Deformation Till Research Articles

Effect of torsional deformation on crystallographic evolution of carbide-free nano-bainitic steels prepared at two different austempering temperatures

The current study investigates the nature and extent of crystallographic change after torsional deformation in nano-structured bainite. This is extremely useful as nano-structured bainite is not stable under mechanical deformation and the evolved structure under torsion is finally going to determine other mechanical responses like fracture and fatigue. Two blocks of nano-bainitic steels were prepared after austenitization at 950°C and austempering at 250°C (NB250) and 350°C (NB350) respectively. It was found that there was a decrease in the bainitic ferrite (BF) and retained austenite (RA) length scale with a reduction in austempering temperature along with reduction in the RA content. Specimens from the undeformed two blocks (NB250-UD and NB350-UD) were subjected to torsional deformation till failure (NB250-T and NB350-T) and the crystallographic characteristics of the torsion-tested and undeformed specimens were obtained using electron back-scattered diffraction (EBSD). The orientation relationship (OR) between BF and RA for NB250-UD and NB350-UD was close to Kurdjumov-Sachs (K-S) which changed to predominantly Nishiyama Wassermann (NW) after torsion deformation (NB250-T and NB350-T). Significant refinement in packet and block was observed as a result of torsional deformation. Variant selection was stricter for NB350-UD than NB250-UD but torsional deformation led to weakening of variant selection. The extent of lowest misorientation V1-V4 variant pairing was higher for NB350-UD but it did not change much with torsion in case of NB250-T whereas NB350-T displayed a reduction. Fractography revealed that the dimple size corresponded to block size range between the undeformed and torsion-tested sample for the respective austempering condition.

Microstructure and mechanical properties of medium-entropy TiNbZr alloy-based composites, reinforced with boride particles

The TiZrNb metal-matrix composites reinforced by in-situ formed borides were produced by vacuum arc melting using different amount of TiB2 (0.2, 2.0 and 4.4 wt%). Structure, mechanical properties and biocompatibility of the composites were studied. The initial microstructures of the composites were composed of the bcc TiZrNb matrix and needle-like (Ti, Nb) B particles the volume fraction of which was ∼ 1.0%, 6.8% and 13.2%, respectively. Besides a small amount of the ω phase particles measuring ∼ 10 nm were found in the matrix of all the composites. Compression test at room temperature showed that the minimum content of the borides did not have noticeable strengthening effect on mechanical properties of the composite. An increase in the amount of (Ti, Nb) B to 6.8 vol% resulted in an increase in the yield stress by 22% to ∼ 900 MPa without a visible decrease in ductility. The composite with 13.2 vol% of the borides showed the yield strength of 1010 MPa and compression ductility (deformation till fracture) of 9% that can be associated with a hypereutectic composition and appearance of coarse particles of primary (Ti, Nb) B. Evaluation of main strengthening mechanisms suggested that the load transfer strengthening contributed mainly to the overall strength of the composite. Analysis of biocompatibility suggests some decrease in the proliferation rate of mesenchymal stem cells with an increase in the borides amount.

Experimental Study on Strength and Microstructure of Glacial Till Stabilized by Ionic Soil Stabilizer

Glacial till, widely distributed in southwest China, is a special soil directly deposited by detritus formed from melting Quaternary glaciers. In this paper, the F1 ionic soil stabilizer was adopted for stabilizing the glacial till to improve its mechanical strength. A series of micro and macro tests were carried out to study the mechanical properties and microstructure of stabilized soil with the F1 ionic soil stabilizer. The results show that the F1 ionic soil stabilizer can destroy the diffuse double layer structure on the surface of glacial till particles and reduce the thickness of the adsorbed water layer through strong cation exchange and hydrophobic interactions of active sulfonated oil, which reduce the spacing of glacial till particles, enhance the aggregation of glacial till particles, and effectively suppress the swelling deformation of the glacial till. It can be concluded that the water sensitivity and compaction characteristics of glacial till can be significantly improved by the stabilization of the F1 ionic soil stabilizer. Moreover, the mechanical strength of the glacial till can be significantly improved by the stabilization of the F1 ionic soil stabilizer. This article is helpful as a guideline for practical design and future research on applying the F1 ionic soil stabilizer to improve the bearing capacity of foundations in glacial till areas.

