Deformation Zone Research Articles

High-strain rate deformation of aluminum during the Taylor test

The aim of the study is to develop a methodology for assessing changes in the microstructure of aluminum under dynamic deformation in a rather wide range of the strain rate and strain degree. The distribution of the microstructure and the strength properties in the cross-section of pure aluminum samples (A99) after dynamic deformation according to the Taylor test were studied. The tests were carried out at room temperature using a PG-20 light-gas cannon, at sample throwing speeds of 127 and 165 m/sec. An interference microscope (Leica IM DRM) and a scanning electron microscope (Jeol JSM-6490) were used to study the aluminum microstructure; the microhardness measurements were carried out on an HVS-1000 device to study the uniformity of the strain distribution in samples. It is shown that three characteristic areas can be distinguished in aluminum samples after Taylor test: the elastic deformation zone, the plastic deformation zone, and the zone of severe plastic deformation, which is located in the area of collision of the sample with a steel barrier. It is shown that dynamic deformation reduced the grain structure from 1 – 1.1 mm to 2.5 – 3 μm at high impact velocities. An elongated grain shape is observed in the collision zone. The proposed method provided determination of the critical strain degree necessary for the onset of grain fragmentation and allowed us to explain the formation of zones of weak and severe plastic deformation. It is shown that the critical strain degree corresponding to the beginning of grain fragmentation increases from 0.18 to 0.21 with an increase in the throwing speed of the sample from 127 to 165 m/sec. In the zone of weak deformation, plastic deformation proceeds by intragrain riveting and the initial stages of grain fragmentation. In the zone of severe plastic deformation, a fine-grained microstructure is formed, which leads to an increase in the microhardness of aluminum in accordance with the Hall – Petch equation.

Polyphase formation of a Neoarchean auriferous fault zone network in the Michipicoten greenstone belt, southern Superior craton

Correlating structurally distinctive fault zones for understanding an unknown deformation system at the regional scale remains a challenge for understanding orogenic evolution and gold endowment. The current study deals with this challenge in the southern Michipicoten greenstone belt (MGB) of the Superior craton focusing on a Neoarchean auriferous fault zone network. Three deformation events associated with episodic gold mineralization are revealed in the ca. 2745 Ma host granitoid: (1) NW‒SE shortening recorded by the subvertical Grace and Minto B fault zones and locally the inclined Jubilee and Hornblende fault zones; (2) top-to-NNE strike-slip to oblique faulting indicated primarily by the dominant structures of the Jubilee and Hornblende fault zones; and (3) top-to-NE extension demonstrated by the northeast-dipping Parkhill #4 and Cooper fault zones. Fault zone lithologies and mineral assemblages suggest that the localization of deformation for the formation of these fault zones was controlled by rheological heterogeneities and syn-deformation fluids. The first and second events are correlated with two shortening events in a gold-endowed, structurally and kinematically distinctive deformation zone of the northern MGB. This correlation based on deformation processes suggests a larger footprint of gold mineralization associated with a regional deformation in the MGB and has implications for investigating structural evolution of orogens and orogenic gold mineralization in general.

A universal simulation model of the continuous pipe rolling process on a controllably movable mandrel.

To study the technological process of rolling solid and hollow round profiles, it is important to have a correct mathematical description of the patterns that determine the boundaries of the deformation zone. The article analyzed scientific works that examine the calculation of geometric parameters of the deformation zone during the rolling of solid and hollow round profiles in two-roll and multi-roll calibers. As a result of the analysis, a conclusion was drawn regarding the necessity of a more detailed description of the determination patterns for the geometric boundary conditions of the deformation zone. This led to the proposal of a universal method for determining the shape of the billet and the shape of the caliber groove, as well as the derivation of the equations for the roll surface and the boundary of the contact surface of the deformation zone for various rolling schemes. The developed method allows for an increase in the accuracy of calculating the energy-force parameters of the rolling processes, including continuous rolling, in the production of solid and hollow round profiles according to the circular–oval scheme in calibers formed by any number of rolls, thanks to the consideration of a sufficiently wide range of geometric features

An investigation of force and pressure analysis during the process of equal channel angular pressing to M1 copper using finite element and upper-bound methods

This article presents two methods to determine pressing forces to the M1 copper plate. The first approach employs the upper-bound method, and the second method combines numerical simulation with a central composite design. The upper-bound method uses physical analysis to determine the deformation zone and establish the division of the rigid block model. The findings were identical to the slip-line solution method. The results obtained from the three-dimensional simulation performed using Qform software combined with a central composite design have provided regression equations that help determine the force and punching pressure. The impact of each parameter on the pressing force is similar in both approaches, and the difference between the two methods is insignificant and falls within a dependable range.

