High Compressive Strain Research Articles

Experimental study on flexural behaviour of reinforced reactive powder concrete pole

To investigate the feasibility of using reactive powder concrete (RPC), with high compressive strength, compression and tensile strain, for concrete poles, and to study differences between RPC poles and normal concrete (NC) poles, four RPC poles and three NC poles were designed and manufactured with the same specifications. The failure mode, crack distribution, cross-section strain distribution, deformation performance, cracking moment and flexural strength of the RPC and NC poles were analysed through flexural load tests. The results indicated that the maximum crack width of RPC poles under all levels of loads was significantly smaller than that of NC poles. The cracking moment of RPC poles increases by 27.3%–37.0%, and the flexural strength of the RPC pole increased by 18.7–45.4% compared with those of NC pole. The calculation method for the cracking moment of RPC poles considering the influence of steel fibres, and the calculation formula for the flexural capacity of RPC poles considering the contribution of the tensile force of the RPC in the tensile zone are developed.

Influence of the PFNA screw position on the risk of cut-out in an unstable intertrochanteric fracture: a computational analysis

The position of the lag screw in the femoral head is a key factor to cut-out, the most reported complication in the internal fixation of intertrochanteric fractures. Considering that the best position for the lag screw remains controversial, the aim of this study was to evaluate the influence of different lag screw positions on the risk of cut-out of an unstable intertrochanteric fracture fixed with a Proximal Femoral Nail Anti-Rotation (PFNA) implant. The relationship between cut-out and the tip-apex distance (TAD) or the calcar referenced tip-apex distance (CalTAD) was also investigated.Finite element models of one male and one female femur treated with a PFNA implant were developed considering the lag screw positioned centrally and inferiorly on the anteroposterior view, and for each of these, the screw tip at 4 discrete positions along its longitudinal axis. All 8 positions simulated for each femur considered the lag screw in a centre position on the lateral view. The risk of cut-out was evaluated for two loading conditions assuming it is related with high compressive strains.The bone region at the fracture line, near the tip of the missing medial fragment, was always the most concerning regarding high compressive strains. The inferior positioning of the lag screw reduced the volume of bone susceptible to yielding compared to the centre positioning. The deep placement of the screw tip improved the outcome for both centre and inferior positions.The results suggested the inferior and deep placement of the screw to be the best position to reduce the risk of cut-out. The volume of bone susceptible to yielding was found not to be correlated to TAD or CalTAD, suggesting that further investigation is necessary to identify other, more reliable, predictors of cut-out.

Spatial characteristics of nickel-titanium shape memory alloy fabricated by continuous directed energy deposition

Additive manufacturing has been adopted to process nickel‑titanium shape memory alloys due to its advantages of flexibility and minimal defects. The current layer-by-layer method is accompanied by a complex temperature history, which is not beneficial to the final characteristics of shape memory alloys. In this study, a continuous directed energy deposition method has been proposed to improve microstructure uniformity. The spatial characterization of nickel‑titanium shape memory alloy fabricated by continuous directed energy deposition is investigated to study the temperature history, phase constituent, microstructure, and mechanical properties. The results indicate that the fabricated specimen has a monotonic temperature history, relatively uniform phase distribution and microstructure morphology, as well as high compressive strength (2982 MPa–3105 MPa) and strain (37.7%–41.1%). The reported method is expected to lay the foundation for spatial control during the printing of functional structures.

Experimental study of flexural behaviour of high strength steel (HSS) ‐ Engineered Cementitious Composites (ECC) composite beam with profiled steel sheeting

