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Grafting nanomaterials on the carbon fiber (CF) surface is considered an effective strategy for enhancing the interfacial properties of CF-reinforced polymer composites (CFRPs). However, the mechanical properties of the CFs are often compromised during treatment. A new method for in situ growing silver nanoparticles (AgNPs) on the CF surface is proposed in this study. The CFs are first immersed in a low-viscosity silver nitrate solution to form a thin liquid film on the surface. Subsequently, using the abundant active particles in the plasma, the silver ions are reduced to silver atoms and grown into AgNPs on the CF surface. The tensile strength of CF@Ag was 38.74% greater than that of untreated CF, potentially due to the reparative action of AgNPs on defects in CF. The CF showed an evident improvement in surface wettability because of the AgNPs. Furthermore, the interfacial properties were noticeably improved, with the interfacial shear strength of CF@Ag increasing to 91.59 MPa, which was about twice that of pristine CF. Thus, the mechanical properties of composites are significantly improved (flexural strength increased by 190.74%). This study presents a non-destructive and convenient method for growing nanoparticles onto CF to establish a robust interface in CFRPs. [ABSTRACT FROM AUTHOR]

We report results on the mechanical and structural response to shear deformation of nanodiamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) and interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) based on molecular-dynamics simulations. We find that IB-TBG nanodiamond superstructures subjected to shear deformation undergo a brittle-to-ductile transition (BDT) with increasing interlayer bond density (nanodiamond fraction). However, RD-IBG bilayer sheets upon shear deformation consistently undergo brittle failure without exhibiting a BDT. We identify, explain, and characterize in atomic-level detail the different failure mechanisms of the above bilayer structures. We also report the dependence of the mechanical properties, such as shear strength, crack initiation strain, toughness, and shear modulus, of these graphene bilayer sheets on their interlayer bond density and find that these properties differ significantly between IB-TBG nanodiamond superstructures and RD-IBG sheets. Our findings show that the mechanical properties of interlayer-bonded bilayer graphene sheets, including their ductility and the type of failure they undergo under shear deformation, can be systematically tailored by controlling interlayer bond density and distribution. These findings contribute significantly to our understanding of these 2D graphene-based materials as mechanical metamaterials. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of different bonding agents and application of glaze on the shear bond strength (SBS) between monolithic zirconia (MZ) and indirect composite (IC). Materials and Methods: Five different bonding agents (G-Premio Bond [GP]; Tokuyama Universal Bond [TU]; Signum Zirconia bond [SZ]; Clearfil Ceramic Primer Plus [CCP]; Z-Prime Plus [ZP]) were applied to a total of 200 MZ disk-shaped specimens (n = 100 glazed and 100 nonglazed). Half of the specimens then underwent thermocycling and the other half no thermocycling (n = 10 specimens each subgroup). The experimental setup was prepared as two pieces according to the ISO TR 11405 standards. Specimens embedded in acrylic resin were placed into the experimental setup and a universal testing machine at a crosshead speed of 0.5 mm/minute. Mann-Whitney U test and Kruskal-Wallis test were used for statistical analyses. Bonferroni correction was then performed, and test results with P < .05 were accepted as statistically significant. Results: The application of glaze significantly enhanced SBS when ZP or CCP was used; however, it did not have any significant effect when GP, TU, or SZ were used. Thermocycling significantly decreased the SBS in all bonding agent groups except GP specimens with glaze (P = .16). The highest SBS in all conditions was noted when GP and TU were used. Conclusions: These findings suggest that the bonding agents GP and TU may be recommended for better bonding between MZ and IC. [ABSTRACT FROM AUTHOR]

For improving the mechanical properties of MgAl 2 O 4 ceramic and maintaining its wide band transparency, the sapphire/MgAl 2 O 4 /sapphire laminated transparent composites with thin sapphire layers were fabricated by brazing with BaO–B 2 O 3 –SiO 2 (BBS) glass filler. The BBS glass filler had an appropriate CTE (coefficient of thermal expansion) value and good wettability on the surface of sapphire and MgAl 2 O 4 ceramics. Joining experiments were first carried out to optimize the preparation process parameters of laminated composites. The results indicated that high bonding temperature promoted mutual dissolution and diffusion of BBS glass and MgAl 2 O 4 ceramic, but led to the intergranular infiltration of glass filler and the formation of pores due to volatilization of B 2 O 3. When the bonding temperature was 1000 °C, the sapphire/MgAl 2 O 4 joints with the best transparency and acceptable shear strength could be obtained. On this basis, the laminated composites with 0.15 mm thick sapphire layers were fabricated by brazing using BBS glass at 1000 °C. The flexural strength of the laminated composite reached 320 ± 10 MPa, which was higher than that of MgAl 2 O 4 (195 ± 15 MPa). The in-line transmittance of laminated composite was 80.9 % at 1000 nm, which was slightly lower than that of MgAl 2 O 4 (82.2 %). [ABSTRACT FROM AUTHOR]

The implementation of hot melt adhesives reaching structural adhesion with both impact resistance and detachability is of prospective industry value but still remains challenging. In this work, 2‐amino‐4‐hydroxy‐6‐methylpyrimidine serving as both chain extender and end‐capping reagent due to its isomerism, was developed to construct a supramolecular polyurethane‐derived hot melt structural adhesive. The as‐synthesized PUM elastomers occurs obvious decrease of molecular weight at 80°C compared to room temperature, revealing the existence of self‐complementary 2‐ureido‐4[1H]‐pyrimidinone (UPy) motifs at chain ends. This unique structure allows to chemically incorporate abundant hierarchical and quadruple hydrogen bonding moieties, which results in remarkable enhancement of shear strength, ranging from 6.4 to 16.6 MPa. More importantly, it also exhibits unique impact‐strengthening and reproducible adhering ability. The Hopkinson‐press‐bar and cyclic tensile tests manifest that quadruple hydrogen bonds play a pivotal role in buffering external forces and increasing energy dissipation when exposed to high velocity impacts. The true stress and strain synchronously increase as the strain rate augments while the shear strength can even roar up to ~18 MPa at high tensile speed. With regard to mild synthetic conditions, atomic economic use of reactants, it is promising that this material has industrial potential to be utilized in applications referred to energy‐absorption and reproducible structural adhesion. [ABSTRACT FROM AUTHOR]

