Adhesion Problems Research Articles

Effect of laser cleaning of carbon fiber-reinforced polymer and surface modification on chemical activity and bonding strength

Bonding has been used to repair carbon fiber-reinforced polymer (CFRP) materials. However, research has shown that resin residue on the surface of CFRP can cause adhesion problems. Therefore, a reliable surface cleaning procedure is necessary to remove the resin residue before bonding. In this paper, the surface resin was removed by laser cleaning, while the surface properties of CFRP were improved. A pulsed laser cleaning experiment was designed to study the chemical activity and bonding strength of CFRP treated by laser with different laser power and scanning speed. The results showed that as the contact angle of the material surface decreased, chemical activity and adhesive properties were improved. The surface pretreated with laser power of 16 W (scanning speed of 1500 mm/s) had no resin residue and the best adhesive properties; the bonding strength was 1.6 times higher than that of the untreated surface, and the failure mode was dominated by a cohesive damage mode.

Optimization design and experimental analysis of bionic viscosity reduction of chisel type energy saving subsoiling shovel

In order to solve the problems of adhesion to soil and high resistance in traditional subsoiling shovel operation, a bionic energy-saving subsoiling shovel with bionic viscosity reducing and resistance reducing chisel is designed based on the polygon geometry structure of pangolin scales. In this paper, the bionic modeling analysis of chisel type energy-saving subsoiling shovel is carried out by using 3D modeling software. According to the simulation analysis data, we optimize the key structural parameters, and try to produce the bionic energy-saving deep scarifier with reducing viscosity and resistance. In order to study the performance of the chisel type energy-saving subsoiling shovel, L9 (34) orthogonal test was carried out in the field with the number of bionic surfaces, coating materials and forward speed as the experimental factors, and the adhesion soil amount and traction resistance as the test indexes. The results show that the order of influence of each factor on the index is the number of subsoiling shovel bionic surface, coating material and advancing speed; the optimal horizontal combination is that the number of bionic surfaces of subsoiling shovel is 10, the coating material is UHMWPE, and the advancing speed is 6km/h.

Fabrication of antireflection microstructures on the surface of GaSe crystal by single-pulse femtosecond laser ablation.

GaSe crystals are promising as nonlinear optical converters in the mid- and far-IR ranges. However, it is challenging to increase the GaSe surface transmittance of 77% with conventional antireflection coatings because of poor surface quality, leading to coating adhesion problems. Antireflection microstructures (ARMs) offer an alternative way of increasing surface transmittance. In this work, ARMs were fabricated on the surface of a GaSe plate by single-pulse femtosecond laser ablation. An average GaSe surface transmittance of 94% in the 7-11 µm range and a maximum transmittance of 97.8% at 8.5 µm were obtained. The proposed method can be used to increase the efficiency of GaSe-based nonlinear converters.

Biodegradation and Antimicrobial Properties of Zinc Oxide–Polymer Composite Materials for Urinary Stent Applications

Research advancements in the field of urinary stents have mainly been in the selection of materials and coatings to address commonly faced problems of encrustation and bacterial adhesion. In this study, polylactic acid (PLA) and polypropylene (PP) were evaluated with zinc oxide (ZnO) coating to assess its ability to reduce or eliminate the problems of encrustation and bacteria adhesion. PLA and PP films were prepared via twin screw extrusion. ZnO microparticles were prepared using sol-gel hydrothermal synthesis. The as-prepared ZnO microparticles were combined in the form of a functional coating and deposited on both polymer substrates using a doctor blade technique. The ZnO-coated PP and PLA samples as well as their uncoated counterparts were characterized from the physicochemical standpoints, antibacterial and biodegradation properties. The results demonstrated that both the polymers preserved their mechanical and thermal properties after coating with ZnO, which showed a better adhesion on PLA than on PP. Moreover, the ZnO coating successfully enhanced the antibacterial properties with respect to bare PP/PLA substrates. All the samples were investigated after immersion in simulated body fluid and artificial urine. The ZnO layer was completely degraded following 21 days immersion in artificial urine irrespective of the substrate, with encrustations more evident in PP and ZnO-coated PP films than PLA and ZnO-coated PLA films. Overall, the addition of ZnO coating on PLA displayed better adhesion, antibacterial activity and delayed the deposition of encrustations in comparison to PP substrates.