AbstractDue to its high compressive strain of at least 0.5%, which is higher than both the yield strain (0.35%) of high strength steel (HSS) and the compressive strain (0.23%) of normal strength concrete (NSC), Engineered Cementitious Composites (ECC) is a material with high potential to replace NSC in HSS composite beam construction. This study reports an experimental investigation on the flexural behaviour of HSS‐ECC composite beam fabricated by using HSS I‐section in conjunction with hybrid polyethylene‐steel fibers (PE‐ST) ECC slab. Shear connection between the HSS I‐section and the top PE‐ST ECC slab was constructed by using normal profiled steel sheeting and headed shear studs. A HSS‐ECC composite beam and a HSS‐NSC composite beam were cast and tested under four‐point bending. The test results revealed that a large area of HSS I‐section in HSS‐ECC composite beam yielded compared to only a small yielded area of which in the HSS‐NSC counterpart despite the fact that both composite beams have identical configuration and silimar mechanical properties. The HSS‐NSC beam underwent longitudinal shear failure while in contrast, the HSS‐ECC beam failed by flexure and exhibited great ductility.

High density of strong yet deformable intermetallic nanorods leads to an excellent room temperature strength-ductility combination in a high entropy alloy

This paper introduces a new microstructural template for high entropy alloys (HEAs), where the face centered cubic (FCC) complex concentrated solid solution is reinforced with a high density of strong, yet deformable, nanorods of an ordered multi-component intermetallic L12 compound. Thermodynamic modeling has been employed to design this HEA with a large L12 volume fraction. Thermo-mechanical processing by isothermal annealing of the conventionally processed bulk cold-rolled alloy directly at precipitation temperatures, has been applied to produce a high density of uniformly distributed L12 nanorods within refined FCC grains, resulting from concomitant recrystallization and discontinuous precipitation processes. The nanorod morphology of the discontinuous L12 product has been established from three-dimensional atom probe tomography. The refined grains result in a complete coverage of the microstructure with discontinuously precipitated intermetallic nanorods. This nanorod strengthened HEA exhibits an exceptionally high room temperature yield strength of ∼1630 MPa, good tensile ductility of ∼15%, and an ultimate tensile strength of ∼1720 MPa. Furthermore, a single L12 phase alloy, melted based on the precipitate composition in the two-phase FCC + L12 HEA, exhibits very high compressive deformability and strain hardenability, unusual for ordered intermetallic compounds. These results open a new strategy for design of fine-grained microstructures strengthened via ordered intermetallic phases, exploiting the beneficial effects of discontinuous precipitation, for achieving very high room temperature tensile strengths while maintaining good ductility.

Octodecane-cellulose nanofiber flexible composites for latent heat storage

While phase change material (PCM)-encapsulated, emulsion-templated monolithic composites are promising for latent heat storage, they are usually rigid, which hinders their wide applications. Here, we report the fabrication of PCM (octodecane, OD)-encapsulated, emulsion-templated monolithic composites with wide-temperature-range flexibility for latent heat storage. The composites were prepared from OD-in-cellulose nanofiber (CNF) suspension emulsions through interfacial reaction and subsequent drying. Composites from freeze drying showed flexibility at temperature over the melting point of the encapsulated OD (30 °C), while composites from heat drying were flexible at temperatures even below the melting point of the encapsulated OD (such as at 20 °C). The wide-temperature-range flexibility could result from the reduced bonded OH groups within CNFs and the presence of voids with nanofibrous walls. The two types of the composites showed controllable external shapes, robust compression and good encapsulation, without fracture at a high compressive strain of 70% and without leakage at a compressive strain below 30%. Moreover, the composites possessed high reproducibility, extremely high heat capacity (up to 250 J.g−1, even slightly higher than that of bulk OD), high reusability and stability, without obvious deterioration in heat capacity after 100 heating–cooling cycles. The feature that combines wide-temperature-range flexibility, mechanical robustness, high heat capacity and good reusability/stability enabled the OD-encapsulated monolithic composites to be excellent candidates for latent heat storage.

