Calculated Bond Strength Research Articles

Uranium solid performance test of butterfly rebar-corrugated pipe slurry hoe connection

To provide a theoretical basis for the application of spiral reinforcement-corrugated tube grout-pin connection in prefabricated structures, 21 pin-fixed pull-out specimens were designed and manufactured. Through unidirectional pull-out tests, the failure mode, load-displacement curve and the influence of different influencing factors on the bond pin-fix strength of the specimens were analyzed. The bond strength calculation formula of spiral reinforcement-corrugated tube grout-pin connection was fitted, and the recommended value of the pin-fix length was proposed. The test results show that the failure modes of the specimens are mainly steel bar pull-out, crack pull-out, steel bar breakage and rib breakage; the bond strength decreases with the increase of pinning length and steel bar diameter; with the increase of corrugated pipe diameter, the bond strength changes nonlinearly with the steel bar diameter, and the pinning performance is best when the diameter is 50 mm and 60 mm; the average ultimate bond strength increases with the increase of grouting material strength and the pinning length can be further shortened to 5 d; in engineering applications, when the steel bar diameter is not greater than 16 mm, it is recommended that the pinning length be 5 d∼7 d, the aperture ratio be 2.5∼4.28, and when the grouting material strength is , the pinning length should not be less than fcu≥80MPa5 d.

Pullout behavior of polyethylene fiber from cement matrix: Effect of embedment length, matrix strength, and inclination angle

Engineered cementitious composites reinforced with polyethylene fibers (PE-ECC) exhibit the potential for high strength and toughness. To optimize the performance and tailor the properties of PE-ECC, this study focuses on analyzing the pullout behavior of polyethylene (PE) fibers from matrices through single fiber pullout tests and scanning electron microscopy analysis. One fiber type was used throughout the experiment, while three embedment lengths and three inclination angles were considered to investigate the pullout behavior from high-strength matrices. Furthermore, the pullout response from matrices with middle and low strength was examined, considering two embedment lengths. The results indicate that fibers with shorter embedment lengths exhibit lower pullout loads but higher energy absorption capacities. High matrix strength enhances adhesion and friction at the fiber-matrix interface, resulting in plumper pullout load versus slip curves. Owing to snubbing and matrix spalling effects, as the inclination angle increases, both the peak load and slip at the peak load of the inclined fibers exhibit an exponential increasing trend. Additionally, following the peak load, the pullout load of inclined fibers decreases more gradually than that of aligned fibers, and the energy absorption capacity of inclined fibers is significantly improved. Ultimately, general equations are derived for the calculation of pullout work and equivalent bond strength.

Study on the effect of strain rate on the bond performance between GFRP bars and ECC after seawater freeze-thaw cycles

With the increase in marine and coastal infrastructure in cold regions, freeze-thaw damage and dynamic loads will reduce structural performance. However, the dynamic bonding performance of seawater sea sand ECC and glass fiber-reinforced polymer (GFRP) bars after freeze-thaw cycles is still unclear. In this paper, the mass loss rate, dynamic elastic modulus, and compressive strength of seawater sea sand ECC were studied through freeze-thaw cycle tests. The bonding properties of seawater sea sand ECC and GFRP bars were examined under two freeze-thaw environments (Seawater environment, Freshwater environment), four freeze-thaw cycles (0, 50, 100, and 150), and four strain rates (2.63 × 10−5s−1, 2.63 × 10−4s−1, 2.63 × 10−3s−1, and1.32 × 10−2s−1) using pull-out tests. Additionally, the microstructure was analyzed using SEM. The results show that compared with the freshwater freeze-thaw cycle, the seawater freeze-thaw cycle deteriorates the surface peeling resistance and mechanical properties of seawater sea sand ECC. Compared with the non-freeze-thaw specimens, the failure mechanism after freeze-thaw cycles changed from the gradual increase of bond strength with the increase of strain rate to the gradual decrease. Compared with the dynamic elastic modulus, compressive strength, and bond strength freeze-thaw damage model based on the Weibull distribution, it was observed that the predicted life of compressive strength is overestimated, while the predicted life of bond strength is underestimated. The bond strength and slip calculation models for freeze-thaw cycles and strain rates have been established. This provides a theoretical foundation for predicting the structural service life and conducting durability research on ECC and GFRP bars in seawater and sea sand.

