Tension-compression Asymmetry Research Articles

Microplane Constitutive Model for Tension–Compression Asymmetry and Pressure-Sensitive Damage in Polymers

Abstract The multiaxial damage behavior of brittle polymers is highly complex, involving a stark tension–compression asymmetry and strong pressure sensitivity. These aspects are challenging to predict via phenomenological tensor-based damage models. Recognizing that these behaviors stem from various microscale damage mechanisms, this work presents a novel adaptation of the microplane constitutive model for these materials. The salient feature of the model is the semi-multiscale architecture consisting of “microplanes,” which are imagined planes of various orientations within the material microstructure. Various tensile and compressive damage mechanisms are formulated in terms of stress–strain vectors acting on these microplanes. The homogenized macroscale stress tensor is obtained via the principle of the virtual work. This multiscale arrangement allows simple, intuitive, and physically based formulations of microscale damage mechanisms as well as easy distinction of tension and compression. The mechanisms considered here include tensile microcracking, shear-driven plastic-frictional damage, and far postpeak compression hardening. The formulation involves splitting the volumetric and deviatoric components of stresses, which enables properly capturing Poisson ratios greater than 0.25. It also includes a normal strain dependence of the microplane strain limits governing frictional damage evolution. The model is calibrated and successfully validated against experimental data on several polymers under uniaxial tension, compression, and triaxial compression. The model is demonstrated to capture the tension–compression asymmetry of the inelastic behavior, as well as the pressure-sensitive nonlinear behavior under triaxial compression, in excellent agreement with experiments. Notably, the predictions under triaxial compression are found to outperform the Drucker Prager model, thus highlighting the superior potential of the microplane modeling approach for multiaxial damage in polymers.

Elastic–plastic bending analysis of beams with tension–compression asymmetry: bimodular effect and strength differential effect

Elastic–plastic bending analysis of beams with tension–compression asymmetry: bimodular effect and strength differential effect

The Derivation of CRSS in pure Ti and Ti-Al Alloys

The work focuses on the determination of the critical resolved shear stress (CRSS) in titanium (Ti) and titanium-aluminum (Ti-Al) alloys, influenced by an array of factors such as non-symmetric fault energies and minimum energy paths, dislocation core-widths, short-range order (SRO) effects which alter the local atomic environment, and tension-compression (T-C) asymmetry affected by intermittent slip motion. To address these multifaceted complexities, an advanced theory has been developed, offering an in-depth understanding of the mechanisms underlying slip behavior. The active slip systems in these materials are basal, prismatic, and pyramidal planes, with the latter involving both 〈a〉 and 〈c+a〉 dislocations. Each slip system is characterized by distinct Wigner-Seitz cell configurations for misfit energy calculations, varying partial dislocation separation distances, and unique dislocation trajectories—all critical to precise CRSS calculations. The theoretical CRSS results were validated against a comprehensive range of experimental data, demonstrating a strong agreement and underscoring the model's efficacy.

Statistical investigation on the tension-compression asymmetry of slip behavior and plastic heterogeneity in an aged Mg-10Y sheet

Statistical investigation on the tension-compression asymmetry of slip behavior and plastic heterogeneity in an aged Mg-10Y sheet

Viscoelastic–viscoplastic model with ductile damage accounting for tension–compression asymmetry and hydrostatic pressure effect for polyamide 66

This paper proposes a model for predicting the complex inelastic mechanical response of polyamide 66. Polyamide 66 is a semi-crystalline pressure-sensitive polymer that exhibits asymmetric yielding behavior, in which the yield strength is slightly higher in compression. With this in mind, an I1-J2 yield function considering the asymmetric behavior and the hydrostatic pressure effect is presented and integrated into a phenomenological viscoelastic–viscoplastic model accounting for ductile damage. The corresponding thermodynamic framework and constitutive laws are discussed. Then, an experimental approach is presented to identify the model parameters through mechanical tests with different loading paths to capture the active mechanisms. The experimental findings obtained from uni-axial and multi-axial (tension-torsion) mechanical tests and the numerical model are used in an optimization algorithm to identify the model parameters. A parametric analysis is performed to study the effect of the asymmetric behavior on the state variables under different loading conditions using the identified parameters. The present model responses are in good agreement with the experimental data, and the combination of the experimental and numerical results demonstrates and states the asymmetric behavior of polyamide at relative humidity (RH) of 50%, which is captured by the suggested model. It is also worth pointing out that the parametric study conducted on a notched plate using finite element simulations showcases the structural computation capabilities of the proposed model.

