Strain Concentration Research Articles

Effect of solid solution and vacancies on the mechanical properties of Cu(Al)/Al2Cu/(Cu)Al layered gradient heterostructures

We used molecular dynamics simulation (MD) methods to investigate the effect of diffused solutes and vacancies on the tensile deformation behavior of nano-polycrystalline Cu(Al)/Al2Cu/(Cu)Al layered heterostructures. Simulation results show that the Cu(Al)/Al2Cu/(Cu)Al layered heterostructure with Al-20% Cu has the highest ultimate strength and fracture strain. On this basis, gradient Cu solute in the matrix Al improves the synergistic tensile deformation behavior among the components of the nano-polycrystalline Cu(Al)/Al2Cu/(Cu)Al layered gradient heterostructure. More importantly, gradient Cu solute contributes to the localized strain transfer between component layers, ultimately increasing the fracture strain and ultimate strength. In addition, deformation behavior between polycrystalline Cu(Al)/Al2Cu/(Cu)Al layered gradient heterostructure fails at low tensile strains because the vacancies cause strain concentration of polycrystalline Cu near the interface and weaken strain delocalization in polycrystalline Al.

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds (DMWs) involving nickel-based weld metal (WM) and ferritic heat resistant steel base metal (BM) in power plants, there must be an interface between WM and BM, and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure. In this study, a new form of WM/BM interface form, namely double Y-type interface was designed for the DMWs. Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests, and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization. By applying double Y-type interface instead of conventional I-type interface, failure location of DMW could be shifted from the WM/ferritic heat-affected zone (HAZ) interface into the ferritic HAZ or even the ferritic BM, and the failure mode change improved the creep life of DMW. The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation, stress and strain concentrations, and oxide notch on the WM/HAZ interface. The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ, which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries. The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface, preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking. It is a novel scheme to prolong creep life and enhance reliability of DMW, by means of optimizing the interface form, decoupling the damage factors from WM/HAZ interface, and then changing the failure mechanism and shifting the failure location.

Powder bed fusion repair of titanium with surface damage: Molecular dynamics study on microstructure and mechanical properties

Additive manufacturing has been emerging as a highly efficient method that minimizes the consumption of virgin materials and energy to rapidly repair the damaged parts and potentially recover the original performance. Here, the microstructures and mechanical properties of polycrystalline titanium (Ti) with surface damage after powder bed fusion (PBF) repair and post-polishing treatment are investigated by molecular dynamics simulations. It is found that during PBF repair of the surface damage by melting Ti nanoparticles, grain boundaries (GBs) in polycrystalline Ti are more susceptible to damage from temperature elevation than the grain interiors. During the solidification process, grains grow in the form of columnar crystals. After PBF repair and post-polishing treatment, the yield strength of damaged samples is recovered to 96.8% of that of perfect ones. This restoration can be attributed to the increased capacity of carrying dislocations due to that the GB directional growth generates dislocation walls after PBF repair. More importantly, the flow stress exceeds that of the perfect sample due to the increase in stacking faults and the appearance of twins after PBF repair, which enhance the resistance of dislocation motion. The fatigue performance of the damaged samples processed by combinatorial PBF repair and post-polishing treatment is found to surpass that of perfect samples. This is attributed to that the elimination of rough surface and the reduction of intragranular dislocations avoid dislocation entanglement that otherwise results in strain concentration, and also prevent the premature occurrence of twins and the rapid increase in stacking faults during the cyclic loading, thus retarding the nucleation of intergranular cracks. Our molecular dynamics simulation results could help shed light on the atomic mechanism of microstructure evolution during PBF repair and mechanical performance after PBF repair.

Simultaneous enhancement of mechanical and functional properties by heat-treatment in CuAlNi shape memory alloys fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is a promising manufacturing method for fabricating Cu-based shape memory alloys (SMAs), but further performance improvement is needed to ensure service stability and broaden the engineering applications. To achieve simultaneous enhancement of mechanical and functional properties of CuAlNi ternary SMAs fabricated via the LPBF process, this study conducts isochronous and isothermal quenching treatments to tailor the microstructure. The heat-treated specimens with a high quenching temperature and long soaking time exhibited high ultimate tensile strength of 696 ± 10 MPa, large ductility of 8.9 ± 0.2%, and excellent recoverable strain under 2% pre-strain with a shape recovery rate of 100%, which were considerably superior than those of as-built specimens (ultimate tensile strength of 612 ± 10 MPa, elongation of 2.6 ± 0.1%, and 1.26% recoverable strain). This is attributed to the element homogenization during heat treatment, release of residual stress, and coordinated martensite network boundary. However, no significant strain platform of martensite reorientation or detwinning was found in the tensile deformation of the as-built and heat-treated samples, due to localized strain concentration in the parent grain. The microstructural evolution under different quenching treatments and the underlying mechanisms for the improvement of mechanical and functional properties are discussed in detail. This work not only reveals the unique functional response of LPBF fabricated Cu-based SMAs, but also provides a simple and effective method to improve their performance.

