Primary Deformation Mode Research Articles

Interactions between basal dislocation and [formula omitted] twin boundary in HCP metal: A molecular dynamics study

For hexagonal close-packed (HCP) metals having a c/a<3, basal <a> slip is the most common slip system, and {112̅2} twinning is one of the primary plastic deformation modes when compressive stress is applied along the c-axis. In this work, molecular dynamics simulations have been applied to reveal the interaction mechanism between different basal <a> dislocations and {112̅2} twin boundaries (TBs) in Mg, Zr and α-Ti. When the 000113[112̅0] dislocation interacts with the {112̅2} TB, it is transmuted into a 112̅2-{112̅1} double twin (DT). With increasing shear stress, the growth of the 112̅2-{112̅1} DT is impeded by the other side of the {112̅2} TB, it transmutes into (0001)13<101̅0> dislocations and twin dislocations (TDs). Furthermore, the {112̅1} TB is capable of transforming into a {112̅2} TB and a new co-zone {112̅1} TB, which then forms a twin-twin junction (TTJ) to release stress concentration. When the 000113[21̅1̅0] dislocation interacts with {112̅2} TBs, it transmuted into a I2 SFs in the twin and a TD with one-layer height on the {112̅2} TB. But the 000113[1̅21̅0] dislocation would be impeded by the {112̅2} TB and couldn’t be transmuted further.

Quantitative characterization of Zr60700 alloy plate rolling in different directions based on electron back-scatter diffraction

Fully annealed Zr60700 alloy plates with a thickness of 15 mm were rolled at 15%, 30%, 45%, 60%, and 75% thickness reductions, and the rolling paths were unidirectional rolling (UR) and cross-rolling (CR), respectively. Electron back-scatter diffraction (EBSD) experiments revealed that the texture developed gradually towards the basal texture with increased thickness reduction. Severe orientation hardening enhanced the deformation resistance of the CR sample, resulting in a higher grain size than the UR sample. The plastic deformation during the rolling process was dominated by dislocation slip. The results of the prediction based on the Schmid factor (SF) and the calculation based on the in-grain misorientation axis (IGMA) showed that the prismatic <a> slip was the primary deformation mode in the early stages of the UR and CR processes. With the increase in thickness reduction, the basal <a> and pyramidal <c+a> slip played an increasingly important role. Compared with the UR process, the CR process was more accessible to activate the basal <a> slip and more conducive to forming the basal texture. Mechanical tests showed that the CR samples exhibited higher isotropy than the as-received and UR samples.

Tailoring the microstructure and deformation mechanisms of an additively manufactured nickel-based superalloy by post-aging heat treatment

Laser powder bed fusion (LPBF) is a new method for preparing the nickel-based superalloy hot-end components. This study systematically investigated the microstructural characteristics and mechanical performance of a γ′-strengthened Haynes 230 alloy after solution heat treatment (SHT) and aging heat treatment (AHT). The results indicate that γ′ phases continue to grow as the AHT temperature increases. The volume fraction of γ′ phases increases first and then decreases. The maximum γ′ phase fraction can be achieved at 750 °C. The yield strength (YS) of the AHT samples at 25 °C and 800 °C increases first and then decreases, which is mainly caused by γ′ phase fraction evolution. The SHT+750 sample presents an excellent integration of tensile performance at 25 °C and 800 °C. The primary deformation mode at 25 °C is stacking fault (SF) shearing. The δ precipitation and high-density Lomer-Cottrell (L-C) locks are the primary reasons for the higher work hardening rate of the SHT+850 sample. The transition of the dominant deformation mechanism from SF shearing at 25 °C to Orowan bypassing at 800 °C leads to a dramatic reduction in the YS of the SHT+850 sample.

Research on the anisotropic mechanism of plastic behavior during tensile process of textured pure titanium

The presence of texture has an important influence on the deformation behavior of titanium. In this study, the anisotropy of the macro-mesoscopic deformation behavior of the material and its evolution with strain were systematically studied by uniaxial tensile test and electron backscatter diffraction (EBSD) technique. Based on the above results, the calculation formula of Schmid factor (SF) for each variant of the slip system expressed by the crystal orientation angle was derived, and the influence of initial texture and texture redirection on the activability of each deformation mode was explored. The impact of the ratios between the critical resolved shear stress (CRSS) of the three deformation modes on the predictions of the dominant deformation mode of yield was systematically assessed, using the CRSS as the standard. The initial yield mode of RD tensile is prismatic <a>slip, while TD tensile may be a combination of multiple slip modes. One of the primary reasons of the evolution of the basal split texture components is the activation of dislocation slip, while the twinning mainly plays a role in coordinating the deformation. According the Taylor axis analysis, the prismatic <a> slip is the primary deformation mode during RD and TD tensile, followed by pyramidal <a> slip, while the basal <a> slip is difficult to be activated or the activability decreases with the increase of strain.