In the present investigation, diverse functionalized states of multi-walled carbon nanotubes (MWCNT) were employed in fabricating glass/epoxy composites, with the MWCNT consistently incorporated at a 0.5 wt.% concentration. These functionalization states included pristine, hydroxyl, amine, and carboxylic conditions, systematically compared against neat glass/epoxy composites. The findings elucidated that all three functionalizations positively influenced the enhancement of interlaminar shear strength, mode-I interlaminar fracture toughness, and mode-II interlaminar fracture toughness properties. Notably, the amine-functionalized MWCNT exhibited superior performance relative to other formulations. The composite reinforced with amine MWCNT demonstrated significant improvements in ILSS, mode-I ILFT, and mode-II ILFT by 41.82%, 37.75%, and 40.93%, respectively. These enhancements are attributed to factors such as the presence of a more functional group, the quantity of individual MWCNT, and the introduction of additional damage mechanisms, including MWCNT pullout and bridging. Highlights: Improvement in ILSS of glass/epoxy composite by functionalized MWCNT by 20.11-41.82% range. Improvement in mode-I ILFT of glass/epoxy composite by functionalized MWCNT by 5.54-30.81%. Improvement in mode-II ILFT of glass/epoxy composite by functionalized MWCNT by 8.46-40.93%. Microscopic characterization using field-emission scanning electron microscopy revealed existence of MWCNT pullout and bridging. [ABSTRACT FROM AUTHOR]

Molecular dynamic simulation along with experiments was used to study polycarbonate (PC) molecular conformation on composite interfacial properties. The interlaminar shear strength (ILSS) variations of composites with carbon fiber roughness were quite different between sized and unsized carbon fibers, which seem to conflict with the theory that rougher surface is harder to wet. By the results of molecular dynamic simulation, it was found that the conformation of PC molecules through solvent intervention could be higher, which is conducive to the formation of π–π stacking conformation between PC and carbon fibers and benefits the interface interaction, resultantly affecting the ILSS more when the carbon fiber surface area was low. When the specific surface area was high enough, the ILSS gets to a saturation value, because the fracture area changes from the interface to the matrix. It is concluded that the effects of sizing on ILSS varied with carbon fiber surface roughness, and the molecular conformation of the matrix affected by sizing or processing must be considered. Therefore, it is important to enhance the physical interactions with carbon fiber for thermoplastic resin matrixes. [ABSTRACT FROM AUTHOR]

In order to find out the underlying effect of anisotropy on the failure characteristics from the mesoscopic mechanism, using the concept of fabric tensor and assumption of mutual mapping between isotropic space and anisotropic space, a compound stress is proposed based on the combination of ordinary stress and fabric tensor. This compound stress can be used to describe the primary anisotropic properties effectively. For the difference in the effect of stress-induced anisotropy on shear strength of various geotechnical materials in the deviatoric plane, a generalized failure criterion is proposed. This failure criterion can effectively describe various criteria forms from Von-Mises criterion to SMP criterion within a relatively large range. The hydrostatic pressure effect can also be indicated by the shape of the power function on the meridional plane. A primary anisotropy generalized failure criterion can be obtained when the compound stress is used to describe the new generalized failure criterion and the corresponding transformation stress method has been proposed. This method can consider the effect of native induced anisotropy and stress induced anisotropy on the shear strength simultaneously. The comparison between predicted and tested results shows that the proposed anisotropic generalized stress failure criterion and its transformation method can be applied to the geotechnical engineering practice simply, its rationality and applicability have also been verified. [ABSTRACT FROM AUTHOR]

In offshore engineering, soft clay foundations supporting infrastructure are subjected to significant multidirectional cyclic shear stresses due to earthquake or storm loads. To explore the undrained multidirectional cyclic behavior of foundation clays under critical loading conditions, a series of tests were conducted using a variable-direction dynamic cyclic shear system. By controlling the amplitude ratio (η) of two mutually perpendicular shear stresses in the horizontal plane, both unidirectional and multidirectional cyclic shear stress paths were achieved. The shear strength, stiffness, and pore water pressure are presented and discussed by considering the effects of η and cyclic stress ratio (CSR). The results suggest that the increase of CSR and η accelerates the cyclic failure, stiffness degradation, and pore water pressure accumulation of the clay specimens. An η-independent cyclic strength curve is established by normalizing the CSR to 0.755η. Although η hardly affects the shear modulus in the x direction (Gx) during the first cycle and at failure, it affects the parameter (χ) governing the shape of the stiffness degradation curve. Additionally, a model is proposed for predicting the evolution of normalized residual pore water pressure with respect to the number of cycles, wherein the parameter d remains unaffected by CSR and η. [ABSTRACT FROM AUTHOR]

Generally, marine reclamation land needs to be improved by a large margin before the construction of civil structures in coastland due to poor geotechnical properties of the dredged slurry. The combination of vacuum preloading (VP) and dynamic consolidation (DC) has been developed for application in such projects. However, the effect of the combined VP and DC method is mainly controlled by the start-up time of DC (time of first tamping); in this study, the start-up time was determined by the degree of consolidation (DOC), and the DOC under VP was estimated by pore water pressure (PWP). According to a series of previously studied laboratory test results, the DC can be applied when DOC is greater than or equal to 60%. Thus, DOCs of 60%, 65%, 70%, and 75% were considered as the judgment index of start-up time. During the model tests, the settlement and PWP were monitored and measured. The water content and vane shear strength of the dredged slurry were also measured after the completion of tests. The start-up time of DC was determined when an optimal DOC was 70%. [ABSTRACT FROM AUTHOR]

This paper aims to study the effects of the non-stationary soil property on the horizontal bearing capacity of three-dimensional monopile in spatially variable soils. The soil undrained shear strength is assumed to obey lognormal distribution and is simulated as non-stationary random fields. The mean value of the undrained shear strength linearly increases with depth, while the standard deviation keeps constant. The random finite-element method is applied to analyze the reliability of the bearing capacity. The influence of the correlations and non-stationary property on the mean and coefficient of variation of the bearing capacity are discussed. It is found that the correlation distance has no obvious effect on the bearing capacity and the bearing capacity increases with the increase of non-stationary coefficient. The results can guide the reliability-based design of horizontally loaded piles embedded in spatially variable soil. [ABSTRACT FROM AUTHOR]

Reutilisation of waste tire chips to improve red clay is of great significance to environmental protection. The mechanical properties of tire chip and cement stabilised red clay (TCCSRC) at different proportions were investigated through compaction, compression, unconfined compression strength (UCS), and direct shear tests. The UCS and shear strength of TCCSRCs with different proportions were tested and analysed at their optimal moisture content (OMC). The results indicated that the porosity ratio, UCS, shear strength, and cohesion of TCCSRC decreased with increasing tire chip content. The addition of cement increased the sample UCS and shear strength. When the content of tire crumb is 20% and the cement content is 5%, the specimens show good performance in all basic properties, including UCS can reach 1034.3 kPa; the shear strength can reach 46.7 kPa when the axial pressure is 150 kPa. [ABSTRACT FROM AUTHOR]

