scholarly journals Development of a Material Design Space for 4D-Printed Bio-Inspired Hygroscopically Actuated Bilayer Structures with Unequal Effective Layer Widths

Biomimetics ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 58
Author(s):  
Friederike Krüger ◽  
Rebecca Thierer ◽  
Yasaman Tahouni ◽  
Renate Sachse ◽  
Dylan Wood ◽  
...  
Keyword(s):  
Design Space ◽  
Solution Space ◽  
Material Design ◽  
Material Behavior ◽  
Beam Deflection ◽  
Fused Filament Fabrication ◽  
Young’S Moduli ◽  
New Material ◽  
Linear Material ◽  
Production Errors

(1) Significance of geometry for bio-inspired hygroscopically actuated bilayer structures is well studied and can be used to fine-tune curvatures in many existent material systems. We developed a material design space to find new material combinations that takes into account unequal effective widths of the layers, as commonly used in fused filament fabrication, and deflections under self-weight. (2) For this purpose, we adapted Timoshenko’s model for the curvature of bilayer strips and used an established hygromorphic 4D-printed bilayer system to validate its ability to predict curvatures in various experiments. (3) The combination of curvature evaluation with simple, linear beam deflection calculations leads to an analytical solution space to study influences of Young’s moduli, swelling strains and densities on deflection under self-weight and curvature under hygroscopic swelling. It shows that the choice of the ratio of Young’s moduli can be crucial for achieving a solution that is stable against production errors. (4) Under the assumption of linear material behavior, the presented development of a material design space allows selection or design of a suited material combination for application-specific, bio-inspired bilayer systems with unequal layer widths.

scholarly journals Anisotropic and age-dependent elastic material behavior of the human costal cartilage

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Matthias Weber ◽  
Markus Alexander Rothschild ◽  
Anja Niehoff
Keyword(s):  
Costal Cartilage ◽  
Indentation Test ◽  
Biomechanical Properties ◽  
Material Behavior ◽  
Cartilage Tissue ◽  
Elastic Behavior ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Young’S Moduli ◽  
Age Related

AbstractCompared to articular cartilage, the biomechanical properties of costal cartilage have not yet been extensively explored. The research presented addresses this problem by studying for the first time the anisotropic elastic behavior of human costal cartilage. Samples were taken from 12 male and female cadavers and unconfined compression and indentation tests were performed in mediolateral and dorsoventral direction to determine Young’s Moduli EC for compression and Ei5%, Ei10% and Eimax at 5%, 10% and maximum strain for indentation. Furthermore, the crack direction of the unconfined compression samples was determined and histological samples of the cartilage tissue were examined with the picrosirius-polarization staining method. The tests revealed mean Young’s Moduli of EC = 32.9 ± 17.9 MPa (N = 10), Ei5% = 11.1 ± 5.6 MPa (N = 12), Ei10% = 13.3 ± 6.3 MPa (N = 12) and Eimax = 14.6 ± 6.6 MPa (N = 12). We found that the Young’s Moduli in the indentation test are clearly anisotropic with significant higher results in the mediolateral direction (all P = 0.002). In addition, a dependence of the crack direction of the compressed specimens on the load orientation was observed. Those findings were supported by the orientation of the structure of the collagen fibers determined in the histological examination. Also, a significant age-related elastic behavior of human costal cartilage could be shown with the unconfined compression test (P = 0.009) and the indentation test (P = 0.004), but no sex effect could be detected. Those results are helpful in the field of autologous grafts for rhinoplastic surgery and for the refinement of material parameters in Finite Element models e.g., for accident analyses with traumatic impact on the thorax.

