Tensile Shear Strength Values Research Articles

Advances in small-scale resistance spot welding of the Ni-15 %Fe-4 %Mo-1 %Mn permalloy in the production of low-noise ring cores for fluxgate magnetometers

The aim of this study was to assess the possibility of improving control of small-scale resistance spot welding (SSRSW) of the Ni-15 %Fe-4 %Mo-1 %Mn permalloy in the production of low-noise ring cores for fluxgate magnetometers. It was found that the range of the optimal current–time parameters (weld lobe) was within current amplitudes of 1–2 kA and pulse durations of 6–14 ms, which allowed to form sound nuggets with sufficient diameters but without expulsions in most cases. A preheating stage (a pulse with an amplitude of about 1 kA and a duration of 3–4 ms) had a positive effect on the stability of both dimensions and mechanical characteristics of the investigated nuggets. A decrease in the solidification rate slightly improved the stability of tensile shear strength values of the SSRSW joints despite the absence of fundamental differences in the microstructure and phase composition of the weld metals. To determine the reliability of predicting the quality of the SSRSW joints by assessing dynamic resistances measured during the formation of nuggets, a comparative statistical analysis of their diameters and the tensile shear strength values was carried out. The obtained results did not reveal any strong correlation between these parameters.

Metal-Metal Bonding Process Research Based on Xgboost Machine Learning Algorithm.

Conventionally, the optimization of bonding process parameters requires multi-parameter repetitive experiments, the processing of data, and the characterization of complex relationships between process parameters, and performance must be achieved with the help of new technologies. This work focused on improving metal-metal bonding performance by applying SLJ experiments, finite element models (FEMs), and the Xgboost machine learning (ML) algorithm. The importance ranking of process parameters on tensile-shear strength (TSS) was evaluated with the interpretation toolkit SHAP (Shapley additive explanations) and it optimized reasonable bonding process parameters. The validity of the FEM was verified using SLJ experiments. The Xgboost models with 70 runs can achieve better prediction results. According to the degree of influence, the process parameters affecting the TSS ranked from high to low are roughness, adhesive layer thickness, and lap length, and the corresponding optimized values were 0.89 μm, 0.1 mm, and 27 mm, respectively. The experimentally measured TSS values increased by 14% from the optimized process parameters via the Xgboost model. ML methods provide a more accurate and intuitive understanding of process parameters on TSS.

In-situ modification of low molar ratio urea–formaldehyde resins with cellulose nanofibrils for plywood

This study describes the in-situ modification of low molar ratio urea–formaldehyde (UF) resins with cellulose nanofibrils (CNFs) to improve the poor performance of resins synthesized with different methods (Synth 1 and Synth 2) when adding second urea. UF resins were in-situ modified with CNFs dissolved in a mixture of dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) during the alkaline reaction step. Results showed that CNF addition enhanced the resin properties, such as shorter gelation time, faster curing rates at low activation energy, higher tensile shear strength (TSS), and lower formaldehyde emission (FE), compared to those of neat resins. The dry and wet TSS values of plywood bonded with UF resins modified with 3% CNFs synthesized using Synth 2 increased by 30% and 42%, respectively, and the FE value was decreased by 22% and 42%, respectively. These results reveal that in-situ modified UF resins with CNFs showed better performance than neat UF resins and that Synth 2 was more favorable than Synth 1.

Shear strength of beech wood joints bonded with commercially produced PVAc D3 adhesives