Establishment of Lower Hygroscopicity and Adhesion Strategy for Infrared-Freeze-Dried Blueberries Based on Pretreatments Using CO2 Laser in Combination with Ultrasound

The present study aimed at solving industrial problems of hygroscopicity and adhesion of freeze-dried crisp-texture blueberries without adversely affecting the other properties. CO2-based laser in combination with ultrasound-assisted infusion of soybean protein isolate (SPI) prior to pulse-spouted infrared freeze drying (PSIRFD) was noted to be effective in solving this major problem through the results of dynamic water adsorption analyzer. The main reason why this approach worked was that laser pretreatment reduced the exposure of fruit contents (e.g., sugar, organic acid) outside the epidermis. Also, SPI interacted with the fruit contents to reduce the number of hydrophilic points under the synergistic effect of laser and ultrasound by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis. What is more, the sample prepared by this method possessed the better physicochemical properties and lower energy consumption. So, CO2-based laser in combination with ultrasound along with PSIRFD represents an attractive alternative for producing high-quality dried blueberries.

Design and characterization of plasticized bacterial cellulose/waterborne polyurethane composite with antibacterial function for nasal stenting.

A nasal stent capable of preventing adhesions and inflammation is of great value in treating nasal diseases. In order to solve the problems of tissue adhesion and inflammation response, we prepared plasticized bacterial cellulose (BCG) and waterborne polyurethane (WPU) composite with antibacterial function used as a novel nasal stent. The gelation behavior of BCG could contribute to protecting the paranasal sinus mucosa; meanwhile, the WPU with improved mechanical property was aimed at supporting the narrow nasal cavity. The thickness, size and the supporting force of the nasal stent could be adjusted according to the specific conditions of the nasal. Thermogravimetric analysis, contact angle and water absorption test were applied to investigate the thermal, hydrophilic and water absorption properties of the composite materials. The composite materials loaded with poly(hexamethylene biguanide) hydrochloride maintained well antibacterial activity over 12 days. Animal experiments further revealed that the mucosal epithelium mucosae damage of BCG−WPU composite was minor compared with that of WPU. This new type of drug-loaded nasal stent can effectively address the postoperative adhesions and infections while ensuring the health of nasal mucosal, and thus has an immense clinical application prospects in treating nasal diseases.

The Influence of Reclaimed Asphalt Pavement on the Mechanical Performance of Bituminous Mixtures. An Analysis at the Mortar Scale

The main characteristics of bituminous mixtures manufactured with a considerable amount of reclaimed asphalt pavement (RAP), compared to conventional mixtures, are a reduction in workability, an increase in stiffness, and a loss of ductility, due to the presence of the aged bitumen contained in the RAP particles. To minimize these impacts, softer binders or rejuvenators are commonly used in the design of these mixtures in order to restore part of the ductility lost and to reduce the stiffness. In spite of previous investigations demonstrating that the mortar plays an essential role in the workability, long-term performance, and durability of bituminous mixtures (where cracking, cohesion, and adhesion problems all start at this scale), not many studies have assessed the impacts caused by the presence of RAP. In response to this, the present paper analyzes the workability, fatigue performance, and water sensitivity of bituminous mortars containing different amounts of RAP (from 0% to 100%) and rejuvenators. Mortar specimens were compacted using a gyratory compactor and studied via dynamic mechanical analysis under three point bending configuration. The results demonstrated that the presence of RAP reduces the workability and ductility of asphalt mortars. However, it also causes an increase in their stiffness, which induces a more elastic response and causes an increase in their resistance to fatigue, which could compensate for the loss of ductility. This aspect, together with the low water sensitivity shown, when using Portland cement as an active filler, would make it possible to produce asphalt materials with high RAP contents with a similar long-term mechanical performance as traditional ones. In addition, the use of rejuvenators was demonstrated to effectively correct the negative workability and ductility impacts caused by using RAP, without affecting the fatigue resistance and material adhesion/cohesion.