Civil engineering projects are always at high risk of failure when constructed on weak or soft soils due to their lower shear strength and settlement issues. This study summarises the influence of various Nano additives such as Nano aluminium oxide, Nano magnesium oxide, Nano copper, Nano clay, Nano carbons and Nano calcium carbonateon the strength, mineralogical and morphological properties of problematic soils as reported by the researchers. The strength properties such as unconfined compressive strength, direct and triaxial shear strength, and California bearing strength were enhanced with the incorporation of Nano additives up to the optimum amount of dosage in the soil. The very low amount of dosage of Nano additives provided a dramatic change in the strength due to their higher specific surface area as compared to the traditional additives such as cement and lime. The mineralogical and morphological studies showed denser and stiffer soil matrices and depict the formation of new cementitious compounds. From the detailed review of past literature, it can be concluded that the inclusion of a small amount of Nano additives in soil is capable of some shadowing the negative effect of problematic soil for construction purposes. [ABSTRACT FROM AUTHOR]

This study utilised the principles of soil mechanics and the physiograph concept to establish pedo-geotechnical patterns of natural soils for the design of pavement structure. A total of 60 disturbed and undisturbed subgrades were sampled from 10 locations at the SB segment, 10 locations through the TZ and 10 locations at the BC end. A series of specific gravity, grain-size distribution, consistency limits, compaction characteristics (unsoaked and soaked CBR) and shear strength parameters were performed. Field observation and test results revealed that the studied area consists of extensive sand, interposed with clayey sand bodies along the SB segment. Also, particles of various sizes at the TZ and heterogeneous sandy clay in the BC segment were noted. Soils from the TZ under soaked conditions have the highest CBR (80.0–88.1%), MDD (19.0–19.1 kN/m3) and the lowest OMC (10.2–10.5%) values. They also have the highest cohesive strength (72.0–80.0 kN/m2) and angle of internal friction (14°−16°). Comparison among properties revealed that soils from the SB area especially, the TZ have much higher subgrade ratings compared to the soils from the BC terrain. The result revealed that the physiography factors affect the performance of the entire pavement structure. [ABSTRACT FROM AUTHOR]

Due to the wide particle size distribution of coral sand, There are significant differences in mechanical behaviour of coral sand with different particle size distribution. It is of great significance to propose a quantitative analysis method for mechanical properties considering the effect of gradation. In this study, 27 groups of coral sand specimens with particle size ranging from 5 mm to 0.125 mm were prepared. The consolidated undrained (CU) triaxial shear tests were carried out and the influence of gradation and relative density on the shear characteristic were discussed. The grading and relative density of coral sand are controlled by the median particle size (d50) and relative density (Dr), The results show that the peak deviator stress decreased, and the effective internal friction angle first increased and then decreased with the increase of d50. Both the peak deviator stress and effective internal friction angle of coral sand increase with the relative density. A parabolic relationship was founded between the effect internal friction and d50 as Dr was constant. The effective friction angle peaked when d50 was 2 mm. Finally, a calculation method of shear strength parameter considering the gradation and relative density of coral sand was proposed. [ABSTRACT FROM AUTHOR]

In this research, rock mass deformation modulus (Emass), classification of rock mass, cohesion (c) and internal friction angle (Φ), and intact rock properties of the Khersan 2 dam site were investigated. Factors affecting mechanical properties were investigated and compared with the results of previous studies. To assess the shear strength and the Hoek and Brown failure criteria parameters, the triaxial test was performed on samples under saturated conditions. The Q-system and rock mass rating (RMR) were calculated for five-metre sections of boreholes. Results of the Mohr–Coulomb failure criterion showed that the limestones have a mean Φ of 40 degrees and a mean cohesion of 1 MPa, marl limestones have an average of 30 degrees and cohesion of 0.50 MPa, and anhydrite and gypsum showed an average of 26 degrees and 0.10 MPa. The results showed that c and Φ increase with the increase in the shear box size. Based on the RMR and Q-system the site was classified in good class. The mean of Emass showed that the dilatometry test gives the lowest value. Linear and logarithmic relationships were established between RMR89 with compressional wave velocity (Vp) (R2 = 0.95 and RMSE = 1.63) and Q-system (R2 = 0.95 and RMSE = 2.05), respectively. [ABSTRACT FROM AUTHOR]

Earthquake reconnaissance after the recent Kahramanmaras, Turkey, earthquake sequence in February 6, 2023 has shown that the majority of the reinforced concrete (RC) structural elements do not comply with the Turkish Building Earthquake Code (TBEC 2018) requirements. Accurate estimation of the actual strength of existing non-compliant RC structural members is critical to accomplish reliable earthquake performance assessments. This study aims to propose a machine learning-based framework to establish a realistic failure forecast as well as an accurate shear strength estimation depending on the expected failure modes of such walls. To achieve this, shear wall design properties are assigned as inputs whereas failure mode and shear strength were designated as outputs for the corresponding classification and regression problems, respectively. Widely used machine learning methods, namely: Ridge Linear Regression, Logistic Regression, Multi-layer Perceptron, Support Vector Machine, Random Forest, XGBoost, LightGBM, and CatBoost are employed using a database consisting of 432 non-conforming shear walls. The data is randomly split to train and test sets (80% and 20%, respectively) to develop the predictive models and to evaluate model performances, respectively. Performance metrics (e.g. ${R^2}$ R 2 , RMSE) are evaluated over a hundred random splits to ensure robustness. The proposed CatBoost-based models achieve overall accuracies above 90% for both failure prediction and shear strength estimation. The proposed framework is believed to be a promising tool for earthquake engineers for practical and accurate failure mode forecast and shear strength estimation of non-compliant RC shear walls. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study on the size effect behaviors of shear performances of concrete shear walls reinforced by steel bars and Basalt Fiber Reinforced Polymer (BFRP) bars. All the works are conducted through a two-dimensional meso-scale numerical simulation model representing the concrete shear wall. The horizontal reinforcement ratio and the sectional size are the main parameters concerned by the present study. Both the seismic behaviors under cyclic loading and the size effect behaviors of the shear performances were simulated and investigated. It can be concluded from the simulation results, (1) the use of steel bars or BFRP bars as horizontal reinforcement does not change the shear failure modes of concrete shear walls, (2) the size effect on the nominal shear strength of BFRP reinforced concrete (BFRP-RC) shear wall is more significant compared to that for steel-RC shear wall, (3) the increase of horizontal reinforcement ratio improves the shear capacity of the concrete shear wall, while weakens the size effect on the nominal shear strength, and (4) the size effect law for the nominal shear strength of steel-RC shear wall is applicable to BFRP-RC shear wall. Finally, the importance of considering size effect in the evaluation of shear performance of steel-/BFRP-RC shear wall is manifested by comparing the predictive results of several popular design codes with the simulation results. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymers (FRP) have been widely used in shear strengthening applications of reinforced concrete (RC) beams. The accurate prediction of the FRP contribution to the shear strength of beams is essential for reliable design. Gene expression programming (GEP) has been widely utilized because it reliably expresses complex relationships between experimental variables. In this study, three new GEP models are proposed for three different strengthening configurations of FRP such as fully-wrapping, U wrapping, and side-bonding to predict the FRP contribution to shear strength. These models are developed using the most comprehensive database containing a total of 811 strengthened beams (350 fully-wrapped, 328 U-wrapped, and 133 side-bonded. Many variables have been considered in the proposed GEP models, including those that have been experimentally effective but are often neglected in existing literature equations, such as the shear span-to-effective depth ratio (a / d) and the stirrup ratio ( ρ w ). Additionally, the reliability of existing equations in the literature and the proposed GEP models for predicting the FRP contribution to shear strength was statistically evaluated. As a result of this evaluation, the proposed GEP models for each strengthening configuration of FRP yielded the most accurate statistical results, with the lowest coefficient of variation (COV), and the highest coefficient of correlation (R). [ABSTRACT FROM AUTHOR]