Sedimentary basins reduce stability of Antarctic ice streams through groundwater feedbacks

Antarctica preserves Earth’s largest ice-sheet, which in response to climate warming, may lose ice mass and raise sea level by several metres. The ice-sheet bed exerts critical controls on dynamic mass loss through feedbacks between water and heat fluxes, topographic forcing, till deformation and basal sliding. Here we show that sedimentary basins may amplify critical feedbacks that are known to impact ice-sheet retreat dynamics. We create a high-resolution subglacial geology classification for Antarctica by applying a supervised machine-learning method to geophysical data, revealing the distribution of sedimentary basins. Hydro-mechanical numerical modelling demonstrates that during glacial retreat, where sedimentary basins exist, the groundwater discharge rate scales with the rate of ice unloading. Antarctica’s most dynamic ice streams, including Thwaites and Pine Island glaciers, possess sedimentary basins in their upper catchments. Enhanced groundwater discharge and its associated feedbacks are likely to amplify basal sliding and increase the vulnerability of these catchments to rapid ice retreat and enhanced dynamic mass loss.

In Situ Deformation Monitoring of 3D Woven Composite T-Profile Using MXene Nanoparticles.

The aim of this study was to develop a process-efficient smart three-dimensional (3D) woven composite T-profile by depositing MXene nanoparticles at the junction for sensing damage and deformation at the junction. Such smart composites could find application in the online health monitoring of complex-shaped parts. The composites were manufactured by infusing epoxy resin in a single-layer fabric T-profile preform, woven in folded form on a dobby shuttle loom using 300 tex glass roving. The chemically etched Ti3C2Tz MXene nanoparticles were dispersed in deionised water and 10 layers were sprayed at the junction of the composite to form a conductive coating. The MXene-coated composite T-profile specimens were subjected to tensile and fatigue loading to study the electromechanical response of the MXene coating to applied displacement. The results showed that the MXene coating was able to sense the sample deformation till ultimate failure of the composite. The MXene coating was also able to effectively sense the tensile–tensile fatigue loading, carried out at 2000 cycles and 4000 cycles for a 50 N–0.5 Hz and a 100 N–1 Hz load–frequency combination, respectively, while being sensitive to the overall deformation of the composite. The smart complex-shaped composites developed in this work were capable of monitoring their health under tensile and fatigue loading in real time.

Geophysical investigation in sediment cores and its relationship with the governing sedimentary processes at Bransfield Basin, Antarctica.

This research aims to investigate sediment cores from a glaciomarine environment based on their petrophysical parameters to elucidate lithological and sedimentary issues, as well as to identify a geophysical signature based on their parameter's response. To achieve this objective, six marine sediment cores were collected in the Central Bransfield Basin - Antarctica, the lengths ranging from 1.5 to 5.2 meters in water depths ranging from 304 to 1463 meters. The cores were submitted to different analyses and values from density, magnetic susceptibility, electrical resistivity, p-wave velocity, total gamma radiation, silt, clay and sand contents, and mean grain size for each core location were considered. Four large lithologies were identified according to their geological and geophysical characteristics. The first group is subglacial deformation till (GC16); the second is massive diamicton (GC13 and GC12), the third group is composed of diamictons from the basin (AM10) and lower slope (GC09); the fourth lithological group is composed of siliceous mud from an upper slope location (GC06A). The characteristics recorded across Central Bransfield Basin (from South Shetlands Islands to Antarctic Peninsula) highlighted the relationship between the lithological content and associated depositional processes with the geophysical proprieties as density and magnetic susceptibility.