Vertical vibration model for the roll system of a six-high rolling mill based on the Timoshenko beam theory

During the production of cold-rolled strips, the high-speed operation of rolling mills generates vibrations that significantly impact the production efficiency, the strip quality, and the rolling mill service life. Therefore, investigating the vibration characteristics of rolling mills is of paramount importance. Previous studies predominantly treated the rolls as point masses, overlooking variations in the vibrations along the lengths of the rolls. In this study, the working, intermediate, and backup rolls were regarded as continuous elastic bodies, and they were simplified as Timoshenko beams. The modal superposition method was used to solve the vertical vibration equations for the rolls of a six-high rolling mill; thus, the natural frequencies and modal shapes for the rolls were obtained for both free and forced vibrations. A finite-element model validation confirmed that the accuracy of the novel Timoshenko beam six-high rolling mill vibration model introduced in this paper is significantly higher than that of the traditional Euler beam model when the roller length-to-diameter ratio is relatively small. Further analysis based on this model indicates that the forced vibration of the rolls is primarily influenced by fluctuations in rolling force. The amplitude of forced vibration is affected by factors such as the friction coefficient in the deformation zone, rolling speed, and cumulative rolling distance of the work rolls. These findings provide a precise representation of the characteristics of forced vibrations in rolling mills and offer valuable theoretical insight to ensure stable rolling mill operation.

Microstructure evolution and mechanical properties of β/γ-TiAl alloy during high-rate near-isothermal multidirectional forging

The microstructure of β/γ-TiAl alloy was characterized and analyzed in various deformation regions during a high-rate near-isothermal multidirectional forging (HR-NIMDF) process in this study. The results indicate that the localized precipitation of the B2 phase occurs within the large lamella microstructure through DRX and heterogeneous exsolution decomposition mechanism in the stagnant zone. The majority of mixed fine-grained microstructures (α2/γ/B2), with a grain diameter smaller than 1 μm, were formed under an appropriate stress-temperature coupling field. In the central region of the large deformation zone, a small twisted lamellar microstructure with low B2 phase content is observed, suggesting that HR-NIMDF can efficiently decompose the (α2/γ) lamellar structure and achieve refined grain microstructures. After undergoing HR-NIMDF, the β/γ-TiAl alloy exhibits a low tough-brittle transition temperature and an elongation of 7 % at 650 °C, with an ultimate tensile strength of 862.6 MPa. At 700 °C, the elongation increases to 55.4 %, while the ultimate tensile strength decreases to 653.8 MPa. Moreover, this study demonstrates that when the plastic deformation degree is insufficient and the adiabatic warming effect is relatively pronounced, significant precipitation of the B2 phase leads to a reduction in DRX extent within the material, ultimately resulting in the formation of large residual (α2/γ) lamellar microstructure. The unsynchronized thermal-force coupling relationship between the precipitation of the B2 phase and DRX holds significant implications for advancing and refining the thermoplastic deformation process of β/γ-TiAl alloy.

Multiscalar 3D temporal structural characterisation of Smøla island, mid-Norwegian passive margin: an analogue for unravelling the tectonic history of offshore basement highs