The Simulation Of Drop-Weight Impact Test On Ramie-Eglass Hybrid Fiber Composite For Jaloe Kayoh Wall Material

The purpose of this study is to simulate drop-weight impact tests on hybrid fibre composites made of ramie and Eglass, which are used to make the traditional Acehnese boat wall material for jaloe kayoh. Using composites of ramie-Eglass fiber hybrid in the construction of jaloe kayoh wall material will significantly enhance the strength, durability, and sustainability of traditional Acehnese boats. The simulation was carried out using the finite element method approach using the Abaqus software. Three distinct laminate layer configurations—three layers (GRG), five layers (GRGRG), and six layers (GRGGRG)—with alternating Eglass and ramie fibres make up the test specimens. The ends of the specimen are set with fixed support to ensure boundary conditions, which limit all active structural degrees of freedom on all sides of the specimen. According to simulation results, the specimen with six laminate layers, measuring 12.498 mm, had the largest displacement. The specimen with six laminate layers has the highest stress concentration, measured at 560.6 MPa, while the specimen with three layers has the highest strain concentration, measured at 0.023. Its indicating that the lamina variation can influence the structural performance of the jaloe kayoh material. This research contributes to understanding the potential of ramie-Eglass hybrid fiber composites to enhance the safety and durability of traditional vessels such as jaloe kayoh. The implications of the results can serve as a foundation for the development of superior structural materials in the future.

Investigation into the Three-Stage Formation of Micro-Channels with Ultra-Thin Titanium Sheets Used for Proton-Exchange Membrane Fuel Cell Bipolar Plates.

Titanium has a low density and high corrosion resistance. In order to achieve the goal of a lightweight material, and to extend the normal working hour of proton-exchange membrane fuel cells (PEMFCs), ultra-thin titanium plates were chosen to manufacture the key components-bipolar plates (BPs). For the purpose of overcoming the challenges of manufacturing with a large depth to width ratio, a multi-stage formation process was established with characteristics such as high efficiency and a lower price. In this study, the process parameters were examined through an experimental approach. The outcomes show that the channel formed by multistage forming is deeper than that formed by single-stage forming under the same displacement conditions. To achieve greater flow depths, it is recommended to increase the displacements as much as possible during both the first- and second-stage forming processes. The implementation of three-stage forming can effectively reduce the maximum thinning rates within flow channels while improving the overall deformation uniformity. This method deviates from traditional one-stage loading processes by adopting multi-stage loading instead. By employing appropriate mold designs, material deformation and flow can be enhanced throughout gradual loading processes, thereby preventing strain concentration and enhancing the ultimate formation height accuracy within micro-flow channels. Consequently, the proposed three-stage forming process proves highly appropriate for the mass production of BPs utilizing titanium plates.

Investigation of active slip modes via in-grain misorientation axis and strain compatibility of TA2 alloy during in-situ tensile deformation

Slip is an important mechanism to coordinate the deformation in metal materials. Grain boundary can hinder slip transfer, thus lead to strain concentration. This work focus on the law of slip coordination deformation, texture evolution and strain compatibility under different strains. Based on the electron backscattered diffraction (EBSD) technique, the in-situ tensile tests of TA2 alloy were carried out at strain of 2 %, 4 % and 6 %, the activate law of slip under different strains was analyzed by the in-grain misorientation axes (IGMA) method and was verified by Schmid factor (SF). The relationship between grain orientation and strain compatibility at grain boundaries was discussed by calculating the geometric compatibility factor (m′). The results show that the multi-system slip coordination deformation at initial deformation, and the prismatic slip dominates the deformation as the increase of strain. The texture is preferentially distributed in the transverse direction (TD) as the deformation proceeds. The strain concentration is mainly related to the lack of effective plastic deformation mechanism to complete strain transfer at grain boundaries.