Dynamic Response of Dielectric Elastomers

2004 ◽  
Author(s):  
Eric M. Mockensturm ◽  
Nakhiah Goulbourne
Keyword(s):  
Large Deformations ◽  
Electrical Energy ◽  
Material Behavior ◽  
Dielectric Elastomers ◽  
Large Strains ◽  
Inertial Effects ◽  
Stable Equilibria ◽  
Electrostatic Pressure ◽  
Linear Material ◽  
Multiple Stable Equilibria

Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials for many new types of actuators. Unfortunately, their non-linear material behavior and large deformations make actual devices difficult to model. However, the reason for this difficulty can also be used to design actuators that utilize these material and geometric non-linearities to obtain multiple stable equilibria. In this work, we investigate one of the simplest possible configurations, a spherical membrane, using a model that incorporates both mechanical and electrostatic pressure as well as inertial effects that become important when transitioning from one equilibrium to another.

Symmetric Single Rod Cylinders With Variable Piston Area? A Comprehensive Approach to the Right Solution

2018 ◽  
Author(s):  
Giacomo Kolks ◽  
Jürgen Weber
Keyword(s):  
Experimental Validation ◽  
Design Space ◽  
Solution Space ◽  
Hydraulic Cylinder ◽  
Load Cycle ◽  
Displacement Control ◽  
Comprehensive Description ◽  
Subsequent Step ◽  
Variable Displacement ◽  
The Right

In contrast to rotational hydraulic displacement units, such as pumps or motors, conventional hydraulic cylinder actuators do not allow a continuous variation of their displacement quantity: the piston area is regarded constant. In order to adapt to varying load and velocity requirements in a load cycle under torque restrictions of the driving motor, cylinder drives often implement pumps with variable displacement. In this paper, cylinders with discretely variable effective piston area by means of variable circuitry of multi-chamber cylinders are discussed. Hydraulic symmetry or constant asymmetry of the hydraulic cylinder are traits of the cylinder that are required to fit the cylinder to pump structures for closed-circuit displacement control, as given in electro-hydrostatic compact drives (ECD). A methodology to generate all possible solutions of variable area cylinders under the constraint of ECD requirements is proposed. A comprehensive description of the solution space is given, based on combinatorics and solution of equation systems. The methodology dealing with abstract cylinder areas is backed up by a general approach to describe the mechanical cylinder design space to combine multiple cylinder areas in one structural unit. Examples for design of three and four area cylinders are given and results are discussed. The paper concludes with the development of a demonstrator design to allow experimental validation in a subsequent step.

Impact of material concentration and distribution on composite parts manufactured via multi-material jetting

2018 ◽  
Vol 24 (5) ◽  
pp. 872-879 ◽  
Author(s):  
Nicholas Alexander Meisel ◽  
David A. Dillard ◽  
Christopher B. Williams
Keyword(s):  
Material Properties ◽  
Viscoelastic Properties ◽  
Design Space ◽  
Base Material ◽  
Material Design ◽  
Mechanical Analysis ◽  
Material Composition ◽  
Significant Shift ◽  
Content Type ◽  
Property Changes

Purpose Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to macroscale property changes, which must be understood to appropriately design for this additive manufacturing (AM) process. This paper aims to identify impacts on these composites’ viscoelastic properties due to changes in base material composition and distribution caused by incomplete dithering in small features. Design/methodology/approach Dynamic mechanical analysis (DMA) is used to measure viscoelastic properties of two base PolyJet materials and seven “digital materials”. This establishes the material design space enabled by voxel-by-voxel control. Specimens of decreasing width are tested to explore effects of feature width on dithering’s ability to approximate macroscale material properties; observed changes are correlated to multi-material distribution via an analysis of ingoing layers. Findings DMA shows storage and loss moduli of preset composites trending toward the iso-strain boundary as composition changes. An added iso-stress boundary defines the property space achievable with voxel-by-voxel control. Digital materials exhibit statistically significant changes in material properties when specimen width is under 2 mm. A quantified change in same-material droplet groupings in each composite’s voxel pattern shows that dithering requires a certain geometric size to accurately approximate macroscale properties. Originality/value This paper offers the first quantification of viscoelastic properties for digital materials with respect to material composition and identification of the composite design space enabled through voxel-by-voxel control. Additionally, it identifies a significant shift in material properties with respect to feature width due to dithering pattern changes. This establishes critical design for AM guidelines for engineers designing with digital materials.