Deterministic normal contact of rough surfaces with adhesion using a surface integral method.

The fundamental problem of adhesion in the presence of surface roughness and its effect on the prediction of friction has been a hot topic for decades in numerous areas of science and engineering, attracting even more attention in recent years in areas such as geotechnics and tectonics, nanotechnology, high-value manufacturing and biomechanics. In this paper a new model for deterministic calculation of the contact mechanics for rough surfaces in the presence of adhesion is presented. The contact solver is an in-house boundary element method that incorporates fast Fourier transform for numerical efficiency. The adhesive contact model considers full Lennard-Jones potentials and surface integration at the asperity level and is validated against models in the literature. Finally, the effect of surface roughness on the adhesion between surfaces was studied, and it was shown that the root mean square gradient of surface roughness can change the adhesive pressures irrespective of the root mean square surface roughness. We have tested two adhesion parameters based on Johnson's modified criteria and Ciavarella's model. We showed that Civarella's model introduces the most reasonable criteria suggesting that the RMS roughness and large wavelength of surfaces roughness are the important parameters of adhesion between rough surfaces.

Nondrying, Sticky Hydrogels for the Next Generation of High-Resolution Conformable Bioelectronics

This work addresses two well-known problems of tissue-interfacing hydrogels, that is, rapid drying and skin adhesion. These are considered as the main barriers against the wider application of hydr...

Constructing zwitterionic nanofiber film for anti-adhesion of marine corrosive microorganisms

A zwitterionic nanofiber film was constructed through combining zwitterionic polymer with anodic aluminum oxide template for anti-adhering typical marine corrosive microorganisms, i.e. Pseudomonas aeruginosa, Desulfovibrio vulgaris and Chaetoceros muelleri. Results showed that the fabricated zwitterionic polymers film has fibrous nanostructure with uniform distribution and super hydrophilia. This film has wide anti-adhering properties, and it can effectively reduce the attachment of these three microorganisms by more than 99%. Moreover, the adhesion of extracellular polymeric substances secreted from these three microorganisms are also inhibited, which is one reason for the fabricated nanofiber film with anti-adhesion characteristic of microorganisms. This research provides valuable information for solving the problem of microbial adhesion on metal surfaces in the marine environment.

Ant_ViBe: Improved ViBe Algorithm Based on Ant Colony Clustering under Dynamic Background

Foreground target detection algorithm (FTDA) is a fundamental preprocessing step in computer vision and video processing. A universal background subtraction algorithm for video sequences (ViBe) is a fast, simple, efficient and with optimal sample attenuation FTDA based on background modeling. However, the traditional ViBe has three limitations: (1) the noise problem under dynamic background; (2) the ghost problem; and (3) the target adhesion problem. In order to solve the three problems above, ant colony clustering is introduced and Ant_ViBe is proposed in this paper to improve the background modeling mechanism of the traditional ViBe, from the aspects of initial sample modeling, pheromone and ant colony update mechanism, and foreground segmentation criterion. Experimental results show that the Ant_ViBe greatly improved the noise resistance under dynamic background, eased the ghost and targets adhesion problem, and surpassed the typical algorithms and their fusion algorithms in most evaluation indexes.