Streptomyces enissocaesilis L-82 has broad-spectrum antibacterial activity and promotes growth for Carassius auratus.

Aeromonas is the main pathogen causing bacterial diseases in fish. The disadvantages of chemical drugs to control fish diseases have been highlighted, and it is urgent to find an eco-friendly control method. In this study, an actinomycete strain with antibacterial activity against fish pathogenic bacteria was screened from soil samples. Combined with morphological characteristics, physiological and biochemical characteristics, and gyrB gene and whole genome comparison analysis, it was identified as a new strain of Streptomyces enissocaesilis, named Streptomyces enissocaesilis L-82. The strain has broad-spectrum antibacterial activity against fish pathogens. A substance with a mass-to-charge ratio of 227.20 [M + H] + was isolated and purified by high-performance liquid chromatography and mass spectrometry. It was presumed to be a derivative of 5-dimethylallylindole-3-acetonitrile. The strain is safe and non-toxic to crucian carp, and can stably colonize crucian carp and inhibit the proliferation of A. hydrophila. After feeding the feed containing 1 × 108CFU/mL strain concentration, the weight growth rate and specific growth rate of crucian carp increased, the activity of ACP and SOD in serum increased, and the survival rate of crucian carp increased after challenge. Genome-wide analysis showed that the strain had strong ability to metabolize and tolerate extreme environments. And has a strong potential for disease resistance. Therefore, the strain is expected to be developed as a feed additive for fish farming. KEY POINTS: • The new Streptomyces enissocaesilis L-82 has a broad spectrum and stable antibacterial activity and meets the safety standards of feed additives. • Strain L-82 can colonize crucian carp, improve the growth, antioxidant, and immune performance of the host, and improve the survival rate after being infected with A. hydrophila. • Genome-wide analysis suggests that the strain has great disease resistance potential and is expected to be developed as a feed additive for fish culture.

Analysis of Strain Distribution in Common Clinical Designs of Posterior Implant-Supported Fixed Partial Restorations: Comparison between Six Configurations.

The configuration of implant-supported prostheses is considered to influence the magnitude of stress concentrations, affecting their survival rate. The purpose of this study is to determine, through strain gauge measurements during load application, the dispersion and magnitude of strain concentrations in different implant-supported prosthesis designs. All designs matched those commonly used in posterior partially edentulous states. Three implants were inserted into an epoxy resin model (PLM-4B Vishay Measurements Group Inc., Raleigh, NC, USA), allowing for the delivery of three- and four-unit crowns in different cemented configurations. Loads were applied at vertical and oblique directions over the cast crowns in six different configurations representing various posterior partially edentulous restorations. The readings from the strain gauges adhered to the implant necks' presented data on implant strain. Prostheses including cantilevers showed the highest strain among the three-unit prostheses within the prosthetic complex, and three single units showed the least (8133 µs vs. 201 µs, respectively). Angulated load application also had a role in amplifying the strains recorded, resulting in total strains of between 3.5 and 20 times higher than during vertical loading in all configurations. It can be concluded that the configuration of implant-fixed partial prosthesis changes the loads engaging the restoration, the implant, and, probably, the supporting bone.

Research on strength and toughness matching of 1.3GPa ultralow temperature resistant bulb flat steel

In this study, an ultralow temperature resistant bulb flat steel with ultra-high strength and good toughness is prepared to meet the application requirements of hull structural steel for polar ships and large ships. The bulb flat steel with a yield strength of 1292 MPa, elongation of 18.5 % and an impact energy of 53 J at − 196 °C is obtained by quenching and tempering process. In order to reveal the tempering response and strengthening mechanism during the quenching and tempering process of bulb flat steel, multi-scale characterization is carried out to explore the microstructural evolution and nano-precipitation behavior of the ultralow temperature bulb flat steel under different tempering processes. The results indicate that the preferential precipitation of (V, Nb)(C, N) causes dislocation multiplication, and the higher dislocation density in the matrix provides more nucleation sites for M2C. The slower diffusion rate of Mo effectively suppresses the rapid coarsening of M2C, which keep a good coherent relationship between the M2C and the α-Fe matrix. Strain concentration is avoided by synergizing the (V, Nb)(C, N) precipitation and the M2C precipitation of the coherent lattice, thus enabling the ultralow temperature resistant bulb flat steel to maintain ultra-high strength with good plasticity and toughness.