Accurate prediction of indicators for engineering failures in complex mining environments

Due to seismic load, complex geological and geo-mechanical conditions of rock mass in Steeply Inclined and Extremely Thick Coal Seam (SIETCS) mines, the prediction and prevention of dynamic disasters remain quite challenging. Traditionally, physical models and numerical simulations are widely practiced for disaster prediction at shallow depths which becomes difficult in SIETCS mines. The drilling tests and above models are generally time-consuming and uneconomic providing miniature coverage. Whilst, rockburst driven disasters require detailed regional geological understanding and mechanical behavior of rock mass. For this purpose, a non-invasive and cost-effective geophysical workflow covering regional-scale geology is introduced for accurate identification and prediction of rockburst in a SIETCS mine of northwestern China. Passive seismological in-situ observations were made for a period of twenty-four months to compute the seismic source parameters, map fracturing process, identify regional lineaments and calculate important rockburst prediction indicators. The spatiotemporal distribution of induced-microseismicity, three-states stress theory, and mapped fractures helped in the identification of three rockbursts, several high-energy tremors, and the prediction of two new rockburst-prone regions. The mapped fractures through the novel ‘Seismo-Frac model’ showed that for the simultaneous excavation in B3 + 6 and B2 + 1 coal seams subjected to repetitive episodes of seismic deformation, the shear-displacement accumulation, prying effects of rock pillar and roof coupled with dynamic stress are the primary mode of deformation. The mapped fractures and lineaments are unevenly distributed in the minefield with a maximum density of the fractures concentrated in the B3 + 6 coal seam and rock pillar. Furthermore, through conditional probability analysis, the prediction efficiency of source parameter averages (E and N), seismological parameters (b-value and Δb), and maximum potential magnitude (Mm) was compared. A sharp-increase in source parameter averages while a sharp-decrease in the seismological parameters proved to be effective rockburst prediction indicators. This study also introduces decreasing occurrence frequency of fractures and lineaments as the new prediction indicators. This method, while a panacea for imaging the entire fracturing phenomenon, provides insights with widespread implications for academic researchers and industry practitioners to mitigate dynamic disasters in global underground engineering excavation.

Deformation behaviors and the related high-temperature mechanical properties of Mg–11Gd–5Y–2Zn–0.7Zr via regulating extrusion temperatures

The effects of extrusion temperatures (430, 450, 470 and 490 °C) on the microstructures and mechanical properties of Mg–11Gd–5Y–2Zn–0.7Zr (GW) alloys at room temperature (RT), 250, 300, 350 °C were systematically investigated. The dynamic precipitation of blocky and lamellar long period stacking ordered (LPSO) phases was taken place during hot extrusion. The dominant texture changed from <10 1¯0 >//ED to <0001>//ED with increasing extrusion temperature. Tensile results indicated that the GW alloy extruded at 430 °C (GW430) exhibited the highest mechanical properties at both RT and elevated temperatures, which was ascribed to the fine dynamic recrystallized (DRXed) grains, un-DRXed grains with an orientation of <10 1¯0 >//ED, and the LPSO phase strengthening. When tensile tested below 300 °C, slips on the blocky LPSO phase and kinks of lamellar LPSO phase were the primary deformation modes, followed by grain boundary crack. At 350 °C, grain boundaries became the vulnerable sites to be activated. For GW alloys extruded at 450, 470 and 490 °C, an abnormal increase of mechanical properties was observed at 300 °C. This was due to the occurrence of multiple-slip, which showed the intersection and entanglement of dislocations and thus improving the strength of Mg matrix.

An Investigation into the Microstructural Response to Flexural Stresses of a Metastable β‐Phase Ti Alloy produced by Blended Elemental Powder Metallurgy

A Ti‐10V‐3Al‐3Fe metastable β Ti alloy is strained under three‐point bending conditions according to the ASTM E290‐14 standard. A combination of electron backscatter diffraction (EBSD) mapping and high‐resolution scanning transmission electron microscopy (STEM) is used to investigate the microstructural response to flexural stress. Results reveal a delayed formation of the deformation products, due to the load‐bearing capacity of the constituent voids. The deformation products are confined in narrow bands on either side of the fracture surface. {332}⟨113⟩ twinning system is identified as the primary deformation mode followed by the formation of α″ martensite both in β matrix and β twins. Accommodation of the microscopic strain arising from the development of α″ structure and β‐twinning triggers the formation of fine deformation‐induced ω plates, which are observed predominantly at the interfacial plane of β/β twin and β/α″, and also in the interior of the β twins.