Microstructure Design for a Rotating Disk: With Application to Turbine Engines

2005 ◽  
Author(s):  
Stephen D. Sintay ◽  
Brent L. Adams
Keyword(s):  
Design Space ◽  
Elastic Anisotropy ◽  
Material Design ◽  
Rotating Disk ◽  
Material Model ◽  
Elastic Stiffness ◽  
Fiber Texture ◽  
Material Parameters ◽  
Extension Force ◽  
Order Of Magnitude

Through the use of generalized spherical harmonic basis functions a spectral representation is used to model the microstructure of cubic materials. This model is then linked to the macroscopic elastic properties of materials with Cubic Triclinic and Cubic Axial-symmetric symmetry. The influence that elastic anisotropy has on the fatigue response of the material is then quantified. This is accomplished through using the effective elastic stiffness tensor in the computation of the crack extension force, G. The resulting material model and macroscopic property calculations are the foundation for a software package which provides an interface to the microstructure. The Microstructure Sensitive Design interface (MDSi) enables interaction with the material design process and provides tools needed to incorporate material parameters with traditional design, optimization, and analysis software. The microstructure of the material can then be optimized concurrently other engineering models to increase the overall design space. The influence of microstructure on the performance of a spinning disc is explored. The additional design space afforded by inclusion of the material parameters show that for both Cubic Triclinic and Cubic Axial-symmetric material symmetry conditions G can be reduced by more than an order of magnitude. For the Cubic Axial-symmetric condition a Cube <001> fiber texture and a <111> fiber texture are identified as the best performing orientation distributions.

scholarly journals Machine Learning-Based Detection of Graphene Defects with Atomic Precision

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Bowen Zheng ◽  
Grace X. Gu
Keyword(s):  
Machine Learning ◽  
Material Design ◽  
Thermal Vibration ◽  
Single Atom ◽  
Complex Data ◽  
Alternative Approach ◽  
Atomic Precision ◽  
Data Driven Approach ◽  
New Material ◽  
Domain Discretization

AbstractDefects in graphene can profoundly impact its extraordinary properties, ultimately influencing the performances of graphene-based nanodevices. Methods to detect defects with atomic resolution in graphene can be technically demanding and involve complex sample preparations. An alternative approach is to observe the thermal vibration properties of the graphene sheet, which reflects defect information but in an implicit fashion. Machine learning, an emerging data-driven approach that offers solutions to learning hidden patterns from complex data, has been extensively applied in material design and discovery problems. In this paper, we propose a machine learning-based approach to detect graphene defects by discovering the hidden correlation between defect locations and thermal vibration features. Two prediction strategies are developed: an atom-based method which constructs data by atom indices, and a domain-based method which constructs data by domain discretization. Results show that while the atom-based method is capable of detecting a single-atom vacancy, the domain-based method can detect an unknown number of multiple vacancies up to atomic precision. Both methods can achieve approximately a 90% prediction accuracy on the reserved data for testing, indicating a promising extrapolation into unseen future graphene configurations. The proposed strategy offers promising solutions for the non-destructive evaluation of nanomaterials and accelerates new material discoveries.

Faster Generation of Feasible Design Points

2005 ◽  
Author(s):  
Bernard Yannou ◽  
Faysal Moreno ◽  
Henri J. Thevenot ◽  
Timothy W. Simpson
Keyword(s):  
Monte Carlo ◽  
Design Space Exploration ◽  
Design Space ◽  
Pareto Frontier ◽  
Solution Space ◽  
Computation Time ◽  
Analytical Form ◽  
Research Field ◽  
Design Under Uncertainty ◽  
Active Research