To evaluate the effect of different enamel conditioning procedures on the shear bond strength of new metal bracket on previously debonded tooth surface - An in-vitro study

To evaluate the efficacy of different enamel conditioning methods while bonding a new bracket on a previously de-bonded site, and assess the difference in shear bond strength and ARI score if any. 125 human-extracted premolars were selected. 250 premolar brackets were procured. 125 brackets were bonded on the buccal surface of the premolars using different enamel conditioning methods (bonding sequence 1) and was followed by debonding using the Instron Universal testing machine (Debonding procedure I).The remaining 125 brackets were bonded (Bonding sequence II) on the same teeth after the removal of residual adhesive. Bonding sequence II was followed by debonding (Debonding procedure II), shear bond strength calculation, and ARI score calculation. There was a significant difference in SBS between the 5 groups after initial debonding. SEP group (group 4) showed the highest SBS followed by acid etching groups (groups 3, 2, and 1). The sandblasting group (group 5) had the lowest shear bond strength value. After the second debonding, SBS was found to be highest in Group 3 {37% o-phosphoric acid (Bonding I) sandblasting (Bonding II)} followed by Group 4 {SEP (Bonding I and Bonding II)}, group 2 {acid etching (Bonding I) SEP (Bonding II)}, and group 1 (acid etching in both bonding sequences). Group 5 (sandblasting in both sequences) had the least SBS. Non-significant differences were found in ARI score of the five groups. Self-etching primer group had highest SBS and sandblasting group had least SBS after first debond. The SBS of new brackets after two debonding procedures significantly decreased but was still found to be above the required bond strength. SEP and sandblasting can be used as a substitute to acid etching technique in second time bonding of brackets as these groups had higher SBS after second debond.

Experimental investigation on interfacial bonding performance between cluster basalt fiber and cement mortar

To fully understand the action mechanism of basalt fiber (BF) in matrix, so that basalt fiber reinforced concrete (BFRC) can be more widely used in engineering, it is necessary to study the bonding performance between BF and matrix. The interfacial bonding performance between cluster basalt fiber (CBF) and cement mortar were investigated by fiber pull-out test, acoustic emission (AE) technology and digital image correlation method (DICM). The failure modes and surface micro-morphology of pulled-out fibers were analyzed by scanning electron microscope (SEM). The results indicate that as the BF bundle quantity and fiber embedded depth increase, pull-out load increases obviously, while calculated bond strength decreases significantly. Specimens with double BF bundle and larger fiber embedded depth can absorb more interfacial rupture energy. More hydrate particles on the surface of pulled-out BF bundles under higher pull-out load. The variation rules of AE energy and accumulated ring count can accurately predict different test stages. The peak frequencies of AE signal are mainly concentrated in the bands of 0–100 kHz, 200–300 kHz and 420–480 kHz. The changing trend of interface strain can be accurately expressed by the change rule of surface strain. This paper provides a new idea for studying the bonding performance between fiber and matrix.

Bond strength of sand-coated deformed GFRP bars in UHPC, HPC, and NC

This paper focuses on evaluating the bond strength of sand-coated deformed Glass Fiber-Reinforced Composite (GFRP) bars in cement-based materials: Ultra-High Performance Concrete (UHPC), and High-Performance Concrete (HPC) and Normal Concrete (NC). A total of 48 pullout tests were conducted to examine the impact of parameters such as bond length (2.5db, 5db and 10db) and cover thickness (1db, 2db and 4.5db). Three common failure modes comprising bar pullout, rupture, and cover splitting were outlined, in which, pullout of GFRP rebars was controlled by shear damage between the resin and glass fibers, and UHPC splitting behaved with greater ductility than HPC or NC. The bond-slip curve of GFRP rebars involved the micro-slippage branch, the slippage branch, the exponentially descending branch, and the residual branch with oscillation characteristics. In comparison with HPC and NC, GFRP bars in UHPC showed 27.9%-72.6% and 130.5%-164.2% increases in bond strengths, respectively. Moreover, the higher bond strength was achieved in specimens with a smaller bond length or greater cover thickness. Specifically, bond strengths in samples having covers of 4.5db and 2db were enhanced by 30.8%-53.4% and 16.2%-26.8% to those with a cover of 1db. Furthermore, the bond strength calculation formula for GFRP rebars in UHPC was established and validated using the existing tests, and some design recommendations were presented.