On the Plasticity and Deformation Mechanisms in Magnesium Crystals

This work presents an overview of the mechanical response and microstructure evolution of specifically oriented pure magnesium single crystals under plane strain compression at room temperature. Crystals of ‘hard’ orientations compressed along the c-axis exhibited limited room temperature ductility, although pyramidal ⟨c + a⟩ slip was readily activated, fracturing along crystallographic 112¯4 planes as a result of highly localized shear. Profuse 101¯2 extension twinning was the primary mode of incipient deformation in the case of orientations favorably aligned for c-axis extension. In both cases of compression along ⟨112¯0⟩ and ⟨101¯0⟩ directions, 101¯2 extension twins completely converted the starting orientations into twin orientations; the subsequent deformation behavior of the differently oriented crystals, however, was remarkably different. The formation of 101¯2 extension twins could not be prevented by the channel-die constraints when c-axis extension was confined. The presence of high angle grain boundaries and, in particular, 101¯2 twin boundaries was found to be a prerequisite for the activation of 101¯1 contraction twinning by providing nucleation sites for the latter. Prismatic slip was not found to operate at room temperature in the case of starting orientations most favorably aligned for prismatic slip; instead, cooperative 101¯2 extension and 101¯1 contraction twinning was activated. A two-stage work hardening behavior was observed in ‘soft’ Mg crystals aligned for single or coplanar basal slip. The higher work hardening in the second stage was attributed to changes in the microstructure rather than the interaction of primary dislocations with forest dislocations.

Nanoindentation characteristics of nanocrystalline tungsten via atomistic simulation

ABSTRACT Molecular dynamics simulations are performed to explore nanoindentation characteristics of tungsten, and the influences of grain size, indenter velocity, indenter size, and temperature are discussed. The results illustrate that the hardness reduces as the grain size (5.00 ∼ 24.62 nm) decreases. There is no phase change observed during the whole deformation process. For monocrystalline W, the dislocation nucleation and propagation dominate the deformation mechanisms. Differently, the primary deformation mode of nanocrystalline W is the grain split and motion of GBs. Dislocations primarily nucleate below the contact surface of the indenter and substrate and then glide in the grain core. The monocrystalline W has better pattern-forming ability than nanocrystalline. Besides, the pattern-forming ability of nanocrystalline W is negatively correlated with the average grain size (5.00 ∼ 24.62 nm). The von Mises stress is mainly concentrated in the interface between the indenter and substrate, the dislocation area for monocrystalline, and grain boundaries for nanocrystalline. The indentation force and hardness are positively correlated with indenter radius size (30 ∼ 80 Å), negatively correlated with temperature (10 ∼ 1500 K), and insensitive to the indenter velocity when velocity is lower than 3.0 Å /ps (300 m/s).

Crack initiation mechanism of a silicide-containing high-strength Ti–5Al-7.5V alloy under low-cycle fatigue loading

In this work, the dual phase titanium alloy Ti–5Al-7.5V was subjected to low-cycle fatigue at room temperature to reveal the deformation mechanisms of fatigue and crack initiation. Transmission electron microscope analysis showed that planar dislocation slip, most of them localized at the basal and prismatic planes of α phase, is the primary deformation mode of low-cycle fatigue. Multiple slips operate concurrently in the high Schmid factor planes within a single grain. Moreover, a limited number of observed microcracks were formed along the basal slip bands. Electron back-scattered diffraction analysis evidenced that numerous microcracks were formed along basal planes. And, the microcracks were confined in primary α grains without propagation to surrounding transformed β matrix, indicating that the alloy exhibits a high tolerance to microcrack propagation. The α grain aggregate oriented for basal slip is a fatigue-critical microstructure configuration, which provides a high Schmid factor path by linking adjacent grains and potentially lead to internal crack initiation with the formation of a field of facets in the cycling process. While the silicides were observed in contact with the microcracks and slip bands, no evidence of crack initiation from silicides was detected. Given that the microcracks were formed along the pre-existing slip bands, it remains an open question whether the silicides can act as the dislocation sources for planar slips and facilitate crack nucleation from these silicides.

