China
Africa
Explore chapters and articles related to this topic
Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The advantages of adhesive bonding over mechanical fastening include the capacity to bond both alike and dissimilar materials of different thickness, economic and rapid assembly, insulating characteristics, weight reduction, vibration dumping, and uniform stress distribution. On the other hand, examples of the disadvantages of the adhesive bonding are the preparation of surfaces to be connected, long cure times, possible need for heat and pressure for curing, service temperature sensitivity, service deterioration, tendency to creep under prolonged loading, and questionable long-term durability. The upper service temperature of most ordinarily employed adhesives is restricted to about 400°F. However, simpler, cheaper, stronger, and more easy-to-apply adhesives can be expected in the future.
Nanomechanical Properties of Solid Surfaces and Thin Films
Published in Bharat Bhushan, Handbook of Micro/Nano Tribology, 2020
Adhesion describes the sticking together of two materials. Adhesion strength, in a practical sense, is the stress required to remove a coating from a substrate. Indentation and scratch on the micro- and nanoscales are the two commonly used techniques to measure adhesion of thin hard films with good adhesion to the substrate (>70 MPa)(Campbell, 1970; Mittal, 1978; Blau and Lawn, 1986; Bhushan, 1987; Bhushan and Gupta, 1997). Nearly all coatings, by whatever means they are produced, and surface layers of treated parts are found to be in a state of residual (intrinsic or internal) stress. These are elastic stresses that exist in the absence of external forces and are produced through the differential action of plastic flow, thermal contraction, and/or changes in volume created by phase transformation. Microindentation and nanoindentation techniques are also used to measure residual stresses (Bhushan and Gupta, 1997). Microscratch and nanoscratch techniques (using nanoindenter) are also used to measure scratch resistance of surfaces of bulk materials (Bhushan and Gupta, 1995; Bhushan et al., 1996). The nanoindenter has also been modified to conduct microwear studies (Wu and Lee, 1994).
Properties of bulk materials
Published in D.V. Subba Rao, The Belt Conveyor, 2020
Adhesion is the sticking together or adhering of substances in contact with each other. The distinction between adhesion and cohesion is sometimes blurred; cohesion is internal, whereas adhesion is external. When designing systems involving the flow of bulk solids from hoppers or in chutes, or in any situation where a bulk solid slides in contact with a fixed boundary surface, the property of adhesion is important. Adhesion describes the tendency of solid particles to ‘stick’ to a containing surface, such as a wall of a hopper, the side and bottom surfaces of a chute or the surface of a conveyor belt. Kaolin clay is an extreme example for this type of material, which is so tacky that it will stick to a wall when thrown against it. This can create unusual problems in moving this material from storage. Adhesive materials tend to bridge in storage and thus require external assistance.
Material-related and various dependences of adhesion force on piezo velocity revealed on an AFM at moderate humidity
Published in The Journal of Adhesion, 2023
Tianmao Lai, Siyuan Qiu, Runsheng Wang
Experimentally, surface force apparatus (SFA) and atomic force microscope (AFM) are two kinds of widely used apparatuses to measure adhesion forces. An AFM can provide a simple way to experiment by collecting force-displacement curves with a high spatial resolution.[3–5] There is a variety of influencing factors to adhesion forces: contact geometry, surface roughness, surface temperature, hydrophobicity, relative humidity (RH), etc.[6,7] Furthermore, other factors about AFM measurement parameters cannot be ignored: dwell time, piezo velocity, normal load, etc.[8–13] The mechanism of adhesion force can be further understood by investigating the influence of these factors. Moreover, the study can also propose selection recommendations of AFM parameters in measurements.
Evolution of adhesion force behavior at the silica-HOPG interface from humidity-independent to humidity-dependent revealed on an AFM
Published in The Journal of Adhesion, 2023
Tianmao Lai, Yuen Chen, Yuting Zhang
Numerous factors can influence adhesion forces: surface roughness, surface hydrophilicity, tip size and shape, relative humidity (RH), etc..[8] Among them, researchers devote a lot of attention to studying the dependence of adhesion forces on RH. The RH dependence was investigated by using AFM tips on a variety of surfaces: silicon,[9] mica,[10] glass,[11] aluminum oxide,[12] Au film,[13] and so on. Furthermore, some other interfaces with different materials were used to study the RH dependence: cellulose nanocrystals and glass,[14] pollen grains of Hypochaeris radicata and glass,[15] sunflower pollen and aqueous phase droplets,[16] gecko-inspired anisotropic microfibrillar polydimethylsiloxane and glass,[17] gecko-inspired nanopillar arrays and sapphire,[18] gecko beta keratin and space-fixed surface (simulations),[19] granite fragments and silica glass,[20] silica powders and glass,[21] aluminum MEMS microbridges and silicon,[22] graphene and silica,[23,24] and other 2D materials and silicon nitride.[25]
Dealing with Defects and Strengthening Historical Steel Bridges
Published in Structural Engineering International, 2023
Jakub Vůjtěch, Pavel Ryjáček, Jose C. Matos
In comparison with other joining methods, an advantage of adhesive bonding is its good fatigue resistance, high stiffness, easy application, ability to bond dissimilar materials, and also less time consumption with lower costs. Both organic and inorganic adhesives are commercially available at the present time. Most structural applications use a synthetic polymer as a bonding member. The connection is based on adhesive and cohesive force. Cohesion is the bonding force within the polymer. Its properties can be designed and controlled, and the cohesion is designed as the weaker part of the connection. Adhesion ensures that the polymer and the joined members are connected. There are two types of adhesion, mechanical and specific. Mechanical adhesion is the interaction of an irregular surface with the polymer filling the voids.12 Specific adhesion is the attraction between surfaces that are in contact.