Experimental research on interfacial bonding performance of high‐strength steel pipe and surrounding concrete/grout for assembled composite columns

AbstractHigh‐strength steel pipe joints are proposed for assembled composite columns. The steel pipe extends into the upper and lower prefabricated columns and is anchored by poured concrete or grout to realize the connection of the prefabricated columns. Bonding performance of high‐strength steel pipe and surrounding concrete/grout is critical to the joint reliability. Steel pipe push‐out test was carried out, considering parameters of steel pipe section specification, bonding length, bonding material, and outer wall treatment of the steel pipe. Comparative analysis of measured load–displacement/slip curves and calculated bond strength were conducted. Bonding length of 600 mm could provide sufficient bond strength. Increasing bonding length could delay the slippage, but the bond strength decreased. High‐strength grout significantly increased the peak load size. The slenderness ratio and diameter–thickness ratio of the steel pipe had no obvious influence on the bonding performance. Steel pipe with D114*25 section obtained higher bonding strength with smaller ratio of bonding area to cross‐sectional area. Spiral ribs welded to the outer wall of the steel pipe could effectively improve the bonding strength and delay the interface slip. With easy construction and reliable performance, spiral ribs were recommended to be applied in prRactical projects.

Experimental Study on the Bond Performance between Glass-Fiber-Reinforced Polymer (GFRP) Bars and Concrete

By investigating the bond performance between glass-fiber-reinforced polymer (GFRP) bars and concrete, GFRP bars can be better applied to concrete structures as a building material. This paper considered the effects of three different GFRP bar surface treatments, three bonding lengths, corrosive solution, and immersion time on the bonding strength. The test results indicated that the bond strength decreases with the increase in the diameter and bond length. The bonding between GFRP bars and concrete can be improved by treating the surface of the bars in different ways. Compared with the control group, the bond strength of the specimens in the saline solution decreased by 1.3–21.4%, and the bond strength of the specimens in the alkaline solution decreased by 26.5–38.8%. In the corrosive environment, the bond properties are degraded. A bond strength calculation formula considering the surface treatment method of the GFRP bars was proposed. The prediction formula of the bond strength retention rate between the GFRP bar and concrete in the corrosive environment was established. The formula was validated with the available research data and the calculated values agreed well with the test values. The MBPE model and CMR model are modified to establish the bond-slip model of the GFRP bars and concrete in the corrosive environment. The model curve is close to the test curve. This paper provides a theoretical basis for future research on the bond-slip performance of GFRP bars and concrete.

Correlative Theoretical and Experimental Study of the Polycarbonate | X Interfacial Bond Formation (X = AlN, TiN, (Ti,Al)N) During Magnetron Sputtering

AbstractTo understand the interfacial bond formation between polycarbonate (PC) and magnetron‐sputtered metal nitride thin films, PC | X interfaces (X = AlN, TiN, (Ti,Al)N) are comparatively investigated by ab initio simulations as well as X‐ray photoelectron spectroscopy. The simulations predict significant differences at the interface as N and Ti form bonds with all functional groups of the polymer, while Al reacts selectively only with the carbonate group of pristine PC. In good agreement with simulations, experimental data reveal that the PC | AlN and the PC | (Ti,Al)N interfaces are mainly defined by interfacial C─N bonds, whereas for PC | TiN, the interface formation is also characterized by numerous C─Ti and (C─O)─Ti bonds. Bond strength calculations combined with the measured interfacial bond density indicate the strongest interface for PC | (Ti,Al)N followed by PC | AlN, whereas the weakest is predicted for PC | TiN due to its lower density of strong interfacial C─N bonds. This study shows that the employed computational strategy enables prediction of the interfacial bond formation between PC and metal nitrides and that it is reasonable to assume that the research strategy proposed herein can be readily adapted to other organic | inorganic interfaces.