Effects of compressive stress on the corrosion behavior of biodegradable zinc with tension-compression asymmetry under simulated physiological environment

Biodegradable Zn vascular stents are compressed by the vessel wall while maintaining blood flow, which may lead to unpredictable deterioration of the stent due to stress corrosion. This work investigated the mechanical and corrosion behavior of Zn in a coupled environment of compressive stress and artificial plasma. The corrosion rate of Zn increases as compressive stress rises. However, the acceleration effect gradually decreased in contrast to our previous work on tensile stresses, which can be attributed to the tension-compression asymmetry of Zn-metal. Meanwhile, the corrosion mechanism of Zn was compared, and numerical models for stresses and corrosion rates were established.

Tension-compression asymmetry and the grain-scale slip behavior in untextured Mg-10Gd-3Y-0.5Zr (wt.%)

Mg-10Gd-3Y-0.5Zr (wt.%) is a recently developed high-performance cast Mg alloy with random texture. The present work found that both strength and ductility of this alloy were significantly larger for compression than that for tension, i.e. the mechanical properties exhibited tension-compression asymmetry (TCA), although no twins were observed. To understand this uncommon behavior, the relative activity of individual slip modes and slip-slip interactions during deformation were analyzed in detail at grain scale, based on quasi-in-situ experiments, combined with slip trace analysis and EBSD technique. Significantly asymmetric slip behavior was observed. Although basal slip always dominated for both tension and compression, the relative activity of pyramidal II <c+a> (PyrIICA) slip for tension was 2.6 times higher than that for compression. Statistical analysis of the angle between the active slip plane normal and the loading direction implied that the PyrIICA slip was more easily activated when the slip plane under tension. The asymmetric activity of PyrIICA slip was believed to contribute to the observed yield strength TCA. What’s more, almost all possible combinations of cross slip and slip transfer for total 30 slip systems were observed and analyzed in detail only during compression, while such behavior was not observed under tension. The strong slip-slip interactions induced by massive cross slips and effectively accommodated intergranular deformation by slip transfer were consistent with the well-balanced strain hardening, which resulted in improved ultimate strength and ductility for compression.

Strain rate-dependent tension-compression asymmetry in cast Mg-Gd-Y alloy: Insights into slip and twinning mechanisms

Tension-compression asymmetry is a critical concern for magnesium (Mg) alloys, particularly in automotive crash structures. This study systematically examines the tension-compression asymmetry of a cast Mg-Gd-Y alloy at various strain rates. Experimental results indicate symmetric yielding stress under both tension and compression at all strain rates, along with a reduction in the tension-compression asymmetry of ultimate stress and plastic strain as the strain rate increases. This trend arises from an unusual strain rate-dependent tension-compression asymmetry, characterized by strain rate toughening in tension and negligible strain rate effect in compression. The differing behavior is linked to the distinct twinning mechanisms under tension and compression. The suppression of twinning under tension contributes to the positive strain rate dependence of pyramidal slip, whereas the activation of abundant twins during compression means that pyramidal slip is unnecessary to accommodate c-axis strain, leading to the absence of a strain rate effect in compression. Abundant twins nucleate consistently from yielding to 2% strain, but only after basal and prismatic <a> slip have mediated microplasticity, suggesting that these slip systems reduce the nucleation stress for twinning during compression, resulting in a lower activation stress for twinning compared to tension. This study provides new insights into micromechanisms of the tension-compression asymmetry in cast Mg-Gd-Y alloys and offers practical guidance for the application of these materials in critical components that must endure both tension and compression under varying strain rates.

The deformation behavior and mechanism modeling of a corrosion-resistant Ni-Cr-Mo alloy with nanoscale precipitates at room and elevated temperatures

