Nature Of Deformation Research Articles

Numerical Investigation with Failure Characteristic Analysis and Support Effect Evaluation of Deep-Turning Roadways

In recent years, tunnel-boring machines (TBMs) have been widely applied in deep coal mining. Turning is an inevitable challenge in TBM tunneling, and a TBM turning roadway exhibits greater instability than a straight roadway, as engineering experience has indicated. This study aimed to explore the failure mechanism and evaluate the support performance of a deep-turning roadway. Several numerical models were established to investigate the deformation of the roadway, the stress distribution, and the failure zone of the surrounding rocks under different tunneling conditions. The results show that the tunneling depth influences the failure pattern of the turning roadway: deep tunneling with high in situ stress can cause asymmetric failure of the turning roadway, while shallow tunneling with low in situ stress does not. Moreover, the change in turning radius, namely the change in roadway geometry, does not influence the stability of the turning roadway. In addition, the support actions for both the straight and turning roadways do not differ significantly, and the amount of controlled deformation of the surrounding rocks is proportional to their natural deformation.

Influence of water on crystallographic preferred orientation patterns in a naturally deformed quartzite

Abstract. Laboratory experiments demonstrate that intragranular water exerts an important control on deformation within quartz, causing weakening and promoting plasticity. The role of water in natural quartz deformation, however, remains unclear, as recent studies find an inverse relationship between water content and the magnitude of plastic strain. Furthermore, little work has investigated the effects, if any, of water on the relative activity of various slip systems in quartz. We focus on a naturally strained quartzite from the Antietam Formation of the Blue Ridge in Virginia, USA. Quartz water content ranges from < 50 to > 2000 ppm H2O. Water content and crystallographic data were correlated for 968 grains, enabling us to explore the relationship between water content and quartz crystallographic preferred orientation (CPO) patterns. “Dry” (< 150 ppm H2O) and “wet” (> 500 ppm H2O) subsets show distinct CPOs; c axes of dry grains define a cross girdle oriented perpendicular to the extension direction (x), whereas c axes of wet grains are concentrated along the perimeter of the pole figure. All water content subsets show grains clustered near the direction of maximum shortening (z), consistent with activity of the basal 〈a〉 slip system. The cross girdle in the driest grains suggests activity of prism 〈a〉 and possibly rhomb 〈a〉, whereas the orientation of the wettest grains implies a contribution from prism [c] slip. These slip system interpretations are supported by analyses of intragranular misorientations. These results indicate that water content impacts the relative activity of various slip systems in natural quartz, potentially affecting application of the quartz opening angle thermometer.

New cluster algebras from old: integrability beyond Zamolodchikov periodicity

Abstract We consider discrete dynamical systems obtained as deformations of mutations in cluster algebras associated with finite-dimensional simple Lie algebras. The original (undeformed) dynamical systems provide the simplest examples of Zamolodchikov periodicity: they are affine birational maps for which every orbit is periodic with the same period. Following on from preliminary work by one of us with Kouloukas, here we present integrable maps obtained from deformations of cluster mutations related to the simple root systems 
$A_3$, $B_2$, $B_3$ and $D_4$. We further show how new cluster algebras arise, by considering Laurentification, that is, a lifting to a higher-dimensional map expressed in a set of new variables (tau functions), for which the dynamics exhibits the Laurent property. For the integrable map obtained by deformation of type $A_3$, which already appeared in our previous work, we show that there is a commuting map of Quispel-Roberts-Thompson (QRT) type which is built from a composition of mutations and a permutation applied to 
the same cluster algebra of rank 6, with an additional 2 frozen variables. Furthermore, both the deformed $A_3$ map and the QRT map correspond to translation by a generator in the Mordell-Weil group of a rational elliptic surface of rank two, and the underlying cluster algebra comes from a quiver that is mutation equivalent to the $q$-Painlev\'e III quiver found by Okubo. 
The deformed integrable maps of types $B_2$, $B_3$ and $D_4$ are also related to elliptic surfaces. 