Theoretical Investigation of the Properties of Pd2Cu Intermetallics and CO2 Hydrogenation to Ethanol Catalyzed on Pd2Cu (110)

Intermetallics or ordered alloys are catalytically more advantageous than solid solution alloys. The B2 phase Pd2Cu intermetallics exhibit excellent catalytic properties for CO2 hydrogenation to ethanol and other reactions. However, the crystal structure of Pd2Cu is unknown. With a self-coded program based on symmetry and atomic ratio, we combed and identified the Pd2Cu structure. The calculated (110) interlayer distance agrees with the experimental result acceptably. Lattice dynamics and AIMD simulations demonstrate the identified structure is stable. The calculated bond strength indicates that among the five types of bonds, the shorter Pd–Cu bond (SPd–Cu) plays the most important role in stabilizing the structure. Crystal orbital Hamilton population (COHP) analyses reveal that the 5s(Pd)–4p(Cu) interaction dominates the Pd–Cu bonding and the 5s(Pd)–5s(Pd) or the 4p(Cu)–4p(Cu) interaction contributes the most in the homonuclear Pd–Pd and Cu–Cu bonds. Investigations on the reaction mechanism proposed for CO2 hydrogenation to CH3CH2OH show that CH2OH to CH2+OH is the key step determining the production of ethanol, followed by CO2+H to COOH and COOH to CO+OH.

Exploring the behaviors and social preferences of a large, multigenerational herd of zoo-housed southern white rhinoceros (Ceratotherium simum simum).

The zoo-housed southern white rhinoceros (SWR) population is of special concern due to their lack of consistent breeding success. An enhanced understanding of SWR social preferences could better inform management planning by promoting natural social relationships, which can positively affect their well-being. The large, multigeneration herd housed at the North Carolina Zoo provides an ideal opportunity to examine rhino sociality across different ages, kin types, and social groupings. Eight female rhinos' social and nonsocial behaviors were recorded from November 2020 through June 2021 across 242 h. Activity budget analyses revealed strong seasonal and temporal variations in grazing and resting behaviors, with no stereotypic behaviors recorded. Bond strength calculations suggested that each female maintained strong social bonds with one to two partners. Beyond mother-nursing calf bonds, we found that the strongest social ties were maintained between calf-less adults and subadults in these dyads. Considering these findings, we recommend that management plans attempt to house immature females with calf-less adult females, as they may be necessary to the social landscape of immature females and, ultimately, improve their welfare.

Shear Bond Performance at Interface of Concrete-Filled Steel Tube after Freeze-Thaw Cycles.

The shear bond performance between steel tube and concrete is the basis of a synergistic effect between two materials. When a concrete-filled steel tube structure is damaged by freeze and thaw cycles, the shear bond performance will deteriorate, which will inevitably affect the safety of the structure. In this paper, the effects of the numbers of freeze–thaw cycles, section type of steel tube, and concrete strength on the failure mode, bond strength, and peak slip of concrete-filled steel tube are investigated. In addition, the load–slip curve, the shear bond strength calculation formula, and the peak slip calculation formula are obtained. The results show that the shear bond performance decreases with the increase in freeze and thaw cycles; after 20 freeze and thaw cycles, the shear bond strength of the round steel tube specimen with 30 MPa decreases by 33.33%, while that of peak slip increases by 11.49%; the shear bond strength increases with the increase in concrete strength, while the degree of decrease in shear bond strength after freeze–thaw cycles is reduced; the shear bond strength of the round steel tube push-out specimen is higher than that of square steel tube push-out specimen, and after 20 freeze and thaw cycles, the shear bond strength of the round steel tube push-out specimen with 30 MPa/45 MPa is 0.86 MPa/1.62 MPa, while that of square steel tube push-out specimen with 30 MPa/45 MPa is 0.40 MPa/0.50 MPa.

