scholarly journals 4D Printing Pre-Strained Structures for Fast Thermal Actuation

2021 ◽  
Vol 8 ◽  
Author(s):  
Yu Zou ◽  
Zhongyi Huang ◽  
Xiying Li ◽  
Pengyu Lv
Keyword(s):  
Bilayer Structure ◽  
4D Printing ◽  
Element Analysis ◽  
Strained Layer ◽  
Thermal Actuation ◽  
The Finite Element Analysis ◽  
3D Printed ◽  
Shape Property ◽  
External Stimuli

Four-dimensional (4D) printing is an emerging technology by adding the dimension of time-dependent reconfiguration into 3D printing. It enables the 3D printed structure to change the shape, property, or functionality under external stimuli such as temperature, magnetic field, and light, etc. Among the existing 4D printed structures, thermal responsive structures are widely used for their easy operation. However, the slow actuation of the thermal responsive structures impedes the applications like soft robotics. In the current work, a pre-strained strategy is proposed to accelerate the actuation of thermal responsive structures. A 4D printing platform that can apply strain during the printing process is constructed to fabricate the pre-strained structures under the aid of in-situ tensile of the printing base. A bilayer structure with one pre-strained layer and the other non-pre-strained layer is integrally printed. Through experiments and the finite element analysis, it is demonstrated that the aspect ratio has little effect on the deformation of the bilayer structure, whereas the pre-strain plays a key role in the deformation and also greatly accelerates the actuation of the bilayer structure. Based on the 4D printed pre-strained bilayer structure, an energy-free gripper is fabricated and a fully soft crawler is printed to achieve a high running speed.

scholarly journals 4D Printing: A Review on Recent Progresses

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 796 ◽  
Author(s):  
Honghui Chu ◽  
Wenguang Yang ◽  
Lujing Sun ◽  
Shuxiang Cai ◽  
Rendi Yang ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
3D Printing ◽  
Three Dimensional ◽  
Complex Structures ◽  
Future Prospects ◽  
4D Printing ◽  
Stimulation Method ◽  
Shape Property ◽  
External Stimuli

Since the late 1980s, additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has been gradually popularized. However, the microstructures fabricated using 3D printing is static. To overcome this challenge, four-dimensional (4D) printing which defined as fabricating a complex spontaneous structure that changes with time respond in an intended manner to external stimuli. 4D printing originates in 3D printing, but beyond 3D printing. Although 4D printing is mainly based on 3D printing and become an branch of additive manufacturing, the fabricated objects are no longer static and can be transformed into complex structures by changing the size, shape, property and functionality under external stimuli, which makes 3D printing alive. Herein, recent major progresses in 4D printing are reviewed, including AM technologies for 4D printing, stimulation method, materials and applications. In addition, the current challenges and future prospects of 4D printing were highlighted.

Modeling and Simulation of Hydraulic Fracturing Propagation in Permeable Reservoirs

2006 ◽  
Vol 324-325 ◽  
pp. 383-386 ◽  
Author(s):  
Zhi Long Lian ◽  
Xiu Xi Wang ◽  
Heng An Wu ◽  
Bing Xue ◽  
J. Zhang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Analysis Software ◽  
Element Analysis ◽  
Fracture Geometry ◽  
Stress Equilibrium ◽  
Continuity Equations ◽  
The Finite Element Analysis

Numerical simulation of hydraulic fracturing propagations in the permeable reservoirs was carried out with the finite element analysis software (ABAQUS). A model of coupling the stress equilibrium and fluid continuity equations was proposed and implemented. The nonuniform of sink pore pressure on the fracture surfaces which changes associated with the propagation of fracture was described by a self-developed subroutine through the FLOW in ABAQUS. Samples under different conditions were conducted for studying the rules of the propagation of hydraulic fracturing. The results show that the permeability at the fracture tip is more serious than any other places of the fracture face. The model also illustrates that the fracture geometry is mainly determined by the minimal in-situ stress. The model can be used to simulate the effects of hydraulic fracturing pressures and injection rates on fracture propagation. The results are of much significance for the design of hydraulic fracturing treatments.

scholarly journals 4D Printing of Origami Structures for Minimally Invasive Surgeries Using Functional Scaffold

2020 ◽  
Vol 11 (1) ◽  
pp. 332
Author(s):  
Thomas Langford ◽  
Abdullah Mohammed ◽  
Khamis Essa ◽  
Amr Elshaer ◽  
Hany Hassanin
Keyword(s):  
Minimally Invasive ◽  
Smart Materials ◽  
Biomedical Applications ◽  
Shape Recovery ◽  
Short Communication ◽  
Proof Of Concept ◽  
4D Printing ◽  
Significant Discovery ◽  
External Stimuli