Lack of investigation into the tensile strength characteristics of unsaturated tailings hinders their recycling as construction materials in bulk earthworks. Here, the strength characteristics and strength-dilatancy relation in the tensile stress regime of unsaturated tailings were investigated via flattened Brazilian and direct shear tests. A nonlinear variation of tensile strength with water contents was observed. The unsaturated tailings with water contents below the plastic limit were strain softening and dilative under low normal stress. Furthermore, an analytical equation was proposed to predict the tensile strength of compacted tailings via the soil water characteristics curve (SWCC) and corroborated via experiments. [ABSTRACT FROM AUTHOR]

The fracture resistance of adhesive joints depends on the bondline thickness, especially in the toughest systems. While increasing the adhesive thickness to operate at peak fracture toughness is anticipated to be attractive, it leads to a mass increase and to a decrease of the effective shear stiffness and strength, calling for a trade-off. Here, we follow a rational materials selection approach for mechanical design to address different sets of objectives and constraints representative of different classes of applications. The approach is applied to select the best conventional adhesive based on a novel database. Mechanical analysis with two different degrees of complexity is considered. The elementary level only accounts for the influence of thickness on toughness, while more advanced models introduce the dependence of shear strength on thickness as well as the stiffness mismatch with the adherends. The best adhesive choice strongly depends on the objectives, constraints, and loading configuration. However, the ranking is not drastically affected by the adherends' stiffness. Gaps found for stiff/strong and tough adhesives motivate the development of architected joints. Inserting stop holes improves damage tolerance and density but reduces the shear strength and stiffness, requiring an optimum design. [ABSTRACT FROM AUTHOR]

The mechanical properties and structure of polybutylene terephthalate (PBT)/aluminum (Al) composite prepared by ultrasonic-assisted hot-pressing were analyzed, and the influence of ultrasonic-assisted on the bonding properties of PBT/Al composite was studied. The experimental results showed that under the optimal ultrasonic-assisted conditions, the tensile shear strength of the PBT/Al composite reached 26.55 MPa, which was 22.18% higher than that of the PBT/Al composite without ultrasonic-assisted (21.73 MPa). Scanning electron microscopy (SEM) showed that during the hot-pressing process, ultrasonic-assisted promoted the embedding of PBT in the anodic oxide pores on the surface of Al, forming a stronger mechanical interlocking structure. X-ray diffraction (XRD) showed that ultrasonic-assisted did not change the crystal type of PBT, but the shear effect of ultrasound affected the arrangement and orientation of molecular chains in the PBT melt, resulting in changes in crystallinity. X-ray photoelectron spectroscopy (XPS) showed that ultrasonic-assisted did not generate new chemical bonds during the hot-pressing process. Therefore, during the hot-pressing process, ultrasonic-assisted promoted the embedding of PBT in the anodic oxide pores on the surface of Al, enhanced the mechanical interlocking effect between PBT and Al, and improved the tensile shear strength of the PBT/Al composite. [ABSTRACT FROM AUTHOR]

A set of direct shear tests was conducted to investigate the effects of sand mean grain size and geomembrane surface roughness on the shear behaviour of the sand–geomembrane interface. Four types of sands with different mean grain sizes were used and the interfaces included a smooth geomembrane (SGM) and four textured ones with different asperity characteristics. The samples were prepared in a direct shear box at five sedimentation angles. The experimental results showed that the peak friction angle of the soil–textured geomembrane interface was dependent on the mean grain size, inherent anisotropy and surface roughness of the geomembrane. The shear strength of sand–textured geomembranes was two to three times larger than that of the sand–SGM interface. The peak and residual friction angles of sand-SGM interface occurred at sedimentation angle of 72° while it was 108° for sand-TGM interfaces. An increase in mean grain size increased the shear strength of the sand–textured geomembrane interface; while a reverse condition occurred for the sand–SGM interface. The shear strength occurred at larger horizontal displacement as mean particle size increased and the effect of relative roughness on peak friction angle increased with increase in mean grain size. [ABSTRACT FROM AUTHOR]

In the Kashmir region of Pakistan, the presence of Siwalik clays engenders serviceability issues to the infrastructure causing substantial loss of property. In this study, an attempt has been made to address these issues using polypropylene fibres (PPFs) as a sustainable modifier. These fibres were used in five different proportions, namely 0.25, 0.5, 0.75, 1 and 1.25% as partial replacement of base soil to analyse their impact on the engineering behaviour of matrices. Classification, compaction, indirect tensile, unconfined and triaxial compression, swell potential, consolidation and California bearing ratio (CBR) tests were conducted on controlled as well as reinforced-clay samples for comparative analyses. The maximum improvements were observed in unconfined compressive strength (109%), tensile strength (300%), cohesion (13%), friction angle (110%), soaked CBR (800%) and un-soaked CBR (550%). Besides, the reduction in swelling strain by 92% was also recorded corresponding to 1 kPa effective vertical stress. The capital cost analyses showed that PPFs reduced the costs of backfill behind the retaining wall and foundation soil beneath isolated footing by 21 and 44.5%, respectively. Moreover, the modifier had no adverse effect on the aqueous media. Conclusively, PPFs can be used as sustainable modifiers leading to a potential solution for serviceability issues. [ABSTRACT FROM AUTHOR]