Bond Properties of Deformed Rebar in Frost-Damaged Recycled Coarse Aggregate Concrete under Repeated Loading

The bond properties of deformed rebar in frost-damaged recycled coarse aggregate concrete (RAC) under repeated loading (R-L) was studied. It is found that the bond failure modes of specimens for R-L is similar to that for monotonic loading (M-L), whereas the crack width for R-L is larger than that for M-L. The bond strength has a tendency to decrease after frost damage, whereas the peak slip has a tendency to increase, whether under R-L or M-L. The bond strength under R-L is lower than that under M-L, whereas the peak slip under R-L is higher than that under M-L. The experimental results of the pullout specimens in water are contrasted with that in salt solution. Through contrasting research, the frost-damage resistance coefficient and the R-L resistance coefficient in salt solution are lower than that in water, whereas the rebar slip in salt solution is higher than that in water. An ultimate bond strength calculation expression of deformed rebar in frost-damaged RAC under R-L is presented.

Bond-slip behaviour of lightweight aggregate concrete based on virtual crack model with exponential softening characteristics

A theoretical analytical model of bond stress-slip between lightweight aggregate concrete and rebar is presented by using the virtual crack model of fracture mechanics to analyze the nonlinear exponential softening characteristics of lightweight aggregate concrete in this paper. Various critical points at different stages are calculated by using simplified expressions. Moreover, a theoretical analytical model for bond-slip mechanism considering the effect of the stirrup is additionally presented. To simulate the relationship of bond stress-slip, a Python program is developed to generate connectors between rebar and concrete corresponding nodes. Furthermore, a three-dimensional finite element model is also developed to consider the impact of radial stress around the rebar. Compared with the bond stress-slip curves of experimental results, the theoretical analytical model of bond-slip behavior effectively reflects the interaction of rebar and lightweight aggregate concrete, and the three-dimensional finite element model demonstrates how cracks within lightweight aggregate concrete expand. At the interface between lightweight aggregate concrete and rebar, the bond stress is not uniformly distributed alongside the bond length. Due to the inhomogeneity of the bond stress, the bond strength calculation equation needs to be modified. Meanwhile, the modified results are well consistent with the bond-slip test.

Adhesive Bond Strength Calculation of Reinforcing Fibers with Polymers by the “Loop” Method

Adhesive Bond Strength Calculation of Reinforcing Fibers with Polymers by the “Loop” Method

Trigger bond analysis of azo‐based energetic materials

Azo-based energetic materials may initiate explosive decomposition by extruding molecular nitrogen to produce radical fragments. Density functional theory and Wiberg bond index analysis were used to determine trends in bond strength for a series of aromatic azo compounds. Interactions between ortho ring hydrogens and an azo nitrogen lone pair favor a planar molecule with a strengthened azo linkage. Steric groups substituted ortho to the azo linkage cause the molecule to twist, which disrupts delocalization of the π density and weakens the CNazo bond. The results of this study are generally consistent with the low sensitivity of various aromatic azo-based energetic materials. Discrepancies between calculated bond strengths and the experimental impact sensitivities could be attributed to packing forces that affect molecular planarity in the solid state.

The effects of nanostructures on lithium storage behavior in Mn2O3 anodes for next-generation lithium-ion batteries

Nanostructured materials for lithium-ion batteries (LIBs) have many advantages over bulk electrode materials, and therefore, such materials should be effectively utilized in next-generation batteries. Herein, we identify that the superior performances of mesoporous Mn2O3 results from the different lithium storage behaviors of mesoporous and bulk Mn2O3. X-ray absorption spectroscopy (XAS) and bond strength calculation show that mesoporous Mn2O3 has a larger capacity than bulk Mn2O3 owing to an additional oxidation of Mn2+ to a higher oxidation state during charging, as well as an additional reversible reaction during cycling because the weaker Mn–O bond strength of mesoporous Mn2O3 requires much less strength to break or form atomic bonds during the electrochemical reactions. Furthermore, the combined results of X-ray photoelectron spectroscopy and soft XAS indicate that an additional lithium storage reaction through the reversible formation–decomposition of the electrolyte-derived surface layer occurs more in mesoporous Mn2O3 than in bulk Mn2O3. Consequently, the improvement in the lithium storage behavior of mesoporous Mn2O3 due to the increasing specific surface area and decreasing particle size with the progression of cycles, also affects their cycle performances. This study provides a better understanding of the synergistic relationship between nanostructures and the electrochemical performances of anode materials for LIBs.