One of the most commonly used adhesive types in nonstructural applications of wood, with many advantageous characteristics, is polyvinyl acetate (PVAc), which is produced in four different classes (D1-D4), according to its durability to humidity and climatic conditions. In this study, six of the most commonly used and worldwide commercially available brands of PVAc wood adhesives of D3 durability class, of different cost and origin (locally produced or imported), were obtained from the market, aiming to study and compare the “wood to wood” adhesion ability of beech wood, which is one of the most important species used in furniture production in Europe, and assess the quality of the produced gluelines, according to standards [EN 204, EN 205]. Three different conditioning treatment processes were applied to these 6 D3-PVAc adhesives lap joint specimens the “tensile shear strength” of the specimens was determined, while after their destruction, the “wood failure” percentage was visually assessed on the bonding surfaces. According to the results, the tensile shear strength values of the joints ranged between 11.48 and 13.18 N/mm2, revealing satisfying adhesion strength for all the different cases of adhesive brand and process applied after adhesion, meeting the requirements of the standard for D3 durability class categorization. The factor of “adhesive brand type” affected significantly the shear strength values, whereas neither the “conditioning treatment” applied to the specimens, nor the interaction between the two factors of “adhesive brand type” and “treatment”, revealed a significant effect on the shear strength values of the specimens, indicating a good bonding performance, either under ambient conditions or under conditions of high humidity environments. The differences in the adhesives prices (euro/100 g), origin and other technical characteristics (viscosity, solids content), did not affect the shear strength of the joints. The satisfying bonding quality of the studied adhesives was verified by the high “wood failure” percentages recorded on almost all the specimens, as well as the stereoscopically observed bonding lines, suggesting the high potential of resistance to humidity and aging effect, which could extend even more the applications range of such environmentally friendly adhesives.

Single‐phase photo‐cross‐linkable adhesive synthesized from methacrylic acid‐grafted 1‐decene/9‐decene‐1‐ol cooligomer

AbstractThe cooligomerization of 1‐decene with 9‐decene‐1‐ol was conducted by using a Ti amine bis‐phenolate catalyst. Light‐curable adhesive was prepared by the reaction of methacryloyl chloride with the hydroxyl groups of the synthesized cooligomer, which led to the introduction of photo‐polymerizable CC double bonds into the cooligomer chains. Comonomer insertion into 1‐decene oligomeic chains and also methacryloyl chloride reaction with cooligomer were confirmed by both FT‐IR and NMR spectroscopy. Three‐point bending analysis results of cured adhesive sample (cured with blue light) showed flexural modulus and flexural strength values of 1.41 GPa and 1.66 MPa, respectively. Maximum weight loss temperature of 444°C showed high thermal stability of cured adhesive sample. In order to explore adhesion abilities of the synthesized adhesive to different substrates including polymethylmethacrylate (PMMA), polycarbonate (PC), polystyrene (PS), nylon and aluminum (Al), tensile shear bond strength, and peeling tests were conducted. Synthesized adhesive demonstrated tensile shear strength values of 1.28, 1.95, 1.10, 2.15, and 2.42 N/mm2 for PMMA, PC, PS, nylon, and Al substrates, respectively. Furthermore, obtained adhesive indicated greater tendency to polar substrates in comparison to nonpolar ones by the factor of 16–95%. Obtained results suggested a new photo‐curable adhesive with privileged features, which has capability to be used in high temperature applications.

Microencapsulation of polymeric isocyanate for the modification of urea-formaldehyde resins

This study was conducted to prepare the microcapsules of polymeric 4-4 diphenyl methane diisocyanate (MpMDI) by interfacial polymerization using two different surfactants (Tween 40 and Gum Arabic) for the modification of urea-formaldehyde (UF) resins. MpMDI obtained by Tween 40 (TW-MpMDI) were spherical, smooth, and small diameter, while those prepared by Gum Arabic (GA-MpMDI) were irregular, rough surface, and larger diameter. Attenuated total reflection–Fourier transform infrared (ATR-FTIR) spectra of two types of MpMDIs confirmed the successful microencapsulation of pMDI by detecting the isocyanate (NCO) groups after rupturing the shell of MpMDIs. As the MpMDI content in UF resins increased, the non-volatile solids content, pH, gelation time, viscosity, and exothermic peak temperature of UF/MpMDI adhesives slightly increased. Plywood bonded with UF/MpMDI adhesives had 15% higher tensile shear strength (TSS) and 30% higher modulus of rupture (MOR) than those of the plywood bonded with neat UF resins owing to the formation of urethane (HN-(CO)–O-R) bonds. In particular, plywood bonded with UF/TW-MpMDI had higher TSS and MOR values than those bonded with UF/GA-MpMDI adhesive. Regardless of the surfactant types, the formaldehyde emission decreased about 54% with 5% MpMDI addition into UF resins. These results and statistical analysis revealed that 1% TW-MpMDI addition into UF resins provided a proper balance between good adhesion and low formaldehyde emission for plywood.