Abstract. Smøla island, situated within the mid-Norwegian passive margin, contains crystalline-basement-hosted intricate fracture and fault arrays formed during a polyphase brittle tectonic evolution. Its detailed study may strengthen correlation attempts between the well-exposed onshore domain and the inaccessible offshore domain, further the understanding of the passive margin evolution, and provide useful constraints on petrophysical properties of fractured basement blocks. A combination of geophysical and remote sensing lineament analysis, field mapping, high-resolution drill hole logging, 3D modelling, petrographic and microstructural studies, and fault gouge K–Ar geochronology made it possible to define five deformation episodes (D1 to D5). These episodes occurred between the post-Caledonian evolution of the regional-scale Møre–Trøndelag Fault Complex (MTFC) and the Late Cretaceous and younger crustal extension preceding the final stages of Greenland–Norway break-up. Each reconstructed deformation stage is associated with different structural features, fault and fracture geometries, and kinematic patterns. Synkinematic mineralisations evolved progressively from epidote–prehnite, sericite–chlorite–calcite, chlorite–hematite, hematite–zeolite–calcite, to quartz–calcite. K–Ar geochronology constrains brittle deformation to discrete localisation events spanning from the Carboniferous to the Late Cretaceous. Multiscalar geometrical modelling at scales of 100, 10, and 1 m helps constrain the extent and size of the deformation zones of each deformation episode, with D2 structures exhibiting the greatest strike continuity and D1 features the most localised. Overall, the approach highlighted here is of great utility for unravelling complex brittle tectonic histories within basement volumes. It is also a prerequisite to constrain the dynamic evolution of the petrophysical properties of basement blocks.

Experimental and theoretical evaluation of inclined screws in glued laminated bamboo and timber-concrete composite beams

In the timber-concrete composite beam, the timber beam in tension tends to fail in a brittle manner, which results in insufficient utilization of material strength in the compression zone and significant deformation problems. To improve the mechanical performance of the weak sections in the composite beam, a novel type of glued laminated bamboo and timber (GLBT)-concrete composite beam is proposed in which the bamboo layers are placed in the tension and compression zones of the beam. In this paper, thirty-six shear experiments were conducted to investigate the shear behavior of inclined screws in GLBT-concrete composite beams. The test results showed that the failure modes of diagonally positioned screws in GLBT-concrete composite beams involved pull-out failure of the screw and cone expulsion failure of the concrete. The pure tensile-shear loaded screws experienced the pull-out failure and single-hinge bending failure. For bamboo thicknesses of 30, 60, and 300 mm, the shear capacity of diagonally positioned screws increased by 27.9 %, 34.7 %, and 40.7 %, respectively, compared to the screws in pure wood members. Besides, the shear stiffness was improved by 40.4 %, 78.1 %, and 88.7 %, respectively. It was found that as bamboo thickness increased, the shear capacity and stiffness of diagonally positioned screws gradually improved, although the rate of increase gradually diminished. Among the four types of embedding methods, the ±45° diagonal screw connectors exhibited the highest shear stiffness, while the 135° unidirectional inclined screws (pure compressive-shear screws) had the lowest shear capacity and stiffness. This paper presented a theoretical model for estimating the shear capacity of inclined screw connectors in GLBT-concrete composite beams, which considered the various stress distributions of the screw connectors embedded in bamboo and timber layers.

Effect of cell diameter variations on the mechanical behavior of aluminum foams: Experiments and modeling

Aluminum foams can be manufactured in a variety of cell sizes; however, existing models focus primarily on density and neglect the effect of cell size. Furthermore, aluminum foams with different cell diameters exhibit diverse mechanical properties. In this study, a quasi-static/dynamic compression test was performed to investigate the mechanical behavior, damage patterns, and damage mechanisms of aluminum foams with different cell diameters. The results demonstrate that the compressive properties of aluminum foams undergo significant changes. As the cell diameter increases, normalized initial damage stress and Young's modulus also increase, leading to enhanced energy absorption. However, this increase in cell diameter negatively affects the energy absorption efficiency, resulting in increased instabilities. A finite element analysis was conducted using the LS-DYNA finite element software to investigate the behavior of aluminum foils under all the experimentally tested loading regimes. The simulation results reveal that the deformation zone formed due to collapse diminishes with increasing cell diameter. More importantly, a new damage mechanism named central cell cleavage was reported, which increased the energy absorption capacity and amplified the instability during deformation. This study offers novel insights into the mechanical behaviors exhibited by aluminum foams, thereby facilitating their application in structural engineering.

