Deformation Conditions Research Articles

Prediction of the hot flow behavior of AISI 321 stainless steel during dynamic recrystallization using sine hyperbolic constitutive equation and artificial neural network

The hot compression deformation behavior of AISI 321 austenitic stainless steel were studied under the strain rate and temperature ranges of 0.001–1 s−1 and 950–1200°C. The single peak hot flow curves indicated the occurrence of dynamic recrystallization in AISI 321 steel at applied deformation conditions. The microstructural observations showing the development of equaxed austenite grains further approved the results of flow curve analysis. The average size of austenite grains, when deformation is carried out at strain rate of 1 s−1, increases from 8 μm at 950°C to 61 μm at deformation temperature of 1200°C. After microstructure analysis, the flow behavior of AISI 321 steel was modeled using sine-hyperbolic constitutive equation and feed-forward back propagation artificial neural network. The mean absolute error related to the predicted flow stress values at different strains with the sine-hyperbolic constitutive equation is more than 2, and this value is less than unity for the neural network method. The obtained results efficiently indicate that the ANN model is more accurate in predicting the flow behavior of AISI 321 austenitic stainless steel when the dynamic recrystallization is the prevailing softening mechanism.

Adaptive stiffness structures via additively manufactured fluid accumulators

Abstract Lightweight mechanical structures often have low stiffness that prevents their use in structural applications. The demand for lightweight mechanical structures that operate under wide-ranging loading conditions motivates the development of adaptive stiffness structures. The ability to control the stiffness of a mechanical structure allows for tailored static and dynamic properties, including resonant frequencies. However, adaptive stiffness structures that are low cost, offer design flexibility, and can be additively manufactured still remain a challenge. To this end, we introduce adaptive stiffness devices called Pressure-actuated Adaptive Structural Cells (PASCells) with controllable axial stiffness. The proposed PASCells consist of four, flat arches that seal at the edges to contain a working fluid. The axial stiffness of the PASCell increases when the enclosed working fluid is compressed due to volume reduction under an axial load. Axial compression of a PASCell creates large internal volume change and internal pressure that resists this compression, increasing stiffness when the fluid volume is constrained by, for example, closing an outlet valve. Designed for additive manufacturing, PASCells can be integrated with mechanical structures to enable adaptive stiffness. In this paper, we derive the governing equations that describe the static deformation of PASCells under an axial load and internal pressurization and experimentally evaluate the stiffness of the PASCells in empty (or open valve) and filled (or closed valve) configurations. Single, series-connected, and parallel-connected PASCells are additively manufactured and experimentally tested, verifying the model predictions, and experimentally demonstrating a 70% stiffness increase.

CALCULATION OF STATIC DEFORMATION OF AXISYMMETRIC SHELLS OF ROTATION WITH DIFFERENTIAL MODEL

In the paper differential equations of static geometrically nonlinear deformation of axisymmetric shell of rotation are obtained. The resolving functions are projections of vectors in the global coordinate system. The equations allow describing any geometry of meridian (breaks, curvature jumps), large deformations, changing of shell thicknesses during deformation, also cross shears characteristic for thick shells. For the numerical solution, the approach based on the finite difference method is applied, which is realized in the own software package for the calculation of the mechanics of spatial rod systems – DARSYS. The calculations of test problems of the internal pressure inflation of cylindrical, spherical, elliptical, conical shells, as well as a combined conicalcylindrical shell with a meridian break are presented. Graphs of convergence of displacements at the reference points as a function of mesh density and under load variation are given, and deformed meridian configurations are plotted. The solutions obtained in ANSYS by different finite elements of Shell type were used as a reference for comparison. APDL scripts for parametric calculations of the test problems are given in the text of the paper. The proposed approach to the calculation of static deformation of shells of rotation has shown good agreement with finite element modeling in ANSYS (including thick shells) and in the future will be extended to the modeling of dynamic deformation and the possibility of solving coupled problems of interaction with liquid or gas. The given equations of the axisymmetric shell are a special case of the general equations, the development and application of which are beyond the scope of this paper, and the obtained solution results are the first stage of testing the developed complex approach to the calculation of static and dynamic deformation of shells, alternative to finite-element modeling.