Large strain flow curve identification for sheet metals under complex stress states

Strain hardening behaviours at large strain under various loading conditions are the basic but the most important input for reliable numerical simulation of plastic deformation processes, such as sheet metal forming and crash. However, neither the flow curve at large strain beyond necking nor the strain hardening under stress states different from uniaxial tension can be reasonably characterized by the widely employed tensile tests of dogbone specimens. In this study, various experimental methods are investigated to characterize strain hardening behaviours up to large deformation under different stress states for an aluminium alloy sheet of AA5182-O. The experiments conducted include tensile tests of four different specimens (e.g. dog-bone specimen, notched specimen, specimen with a central hole and in-plane shear specimen), bulge tests and twin bridge shear tests. These tests cover wide stress states ranging from shear to equibiaxial tension. Strain hardening is obtained by both analytical computation and an inverse engineering approach under different loading conditions of shear, uniaxial tension, plane strain tension and equibiaxial tension. These two approaches are evaluated by comparing the obtained stress-strain curves under different loading conditions. The evaluation shows that the inverse engineering approach is an effective method to characterize the stress-strain curve up to large plastic deformation till fracture for tests with inhomogeneous deformation. The results also reveal that it needs to develop advanced yield functions to model yielding and hardening behaviours under complex stress states.

Frictional Origin of Slip Events of the Whillans Ice Stream, Antarctica

AbstractIce sheet evolution depends on subglacial conditions, with the ice‐bed interface's strength exerting an outsized role on the ice dynamics. Along fast‐flowing glaciers, this strength is often controlled by the deformation of subglacial till, making quantification of spatial variations of till strength essential for understanding ice‐sheet contribution to sea‐level. This task remains challenging due to a lack of in situ observations. We analyze continuous seismic data from the Whillans Ice Plain (WIP), West Antarctica, to uncover spatio‐temporal patterns in subglacial conditions. We exploit tidally modulated stick‐slip events as a natural source of sliding variability. We observe a significant reduction of the till seismic wave‐speed between the WIP sticky‐spots. These observations are consistent with a poroelastic model where the bed experiences relative porosity and effective pressure increases of >11% during stick‐slips. We conclude that dilatant strengthening appears to be an essential mechanism in stabilizing the rapid motion of fast‐flowing ice streams.

A slip law for hard-bedded glaciers derived from observed bed topography.

Ice-sheet responses to climate warming and associated sea-level rise depend sensitively on the form of the slip law that relates drag at the beds of glaciers to their slip velocity and basal water pressure. Process-based models of glacier slip over idealized, hard (rigid) beds with water-filled cavities yield slip laws in which drag decreases with increasing slip velocity or water pressure (rate-weakening drag). We present results of a process-based, three-dimensional model of glacier slip applied to measured bed topographies. We find that consideration of actual glacier beds eliminates or makes insignificant rate-weakening drag, thereby uniting process-based models of slip with some ice-sheet model parameterizations. Computed slip laws have the same form as those indicated by experiments with ice dragged over deformable till, the other common bed condition. Thus, these results may point to a universal slip law that would simplify and improve estimations of glacier discharges to the oceans.

Grounding zone subglacial properties from calibrated active-source seismic methods

Abstract. The grounding zone of Whillans Ice Stream, West Antarctica, exhibits an abrupt transition in basal properties from the grounded ice to the ocean cavity over distances of less than 0.5–1 km. Active-source seismic methods reveal the downglacier-most grounded portion of the ice stream is underlain by a relatively stiff substrate (relatively high shear wave velocities of 1100±430 m s−1) compared to the deformable till found elsewhere beneath the ice stream. Changes in basal reflectivity in our study area cannot be explained by the stage of the tide. Several kilometres upstream of the grounding zone, layers of subglacial water are detected, as are regions that appear to be water layers but are less than the thickness resolvable by our technique. The presence of stiff subglacial sediment and thin water layers upstream of the grounding zone supports previous studies that have proposed the dewatering of sediment within the grounding zone and the trapping of subglacial water upstream of the ocean cavity. The setting enables calibration of our methodology using returns from the floating ice shelf. This allows a comparison of different techniques used to estimate the sizes of the seismic sources, a constraint essential for the accurate recovery of subglacial properties. We find a strong correlation (coefficient of determination=0.46) between our calibrated method and a commonly used multiple-bounce method, but our results also highlight the incomplete knowledge of other factors affecting the amplitude of seismic sources and reflections in the cryosphere.