From a dynamical systems viewpoint, the message of the paper is that special families of birational maps with completely periodic dynamics under iteration admit natural deformations that are aperiodic yet completely integrable.

Nonrigid registration method for longitudinal chest CT images in COVID-19

Rationale and objectivesTo analyze morphological changes in patients with COVID-19-associated pneumonia over time, a nonrigid registration technique is required that reduces differences in respiratory phase and imaging position and does not excessively deform the lesion region. A nonrigid registration method using deep learning was applied for lung field alignment, and its practicality was verified through quantitative evaluation, such as image similarity of whole lung region and image similarity of lesion region, as well as visual evaluation by a physician. Materials and methodsFirst, the lung field positions and sizes of the first and second CT images were roughly matched using a classical registration method based on iterative calculations as a preprocessing step. Then, voxel-by-voxel transformation was performed using VoxelMorph, a nonrigid deep learning registration method. As an objective evaluation, the similarity of the images was calculated. To evaluate the invariance of image features in the lesion site, primary statistics and 3D shape features were calculated and statistically analyzed. Furthermore, as a subjective evaluation, the similarity of images and whether nonrigid transformation caused unnatural changes in the shape and size of the lesion region were visually evaluated by a pulmonologist. ResultsThe proposed method was applied to 509 patient data points with high image similarity. The variances in histogram characteristics before and after image deformation were confirmed. Visual evaluation confirmed the agreement between the shape and internal structure of the lung field and the natural deformation of the lesion region. ConclusionThe developed nonrigid registration method was shown to be effective for quantitative time series analysis of the lungs.

Semantic-aware hyper-space deformable neural radiance fields for facial avatar reconstruction

High-fidelity facial avatar reconstruction from monocular videos is a prominent research problem in computer graphics and computer vision. Recent advancements in the Neural Radiance Field (NeRF) have demonstrated remarkable proficiency in rendering novel views and garnered attention for its potential in facial avatar reconstruction. However, previous methodologies have overlooked the complex motion dynamics present across the head, torso, and intricate facial features. Additionally, a deficiency exists in a generalized NeRF-based framework for facial avatar reconstruction adaptable to either 3DMM coefficients or audio input. To tackle these challenges, we propose an innovative framework that leverages semantic-aware hyper-space deformable NeRF, facilitating the reconstruction of high-fidelity facial avatars from either 3DMM coefficients or audio features. Our framework effectively addresses both localized facial movements and broader head and torso motions through semantic guidance and a unified hyper-space deformation module. Specifically, we adopt a dynamic weighted ray sampling strategy to allocate varying degrees of attention to distinct semantic regions, enhancing the deformable NeRF framework with semantic guidance to capture fine-grained details across diverse facial regions. Moreover, we introduce a hyper-space deformation module that enables the transformation of observation space coordinates into canonical hyper-space coordinates, allowing for the learning of natural facial deformation and head-torso movements. Extensive experiments validate the superiority of our framework over existing state-of-the-art methods, demonstrating its effectiveness in producing realistic and expressive facial avatars. Our code is available at https://github.com/jematy/SAHS-Deformable-Nerf.

Revisiting Artifacts of Kohn-Sham Density Functionals for Biosimulation.

We revisit the problem of unphysical charge density delocalization/fractionalization induced by the self-interaction error of common approximate Kohn-Sham (KS) density functional theory functionals on simulation of small to medium-sized proteins in a vacuum. Aside from producing unphysical electron densities and total energies, the vanishing of the HOMO-LUMO gap associated with the unphysical charge delocalization leads to an unphysical low-energy spectrum and catastrophic failure of most popular solvers for the KS self-consistent field (SCF) problem. We apply a robust quasi-Newton SCF solver [ Phys. Chem. Chem. Phys. 2024, 26, 6557] to obtain solutions for some of these difficult cases. The anatomy of the charge delocalization is revealed by the natural deformation orbitals obtained from the density matrix difference between the Hartree-Fock and KS solutions; the charge delocalization not only can occur between charged fragments (such as in zwitterionic polypeptides) but also involves neutral fragments. The vanishing-gap phenomenon and troublesome SCF convergence are both attributed to the unphysical KS Fock operator eigenspectra of molecular fragments (e.g., amino acids or their side chains). Analysis of amino acid pairs suggests that the unphysical charge delocalization can be partially ameliorated by the use of some range-separated hybrid functionals but not by semilocal or standard hybrid functionals. Last, we demonstrate that solutions without the unphysical charge delocalization can be located even for semilocal KS functionals highly prone to such defects, but such solutions have non-Aufbau character and are unstable with respect to mixing of the non-overlapping "frontier" orbitals. Caution should be exercised when unexpectedly small (or vanishing) HOMO-LUMO gaps and atypical SCF convergence patterns (e.g., oscillatory) are observed in KS DFT simulations in any context (bio or otherwise).

