1,721,006 research outputs found
Two-way and multiple-way shape memory polymers for soft robotics: An overview
No full textShape memory polymers (SMPs) are smart materials capable of changing their shapes in a predefined manner under a proper applied stimulus and have gained considerable interest in several application fields. Particularly, two-way and multiple-way SMPs offer unique opportunities to realize untethered soft robots with programmable morphology and/or properties, repeatable actuation, and advanced multi-functionalities. This review presents the recent progress of soft robots based on two-way and multiple-way thermo-responsive SMPs. All the building blocks important for the design of such robots, i.e., the base materials, manufacturing processes, working mechanisms, and modeling and simulation tools, are covered. Moreover, examples of real-world applications of soft robots and related actuators, challenges, and future directions are discussed
A convex hull‐based approach for multiaxial high‐cycle fatigue criteria
No full textDesign methods against multiaxial high-cycle fatigue require the formulation of appropriate criteria that differ in the definition of critical measures introduced to quantify damage, as the amplitude of shear stress. The present paper proposes a novel approach to compute the amplitude of shear stress in multiaxial high-cycle fatigue. The approach is based on the computation of the convex hull enclosing the stress history under investigation and is validated on proportional and non-proportional paths in several dimensions and for different materials. High accuracy is achieved when compared with alternative methods from the literature
An efficient algorithm for the solution of min-max problems in multiaxial fatigue
No full textNumerous fatigue criteria require the evaluation of critical quantities to estimate fatigue damage. The approach based on the construction of the minimum circle or hypersphere is often employed in multiaxial high-cycle fatigue criteria to compute critical quantities as the amplitude and mean value of the shear stress. Such a construction can be mathematically formulated as a min-max optimization problem for which efficient numerical strategies are of utmost importance. The present paper proposes a novel algorithm for solving such an optimization problem. The algorithm is based on the alternating direction method of multipliers (ADMM) and is very simple to implement. A wide range of fatigue loading paths, formulated in the two-dimensional and deviatoric spaces, are considered for numerical testing. Comparisons with reference solutions and with two alternative optimization approaches demonstrate the accuracy as well as the high efficiency of the proposed ADMM-based algorithm. A discussion on the adopted stopping criterion and on algorithm parameters is also addressed
Erratum to: Computational Methods for Elastoplasticity: An Overview of Conventional and Less-Conventional Approaches (Archives of Computational Methods in Engineering, (2018), 25, 3, (545-589), 10.1007/s11831-016-9208-x)
No full textThe vendor wrongly numbered the equations in text portions without considering the equations in tables. And ignored and misinterpreted the author corrections. As a result, the referencing in the text to the equations is incorrect
Diagnosi molecolare delle meningo-encefaliti virali :studio relativo a due anni di esperienza
No full textHierarchical motion of 4D-printed structures using the temperature memory effect
No full textThe temperature memory effect (TME) refers to the ability of a shape memory polymer to display recovery around the temperature at which its predeformation occurred so that the material expresses its shape memory response not only in terms of shape but also for what concerns the deformation temperature. This peculiar effect, displayed only by certain classes of polymers, allows to control of the triggering temperature for the shape memory effect as well as to provide multiple shape memory responses for specific, properly designed predeformation histories. Moreover, when combined with 3D printing, such an effect opens new powerful perspectives for designing autonomous structures with customized architectures and programmable/controllable shape changes. However, the design of such structures and of their active response is not trivial and requires careful attention at different levels, i.e., during printing, experimental characterization, modeling, and simulation. The topic of the present chapter concerns 4D-printed structures exhibiting the TME, and it aims at providing the reader with both an analysis and discussion, helpful in guiding toward the design of functional structures capable of controlled motions, also in a hierarchical manner. Particularly, a methodological approach is proposed and includes three main stages: evaluation of material properties, experimental characterization of 3D-printed structures, and modeling/simulation. A discussion about the steps of each stage is provided, together with an overview of the current state of the art, and a case study is presented. Potential application fields and future perspectives are also explored and discussed
Refined shape memory alloys model taking into account martensite reorientation
No full textThe employment of shape memory alloys (SMAs) in a large number of engineering applications has been the motivation for an increasing interest toward a correct and exhaustive modeling of SMA macroscopic behavior. The aim of this paper is the numerical investigation of the theoretical model recently proposed by Auricchio and Bonetti, performed through a more effective and efficient procedure, inspired to that presented for crystal plasticity and consisting in the replacement of the classical set of Kuhn-Tucker conditions by the so-called Fischer-Burmeister complementarity function. Numerical predictions associated with various thermo-mechanical paths are compared to experimental results and the analysis of a boundaryvalue problem is described. Numerical results assess the reliability of the new model and the procedure is verified to be appropriate for the model itself
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