Ni-Cr-Mo alloys are widely-used materials in various critical applications owing to their excellent balance of strength and ductility. The precipitates play a significant role in the exceptional mechanical properties of these alloys, yet the precise microscopic mechanisms underpinning the enhanced properties are still open. Here, the atomistic simulation based on molecular dynamics (MD) was employed to investigate the deformation behavior and mechanism of the precipitation-strengthened single crystal Ni-Cr-Mo alloy under uniaxial loading at temperatures of 300 K, 500 K, 700 K, and 900 K. The results revealed high temperature-induced softening under both tension and compression. Furthermore, the tension-compression asymmetry in ultimate strength is influenced by the disparity in Schmid factor of leading Shockley partial dislocations. By monitoring the evolution of microscopic defects during deformation, the Shockley partial dislocation slip was identified as the primary deformation mechanism in the plastic regime at 300 K, 500 K, 700 K, and 900 K. Based on that, a flow stress representation model was proposed. Moreover, the investigation on the nanoscale Ni2(Cr, Mo) precipitates revealed the transition from the Orowan bypass mechanism to the shearing mechanism under uniaxial loading, accompanied by the formation of dislocation tangles. The dislocation tangles impeded dislocation slip, enhancing the mechanical properties of the alloy. The precipitate can significantly promote the formation of the lamellar dislocation structure under compression at 900 K.

Size effect and its atomistic origin on the mechanical properties of open-cell nanoporous amorphous alloy

Nanoporous amorphous alloys exhibit outstanding mechanical properties, including enhanced ductility, high strength-to-density ratio, and exceptional toughness. In this paper, atomistic models of nanoporous CuZr amorphous alloys (NP–CuZr AAs) with self-similar microstructures but varying ligament sizes are constructed. Molecular dynamics simulations are employed to examine the effects of ligament size on their mechanical properties. The yield strength, yield strain, and Young's modulus are found to be higher under tension than under compression. This tension-compression asymmetry stems from the surface effect, and it becomes more pronounced with decreasing ligament size. As the ligament size increases, the Young's modulus and compressive yield strength increase, while the tensile yield strength and ultimate tensile strength decrease. The tensile behavior comprises linear elastic deformation, strain-hardening, and ligament decay stages. During the ligament decay deformation stage, ligament necking and fracture are more severe with larger ligament sizes, resulting in relatively lower resistance stress.

On the role of the retained porosity on the shock response of additively manufactured high-performance steel: Experiments, constitutive model and finite-element predictions

Experiments have shown that for quasi-static and moderate strain-rates (of the order of 102–103/s) the mechanical response of additively manufactured (AM) and traditionally processed high-strength steels is similar whereas the impact behavior is markedly different. In this paper, we reveal that the main reason for this difference is the retained porosity in the AM material. Fully-implicit finite element calculations are presented in which we simulate both the launching of the impact plate and the impact between the two plates. The constitutive model used is the elastic/plastic model for porous ductile materials with matrix displaying tension-compression asymmetry and Johnson-Cook hardening law that accounts for both strain-rate effects and plastic history. It is shown that even a very small initial porosity changes the wave front, decreases the Hugoniot while increasing the shock rise time, when compared to a void free material. Furthermore, quantitative comparisons between simulation results and plate impact data for both the AM and the wrought AF9628 steel are provided. The good agreement show that the model captures the impact response and illustrates the model capabilities to provide information on field variables that cannot be directly measured.Additive manufacturing (AM) of metals is rapidly advancing as a robust method for production of geometrically complex parts. To enhance understanding of material performance and open up additional application opportunities, dynamic characterization of newly printed alloys is required to validate their effectiveness. In this paper, we present results from plate impact testing of AF9628 steel, a newly developed high-strength low alloy martensitic steel for structural applications which require resistance to high-rate deformation. We put into evidence differences in the shock structure between the AM and the traditionally processed material. To gain understanding, we conduct fully-implicit finite element (FE) calculations in which we model both the launching of the impact plate and the impact between the two plates, respectively. An elastic/plastic damage model that accounts for the effects of the tension-compression asymmetry in plastic deformation and its influence on porosity evolution is used. The FE results reveal that even a very small amount of initial porosity leads to an increase in the shock rise time, explaining the observed trends. Furthermore, quantitative comparisons between simulation results and plate impact data for both the AM and the wrought AF9628 are provided. The good agreement show that the model captures the impact response and illustrates the model capabilities to provide information on field variables that cannot be directly measured.

