Deformation Plateau Research Articles

Mechanical performance and prediction of a novel reinforced octagonal honeycomb

Honeycomb structures are widely used in various engineering applications due to their lightweight and excellent energy absorption capabilities. Materials with two plateau stress regions exhibit unique advantages in multi-stage energy dissipation and multi-task applications. This paper presents a reinforced octagonal honeycomb structure (ROHC) inspired by the topology of an octagonal tensegrity structures. The paper demonstrates the phenomenon of two plateau deformation stages through the 3D printing of ROHC specimens and finite element simulation. By adjusting three geometric parameters of ROHC (angle α, length ratio r, and thickness t of internal reinforcement), the paper obtains the influence laws on the first and second plateau stress and strain, and proves the controllability of two-stage mechanical performance of ROHC. Based on deep learning technology, a performance prediction model for ROHC's two-stage mechanical performance is proposed, with the MSE and R values confirming the accuracy of the prediction model. Based on the prediction model, a rapid reverse design method is proposed, capable of designing structures with expected two-stage mechanical performance, with errors <7.25 %. The proposed honeycomb structure with predictable and reversible design has significant research value in fields with multi-stage energy absorption and crash protection requirements.

The influence of alien dislocations on the plasticity of [formula omitted]-axis Mg single crystals under tension and compression

Uniaxial tension and compression tests were conducted on as-grown [0001] Mg single crystals and on [0001] single crystals containing an alien distribution of basal dislocations to elucidate their effect on the deformation mechanisms and strain hardening. During tensile deformation, the basal dislocations induce elasto-plastic transition and micro-yielding that precede the gross deformation by twinning. They decrease the stress for twin nucleation, the tensile strength, and the failure strain compared to the virgin single crystals. The weakening of the microstructure and early failure are attributed to the higher density of micro cracks formed in the crystals with alien basal dislocations. The extraneous basal dislocations alter entirely the deformation mechanisms and strain hardening characteristic of [0001] single crystals under compression. They suppress the pyramidal slip as a dominant deformation mode and promote the gross deformation by cooperative basal slip and twinning during extended deformation plateau. The deformation twinning is of anomalous type, nucleating and propagating with the assistance of extraneous basal dislocations at the negative Schmid Factor and against the imposed compressive strain. τtw≈2.1±0.2MPa is found as the basal slip-assisted twinning stress in Mg.

Illite K‐Ar Dating of the Leibo Fault Zone, Southeastern Margin of the Tibetan Plateau: Implications for the Quasi‐Synchronous Far‐Field Tectonic Response to the India‐Asia Collision

AbstractWhether tectonic strain from the early stage India‐Asia collision has synchronously affected the far‐field margin of the Tibetan Plateau is crucial for understanding plateau deformation and growth processes. However, direct evidence for early far‐field deformation remains scarce. Utilizing illite K‐Ar dating of three fault gouge samples, we established the faulting history of the Leibo fault zone (LFZ) at the southeastern margin of the Tibetan Plateau (SEMTP). Consistent authigenic illite ages of 52 ± 2, 54 ± 12 and 55 ± 6 Ma suggest the reactivated thrust faulting of the LFZ in the Early Cenozoic. Positioned ∼700 km east of the collisional boundary and at the intersection of three blocks with distinct lithospheric rheology in strength/viscosity, this event suggests a quasi‐synchronous far‐field tectonic response in the SEMTP to the India‐Asia collision.

Seismic Reflection Imaging of a Deep‐Penetrating Red River Fault in the Yinggehai Basin, Northwest of the South China Sea

AbstractThe Yinggehai Basin (YB) in the northwest of the South China Sea (SCS) has preserved the complete evolution of the Red River Fault (RRF), whose motion over time has largely contributed to shaping the current tectonic framework of the southeastern Tibetan Plateau and Indochina Block. Here we, for the first time, image the RRF, crustal architecture, and crust‐mantle boundary (i.e., Moho) in detail under the YB from two high‐resolution 40‐km‐depth seismic reflection pre‐stack migration profiles. Our seismic reflection images provide direct seismic evidence to support a deep‐penetrating RRF, most likely crosscutting the Moho. In this sense, the RRF was a large‐scale shear zone, along with the clockwise rotation of the Indochina Block, to accommodate the Indochina Block extrusion during Oligocene‐early Miocene and form the YB. We highlight that the material extrusion along deep‐penetrating faults dominated the Tibetan Plateau deformation in response to the India‐Asia collision at an early stage.