Evidence of Dislocation Mixed Climb in Quartz From the Main Central and Moine Thrusts: An Electron Tomography Study

AbstractIn this study we apply electron tomography to characterize 3D dislocation microstructures in two quartz mylonite specimens from the Moine and Main Central Thrusts, both of which accommodated displacements by dislocation creep in the presence of water. Both specimens show dislocation activity with dislocation densities of the order of 3–4 × 1012 m−2 and evidence of recovery from the presence of subgrain boundaries. 〈a〉 slip occurs predominantly on pyramidal and prismatic planes (〈a〉 basal glide is not active). [c] Glide is not significant. On the other hand, we observe a very high level of activation of 〈c + a〉 glide on the , , (n = 1,2) and even planes. Approximately 60% of all dislocations show evidence of climb with a predominance of mixed climb, a deformation mechanism characterized by dislocations moving in a plane intermediate between the glide and the climb planes. This atypical mode of deformation demonstrates comparable glide and climb efficiency under natural deformation conditions. It promotes dislocation glide in planes not expected for the quartz structure, probably by inhibiting lattice friction. Our quantitative characterization of the microstructure enables us to assess the strain that dislocations can generate. We show that glide systems indicated by the observed dislocations are sufficient to accommodate any arbitrary 3D strain by themselves. Although historically dislocation glide has been regarded as being primarily responsible for producing strain, activation of climb can also directly contribute to the finite strain. On the basis of this characterization, we propose a numerical modeling approach for attempting to characterize the local stress state that gave rise to the observed microstructure.

Generation of realistic synthetic cable images to train deep learning segmentation models

Semantic segmentation is one of the most important and studied problems in machine vision, which has been solved with high accuracy by many deep learning models. However, all these models present a significant drawback, they require large and diverse datasets to be trained. Gathering and annotating all these images manually would be extremely time-consuming, hence, numerous researchers have proposed approaches to facilitate or automate the process. Nevertheless, when the objects to be segmented are deformable, such as cables, the automation of this process becomes more challenging, as the dataset needs to represent their high diversity of shapes while keeping a high level of realism, and none of the existing solutions have been able to address it effectively. Therefore, this paper proposes a novel methodology to automatically generate highly realistic synthetic datasets of cables for training deep learning models in image segmentation tasks. This methodology utilizes Blender to create photo-realistic cable scenes and a Python pipeline to introduce random variations and natural deformations. To prove its performance, a dataset composed of 25000 synthetic cable images and their corresponding masks was generated and used to train six popular deep learning segmentation models. These models were then utilized to segment real cable images achieving outstanding results (over 70% IoU and 80% Dice coefficient for all the models). Both the methodology and the generated dataset are publicly available in the project’s repository.

