The biaxial weft-knitted (BWK) preform is a unique category of weft-knitted preforms that combines the advantages of non-crimp and knitted architectures. Non-crimp yarns provide in-plane mechanical ...properties, whereas knitted yarns provide damage tolerance, toughness, and formability. They are typically produced on flat knitting machines using interlock or rib gating and the loop transfer technique. This study used experimental and numerical approaches to explore the tensile properties of biaxial single jersey knitted (BSJK)-reinforced composites. BSJK fabric was produced on a computer-controlled flat knitting machine using nylon 6.6 and jute yarns as knitting and straight yarns, respectively. For preparation of the composite samples, polyester resin was injected into the produced knitted fabric by vacuum-assisted resin transfer molding. Tensile tests were conducted on composite samples in the course and wale directions. After the experimental tests, geometric equations were developed for the BSJK fabric. Then, a meso-scale finite element model was proposed using the developed geometric model in the ABAQUS environment. A user-defined material subroutine was prepared to predict the tensile stiffness, as well as the strength. The findings revealed that the produced BSJK-reinforced composite can be tailored to have excellent in-plane tensile characteristics; moreover, the developed geometric equations can adequately predict tensile behavior.
•New geometric vector modelling of SCARA robot.•Definition of independent geometric parameters based on robot joints invariants.•A direct parameters identification method based on “Circle Point ...Analysis”.•Improvement of the accuracy of a SCARA robot (mean transformation error less than 0.03 mm).•Improvement of the final accuracy of a SCARA robot compared to first and second-order Denavit–Hartenberg geometrical model.
This article introduces a new geometric vector modeling method of serial kinematic robot consistent with the identification process. This method is based on the definition of position and orientation of the robot joint invariants. For example, the invariant of the rotational joint is a straight-line (rotational joint axis). Thus, only independent geometrical parameters are introduced to model the joint axis position and orientation in space. Note that, the orientation is not constrained as in the Denavit–Hartenberg (DH) formalism. This article presents the methodology to define these geometrical parameters and the geometrical model. In this context, the identification method relies on "Circle Point Analysis". The points are measured with a laser tracker. Indeed, with a relevant processing of the measured points, we directly identify the invariants of joints. This method is applied to a SCARA robot geometric modeling. After an identification process, this methodology allows improving inverse kinematic error compared to the classical DH geometrical model with first and second-order defects. Moreover, the obtained residual error mean value is close to the accuracy of the measurement process.
Sandwich structures with composite honeycomb core and skin have been mostly used for a variety of engineering applications. There are different man-made honeycomb structures with metal, polymer, and ...paper honeycomb cell geometry which provide minimum weight, least material content and minimal material cost. In this paper, the textile fiber-based 3 D woven honeycomb structure is engineered by using fabric geometrical parameters and mathematical expressions have been developed to calculate the repeat unit weight, fiber volume fraction (FVF) and specific weight of 3 D woven honeycomb structures. Five 3 D woven honeycomb fabric samples with different cell sizes were produced using model-based construction parameters on a customized rapier weaving machine. Fabric dimensional parameters were determined experimentally to validate the model value with actual results. A reasonably high agreement was observed between experimental and theoretical values. The model can be used as a tool to engineer woven honeycomb reinforcement architecture to produce lightweight structural composite materials.
•The damage evolution and crack propagation of asphalt mixture are simulated.•Asphalt mastic in fracture processes is described by the damage constitutive model.•The heterogeneous asphalt mixture ...models are created with a parameterization method.•Effects of pre-crack location and aggregate distribution are evaluated.
A numerical simulation framework is proposed to analyze damage evolution and crack propagation behaviors of heterogeneous asphalt mixture under low temperature. In this framework, asphalt mixture is considered as a two-phase composite consisting of coarse aggregates and asphalt mastic (namely a mix of fine aggregates and asphalt binder). The heterogeneous and random geometrical models of asphalt mixture are created with the parameterization method and the physical degeneration of asphalt mastic in fracture processes is characterized with the damage constitutive model with some experimentally determined parameters. The framework is validated by good agreement between the predictions and the experiments in crack path. Finally, the effects of crack location and coarse aggregate distribution on crack propagation and damage evolution in a pre-cracked three-point bending asphalt mixture beam are evaluated.
A theoretical reflection on smart shape modeling Serón, Francisco J.; Zaldívar, Ángel; Blesa, Alfonso ...