Eocene–Miocene tectonic reworking of the southeastern Tibetan Plateau: Geochronological and geochemical records from granitoids along the Ailao Shan–Red River Shear Zone

The convergence of the Indian Plate and Eurasia shaped the Earth’s broadest and highest-elevation collisional system and topographic growth, which is not simply illustrated by ongoing contractional deformation. The Cenozoic magmatism along the Ailao Shan-Red River Shear Zone (ARSZ), linking surface geology with deep lithospheric processes, provides additional information regarding the age and progressive deformation of the India-Asia collision. In this study, we present new zircon U–Pb geochronological, elemental geochemical and zircon Hf isotopic data for the Eocene–Miocene granitoid to resolve the southeastern Tibetan Plateau deformation history. The Jinping granitoids in the southern ARSZ were dated at 37.5–33.6 Ma. They show similar geochemical characteristics (whole-rock major oxides, trace element, Sr–Nd–Pb isotopic and zircon in-situ Hf isotopic data) with respect to coeval potassic granitoids in NW Yunnan, suggesting their origination from partial melting of thickened lower crust with additional contribution from enriched mantle-derived magmas. Leucogranite samples within the ARSZ yielded distinctive zircon U–Pb ages of 28.3 Ma and 18.5 Ma. Geochemical features suggest that they were derived from a heterogeneous crustal source consisting of metasediments and metabasites. Our results, along with those previous studies, suggest that the widespread potassic magmatism in the central and southeastern Tibetan Plateau is related to lithospheric mantle upwelling, which resulted in the partial melting of the thickened lower crust and a short-lived crustal extension during a period of decreased convergence rate. Subsequently, the orogenic-scale sinistral strike-slip movement provided shearing heat for generating leucogranites within the shear zones during the late Oligocene–Miocene. The plateau-wide shift in stress reorganization and tectonic reworking led to the lateral extrusion of the SE Tibetan Plateau and its attainment of modern high elevation.

Microstructure and compression properties of semisolid CrCuFeMnNi high-entropy alloys

CrCuFeMnNi high-entropy alloys were investigated for semisolid processing due to their high compositional flexibility. They exhibited a highly globular semisolid microstructure, with small transformed solid globules. The alloys had a mixture of BCC and two FCC phases, with BCC fractions remaining almost constant while the fractions of both FCC phases changed with Cu content. Although the predicted and experimental equilibrium phase fractions differed, measured compositions were close to equilibrium. During semisolid compression, peak stresses decreased, and the deformation plateau increased with liquid fraction. Furthermore, the alloys behaved like a cohesionless granular material.

Soft polyurethane foam reinforced by expanded polystyrene particles: Compression performance, strain rate, and cyclic compression response

AbstractThe incorporation of particles with soft polyurethane (PU) foam aims to mechanically strengthen the PU foam as PU foam falls short of the mechanical expectation of academia and industries. In this study, the expanded polystyrene (EPS) particles are added to soft polyurethane foam, and composite foam with higher mechanical properties is successfully prepared by one‐step foaming process. The results show that under optimal conditions that is, EPS particle size of 0.5 mm and content of 2.5 wt% (EPS‐0.5‐2.5%), the synthesized foam has the smallest bubble pore diameter of 80 μm and has a stress of 0.284 MPa at 75% strain, which is much higher than that of blank polyurethane foam. As a result of a rise in the quantity of EPS particles, the composite PU foam shows a lower dependency on the strain rate. After the multiple cyclic compression test, PU foam exhibits a descending trend on the stress in the deformation plateau region. Besides, the low‐velocity impact test results indicate that the peak contact force of EPS‐0.5‐2.5% is lower than that of the control group by 632 N.