Assessing the effectiveness of traction gels using full-scale and field testing

Leaf fall during the autumn season creates low adhesion problems on the railways. Traction gels are used to prevent low adhesion, but very little testing has been carried out to assess their performance. Views on their effectiveness vary and their usage is inconsistent across the UK network as a result. This work developed a range of full-scale laboratory and field tests that can be used to assess traction gel performance. The outcomes can lead to increased industry confidence in their ability to mitigate low adhesion, as well as in future product development. It was shown that as a wheel passes over a puddle of traction gel on a rail head, that the gel element is squeezed away leaving the solid particles behind, pick-up on the wheel of particles was also evident. Traction gels were shown to increase traction in full-scale laboratory friction tests in dry and low adhesion conditions. Field brake tests showed that braking was effective in low adhesion and dry conditions with traction gel applied, matching the laboratory test results. The traction gel was also shown to remove a leaf layer, artificially produced by running a DMU over leaf material on a test track. Subsequent work should validate the results on a working railway line during the autumn season.

Investigation on the adhesion improvement of organic coatings on the surface of hot-dip galvanized steel

In order to solve the problem of poor adhesion of organic coatings on the surface of hot-dip galvanizing, we conducted a series of experiments to select the suitable pre-treatment method and type of the coatings. We adopted temperature shock & alternating damp heat combined test and waterproof test to simulate the service conditions, and investigated the adhesion of organic coating on the surface of hot-dip galvanizing in the wet environment. With the XPS analysis, we discussed the avoidance of formation of weak boundary layer on the hot-dip galvanizing surface by pre-treatment, and the improvement on adhesion of the organic coatings. We also proposed the pre-treatment method of coupling treatment with silane or combined alkali washing & grinding procedures, by which the organic coating on the hot-dip galvanizing surface performed excellent adhesion and water proof ability against wet conditions.

Characterization of silicon acrylic resin containing silica nanoparticles as candidate materials for antifouling and anticorrosion properties in seawater

Abstract The damage caused by marine fouling organisms to ships and underwater artificial equipment is becoming increasingly serious issue, and the prevention and control of marine biofouling has always been a research hotspot in marine coatings. Aiming at the problems of poor adhesion, long curing time and high curing temperature of low-surface energy marine antifouling coatings of organosilicon, a hydrophobic low-surface energy nano-SiO2/silicon acrylic resin nanocomposite coating was synthesized. The anticorrosive property of the composite coatings was analyzed by simulated seawater periodic immersion experiments. The gel permeation chromatography analysis showed that polydimethyl-siloxanes (PDMS) is involved in cross-linking reactions. The dynamic thermomechanical analysis indicated that the glass transition temperature of resin is 58 °C. The contact angle (CA) test showed that the CA of nanocomposite coating is 109.99°. All the detection results can support the excellent antifouling and anticorrosion performance of the low surface energy nanocomposite coatings.

Functional Coatings for Orthodontic Archwires-A Review.

In this literature review, the current state-of-art of coatings for orthodontic archwires’ increasing antimicrobial and relevant mechanical properties, such as surface topography, friction or corrosion resistance, has been presented. There is a growing request for orthodontic appliances, therefore, most researchers focus on innovative functional coatings to cover orthodontic archwires and brackets. Orthodontic appliances are exposed to the unfavorable oral cavity environment, consisting of saliva flow, food, temperature and appliance force. As a consequence, friction or biocorrosion processes may occur. This can affect the functionality of the orthodontic elements, causing changes in their microstructure, surface topography and mechanical properties. Furthermore, the material which the orthodontic archwire is made from is of particular importance in terms of the possible corrosion resistance. This is especially important for patients who are hypersensitive to metals, for example, nickel, which causes allergic reactions. In the literature, there are some studies, carried out in vitro and in vivo, mostly examining the antibacterial, antiadherent, mechanical and roughness properties of functional coatings. They are clinically acceptable but still some properties have to be studied and be developed for better results. In this paper the influence of additives such as nanoparticles of silver and nitrogen-doped TiO2 applied on orthodontic brackets by different methods on the antimicrobial properties was analyzed. Future improvement of coating techniques as well as modification of the archwire composition can reduce the release of nickel ions and eliminate friction and bacterial adhesion problems, thus accelerating treatment time.