Experimental Investigation on Micro Deep Drawing of Stainless Steel Foils with Different Microstructural Characteristics

In the present work, austenitic stainless steel (ASS) 304 foils with a thickness of 50 µm were first annealed at temperatures ranging from 700 to 1100 ℃ for 1 h to obtain different microstructural characteristics. Then the effects of microstructural characteristics on the formability of ASS 304 foils and the quality of drawn cups using micro deep drawing (MDD) were studied, and the mechanism involved was discussed. The results show that the as-received ASS 304 foil has a poor formability and cannot be used to form a cup using MDD. Serious wrinkling problem occurs on the drawn cup, and the height profile distribution on the mouth and the symmetry of the drawn cup is quite non-uniform when the annealing temperature is 700 ℃. At annealing temperatures of 900 and 950 ℃, the drawn cups are both characterized with very few wrinkles, and the distribution of height profile, symmetry and mouth thickness are uniform on the mouths of the drawn cups. The wrinkling becomes increasingly significant with a further increase of annealing temperature from 950 to 1100 ℃. The optimal annealing temperatures obtained in this study are 900 and 950 ℃ for reducing the generation of wrinkling, and therefore improving the quality of drawn cups. With non-optimized microstructure, the distribution of the compressive stress in the circumferential direction of the drawn foils becomes inhomogeneous, which is thought to be the cause of the occurrence of localized deformation till wrinkling during MDD.

Lithopetrographic and geochemical features of the Saalian tills in the Szczerców outcrop (Poland) in various deformation settings

Abstract This paper presents the results of new studies of Saalian tills, from the Ławki and Rogowiec formations, filling the Kleszczów Graben. The study area is located in the Szczerców outcrop, Bełchatów Lignite Opencast Mine, central Poland. Laboratory studies included macrofossil analysis of the deposits, as well as petrographic and geochemical (neodymium isotope ratio) measurements. The studies were carried out in 2014–2016 and resulted in both establishing the sedimentary Saalian complex and constructing geological cross-sections and a synthetic lithostratigraphic profile. Development of sediments in this part of the Kleszczów Graben in the Pleistocene was largely influenced by tectonic factors (Chabielice fault, Dębina Salt Dome) and glacitectonic processes (Wartanian Glaciation). The Saalian tills (T4 – Ławki and T7 – Rogowiec lithotypes) are between the Holsteinian sand with macroremnants of trees and the Eemian gyttja and peat. Petrographic coefficients for lithotype T4 (Ławki Formation) are 1.33–1.06–1.01 and 0.12 and for lithotype T7 (Rogowiec Formation) are 1.29–1.23–1.04 and 0.12. Investigations of the Nd isotopic compositions of the studied samples reinforce our interpretations of till deformation and tentative lithostratigraphic correlations. Neodymium isotope ratios “P” (−14.4 ± 0.7) and “D” (−12.4 ± 0.3) ε Nd values (2σ) correspond to mean signatures of Saalian glacigenic moraine sediment. This proves that ε Nd values less than −12.4 reflect the southern Fennoscandian Ice Sheet sediment provenance, but ε Nd values greater than −12.4 indicate the western European origin.