Drop-weight impact responses and energy absorption of lightweight glass fiber reinforced polypropylene composite hierarchical cylindrical structures

A high spike force at the beginning of impact and the load fluctuations caused by unstable plateau deformation are disadvantages to avoid for impact resistance structures. Lightweight glass fiber-reinforced polypropylene composite hierarchical cylindrical structures (namely GFRP-CHCS, with a relative density of less than 0.1) have the potential to achieve low initial force and high crushing force efficiency under dynamic conditions. This work explores the drop-weight impact behaviors and energy absorption capacity of GFRP-CHCS. Deformation modes, failure conditions, and impact load history responses are discussed. Results showed that GFRP-CHCS has no initial load peak and achieves gentle response curves under the low-velocity impact when the load speed is less than 10 m/s. Among the experiments where the impact energy was beyond the range of static energy absorption, more than 94% of the impact energy was absorbed or dissipated when the impact energy ranged from 200 J to 300 J. After unloaded, GFRP-CHCS maintained good integrality and recovered a significant deformation which was over 93% initial structural height. With ideal isotropic material properties, numerical and theoretical predictions were conducted regarding the loading velocity effects on structural deformation mode and mean impact response force. This work utilized a thermoplastic composite consisting of GFRP face sheets and polypropylene core. The results have reference significance for the anti-impact design of thermoplastic composite hierarchical structures.

Braided GFRP sleeving reinforced curved laminated bamboo beams: An efficient way to attenuate delamination

For curved laminated bamboo beams, delamination greatly attenuates their load carrying capacity and ductility. In this study, glass fiber reinforced polymer sleeving (GFRPS) was applied to strengthen the laminated bamboo arch (LBA), forming a new composite bamboo structure. Three-point bending experiments were carried out to investigate the deformation and failure behaviors. It is found that the GFRPS effectively restrains the delamination and forms a plastic hinge at the vault after the peak load, which greatly enhances the load carrying capacity and results in a long deformation Plateau I (Plateau I is a plateau segment where the load P is greater than the average peak load (50.82 kN) of group BAH). Plateau I is elongated over 29.6 times by the GFRPS, indicating that GFRPS reinforced LBA becomes ductile. The peak load can be improved by 32.8% while the load of the second Plateau II (Plateau II is a common ductility plateau in ductile materials) is enhanced by 62.1%. The curved composite beam exhibits superior ductility and energy dissipation. Reaching 110 mm for the displacement, the average energy dissipation of the composite LBA could be 87.13% higher than that of the LBA.

Assessment of the deformation model of the proximal tibia in the course of degenerative disease: analysis of the 3-dimensional mathematical model

BackgroundThe high tibial osteotomy (HTO) is an effective knee-saving procedure, which relieves arthritis symptoms and prolongs the life of the knee joint. This procedure requires detailed preoperative planning. Usually, the contralateral side is used as a template for this purpose. Some intra-operative complications made us thinking how exactly the degenerative disease alter the epiphysis if the tibia. Our study aimed to assess morphological differences between healthy knees and degenerative knees using a three-dimensional mathematical model.MethodsTwenty-three computed tomography (CT) examinations were collected out of 237 individuals screened for inclusion/exclusion. The inclusion criteria were: age between 40 and 69 years, degenerative knees with visible varus deformation, and signs of radiological osteoarthritis (OA) in the knee joint (such as joint space narrowing, subchondral sclerosis, subchondral cyst formation, and osteophytes. The average age of the included patients was 56.2 years. Nine men’s and 14 women’s knee joints were used for the calculation and comparisons.ResultsFemale varus knees showed much more significant variability in tibial plateau dimensions according to sides of the body than male ones. These differences were statistically significant (P=0.03). In comparison between the basal bone and bones with OA, variability in 3D dimensions was statistically significant only for lateral condyles in males’ right knees (P=0.025). Compared to the degenerative knees to the most average, healthy knees, there were significant differences in the measured surface area of males’ right knees for both condyles: for the medial P=0.0046, for lateral P=0.005. Male varus knees had a statistically more considerable (P=0.028) surface area for all measured condyles. Angles of inclination differ significantly between knees with OA and healthy knees in the male population for the medial condyle plateau in the left knees. The female population for the lateral condyle in left knees and the medial condyle in right knees.ConclusionsThe proximal tibial plateau deformation showed high variability in the two-dimensional and three-dimensional analysis in the designed mathematical models. This finding must be considered during preoperative planning.

