustained generation of nitric oxide (NO) through the catalytic decomposition of S-nitrosothiols by selenocystamine lead to a biomimetic endothelial function for the enhancement of blood compatibility. The inflammation-responsive compound AP can detoxify excess reactive oxygen species (ROS) while controlling the release of dexamethasone to reduce chronic inflammation. We demonstrate the ability of microfiber scaffolds to reduce thrombotic and inflammatory complications, inhibit SMC proliferation, and promote rapid endothelialization both in vitro and ex vivo. Hence, microfiber scaffolds are robust and promising for blood-contacting implants with enhanced antithrombogenicity and anti-inflammatory capabilities.

Study on the bending mechanical properties of composite tube and metal joint bonding structure

Abstract The study of the mechanical properties of composite adhesively bonded joints is a very important issue, which directly affects the safety and reliability of the structure. This article studies the bending performance of carbon fiber composite tubes and metal joint bonding structures, as well as obtains the structural bearing capacity, influencing factors, and structural failure modes. Through mechanical analysis and static bending load tests, it is shown that the failure model of composite tube adhesively bonded metal joints under bending load is manifested as the first layer peeling or interlayer failure of the composite material in the bonding area between the tube and the joint, leading to local crushing at the end of the tube. There is no gap between the tube and the joint, which has little effect on the bending bearing capacity. The thickness gradient treatment at the end of the joint does not help improve the bending bearing capacity. The adhesive layer is at a 90 ° angle, which makes it easy for the first layer to peel off; it should be avoided. Other angle layers have little impact on load-bearing capacity. The longer the bonding length is, the stronger the bending capacity is. The adhesive J133 or 420 has a similar load-bearing. Wrapping a carbon fiber unidirectional layer around the ends of tubes and joints is helpful in improving their bending load-bearing capacity.