Mechanical properties of soils in internal waste bank of lignite mines and their primary characteristics

The modern development of urban areas is related to, among others, the location of industrial facilities on the outskirts of cities. More and more often, commercial buildings are founded on areas that have not been used for construction so far. Such areas include, among others: reclaimed lignite mine banks in the Konin region. The man-made soil is a chaotic mixture of fragments of glacial tills and Pliocene clays, often exceeding 20 m in thickness, which is naturally consolidated over time. Due to the method of formation of the embankment, despite the fact that banks are made of natural soil, their strength and deformation characteristics clearly differ from those characteristic of lithologically similar soils deposited as a result of geological processes. In this case, the use of a standard test approach may overestimate the strength and stiffness of the soil. Due to the complex structure of the bank in-situ tests were used for geotechnical exploration: CPTU and FVT, as well as laboratory tests in a triaxial apparatus and an oedometer. The results were compared with the results of studies conducted in similar naturally deposited soils. The obtained results provide valuable geotechnical characteristics of the embankment soil, which in its large fragments is built of natural soil clasts. The obtained results indicate a relatively small change in the geotechnical properties of the soils incorporated into the embankment within individual clasts of the natural soil (on a local scale) and a clear deterioration in the scale of the entire embankment, treated as the impact zone of building structures.

Photonic implementation of the quantum Morra game

The Morra game, an age-old noncooperative game, traditionally played on one's hand, has proved to be a rich setting to study game-theoretic strategies, both classically and within the quantum realm. In this paper, we study a faithful translation of a two-player quantum Morra game, which builds on previous study by including the classical game as a special case. We propose a natural deformation of the game in the quantum regime in which Alice has a winning advantage, breaking the balance of the classical game. A Nash equilibrium can be found in some cases by employing a pure strategy, which is impossible in the classical game where a mixed strategy is always required. We prepared our states using photonic qubits on a linear optics setup, with an average deviation ≤2% with respect to the measured outcome probabilities. Finally, we discuss potential applications of the quantum Morra game to the study of quantum information and communication. Published by the American Physical Society 2024

Design, Analysis, and Wind Tunnel Evaluation of Novel Fabric-Covered Rotor Blades in Wind Energy Generation

This paper investigates the performance of a novel fabric-covered rotor blade. The study aims to address the need for cost-effective wind turbine blades by exploring the potential of textile-based materials. The research includes a comprehensive wind tunnel experiment to evaluate the aerodynamic response of the fabric-covered blade, compared to a traditional hard-shell blade. The experimental data are systematically processed and corrected for wind tunnel effects, providing valuable insights into the aerodynamic behavior of the novel blade. The results show that the fabric-covered blade, constructed from PTFE-coated fiberglass fabric, exhibits promising aerodynamic characteristics, with potential applications in reducing manufacturing expenses and enhancing power generation. The study concludes by proposing a novel control strategy leveraging the natural deformation of blades at high wind speeds, suggesting potential applications in limiting power output at high wind speeds. Overall, these findings contribute to the ongoing efforts in developing innovative and cost-efficient solutions for wind energy generation.

Shaking table tests of power distribution cabinets: Physical damage, post-earthquake functionality and seismic response evaluation

Power distribution cabinets (PDCs) are widely used in several critical facilities to ensure the power supply and distribution. Although these cabinets may suffer seismic damage during earthquakes, and result in cascading functionality, economic and life losses, they have received little attention in terms of seismic performance. Therefore, there is an increasing need to understand the performance of such equipment during earthquakes. This study conducted shaking table tests on three PDCs to investigate the seismic performance and dynamic responses. Both physical damage and post-earthquake functionality evaluation were conducted during shaking table tests. The seismic responses of tested cabinets including natural frequency, stress, acceleration, and deformation responses were presented in detail. Seismic qualification levels of tested cabinets based on existing rules were also introduced. This paper not only enlarges the experimental database of the seismic performance of PDCs, but also provides basic data and rules for performance-based seismic evaluation of such nonstructural components.

The role of twinning and stacking fault-induced plasticity on the mechanical properties of aluminum-lithium-graphene nanocomposites

In this study, the synthesis-structure-property relationship of graphene-reinforced Al matrix nanocomposites was investigated. The Al-Li-GNPs nanocomposite was synthesized to attain both high strength and good ductility. The incorporation of GNPs as a reinforcement in the Al-based matrix provided a nanocomposite structure for an integrated strengthening effect. To promote plasticity and maintain good ductility, the nanocrystalline Al matrix was alloyed with Li to reduce its stacking fault energy and promote additional deformation mechanisms. The compressive yield strength (CYS) increased from 88 MPa for the starting Al to 403 MPa for the Al-Li-GNPs nanocomposites with 1.0 wt% GNPs. Fracture analysis indicated that the synthesized nanocomposite exhibited a ductile nature and significant plastic deformation. Based on microscopic analysis, the enhanced strength of the Al-Li-GNPs nanocomposite was attributed to grain refinement, load transfer, and strain hardening. The good ductility, on the other hand, was attributed to dislocation slipping, the formation of stacking faults, and twinning.