Design space exploration during conceptual design is an active research field. Most approaches generate a number of feasible design points (complying with the constraints) and apply graphical post-processing to visualize correlations between variables, the Pareto frontier or a preference structure among the design solutions. The generation of feasible design points is often a statistical (Monte Carlo) generation of potential candidates sampled within initial variable domains, followed by a verification of constraint satisfaction, which may become inefficient if the design problem is highly constrained since a majority of candidates that are generated do not belong to the (small) feasible solution space. In this paper, we propose to perform a preliminary analysis with Constraint Programming techniques that are based on interval arithmetic to dramatically prune the solution space before using statistical (Monte Carlo) methods to generate candidates in the design space. This method requires that the constraints are expressed in an analytical form. A case study involving truss design under uncertainty is presented to demonstrate that the computation time for generating a given number of feasible design points is greatly improved using the proposed method. The integration of both techniques provides a flexible mechanism to take successive design refinements into account within a dynamic process of design under uncertainty.

A Variable Fidelity Model Management Framework for Multiscale Computational Design of Continuous Fiber SiC-Si3N4 Ceramic Composites

2007 ◽  
Author(s):  
Gilberto Meji´a Rodri´guez ◽  
John E. Renaud ◽  
Vikas Tomar
Keyword(s):  
Material Design ◽  
Ceramic Composites ◽  
Design Tool ◽  
Material Behavior ◽  
Model Management ◽  
High Fidelity ◽  
Management Framework ◽  
Design Cycle ◽  
Variable Fidelity ◽  
Fidelity Model

Research applications involving design tool development for multiple phase material design are at an early stage of development. The computational requirements of advanced numerical tools for simulating material behavior such as the finite element method (FEM) and the molecular dynamics method (MD) can prohibit direct integration of these tools in a design optimization procedure where multiple iterations are required. The complexity of multiphase material behavior at multiple scales restricts the development of a comprehensive meta-model that can be used to replace the multiscale analysis. One, therefore, requires a design approach that can incorporate multiple simulations (multi-physics) of varying fidelity such as FEM and MD in an iterative model management framework that can significantly reduce design cycle times. In this research a material design tool based on a variable fidelity model management framework is presented. In the variable fidelity material design tool, complex “high fidelity” FEM analyses are performed only to guide the analytic “low-fidelity” model toward the optimal material design. The tool is applied to obtain the optimal distribution of a second phase, consisting of silicon carbide (SiC) fibers, in a silicon-nitride (Si3N4) matrix to obtain continuous fiber SiC-Si3N4 ceramic composites (CFCCs) with optimal fracture toughness. Using the variable fidelity material design tool in application to one test problem, a reduction in design cycle time around 80 percent is achieved as compared to using a conventional design optimization approach that exclusively calls the high fidelity FEM.

scholarly journals The Attitude of Economic Students and Lecturers toward Economic English Material Based on Shariah Economy System

2017 ◽  
Vol 8 (4) ◽  
pp. 697
Author(s):  
Syamsul Una ◽  
Djamiah Husain ◽  
Abd. Halim
Keyword(s):  
Survey Research ◽  
Teaching And Learning ◽  
Positive Attitude ◽  
Material Design ◽  
Learning Material ◽  
New Material ◽  
Academic Year ◽  
Economy System

This research aimed to investigate Economic students and lecturers’ attitude toward economic English material based on shariah economy system. The material was the new material design that combined economic English in general and shariah economy concept in a teaching and learning material. This research is survey research. It was held at Economy Faculty of Dayanu Ikhsanuddin University Baubau Indonesia in 2015/2016 academic year. This research was limited to analyze both Economic students and lecturers’ attitude toward economic English material based on shariah economy system. The Participants of the study were 100 Economic students and 20 Economic lecturers. The instruments used were questionnaire and interview. All participants were invited to respond to questionnaires. And they then participated in follow-up interviews. The results of the study showed that the main score of students’ attitude was 42.24 and lecturers’ attitude was 41.50. From the main above indicated that both Economic students and lecturers had positive attitude toward economic English material based on shariah economy system.

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