In construction projects in Khuzestan province in Iran, electric-arc steel slag (EASS) materials are used as fill materials. In this research study, bio-cementation practice on EASS materials is examined and compared with that on natural sand. For this purpose, direct shear, unconfined compressive strength (UCS) and constant head permeability tests, together with scanning electron microscopy images obtained using an instrument equipped with an energy-dispersive X-ray spectroscope, were used to analyse and compare untreated and treated materials. The results showed that despite higher urease activity and higher calcite production of EASS materials compared with natural sand, the latter showed slightly higher UCS, higher cohesion intercept enhancement and higher permeability decrease after bio-cementation treatment. [ABSTRACT FROM AUTHOR]

Vertical drains installed in soft clay deposits enhance the rate of consolidation in preloading projects. Using a mandrel to install the prefabricated vertical drains, its insertion and withdrawal will result in the remoulding of the soil zone surrounding it, called the smear zone. The extent of the smear zone is an important parameter that characterises the smearing effect. This paper describes this effect in terms of smear ratio (i.e. the ratio of the diameter of smear zone ds to the diameter of drain, dw) on the consolidation characteristics of soil with radial drainage. A series of radial consolidation tests with a predetermined smear zone in a model unit cell was conducted by varying the diameter of the smear zone. The experimental results show that beyond a smear ratio of 4, the soil behaves as if it is in a fully remoulded condition. The results were compared with some of the theoretical approaches reported in the literature. The analytical solution that predicts the time–settlement curve in a better way is identified. Also, it is observed that the gain in undrained shear strength due to the consolidation of soft clay decreases with the increase in the diameter of the smear. [ABSTRACT FROM AUTHOR]

The machining mechanics of carbon fiber reinforced polymer (CFRP) materials are influenced by the coupled effects of the workpiece anisotropy, tool edge geometry, and cutting parameters. Predicting the chip formation mechanism is crucial for optimizing cutting parameters, reducing tool wear, and improving efficiency and surface quality. This study quantitatively evaluates the effect of main CFRP failure criteria on the chip formation mechanism in modeling the machining mechanics of CFRP. The results show that the Hashin-Puck and Dávila criteria excel at capturing chip formation across all fiber orientations because of the incorporation of the "internal friction" concept, while others only achieve accurate predictions in specific fiber orientation ranges due to improper shear strength consideration. The sources of the prediction similarities, differences, and limitations of failure criteria are experimentally validated. Sensitivity analyses quantitatively determine the effect of the tool rake angle on the machining energy consumption and cutting forces across the fiber orientation range. This research can be used to select the optimal failure criteria, design proper cutting tool geometry, and inform the cutting parameter choices for CFRP machining operations. [ABSTRACT FROM AUTHOR]

AlCoCrFeNi2.1 eutectic high‐entropy alloy was introduced to join Cf/SiC composite by spark plasma sintering technique. The influence of holding times on microstructure, shear strength and fracture behavior of the joints was studied. When held for 7 min, the typical microstructure of the Cf/SiC‐AlCoCrFeNi2.1‐Cf/SiC joint was Cf/SiC composite → CrSi2 + FCC + Al8Cr5 + graphite → CrSi2 + FCC + Al8Cr5 → CrSi2 + FCC + Al8Cr5 + graphite → Cf/SiC composite. As the holding time extended, the Ni–Si and Fe–Si brittle phases in the joint gradually reduced, and the diffusion transition layer continued to thicken. The maximum joint strength was 23.9 MPa, which was obtained at 1450°C for 7 min. Analyzed by scanning electron microscopy and energy dispersive spectroscopy, the fracture modes of the joints joined at different holding times were all brittle fracture. [ABSTRACT FROM AUTHOR]

Underground coal mining operations are vital to global energy supply that often take place in challenging environments where structural stability and safety are paramount. Shotcrete is a widely adopted technique for reinforcing underground rock surfaces which has been proven effective in safeguarding against roof collapse and structural instability. However, the underground environment remains susceptible to low velocity impacts from falling debris, blasting and equipment interactions which can pose significant risks to miners and infrastructure. This research article presents an experimental investigation into the effectiveness of tuned mass dampers (TMDs) in enhancing the structural resilience of shotcrete reinforced coal mines when subjected to low velocity impact loads. Further, this study employs a systematic experimental approach using variable head-free falling impact testing equipment to explore the potential benefits of integrating tuned mass dampers into the support systems of shotcrete reinforced coal mines. The study employs drop weight falling head impact tests with varying drop height of 1.0 m, 1.5 m and 2.0 m to study the influence of the impact energy. It was observed that the peak force characteristics increased for all damped cases with an increase of 15 kN, 18.41 kN and 12.64 kN and corresponding increment of 17.64%, 14.13% and 9.15% respectively as compared to undamped cases in addition to the reduced strain values in coal mine for damped cases under drop weight impact. The findings of this study conclude that after installation of tuned mass dampers the structural damage caused by low velocity impact was reduced and provides valuable insights into the applicability of TMDs and their potential to enhance safety and structural integrity in underground coal mines. [ABSTRACT FROM AUTHOR]

The shear strength of rooted soils depends on the principal stress direction owing to the anisotropy in the soil structure and root system. Existing failure criteria cannot describe the strength anisotropy of rooted soils under general loading conditions because they are mainly based on the test results of direct shear. This study presents a new generalised three-dimensional anisotropic failure criterion for rooted soils. The model employs the projection of two independent microstructure fabric tensors (soil fabric and root network) on the stress tensor. Twenty-four drained triaxial compression and extension tests were carried out to measure the strength anisotropy of silty sand vegetated with vetiver grass (Chrysopogon zizanioides L.) at different overconsolidation ratios and calibrate the material parameters for the proposed criterion. Anisotropies of both cohesion and friction angle exist in rooted soil. Roots contribute mainly to the increase in cohesion (hence root cohesion) from most of the direct shear test data. Roots with predominant orientation aligning in the tensile strain direction contribute the most to soil strength. In the case of vetiver grass, which has a taproot system, their roots show the strongest reinforcement effect in the conventional triaxial extension path, in which the maximum portion of the roots is subjected to tension. [ABSTRACT FROM AUTHOR]

Traditionally, the reliability of a rock slope is evaluated based on the linear Mohr–Coulomb strength criterion, neglecting the nonlinear shear strength of the majority of geotechnical materials. The paper proposes a probability method to assess the reliability of rock slopes based on the power-type nonlinear strength criterion and the mean-value first-order second-moment method. In the proposed method, a novel analytical method to determine the safety factors of slopes with plane failure is derived based on the power-type nonlinear strength criterion. The local mean value of a random variable on the failure surface is determined based on the two-dimensional random field theory, avoiding the random field simulation. To quickly search the minimum reliability index βmin, a dichotomic search method is proposed. The validity of the proposed method is demonstrated in two cases. The study results from the two cases illustrate that the proposed method has high computational efficiency and accuracy. The proposed method offers a fresh way to examine the reliability of rock slopes when the nonlinear strength criterion is adopted. [ABSTRACT FROM AUTHOR]