Shaking table tests of a switching power cabinet considering physical damage and functionality loss

Switching power cabinets are critical equipment that converts alternating current (AC) to direct current (DC) for electrical power system of telecommunication buildings. Post-earthquake damage to the cabinet may result in entire functionality loss of telecommunication buildings, which will have a significant impact on post-earthquake emergency response. In this study, unidirectional shaking table tests were conducted separately in X-direction and Y-direction to evaluate the seismic responses of a switching power cabinet. The seismic input motion was generated based on required response spectrum of YD 5083 code. The peak table acceleration levels were scaled from 0.3 g to 2.5 g in order to capture progressive damage of the switching power cabinet. Based on the test results, the physical damage and functionality loss of tested cabinet were analyzed first. Then the response characteristics of the cabinet were evaluated and explained in terms of the natural frequency, acceleration, and deformation response. Both outside cabinet and in-cabinet acceleration amplification factors were analyzed. The seismic fragility curves of switching power cabinet were also developed considering four observed seismic damage states.

Experimental study on drilling of soft rocks

Drilling is commonly occurring material deformation process in vast range of industries including manufacturing, mining, petroleum, infrastructure, biomedical etc. Due to its three-dimentional nature and multi-axial deformation of material, drilling is a very complex process involving severe plastic deformation of material, high strain and strain rates, volume change, tempretarure gradient etc. In addition to this, drilling in rocks becomes further more complicated due to additional complexity added by brittle fracture. Therefore, it becomes important to have a complete understanding of the process and the effect of drilling paramerets on the material response in order to make it more energy efficient and improve the productivity in industrial applications.
 An attempt to understand the drilling in metals has been made by using a simplistic approach of decoupling the process into simpler process where, the penetration of the drill into the material and the rotatory motion has been correlated to indentation and cutting, respectively [1, 3, 8]. Similar framework has been adopted for rocks by many researchers where drill bits consist of many polycrystalline diamond compact cutters mounted on a tingesten carbide matrix [2, 5, 7]. In order to understand the interaction of these bits with rock, simplified models have been proposed for the cutters mounted on these bits [6]. This research work intends to understand the drilling mechanism experimentally by comparing drilling response (thrust force and torque) with the findings of intentation and cutting studies. Also, the force response (thrust and torque) were compared with the results obtained from the model.
 Drilling experiments were performed on samples prepared using gypsum, which is an ideal model material for soft rocks [4, 9]. Sample porosity was controlled by controlling the water content during casting of the samples (46 mm x 46 mm x 20 mm). Twist drills with helix angle of 300 and 600 were used. The diameter of the drill (6 mm) was kept significantly smaller (~ 8 times) than the width of the sample. The tip angle was kept constant (1200) for both the drills. The penetration rate was varied from 1 – 100 mm/min at constant rotation speed of 100 rpm. The penetration rate in combination with the rotation speed can be seen as depth of cut per revolution of the drill. The thrust force and torque were normalized with respect to the drill radius to compare the signatures with indentation [10, 11] and cutting [12] experiment results, respectively.
 On comparing normalized thrust and torque signatures with indentation and cutting results, a remarkable similarity was observed. Figure 1 and 2 show normalized thrust and normalized torque, respectively, as a function of depth of cut per revolution (penetration rate/ rotation speed). Similar to indentation results, Fig.1a shows that the thrust force has a strong dependence on material porosity but remained independent of drill geometry (Fig. 1b). This indicated that the drill geometry (which is responsible for cutting the material) does not influence the indentation part (vertical penetration). In contrast to this, the normalized torque showed dependence on both, drill geometry and porosity (Fig. 2) which was evident from studies performed gypsum cutting [12]. Also, the torque signatures were remarkably similar to cutting forces and cyclic peaks were observed which indicated cyclic removal of the chips during cutting. The drilling results were compared with the theoretical model as well [6]. However, results corresponding to the 300 helix angle drill did not align with the model predintions. Suitable modifications in the model was suggested. Based on some preliminary experiments performed by imaging the drilling process, it was believed that there exists an optimum helix angle for which the model presdintions hold good.
 This study shows experimentally that drilling, which is a complex 3 dimentional process, can be studied by decoupling it into simpler 2 dimentional processes: cutting and indentation. The similarity between the experimental findings of cutting, indentation and drilling suggest that the findings of cutting and indentation studies can be clubbed together and can be used to understand drilling better.