Phase-field approach for precise fracture tracking in anisotropic rocks: Integrating orthotropy-based energy decomposition and two-fold symmetric fracture toughness

Rock formations are known to exhibit material anisotropy, both in terms of elastic and fracture properties. This means that the fracture path in such formations is not a priori known but rather a complex unknown that requires robust numerical techniques to predict accurately. In this context, the phase-field model is considered particularly effective, provided that certain physical considerations are carefully adjusted to align with the physics of the problem. While addressing elastic anisotropy is well-established, the tension–compression asymmetry necessary to inhibit crack interpenetration in phase-field fracture models needs to account for the specific material anisotropy. Additionally, to accurately capture crack propagation, it is critical to simultaneously account for orientation-dependent fracture toughness in such materials. To address this, the present study employs an anisotropic phase-field model that integrates the generalized spectral decomposition proposed in the literature for orthotropic materials with a two-fold symmetric fracture toughness, to predict the fracture trajectories in rock-type samples under fixed mixed-mode loading ratios. While each of the two aspects has primarily been applied to model orthotropic plates under simple tensile and shearing loading conditions in the literature, here we study their applicability in complex loading scenarios. To this end, the experimental data from notched semi-circular specimens of Grimsel Granite undergoing complex mixed-mode loading obtained in our previous work is considered. We focus on two given mode-mixity ratios and perform numerical studies. Our results emphasize the importance of considering this generalized decomposition for phase-field modeling of fracturing in rock-type materials, particularly under loading conditions where the crack might otherwise be unrealistically driven into the compressive region. Although certain features are well captured by considering anisotropy in elasticity alone, our findings demonstrate that incorporating a two-fold symmetric fracture toughness proves to be advantageous for more precise tracking of the fracture path.

Constitutive modeling of functional fatigue with tension–compression asymmetry for superelastic NiTi shape memory alloy

Under cyclic loads, superelastic shape memory alloys (SMAs) exhibit stress–strain responses featured by functional fatigue, i.e., degradation of superelasticity and accumulation of irrecoverable deformation as cycling number increases, together with an asymmetry between tensile and compressive responses. Comprehensive understanding and modeling of these material complexities are crucial for the design and analysis of various superelastic SMA structures in practical applications. This work has developed a novel constitutive model based on irreversible thermodynamics to account for functional fatigue with tension–compression asymmetry. A potential function, defined as a weighted sum of two potentials that are calibrated against the tensile and compressive responses respectively, is employed to generate the asymmetric responses, and functional fatigue is represented by degradation of superelastic properties and growth of plastic strain as martensitic transformation accumulates. The model is adopted in numerical simulations for superelastic SMA tubes under cyclic lateral compression, which is experimentally investigated as a model problem. The agreement between simulations and experiments shows the validity and effectiveness of this constitutive modeling. Through additional finite element simulations incorporating this model, the effects of tension–compression asymmetry under cycling and diameter-to-thickness ratio of the tubular geometry upon mechanical responses of laterally compressed SMA tubes are also unveiled.

Automated data-driven discovery of material models based on symbolic regression: A case study on the human brain cortex

We introduce a data-driven framework to automatically identify interpretable and physically meaningful hyperelastic constitutive models from sparse data. Leveraging symbolic regression, our approach generates elegant hyperelastic models that achieve accurate data fitting with parsimonious mathematic formulas, while strictly adhering to hyperelasticity constraints such as polyconvexity/ellipticity. Our investigation spans three distinct hyperelastic models—invariant-based, principal stretch-based, and normal strain-based—and highlights the versatility of symbolic regression. We validate our new approach using synthetic data from five classic hyperelastic models and experimental data from the human brain cortex to demonstrate algorithmic efficacy. Our results suggest that our symbolic regression algorithms robustly discover accurate models with succinct mathematic expressions in invariant-based, stretch-based, and strain-based scenarios. Strikingly, the strain-based model exhibits superior accuracy, while both stretch-based and strain-based models effectively capture the nonlinearity and tension-compression asymmetry inherent to the human brain tissue. Polyconvexity/ellipticity assessment affirm the rigorous adherence to convexity requirements both within and beyond the training regime. However, the stretch-based models raise concerns regarding potential convexity loss under large deformations. The evaluation of predictive capabilities demonstrates remarkable interpolation capabilities for all three models and acceptable extrapolation performance for stretch-based and strain-based models. Finally, robustness tests on noise-embedded data underscore the reliability of our symbolic regression algorithms. Our study confirms the applicability and accuracy of symbolic regression in the automated discovery of isotropic hyperelastic models for the human brain and gives rise to a wide variety of applications in other soft matter systems. Statement of significanceOur research introduces a pioneering data-driven framework that revolutionizes the automated identification of hyperelastic constitutive models, particularly in the context of soft matter systems such as the human brain. By harnessing the power of symbolic regression, we have unlocked the ability to distill intricate physical phenomena into elegant and interpretable mathematical expressions. Our approach not only ensures accurate fitting to sparse data but also upholds crucial hyperelasticity constraints, including polyconvexity, essential for maintaining physical relevance.

