Papers by Keyword: Adhesion

Abstract: High-performance thermoplastic polymers paved the way for new fast manufacturing pro-cesses, including welding. In order to obtain optimal bonding of the substrates, an adhesion step isrequired, governed by two main phenomena : intimate contact and healing. While healing has beenvastly explored, theorized and starts to be understood, prediction and characterization of the degree ofintimate contact is still a challenge. After a review of squeeze flow models for intimate contact, alongwith the expressions of the analytical solutions for a Newtonian and a shear-thinning fluid modeled bypower law, a finite element model is presented in order to observe the influence of asperity geometry,fluid behavior, and other assumptions on the evolution of the degree of intimate contact.

Abstract: This research is centered on an environmentally sustainable sol-gel coating, using silica extracted from rice husk ash (RHA), to foster the persistent deterioration of mild steel cause by corrosion for decades despite all efforts put in place by previous researchers. The research focus, was on the extraction of silica from rice hush to synthesize silica-base sol-gel formulation, doped in a graphene oxide to enhanced its efficiency. The formulated sol-gel coating was applied on the mild steel substrates and then characterized by evaluating its corrosion resistance through electrochemical and surface characterization techniques. Such as XRD, FT-IR, SEM, Tafel Polarization and Adhesion Test, which were carried out on the coated samples. Corrosion test was carried out by immersing coated and uncoated samples in 3.5% NaCl solution for seven (7) days and then conducted a Potentiodynamic polarization and Electrical Impedance Spectroscopy (EIS) test to analyze the corrosion rates, impedance and protection efficiency. It was observed that, the highest inhibition efficiency of 85% was achieved at a concentration of 1.0g/200ml after 7 days of exposure which revealed that, coated mild steel possess higher potential corrosion resistant when compared with the conventional anti-corrosion coating in use. Essentially, this research would definitely promote green chemistry by utilizing agricultural waste materials, avoiding uses of toxic precursors and offering an eco-friendly alternative to conventional anti-corrosion coatings.

Abstract: This study investigates the degradation of adhesion between aluminum alloy and epoxy resin under high-temperature and high-humidity conditions. As next-generation power modules increasingly demand enhanced reliability, understanding the factors that affect metal/resin adhesion has become crucial. In this work, fourier transform infrared spectroscopy and adhesion strength testing were employed to evaluate the chemical and mechanical changes occurring at the interface during accelerated aging. FT-IR analysis revealed that the peak intensity of the carbonyl C=O peak in the epoxy resin decreased with aging time, while the aromatic C=C peak remained largely unchanged. The degree of moisture absorption, calculated from the ratio of these peak intensities, increased with the progress of aging. In addition, moisture uptake was found to weaken hydrogen bonding at the A1050/epoxy resin interface, and this effect was more pronounced in specimens with thinner resin layers. Adhesion strength tests showed a significant reduction in adhesive strength with prolonged exposure to high humidity and temperature. Fracture surface observations further indicated a shift in failure mode from cohesive to interfacial with aging. These results suggest that moisture-induced chemical changes at the interface contribute to the degradation of adhesion.

Abstract: Nowadays, the application of protective coatings based on polymer materials is a widespread method of protecting products and parts of water transport from the effects of various environments and is used to increase their service life after repair and restoration work. Application as a base for polymer composite materials based on epoxy resins is considered relevant. To improve the adhesive and mechanical characteristics of polymer composites, their physical and chemical modification was carried out. In particular, it is promising from a practical point of view to introduce into the epoxy resin a microdispersed filler of synthesized aluminum-copper charge (SACC) with a negligible content. It was established that in order to obtain protective coatings or products for increasing the resource of water transport with increased indicators of adhesive and cohesive characteristics, it is necessary to form a composite with the following number of ingredients: epoxy oligomer – 100% by mass; hardener PEPA – 10% by mass; microdisperse filler synthesized aluminum-copper charge – 2 % by mass. The mechanism of activation of interphase interaction during crosslinking of materials due to the formation of chemical bonds between side groups and segments of the epoxy oligomer and active centers on the surface of particles, such as Al+, Cu+, CuAl2 and Al4C3 is substantiated. It is shown that the adhesive-cohesive properties of materials depend mainly on the volume of the boundary surface layers that are formed around the filler particles during the polymerization of composites. The density of such layers differs from the density of the initial ingredients - polymer and filler and is determined by the following criteria: the level of wetting of the dispersed particles with a low-viscosity Newtonian oligomer, their dispersion and specific surface area, the presence of active centers on the surface. A model of the formation of epoxy composites in the presence of a dispersed filler is proposed. The model assumes the gradual formation of boundary surface layers around filler particles. In particular, it is shown the possibility of forming a network structure of a polymer with supramolecular globular inclusions in a polymer system without a filler, as well as successive stages of structure formation of composites in the presence of a filler.

Abstract: In Al-Si alloy roll casting, the thickness of the foil and strip decreases as Si content decreases below 2 mass%, contrary to the expectation that the latent heat decreases as Si content decreases. This phenomenon was investigated experimentally using a melt spinning single roll caster, melt drag single roll caster, and vertical type high-speed twin roll cater. The results demonstrate that the peeling of the solidification layer influences the thickness of the foil and strip. The relationship between casting conditions and adhesion of the solidification layers was also investigated.

