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Al-Mg alloys are widely used as important engineering structural materials in aerospace engineering, transportation systems, and structural constructions due to their low density, high specific strength, corrosion resistance, welding capability, fatigue strength, and cost-effectiveness. However, the conventional Al-Mg alloys can no longer fully satisfy the demands of practical production due to difficulties caused by many defects. The high strength of Al-Mg alloys as non-heat treatment precipitation-strengthened alloys is achieved primarily by solid solution strengthening along with work hardening rather than precipitation strengthening. Therefore, severe plastic deformation (SPD) techniques can be often used to produce ultrafine-grained structures to fabricate ultra-high strength aluminum alloys. However, this approach often achieves the strengthening of material at the cost of reduced ductility. This paper comprehensively summarizes the various approaches of ultrafine/nanocrystalline materials for enhancing their plasticity, elaborates on the creation of a bimodal microstructure within the alloy, and discusses the formation of a nanotwin microstructure within the alloy and the incorporation of dispersed nanoparticles. The mechanisms underlying both the strengthening and toughening during large plastic deformation in aluminum alloys are summarized, and the future research direction of high-performance ultrafine crystalline and nanocrystalline Al-Mg aluminum alloys is prospected.

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This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

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Sustainable poly (lactic acid) (PLA) with excellent strength, toughness, heat resistance, transparency, and biodegradability was achieved by uniaxial pre-stretching at 70 °C. The effect of pre-stretched ratio (PSR) on the microstructure and properties of the PLA was investigated. The undrawn PLA was brittle. However, after pre-stretching, the elongation at break was increased significantly. The maximum value of 161.2 % was obtained at pre-stretching ratio (PSR) of 1.0. With the increase of PSR, the modulus and strength were improved obviously (from 1601 MPa and 60.2 MPa for undrawn PLA to 2932 MPa and 106.3 MPa for the ps-PLA at PSR =3.0). Meanwhile, the heat resistance of PLA was improved obviously with the increase of PSR. For the ps-PLA3.0, there were almost no deformation and shrink at 140 °C. Interestingly, after pre-stretching, the PLA still maintained the good transparency and biodegradability. The brittleness for undrawn PLA was attributed to the network structure of cohesional entanglements. After pre-stretching, the destruction of the network structure and formation of the orientation, mesophase and oriented nanosized crystalline phase lead to the increased the toughness, strength and heat resistance without sacrificing the transparency and biodegradability. This work provides a significant guidance for the fabrication of PLA material with excellent comprehensive performance including strength, toughness, heat resistance, transparency, and biodegradability.

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OBJECTIVE: This study was designed to examine the mediator role of resilience in the relationship between chronotype and mental toughness in adolescents. METHODS: The descriptive correlational study was completed with 342 high school students from one school in Türkiye (mean age 17.25±1.11 years). Data were collected with the Morningness-Eveningness Scale for Children, Child and Youth Resilience Measure, and Mental Toughness Scale for Adolescents. Hierarchical regression analyses with PROCESS Model 4 were used to evaluate the mediator effect. RESULTS: It was observed that the morning chronotype tendency increased resilience (p < 0.001) mental toughness (p < 0.001). Higher resilience led to increased mental toughness. When the mediation effect was examined, resilience was a full mediator in the relationship between chronotype characteristics and mental toughness (ß=0.396; p = 0.000). CONCLUSIONS: According to these results, a morning chronotype tendency in adolescents increases their resilience and, therefore, mental toughness. These results suggest that effective methods for enhancing mental toughness in adolescents should be multifaceted. Additionally, it highlights the importance of identifying and regulating chronotype tendencies among adolescents, while also emphasizing the need to increase resilience in this demographic.

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Thermoset epoxy resin-based materials are widely used, but their permanent cross-linked network limits their processability and reusability, which can lead to environmental burdens. In this work, by exploiting the weak reactivity of aniline to design appropriate reaction ratios, we achieved a linear link between the epoxy resin and the curing agent. This linear link, along with the crosslinking points provided by the flexibly branched polyurethanes, avoids the inherent brittleness associated with the highly crosslinked network of conventional epoxy resins. As a result, the adhesive exhibits extraordinary improvements in extensibility and toughness. The lap shear strength, tensile strength and elongation at break reach 11.9 MPa, 14.4 MPa and 607 %, respectively. The fracture toughness is as high as 109.6 kJ/m2, far beyond the existing epoxy adhesives. The synergistic effect of disulfide bonds and hydrogen bonds confers the adhesive with self-healing and repeatable bonding characteristics. The multi-level hydrogen bonding and appropriate phase separation structure are key to optimizing toughness, resulting in excellent comprehensive performance. The introduction of polyurethane not only improves toughness but also enhances the interfacial bonding force between the adhesive and the substrate, broadening the scope of applications. The prepared high-performance polymers provide new insights into reusable epoxy adhesives.