A finite strain viscoelastic model with damage and tension–compression asymmetry considerations for solid propellants

A short survey on the experimental testing of solid propellants has highlighted finite strain responses that are temperature-dependent, viscoelastic with damage, and exhibit tension/compression asymmetry. Consequently, a finite strain viscoelastic model that satisfies the principles of thermodynamics has been developed. This model is based on the common multiplicative decomposition of the deformation gradient into elastic and viscous components, with considerations for damage and asymmetry. The model has been tested against three sets of data from the literature, carefully selected to represent the various characteristics of solid propellants. The model accurately reproduces uniaxial tension responses at different strain rates and temperatures, with the capability to account for superimposed hydrostatic pressure. Notably, these satisfactory representations require only five fitting parameters, in addition to the typical identification of polymer linear viscoelasticity and time–temperature superposition. Finally, an attempt to reproduce both tension and compression tests conducted independently on the same material underscores the need to account for tension–compression asymmetry, as defined in the proposed constitutive equations. This finding advocates for new tests, such as compression following tension and vice versa.

A coupled crystal inelasticity-phase field model for crack growth in polycrystalline nitinol microstructures

Abstract This paper introduces a comprehensive computational framework, comprising a finite deformation crystal inelasticity constitutive model and phase field model, for modeling crack growth in superelastic nitinol polycrystalline microstructures. The crystal inelasticity model represents crystal stretching and lattice rotation from elastic mechanisms, as well as local inelastic deformation due to austenite-martensite phase transformation. The phase field formulation decomposes the Helmholtz free energy density into stored elastic energy, phase transformation energy, and crack surface energy components. The elastic energy accounts for tension-compression asymmetry with the formation of the crack through a spectral decomposition. Kinetic Monte Carlo simulations generate equilibrium area fractions of different surface orientations, which serve as weights for the surface energy. An adaptive wavelet-enhanced hierarchical finite element (FE) model is introduced to alleviate high computational overhead in phase field crack simulations. Simulations with the coupled inelasticity phase field model are conducted under various loading conditions including Mode-I tension, a quasi-static Kalthoff experiment, and cyclic loading of polycrystalline microstructures. Crack propagation is effectively predicted by this model, providing valuable insights into the material mechanical behavior with growing cracks.

Understanding the mechanism of bimodal texture evolution and DRX behavior of AZ31 magnesium alloy during shear deformation

Shear deformation in commercial magnesium alloys frequently resulted in an additional atypical texture where the basal plane aligned nearly parallel to the extrusion direction, affecting the alloy's mechanical anisotropy. This study prepared AZ31 magnesium alloys with both typical shear texture and atypical texture using a two-stage shear method at 250 °C, 290 °C, and 340 °C. The formation mechanism of the bimodal texture and their relationship with dynamic grain refinement and deformation parameters were comprehensively investigated. While temperature-dependent activation of <c+a> slip usually contributed to the atypical texture, this study identified a {101¯2} twin associated microstructure that reinforced the abnormal texture at lower processing temperature. It was found that the abundant nucleation of the multi-orientation {101¯2} twin bands in the initial stage and their differential slip activations facilitated the evolution of an alternating banded structures characterized by bimodal texture. These microstructures inherited the grain boundary rotation axis of {101¯2} twin and was potentially assimilated into specialized θ[112¯0] symmetric tilt grain boundaries with lower interface energy during continuous shear, stabilizing the bimodal texture. During shear deformation, grain nucleation strengthened the [101¯0]−[112¯0] fibers with bimodal texture by generating ∼30°[0001] grain boundaries through the preferential accumulation of prismatic dislocations. However, more continuous dynamic recrystallization, discontinuous dynamic recrystallization, and micro-shear bands facilitated the nucleation of grains with dispersed basal orientations via dominant non-prismatic dislocations, weakening the overall texture. Besides, the mechanical anisotropy of the alloys was comprehensively influenced by atypical texture and microstructure. At higher deformation temperatures, the reduction in twinning bands and the increase in dynamic recrystallization level relieved the alloy’s tension-compression asymmetry, but deprived its yield strength. This study supplemented the formation mechanisms of bimodal texture during shear deformation, providing valuable insights for optimizing wrought magnesium alloys with superior mechanical properties.