International journal on interactive design and manufacturing,
06/2022, Volume:
16, Issue:
2
Journal Article
Peer reviewed
Open access
This paper presents, as far as the authors are aware, a complete and extended new taxonomy of shape specification modeling techniques and a characterization of shape design systems, all based on the ...relationship of users’ knowledge to the modeling system they use to generate shapes. In-depth knowledge of this relationship is not usually revealed in the regular university training courses such as bachelor’s, master’s and continuing education. For this reason, we believe that it is necessary to modify the learning process, offering a more global vision of all the currently existing techniques and extending training in those related to algorithmic modeling techniques. We consider the latter to be the most powerful current techniques for modeling complex shapes that cannot be modeled with the usual techniques known to date. Therefore, the most complete training should include everything from the usual geometry to textual programming. This would take us a step further along the way to more powerful design environments. The proposed taxonomy could serve as a guideline to help improve the learning process of students and designers in a complex environment with increasingly powerful requirements and tools. The term “smart” is widely used nowadays, e.g. smart phones, smart cars, smart homes, smart cities... and similar terms such as “smart shape modeling”. Nowadays, the term smart is applied from a marketing point of view, whenever an innovation is used to solve a complex problem. This is the case for what is currently called smart shape modeling. However, in the future; this concept should mean a much better design environment than today. The smart future requires better trained and skilled engineers, architects, designers or technical students. This means that they must be prepared to be able to contribute to the creation of new knowledge, to the use of innovations to solve complex problems of form, and to the extraction of the relevant pieces of intelligence from the growing volume of knowledge and technologies accessible today. Our taxonomy is presented from the point of view of methods that are possibly furthest away from what is considered today as “intelligent shape modeling” to the limit of what is achievable today and which the authors call “Generic Shape Algorithm”. Finally, we discuss the characteristics that a shape modeling system must have to be truly “intelligent”: it must be “proactive” in applying innovative ideas to achieve a solution to a complex problem.
In this article, a nonconformal and nonoverlapping domain decomposition method (DDM) based on surface integral equation (SIE) is proposed for the electromagnetic (EM) scattering or radiation of ...multiscale metallic targets. To reduce the unknown amount of the conventional SIE for multiscale EM simulation, we apply curved triangular elements and higher order hierarchical vector (HOHV) basis functions to the SIE. Next, to increase the flexibility of geometrical modeling and accelerate the convergence of the presented SIE system for electrically large and multiscale metallic targets, a DDM scheme is further developed to employ a discontinuous Galerkin (DG) approach to glue conformal/nonconformal surface grids between adjacent subdomains. In addition, an interior penalty term is introduced to stabilize the DDM solution, and half edge-based HOHV basis functions are introduced to model the current associated with nonconformal surface elements. Meanwhile, the basis expansion and recombination (BER) technique is introduced to significantly accelerate the matrix-filling and improve the efficiency. The flexibility of basis order selection is further enhanced by the hierarchical characteristic of HOHV bases. Finally, several numerical results are provided to demonstrate the accuracy, efficiency, and flexibility of the proposed HO-DG-DDM.
In this work, a new structure for designing auxetic yarn and its geometrical analysis is presented. The proposed structure is referred to as a double-core helical auxetic yarn (DC-HAY). It consists ...of two core components of soft yarn with a larger diameter and one wrap component of stiff yarn with a smaller diameter. A primary geometrical model for predicting the Poisson's ratio of the structure was presented through the deformation analysis of the DC-HAY during the tensile loading. Also, the primary proposed model was modified by considering the non-linear behavior of Poisson's ratio of the core components. For the verification of the proposed models, some experiments were conducted based on the initial wrapping angle, as well as the diameter ratio and modulus ratio of components. The results showed that the proposed yarn structure exhibits an apparent auxetic outcome. Moreover, the modified model is capable of predicting the maximum negative Poisson's ratio of the DC-HAY with a desirable error. Furthermore, it was found that the higher modulus ratio of components, higher diameter ratio of components and the lower initial wrapping angle will result in a higher maximum NPR, which were −8.23, −8.16 through the main lateral directions of samples.
This paper proposes an original elasto-geometrical calibration method to improve the static pose accuracy of industrial robots involved in machining, forming or assembly applications. Two approaches ...are presented respectively based on an analytical parametric modeling and a Takagi–Sugeno fuzzy inference system. These are described and then discussed. This allows to list the main drawbacks and advantages of each of them with respect to the task and the user requirements. The fuzzy logic model is used in a model-based compensation scheme to increase significantly the robot static pose accuracy in a context of incremental forming application. Experimental results show the efficiency of the fuzzy logic model while minimizing development and computational resources.
•Robots' pose accuracy improvement with an elasto-geometrical calibration method•Parametric modeling & fuzzy inference system to achieve elastic modeling•Identification of the elasto-geometrical models with experimental data•Discussion about each elastic model, on the task and user requirement topics•Validation of the fuzzy logic elastic model through an experimental forming process
Abstract
Förster resonance energy transfer (FRET) in sensitized fluorescent (SF) organic light‐emitting diodes (OLEDs) is an important process for suppressing triplet exciton loss during energy ...transfer toward the fluorescent dopant. Herein, the contribution of the relative orientation between the sensitizer and emitting dopant to the FRET in state‐of‐the‐art SF OLEDs is explained using experimental and theoretical approaches. The enhanced relative orientation factor (
κ
2
) from 0.375 to 1.250 is theoretically demonstrated in the FRET theory depending on the orientation of the sensitizer and emitting dopant. On comparing two SF OLED systems with different sensitizers, the sensitizer with a higher horizontal dipole orientation exhibits a higher FRET rate, resulting in the enhanced
κ
2
. The exciton dynamics under device operation are explored to quantitatively verify the contribution of the enhanced FRET rate to the exciton transfer processes; the triplet consumption rate of the sensitizer improves by 2.2 times, demonstrating an efficient exciton transfer.
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