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PURPOSE: This study aimed to evaluate the impact of artificial aging on the fracture toughness and hardness of three-dimensional (3D)-printed and computer-aided design and computer-aided manufacturing (CAD-CAM) milled 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP). MATERIALS AND METHODS: Forty bar-shaped specimens (45 × 4 × 3 mm) were prepared using two manufacturing technologies: 3D printing (LithaCon 3Y 210, Lithoz GmbH, Vienna, Austria; n = 20) and milling (Initial Zirconia ST, GC, Japan; n = 20) of 3Y-TZP. The chevron-notch beam method was used to assess the fracture toughness according to ISO 24370. Specimens from each 3Y-TZP group were divided into two subgroups (n = 10) based on the artificial aging process (autoclaving): nonaged and aged. Nonaged specimens were stored at room temperature, while aged specimens underwent autoclave aging at 134°C under 2 bar-pressure for 5 h. Subsequently, the specimens were immersed in absolute 99% ethanol using an ultrasonic cleaner for 5 min. Each specimen was preloaded by subjecting it to a 4-point loading test, with a force of up to 200 N applied for three cycles. Further 4-point loading was conducted at a rate of 0.5 mm/min under controlled temperature and humidity conditions until fracture occurred. The maximum force (Fmax) was recorded and the chevron notch was examined at 30 × magnification under an optical microscope for measurements before the fracture toughness (KIc) was calculated. Microhardness testing was also performed to measure the Vickers hardness number (VHN). A scanning electron microscope (SEM) coupled with an energy dispersive X-ray unit (EDX) was used to examine surface topography and chemical composition. X-ray diffraction (XRD) was conducted to identify crystalline structure. Data were statistically analyzed using two-way ANOVA and Student's t-test with a significance level of 0.05. RESULTS: The nonaged 3D-printed 3Y-TZP group exhibited a significantly higher fracture toughness value (6.07 MPa m1/2) than the milled 3Y-TZP groups (p < 0.001). After autoclave aging, the 3D-printed 3Y-TZP group maintained significantly higher fracture toughness (p < 0.001) compared to the milled 3Y-TZP group. However, no significant differences in hardness values (p = 0.096) were observed between the aged and nonaged groups within each manufacturing process (3D-printed and milled) independently. CONCLUSION: The findings revealed that the new 3D-printed 3Y-TZP produced by the lithography-based ceramic manufacturing (LCM) technology exhibited superior fracture toughness after autoclave aging compared to the milled 3Y-TZP. While no significant differences in hardness were observed between the aged groups, the 3D-printed material demonstrated greater resistance to fracture, indicating enhanced mechanical stability.

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Hydrogel, as a promising material for a wide range of applications, has demonstrated considerable potential for use in flexible wearable devices and engineering technologies. However, simultaneously realizing the ultrastretchability, low hysteresis, and high toughness of hydrogels is still a great challenge. Here, we present a dual physically cross-linked polyacrylamide (PAM)/sodium hyaluronate (HA)/montmorillonite (MMT) hydrogel. The introduction of HA increases the degree of chain entanglement, and the addition of MMT acts as a stress dissipation center and cross-linking agent, resulting in a hydrogel with high toughness and low hysteretic properties. This hydrogel synthesized by a simple strategy exhibited ultrahigh stretchability (3165%), high breaking stress (228 kPa), high toughness (4.149 MJ/m3), and ultralow hysteresis (≈2% at 100% of strain). The fabricated hydrogel flexible strain sensors possessed fast response and recovery times (62.5:75 ms), a wide strain detection range (2000%), a strain detection limit of 1%, and excellent cycling stability over 500 cycles. Furthermore, the hydrogel flexible strain sensor can be used for human motion monitoring, gesture recognition, and pressure recognition assisted by deep learning algorithms, showing enormous promise for applications.