Surface etching and silane heating using Er:YAG and Nd:YAG lasers in dental ceramic luted to human dentin

AbstractInvestigate the tensile bond strength, surface morphology, and wettability of reinforced glass‐ceramic etched with high power laser at different protocols and luted to human dentin. Fifty carious‐free human molars were used in this study and distributed in five groups according to surface etching: (Control [HF10% + Silane]; Er [Er:YAG + Silane]; Sil + Er [Silane + Er:YAG]; Nd [Nd:YAG + Silane]; and Nd + Sil [Silane + Nd:YAG]). After, the tensile bond strength test was performed. Three specimens per group were used to perform the surface morphologies by using scanning electron microscopy analysis and wettability by using the sessile drop technique. Failure modes were determined. Data were analyzed with two‐way analysis of variance and Tukey tests, with α = .05. The bond strength data showed statistically significant differences among tested groups for the laser and silanization technique type (p < .001). The highest calculated bond strength values were obtained with Er (19.25 ± 3.70 MPa) followed by Sil + Er (14.11 ± 4.11 MPa), Control (9.42 ± 2.27 MPa), Nd (9.66 ± 2.02 MPa), and Nd + Sil (6.71 ± 1.88 MPa), respectively. The silane application prior to the laser irradiation showed an inferior bond strength compared to the conventional silanization technique. The surface etching using Er:YAG laser showed promissor results for the lithium disilicate.

Using genetic programming to model the bond strength of GFRP bars in concrete under the effects of design guidelines

Purpose This paper aims to use a derivative of genetic programming to predict the bond strength of glass fiber-reinforced polymer (GFRP) bars in concrete under the effects of design guidelines. In developing bond strength prediction models, this paper prioritized simplicity and meaningfulness over extreme accuracy. Design/methodology/approach Assessing the bond strength of GFRP bars in concrete is a critical issue in designing and building reinforced concrete structures. Findings Ultimately, the equation of a linear form of a particular design guideline was suggested as the optimal prediction model. Improvements to the current design guidelines suggested by this model include setting a 1.31 magnification and considering the effects of the three significant parameters of bar diameter (db), minimum cover-to-bar diameter (C/db) and development length to bar diameter (l/db) under an acceptable root mean square error accuracy of around 2 MPa. Furthermore, the model suggests that the original influence parameter of concrete compressive strength (fc) may be removed from bond strength calculations. Originality/value The model suggests that the original influence parameter of concrete compressive strength (fc) may be removed from bond strength calculations.

Evaluation of Zirconia Infused Glass Ionomer Cement Versus Resin Modified Glass Ionomer in Class II Restorations of Primary Molars

Objective of this study to was to evaluate zirconia infused glass ionomer cement versus resin modified glass ionomer in class II restorations of primary molars.Materials & Methods: This study was classified in to vivo and vitro study. I- vivo study: 18 posterior primary molars from 9 children by using split mouth technique was classified equally in to two groups. Group 1: 9 deciduous molars were restored with resin-modified glass-ionomer (RMGI) filling. Group 2: 9 deciduous molars were restored with zirconia infused glass-ionomer (ZRGI) filling. Follow up using the FDI criteria to evaluate the clinical performance of both materials. II- vitro study: 18 freshly extracted human deciduous molars with no crack, decay or structure deformities were collected and stored in normal saline. Group 3: 9 extracted deciduous molars were restored with resin-modified glass-ionomer filling. Group 4: 9 extracted deciduous molars were restored with zirconia- infused glass-ionomer filling. The measures were calculated by Shear bond strength and Wear resistance calculation. Results: It was found that that RMGI is better in shear strength than zirconia infused glass ionomer, while the two materials have the same resistance to wear. Conclusion: Shear Bond strength of RMGI is better than zirconomer. There is no significant difference in wear resistance between the two materials. Clinical performance of RMGI is better than zirconomer.