Method for establishing the multipath adaptive mitigation model considering deformation displacement of monitoring stations

ABSTRACT Multipath effects are an unavoidable error in Global Navigation Satellite System (GNSS) deformation monitoring. Existing multipath models are predominantly established under stationary conditions and are not applicable to scenarios involving slope ruptures or rapid displacements. To address this issue, we propose the Multipath Adaptive Mitigation Model (MAMM) and validate its precision. The study demonstrates that traditional multipath models are ineffective in suppressing multipath errors under the specified conditions. The comparison between MAMM and the Multipath Hemispherical Model (MHM) indicates that, in the simulated displacement experiments, MHM’s effectiveness in mitigating multipath errors significantly decreases as the actual displacement distance increases, whereas MAMM consistently maintains an improvement rate in positioning precision of over 100%, markedly surpassing that of MHM. In real displacement scenarios, MAMM demonstrates similar advantages to those observed in the simulated experiments under instantaneous deformation conditions, while in slow displacement scenarios, MAMM offers a limited precision advantage over MHM.

Experimentation Evaluation of Dynamics of Steel Wire Rope

Wire ropes represent a distinct category of ropes synthesized through the intertwining or braiding of individual steel wires. This unique construction confers notable attributes such as strength, flexibility, and durability to the resultant rope. The pervasive wire ropes across diverse industries underscores their capacity to adeptly manage substantial loads and endure adverse environmental conditions finding its application in mechanical, civil, mining, and marine engineering. This paper presents usage of image processing method to detect the deflection of a steel wire rope. The system comprises of dividing the wire rope into different sections, spatial referencing, frame separation, color-based detection, morphological operations, data collection and visualization. The steel wire rope deflection program will allow designers to conveniently process the transverse deflection trajectories of a steel wire rope in real time. One may further introduce any control actions when the deflection distance reaches a threshold value. The image-based algorithm enabled a robust detection of the deformed shape as a function of time, thus obtaining its dynamic trajectories. The deflection shapes and trajectories are compared with numerical predictions made using Cosserat Rod theory, which considers the geometric nonlinearities introduced due to large deflection. The numerical solution gave a rough estimate of the static deformation state of the wire, which agrees with the experimental results. This study will be useful for Structural Health Monitoring, Safety Assurance, Fatigue Analysis and Performance optimization. Moreover, the Continuum Mechanics employs Cosserat rod theory to model continuum robots which will provide enhanced computational efficiency and better dynamic simulation capabilities[18]. The deflection shapes and trajectories are compared with analytical predictions made using Cosserat Rod theory, which considers the geometric nonlinearities introduced due to large deflection.

Bioinspired adaptive lipid-integrated bilayer coating for enhancing dynamic water retention in hydrogel-based flexible sensors

While hydrogel-based flexible sensors find extensive applications in fields such as medicine and robotics, their performance can be hindered by the rapid evaporation of water, leading to diminished sensitivity and mechanical durability. Despite the exploration of some effective solutions, such as introducing organic solvents, electrolytes, and elastomer composites, these approaches still suffer from problems including diminished conductivity, interface misalignment, and insufficient protection under dynamic conditions. Inspired by cell membrane structures, we developed an adaptive lipid-integrated bilayer coating (ALIBC) to enhance water retention in hydrogel-based sensors. Lipid layers and long-chain amphiphilic molecules are used as compact coating and anchoring agents on the hydrogel surface, mimicking the roles of lipids and membrane proteins in cell membranes, while spare lipids from aggregates within hydrogels can migrate to the surface to combat dehydration under deformation. This lipid-integrated bilayer coating prevents the water evaporation of hydrogels at both static and dynamic states without affecting the inherent flexibility, conductivity, and no cytotoxicity. Hydrogel-based sensors with ALIBC exhibited significantly enhanced performance in conditions of body temperature, extensive deformation, and long-term dynamic sensing. This work presents a general approach for precisely controlling the water-retaining capacity of hydrogels and hydrogel-based sensors without compromising their intrinsic physical properties.