Influence of Grain Size and Its Distribution on Charpy Impact Properties of TA3 Alloy

In practice, most components often receive impact loads during service. In order to ensure the service safety of components, impact toughness evaluation is essential. To the best of our knowledge, the previous studies were mainly focused on the quasi-static tensile deformation, and the impact toughness of bimodal grain structured metals have rarely been reported. Three different grain size characteristics TA3 alloy, i.e., fine grained sample (FG Ti), the mixture of coarse and fine grained sample (MG Ti), and coarse grained (CG Ti), were produced, and their tensile and Charpy impact properties were comparatively investigated. Owing to the strengthening of retained β phase and the twining inducing plasticity effect, MG Ti display the highest tensile strength and impact absorbed energy, together with an intermediate tensile elongation. The impact deformed microstructures revealed that the primary deformation modes of FG Ti, MG Ti and CG Ti sample are: dislocation slips, a combination of dislocation slip in fine grained region and {101¯2} deformation twins in coarse grained region, and {112¯1} deformation twins in sequence.

Flow-induced vibration of a circular cylinder with an attached elastic plate of high aspect ratio

The flow-induced transverse vibration of a cylinder (diameter D*) with an attached flexible and elastic plate of high aspect ratio to its leeward side is investigated numerically at a low Reynolds number of 150 for a range of reduced velocities (Ur) using an in-house developed fluid solver based on curvilinear immersed boundary method strongly coupled with an open-source finite element-based structural solver. It was observed that an attached elastic plate of width B=B*/D*=0.1 and length L=L*/D*=1 suppresses large vibrations of the cylinder, but one with length L = 2, contrary to previous studies, amplifies vibrations up to five times of an isolated cylinder. Three regimes were observed: vortex-induced vibration (VIV), suppression, and galloping. In VIV regime for 3≤Ur≤7, lock-in was observed where the vortex shedding frequency from the plate-cylinder system was seen to slightly increase relative to that of static cylinder–plate system to match with the natural frequency of the cylinder and the plate. In this regime, the deformations of the elastic plate were large (max. 91% of L) and in high modes (up to fifth mode), leading to new vortex patterns. The transverse displacement of the cylinder–plate system was found to reach nearly twice of an isolated cylinder in this regime. For 7&amp;lt;Ur≤9, the cylinder–plate system was pushed into suppression regime, wherein its displacement was nullified because of lack of vorticity interaction and out-of-phase deformation. Beyond Ur = 9, the cylinder–plate system vibrated in the galloping regime, wherein it shed and generated forces as an asymmetric body creating an angle of attack with the incoming flow. The primary mode of deformation of the elastic plate progressively increased from second mode to third mode in galloping regime, and the transverse displacement of cylinder showed a linear increase with the increase in reduced velocity until Ur = 18. The vibration amplitude of the cylinder was higher in the galloping regime, but the vibrations of the plate were more intense (higher amplitude and mode) in the VIV regime. New vortex patterns were observed in the VIV and galloping regimes ranging from 2S mode till 2T mode including all the vortex pattern between them like 2S, 2P, 2Q, and P + T modes, which are reported for the first time.

Shock resistance capabilities of nickel crystal containing helium nanobubbles

It has been revealed in previous studies that helium bubbles have a damaging consequence on the load bearing capabilities of nickel. Shock resistance is the key characteristic of structural materials used in the construction of a nuclear reactor. Herein, atomistic simulations were performed to study the dynamic shock resistance capabilities of single crystal Ni impregnated with helium bubble. The effect of the geometrical configuration of helium bubble on a nickel crystal, which acts as a substrate in which the bubble is lodged, when subjected to shock loading, was studied. It was concluded from the atomistic simulations that the presence of helium bubble with a higher concentration of helium atom leads to a reflection of shock front energy from the shock path. The diameter of the helium bubble at the same concentration of He (the ratio of He atoms to the vacancy created by deleting Ni atoms) is less critical for the shock resistance capabilities of Ni crystal. At lower values of shock impact, the deformation is mainly controlled by dislocation emission, whereas at higher impact velocities, the phase transformation from FCC to BCC is the primary mode of deformation. The analysis presented in this article will help in elucidating the shock resistant capabilities of Ni facing challenges of transmutation.