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Plasticized PLA plastic films are being increasingly used in, among others, packaging and agriculture sectors in an attempt to address the rapid growth of municipal waste. The present paper aims to review the recent progress and the state-of-the-art in the field of fully bio-renewable tough blends of PLA with green plasticizers aimed at developing flexible packaging films. The different classes of green substances, derived from completely bio-renewable resources, used as potential plasticizers for PLA resins are reviewed. The effectiveness of these additives for PLA plasticization is discussed by describing their effects on different properties of PLA. The performance of these blends is primarily determined by the solvent power, compatibility, efficiency, and permanence of plasticizer present in the PLA matrix of resulting films. The various chemical modification strategies employed to tailor the phase interactions, dispersion level and morphology, plasticization efficiency, and permanence, including functionalization, oligomerization, polymerization and self-crosslinking, grafting and copolymerization, and dynamic vulcanization are demonstrated. Sometimes a third component has also been added to the plasticized binary blends as compatibilizer to further promote dispersion and interfacial adhesion. The impact of chemical structure, size and molecular weight, chemical functionalities, polarity, concentration, topology as well as molecular architectures of the plasticizers on the plasticizer performance and the overall characteristics of resulting plasticized PLA materials is discussed. The morphological features and toughening mechanisms for PLA/plasticizer blends are also presented. The different green liquids employed show varying degree of plasticization. Some are more useful for semi-rigid applications, while some others can be used for very flexible products. There is an optimum level of plasticizer in PLA matrices above which the tensile ductility deteriorates. Esters-derivatives of bio-based plasticizers have been shown to be very promising additives for PLA modification. Some plasticizers impart additional functions such as antioxidation and antibacterial activity to the resulting PLA materials, or compatibilization in PLA-based blends. While the primary objective of plasticization is to boost the processability, flexibility, and toughness over wider practical conditions, the bio-degradability, permeability and long-term stability of microstructure (and thereby properties) of the plasticized films against light, weathering, thermal aging, and oxidation deserve further investigations.

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Cortical bone is a tough biological material composed of tube-like osteons embedded in the organic matrix surrounded by weak interfaces known as cement lines. The cement lines provide a microstructurally preferable crack path, hence triggering in-plane crack deflection around osteons due to cement line-crack interaction. Inspired by this toughening mechanism and facilitated by a hybrid (3D-printing/casting) process, the study engineers architected tubular cement-based materials with the stepwise cracking toughening mechanism, that enables a non-brittle fracture. Using experimental and theoretical approaches, the study demonstrates the competition between tube size and shape on stress intensity factor from which engineering stepwise cracking can emerge. Two competing mechanisms, both positively and negatively affected by the growing tube size, arise to significantly enhance the overall fracture toughness by up to 5.6-fold compared to the monolithic brittle counterpart without sacrificing the specific strength. This is enabled by crack-tube interaction and engineering the tube size, shape, and orientation, which promotes rising resistance-curves (R-curve). "Disorder" curves and statistical mechanics parameters are proposed for the first time to quantitatively characterize the degree of disorder for describing the representation of the architected arrangement of materials in lieu of otherwise inadequate "periodicity" classification and misperceived disorder parameters (perturbation and Voronoi tessellation methods).

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The main aim of this study was to investigate adolescents' eustress-distress and mindfulness by examining mental toughness (MT) using network and mediator analyses. The study included 414 adolescents. The results showed that MT was positively related to eustress and mindfulness, but distress was negatively related to MT. Based on the network analysis findings, we tested mindfulness' mediating role in the relationship between eustress-distress and MT. The findings showed that mindfulness played a significant mediating role. However, the mediating role of mindfulness was negative for the relationship between distress and toughness and positive for eustress. These findings advance eustress, distress, and mindfulness as mechanisms for understanding the effects of MT. Considering current knowledge of MT, eustress, distress, and mindfulness, the results are discussed.

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Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0-1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

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Phenolic resins are widely used for outdoor and structural wood-based panels; however, they are challenged by high curing temperatures, low curing rates, and high brittleness. Inspired by lobster epidermis hardening, a tough, strong, and fast-curing phenolic resin (named DCS/PG/PF) was proposed herein. In this approach, dopamine-grafted chitosan (DCS) and polyethyleneimine-functionalized graphene (PEI@G) were incorporated into neat phenol formaldehyde (PF) resin. The gel time and maximum curing temperature of DCS/PG/PF resin were considerably reduced from 445 s and 147.8 °C for the neat PF resin to 317 s and 127.8 °C, respectively. This was attributed to the oxidative crosslinking of catechol moieties in DCS and amino groups in PEI@G within the naturally alkaline environment of phenolic resins in addition to the high reactivity between catechol moieties and PF chains as well as between amino and PF chains. The prepared resin demonstrated a dry bonding strength of 2.56 MPa, wet bonding strength of 1.81 MPa, and debonding work of 0.714 J, exhibiting a considerable increase of 16.9 %, 52.1 %, and 95.1 %, respectively, compared with those of the PF resin. These improvements were attributed to the dense organic-inorganic hybrid crosslinking network formed in the DCS/PG/PF. Furthermore, the DCS/PG/PF resin exhibited enhanced thermal stability.