Effect of high-temperature shear deformation on the synthesis of TiB<sub>2</sub>‒ZrO<sub>2</sub> composite material under conditions of free SHS compression

Ceramic materials based on TiB2 and stabilized ZrO2 were obtained by self-propagating high-temperature synthesis (SHS). The stabilization of the high-temperature phases of ZrO2 was carried out by introducing Y2O3 into the initial mixture. The effect of the Y2O3 content on the combustion characteristics of the studied materials, as well as on the phase composition of synthesis products in the range of Y2O3 concentrations from 0 to 6,2 wt. %, was studied. Gorenje. To study the effect of high-temperature shear deformation on the synthesis process by free SHS compression, compact plates with dimensions of 50×50×7 mm were obtained based on the studied compositions. It has been established that as a result of the synthesis of materials obtained under conditions of high-temperature shear deformation and without pressure application, the reaction products have different phase compositions. The resulting compact plates are composite materials consisting of a matrix based on stabilized ZrO2 with TiB2 particles distributed in it.

Refining metamorphic-time paths with deformation conditions: the exhumation history of the southernmost part of Brasília Orogen, Brazil

Refining metamorphic-time paths with deformation conditions: the exhumation history of the southernmost part of Brasília Orogen, Brazil

Effect of the flow behavior and dynamic recrystallization of EH420 marine steel on the morphology evolution of martensite substructures

The hot deformation behavior of EH420 marine steel was investigated by isothermal compression tests in the temperature range of 850~1050°C and the strain rate range of 0.01~10s−1. A high-temperature constitutive model and a hot processing map were developed. The results indicated that the microstructure of EH420 marine steel after hot deformation was mainly bainite and lath martensite. The martensite blocks gradually coarsened with the increase in temperature within the range of 950~1050°C/0.01s-1, and the average width increased from about 0.7 μm to 2.3 μm. At high strain rates, martensite blocks became coarse and disordered due to flow instability. The flow stress curve showed a single peak when the strain rate was low. There were more dynamic recrystallization (DRX) structures, resulting in fine and ordered martensite blocks. Under the deformation conditions of 0.1~10s-1/1000°C, the proportion of high-angle grain boundaries (HAGBs) decreased from 53.5% to 40.7% as the strain rate increased. Meanwhile, the hot deformation mechanism shifted from discontinuous dynamic recrystallization (DDRX) to the combined effect of DDRX and dynamic recovery (DRV) and finally transformed into DRV. The flow stress derived from the constitutive model was consistent with the experimental results. The activation energy of EH420 marine steel was 3.16×105J/mol. The optimal hot processing parameters were 950~1050°C and 0.01~0.1s-1.

Fabrication of bismuth-telluride thermoelectric wires by friction extrusion

Efficient conversion of low-grade heat into electric power is challenging for thermoelectric materials and systems. This is because the high-aspect ratio thermoelectric elements needed for maximum conversion efficiency are difficult and costly to manufacture. In this work, friction extrusion is explored as a new method for fabricating bulk bismuth-telluride (BiTe) wires that can be sectioned into high-aspect ratio thermoelectric elements. Bismuth-telluride feedstock materials in the form of vacuum hot-pressed powder and castings are processed by friction extrusion into meters-long wires having 2.5 mm and 1.0 mm diameters. The novel deformation process gives an average grain size below 5 µm and preferential c-axis texture alignment perpendicular to the extrusion direction. Results for Seebeck coefficient, resistivity, power factor, and weighted mobility show that transport properties exceeding that of high-performance vacuum hot-pressed powders are achieved through friction extrusion of simple castings. The unique deformation conditions at the rotating die/feedstock interface enables a much higher extrusion ratio (161:1) than is possible with conventional extrusion. This is a key enabler for extruding small wire diameters from cast billets.

Performance prediction of 304 L stainless steel based on machine learning

With the development of testing technology and data mining methodologies, machine learning (ML) has been widely applied for predicting the performance of materials in various systems including stainless steel with improved performance. To address the limitations of traditional experimental and statistical methods in predicting the thermal deformation of materials, a predictive machine learning model was developed based on the data obtained from thermal simulation compression tests. Specifically, the Arrhenius and the Modified Johnson-Cook (J-C) Constitutive Model were developed utilizing experimental data to initially predict the rheological behavior of 1.52% Cu-304L stainless steel. Then, a physical metallurgy (PM)-guided Back Propagation (BP) model was developed, and Genetic Algorithm (GA), Whale Optimization Algorithm (WOA), and Mind Evolutionary Algorithm (MEA) were incorporated into the model for optimization purposes, respectively. Finally, the results indicate that the PM-MEA-BP model exhibits superior predictive performance, accurately forecasting the texture evolution of 304L stainless steel with random crystal orientation under rolling deformation conditions. Additionally, the present work also clearly demonstrated that the model not only satisfies precision requirement but also has certain guiding significance for optimizing process parameters and forecasting the microstructure and properties of stainless steel.