Evaluation of test methods and face-sheet thickness effects in damage tolerance assessment of composite sandwich plates

Composite sandwich materials provide high bending performance-to-weight ratios. However, these materials are vulnerable to impact damages which can drastically reduce their load-bearing capability. Presently there is a lack of standardised test methods for impact assessment. This study compares three different test methods for impact assessment; single skin compression after impact (CAI-SS), sandwich compression after impact (CAI-SW) and four-point bending-after-impact (BAI). The CAI-SS test method shows high compressive strength and strain at failure and the tesr is relatively easy to evaluate. For finite size plates with significant impact damage, the CAI-SS test method is recommended for post impact strength assessment. For large sandwich panels with relatively small impact damages the CAI-SW test method could be more relevant since it includes effects of panel asymmetry generated from the impact damage. The BAI test method may be recommended as an alternative to CAI but quite long specimens are required in order to assure compressive failure in the tested face-sheet, making the test both demanding and expensive. On the other hand, lower load levels are required to break the specimens and there is less need for precise machining during specimen manufacturing. A finite element model including progressive damage evolution was used to estimate the post impact strength. The simulations showed generally good agreement with the experiments.

Experimental testing and 3D meso-scale numerical simulations of SCC subjected to high compression strain rates

Experimental and numerical investigations of three types of Self-compacting concrete (SCC) in Split Hopkinson Pressure Bar (SHPB) compression tests are performed. A detailed methodology for correctly and efficiently performing SHPB tests of SCC in the range of 68–236 s−1 is presented. Numerical simulations were performed using the developed 3D meso-scale model with mortar, the Interface transition zone (ITZ) and randomly generated aggregate spheres; these three parts were described using the Johnson-Holmquist (JHC) constitutive model. The results confirmed that the Dynamic increase factor (DIF) obtained from SHPB tests is due to the material’s property and the inertia effect. While lateral inertial confinement is found to be dependent on the strength of the concrete, its contribution is less significant at strain rates beyond 200 s−1. Finally, the DIF decreases as the compressive strength of concrete increases.

Anisotropic Carbon Aerogel from Cellulose Nanofibers Featuring Highly Effective Compression Stress Transfer and Pressure Sensing

Carbon aerogels with excellent compressibility and resilience are attracting considerable attention in broad application prospects for their reversible resilience and resistance to damage from external stress. It is of great interest to explore green and low-cost carbon aerogels from sustainable resources but remains challenging because of the brittleness of carbon blocks. Herein, inspired by the anisotropic architectures in nature, we propose a bottom-up approach for fabricating an anisotropic carbon aerogel with a 3D lamellar structure from cellulose nanofibers. The aligned and continuous lamellar texture with desirable thickness (142 nm) can effectively transfer stress throughout the 3D network and resist the destruction at high compression, and thus, the carbon aerogel exhibits shape recovery from high compression strain and excellent fatigue resistance. The carbon aerogel can withstand extremely high compression strain (95%) for at least 50 cycles or 50,000 cycles at 50% strain with 84% height retention. Moreover, the excellent mechanical performance, stable 3D lamellar architecture, and high conductivity endow the carbon aerogel with rapid current response and high sensitivity in a wide pressure range (0.002-7 kPa). This study introduces the carbon aerogel as an excellent choice for fabricating the 3D tactile sensor to capture various signals of human motions.

Cortical Thickness Adaptive Response to Mechanical Loading Depends on Periosteal Position and Varies Linearly With Loading Magnitude.