Abstract: Currently, functional tests and property tests are used to evaluate cutting fluid [1]. However, the problem is that the results obtained from above tests do not always match with each other because the insert tip is under extreme pressure and high temperature in actual machining. Therefore, a new cutting fluid evaluation method based on actual machining is needed. End face cutting in lathe machining is cutting workpiece from outside to center. In this study, rotation speed was fixed. In other words, cutting speed varies with the radius of workpieces and it is considered possible to clarify the effectiveness of cutting fluid at each cutting speed in a single cut.The performance of the cutting fluid was evaluated based on acceleration of cutting tool and surface roughness of workpiece. The following results were obtained. In steel materials, the acceleration of insoluble cutting oil was highest, and burnt insert tips were observed after the end face cutting. Insoluble cutting oil used in this study has a lower viscosity and a lower boiling point than mineral oils and esters. The highest acceleration of insoluble cutting oil is considered to be due to insufficient lubricating effect because of evaporation of it. No effect of insoluble cutting oil, mineral oils or esters was obtained on surface roughness. The acceleration of undiluted solution is higher than that of diluted solution and burnt insert tips were obtained. The cooling effect of undiluted solution is low because of less water. The highest acceleration of undiluted solutions is considered to be due to insufficient lubricating effect because of evaporation of it. In A5056, surface roughness of the diluted solution was higher at low cutting speed due to lack of lubricating effect. Differences in acceleration, surface roughness and insert tip were observed for each oil type, indicating the possibility of evaluating cutting fluid performance using the method proposed in this study.

Abstract: Many of the previous studies on cutting properties have compared various steels with a same heat treatment, and there are almost no studies that focus on the differences in heat treatments of a same material. In this report, the influence of different heat treatments on tool wear of high-carbon steel (C55) is experimentally investigated in turning process. This study focused on three heat treatments: quenching and tempering, normalizing, and spheroidization annealing. We divided flank wear into 3 areas (corner, middle area and groove wear) for observation and analyzed each characteristic. It is found that for C55, regardless of heat treatment types, wear at the corner of the insert tip is highly dependent on cutting speed, whereas the dependence is lower where it is far away from the corner. This result is considered to be due to the adhesion that occurs while cutting. Therefore, selecting the cutting speed that minimizes flank wear at the corner can control tool wear and extend tool life. In terms of real-time monitoring for tool replacement, the correlation coefficient between the flank wear and the sensing data (spindle current, feed-axis servo motor current, and cutting sound) is also considered to depend on the adhesion condition at the insert tip. If adhesion occurs, the correlation coefficient is not stable and it’s likely to be difficult to predict wear trend to check the end of a tool life. Adhesion makes tool wear prediction using the sensing data difficult.

Abstract: To achieve low on-resistance in any vertical 4H-SiC semiconductor power device, it is essential to create a suitable ohmic contact on the corresponding n-doped SiC substrate. In particular after wafer thinning, a common technology to reduce substrate resistivity, laser annealing for ohmic contact formation on the wafer backside is the only option due to temperature sensitive materials (such as Titanium or Aluminum) on the partially or fully processed wafer frontside. In this work, to solve adhesion issues of the backside metallization, plasma treatments, as easy to integrate process steps, were examined. By stripping obstructive carbon layers, formed after ohmic contact laser annealing, and without damaging the wafer frontside, an enhanced adhesion of following metallization layers was achieved. Both O₂- and H₂-plasma processes were investigated and demonstrated significant improvements to the adhesion of metallization stacks on the wafer backside compared to untreated surfaces and without drawbacks in the ohmic contact quality.

Abstract: A layered clay/epoxy coating was fabricated to investigate the effects of montmorillonite (MMT) and halloysite nanotube (HNT) loading at 0.5, 1.5, and 2.5 parts per hundred resin (phr) on the corrosion resistance and thermal stability of coated mild steel plates. The corrosion study was carried out by Electrochemical Impedance Spectroscopy (EIS) and Tafel polarization. The |Z|_0.1Hz value, R_ct, and R_p of the layered/clay epoxy coatings containing 1.5 phr of HNT and MMT exhibited the best anticorrosion performance compared to other clay content levels. The |Z|_0.1Hz value for the epoxy coating filled with 1.5 phr of MMT (M1.5) is 2.132 × 10⁹ Ω·cm², while it is slightly higher for H1.5 coatings, i.e., 2.629 × 10⁹ Ω·cm². Water absorption trends were consistent with EIS and Tafel polarization studies. The presence of highly compatible nanocontainers clay reduced the total free volume and promoted cross-linking, enhancing anticorrosion performance. Thermal Gravimetry Analysis (TGA) showed that a 1.5 phr loading of MMT in layered/clay epoxy coating demonstrated better thermal stability than a coating embedded with HNT. This improvement can be attributed to the barrier effect of MMT, which retards the diffusion of oxygen molecules into the coating.

Abstract: We present our recent study on adhesive contacts of viscoelastic materials sliding against rigid substrates. Ultimately, the theory addresses the combined effect of viscoelasticity and adhesion in sliding contacts, with specific focus on the sliding frictional behavior. Compared to the adhesiveless case, we show that a significant enhancement of hysteretic friction occurs in the presence of adhesion, in agreement with long-standing experimental evidence. The presented formulation allows to investigate the effect of sliding velocities ranging from extremely slow to very high, thus taking into for local viscoelasticity, occurring at the edges of the contacts (crack tips), and bulk viscoelasticity, occurring in the bulk deformable material.