FEM Analysis of Crane Hooks with Different Cross Section

In this paper the 3D model of the crane hook was realized using Autodesk Inventor Professional 2025 and finite element analysis, was performed using Ansys Workbench, in order to determine the state of stress, deformation and safety factor, by applying restrictions and loads conditions. Two materials were chosen, for crane hook, in accordance with the specialized literature. The materials taken for static analysis was Stainless Steel AISI 1020 and 34CrMo4. The FEM analysis of a crane hook provides critical information for evaluating the design's structural integrity, identifying potential problem areas, and ensuring that the hook can safely carry the loads it is intended to handle.

Morphology and Properties of the Laser-Irradiated Composition “Chrome Coating — Copper Substrate”

Introduction. During pulsed laser processing and modification of the surface of non-ferrous alloys and coatings based on them, several still unresolved issues arise. In particular, the extreme thermal deformation conditions of laser processing are not linked to the peculiarities of structure formation and formation of properties in irradiated “coating — copper substrate” compositions. A metal physical analysis of the possibility and reasons for increasing the adhesion strength of coatings to a metal (copper) substrate during high-speed laser processing is insufficiently substantiated and evidence-based. To make a reasonable choice of technological parameters for the surface hardening mode of non-ferrous alloy products, as well as for obtaining high-quality workable composite layers on their surface, it is necessary to solve the above issues and tasks. The aim of this article is to determine the possibility and conditions for increasing the adhesion strength of a chrome coating to a copper substrate under laser irradiation of the composition.Materials and Methods. Metal physical studies in the work were carried out on samples of non-ferrous alloys of the Cu–Zn system with a chrome electrochemical coating with a thickness of 20 μm. The “copper substrate — chrome coating” composition was irradiated at a Kvant-16 installation with a radiation power density of 70–250 MW/m2. Metallographic structural analysis, scanning probe microscopy, and durometric studies were used in the work.Results. It has been calculated that the dynamic and thermal stresses arising in the laser-irradiated compositions “chrome coating — copper substrate” were about 320 MPa. Metal physical studies revealed that, in extreme thermal deformation conditions of laser treatment, the effect of contact melting was manifested at the boundary of the coating with the copper base. Dynamic recrystallization occurred in the surface layers of the irradiated L62 copper alloy, resulting in the formation of grains with a size of 4.5–5.0 μm on the surface of the alloy with an initial grain size of 25 μm.Discussion and Conclusion. It has been found that the adhesion strength of a chrome coating to a copper alloy substrate increased laser irradiation at a radiation power density of 150 MW/m2. This was due to the formation of a transition region 2–4 μm deep in the contact zone with a structure consisting of sections of mutually insoluble solid solutions based on chromium and copper. Based on the analysis of the copper —chromium state diagram and the model of the temperature field under laser irradiation of the chromium coating, it was suggested that contact melting occurred in the transition zone from the coating to the copper substrate. It was shown that thermostrictive stresses, the calculated quantitative values of which were about 320 MPa, had an initiating effect on the observed processes of structure formation in the laser irradiation zones. It was found that such a level of stresses arising in copper alloys under laser irradiation was sufficient for plastic deformation and dynamic recrystallization of the metal and contributed to the formation of a fine-grained structure (4.5–5.0 μm) with an initial grain size of 25 μm. An analysis of the results of studies of irradiated compositions "coating — copper substrate" allowed us to conclude that they expanded the technological capabilities of the laser method of hardening materials and ensure guaranteed high performance of irradiated products with coatings