The aim of the current study was to quantify the local effect of mechanical loading on cortical bone formation response at the periosteal surface using previously obtained μCT data from a mouse tibia mechanical loading study. A novel image analysis algorithm was developed to quantify local cortical thickness changes (ΔCt.Th) along the periosteal surface due to different peak loads (0N ≤ F ≤ 12N) applied to right-neurectomised mature female C57BL/6 mice. Furthermore, beam analysis was performed to analyse the local strain distribution including regions of tensile, compressive, and low strain magnitudes. Student’s paired t-test showed that ΔCt.Th in the proximal (25%), proximal/middle (37%), and middle (50%) cross-sections (along the z-axis of tibia) is strongly associated with the peak applied loads. These changes are significant in a majority of periosteal positions, in particular those experiencing high compressive or tensile strains. No association between F and ΔCt.Th was found in regions around the neutral axis. For the most distal cross-section (75%), the association of loading magnitude and ΔCt.Th was not as pronounced as the more proximal cross-sections. Also, bone formation responses along the periosteum did not occur in regions of highest compressive and tensile strains predicted by beam theory. This could be due to complex experimental loading conditions which were not explicitly accounted for in the mechanical analysis. Our results show that the bone formation response depends on the load magnitude and the periosteal position. Bone resorption due to the neurectomy of the loaded tibia occurs throughout the entire cross-sectional region for all investigated cortical sections 25, 37, 50, and 75%. For peak applied loads higher than 4 N, compressive and tensile regions show bone formation; however, regions around the neutral axis show constant resorption. The 50% cross-section showed the most regular ΔCt.Th response with increased loading when compared to 25 and 37% cross-sections. Relative thickness gains of approximately 70, 60, and 55% were observed for F = 12 N in the 25, 37, and 50% cross-sections. ΔCt.Th at selected points of the periosteum follow a linear response with increased peak load; no lazy zone was observed at these positions.

Low-threshold strain-compensated InGaAs/(In,Al)GaAs multi-quantum well nanowire lasers emitting near 1.3 μm at room temperature

Realizing telecom-band lasing in GaAs-based nanowires (NW) with low bandgap gain media has proven to be notoriously difficult due to the high compressive strain built up in the active regions. Here, we demonstrate an advanced coaxial GaAs-InGaAs multi-quantum well (MQW) nanowire laser that solves previous limitations by the introduction of a strain compensating InAlGaAs buffer layer between the GaAs core and the MQW active region. Using a buffer layer thickness comparable to the core diameter applies a significant tensile strain to the GaAs core which efficiently minimizes the compressive strain in the InGaAs MQW and enables large In-content without plastic relaxation. Experimental verification is shown for NW-lasers with an In-content of up to 40% in the MQW, evidencing a clear strain-relieved redshift of the lasing emission and a strong reduction of the lasing threshold compared to highly strained MQWs in state-of-the-art GaAs NW-lasers. This way we achieve optically pumped room temperature lasing operation with a threshold below 50 μJ cm−2 in the telecom O-band close to 1.3 μm.

Transverse Flexural Behaviour of Steel-Engineering Cementitious Composites (ECC) Composite Deck under Negative and Positive Bending Forces

Orthotropic steel bridge deck system usually consists of an orthotropic steel deck and an asphalt overlay. Fatigue cracks of the orthotropic steel deck and premature damage of the asphalt overlay are frequently reported for such system. Engineering cementitious composites (ECC) was therefore proposed to replace the asphalt overlay to address the aforementioned issues. The current study presents an investigation on the transversal flexural behaviour of the ECC under bending forces. Influence of the bending force direction, cover thickness, the number of longitudinal reinforcement steel bars on the flexural performance was revealed. Responses with regard to the load-deflection curve, failure mode, the ultimate capacity, the cracking behaviour, the interfacial slip between ECC and steel deck and the nominal cracking stresses were analysed. The results showed that the load-deflection response under both negative and positive bending forces exhibits elastic stage, crack-developing stage and yield stage. Compared with the reinforcement ratio, cover thickness plays a more significant role on the flexural performances. When the cover thickness decreases from 35 mm to 25 mm, the peak load increases by 21%–25%. ECC maintains its feature of being ductile, with high tensile and compressive strain capacity in the composite slab. From the design point of view, reducing the cover thickness and increasing the reinforcement ratio can improve the ultimate load and cracking stress, and reduce the internal slip, strain and crack width of the composite slab. It is expected that the current study can provide basic knowledge to the design and application of the steel-ECC composite deck system.