Origami structures have attracted attention in biomedical applications due to their ability to develop surgical tools that can be expanded from a minimal volume to a larger and functional device. On the other hand, four-dimensional (4D) printing is an emerging technology, which involves 3D printing of smart materials that can respond to external stimuli such as heat. This short communication introduces the proof of concept of merging origami and 4D printing technologies to develop minimally invasive delivery of functional biomedical scaffolds with high shape recovery. The shape-memory effect (SME) of the PLA filament and the origami designs were also assessed in terms of deformability and recovery rate. The results showed that herringbone tessellation origami structure combined with internal natural cancellous bone core satisfies the design requirement of foldable scaffolds. The substantial and consistent SME of the 4D printed herringbone tessellation origami, which exhibited 96% recovery compared to 61% for PLA filament, was the most significant discovery of this paper. The experiments demonstrated how the use of 4D printing in situ with origami structures could achieve reliable and repeatable results, therefore conclusively proving how 4D printing of origami structures can be applied to biomedical scaffolds.

scholarly journals Design and Analysis of 3D Printable Foot Prosthesis

2017 ◽  
Vol 61 (4) ◽  
pp. 282 ◽  
Author(s):  
Bence Rochlitz ◽  
Dávid Pammer
Keyword(s):  
Mechanical Properties ◽  
Medical Devices ◽  
Low Cost ◽  
Element Analysis ◽  
Cyclic Compression ◽  
Deposit Modeling ◽  
The Finite Element Analysis ◽  
3D Printed ◽  
Transtibial Amputees ◽  
Low Activity

3D printing manufacturing process has the possibilities to produce individual medical devices, especially implants and prosthesis with short production time. The aim of this study is to design a 3D printable Energy Storage and Return (ESAR) foot prosthesis for transtibial amputees with a novel geometry. The criteria of the prosthesis were 3D printable, low cost, simply geometry and satisfying mechanical properties for low activity use. The finite element analysis of the designed foot prosthesis was conducted in each of the three support phases of the walking cycle (controlled plantarflexion, controlled dorsiflexion, powered plantarflexion or push-off phase). Besides of the simulations the prototype was printed by fused deposit modeling (FDM) technology, used ABS material and the produced prototype was investigated in quasi-static and cyclic compression. It can be stated after the investigation (simulation and test) that the 3D printed prototype fulfill the requirements and it can be used as passive ESAR foot prosthesis.

Evaluation of Pipeline Stresses During Line Lowering

2008 ◽  
Author(s):  
Millan Sen ◽  
Joe Zhou
Keyword(s):  
Finite Element Analysis ◽  
Loading Condition ◽  
Analysis Program ◽  
Element Analysis ◽  
Environmental Loads ◽  
Right Of Way ◽  
The Finite Element Analysis ◽  
The Right ◽  
Maximum Stresses

The stresses induced to a pipe during line lowering are the maximum stresses that the pipeline will experience during its lifetime, in regions where there are no excessive environmental loads. During the installation of the TransCanada pipeline at Stittsville, Ontario, it was critical to limit the pipeline stresses that occurred during line lowering. This was required in order to fulfill the requirements of ECA-based flaw acceptance criteria applicable to mainline welding. However, the construction of the pipeline involved numerous challenges with regards to moving equipment during the pipeline installation, regions of deep cover requirements, and spatial restrictions on the right of way. These conditions introduced complicated loading scenarios, which made it difficult to ascertain the resulting stresses that the line lowering would apply to the pipeline. These stresses were evaluated herein using the finite element analysis program PIPLIN, with consideration of the actual in-situ installation conditions. Each loading condition was modeled individually, and the forces in the sidebooms were considered in addition to the pipeline stresses. It was determined that all the stresses in the pipeline during the line lowering were acceptable, so long as the specified boom locations remained within limits.

scholarly journals Post-flambage unilatéral des films minces sur substrat

2007 ◽  
pp. 941-955
Author(s):  
Guillaume Parry ◽  
Jérôme Colin ◽  
Christophe Coupeau ◽  
Alain Cimetière
Keyword(s):  
Biaxial Stress ◽  
Element Analysis ◽  
Compression Device ◽  
Critical Transitions ◽  
Atomic Force ◽  
Biaxial Stress State ◽  
The Finite Element Analysis ◽  
Rectangular Strip ◽  
Post Buckling

