scholarly journals Design and Testing of Bistable Lattices with Tensegrity Architecture and Nanoscale Features Fabricated by Multiphoton Lithography

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 652 ◽  
Author(s):  
Zacharias Vangelatos ◽  
Andrea Micheletti ◽  
Costas P. Grigoropoulos ◽  
Fernando Fraternali
Keyword(s):  
Dynamic Responses ◽  
Repeated Loading ◽  
Stable Configuration ◽  
Compression Tests ◽  
Modular Lattices ◽  
Softening Behavior ◽  
Multiphoton Lithography ◽  
Nanoscale Features ◽  
Force Displacement ◽  
Design And Testing

A bistable response is an innate feature of tensegrity metamaterials, which is a conundrum to attain in other metamaterials, since it ushers unconventional static and dynamical mechanical behaviors. This paper investigates the design, modeling, fabrication and testing of bistable lattices with tensegrity architecture and nanoscale features. First, a method to design bistable lattices tessellating tensegrity units is formulated. The additive manufacturing of these structures is performed through multiphoton lithography, which enables the fabrication of microscale structures with nanoscale features and extremely high resolution. Different modular lattices, comprised of struts with 250 nm minimum radius, are tested under loading-unloading uniaxial compression nanoindentation tests. The compression tests confirmed the activation of the designed bistable twisting mechanism in the examined lattices, combined with a moderate viscoelastic response. The force-displacement plots of the 3D assemblies of bistable tensegrity prisms reveal a softening behavior during the loading from the primary stable configuration and a subsequent snapping event that drives the structure into a secondary stable configuration. The twisting mechanism that characterizes such a transition is preserved after unloading and during repeated loading-unloading cycles. The results of the present study elucidate that fabrication of multistable tensegrity lattices is highly feasible via multiphoton lithography and promulgates the fabrication of multi-cell tensegrity metamaterials with unprecedented static and dynamic responses.

Experimental and Numerical Investigation of Texture Development during Hot Rolling of Magnesium Alloy AZ31

2007 ◽  
Vol 539-543 ◽  
pp. 3448-3453 ◽  
Author(s):  
C. Schmidt ◽  
Rudolf Kawalla ◽  
Tom Walde ◽  
Hermann Riedel ◽  
A. Prakash ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Hot Rolling ◽  
Rolling Texture ◽  
Rolling Process ◽  
Model Parameters ◽  
Compression Tests ◽  
Basal Texture ◽  
Alloy Az31 ◽  
Magnesium Alloy Az31 ◽  
Softening Behavior

Due to the deformation mechanisms and the typical basal texture rolled magnesium sheets show a significant asymmetry of flow stress in tension and compression. In order to avoid this undesired behavior it is necessary to achieve non-basal texture during rolling, or at least, to reduce the intensity of the basal texture component. The reduction of the anisotropy caused by the basal texture is very important for subsequent forming processes. This project aims at optimizing the hot rolling process with special consideration of texture effects. The development of the model is carried out in close cooperation with the experimental work on magnesium alloy AZ31 .The experimental results are required for the determination of model parameters and for the verification of the model. Deformation-induced texture is described by the visco-plastic self-consistent (VPSC) model of Lebensohn and Tomé. The combination of deformation and recrystallization texture models is applied to hot compression tests on AZ31, and it is found, that the model describes the observed texture and hardening/softening behavior well. In some cases rotation recrystallization occurs in AZ31 which appears to be a possibility to reduce the undesired basal rolling texture.

scholarly journals Particle Compression Test: A Key Step towards Tailoring of Feedstock Powder for Cold Spraying

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 458 ◽  
Author(s):  
Hamid Assadi ◽  
Frank Gärtner
Keyword(s):  
Cold Spray ◽  
Cold Spraying ◽  
Compression Tests ◽  
Feedstock Powder ◽  
Design And Manufacturing ◽  
Present Case Study ◽  
Force Displacement ◽  
Subsequent Comparison ◽  
The Ideal