In-Plane Interactive Buckling of High Strength Steel Welded Wide Web I-Section Beam-Columns

A numerical investigation on the overall-local interactive buckling performance of high strength steel (HSS) wide web I-section members was conducted using finite element (FE) models verified against experimental data. The effect of overall slenderness, the height-thickness ratio of the web h w / t w , and the width-thickness ratio of the flanges (bf/tf) on ultimate load was parametrically analyzed. The result demonstrated that (i) for the beam-columns with higher steel grade, the Pz-Uz curve presents a relatively obvious deformation plateau, meaning a certain degree of ductility. (ii) The ultimate load decreased essentially linearly resulting from higher h w / t w , and the trend was graphically consistent under various steel grades. (iii) bf/tf lower than 0.6 led to the failure mode of shearing buckling, and the corresponding ultimate load increased with an increase of bf/tf. In the case of bf/tf greater than 0.6, the ultimate load decreased as a result of the higher bf/tf. Based on the concept of the direct strength method, the local postbuckling strength prediction formula was fitted with stub beam-column FE results and examined with experiment data. The correlation formula of compression and bending moment was proposed to evaluate the resistance of the interactive buckling of the HSS wide web I-section underpinned by the FE results of beam-columns with intermediate length and experiment data.

Three-dimensional finite element modelling on strain localization around the Mabian earthquake swarm, Sichuan Province

SUMMARYThe Mabian fault zone, distanced ∼200 km to the east of the Xianshuihe–Xiaojiang fault system, is located in the western vicinity of the relatively stable South China Block. Since 1917, about 54 M &amp;gt; 4.7 earthquakes, including the 1974 Ms = 7.1 Mabian event have occurred around this fault zone, suggesting that significant strain is localized within the Mabian fault zone. Here, we built a 3-D finite element model to investigate the main parameters that possibly control strain localization around the Mabian fault zone averaged over the active deformation timescale. In the model, the Xianshuihe–Xiaojiang fault system is specified as a discontinuous contact interface for its motion governed by a Coulomb-friction law, and the crustal rheology is simplified as a frictional upper crust underlain by a viscoelastic lower crust. In addition, global positioning system (GPS) data are used to mimic the horizontal tectonic loading, and the model base is supported by a hydrostatic pressure. Numerical results show that with the weak fault strength and the low viscosity contrast between the Tibetan plateau and the South China Block, strain rates from motion of the southeastern Tibetan plateau could be propagated across the Xianshuihe–Xiaojiang fault system more widely within the Mabian fault zone. Constrained by the estimates on slip rates of the faults and on rheological structures of the crust, our optimal model predicts the effective friction coefficient of the Xianshuihe–Xiaojiang fault of 0.05–0.1. Under this condition, relative motion across the Xianshuihe–Xiaojiang fault system is largely partitioned by the geometric bend near the central portion of the fault system, resulting in a relatively high strain rate of 2.1–3×10–8 yr–1 accumulating around the Mabian fault zone. Keeping the weak strength of the fault, numerical results also show that if the central portion of the Xianshuihe–Xiaojiang fault system follows the Daliangshan fault, strain accumulation around the Mabian fault zone could be significantly reduced. It thus can be concluded that the strain partitioning from the weak strength and the special geometry of the Xianshuihe–Xiaojiang fault system must play a crucial role in active deformation around the Mabian area out of the Tibetan plateau deformation domain. This in turn means that in the Xianshuihe–Xiaojiang fault system, the Anninghe–Zemuhe fault is still the main boundary between the southeastern Tibetan plateau and the South China Block.

Statistical analysis for cost effective process parameters and localized strain hardening behavior of Al-7050 foam

Cost effective process parameters of fabricating Al-7050 foam were obtained by reducing amount of blowing agent and processing time in advancement of low cost, low density and high mechanical properties for structural applications. Quasi-static compressive properties and localized plateau deformation behavior were studied. Maximum strength to density ratio up to 40.38 MPa/(gm/cm3) with utilizing 0.2 wt% TiH2 was achieved. Localized brittleness of plateau cell walls were observed by localized strain hardening behavior in plateau deformation.