Analysis of cutting tool geometry induced machining response, surface integrity and anisotropy relation of additively manufactured 316L stainless steel

Although the machining responses of additively manufactured (AM) materials generally differ from wrought materials due to their microstructural properties, there is no study examining the effects of varying cutting tool rake angles in the machining of AM 316L stainless steel material. The aim of this paper is to evaluate the effects of machining using varying cutting tool rake angles and cutting speeds on the cutting response in terms of cutting force, tool wear, chip morphology and surface integrity characteristics such as microstructure, micro-hardness and x-ray diffraction (XRD) analysis of powder bed fusion – laser beam (PBF-LB) 316L. The effect of the tool rake angle on the anisotropic structure of the material was revealed by examining the machining-induced affected layer from both the built and scan planes and by comparing it with the wrought material. The findings showed that PBF-LB 316L behaves more abrasively than the wrought, creating higher cutting force and tool wear due to the differences in the friction coefficient and thermal conductivity of the materials. Although the machining-induced affected layer is not the same in the built and scan planes of the PBF-LB material due to anisotropy, it is considerably higher compared to the wrought material, especially at negative rake angles. While the hardness of PBF-LB material is higher at a low cutting speed and negative rake angle, the hardening capacity of wrought material is higher at high cutting speed and negative rake angle. PBF-LB chips have repeated adiabatic shear bands and the secondary deformation zone is more evident in wrought chips.

Non-uniform microstructure evolution rules and mechanisms of Ti55 alloy with initial basket-weave structure during electrically-assisted V bending

Electrically assisted V-bending (EAVB) experiments of Ti55 alloy sheets with initial basketweave structure were carried out at effective current densities of 3–5A/mm2. The history of temperature field, microstructure patterns and mechanical properties were characterized by IR imaging, OM, EBSD and hardness tests. The results show that α lamellae continuously decrease in thickness (from 2.38 μm to 0.64 μm) with increasing current density. The microstructure patterns of the three deformation zones are significantly different due to different deformation mode and electro-thermo-mechanical routes. Due to limited plastic strain, the orientation rotation and shear fracture of the α lamellae are restricted in the neutral layer, while the ones in the inner and outer layers are refined and become more uniform at mild current density. With increasing current density, the main deformation mode of α grains in the inner layer is {1010} prismatic slip and dynamic spheroidization/recrystallization tends to occur at α lamellae with <0110>α//TD orientation. In the neural and outer layer, intense local Joule heat effect induces α→β→α′ phase transformation in “hot spots”, leading to massive growth of 3 variant needle-like α′, intensified heterogeneous micro-deformation and significant strengthening effect. The combined effects of local Joule heat, residual α phase and deformation-induced defect nucleation break the strict Burgers orientation relationship between α/α’ lamellae and β matrix during EAVB and subsequent cooling process.

Numerical study of time-dependent stresses in the floor of the stope with powered support

When sections of the powered support are clamped in the stope, one of the ways to move them is to explode the rock under them. In the case when there is outburst-prone sandstone in the seam floor, blasting operations becomes dangerous and it is necessary to study the stress field in the host rocks. In this work, a numerical study of the time-dependent stress field in the floor of the stope with powered support is performed. Distributions of values of geomechanical parameters characterizing the stress field and zones of inelastic deformations at different time steps are given. Graphs of changes in these parameters in the floor of the stope are plotted. The minimum time for unloading sandstone at the place of drilling the hole for explosive charge is calculated. It is shown that in front of the mine face plane, the sandstone in the seam floor is in a uniform compressed state; all components of the stress field are close to unity. However, they start to decrease already 2.5 m before the mine face plane. At the hole drilling site, the maximum stress is 0.77γH, the minimum stress is 0.35γH at a depth of 1 m for given conditions.

Development of TRIP phenomenon using power refining of retained austenite by niobium

AbstractThe illustrations above demonstrate that as the percentage of niobium increases, the grain size decreases, leading to an increase in the stability of transformation induced plasticity steel. This, in turn, results in improved mechanical strength. The optimal volume fraction of retained austenite for a significant transformation induced plasticity effect to occur is reported to be in the range of 10 vol. %–20 vol. %. The volume fraction of retained austenite directly determines the carbon content and grain size of the retained austenite, its two main stabilization factors. The stability of the retained austenite dictates when the strain‐induced martensite transformation (SIMT) occurs during straining of transformation induced plasticity high strength steel. Unstable retained austenite transforms almost immediately upon deformation, increasing work hardening rate and formability during the stamping process. At the appropriate stability of the retained austenite, the Strain‐Induced Martensite Transformation begins only at strain levels beyond those produced during stamping and forming, and the retained austenite is still present in the final part; it can transform into martensite in the event of a crash, providing greater crash energy absorption. The tensile strength level of micro‐alloyed transformation induced plasticity steels may exceed 1 GPa. Grain refinement mechanism is considered as the most applied mechanism used in increasing of steel strength without deterioration of ductility and toughness. Recently, it was proposed that the grain refinement could act positively on promoting the transformation induced plasticity effect of advanced high strength steel through improving the stability of retained austenite. In this research, quenching and partitioning heat treatment technique was applied to four grades of low carbon steel with different percentage of niobium. Then, the effect of niobium on grain refinement has been detected by microstructure observations. Mechanical properties and strain hardening properties of investigated steel have been determined. In addition, by using x‐ray diffraction, as well as a new electric resistance‐based sensor, it was possible to characterize the stability of the retained austenite through the plastic deformation of steel. Grain refinement by using of niobium has a great impact on promoting the stability of retained austenite against the plastic stress at the plastic deformation zone.