High Deformable Concrete (HDC) element: An experimental and numerical study

High deformable concrete (HDC) elements have compressive strength rates equal to conventional concrete and have got a high compressive strain at about 20% to 50%. These types of concrete elements as prefabricated parts have an abundance of applications in the construction industry which is the most used in the construction of tunnels in squeezing grounds, tunnel passwords from fault zones or swelling soils as soft supports. HDC elements after reaching to compressive yield stress, in nonlinear behavior have hardening combined with increasing strain and compressive strength. The main aim of this laboratory and numerical research is to construct concrete elements with the above properties so the compressive stress-strain behavior of different concrete elements with four categories of mix designs have been discussed and finally one of them has been defined as HDC element mix design. Furthermore, two columns with and without implementing of HDC elements have been made and stress-strain curves of them have been investigated experimentally. An analysis model is presented for columns using finite element method adopted by ABAQUS. The results obtained from the ABAQUS finite element method are compared with experimental data. The main comparison is made for stress-strain curve. The stress-strain curves from the finite element method agree well with experimental results. The results show that the dimension of the HDC samples is significant in the stress-strain behavior. The use of the element greatly increases energy absorption and ductility.

Machining Ti-6Al-4V Alloy Using Nano-Cutting Fluids: Investigation and Analysis

Minimum Quantity Lubrication nanofluid (MQL-nanofluid) is a viable sustainable alternative to conventional flood cooling and provides very good cooling and lubrication in the machining of difficult to cut materials such as titanium and Inconel. The cutting action provides very difficult conditions for the coolant to access the cutting zone and the level of difficulty increases with higher cutting speeds. Furthermore, high compressive stresses, strain hardening and high chemical activity results in the formation of a ‘seizure zone’ at the tool-chip interface. In this work, the impact of MQL-nanofluid at the seizure zone and the corresponding effects on tool wear, surface finish, and power consumption during machining of Ti-6Al-4V was investigated. Aluminum Oxide (Al2O3) nanoparticles were selected to use as nano-additives at different weight fraction concentrations (0, 2, and 4 wt.%). It was observed that under pure MQL strategy there was significant material adhesion on the rake face of the tool while the adhesion was reduced in the presence of MQL-nanofluid at the tool-chip interface, thus indicating a reduction in the tool chip contact length (TCCL) and reduced seizure effect. Furthermore, the flank wear varied from 0.162 to 0.561 mm and the average surface roughness (Ra) varied from 0.512 to 2.81 µm. The results indicate that the nanoparticle concentration and the reduction in the seizure zone positively influence the tool life and quality of surface finish.

Using a big data approach to explore in situ chondrocyte response to impact loading in articular cartilage

Using a big data approach to explore in situ chondrocyte response to impact loading in articular cartilage

Development of residual strains and their relaxation processes in atomically thin layers of core-shell structured nanoparticles

Residual elastic strains imposed on atomically thin films coated onto substrate materials cause changes in the electronic structures of such films. This knowledge has been employed in various industrial sectors as a means of tuning the optical, electrical, magnetic, and chemical properties of materials. Although the magnitudes of residual strains and properties of materials are closely related to the thickness of coating layers, the measurement of residual strains that develop in atomically thin films is challenging owing to the experimental complexities of conventional measurement methods. In this work, the residual strains developed in atomically thin Au overlayers grown epitaxially on Pd nanoparticles were measured using transmission electron microscopy based on nanobeam precession electron diffraction. Experiments revealed that a 1-nm-thick Au film can withstand an exceptionally high compressive strain of 4.3%, which is reduced to nearly zero as the film thickness increases beyond 5 nm. The microstructural evolution of Au films was monitored using high-resolution transmission electron microscopy and the large strain storage capacity and plastic relaxation behavior of Au films were interpreted by comparing them with the previous computer simulations and theoretical models.

Role of laser scan strategies in defect control, microstructural evolution and mechanical properties of steel matrix composites prepared by laser additive manufacturing