Eocene Rotation of the Northeastern Central Tibetan Plateau Indicating Stepwise Compressions and Eastward Extrusions

AbstractWhen and how the TP underwent uplift and deformation are still under heated debate. We present paleomagnetic evidence for the NB in the northeastern central TP to help decipher the potential plateau deformation mechanism. Magnetostratigraphy with zircon U‐Pb age of volcanic rock demonstrates that the NB basin deposited during 52.5–35.0 Ma. Paleomagnetic declinations indicate that the basin experienced counterclockwise rotation of 25.9 ± 7.2° during 52–46 Ma and clockwise rotation of 24.4 ± 9.7° during 41–35 Ma, which coexisted with the intrusion and explosion of volcanic rocks at 51–46 and 39–35 Ma. We proposed a stepwise compression and extrusion model to interpret the basin deposition, rotation, and volcanism by northward compression and eastward extrusion of the eastern Lhasa and Qiangtang Blocks (Proto‐TP) in relation to the Sichuan Basin as early response to the India‐Asia collision.

Axial compression deformability and energy absorption of hierarchical thermoplastic composite honeycomb graded structures

Thermoplastic composites have advantages of high damage tolerance, reprocessing and recycling capacities which are in growing demand in lightweight engineering applications. Structural gradient were introduced to designed continuous woven glass fiber reinforced hierarchical thermoplastic composite honeycomb graded structures (HTCHGS) aim to improve on deformation stability and induce the failure processes. Axial compression tests were conducted to investigate compression behavior, energy absorption capacity and influence of structural gradient distributions. Experimental observation showed that failure of HTCHGS was induced and constrained as expected, stable rising load plateau achieved by presented staggered conical HTCHGS. The staggered conical HTCHGS obtained mean value of 0.64 and 1.56 J/g on crushing force efficiency and specific energy absorption at the densification displacement. FEM simulations were carried out among presented configurations by parameterized modeling, validated the induced deformation processes by structural gradient which matched well with the tests. Stress distributions were compared among six configurations at typical deformation stage, found core components of staggered configurations contribute more to energy absorption than that of regular configurations. Staggered dumbbell HTCHGS provide long and stable deformation plateau till densification, and staggered conical HTCHGS are considered as optimal energy absorbing components among the configurations which give possible guidance for engineering structural designs.

Compressive behavior of stretched and composite microlattice metamaterial for energy absorption applications

A new proposed truss lattice metamaterial is introduced and compared with the conventional octet truss lattice (OTL) material with regards to specific energy absorption (SEA) and energy absorption efficiency (EAE). The proposed lattice architecture resembles the Face-Centered Cubic (FCC) metamaterial with a mesostructural unit cell with an aspect ratio of 1:1:2, referred to as the stretched cell lattice (SCL). SCL and OTL samples were fabricated from stainless steel 316L by selective laser melting (SLM). Quasi-static compression experiments on the SLM fabricated metamaterials revealed an unstable twisting deformation mode for the SCL, whereas a stable crushing behavior was observed for the OTL. SCL samples provided higher SEA and EAE than OTL by 26% and 17%, respectively. Additionally, it was shown analytically, numerically and experimentally that the yield strength of the proposed SCL is ~80% higher than that of the OTL metamaterials of the same base material and relative density. A hybrid composite lattice structure based on acrylic matrix and the additively manufactured microlattice metamaterials was produced to enhance the struts buckling resistance. The hybrid composite showed a 47% higher specific strength while the SEA and EAE dropped by 31.5% and 30.7%, respectively, when compared to the bare stainless steel microlattice. Dynamic compression experiments using Split Hopkinson Pressure Bar (SHPB) at strain rates in the order of 103/s demonstrated a similar deformation plateau as the static compression experiments with a dynamic increase factor (DIF) of ~1.3 for the bare stainless steel metamaterials and ~2 for the acrylic-stainless steel hybrid composite material.

Simulation of localized compaction in Tuffeau de Maastricht based on evidence from X-ray tomography

Deformation experiments with concurrent X-ray microtomography are used to characterize the mechanical properties of a high-porosity carbonate rock from Central Europe (the Tuffeau de Maastricht). Evidence of deformation behavior and pressure-dependent strain localization for this rock are taken into account to define the parameters of an elastoplastic constitutive law with competing hardening and softening mechanisms. Full-field data regarding the compaction localization regime have been used to identify a compromise between compaction hardening and structure deterioration. It was shown that by placing emphasis on the destructuration behavior it was possible to reproduce features such as the elongation of the deformation plateau emerging during compaction band formation, as well as the pressure-dependent inclination of the ensuing compaction bands. Most notably, the comparison between measurements and simulations showed that the strategy here used to constrain the model parameters allows a satisfactory depiction of both the macroscopic deformations and the portion of sample volume across which the compaction zones develop and propagate. These results point out the major benefits of parameter calibration strategies accounting synergistically for global measurements and spatially-distributed deformations, especially in the presence of constitutive laws meant to replicate compaction localization.