Cold spray is on the way to becoming a mainstream technology for coating and additive manufacturing processes. While there have been many advances in various aspects of this technology, the question of tailoring the ‘ideal’ feedstock powder for cold spraying has remained open. In particular, the mechanical strength and its dependence on the particle size, which are amongst the most relevant properties of the feedstock powder for cold spraying, are rarely covered when reporting powder specifications. This is mainly because of the lack of standardised methods of characterisation for these specific properties. In the present case study, we demonstrate how compression tests of single Inconel 718 particles by using a modified nanoindenter can address this central question. Data analyses are supported by finite element modelling of particle compression for a range of plastic behaviours. The results of simulation are then stored in the form of a surrogate model for subsequent comparison with the experimental data. Thus, the ultimate tensile strength and the size of the examined particles are calculated directly from the measured force-displacement data. The paper will also discuss how this information can be used to optimise cold spraying, and so, unveils a key step towards the design and manufacturing of cold-spray-specific feedstock powder.

Quantitative Analysis of Dynamic Softening Behaviors Induced by Dynamic Recrystallization for Ti-10V-2Fe-2Al Alloy

2015 ◽  
Vol 34 (6) ◽  
Author(s):  
Guozheng Quan ◽  
Shiao Pu ◽  
Hairong Wen ◽  
Zhenyu Zou ◽  
Jie Zhou
Keyword(s):  
Titanium Alloy ◽  
Quantitative Analysis ◽  
Dynamic Recrystallization ◽  
Hot Compression ◽  
Laboratory Scale ◽  
Compression Tests ◽  
Temperature Range ◽  
Height Reduction ◽  
Softening Behavior ◽  
Dynamic Softening

AbstractIn order to investigate the effect of dynamic recrystallization (DRX) behavior on dynamic softening behavior of wrought Ti-10V-2Fe-3Al titanium alloy, a series of laboratory scale isothermal hot compression tests with a height reduction of 60% were performed in a temperature range of 948 K~1023 K in the (

scholarly journals Numerical Simulations of Clay Tiles Compression

2012 ◽  
Vol 504-506 ◽  
pp. 1403-1408 ◽  
Author(s):  
Jérémie Vignes ◽  
Fabrice Schmidt ◽  
Gilles Dusserre ◽  
Olivier de Almeida ◽  
Jean Frédéric Dalmasso
Keyword(s):  
Numerical Model ◽  
Tensile Stress ◽  
Numerical Simulations ◽  
Compression Tests ◽  
Rheological Study ◽  
Constitutive Parameters ◽  
Actual Geometry ◽  
Clay Tiles ◽  
Force Displacement ◽  
Tribological Parameters

During the pressing step, the clay tiles undergo stresses which result in the appearance of defects. A rheological study, based on free compression tests, allowed to confirm the Elasto-visco-plastic behaviour of the clay. The different constitutive parameters were estimated by fitting the force-displacement experimental curves using the optimisation algorithm (ES Metamodel) implanted in the commercial software Forge 2009®. The influence of the tribological parameters was studied using squeezing numerical simulations of a full tile. The numerical model was validated with experimental squeezing test of technological specimen with a tile lug. Then, we have compared experimental force with the numerical one and deduced that the clay/tool interface is not perfectly sliding. A friction Tresca’s law was used to model the clay/tool interface. Numerical results showed that the actual geometry of tile lug didn’t allow to form correctly the tile. Several areas undergo tensile stress, air traps ,... A new geometry of tile lug was proposed in order to limit this phenomenon. Using a simplified defect criteria (Latham and Cockroft), the numerical model allowed to locate the areas where there is a risk of crack.