Various buckling equilibria can be observed on the delaminated areas of thin films. These equilibria are usually under advanced post-buckling. Results of the finite element analysis for the post-buckling equilibria of a thin film delaminated along a rectangular strip are discussed in this paper. Those results are compared with experimental observations performed with the help of an in-situ atomic force microscope coupled to a compression device which allows to vary the biaxial stress state in the film. The transitions from straightsided blisters to bubbles or telephone cord blisters are characterized. Both sub-critical and super-critical transitions are highlighted. A mapping of the various stable post-critical equilibria is given.

scholarly journals Modified design and use of a high-pressure environmental stage for laboratory X-ray powder diffractometers

2008 ◽  
Vol 41 (2) ◽  
pp. 350-355 ◽  
Author(s):  
Pamela S. Whitfield ◽  
A. Victoria Nawaby ◽  
Brian Blak ◽  
James Ross
Keyword(s):  
Variable Temperature ◽  
Materials Processing ◽  
Design Code ◽  
Element Analysis ◽  
Data Set ◽  
Time Resolved ◽  
X Ray ◽  
The Finite Element Analysis ◽  
American Society

The popularity of supercritical CO2for materials processing makes thein situstudy of pressures up to 10 MPa in the laboratory particularly interesting. This paper describes a modified design for a 12.4 MPa (1800 psi) variable-temperature pressure vessel based on an existing cell reported by Koster van Groos, Guggenheim & Cornell [Rev. Sci. Instrum.(2003),74, 273–275]. The modifications satisfied the demands of the American Society of Mechanical Engineers design code 31.3, leading to legal design registration, construction and subsequent hydrostatic test. The thinner windows that the finite element analysis indicated as sufficient allow for rapid data collection, even using a laboratory-based Mo source. This type of application is demonstrated with a time-resolved data set showing the crystallization of a polylactic acid–clay nanocomposite under 6.8 MPa CO2.

Critical Thickness for Strained Quantum Wires

1995 ◽  
Vol 379 ◽  
Author(s):  
T. J. Gosling ◽  
L. B. Freund
Keyword(s):  
Finite Element ◽  
Critical Thickness ◽  
Quantum Wires ◽  
Lattice Mismatch ◽  
Threading Dislocations ◽  
Element Analysis ◽  
Strained Layers ◽  
Strained Layer ◽  
The Finite Element Analysis ◽  
The Stability

ABSTRACTThe stability of strained quantum wires against the propagation of threading dislocations is considered, using a critical thickness criterion due to Matthews and Blakeslee that is extensively used for strained layers. Given first are results for the critical mismatch at which a buried wire of a given thickness becomes susceptible to degradation. It is found that a wire, once buried, is extremely stable, being able to support, without loss of coherency, around five times the lattice mismatch that can be supported by a buried strained layer of the same thickness. It is concluded that if a strained wire contains dislocations then those dislocations must have been introduced during its growth, when the top surface of the wire is exposed. To investigate this, the results of finite element calculations are presented that give the critical relationship between mismatch and thickness during the growth of a triangular quantum wire being deposited in a [110]-oriented V-groove in a patterned (001) substrate. The results may be approximately expressed through an expression of the same form as that derived by Matthews and Blakeslee for a strained layer, but with modified coefficients obtained via the finite element analysis. Contact is made with the limited experimental evidence available.

In situ TEM measurements of the electrical properties of interface dislocations

1992 ◽  
Vol 50 (2) ◽  
pp. 1338-1339
Author(s):  
F. M. Ross ◽  
R. Hull ◽  
D. Bahnck ◽  
J. C. Bean ◽  
L. J. Peticolas ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Electronic Device ◽  
In Situ Tem ◽  
Device Performance ◽  
Misfit Dislocations ◽  
Electrical Characteristics ◽  
Strained Layer ◽  
Transmission Electron ◽  
Interfacial Dislocations

We describe an investigation of the electrical properties of interfacial dislocations in strained layer heterostructures. We have been measuring both the structural and electrical characteristics of strained layer p-n junction diodes simultaneously in a transmission electron microscope, enabling us to correlate changes in the electrical characteristics of a device with the formation of dislocations.The presence of dislocations within an electronic device is known to degrade the device performance. This degradation is of increasing significance in the design and processing of novel strained layer devices which may require layer thicknesses above the critical thickness (hc), where it is energetically favourable for the layers to relax by the formation of misfit dislocations at the strained interfaces. In order to quantify how device performance is affected when relaxation occurs we have therefore been investigating the electrical properties of dislocations at the p-n junction in Si/GeSi diodes.

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