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Choking susceptibility refers to the propensity of an athlete to choke under pressure. Mesagno has operationalized choking susceptibility as a combination of scores on self-consciousness, anxiety and coping. Despite the potential of Mesagno's protocol, there is currently limited support for its validity. Secondly, although mental toughness (MT) has a relationship with sport performance, there is limited research on its relationship to choking under pressure, specifically. The current study investigated the relationship between choking susceptibility and mental toughness. It was hypothesized that choking susceptible athletes will have significantly lower levels of mental toughness than those who are not choking susceptible. Data from a heterogeneous sample of athletes (N = 415) was obtained through a Qualtrics research panel. Results of a Mann-Whitney U showed that self-reported mental toughness was not significantly different in athletes categorized as choking susceptible and non-choking susceptible. Correlational analyses also highlighted differences between mental toughness and the composite scores of choking susceptibility, which provide researchers with avenues for future research in this area alongside a need for each construct to be examined in relation to choking behavior in sport.

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Titanium (Ti) and its alloys are known to exhibit room-temperature fracture toughness below 130 MPa m1/2, only about one half of the best austenitic stainless steels. It is purported that this is not the best possible fracture resistance of Ti, but a result of oxygen impurities that sensitively retard the activities of plasticity carriers in this hexagonal close-packed metal. By a reduction of oxygen content from the 0.14 wt% in commercial purity Ti to 0.02 wt%, the mode-Ι fracture toughness of the low-oxygen Ti is measured to be as high as KJ Ic ≈ 255 MPa m1/2, corresponding to J-integral-based crack-initiation toughness of up to JIc ≈ 537 kJ m-2. This extraordinary toughness, reported here for the first time for pure Ti, places Ti among the toughest known materials. The intrinsic high fracture resistance is attributed to the profuse plastic deformation in a significantly enlarged plastic zone, rendered by the pronounced deformation twinning ahead of the crack tip along with ample twin-stimulated 〈c+a〉 dislocation activities, in the absence of impeding oxygen. Controlling the content of a property-controlling impurity thus holds the promise to be a readily applicable strategy to reach for unprecedented damage tolerance in some other structural alloys.

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Introduction: This meta-analysis investigates the relationships between the Dark Triad personality traits (narcissism, Machiavellianism, and psychopathy) and mental toughness. Previous research has shown mixed results regarding the influence of these traits on mental toughness. The objective of this meta-analysis is to synthesize existing literature and provide a comprehensive understanding of how Dark Triad traits correlate with mental toughness. Methods: A comprehensive literature search was conducted in 7 databases, Data were extracted by correlation and analyzed using a random-effects model. Results: The results yielding 27 effect sizes with a total of 12,378 participants, revealed a significant moderate positive association between narcissism and mental toughness (r = 0.327, p < 0.001), suggesting that individuals with higher levels of narcissism tend to exhibit greater mental toughness. However, no significant associations were found between Machiavellianism (r = 0.023, p = 0.719) or psychopathy (r = -0.022, p = 0.625) and mental toughness. Discussion: The findings contribute to a more nuanced understanding of the Dark Triad traits and their differential associations with adaptive psychological constructs, highlighting the unique role of narcissism in mental toughness. This meta-analysis provides valuable insights for future research and practical applications in fostering adaptive aspects of narcissism while mitigating its potential maladaptive consequences.