Numerical modeling of fractures interaction for EGS

Geothermal energy is a promising source of clean renewable energy that does not depend on weather conditions and has the potential of providing base load as well as peaking electrical supply. During the last twenty years, application of the geothermal energy for electricity generation, heating and cooling have increased noticeably in many countries, including USA, Iceland, New Zealand, Turkey, and Indonesia. The worldwide installed geothermal power capacity is approximately 16 MWe, with a growth rate estimated between 3.4% to 5.4% per year over the period between 2015 to 2060, according to the World Energy Council [1]. Geothermal energy has the potential to provide 3% of electricity and 5% of heating with respect to the global demand by 2050 [2].
 Enhanced Geothermal System enables producing geothermal energy from Hot Dry Rock (HDR) reservoirs, which are deficient in water and permeability, the two basic components necessary to exploit their geothermal potential (e.g., [3, 4]). EGS implementation requires the drilling of injection and production wells. Through the first one a cold fluid is injected, whereas hot water and/or steam is recovered from the production well. A key feature of this methodology is the network of fractures that connect these two wells. The discontinuities can be either, (naturally) pre-existing fractures, or (artificially) triggered fractures by the thermal shock induced by the contact between the cool injection fluid and the hot natural rock. Water or liquid nitrogen are contemplated as potential injection fluids. This type of project envisages reservoirs at depth with temperature above 180°C. Several field tests in different countries have been conducted to evaluate the feasibility of EGS (e.g., [3, 4, 5, 6, 7, 8, 9, 10, 11, 12]), including the ongoing Utah-FORGE project in the USA (e.g., [13]).
 Numerical modeling of the interaction between hydraulic driven fractures (HF) and natural fractures (NF) is still a challenging problem, since the presence of NFs introduce heterogeneity on the hydromechanical properties of the rock mass and affects the geometry of the HF. Therefore, the development of robust numerical methods able to address this kind of phenomena is crucial for the safe application of stimulation techniques. This work presents a finite element (FE) technique, called mesh fragmentation technique (MFT) [14], capable of tackling this type of problem. The MFT consists in introducing solid high-aspect ratio finite elements in-between the regular (bulk) finite elements to simulate both NFs and the formation and propagation of HFs. This MFT has been successfully used to model drying cracks in soils [15, 16], hydraulic fracturing in rocks [17, 18] and natural fractures deformation due to pressure depletion [19]. The fully coupled hydro-mechanical approach has been implemented in the FE program CODE_BRIGHT. The paper presents the main theoretical components and implementation of the proposed approach. Numerical examples are used to demonstrate the capabilities of the proposed technique. Figure 1 presents the pressure contours related to the modeling of the hydraulic fracturing of two neighbor wells in a naturally fractured rock. A very satisfactory performance of the proposed method is observed in all the analyzed cases.