Analytical Study of the Reduction of Contact Pressure during Cold Rolling of Thick Strips with a Single Deformation Zone

Analytical Study of the Reduction of Contact Pressure during Cold Rolling of Thick Strips with a Single Deformation Zone

Experimental study on the deterioration of mechanical properties of sandy mudstone under different water-gas interactions

Based on the water-rock-gas coupling test system, the work combined the scanning electron microscope and XTDIC 3D full-field strain measurement system. The Brazilian splitting test was performed on four groups of sandy mudstone specimens under contrast (CO), mash-gas soaking (MS), water-mash gas soaking (WM), and water-soaking (WS) conditions. The tensile strength, deformation failure, and microscopic characteristics of fractures were studied to reveal the deterioration mechanism of the tensile properties of sandy mudstone under water-gas coupling. The results showed that the uniaxial tensile strength of sandy mudstone specimens under the three soaking conditions was less than that of the contrast conditions. Compared with specimens in the CO group, the tensile strength of specimens in MS-WS groups was reduced; the WS group decreased the most. Specimens changed from brittle failure to plastic failure after soaking. The decrease rate in strength after the peak was consistent with the change trend in tensile strength. It led to a larger localized deformation zone of specimens and more obvious displacement. The deformation localization zone of the WS group was the broadest, with the most intense displacement. Besides, stress concentration first occurred in the submerged part of the WM group. Fractures expanded in the direction of maximum principal strain. The internal pore structure of sandy mudstone specimens in each group changed after soaking. The average porosity, maximum pore area, and probability entropy of specimens in WS-MS groups increased compared to the CO group. The WS group had the largest reduction and the MS group had the smallest. The pre-peak energy storage capacity of sandy mudstone specimens was gradually weakened. Compared with the CO group, that in the WS-MS groups was reduced. The WS group had the greatest reduction, and the MS group had the smallest. The deterioration effect of water on the interior of sandy mudstone was stronger than that of gas. The work is of great significance for understanding the stability of coal and rocks in closed-pit high-gas mines.

Reconstructing the Evolution of Foreland Fold‐And‐Thrust Belts Using U‐Pb Calcite Dating: An Integrated Case‐Study From the Easternmost Jura Mountains (Switzerland)

AbstractThis case‐study from the Jura Mountains in the foreland of the European Alps demonstrates how the coupling of subsurface analysis and U‐Pb carbonate dating can provide absolute timing constraints and shortening rate estimates of fold‐and‐thrust belts. It is confirmed that the initial Late Cenozoic foreland deformation driving the formation of the easternmost Jura Mountains in Switzerland was predominately thin‐skinned with contractional deformation largely restricted to the Mesozoic succession above a sub‐horizontal basal décollement. Thereby, the localization and structural style of related deformation structures was strongly guided by the characteristics of underlying Late Paleozoic half grabens. The main thin‐skinned thrust front formed at ∼12 Ma, followed by further deformation in the hinterland and locally continued foreland‐directed thrust propagation. The major deformation zones exposed at surface were established at ∼8 Ma but shortening continued until at least ∼4 Ma. Thick‐skinned contraction associated with the inversion of basement structures only played a subordinate role during the latest deformation phase after 8 Ma. Based on cumulative shortening values derived from balanced cross sections, our U‐Pb ages of syn‐tectonic calcite slickenfibres allow to estimate thin‐skinned deformation rates for the easternmost Jura Mountains between ∼0.9 and ∼0.1 mm/year, decreasing toward the eastern tip of the arcuate belt. Moreover, deformation rates seemingly decreased over time with rates of initial thin‐skinned thrusting being significantly higher than the later deformation north of the main thrust front. These new findings from a classical foreland setting highlight the potential of integrating U‐Pb dating in regional fold‐and‐thrust belt investigations elsewhere.

