Assembly and Disassembly Mechanics of a Cylindrical Snap Fit

Snap fit is a common mechanical mechanism. It uses the physical asymmetry that is easy to assemble but difficult to disassemble to provide a simple and fast link between objects. The ingenious combination of geometric shape, bending elasticity and friction of the snap fit is the mechanism behind the easy to assemble but difficult to disassemble disassemble. Yoshida and Wada (2020) has done a groundbreaking work in the analysis of the elastic snap fit. During our study of their paper, while we really enjoyed their research, unfortunately we detected several questioning formulations. After careful checking, we found that those formulations are not typographical, therefore it is necessary to make corrections. This paper reformulates the linear elasticity of a cylindrical snap fit, obtains an exact solution and proposes an accurate relation between the opening angle and bending tangent angle. Under the first order approximation, our formulations can reduced to the results of Yoshida and Wada and hence confirms the scientific correctness of Yoshida and Wada's work. Furthermore, this paper also derives a correct vertical displacement expression, and propose a new way of disassembly by bending for the first time and formulate a scaling law by data fitting. All formulations are validated by finite element simulation and experiment. The research here is helpful to the design of elastic snap fit or adjustable mechanical mechanism and metamaterial cell.

Investigation on Rock Strata Fracture Regulation and Rock Burst Prevention in Junde Coal Mine

Through the establishment of structural mechanics model, this paper analyzes the fracture of super thick rock stratum. Through the model, it can be seen that the fracture of low-level super thick rock stratum produces large elastic energy release and dynamic load, which is easy to produce disasters such as rock burst. The numerical calculation shows that under the influence of low hard and thick rock stratum, the leading area of coal mine roadway will produce energy concentration, and the coal pillar will also produce energy accumulation. Thick rock stratum is in bending state and has large bending elasticity. Coal pillar has large compression elasticity, which is the main reason for rock burst. The accumulation of elastic properties of overburden and rock burst caused by coal pillar energy storage can be effectively controlled by using advanced presplitting blasting, coal seam drilling pressure relief, and strengthening support.

Surfactant Monolayer Bending Elasticity in Lipase Containing Bicontinuous Microemulsions

Lipase-catalyzed reactions offer many advantages among which a high degree of selectivity combined with the possibility to convert even non-natural substrates are of particular interest. A major drawback in the applicability of lipases in the conversion of synthetically interesting, non-natural substrates is the substantial insolubility of such substrates in water. The conversion of substrates, natural or non-natural, by lipases generally involves the presence of a water–oil interface. In the present paper, we exploit the fact that the presence of lipases, in particular the lipase from Candida antarctica B (CalB), changes the bending elastic properties of a surfactant monolayer in a bicontinuous microemulsion consisting of D2O/NaCl -n-(d)-octane-pentaethylene glycol monodecyl ether (C10E5) in a similar manner as previously observed for amphiphilic block-copolymers. To determine the bending elastic constant, we have used two approaches, small angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy. The time-averaged structure from SANS showed a slight decrease in bending elasticity, while on nanosecond time scales as probed with NSE, a stiffening has been observed, which was attributed to adsorption/desorption mechanisms of CalB at the surfactant monolayer. The results allow to derive further information on the influence of CalB on the composition and bending elasticity of the surfactant monolayer itself as well as the underlying adsorption/desorption mechanism.

Evaluation of Eucalyptus triantha Timber for Structural Applications

Eucalypt wood is an important raw material with multiple uses applied for furniture, pulp and paper, charcoal, biomass, and construction. Sixteen tests were performed to evaluate physical and mechanical properties of Eucalyptus triantha, which could estimate the possibility of utilization of this woody material in construction. In all, about 267 repeats were realized. Two moisture contents were regarded according to the Brazilian and American standard documents: fiber saturation point (30%) and standard dried point (12%). Results were statistically treated with t-test and demonstrated increases in six mechanical properties from Eucalyptus triantha wood species: rupture moduli in perpendicular and parallel compressions and static bending; elasticity moduli in parallel tensile, perpendicular compression, and static bending. Volumetric mass and bulk densities were practically stable. Physical and mechanical properties estimation evinced that Eucalyptus triantha wood can be used in structural elements.

Fluid deformable surfaces

Lipid membranes are examples of fluid deformable surfaces, which can be viewed as two-dimensional viscous fluids with bending elasticity. With this solid–fluid duality any shape change contributes to tangential flow and vice versa any tangential flow on a curved surface induces shape deformations. This tight coupling between shape and flow makes curvature a natural element of the governing equations. The modelling and numerical tools outlined in Torres-Sánchez et al. (J. Fluid Mech., vol. 872, 2019, pp. 218–271) open a new field of study by enabling the exploration of the role of curvature in this context.

Композиты на основе полистирола с включениями алюмосиликатов различной формы

Samples of composites based on polystyrene with addition of halloysite nanotubes, mica, and montmorillonite aluminosilicates are obtained and the influence of these fillers on viscoelastic, mechanical, and structural properties of composites is studied. It is shown that an addition of up to 5% of mica can increase the rigidity of composites along with maintaining their strength at the level of pure polystyrene and without considerable embrittlement of samples. The addition of halloysite nanotubes and montmorillonite also increases the material stiffness but reduces its strength and elasticity. A significant (up to 50%) increase in the bending elasticity modulus of the composite was achieved by addition of 15% of halloysite nanotubes or 5% of mica.