Effect of unusual texture on tension-compression asymmetry for Mg-RE alloy by viscoplastic self-consistent modeling

The tension-compression asymmetry presents notable challenges for the application of magnesium alloys in many fields. In this study, the solid-solution treated Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy's tension-compression asymmetry was examined using optical microscope (OM), x-ray diffraction (XRD), viscoplastic self-consistent (VPSC) modeling, and electron backscatter diffraction (EBSD). The VPSC hardening parameters were significantly adjusted based on the Schmid factor of deformation modes in rare earth magnesium (Mg-RE) alloy, which came from the EBSD data. Excellent agreement was found between the modified VPSC model's calculation results, especially the stress-strain curves and pole figures. The alloy exhibited good strength with a negligible tension-compression asymmetry and an impressive 0.98 ratio of compressive yield strength to tensile yield strength (CYS/TYS). The main cause could be attributed to the unusual texture of (11-20) <0001> in alloy, which eliminated the imbalance in tension and compression deformation by having a negative effect on the activation of {10-12} twinning in tensile and a positive effect in compressive deformation. The activation level of {10-12} twinning was 0.37 and 0.40 calculated by VPSC model, in the plastic deformation of tension and compression, respectively; in the tensile and compression samples, the EBSD data indicated that approximately 31.9% and 31.1% (area proportion) of the grains were deformed with twins, respectively. Both tension and compression deformation showed the {10-12} twinning in the early stage of deformation, which transformed to {11-22} twinning in the later stage. The considerable activation of pyramidal <c+a> during the later stages of deformation endowed the alloy with good ductility.

Dual-phase polycrystalline crystal plasticity model revealing the relationship between microstructural characteristics and mechanical properties in additively manufactured maraging steel

To elucidate the relationship between microstructural characteristics and mechanical properties in additively manufactured (AM) maraging steel, this study introduces a computational approach that addresses two fundamental challenges. Firstly, it addresses the creation of representative volume elements (RVEs) that mimic the observed microstructural complexities, such as meltpool boundaries, prior austenite grains, packets and blocks of lath martensite. This is accomplished through the application of Potts Monte-Carlo methods and grain segmentation techniques in accordance with the Kurdjumov–Sachs orientation relationship. Secondly, this study develops a comprehensive crystal plasticity (CP) model encompassing both bcc and fcc plasticity. Inspired by atomistic and discrete dislocation dynamics studies, the proposed CP model incorporates characteristics intrinsic to bcc plasticity, including non-Schmid effects, dislocation and precipitate strengthening, and Hall–Petch type strengthening of elongated martensitic blocks. Utilizing the created RVEs and the proposed CP framework, finite element simulations are conducted based on an update-Lagrangian formulation. The purpose of this study is to investigate the deformation behavior, texture evolution, tension–compression asymmetry, and evolution in dislocation density in RVEs representative of as-built and heat-treated samples of maraging steel. This computational approach and its findings deepen our understanding of the intricate interplay between microstructural characteristics and mechanical properties in maraging steel and also provide valuable guidelines for refining its additive manufacturing and heat treatment processes.

Triaxial mechanical characterization of ultrasoft 3D support bath-based bioprinted tubular GelMA constructs

Support bath-based extrusion bioprinting is an emerging additive manufacturing paradigm that allows for the creation of geometrically complex three-dimensional tissue-mimicking constructs. Although this approach enables arbitrary geometries to be printed, preserving shape and mechanical integrity after the construct is extracted from the support bath is one of the main challenges today. In the present study, we systematically tested the effect of critical printing parameters on construct integrity and stiffness. Specifically, we varied the concentration and temperature of the bioink and support bath material, hydrogel crosslinking time, and cell density of the bioink. While previous studies on hydrogel materials quantify construct properties based on a single loading mode-such as uniaxial testing or rheological experiments, for example—we used a multiaxial mechanical testing protocol to assess the printed construct’s response in tension, compression, and shear. For each sample, we determined a single set of material parameters by simultaneously fitting all three modes in our inverse finite element framework. In support of future modeling work, we analyzed three different constitutive models with respect to their ability to match the construct’s mechanical response. We observed that GelMA concentration, temperature, and cell density have a statistically significant effect on the construct stiffness; support bath temperature and UV crosslinking time have a weak effect on construct stiffness; and support bath concentration appears to have no direct effect on the measured construct properties. Our construct stiffness were found to vary between 0.07 and 2.2 kPa depending on printing conditions, and showed noticeable tension–compression asymmetry as well as pronounced nonlinear behavior when loaded under shear.