Improved method for analyzing cohesive strength development of pMDI

Analyzing the development of cohesive strength of polymeric diphenylmethane diisocyanate (pMDI) with the help of the small-scale test method proposed in the standard (ASTM-D7998-15) is rarely used, as resulting lap-shear strength values are lacking in informative value. Up to now, the gained strength values have been dramatically below the ones typically achieved with most standard wood adhesives, while the performance in a panel product is at least of equal quality. In order to address this discrepancy and to fill the gap of the lacking method to properly investigate curing behavior of pMDI adhesives, a modification of the specimen geometry for pMDI adhesive analysis is proposed, resulting in meaningful tensile shear strength values also when using pMDI as adhesive. Applying this modified specimen geometry enables investigating relevant processing parameters, such as the effect of press time, press temperature and wood moisture content on the tensile shear strength development using pMDI. The strength development was found to be positively affected by all three factors significantly. Furthermore, the calculated reactivity index showed a decrease in activation energy of 20% with increasing wood moisture content. Based on the results gained, it can be concluded that both, wood moisture and temperature, are crucial factors to accelerate curing of pMDI. Even so the principle influence of the exemplary selected parameters has already been shown earlier, the new methodology opens up new possibilities in investigating the curing behavior of pMDI.

Ammonium Lignosulfonate Adhesives for Particleboards with pMDI and Furfuryl Alcohol as Crosslinkers.

Tightening formaldehyde emission limits and the need for more sustainable materials have boosted research towards alternatives to urea-formaldehyde adhesives for wood-based panels. Lignin residues from biorefineries consist of a growing raw material source but lack reactivity. Two crosslinkers were tested for ammonium lignosulfonate (ALS)—bio-based furfuryl alcohol (FOH) and synthetic polymeric 4,4′-diphenylmethane diisocyanate (pMDI). The addition of mimosa tannin to ALS before crosslinking was also evaluated. The derived ALS adhesives were used for gluing 2-layered veneer samples and particleboards. Differential Scanning Calorimetry showed a reduction of curing temperature and heat for the samples with crosslinkers. Light microscopy showed that the FOH crosslinked samples had thicker bondlines and higher penetration, which occurred mainly through vessels. Tensile shear strength values of 2-layered veneer samples glued with crosslinked ALS adhesives were at the same level as the melamine reinforced urea-formaldehyde (UmF) reference. For particleboards, the FOH crosslinked samples showed a significant decrease in mechanical properties (internal bond (IB), modulus of elasticity (MOE), modulus of rupture (MOR)) and thickness swelling. For pMDI crosslinked samples, these properties increased compared to the UmF. Although the FOH crosslinked ALS samples can be classified as non-added-formaldehyde adhesives, their emissions were higher than what can be expected to be sourced from the particles.

Mechanical Properties of Dissimilar A356/SAPH440 Lap Joints by the Friction Stir Spot Welding and Self-Piercing Riveting

Aluminum alloy A356-T6 and automotive steel sheet SAPH440 were joined using friction stir spot welding and self-piercing riveting. The maximum tensile shear strength values in weld joints were approximately 3.5 kN at a rotation speed of 500 rpm and plunge depth of 1.0 mm. It was confirmed that the intermetallic compound layer of weld joints below 9.23 μm did not exceed the permissible thickness 10 μm of Al–Fe joints. The self-piercing riveting joints exhibited maximum tensile-shear strength of 7.9 kN, which was higher than that of the weld joints. However, during the riveting process, cracking appeared in the joint on the aluminum side, which was caused by lack of ductility of cast aluminum. In addition, it was observed that the cracks on the aluminum side were getting larger, as the radius of the lower mold increased.