Underground Gas Storage Monitoring Using Free and Open Source InSAR Data: A Case Study from Yela (Spain)

Gas consumption is subject to large seasonal fluctuations between the summer season (period with lower request) and the winter season (time with increased consumer demand). Underground gas storage applications (UGS) help to ensure a steady and reliable supply of natural gas, even during periods of peak demand, smoothing price fluctuations and providing a means of balancing the supply and demand of natural gas on a daily, weekly, or seasonal basis. However, UGS activities can induce vertical ground displacement, which is usually strictly associated with the injection and withdrawal of gas into/from the reservoir. It is necessary to carefully monitor and manage the potential impact of UGS activities on the subsurface and surface to ensure the stability and safety of the local environment. The Interferometric Synthetic Aperture Radar (InSAR) technique can provide a wide range of high-precision information on seasonal surface deformation associated with UGS activities useful for increasing the amount of information on ground deformation monitoring. This study introduces a unique and replicable approach to investigating freely available ground movement data for a fractured aquifer reservoir located in the Madrid Basin (Guadalajara, Spain), which is currently employed for seasonal underground gas storage applications. Notably, this study gives a comprehensive comparison of InSAR results of UGS activity in a deep aquifer, leveraging data that are entirely open-source and easily accessible. The Yela UGS project exploits a carbonate reservoir (dolomite) managed, since 2012, by Enagás, the Spanish main Transmission System Operator (TSO). InSAR data from 2015 to 2021 provided a full and coherent ground deformation pattern of the area. Based on this data, a fully integrated volumetric variation model was developed, elucidating the effects of gas storage activity. A significant correlation between the periodic injection/withdrawal rates of natural gas and InSAR ground deformation over time was identified.

Simultaneous improvement in strength and ductility in 7xxx Al through a combination of natural aging and deformation

Room temperature processing methods of reaching near-T6 yield and ultimate tensile strength in Al–Zn–Mg–Cu alloys provide a potentially lower cost alternative to high temperature forming and post-forming artificial aging methods. This study demonstrates a method, where a combination of pre-deformation and natural aging matched T6 strength along with ductility and strain hardening greater than the T6 values. Tensile deformation of 5% and 10% was applied to naturally aged samples at 144 h (6 days) and the samples were further naturally aged up to 220 days. The pre-deformed samples showed strong type A Portevin-Le Chatelier (PLC) banding with limited ductility and strain hardenability. Further natural aging increased both strength and ductility simultaneously and converted PLC to type B. This resulted in the same yield strength as T6 temper in the 10% deformed sample but with almost 77% greater total ductility (including the 10% pre-deformation). The simultaneous increase in strength and ductility was attributed to the small, shearable clusters/precipitates and solutes present in the microstructure as suggested by the changes in the PLC behavior.

Affine Geometry and Relativity

We present the basic concepts of space and time, the Galilean and pseudo-Euclidean geometry. We use an elementary geometric framework of affine spaces and groups of affine transformations to illustrate the natural relationship between classical mechanics and theory of relativity, which is quite often hidden, despite its fundamental importance. We have emphasized a passage from the group of Galilean motions to the group of Poincaré transformations of a plane. In particular, a 1-parametric family of natural deformations of the Poincaré group is described. We also visualized the underlying groups of Galilean, Euclidean, and pseudo-Euclidean rotations within the special linear group.

Multifunctional Materials Strategies for Enhanced Safety of Wireless, Skin‐Interfaced Bioelectronic Devices

AbstractMany recently developed classes of wireless, skin‐interfaced bioelectronic devices rely on conventional thermoset silicone elastomer materials, such as poly(dimethylsiloxane) (PDMS), as soft encapsulating structures around collections of electronic components, radio frequency antennas and, commonly, rechargeable batteries. In optimized layouts and device designs, these materials provide attractive features, most prominently in their gentle, noninvasive interfaces to the skin even at regions of high curvature and large natural deformations. Past studies, however, overlook opportunities for developing variants of these materials for multimodal means to enhance the safety of the devices against failure modes that range from mechanical damage to thermal runaway. This study presents a self‐healing PDMS dynamic covalent matrix embedded with chemistries that provide thermochromism, mechanochromism, strain‐adaptive stiffening, and thermal insulation, as a collection of attributes relevant to safety. Demonstrations of this materials system and associated encapsulation strategy involve a wireless, skin‐interfaced device that captures mechanoacoustic signatures of health status. The concepts introduced here can apply immediately to many other related bioelectronic devices.