The tangential displacement amplitude determines the mobilization of shear strength and the deforming and sliding displacements of soil–structure interfaces, and therefore plays a crucial role in the interface behavior. A series of three-dimensional (3D) simple-shear interface tests were conducted between gravel and steel to investigate the influence of tangential displacement amplitude on the tangential deformation, volumetric change, and shear strength. Test results show that deforming and sliding displacements are distinctly induced by shearing. The deforming displacement migrates toward the initial shear direction, caused by the shear orientation effect, and the migration becomes magnified and then stabilizes with cyclic shearing. The shear strength would not be mobilized when the tangential displacement amplitude is relatively small. It behaves in an anisotropic manner if mobilized and gradually degrades as cyclic shearing continues, attributed to the dominant particle crushing over the shear densification effect. Two critical tangential displacement amplitudes are found for the mobilization of shear strength, and determine whether the shear strength could be mobilized during cyclic shearing and whether it is immediately mobilized at initial shearing, respectively. The tangential displacement amplitude primarily affects deforming and sliding amplitudes and their migration, shear stiffness, irreversible and peak reversible normal displacements, peak and residual cyclic shear strength, and anisotropy extent, instead of their relationship patterns. An increased tangential displacement amplitude results in magnified sliding amplitude, decreased deforming weight, accelerated degradation of deforming amplitude, and magnified migration of deforming and sliding displacements. Additionally, large tangential displacement amplitude leads to large irreversible and peak reversible normal displacements, small shear stiffness, and small peak and residual cyclic shear strength. The peak reversible normal displacement is determined by and has a linear relationship with the deforming displacement, and the irreversible normal displacement presents perfect consistency behavior against shear work density, regardless of tangential displacement amplitude. The consistency behavior could be well described using a hyperbolic model, which significantly simplifies the 3D constitutive modeling of the interface. [ABSTRACT FROM AUTHOR]

The matric suction must be measured when calculating the shear strength of unsaturated silt, but the measurement method is cumbersome and time-consuming. The saturation degree of silt is easily measured; therefore, a simplified calculation method for the shear strength of unsaturated silt using the saturation degree instead of matric suction is valuable in practical engineering. A new calculation method based on the saturation degree of silt is proposed to determine the smooth transition from a saturated to an unsaturated state. Suitable parameters for unsaturated Zhengzhou silt are determined, and the results of an unsaturated triaxial test and the soil–water characteristic curve are used to establish the proposed calculation method. A comparison of the results of Vanapalli's method and the simplified calculation method indicates high consistency and a low error. Therefore, the simplified method is more suitable for practical applications than Vanapalli's method. [ABSTRACT FROM AUTHOR]

Most of the previous studies on the behavior of cemented sand were carried out under axisymmetric conditions. In this study, the failure and stress–strain behavior of cemented sand under plane strain conditions were investigated by drained plane strain tests. It was found that the behavior of cemented sand was much affected by its consolidation history, as the bonding began to break when the consolidated stress was larger than the yielding stress during coefficient of lateral earth pressure at rest (K0) consolidation. The growth of the intermediate principal effective stress (σ2′) made the stress–strain curve stiffer and less dilative under plane strain than under axisymmetric conditions. The bonding mobilization during the test was analyzed using an energy-balance approach. The friction between the sand particles and the breaking of the cementation bonding was assumed to dissipate the work done on the cemented sand. The peak friction angle of the cemented sand was not influenced by the cement content (cc), while the effective cohesion increased with the amount of cementation, as indicated by the cc in a power function relationship. In comparison to axisymmetric conditions, plane strain conditions result in a higher friction angle and lower cohesive strength. [ABSTRACT FROM AUTHOR]

Large residual stress induced by significant difference in the coefficient of thermal expansion compromises the mechanical performance of a brazed joint between the WC–Co cemented carbide (YG20) and 3Cr13 stainless steel in a cutting tool of shield machine. In this study, a melamine formaldehyde foam precursor was utilized to produce a 3D hollow carbon foam (HCF) used as interlayer through a high‐temperature carbonization process to aid in the brazing process of YG20 and 3Cr13. First, the morphology and microstructure of the HCF interlayer were revealed as a defect‐rich carbon shell with a hollow structure. Afterward, the effects of introducing the as‐prepared HCF interlayer on the joint microstructure and shear performance were investigated. Results indicate that the HCF interlayer contributed to phase homogenization and, moreover, the residual stress relieving through in situ forming a core (metallic matrix)–sheath (ceramic shell) structure. This method outperformed the direct brazing approach without using an interlayer, with a 41% increase in the joint shear strength due to the synergistic strengthening mechanism of the HCF through residual stress reliving and joint seam toughening. Based on the results, in spite of the residual stress, the fast load transfer and the compensation from the matrix core to the ceramic sheath are responsible for the improved mechanical performance of the joint. [ABSTRACT FROM AUTHOR]

ZrSi2–SiC powder was employed as the joining material to join SiC ceramics in this study. The effects of SiC particle (SiCp) content and joining temperature on the phase composition, microstructure, and shear strength of SiC joints were studied and reported for the first time. Research results showed that introduction of SiCp into the interlayer improved the mechanical performance of the joint. When 10 wt.% SiCp was introduced into the interlayer, the optimal shear strength measured of the joint was 116.7 ± 6.7 MPa under the joining condition of 1500°C for 10 min. With the joining temperature increased, the shear strength of the joint gradually increases. When the joint was performed at 1600°C for 10 min, an ultra‐high temperature phase of ZrC was detected in the interlayer, and the shear strength of the joint was 168.1 ± 12.6 MPa. The SiC joint with high mechanical strength might have the potential for application in the field of nuclear industry. [ABSTRACT FROM AUTHOR]

Currently, the encapsulation of SiC/SiC has been a key technical challenge limiting further application, and YAS-based glass offered a possible solution. In this paper, different CaO-doped Y 2 O 3 –Al 2 O 3 –SiO 2 (YAS) glass solders were prepared and employed to join SiC/SiC. The joints were all structurally dense with the room temperature shear strengths higher than or equal to ∼51.7 MPa. Notably, joints containing 3.0 wt% CaO exhibited increased shear strength of ∼57.1 MPa, and the shear strength at 1200 °C was about 15.8 MPa in an air environment, meeting the requirements of the LOCA conditions. Optimal performance was achieved by using 3.0 % CaO-doped YAS glass to encapsulate SiC/SiC cladding, yielding a continuous, dense encapsulation region with predominantly small closed pores (≤1.0 mm3). Glass infiltration was found in both the end plug and cladding wall. The joints did not leak after 72h of holding pressure at 15 MPa, indicating their excellent air tightness. [ABSTRACT FROM AUTHOR]