Study on the microstructure and creep fracture behavior of 22Cr 15Ni steel welded joint after aging at 650 °C

It has been carefully investigated that microstructure and creep fracture behavior of Fe–22Cr–15Ni (SP2215) steel welded joints on aging at 650 °C. The extrapolated stresses for welded joint after aging for 0 h (Aging-0h WJ) and 2012 h (Aging-2012h WJ) at 105 h are 105.2 and 91.7 MPa, respectively. The fracture location for Aging-0h WJ and Aging-2012h WJ was respectively heat affected zone (HAZ) and weld metal (WM). HAZ grain size of Aging-0h WJ was 53–88 μm because of thermal cycling. After 2012h aging, HAZ grain size did not change, but grain boundaries were roughened and M23C6 has been found on grain boundaries. Welding and aging treatment did not cause element migration near the fusion line. However, the decrease in Nb elements on the weld side resulted in a decrease in the amount of NbC, which delayed creep damage. The 2012h aging had no significant effect on the hardness difference between HAZ and WM near fusion line, indicating that the transfer of creep fracture position was caused by microstructure changes. The cluster-like NbC formed in WM of Aging-2012h WJ, which not only reduced Nb solid strengthening effect, but also caused local strain concentration. Moreover, in WM of Aging-2012h WJ, the orientation and hardness differences between large-sized (Nb, Ti) C and matrix, and M23C6 on the grain boundary jointly reduced the WM creep performance.

A size-dependent imperfect interface model for adhesively bonded joints considering strain gradient elasticity

As the size of a layered assembly is reduced, the adhesive layer thickness correspondingly decreases from macro to micro scale. The influence of micro-scale adhesive layers becomes more pronounced, significantly changing the overall performance of the composite structure. This work proposes an original imperfect interface model simulating the behavior of a thin strain gradient elastic adhesive, embedded between two strain gradient elastic bodies, through the asymptotic methods. The intermediate layer is assumed to be mechanically compliant. The contact laws, expressed in terms of the jumps and means values of the displacements, normal derivatives of the displacements, stresses, and double-stresses, represent a formal generalization of the soft elastic interface conditions. Two simple benchmark equilibrium problems (a three-layer composite micro-bar subjected to an axial load and a torsional moment) are developed to analytically/numerically assess the asymptotic model. Size effects and non-local phenomena, due to high strain concentrations at the edges, are highlighted. The example proves the efficiency of the proposed approach in designing micro-scale layered devices.

Qualitative investigations into floodways under extreme flood loading

AbstractThe Australian use of the term floodway refers to a trafficable transverse structure designed to facilitate the safe crossing of watercourses. Floodways are also commonly referred to as fords and causeways. This research explores areas of focus through experimental, numerical and survey methods to improve floodway resilience with regard to flood risk management. The industry‐based survey provides a dataset relating to user experiences, deduces the likeliness of floodways to sustain damage, defines several key focus areas, and reveals that the current risk levels are primarily managed without significant investigation into design. A floodway experimental and numerical simulation program was developed to investigate the lateral forces induced through debris impact using scaled models in a soil box and finite element analysis. Qualitatively, crack propagation and displacement correlated closely with the strain concentrations and displacements in the numerical simulation, with failure attributed to tensile strength being exceeded, followed by plastic strain development within the soil elements. It was concluded through this research that floodway failure during flood is complex and can be attributed to several different failure modes including concrete failure, yielding of adjoining soil material, and hydraulically via scour.

Effects of the Injection Material and Resin Layer on the Mechanical Properties of Carbon Fiber-Reinforced Thermoplastic (CFRTP) Press and Injection Hybrid Molded Parts