CORRESPONDENCE OF NUMERICAL MODELS OF LANDSLIDE-PRONE SLOPE TO PHYSICAL OBJECTS OF RESEARCH

Purpose. The purpose of this work is to substantiate the adequacy of numerical models to real physical objects, which significantly depends on how precisely the physical and mechanical characteristics of the soil massif are determined. This especially applies to the determination of critical geometric parameters of slopes. Methodology. Generalization of well-known research in geomechanics and geotechnics, which used an approach to determine the main mechanical characteristics of the soil massif based on the analysis of the deformed state, including critical, real objects, and subsequent back-calculations. Findings. According to the methodology in accordance with the specified approach, all objects under investigation, regardless of their final purpose, are classified according to a justified classification feature. For each class, the following basic real objects are selected, on which irreversible changes in the deformation state have occurred. If the geological structure, hydrogeology of the rock massif, external influences, as well as the geometric parameters of such a destructive process, which is a landslide, are known, then through reverse calculations it is possible to find such averaged physical and mechanical characteristics, the use of which for the appropriate class of selected objects will allow to build and investigate an adequate geomechanical model. Originality. A methodical approach to the determination of physical and mechanical characteristics by their selection, using cases of manifestations of the stress-strain state of pre-classified real objects, is proposed. Practical value. Determining the critical conditions of natural slopes and artificial slopes based on the assessment of the physical and mechanical characteristics of the soil massif as a whole by means of reverse calculations will allow to safely design the construction of buildings and structures on the slopes and ensure the reliable operation of open pit mining operations.

Deformation pseudo-twinning of the L21-ordered intermetallic superlattice

Ordered intermetallic materials are promising candidates for applications in extreme environments due to the strong localized bonding schemes that stabilize the structures against degradation. Here, we investigate the propensity for deformation twinning modes in the L21-ordered MnCu2Al intermetallic by inducing a state of severe plastic deformation. Post-mortem microstructural analysis reveals the presence of meso-scale deformation twins accompanied by a high degree of nano-scale crystalline heterogeneity. The orientation relationship between the parent and twin structures is consistent with activation of the 〈111〉{112} deformation twinning mode. Ab initio generalized stacking fault energy curve calculations corresponding to 〈111〉{112} twinning shear suggest that the magnitude of the twinning partial is 14〈111〉{112} and results in the local formation of a metastable orthorhombic phase within the pseudo-twin. This work highlights the discrepancy between the deformation modes of ordered/disordered structures and promotes an increased awareness for the role that long-range chemical order plays in determining deformation modes.

Influence of AlCoCrFeNiCuSn HEA reinforcement particles on the plastic flow behaviour of the friction stir processed composite material under constrained confined deformation conditions

In the present investigation, an AlCoCrFeNiCuSn high entropy alloy (HEA) reinforced (with 2.5, 5, 7.5 weight percentage (wt.%)) AA7050-based metal matrix composite has been developed by utilising the friction-stir processing (FSP) technique. Further, the representative volume element (RVE) based finite element analysis (FEA) model and macro-mechanical static indentation FEA model have been developed to analyze the plastic deformation of developed composite material under constrained confined deformation conditions at a load range of 4.90 to 49.03 kN. The microstructural investigation confirms the fair distribution of AlCoCrFeNiCuSn HEA particles in the AA7050 matrix. The micro-mechanical RVE-based FEA model and macro-mechanical static indentation FEA model were successfully validated with experimental and analytical models (ECM and FPM) with less than 5% percentage difference. The yield strength of matrix material was increased with 6.51%, 10.47%, and 15.19% by increasing the AlCoCrFeNiCuSn HEA reinforcement particle with 2.5wt.%, 5wt.%, and 7.5wt.% respectively. Further, the tensile strength of matrix material was increased with 1.88%, 3.93%, and 10.49% by increasing the AlCoCrFeNiCuSn HEA reinforcement particle with 2.5wt.%, 5wt.%, and 7.5wt.% respectively. Additionally, Composition 1 (AA7050/2.5wt.% AlCoCrFeNiCuSn HEA), composition 2 (AA7050/5wt.% AlCoCrFeNiCuSn HEA) and composition 3 (AA7050/7.5wt.% AlCoCrFeNiCuSn HEA) show 7.39%, 11.91% and 22.16% more Meyer’s hardness than matrix material.

The concept of fractured rock-mass modeling using DFN-based statistical volume elements

The overall mechanical response of a fractured rock mass is, to a large extent, affected by naturally occurring fractures that exhibit sizes from millimeters to kilometers. Thus, in analysis of underground structures, such as tunnels, it is required that the fractures’ influence on the stress and deformation state in the vicinity of the structure is taken into account. In the present work, we examine the applicability of the statistical volume element (SVE) approach to determining the apparent stiffness tensor of an equivalent continuum representation of the fractured rock, which is then used in the framework of the finite element method. The equivalent continuum properties are determined by volume-averaging the effect of individual fractures that intersect the SVE, while the fractures are represented using the “parallel plate model”. Stochastically generated discrete fracture networks are used to represent the fractures’ geometry. Presently, we solve the problem linearly for an incremental change of the stress state. An application of the concept is demonstrated on simulation of tunnel excavation.