A novel sintered-joining of Al 2 O 3 and AlN is achieved for the first time using micro-Ag particle interlayers in air. In comparison with reactive air brazing, this method addresses the issue of reduced strength caused by air holes in brazed joints. Also, this sintered-joining method can be performed at a lower temperature (920 °C), improving the joint strength by relieving the residual stresses. The sintering effect of micro-Ag particles and their high density of dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of Ag and ceramic. Ag–O clusters formed at the interface can be embedded into oxygen vacancies on the ceramic surface, playing a key role in interfacial joining. By optimizing joining temperature, assembly pressure and holding time, a maximum joint shear strength of 85.2 MPa is achieved at 920 °C for 30 min with an assembly pressure of 1 MPa. This study successfully prepares Al 2 O 3 /AlN joints with excellent mechanical properties, providing a reliable foundation for the fabrication of power integrated circuits with efficient operation. [ABSTRACT FROM AUTHOR]

The undrained shear strength of marine sediment is of vital importance because of its critical role in seafloor slope stability, seafloor infrastructure, and influencing sediment dynamics that can lead to underwater landslides. Therefore, understanding the undrained shear strength of marine sediments and its influencing factors is a fundamental requirement for both offshore engineering and geoscience studies. Core data obtained from 198 sites across 46 legs of the Ocean Drilling Program/International Ocean Discovery Program (ODP/IODP) were used to analyze the undrained shear strength of marine sediments and their influencing factors. The undrained shear strength of marine sediments is significantly influenced by the depositional environment. Sediments deposited in active continental margins exhibit a higher undrained shear strength than those deposited in deep-sea and carbonate platform environments due to seismic strengthening and over-consolidation. It was found that fine-grained siliciclastic lithofacies with less than 50% carbonate content exhibited high variability and a rapid increase in the undrained shear strength with depth. In contrast, fine-grained carbonate lithofacies with more than 50% carbonate, as well as reef-facies carbonates, showed low variability and only a gradual increase in undrained shear strength with depth. Additionally, we showed a positive association between the undrained shear strength and physical characteristics including bulk density and P-wave velocity, as well as an inverse correlation with porosity. An exponential relationship was found between these physical properties and the undrained shear strength, with coefficients of determination (R²) values of 0.71, 0.74, and 0.69, respectively. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Immediate dentin sealing (IDS) was introduced to overcome the disadvantages of delayed dentin sealing like pollution of dentin tubules, microleakage, and bond strength destruction over time. The effect of IDS on the bond strength of indirect restorations is still debatable. Purpose: This study was conducted to determine the effect of IDS on the bond strength of ceramic restorations to dentin. Materials and Method: In this systematic review and meta-analysis, the study protocol was registered on the PROSPERO database under the registration number CRD420202014 27. MEDLINE (PubMed), Web of Science, Scopus, and ProQuest databases were searched until January 2021 and updated in January 2022. Worldcat.org and Opengrey.eu, ProQuest dissertation and thesis, and Google Scholar were searched to explore the grey literature. The in vitro studies evaluating the bond strength of ceramic restoration to dentin with and without IDS were included. Seven criteria were assessed to evaluate the risk of bias in the study. Statistical analyses were conducted using RevMan 5.3. The inverse variance method was used to determine the mean difference of micro-tensile bond strength (µTBS) and shear bond strength (SBS). Results: A total of 10 studies (20 datasets) were included in the meta-analysis. Regarding the µTBS analysis, IDS had a significantly higher bond strength than Delayed Dentin Sealing (DDS) (MD:1.16, 95%CI:0.28_2.03, I² =0%). However, no significant difference was found between them in the SBS analysis (MD:0.25, 95%CI: -0.56-1.06, I² =96%). All studies were categorized to have a moderate or high risk of bias. Conclusion: Most in vitro evidence showed favorable results for the effect of IDS on the bond strength and durability of indirect restorations. The adhesive system and the type of ceramic and its treatment before cementation are determining factors. Due to the heterogeneity of the outcomes and studies with a moderate/high risk of bias, the quality of the evidence was low. [ABSTRACT FROM AUTHOR]

This study focuses on the development and testing of a bio-inspired self-burrowing dual anchor soft probe for potential geotechnical applications. Dual anchor refers to the form of movement in soils in which some bivalve molluscs adopted by alternately generating anchoring effects in the soil through shell expansion and fluid-filled feet. By mimicking this mechanism, this study used pneumatic artificial muscles as soft actuators and developed an autonomous burrowing probe. The structure and the performance of the actuators and the probe were investigated and optimized. The burrowing-out process of the dual anchor probe was not a simple upward movement. Instead, it rose in the inflation phase and slipped downward in the deflation phase. The difference between the two was a stride in one single step. In the sands with relative densities of 30%, 50%, and 80%, the total slips accounted for 18.8%, 19.6%, and 26.9% of the total upward movements, respectively. Thus, the entire movement process showed a reciprocating upward trend. The burrowing process could be divided into a restricted stage and a free stage according to whether shear failure occurs in the overlying soil layer. When the soil density was high, the initial stage of burrowing was in a restricted stage. The amount of rise and slip were at a low level and increased slowly as the number of cycles increased. When the burrowing process was in the free stage, the increase was basically stable at a high value and accompanied by small slips. [ABSTRACT FROM AUTHOR]

In this study, the investigation on the influence of Alstonia Angustiloba tree moisture absorption at various depths and separation on the development of persuaded moisture absorption in soil were performed. The slope stabilization analysis were conducted considering two conditions (dry and wet conditions) at two different slope (saturated and unsaturated slope). Besides, the tree moisture absorption data generated during the course of 8 months of on-site monitoring are recorded and applied to assess the safety factor of the slope. Slope stabilization analysis is then performed and represented in two-dimensional and three-dimensional contour model to investigate the effect of plant transpiration on the slope stabilization. According to the findings, at the slope crest with the existence of Alstonia Angustiloba tree, the tree moisture absorption recorded a maximum value, at a distance and depth of 1.1 and 0.25 m. Moreover, the findings also proved that larger tree moisture absorption enhanced the slope's safety factor by up to 53% (from 2.17 to 4.57). The tree moisture absorption can provide an environmentally benign technique that can be used globally to avert slope disaster. [ABSTRACT FROM AUTHOR]