Microstructure evolution and mechanical analysis of lithium battery electrode in calendering deformation zone

Microstructure evolution and mechanical analysis of lithium battery electrode in calendering deformation zone

Geomorphic signatures of neotectonic activity along the Western Andean Front in the Chilean Andes (35°S to 37°S)

AbstractCharacterizing neotectonic activity along mountain fronts in active orogens is the key to better understanding trajectories of landscape evolution, climatic‐tectonic couplings and natural hazards. One such prominent mountain front is the Western Andean Front (WAF), which defines the boundary between two main physiographic units along the Chilean Andes (15°S to 39°S): the Central Depression and Principal Cordillera. This study analyses the geomorphic imprints of neotectonic fault activity in the WAF between 35°S and 37°S. We used several topographic metrics, including the mountain‐front sinuosity index (Smf), the valley floor width‐to‐height ratio (Vf) and the stream length‐gradient (SL) index to gain information about the regional distribution of deformation patterns and its relative tectonic activity for distinctive segments. In addition, a raster map combining rock strength (RS) and mean annual precipitation (MAP) allowed discriminating lithology‐climate vs. tectonics influence on SL anomalies from catchments spanning from the main deformation zone to the regional drainage divide. We use the local relief and swath profiles to quantify the incision and transient state of mountain fronts to evaluate the geomorphic response to tectonic and/or climatic input. Our analysis highlights significant variations from north to south, delineating two distinct segments with different topographic, geomorphic and geometric fault characteristics. These segments are indented at approximately 36°S. From north to south, there is a segment with an inactive thrust front with a primarily climate‐driven fluvial response over long timescales and a second segment with a transient state adjusting to relatively high uplift rates. Morphometric data analysis, DEM‐based morpho‐structural maps, geological maps and previous research support the interpretation of two sets of neotectonic faults: (1) NNE‐striking reverse faults with a dextral slip component and (2) NW‐striking sinistral slip faults, likely a response to deformation partitioning caused by oblique subduction on a continental margin.

A case study on the stability of a big underground powerhouse cavern cut by an interlayer shear zone in the China Baihetan hydropower plant

AbstractThe big underground powerhouse cavern of the China Baihetan hydropower plant is 438 m long, 34 m wide, and 88.7 m high. It is cut by a weak interlayer shear zone and its high sidewall poses a huge stability problem. This paper reports our successful solution of this problem through numerical simulations and a replacement‐tunnel scheme in the detailed design stage and close site monitoring in the excavation stage. Particularly, in the detail design stage, mechanical parameters of the shear zone were carefully determined through laboratory experiments and site tests. Then, deformation of the surrounding rocks and the shear zone under high in situ stress conditions was predicted using 3 Dimensional Distinct Element Code (3DEC). Subsequently, a replacement‐tunnel scheme was proposed for the treatment on the shear zone to prevent severe unloading relaxation of surrounding rocks. In the construction period, excavation responses were closely monitored on deformations of surrounding rocks and the shear zone. The effect of local cracking in the replacement tunnels on sidewall stability was evaluated using the strength reduction method. These monitoring results were compared with the predicted numerical simulation in the detailed design stage. It is found that the shear zone greatly modified the deformation mode of the cavern surrounding rocks. Without any treatment, rock mass deformation on the downstream sidewall was larger than 125 mm and the shearing deformation of the shear zone was 60–70 mm. These preset replacement tunnels can reduce not only the unloading and relaxation of rock masses but also the maximum shearing deformation of the shear zone by 10–20 mm. The predictions by numerical simulation were in good agreement with the monitoring results. The proposed tunnel‐replacement scheme can not only restrain the shear zone deformation but also enhance the safety of surrounding rocks and concrete tunnels. This design procedure offers a good reference for interaction between a big underground cavern and a weak layer zone in the future.

Thermodynamic conditions of granitization and metamorphism of rocks in the northwestern part of the Ukrainian shield

Thermodynamic conditions of granitization and metamorphism of rocks in the northwestern part of the Ukrainian shield