Strength and plasticity coordination improvement mechanism in network structure TiBw/TA15 composite via multi-DOF forming

TiBw/TA15 composite with network TiB whisker (TiBw) reinforcement architecture, exhibits high strength but limited plasticity, presenting a significant challenge in enhancing the plasticity of TiBw/TA15 composites. In the current work, strength and plasticity coordination improvement of TiBw/TA15 composite is achieved through the application of multi-degrees of freedom forming (multi-DOF forming) technology. The α phase spheroidization behaviour and strength-plasticity coordination improvement mechanisms are investigated. The results elucidate that increasing deformation amount through multi-DOF forming leads to more pronounced α phase spheroidization and refinement. This effect is attributed to the generation of substantial strain along the deformation path, particularly in the regions where hard TiBw particles rotate (i.e., the tips of TiBw). Additionally, the impediment of dislocation movement by TiBw causes dislocations to accumulate along these rotation regions via single slip and cross slip mechanisms, thereby accelerating the α phase spheroidization process. Furthermore, with increasing deformation amount, the strength and plasticity are coordinately improved. The tensile strength and elongation increase linearly from 972 MPa to 1239 MPa (increased by 27.5 %) and from 5.6 % to 7.9 % (increased by 41.1 %) as the deformation condition advanced from the sintered state to the 40 % deformation condition, respectively. Improved plasticity can be attributed to the refinement of grains and TiBw, promoting more uniform plastic deformation and reducing stress concentrations during tensile testing. The strengthening mechanisms encompass load transfer strengthening facilitated by TiBw, grain refinement strengthening and dislocation pinning effect caused by TiBw.

Mode shape area difference method for sparse damage detection in beam‐like structures

AbstractThis article develops the mode shape area difference (MSAD) method for detecting sparse damage in beam‐like structures under serviceability conditions. MSAD enhances the static deformation area difference (DAD) damage detection method by extending its application to the modal domain. MSAD leverages the sensitivity of mode shapes to the damage, enabling damage detection and localization through the quantification of area differences between functions of modal displacements and their derivatives. To test the applicability of the method to real modal data that is affected by measurement noise resulting in different accuracies on which the modal displacements are estimated, method is evaluated under different levels of artificial noise added to the theoretical mode shapes derived from numerical model of a simply supported reinforced concrete beam. The noise level is defined by a maximum noise amplitude representing the maximal permutation in each component of normalized mode shape. Additionally, the threshold value of noise level from within the reliable estimation of damage based on MSAD method is determined. It is confirmed that MSAD method requires mode shapes with exceptionally low noise levels and demands precise estimation of all mode shape components, thereby reducing its applicability to real experimental data.

Machine learning-Assisted spiral fiber Bragg Grating-Based flexible dual-parameter sensing

The ability of flexible sensors to bend or fold freely offers great advantages in sensing ability and adaptability to harsh environments. Moreover, compared with typical electrical effect based flexible sensors, optical based fiber Bragg grating (FBG) flexible sensors offer much greater ease of networking and resistance to electromagnetic interference, making them suitable for distributed multi-point strain measurements in complex environments. In this paper, two FBGs with no overlapping reflective spectra are shallowly embedded in the surface layer of a flexible thin-cylinder substrate to form a dual-parameter flexible strain sensor. However, it is crucial for the changes in direction and curvature parameters of FBG strain sensors under deformation to be accurately understood to characterize the current deformation state of the flexible sensor. Moreover, conventional peak tracking demodulation methods often fail to account for distortion in the reflected spectrum of a spiral FBG under stress. Hence, a multi-output convolutional neural network learning model is constructed to simultaneously identify the bending direction and curvature radius of the flexible sensor using machine learning methods. Experimental results show that the flexible dual-parameter FBG sensor has precisely recognize angles to within 2° across a 360° range, with a curvature recognition accuracy of 99.1%, offering precision sensing performance suitable for highly demanding application scenarios such as bionic robots and flexible medical devices.