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Principles of Adhesive Rheology
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
When cracks are created in the adhesives (or at the interface between the adhesive and the adherend), the stresses are normally concentrated at the crack’s tips. The stress concentration is related to the curvature; the smaller the curvature, the larger the stress concentration. However, when the adhesive engages in plastic flow, the local flow will blunt the tip of a preexisting crack and truncate the local stress at the value of the yield strength. Thus, the ability of the adhesives to engage in plastic flow helps prevent debonding.
Mechanical Behavior of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
Superplasticity has a wide range of applications in design and production fields. It can be applied to manufacture the components with smooth edges and contours with a double curvature. It can give us high-dimensional accuracy with exceptional surface finish. It can reduce the lead times and improve productivity. It is widely applied in the industry where vacuum-forming techniques are preferred to produce intricate shapes. The alloys employed for this process are Supral (containing –6Cu–0.5Zr) and IMI 318 (containing –6Al–4V). Superplasticity is still in the developing stage, and there is not much information on it. When deformation of material takes place, grains slide, and this continues until it is met by obstruction. Dislocations and GBs prevent the generation of further dislocations when the strain rates are high, and the dislocations tangle up due to the formation of cell structures when temperature is low; this causes superplasticity to cease.
Computer-Aided Design
Published in Yoseph Bar-Cohen, Advances in Manufacturing and Processing of Materials and Structures, 2018
Nicholaos Bilalis, Emmanuel Maravelakis
The user must be familiar with the basic schemes for curve and surface representation, such as Bézier, B-Splines, and NURBS, and understand their differences and the basic elements defining them, such as control points, curve and surface degree, and the various types of knot vector. Systems handle all curve/surface types in a unified way, but shape control depends on its type. The preferred method for digitizing sketches and drawings and approximating them with curves is through the definition of the control points of the curve (Figure 2.13a); the curve approximates the control points, and first, a rough fitting of the sketch line is aimed and subsequently its fine tuning is achieved by changing the position of the control points. Another method for fitting a curve to a sketch line is through interpolation; a number of points are defined on the sketch line and a B-Spline is generated, which interpolates all points. In both cases, the quality of the final curve is examined and curvature graphs are produced. Curvature is defined for curves and surfaces, and intuitively, it represents the deviation of a curve or surface from being a straight line or a flat surface. In the case of curves, its value is the reciprocal of the radius of the osculating circle (Figure 2.13b). A high curvature value means that small circle radius and the curve bends more sharply, while low curvature value means high radius circle and the curve tends to a straight line. Curvature combs are plotted directly and the quality of the produced curve is examined (Figure 2.13c).
Automated variance modeling for three-dimensional point cloud data via Bayesian neural networks
Published in IISE Transactions, 2023
Zhaohui Geng, Arman Sabbaghi, Bopaya Bidanda
Curvature is a geometric measure that describes how much a curve or surface deviates from a line or a plane, respectively. Variables based on curvature are widely used in computer vision and RE for registration and segmentation, due to their robustness to noise, and translational and rotational invariances (Gauthier et al., 2017). As we only consider discretized points, in this article, “curvature” refers to the curvature of a curve at a point. For illustrative curvatures in 2-D, we note that the curvature of any point on a circle is the reciprocal of its radius, the curvature of a point on a straight line is zero, and the curvature of the intersection point for two lines is infinite. Curvature is not uniquely defined in 3-D because infinitely many curves can pass through a point on a surface. Two commonly used curvature measures in 3-D are the Gaussian and the mean curvatures, defined respectively as and in terms of the maximum and minimum values of all the curvatures as denoted by κ1 and κ2, respectively. Estimations of Gaussian and mean curvatures yield information on a local surface containing the surface change in a small region, but not on an individual point. Therefore, we utilize the rate of the local curvature change νi for each landmark i in our algorithm, where this quantity is defined as in terms of the previously defined eigenvalues.
Wave propagation in a porous functionally graded curved viscoelastic nano-size beam
Published in Waves in Random and Complex Media, 2023
Davood Shahsavari, Behrouz Karami, Abdelouahed Tounsi
As far as applicable continuous structures are concerned, curved beams, because of existing a principal plane with curvature, are commonly used in the design of helicopters, rockets, vessel, ships, and bridges, and also as the stiffeners attachments in designing of thin plates and panels to the aim of increasing the load capacity power. Buckling, vibration, dynamic, and wave propagation of curved composite structures have been investigated in many research studies [54,58–60]. Furthermore, a literature review on the size-dependent mechanical characteristics of curved beams is performed here. Micromechanical modeling vibration analysis of FGM curved microbeam for various homogenization models was performed in Ref. [61] based on first-order shear deformation theory of beams. Based on NSGT in conjunction with the Reddy’s higher-order shear deformation theory of beam, snap-buckling response of P-FGM curved nanobeams surrounded by elastic foundation using perturbation was investigated by She et al. [62]. Navier series were applied to obtain the resonance behavior of curved nanobeam made of P-FGM supporting with simply-supported ends [63]. More recently, size-dependent forced vibration response of P-FGM curved nanobeam utilizing a trigonometric function was examined by Xu et al. [64].
Free vibration analysis of curved metallic and composite beam structures using a novel variable-kinematic DQ method
Published in Mechanics of Advanced Materials and Structures, 2022
Yang Yan, Erasmo Carrera, Alfonso Pagani
Composite materials as an alternative to metallic counterparts have gained much attention owing to their enhanced capability to tailor the structural behavior for specific purposes. In practical engineering applications, these materials are widely used to create laminated structures, such as beams, plates and shells, which are subsequently assembled into primary and secondary components of the aeronautical industry, such as rotor blades of helicopters or stiffeners of wing panels, to name a few [1]. Generally speaking, composite beams are often constructed with a straight or curved axis and a rectangular or thin-walled cross-section. Compared to straight beams, the incorporation of axial curvature increases structural stiffness, together with the complex axial-bending-torsional coupling effect [2]. Accordingly, a refined analysis model is indispensable for a better understanding of mechanical behaviors of curved beams, e.g. vibration behaviors.