New formulation of nonlinear kinematic hardening model, Part II: Cyclic hardening/softening and ratcheting

The second part of the study presents development of the Dirac delta functions framework to modelling of cyclic hardening and softening of material during cyclic loading conditions for the investigated in Part I low carbon S355J2 steel. A new criterion of plastic strain range change is formulated. This provides more certainty in the cyclic plasticity modelling framework compared to classical plastic strain memorization modelling. Two hardening parameters from the developed kinematic hardening rule are written as functions of both plastic strain range and previously accumulated plastic strain. This representation of hardening parameters is able to accurately match experimental results with different types of loading programs including random loading conditions and considering initial monotonic behaviour with yield plateau deformation. Ratcheting behaviour is simulated by the developed cyclic plasticity framework by considering an approximated form of the Dirac delta function for modelling the deviation effect and introducing an additional supersurface for better prediction of ratcheting rate. The proposed cyclic plasticity model requires up to 21 material constants, depending on application. A clear and straightforward calibration procedure, where sets of material constants are determined for each plasticity phenomenon considered, is presented. Application of the model to different materials under various tension-compression and non-proportional axial-torsion cycles shows very close agreement with test results.

New formulation of nonlinear kinematic hardening model, Part I: A Dirac delta function approach

A new mathematical modelling framework for simulation of metal cyclic plasticity is proposed and experimental validation based on tension-compression cyclic testing of S355J2 low carbon structural steel presented over the two parts of this paper. The advantages and limitations of the stress-strain curve shape modelling given by “Armstrong and Frederick” type hardening rules are discussed and a new formulation for kinematic hardening is proposed for more accurate representation of the stress-strain dependence under cyclic loading conditions. The proposed model is shown to describe the shape of the stress-strain curve accurately under various different loading conditions. Transition effects occurring at loading reversals are incorporated through a new framework of Dirac delta functions. In addition to the yield surface, stress supersurfaces able to expand and instantly move to simulate a shift of stress-strain curves during loading reversals are determined. This also enables inclusion of the behaviour of monotonic stress-strain curves with yield plateau deformation in one mathematical model. The influence of the first stress invariant on the shape of a stress-strain curve in tension and compression directions observed in many metals is incorporated into the kinematic hardening rule. The ability of the model to accurately describe transition from elastic to elastic-plastic deformation at small offset strain yield points naturally accounts for nonlinearity of an unloading stress-strain curve after plastic pre-strain. Development of the model to include mixed cyclic hardening/softening, ratcheting and mean stress relaxation is presented in a companion paper (Part II), which includes experimental validation of the modelling framework.

Turbulent lithosphere deformation in the Tibetan Plateau.

In this work, we show that the Tibetan Plateau deformation demonstrates turbulence-like statistics, e.g., spatial invariance across continuous scales. A dual-power-law behavior is evident to show the existence of two possible conservation laws for the enstrophy-like cascade in the range 500≲r≲2000km and kinetic-energy-like cascade in the range 50≲r≲500km. The measured second-order structure-function scaling exponents ζ(2) are similar to their counterparts in the Fourier scaling exponents observed in the atmosphere, where in the latter case the earth's rotation is relevant. The turbulent statistics observed here for nearly zero-Reynolds-number flow can be interpreted by the geostrophic turbulence theory. Moreover, the intermittency correction is recognized with an intensity close to that of the hydrodynamic turbulence of high-Reynolds-number turbulent flows, implying a universal scaling feature of very different turbulent flows. Our results not only shed new light on the debate regarding the mechanism of the Tibetan Plateau deformation but also lead to new challenges for the geodynamic modeling using Newton or non-Newtonian models because the observed turbulence-like features have to be taken into account.