Free-fall penetration (FFP) testing has drawn wide attention in evaluating in-situ undrained shear-strength (Su) of marine clay because it can save time and reduce costs. However, model parameters for interpreting Su are empirical and usually determined based on engineering experience, leading to great uncertainties in Su results. In this study, FFP model tests were conducted using conical, hemispherical and T-shaped penetrometers to gather data. Subsequently, Bayesian theory was employed to ascertain the optimal model parameters. The penetrometer motion state and influencing factors of penetration depth are analysed and discussed. By considering prior knowledge and inherent variability of Su, optimal model parameters for the three types of penetrometers are obtained using maximum likelihood estimation method. The reasons for the different model parameters of three type penetrometers are discussed. In order to assess the effectiveness of the proposed models, field tests were conducted to gather in-situ data. To reduce uncertainty inherent in limited amount of data, a Bayesian updating approach combined with Markov chain Monte Carlo method were used to evaluate posterior distribution of Su of the three penetrometers. Results show that updated Su samples were consistent with those determined by vane shear tests, which verified the reliability of proposed model parameters. [ABSTRACT FROM AUTHOR]

Titanium/bronze bimetal finds broad prospective application in piston pumps in the aerospace field, while joining of titanium alloy to bronze is quite challenging because of the significant difference in the thermophysical properties between these two materials. The present work aimed to fabricate TC6/CuSn10Pb1 bimetal via using hot press diffusion bonding and a CuAgZnCd multi-component alloy as the intermediate layer. The results showed that cracks occurred in TC6/ZCuSn10Pb1 interface without using an interlayer, resulting in low shear strength. A crack-free bonding interface between TC6 and ZCuSn10Pb1 was obtained by using t.e AgCuZnCd as interlayer. During joining of TC6 and ZCuSn10Pb1 with the addition of the CuAgZnCd interlayer, the layered CuSn3Ti5 intermetallic compound was formed near the ZCuSn10Pb1 side of bonding interface at the bonding temperature ranges of 775–825°C, Following bonding at 850°C, a TC6/AgCuZnCd/ZCuSn10Pb1 bimetal without layered intermetallic compounds was obtained, and the intermetallic compounds and solid solution phase in the bonding interface showed fine grain size, resulting in improved strength-ductility synergy of bimetal. Besides, as the bonding temperature increased to 875°C, an obvious layered CuTi4 and Cu2Ti intermetallic compounds formed in the bonding interface, and interface shear strength decreased rapidly. [ABSTRACT FROM AUTHOR]

The traditional methods for enhancing the bearing capacity of loess foundations are limited by high resource consumption and environmental pollution. In contrast, microwave and resistance wire thermal reinforcement has emerged as a more efficient and environmentally responsible alternative. However, existing research on the strength characteristics and micro-mechanisms of microwave and resistance wire thermal reinforcement in wet and soft loess is still limited. To address this gap, this study conducted indoor direct shear tests and undrained compressive strength tests on thermally reinforced loess using strength theory. This research examined the variations in strength characteristics under different heating conditions. The study found that with increasing heating temperature, thermally reinforced loess experienced the following changes: 1) an increase in peak shear stress accompanied by a decrease in shear displacement; 2) an improvement in shear strength; and 3) a transition from plasticity to brittleness in failure characteristics under peak pressure, accompanied by an increase in undrained compressive strength. [ABSTRACT FROM AUTHOR]

Automotive industries have seen increased demands for indirect hot-stamped pre-coated ultra-high-strength steel 22MnB5 due to its excellence. This paper presents the results of experimental investigation of the effect of Al-Si coating weights AS150 (150 g/m2) and AS80(80 g/m2) and spot-welding process parameters of indirect hot-stamped Usibor 1500 to further understand which coating weight perform better for automotive application. The resistance spot welding experiments were conducted with a medium-frequency direct control (MFDC) machine. The MFDC resistance spot-welding machine had two G20 electrodes with a 458 truncated cone designed with a diameter of 4.9 mm. The results show that the nugget diameter increases with increasing weld current, better spot-weld nugget diameter is recorded at weld currents above 7.5 kA for both AS80 and AS150 coating weights, and the weld current range decreases with increase in coating weight and with increase in the interdiffusion layer. Heat treatment dwell time has a remarkable influence on weld current range for both AS150 and AS80 coating weights. AS80 coating weight has a slightly higher weld current range of 2.1 KA than AS150 coating weight with weld current range of 1.8 KA. Tensile shear strength for AS150 and AS80 increases nonlinearly with increase in weld diameter. [ABSTRACT FROM AUTHOR]

The rapid development of aerospace electronics towards lightweight and miniaturized designs has put forward higher requirements for the reliability of device interconnection. It is crucial to study the effects of space radiation and thermal cycle environments on the performance of micro-solder joints. This study uses experimental and simulation methods to study the comprehensive effects of electron irradiation and thermal cycling on the mechanical and electrical properties of Sn-3.0Ag-0.5Cu (SAC305) micro-solder joints. The results show that the combined effect of electron irradiation at a dose of 100 Mrad(Si) and 200 thermal cycles causes the operating temperature of the resistor in the sample to increase while severely reducing the shear strength of the solder joint. Two fracture modes, brittle and plastic, are observed in solder joints during the shearing process. As the number of thermal cycles increases, the proportion of plastic fracture increases. The combined effects of electron irradiation and thermal cycling exacerbate the deterioration of the shear strength of solder joints, with the shear strength of solder joints with brittle fractures decreasing by 28.00% and those with plastic fractures decreasing by 23.34%. [ABSTRACT FROM AUTHOR]

Shear tests are known to be quick tests for heavy wire bonds to evaluate the interconnect quality. The challenge is to interpret the results of such shear tests, in terms of shear strength and the shear code defined by the German Welding Society (DVS). In this study, we aim to get a better understanding of the shear process by studying the material behavior through the shear test of heavy wire bonds. We took two different aluminum wire materials, Al H11 and AlMg0.5, and ultrasonic bonded them on 99.95% copper sheets, resulting in a good bond quality according to the DVS standard. We performed shear tests on these samples, stopping them shortly before final failure. We investigated the resulting deformed state by cross-sections and further instrumental indentation patterns in the middle of the wedge. The indentation hardness patterns revealed that Al H11 and AlMg0.5 behave significantly differently in terms of hardening under deformation. Our experiments show that the different material behavior has an influence on the failure path of the shear tests. We conclude, when comparing different materials by means of shear test results, that the outcome is influenced by the different hardening behavior. [ABSTRACT FROM AUTHOR]