Water pressure fluctuations control variability in sediment flux and slip dynamics beneath glaciers and ice streams

Rapid ice loss is facilitated by sliding over beds consisting of reworked sediments and erosional products, commonly referred to as till. The dynamic interplay between ice and till reshapes the bed, creating landforms preserved from past glaciations. Leveraging the imprint left by past glaciations as constraints for projecting future deglaciation is hindered by our incomplete understanding of evolving basal slip. Here, we develop a continuum model of water-saturated, cohesive till to quantify the interplay between meltwater percolation and till mobilization that governs changes in the depth of basal slip under fast-moving ice. Our model explains the puzzling variability of observed slip depths by relating localized till deformation to perturbations in pore-water pressure. It demonstrates that variable slip depth is an inherent property of the ice-meltwater-till system, which could help understand why some paleo-landforms like grounding-zone wedges appear to have formed quickly relative to current till-transport rates.

A full-range stress-strain model for metallic materials depicting non-linear strain-hardening behavior

Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analysis of metals. Recently, 2-stage and 3-stage R-O variant models have been proposed to replicate stress-strain behavior under large plastic deformation. The complexity of these models increases with the addition of each stage. Moreover, these models have considered deformation till necking only. In this paper, a simplistic multi-stage constitutive model is proposed to capture the strain-hardening non-linearity shown by metals including its post necking behavior. The constitutive parameters of the proposed stress-strain model can be determined using only elastic modulus and yield strength. 3-D digital image correlation was used as an experimental tool for measuring full-field strains on the specimens, which were subsequently utilized to obtain the material parameters. Our constitutive model is demonstrated with an aerospace-grade stainless steel AISI 321 wherein deformation response averaged over the gauge length (GL) and at a local necking zone are compared. The resulting averaged and local material parameters obtained from the proposed model provide interesting insights into the pre and post necking deformation behavior. Our constitutive model would be useful for characterizing highly ductile metals which may or may not depict non-linear strain hardening behavior including their post necking deformations.

Analytical and finite element modelling of hydraulic bulge test on extra deep drawing steel with fractography study

ABSTRACT In this paper, analytical, finite element modelling (FEM) and experimental studies are conducted on the biaxial stretching of extra deep drawing steel sheet using hydraulic bulge test, where the true plastic strain exceeds 70%, in contrast to the 20–30% strain achieved in the conventional uniaxial tensile test. The analytical modelling includes four different approaches, namely, Hill, Panknin, Chakrabarty and Kruglov. FEM is done using three yield criteria, Hill-48, Barlat-89 and Barlat-2000. Experimental results show that the stress-strain relationship using bulge radius based on Panknin approach and thickness based on Kruglov approach in the analytical study and using Barlat-2000 yield model in FEM study are in close agreement with the experimental curve. Fractography study, conducted on specimens from tensile and bulge test, reveals/confirms the presence of more deep elongated shear dimples in bulge test compared to equiaxed dimples in the tensile test. This corroborates with the experimental results of achieving the high level of plastic deformation till fracture in the hydraulic bulge test.

Converging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario

The hypothesis that Oak Ridges Moraine (ORM) formed between converging ice streams requires critical testing. Available data (e.g., digital elevation models, maps, seismic profiles, continuous cores, and pit exposures) are inconsistent with the converging ice stream hypothesis. Combined analysis of landform and subsurface data permits testing the ORM area stratigraphic sequence and sedimentary origin. Stratigraphic data indicate that drumlinized Newmarket Till, incised by north–south-oriented (tunnel) valleys, extends beneath ORM. Thus, streamlining on Newmarket Till is older than ORM and has no direct bearing on its formation. The north–south-trending valleys truncate streamlined Newmarket Till, extend to bedrock, have inset eskers, and occur beneath ORM. Hence, these valleys are older than ORM and have a subglacial rather than a proglacial origin. Overlying the mega-scale lineations and incised channels are topographically elevated (>300 m a.s.l.), ORM glaciofluvial–glaciolacustrine sequences. Its east to west paleoflow trend indicates an east–west-oriented hydraulic gradient, orthogonal to expected gradients of proposed north-south converging ice streams. The exclusive presence of ORM meltwater sediments, with rare deformation, is incompatible with a converging ice stream, deforming-bed hypothesis. Halton sediment grades upward from stratified sand (ORM) to interbedded diamicton and glaciolacustrine sediment, rather than deformation till. Halton sediment overlies ORM and consequently the proposed Halton ice streaming is younger than the moraine. Halton Till is present in few of the predicted ice stream areas, and where Halton Till is present, it has no mega-scale lineations. In sum, the weight of evidence unequivocally argues against a converging ice-stream process model for the ORM.