Amino Group Bearing Organic–Inorganic Hybrid Materials for Joining Aluminum Alloys and Thermoplastic Fiber‐Reinforced Parts

The production of metal‐based hybrid laminates, such as aluminum combined with thermoplastics like polyamide 6, requires a precise and purposeful design of the interface between the two components. The utilization of twin polymerization has been successfully examined and an improved adhesion behavior is shown. By utilizing the monomers 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] and 2‐(3‐amino‐n‐propyl)‐2‐methyl‐4H‐1,3,2‐benzodioxasiline in a molar ratio of 15:85, medial tensile shear strength values of 12.9 ± 3.9 MPa are achieved in tests according to DIN EN 1465. Electron microscopic and atomic force microscopic investigations give further structural details of the hybrid material. Additionally, the results of nanoindentation and microscratch tests clearly demonstrate that the choice of an adhesion promoter depends on its chemical as well as its mechanical characteristics.

Effect of nano-modified adhesive on interface adhesion properties of steel component reinforced with carbon fibre reinforced polymer

In this paper, nano-Al2O3 particle was added in epoxy adhesive. Its effects on the interface properties of carbon fibre reinforced polymer bonding-reinforcing steel have been investigated. The tensile shear strength values of bonding samples were higher after nano-modification. According to the scanning electron microscope and energy-dispersive spectrum analysis, the pattern and elemental distribution of interface were characterised. Al content has shown to be little increased at the interface, and thus it can enhance the toughness of interface. The results show that the addition of nano-Al2O3 particles in adhesive is conductive to the formation of Si–O–Fe which is a requirement to obtain good adhesion interface.

Friction Stir Lap Joining of Blanks under Different Conditions

The present investigation aims at studying the effect of the tool geometry and of rotational velocity of the tool, at different welding velocities, on the tensile shear strength of the friction stir welded joints realised with blanks of different thicknesses. The proposed trial and error methodology was based on experiments, numerical simulations and microstructure observations.It was observed that, at the lowest rotational velocity, the slender tool determines tensile shear strength values lower than those obtained with the thick tool in particular at the highest welding velocity investigated. The numerical simulation evidenced a wider stirred zone for the thick tool when compared with that realised with the slender tool at the lowest rotational velocity. Microstructure observations evidenced that the increase in the welding velocity determines reduced stirred zones and an homogenisation of material particularly relevant for the slender tool.

Joining of Dissimilar 6063 Aluminium Alloy – 316L Stainless Steel by Spot Welding: Tensile Shear Strength and Heat Treatment

Tensile shear strength and ageing treatment of dissimilar 6063 aluminum alloy-316L stainless steel joint fabricated by spot welding were investigated. The results showed that tensile shear strength increased with the increasing of welding current. The enhancement of tensile shear strength of the joints was due to the enlargement of the nugget diameter. It was also found that the tensile shear strength values for heat treated joint almost similar to that of non-heat treated joint.

Resistance Spot Welding of Advanced High Strength TWIP Steels

In this study, advanced high manganese austenitic steel sheets were welded by resistance spot welding at different welding parameters. The effects of welding current, clamping force, number of the current impulse, and duration of each current impulse were examined. Based on Taguchis method, an L-27(313) orthogonal array was employed for carrying out resistance spot welding tests. The welded sheets were subjected to tensile-shear tests in order to determine the strength of the welded joints. Basically, the results showed that tensile-shear strength increase with clamping force at the medium and high effective welding time (>400 ms). However, the occurrence of micro cracks within the welded joints may justify the scattering of tensile-shear strength values.

Hydroxymethylated resorcinol (HMR) priming agent for improved bondability of wax-treated wood

The effects of hydroxymethylated resorcinol (HMR) on the tensile shear strength of wood joints treated with montan ester wax were studied with polyvinyl acetate (PVAc) and melamine formaldehyde (MF) adhesives. Untreated specimens which were bonded with MF and PVAc had similar bond strength properties under dry conditions, but MF bonded specimens’ tensile shear strength values were higher than that of PVAc glued specimens under wet conditions. With both adhesives tested, dry tensile shear strengths of wax-treated specimens were in a comparable range to those of untreated wood, while under wet conditions the strength values of wax-treated specimens were significantly lower than those of the controls.