Deformation mechanism and cyclic stress response of Zircaloy-4 alloy cladding tube during low cycle fatigue at room temperature

This work systematically investigated the deformation mechanism and cyclic stress response behavior of Zircaloy-4 alloy cladding tube at room temperature. Low cyclic fatigue tests revealed that cyclic softening and hardening strongly depend on the applied strain amplitude. Besides, prismatic < a > slip was the primary cyclic deformation mode when the value of plastic strain amplitude less than that of elastic strain amplitude, otherwise prismatic < a > slip and {101¯2} <1¯011 > twinning dominated the deformation. Due to the combination effect of grain rotation, dislocation accumulation and twinning, cyclic softening, saturation and hardening behaviors were presented in Zircaloy-4 alloy.

Regularization of shear banding and prediction of size effects in manufacturing operations: A micromorphic plasticity explicit scheme

Good quality manufacturing operation simulations are essential to obtain reliable numerical predictions of the processes. In many cases, it is possible to observe that the deformation localizes in narrow areas, and since the primary deformation mode is under shear, these areas are called shear bands. In classical continuum mechanics models, the deformation localization may lead to spurious mesh dependency if the material locally experiences thermal or plastic strain softening. One option to regularize such a non-physical behavior is to resort to non-local continuum mechanics theories. This paper adopts a scalar micromorphic approach, which includes a characteristic length scale in the constitutive framework to enforce the plastic strain gradient theory to regularize the solution. Since many manufacturing process simulations are often assessed through finite element methods with an explicit solver to facilitate convergence, we present an original model formulation and procedure for the implementation of the micromorphic continuum in an explicit finite element code. The approach is illustrated in the case of the VPS explicit solver from ESI GROUP. According to the original formulation, we propose an easy way to implement a scalar micromorphic approach by taking advantage of an analogy with the thermal balance equation. The numerical implementation is verified against the analytical solution of a semi-infinite glide problem. Finally, the correctness of the method is addressed by successfully predicting size effects both in a cutting and a bending tests.

Investigation of the cutting force response to a PDC cutter in rock using the discrete element method

In the drilling industry, Polycrystalline Diamond Compact (PDC) bits with multiple fixed PDC cutters are widely applied to cut rock under high bottom hole pressure and high temperature. The bit-rock interaction is the main excitation source of drill string vibrations and needs to be understood and controlled better to improve the performance of the drilling process. Rock cutting mechanisms can be examined best for a single PDC cutter: Limitations of dynamic control and available sensors in experimental setups are eliminated in numerical simulations. Using the Discrete Element Method (DEM), deformation and strength of rock can be modeled through its full degradation in the PDC cutting process under typical environmental conditions. Stresses and strains in the rock material and on the cutter faces become available for examination.In this paper, numerical simulations of the cutting process are conducted using a modified bonded-particle model (specialized DEM), which is calibrated to a pressure series of high-strain triaxial laboratory tests. The simulation results are interpreted from the perspective of continuum mechanics providing stress and strain rate fields within the rock. These serve to identify two primary deformation modes predominant in two distinct zones moving with the PDC cutter: A crush zone below the chamfer and a shear zone ahead of the cutter face. The influences of two cutter design parameters, the back rake angle and the chamfer size, on these zones and the cutting force, are investigated. The shear angle is found to decrease with increasing back rake angle, resulting in a wider shear band. Moreover, the back rake angle has a considerable influence on the cutting forces both in the normal and tangential direction, whereas the chamfer size affects the normal cutting force predominantly. These results are in good accordance with experimental observations in the literature. Furthermore, the relationship between the cutting force and underlying rock failure mechanisms is clarified.This study enhances the understanding of the rock cutting process and gives first indications for dynamic cutting force control through cutter design.

Shock response of single-crystal boron carbide along orientations with the highest and lowest elastic moduli

The response of monocrystalline boron carbide to planar shock loading has been investigated using molecular-dynamics simulations, along crystal orientations with the highest and lowest elastic moduli. While shocks of intensity lower than the Hugoniot elastic limit (HEL) generate quasilongitudinal and quasitransverse waves, an elastic precursor trailed by inelastic waves is observed when HEL is exceeded. Bond breakage, accompanied by temperature rise, is observed to be the primary mode of deformation under the inelastic waves. Higher shock intensities (particle velocity, ${U}_{p}&gt;2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s}$) generate a deformation shock front, which induces loss of shear strength along with a considerable loss of crystalline order. Boron carbide is also revealed to exhibit two distinct deformation regimes. While shear strength increases with ${U}_{p}$ in the first regime $({U}_{p}\ensuremath{\le}2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s})$, a monotonic reduction is observed in the second $({U}_{p}&gt;2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s})$. The latter regime is also characterized by a convergence in the shock Hugoniot curves obtained along the two loading directions, indicating that the Hugoniot state of boron carbide may be independent of crystal orientation for ${U}_{p}&gt;2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s}$. Finally, it is shown that the simulation-derived hydrostat curve presented in this work is coherent with experimental data up to 140 GPa and provides an accurate basis for assessing residual strength of boron carbide under shock conditions.