Steel matrix composites (SMCs) reinforced with WC particles were fabricated via selective laser melting (SLM) by employing various laser scan strategies. A detailed relationship between the SLM strategies, defect formation, microstructural evolution, and mechanical properties of SMCs was established. The laser scan strategies can be manipulated to deliberately alter the thermal history of SMC during SLM processing. Particularly, the involved thermal cycling, which encompassed multiple layers, strongly affected the processing quality of SMCs. S-shaped scan sequence combined with interlayer offset and orthogonal stagger mode can effectively eliminate the metallurgical defects and retained austenite within the produced SMCs. However, due to large thermal stress, microcracks that were perpendicular to the building direction formed within the SMCs. By employing the checkerboard filling (CBF) hatching mode, the thermal stress arising during SLM can be significantly reduced, thus preventing the evolution of interlayer microcracks. The compressive properties of fabricated SMCs can be tailored at a high compressive strength (∼3031.5 MPa) and fracture strain (∼24.8%) by adopting the CBF hatching mode combined with the optimized scan sequence and stagger mode. This study demonstrates great feasibility in tuning the mechanical properties of SLM-fabricated SMCs without varying the set energy input, e.g., laser power and scanning speed.

Strained Silicon-on-Insulator Platform for Cointegration of Logic and RF—Part I: Implant-Induced Strain Relaxation

The relaxation of tensile strain in fully depleted (FD) strained silicon-on-insulator (SSOI) by means of ion implantation is experimentally demonstrated in this work. This could enable SiGe p-channel field-effect transistors (pFETs) with high compressive strain (after ion implantation and Ge condensation) to be formed together with Si n-channel field-effect transistors (nFETs) with high tensile strain on the same substrate. From simulations in advanced technology node, 0.8% strain of nFETs and −0.9% strain of pFETs in fin structures can provide saturation drain current and peak ${G}_{\text {m}}$ enhancements of ~20%–30%. ${f}_{\text {T}}$ and ${f}_{\text {max}}$ benefit greatly from strain across the entire range of ${V}_{\text {G}}$ , with their peak values increasing significantly, thus allowing SSOI devices to meet 5G targets. In addition, forward back-bias shifts ${f}_{\text {T}}$ and ${f}_{\text {max}}$ curves toward lower $\boldsymbol \vert {V}_{\text {G}}\boldsymbol \vert $ , enabling reduced power consumption at the same high performance and providing better linearity. Hence, the ability to form highly strained nFETs and pFETs together on a common FD-SSOI substrate paves the way for it to become the ultimate high-performance complementary metal-oxide-semiconductor (CMOS) platform for 5G RF and logic circuits. The relaxation of the tensile strain is demonstrated and documented in Part I. A novel Comb-like device architecture to further enhance the SSOI electrical and RF performance is provided in Part II.

Can barb thread design improve the pullout strength of bone screws?

AimsTo draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws.MethodsButtress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared.ResultsThe barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure.ConclusionBone screws with a reverse buttress thread design will significantly increase the pullout strength.Cite this article: Bone Joint Res 2021;10(2):105–112.

Electronic and transport properties of GaAs/InSe van der Waals heterostructure

Recently, the GaAs/InSe heterostructure was synthesized experimentally, and the spatial redistribution of charge and motion of energy-resolved photoelectron was imaged. To gain more insight into the detailed electronic structure and expand knowledge to transport behaviors and physical field tuning effects, we here construct the GaAs/InSe van der Waals heterostructure theoretically and perform investigations in depth, especially focusing on the comprehensive understanding and mechanism analysis of results, trying to create new predictions. The results show that such a heterostructure holds a typical type-II band alignment and its band gap is narrowed significantly as compared with its each component, and the indirect-direct band gap transition is realized, which holds great potential applications in developing excellent photovoltaic materials and new photo-electronic devices. Particularly, the carrier mobility of heterostructure is predicted to be enhanced dramatically to μ > 104 cm2 V−1 s−1, greatly overcoming the intrinsic weakness of InSe monolayer with a very low hole mobility, ~101 cm2 V−1 s−1. Meanwhile, we find that the electronic structure of the heterostructure is flexibly controllable. Under higher compressive strain and whole tensile strain, its band-gap size drops linearly. While by applying an external electric field, the band offset is increased significantly, and the type-II band alignment is well preserved and the band gap drops significantly under positive external electric field, These flexibly tunable properties are more favorable to design the photovoltaic materials and photo-electronic devices.