Experimental validation of the damage-plasticity modeling concept for normal strength concrete in fire

2018 ◽  
Vol 9 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Martin Neuenschwander ◽  
Claudio Scandella ◽  
Markus Knobloch ◽  
Mario Fontana
Keyword(s):  
Elevated Temperatures ◽  
Elastic Stiffness ◽  
Stiffness Degradation ◽  
Calibration Data ◽  
Compression Tests ◽  
Validation Data ◽  
Content Type ◽  
Softening Behavior ◽  
Fire Engineering ◽  
Modeling Concept

Purpose This paper aims to investigate with strain-rate controlled uniaxial cyclic compression tests the softening behavior of concrete and its elastic stiffness degradation with increasing plastic straining. Design/methodology/approach Such tests at ambient temperature show that concrete exhibits the phenomenon of elastic stiffness degradation, which can be captured by damage-plasticity models. Findings The experimentally derived evolutions of the elastic stiffness with plastic strain confirm the suitability of the damage-plasticity modeling concept for concrete in compression at elevated temperatures and provide novel calibration data. Originality/value Temperature-dependent concrete models implementing this modeling concept are often used presently in structural fire engineering, despite the lack of experiment-based validation data.

Design and Testing of a Thin-Flexure Bistable Mechanism Suitable for Stamping From Metal Sheets

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Benjamin Todd ◽  
Brian D. Jensen ◽  
Stephen M. Schultz ◽  
Aaron R. Hawkins
Keyword(s):  
Compliant Mechanisms ◽  
Elliptic Integral ◽  
Plane Motion ◽  
Acceleration Threshold ◽  
Metal Sheets ◽  
Out Of Plane ◽  
A New Technique ◽  
Bistable Mechanism ◽  
Force Displacement ◽  
Design And Testing

We present a new technique for fabricating compliant mechanisms from stamped metal sheets. The concept works by providing thinned segments to allow rotation of flexural beams 90 deg about their long axis, effectively providing a flexure as wide as the sheet’s thickness. The method is demonstrated with the design and fabrication of a metal bistable mechanism for use as a threshold accelerometer. A new model based on elliptic integral solutions is presented for bistable mechanisms incorporating long, thin flexures. The resulting metal bistable mechanisms are tested for acceleration threshold sensing using a drop test and a vibration test. The mechanisms demonstrate very little variation due to stress relaxation or temperature effects. The force-displacement behavior of a mechanism is also measured. The mechanisms’ switching force is less than the designed value because of out-of-plane motion and dynamic effects.

Hot Deformation Behavior of V-Microalloyed Steel

2010 ◽  
Vol 654-656 ◽  
pp. 310-313
Author(s):  
An Chao Ren ◽  
Yu Ji ◽  
Gui Feng Zhou ◽  
Ze Xi Yuan ◽  
Bin Han ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Cooling Rate ◽  
Deformation Temperature ◽  
Rail Steel ◽  
Compression Tests ◽  
Double Pass ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Softening Behavior ◽  
Transformation Curve

The dilatation curves of continuous cooling transformation at different cooling rates were determined for U75V rail steel by THERMECMASTOR-Z thermal simulator, and continuous cooling transformation curve was obtained. The influence of cooling rate on microstructure and hardness was studied. The softening behavior after isothermal deformation in the austenite region 850-1000°C but before the second pass was also studied by double-pass compression tests. The results show that the product of austenite decomposition was pearlite when the cooling rate was lower than 10°C. Troostite and martensite were gained at the cooling rate of 10°C•s-1. Only martensite was obtained when the cooling rate was in the range of 10-50°C•s-1. The hardness of the steel increased with the increase of cooling rate. Under the condition of 30% deformation and 3s-1 deformation rate, the relaxation time for completing recrystallization was shorter than 100s when the deformation temperature was higher than 1000°C. When the deformation temperature was lower than 880°C, full recrystallization was difficult to achieve even if the relaxation time was extended.

scholarly journals Repeated Loading Behavior of Pediatric Porcine Common Carotid Arteries