Assessing the magnetic order dependent γ-surface of Cr-Co-Ni alloys

In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys for reaching higher mechanical performance, it is important to establish predictive design strategies using computation-aided methods. Here, using ab initio calculations we systematically study the effects of magnetism and chemical composition on the generalized stacking fault energy surface (γ-surface) of Cr-Co-Ni medium entropy alloys and show that both chemistry and the coupled magnetic state strongly affect the γ-surface, consequently, the primary deformation modes. The relations among various stable and unstable stacking fault energies are revealed and discussed. The present findings are useful for studying the deformation behaviors of Cr-Co-Ni alloys and facilitate a density functional theory based design of transformation-induced plasticity and twinning-induced plasticity mechanisms in Cr-Co-Ni alloys.

On the microstructure evolution during low cycle fatigue deformation of wrought ATI 718Plus alloy

In the present work, strain-controlled low cycle fatigue (LCF) tests were performed at 704 °C using 0.25 Hz in cyclic frequency with tension-compression loading on the forged alloy 718Plus to investigate the fatigue performances determined by structures, and the corresponding microstructure evolutions and deformation mechanisms were analyzed through techniques of scanning electron microscope (SEM) and transmission electron microscope (TEM). The fatigue specimens from different locations (core and rim) showed similar response on cycle stress, but smaller grain size contributed to superior fatigue performance. Fatigue deformation induced the generation of η precipitates in grain interior and promoted the growth of grains and η precipitates, but brought insignificant change on the morphology of spherical γ′ phase and slightly increase in particle size and γ′/γ lattice misfit, indicating its excellent mechanical stability at 704 °C. A transition area was observed between the η precipitates and γ matrix, which was determined to be γ phase via high resolution transmission electron microscopy (HRTEM) and elements mapping techniques. Twinning and dislocation planar slip bands were confirmed to be the primary fatigue deformation modes of alloy 718Plus. Dislocations piled up and formed networks at the edges of η precipitates during the fatigue process, inducing the initiation and propagation of micro-cracks. As the cycle accumulated, the η and γ′ precipitates were sheared by gliding dislocations, resulting in weakened resistance to deformation and fatigue softening.

Hyperelastic constitutive modeling of hydrogels based on primary deformation modes and validation under 3D stress states

In isotropic linear elasticity, a constitutive model calibrated using a single deformation mode (e.g., compression or tension or shear) is sufficient to describe a complex three-dimensional (3D) stress state. Such an approach, however, is likely inadequate for modeling hydrogels, which exhibit a nonlinear stress-strain response that varies significantly between deformation modes and is also sensitive to microstructure via gel concentration. In this study, a combined experimental and constitutive modeling framework is proposed for the development and validation of concentration-dependent 3D hyperelastic models for hydrogels. Agarose hydrogel in a concentration range of 0.4–4% w/v is chosen as the model material. Uniaxial compression, uniaxial tension, and simple shear (three primary deformation modes) experiments are conducted. The small strain elastic modulus-gel concentration relationships obtained from experiments are compared with those predicted by the molecular theory of rigid polymer networks (Jones-Marques theory) to identify the concentration range in which entropic elastic (hyperelastic) response dominates. In this range (1.5–4% w/v), four hyperelastic constitutive models are fit to the combined compression-tension-shear stress-strain data: Mooney-Rivlin, three-parameter generalized Rivlin, Gent, and Gent-Gent models. It is demonstrated that the generalized Rivlin model offers the best overall accuracy, and the variation of its model parameters with gel concentration is consistent with the Jones-Marques theory. The resulting concentration-dependent Extended Generalized Rivlin model is employed in finite element simulations of the non-homogeneous 3D stress state of wedge indentation. Simulated load versus depth and strain field predictions show very good agreement with experimental wedge indentation results. Finally, it is shown that a hyperelastic model calibrated using only a single deformation mode yields poor results for other primary and 3D deformations, and thus multiple primary deformation modes (preferably all three) should be considered.