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For damage tolerance design in engineering components, the fracture toughness value, KIC, of the material is essential. However, obtaining specimens of sufficient thickness from stir friction welded plates is challenging, and often, the experimental test values do not meet the necessary criteria, preventing the experimental fracture toughness, Kq, from being recognized as plane strain fracture toughness KIC. The fracture toughness Kq of 2195 Al-Li alloy welding seams with different thicknesses was measured on the forward and backward sides. Microstructure characterization was conducted by scanning electron microscope (SEM). The results indicated minimal significant differences in grain size between the advancing and retreating sides of the weld nugget zone. In specimens of the same thickness, fracture toughness measurements along the normal direction of the joint cross-section showed a high similarity between the advancing and retreating sides of the weld nugget zone. Utilizing the quantitative relationships between fracture toughness and sample thickness derived from both the fracture K and G criteria, it is possible to predict the fracture toughness of thick plates using thin plates. This study employs these relationships to calculate the fracture toughness KIC of 2195 aluminum-lithium alloy friction stir welds. The KIC values obtained are 41.65 MPa·m1/2 from the fracture K criterion and 43.54 MPa·m1/2 from the fracture G criterion.

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High-carbon steels are normally used as tool materials. The use of such steels for construction is limited due to their increased brittleness and poor weldability. However, it appears that high-carbon steels possess certain hidden reserves for enhanced plasticity and strength if properly heat-treated. An unconventional heat treatment was applied to carbon eutectoid steel (0.8 wt.% C) in order to increase its strength and impact toughness simultaneously. Samples for tensile and impact testing were held at 800 °C for different time ranges from 3 min to 9 min with subsequent cooling in oil. It was established that for each type of sample, an optimal holding time exists that is responsible for increased strength and high impact toughness. The hardness and microhardness levels of the surface and under-surface regions of the samples reached 390 HV after optimal heat treatment. An X-ray revealed a shift of the (211)α-peak to the lower 2-theta angles after heat treatment with the optimal holding time; this indicates an increase in carbon content in alpha solid solutions of approximately 0.12 wt.%. Thus, a nanostructured mixture of low-carbon martensite and thin cementite plates is formed in the under-surface region of carbon eutectoid steel after heat treatment, with a controlled holding time at the austenitizing temperature.

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Thermomechanical processing (TMP) of ferritic-martensitic (FM) steels, such as HT9 (Fe-12Cr-1MoWV) steels, involves normalizing, quenching, and tempering to create a microstructure of fine ferritic/martensitic laths with carbide precipitates. HT9 steels are used in fast reactor core components due to their high-temperature strength and resistance to irradiation damage. However, traditional TMP methods for these steels often result in performance limitations under irradiation, including embrittlement at low temperatures (<~430 °C), insufficient strength and toughness at higher temperatures (>500 °C), and void swelling after high-dose irradiation (>200 dpa). This research aimed to enhance both fracture toughness and strength at high temperatures by creating a quenched and tempered martensitic structure with ultrafine laths and precipitates through rapid quenching and unconventional tempering. Mechanical testing revealed significant variations in strength and fracture toughness depending on the processing route, particularly the tempering conditions. Tailored TMP approaches, combining rapid quenching with limited tempering, elevated strength to levels comparable to nano-oxide strengthened ferritic alloys while preserving fracture toughness. For optimal properties in high-Cr steels for future reactor applications, this study recommends a modified tempering treatment, i.e., post-quench annealing at 500 °C or 600 °C for 1 h, possibly followed by a brief tempering at a slightly higher temperature.

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ScAlMgO4 (SCAM), which can be used as an epitaxial substrate material of GaN in power devices, faces the challenge of achieving a high-quality surface by ultra-precision polishing due to its brittle and easily cleaved characteristics, which are closely associated with its mechanical properties. The micromechanical properties of SCAM single crystals were evaluated by nanoindentation and microscratch tests using different indenters. The elastic modulus EIT and the indentation hardness HIT of SCAM obtained by nanoindentation were 226 GPa and 12.1 GPa, respectively. Leaf-shaped chips and the associated step-like planes of SCAM can be found in the severely damaged regime during scratching by Berkovich and Vickers indenters with sharp edges due to the intersection of intense radial and lateral cracks. The fracture toughness (Kc = 1.12 MPa·m1/2) of SCAM can be obtained by using a scratch-based methodology for a spherical indenter based on linear elastic fracture mechanics (LEFM) under an appropriate range of applied loads. An optimal expression for calculating the fracture toughness of easily cleaved materials, including SCAM, via the Vickers indenter-induced cracking method using a Berkovich indenter was recommended.

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The importance of psychological performance skills (mental toughness) is recognised in many mission-critical professions. Similar importance has been suggested for nursing. Survey data demonstrate that surgical staff believe that such skills exert significant influence on surgical excellence, surgical errors and on managing surgical emergencies. However, few surgical staff receive such training. It is suggested that models exist to easily meet this training need and opportunity.