A slip law for glaciers on deformable beds.

Slip of marine-terminating ice streams over beds of deformable till is responsible for most of the contribution of the West Antarctic Ice Sheet to sea level rise. Flow models of the ice sheet and till-bedded glaciers elsewhere require a law that relates slip resistance, slip velocity, and water pressure at the bed. We present results of experiments in which pressurized ice at its melting temperature is slid over a water-saturated till bed. Steady-state slip resistance increases with slip velocity owing to sliding of ice across the bed, but above a threshold velocity, till shears at its rate-independent Coulomb strength. These results motivate a generalized slip law for glacier-flow models that combines processes of hard-bedded sliding and bed deformation.

Sub‐annual moraine formation at an active temperate Icelandic glacier

AbstractThis paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low‐relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub‐annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub‐annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt‐driven squeeze events and (ii) larger push moraines formed during winter re‐advances. We suggest the development of this process‐form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice‐marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process‐form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica

AbstractRecent seismic measurements from upper Thwaites Glacier indicate that the bed-type variability is closely related to the along-flow basal topography. In high-relief subglacial highlands, stoss sides of topographic highs have a relatively higher acoustic impedance (‘hard’ bed) with lower acoustic impedance (‘soft’ till) on lee sides. This pattern is similar to observations of many deglaciated terrains. Subglacial hydraulic-potential gradient and its divergence show a tendency for water to diverge over the stoss sides and converge into the lee sides. Convergence favors a thicker or more widespread water system, which can more efficiently decouple ice from the underlying till. Under such circumstances, till deformation does occur but, fluxes are relatively small. Till carried from the lee sides onto stoss sides of downstream bumps should couple to the ice more efficiently, increasing the ability for transport by till deformation. In turn, this suggests that steady-state till transport can be achieved if the stoss-side till layer is thin or discontinuous. In addition, the large basal shear stress generated in the highlands seems too high for a bed lubricated by a continuous although thin deforming till, suggesting till discontinuity, which would allow debris-laden ice to erode bedrock on stoss sides, supplying additional till for transport.

Surface melt‐driven seasonal behaviour (englacial and subglacial) from a soft‐bedded temperate glacier recorded by in situ wireless probes

AbstractWe investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique Glacsweb wireless in situ probes (embedded in the ice and the till) combined with other techniques [including ground penetrating radar (GPR) and borehole analysis]. During the melt season (spring, summer and autumn), high surface melt leads to high water pressures in the englacial and subglacial environment. Winter is characterized by no surface melting on most days (‘base’) apart from a series of positive degree days. Once winter begins, a diurnal water pressure cycle is established in the ice and at the ice/sediment interface, with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag. This direct surface melt also drives water pressure changes in the till. Till deformation occurred throughout the year, with the winter rate approximately 60% that of the melt season. We were able to show the bed comprised patches of till with different strengths, and were able to estimate their size, relative percentage and temporal stability. We show that the melt season is characterized by a high pressure distributed system, and winter by a low pressure channelized system. We contrast this with studies from Greenland (overlying rigid bedrock), where the opposite was found. We argue our results are typical of soft bedded glaciers with low englacial water content, and suggest this type of glacier can rapidly respond to surface‐driven melt. Based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets, which may become more channelized in winter, and more responsive to changes in meltwater inputs. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.