The low adhesion problem: The effect of environmental conditions on adhesion in rolling-sliding contact

Low adhesion problem is one of the major problems for railways all over the world because this phenomenon can occur anytime and anywhere. To investigate when poor adhesion conditions can be expected in real operation, a ball-on-disc tribometer with a climate chamber was employed to simulate rolling-sliding contact under various environmental conditions. Clean and contaminated discs with leaf extract were used to simulate different surface conditions. Results indicate that contact operating under rolling-sliding conditions is more prone to the occurrence of low adhesion than found by others for pure sliding contact. Very low adhesion (≤0.05) were identified for contaminated and oxidized specimens operating under humid and wet conditions. For clean surfaces, low adhesion (≤0.15) were found under dew conditions.

Effect of Scale and Sequence of Surface Textures on the Anti-adhesive Wear Performance of PVD Coated Tool in Dry Machining SLM-Produced Stainless Steel

During the dry post-machining processing of selective laser melting (SLM)-produced stainless steel with TiAlN coated tool, the elements of stainless steel chips can diffuse and adhere into the coated tool surface, causing serious adhesive wear. In this study, to inhibit the adhesion problem at the tool-chip interface, surface textures with different scales (micro-, nano- and micro/nano-textures) are produced on tool rake face by laser processing before and after physical vapor deposition (PVD) TiAlN coatings deposition. To investigate the cutting performance of these developed coated tools, dry machining tests of the SLM-produced stainless steel are carried out. And, the mechanical properties of textured TiAlN coatings such as the hardness, elastic modulus and critical load are also studied to explain the results from the machining tests. It can be found that the anti-adhesive wear performance of TiAlN coated tool is improved by laser surface texturing. The texture dimension significantly affects the mechanical properties and dry cutting performance of the TiAlN coated tool, and the micro/nano-textures are found to be optimum. Meanwhile, the sequence of surface textures also has an effect on the wear performance of the developed TiAlN coated tools. In the experiment, laser surface texturing before coatings is effective in acting as a barrier against flaking of the TiAlN film, providing a higher active surface for the subsequent TiAlN coatings and presenting a higher compressive residual stress. Thus, the developed cutting tool which is textured before TiAlN coatings deposition presents a milder wear compared to the developed one which is textured after TiAlN coatings deposition.

Exact solutions of some singular integro-differential equations related to adhesive contact problems of elasticity theory

The problem of constructing an exact solution of singular integro-differential equations related to problems of adhesive interaction between elastic thin semi-infinite homogeneous patch and elastic plate is investigated. For the patch loaded with horizontal forces the usual model of the uniaxial stress state is valid. Using the methods of the theory of analytic functions and integral transformation, the singular integro-differential equation is reduced to the Riemann boundary value problem of the theory of analytic functions. The exact solution of this problem and asymptotic estimates of tangential contact stresses are obtained.

Numerical analysis and simulation of an adhesive contact problem with damage and long memory

<p style='text-indent:20px;'>This paper studies an adhesive contact model which also takes into account the damage and long memory term. The deformable body is composed of a viscoelastic material and the process is taken as quasistatic. The damage of the material caused by the compression or the tension is involved in the constitutive law and the damage function is modelled through a nonlinear parabolic inclusion. Meanwhile, the adhesion process is modelled by a bonding field on the contact surface while the contact is described by a nonmonotone normal compliance condition. The variational formulation of the model is governed by a coupled system which consists of a history-dependent hemivariational inequality for the displacement field, a nonlinear parabolic variational inequality for the damage field and an ordinary differential equation for the adhesion field. We first consider a fully discrete scheme of this system and then focus on deriving error estimates for numerical solutions. Under appropriate solution regularity assumptions, an optimal order error estimate is derived. At the end of this paper, {we report some two-dimensional numerical simulation results} for the contact problem in order to provide numerical evidence of the theoretical results.

Numerical Analysis of an Adhesive Contact Problem with Long Memory

Numerical Analysis of an Adhesive Contact Problem with Long Memory