In the press and injection hybrid molded parts of fiber-reinforced thermoplastics (FRTPs), failure at the interface between the surface material (the outer shell) and the ribs (the injection part) or that at the injection part has become an issue. Adding a resin layer to the rib roots at the same time that the ribs are molded through injection has been proposed, which may increase the mechanical properties and reduce the material cost. To prevent failure at the injection part, the use of fiber-reinforced resin as an injection material has been suggested. This approach contributes to a higher bond strength by lowering the molding shrinkage rate. In this study, the hat-shaped parts of carbon fiber-reinforced thermoplastics (CFRTPs) with fiber-reinforced and neat resin layers at the rib root were fabricated through press and injection hybrid molding, and their mechanical properties were evaluated through three-point bending tests. The effects of the resin layer at the rib root and the existence or nonexistence of fiber reinforcement on the mechanical properties, as well as the relationship between the material cost and the mechanical properties, were clarified through an experiment and FEM analysis. The bond strength was also evaluated through tensile tests that were undertaken at the rib root. Molded parts with neat PA6 and glass fiber-reinforced PA6 resin layers at the rib roots showed higher bond strength than those without resin layers. In a three-point bending test of a CFRTP hat-shaped part with a resin layer at the rib roots, the use of a 1 mm thick CFRTP laminate for the outer shell and glass fiber-reinforced PA6 resin as the injection material showed the same stiffness as a part that used a 2 mm thick CFRTP laminate for the outer shell. FEM analysis showed that the resin layer prevented the concentration of strain at the rib roots, and the model that used a 1 mm thick CFRTP laminate for the outer shell and glass fiber-reinforced PA6 resin as the injection material showed the best specific stiffness in this study. By adding a resin layer to the rib roots, the fabrication of molded parts with excellent specific stiffness was enabled at a small increase in cost.

Local strain evolution near α/β interface in TC11 titanium alloy under electroshocking treatment

The evolution of local strain at α/β interface in TC11 titanium alloy under electroshocking treatment (EST) was investigated and quantified by Kernel average misorientation (KAM) and Geometrical phase analysis (GPA). The KAM results showed that the phenomenon of strain concentration weakened after EST with 0.04 s, and mass of strain in small area formed and distributed evenly after EST with 0.06 s. GPA analysis indicated that the annihilation of dislocation and lattice distortion near interface was the main reason for weakening the strain concentration during phase transition from αs to β after EST with 0.04 s. After EST with 0.06 s, the alternate appearance of severe defect area and the regular area near the interface resulted in the formation of small area strain, and the precipitation of fine αM phase inhibited the growth of strain area, which resulted in the even distribution of strain. This work can demonstrate the effect mechanism of EST on the local strain near the phase interface of titanium alloys and provide a theoretical basis for the microstructure manipulation of titanium alloys under EST.

The Effect of Multi-Step Tempering and Partition Heat Treatment on 25Cr2Ni3MoV Steel's Cryogenic Strength Properties.

In this study, the refinement of two microstructures was controlled in medium carbon 25Cr2Ni3MoV steel via multi-step tempering and partition (MTP) to achieve high cryogenic strength-ductility combinations. Microstructure evolution, the distribution of stress concentration, and microcrack formation and propagation during cryogenic Charpy impact testing were investigated. Compared with their performance in the quenching and tempering states (QT), the MTP steels showed a significant improvement in yield strength (1300 MPa), total elongation (25%), and impact toughness (>25 J) at liquid nitrogen temperature (LNT). The strengthening contributions mainly originated from the high dislocation density and refinement cementite (size: 70 nm) in the martensite lath (width: 1.5 μm) introduced by refined reversed austenite and its latter decomposition. The instrumented Charpy impact results indicated that cracks nucleated in the primary austenite grain (PAG) boundary for two steels due to the strain concentration band preferring to appear near PAGs, while cracks in the QT and MTP samples propagated along the PAGs and high-angle grain boundary (HAGB), respectively. The crystallized plasticity finite element simulation revealed that the PAG boundary with cementite precipitates of large size (>200 nm) was less able to dissipate crack propagation energy than the HAGBs by continuously forming a high strain concentration area, thus leading to the low-impact toughness of the QT steel.

Effect of long-term aging on the microstructure evolution and fracture mechanism of 9% Cr steels

The fracture toughness of pressure pipe steels is vital for their design and safe operation. Understanding the deterioration of the fracture toughness and the corresponding fracture mechanisms is instructive and meaningful for material selection and development. The elastic–plastic fracture toughness of 9% Cr steels aged at 873 K and 923 K from the initial state to 20000 h was investigated at ambient temperature and 873 K. The deterioration of the fracture toughness and the corresponding fracture mechanisms are discussed in detail. For 9% Cr steels, voids mainly initiated from primary inclusions such as silicides, sulfides, alumina and manganides in as-received state, while voids initiated from both primary inclusions and secondary particles such as the Laves phase after long-term aging. These voids grew and coalesced with neighboring voids and crack tips subsequently until ultimately fracture. After aging at 873 K, the fracture toughness values tested at 873 K decreased from the initial state to 3000 h and then increased to 10000 h. The peculiar deterioration of the fracture properties after 3000 h of aging at 873 K can be attributed to the high number density of Laves phase particles in the steels. It was found that the densely distributed hard Laves phase particles induced strain concentration at the interface between the Laves phase and the matrix under plane-strain tension condition and promoted nucleation of voids. It was suggested that the spatial distribution of the Laves phase played a significant role on the void formation. 9% Cr steels with a denser distribution of Laves phases brings about voids with shorter interspaces, which are more susceptible to coalesce into crack tip, resulting in lower fracture resistance. After aging at 923 K from 10000 h to 20000 h, the number density, size and volume fraction of precipitates, block size, misorientation angle and dislocation density remained almost constant. The slight increase in the fracture toughness from 10000 h to 20000 h can be mainly ascribed to the coarsening of the martensite lath in this stage.