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Stephanie A. Pasquesi ◽  
Yishan Liu ◽  
Susan S. Margulies
Keyword(s):  
Mechanical Response ◽  
Peak Stress ◽  
Stretch Ratio ◽  
Repeated Loading ◽  
Contributing Factors ◽  
Softening Behavior ◽  
Longitudinal Stretch ◽  
Longitudinal Extension ◽  
Common Carotid Arteries ◽  
Flexion And Extension

Rapid flexion and extension of the neck may occur during scenarios associated with traumatic brain injury (TBI), and understanding the mechanical response of the common carotid artery (CCA) to longitudinal stretch may enhance understanding of contributing factors that may influence CCA vasospasm and exacerbate ischemic injury associated with TBI. Immature (4-week-old) porcine CCAs were tested under subcatastrophic (1.5 peak stretch ratio) cyclic loading at 3 Hz for 30 s. Under subcatastrophic cyclic longitudinal extension, the immature porcine CCA displays softening behavior. This softening can be represented by decreasing peak stress and increasing corner stretch values with an increasing number of loading cycles. This investigation is an important first step in the exploration of fatiguelike behavior in arterial tissue that may be subjected to repeated longitudinal loads.

Study on behaviour of geometrically scaled glass reinforced epoxy tubes subjected to non-coincident quasi static-indentation

2018 ◽  
Vol 9 (5) ◽  
pp. 675-692
Author(s):  
Fahad Almaskari ◽  
Farrukh Hafeez
Keyword(s):  
Peak Load ◽  
Repeated Loading ◽  
Damage Growth ◽  
Content Type ◽  
Starting Point ◽  
Static Indentation ◽  
Indentation Tests ◽  
Loading And Unloading ◽  
Force Displacement ◽  
Practical Implications

Purpose The purpose of this paper is to study the behaviour of glass reinforced epoxy tubes subjected to repeated indentation loads at two non-coincident indentations 180° apart. Design/methodology/approach Four geometrically scaled specimens ranging from 100 to 400 mm diameter were used in repeated indentation tests. Force, displacement and damage growth were recorded for loading and unloading until the indenter returned to its original starting point. Findings Similar scaled trends were observed between the non-coincidental loadings. Unlike reported response form coincidental loadings, the responses from non-coincidental loadings yield lower values for bending stiffness and peak load. Research limitations/implications The differences in behaviour of the specimen between non-coincident loadings were attributed to reductions in fracture toughness and circumferential modulus. Practical implications Distant non-interacting damage and delamination around the circumference does reduce the structural performance. Originality/value Behaviour of composite tubes under different loading conditions, for example low speed impact or quasi static indentation, is widely studied, however little attention has been given to the repeated loading incidents.

scholarly journals Micro-Mechanical Properties of Expanded Clay Particles

2019 ◽  
Vol 8 (11) ◽  
pp. 840-844
Keyword(s):  
Mechanical Properties ◽  
Power Law ◽  
High Variability ◽  
Compression Tests ◽  
Clay Particles ◽  
High Dependency ◽  
Crushing Force ◽  
Clay Aggregates ◽  
Force Displacement ◽  
Highly Porous

The aim of this paper is to study the micro-mechanical behavior of an industrial crushable and highly porous granular material. Lightweight Expanded Clay Aggregates (LECA) was selected in this research for testing thanks to its brittle nature and highly porous character which makes it easier to study the crushable behavior of this material. LECA’s micro-mechanical properties were identified to understand the parameters that affect particle’s crushing. Uniaxial compression tests, consisting on compressing the particles between two rigid platens, were made on a set of single LECA’s particles to investigate the force displacement response and the Hertzian behavior was identified as the contact law. The particles’ strengths were determined for tested granules using the crushing force and grains’ Young moduli were calculated using the suggested contact law. Due to their high variability, the particles’ crushing stress and their Young moduli were related to particle’s dimension using a suggested power law to predict these mico-mechanical properties. Results have shown a high dependency between the particle’s micro-mechanical properties and their dimensions.

Sign in / Sign up

Export Citation Format

Share Document