Adhesives and coatings based on phenolic/epoxy resins

Low molecular weight epoxy resin based on bis (4-hydroxy phenyl) 1,1 cyclohexane was prepared and modified with various types of the prepared phenolic resins. Phenol–, cresol–, resorcinol–and salicylic acid–formaldehyde resins were used. The optimum conditions of formulation and curing process were studied to obtain modified wood adhesives characterized by high tensile shear strength values. This study indicated that the more suitable conditions are 1:2 weight ratio of phenol–or cresol–formaldehyde to epoxy resin in the presence of phthalic anhydride (20 wt%) of the resin content as a curing agent at 150°C for 80 min. Resorcinol–or salicylic acid–formaldehyde/epoxy resins formulated at 1:2 weight ratio were cured in the presence of paraformaldehyde (20 wt%) at 150°C for 60 min. The effect of the structure of phenolic resins on the tensile shear strength values of formulated resin samples, when mixed with the epoxy resins and cured under the previously mentioned optimum conditions for different times, was investigated. Metallic and glass coatings from the previous resins were also prepared and evaluated as varnishes or paints. Copyright © 1999 John Wiley & Sons, Ltd.

Adhesives and coatings based on poly(vinyl acetal)s

Phenolic resins such as resole phenol– and cresol–formaldehyde, as well as low-molecular-weight epoxy resin based on bis(4-hydroxy phenol) cyclohexane were prepared and modified with various types of the prepared poly(vinyl acetal)s. Poly(vinyl formal), poly(vinyl isobutyral), and poly(vinyl propional) were used. This study indicated that the optimum conditions for curing phenolic or epoxy resin–poly(vinyl acetal)s adhesive compositions are of an equal weight ratio or a 2 : 1 weight ratio in the presence of phthalic anhydride (10 or 20 wt %) of resin content as a curing agent at 150°C for 20 or 60 min, respectively. The effect of acetal type on the tensile shear strength values of resin samples, cured under the previously mentioned optimum conditions for different times, was investigated. The effect of structure of cresol–formaldehyde and epoxy resins was also studied. Metallic and glass coatings from the previous pure resins and their formulated mixtures were also prepared and evaluated as varnishes or paints. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1769–1777, 1998

Adhesives and coatings based on poly(vinyl acetal)s

Phenolic resins such as resole phenol– and cresol–formaldehyde, as well as low-molecular-weight epoxy resin based on bis(4-hydroxy phenol) cyclohexane were prepared and modified with various types of the prepared poly(vinyl acetal)s. Poly(vinyl formal), poly(vinyl isobutyral), and poly(vinyl propional) were used. This study indicated that the optimum conditions for curing phenolic or epoxy resin–poly(vinyl acetal)s adhesive compositions are of an equal weight ratio or a 2 : 1 weight ratio in the presence of phthalic anhydride (10 or 20 wt %) of resin content as a curing agent at 150°C for 20 or 60 min, respectively. The effect of acetal type on the tensile shear strength values of resin samples, cured under the previously mentioned optimum conditions for different times, was investigated. The effect of structure of cresol–formaldehyde and epoxy resins was also studied. Metallic and glass coatings from the previous pure resins and their formulated mixtures were also prepared and evaluated as varnishes or paints. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1769–1777, 1998

Effect of the adhesive strength on the bendability of vibration-damping composite steel sheet.

Effect of adhesion strength on the Bendability was studied in a compositetype vibration-damping steel sheet which consists of two steel skins bonded with a viscoelastic resin. The adhesion strength of the damping sheet was evaluated in tensile shear strength (TSS); TSS values of the damping sheets used for the test were 6, 61, 126 and 148kgf/cm2. U-and 90 deg-bend tests were adopted as bend formability tests.It was found that the bendability of the damping sheet is closely related to their TSS, and it is improved with an increase of TSS. When the TSS is higher than 126kgf/cm2, the bendability of the damping sheet is quite similar to that of conventional steels. On the other hand, when the TSS is as low as 6kgf/cm2, the slip and peel-off between two skins were observed in the bend tests.In the 90 deg-bend test, the damping sheet with TSS of lower than 61 kgf/cm2 bend properties are different from the conventional steel. In large size of bend radius, bend angles of the damping sheet were larger than those of the conventional steel. However, in small size of bend radius, bend angles of the damping sheet were smaller than those of the conventional steel. These behaviors of the damping sheet are based by elastic property of the core resin.