Improvement of shape recovery by controlling the microstructure and mechanical properties in a thermomechanically-treated Fe-based alloy

In this research, the effects of thermomechanical treatment including heavy cold rolling and post-deformation annealing on the improvement of shape recovery in an Fe–9Ni–7Mn (at.%) martensitic alloy were investigated. Experimental results showed that the 80 % cold rolling produced a little fraction of strain-induced austenite phase in the martensitic matrix due to the strain concentration in the microstructure and the temperature rise under deformation. During post-deformation annealing at 590 °C in a dual phase (α+γ) region, a greater fraction of the austenite was introduced in the martensitic matrix such that its amount first increased by increasing the annealing time to 1.8 ks and then decreased at a more time of reversion. The microstructural evolution revealed that the austenite reversion under post-deformation annealing initially occurred by a shear nature at the early steps of reversion and then continued by diffusion. Tensile testing represented a good mixture of a relatively high ultimate tensile strength of ∼780 MPa and proper ductility of ∼8.5 % in the post-deformation annealed (PDA) sample for 0.9 ks. In addition, the shape memory properties were examined under the conditions of cold rolling and post-deformation annealing. The results showed a maximum shape recovery rate of ∼23 % for the cold rolled specimen which increased to ∼50 % after post-deformation annealing for 0.9 ks. The presence of a relatively high amount of retained austenite with proper stability and strength in the microstructure of the PDA sample for 0.9 ks was the reason for achieving the highest value of shape recovery.

Deformation mechanisms of additively manufactured TiNbTaZrMo refractory high-entropy alloy: The role of cellular structure

Additive manufacturing of refractory high-entropy alloys (RHEA) is challenging, limited information is available on the microstructure and mechanical properties of as-built RHEA. In this work, Ti1.5Nb1Ta0.5Zr1Mo0.5 (TNTZM; at%) alloy is successfully fabricated by additive manufacturing. It is characterized by distinctive cellular structures, exhibited outstanding plasticity of 50 %, and a yield strength of 904 MPa. The cellular structure hindered dislocations transfer between adjacent cells and limited dislocation slip inside the cells, thereby significantly improving strength and uniform deformation. Moreover, the cellular structure facilitated the redistribution of dislocations during later deformation to avoid strain concentrations within the grains. The regulated dislocation initiation on demand during the evolution of the cellular structure at the different deformation stages is proposed. This work provides new insights improving the mechanical properties of additive manufactured RHEA.

Bending and Stretching‐Insensitive, Crosstalk‐Free, Flexible Pressure Sensor Arrays for Human‐Machine Interactions

AbstractAccurate data acquisition from flexible sensors placed on deformable 3D freeform surfaces is of critical importance for many applications, such as wearable electronics, human‐machine interfaces, and soft robotics. However, the mechanical coupling between the sensor and the deformable subject surface to bending and stretching deformations can significantly reduce the accuracy of the acquired data. This study combines a polyimide (PI) micropore isolation layer (PIL) and serpentine electrodes with a flexible piezoresistive sensor to mitigate the issue of mechanical coupling. As a mechanical buffer to distribute the external pressure and reduce the strain concentration, the PIL can avoid the bending interference for bending curvature up to 256 m−1, while maintaining a high sensitivity of S > 21.5 kPa−1. The serpentine electrode design further allows the sensor to reliably acquire data in the presence of stretching up to 45% without cross‐talk. The versatility of the developed sensor is demonstrated in several human‐machine interaction scenarios, including gesture recognition and motion detection. The design strategies on materials and structures from this study can also be applied for the development of other flexible sensors with high sensitivity and low deformation interference to avoid the mechanical coupling between the sensor and the deformable surface.