Compressive Stress Relaxation Research Articles

Dynamic Compressive Stress Relaxation Model of Tomato Fruit Based on Long Short-Term Memory Model.

Tomatoes are prone to mechanical damage due to improper gripping forces during automated harvest and postharvest processes. To reduce this damage, a dynamic viscoelastic model based on long short-term memory (LSTM) is proposed to fit the dynamic compression stress relaxation characteristics of the individual fruit. Furthermore, the classical stress relaxation models involved, the triple-element Maxwell and Caputo fractional derivative models, are compared with the LSTM model to validate its performance. Meanwhile, the LSTM and classical stress relaxation models are used to predict the stress relaxation characteristics of tomato fruit with different fruit sizes and compression positions. The results for the whole test dataset show that the LSTM model achieves a RMSE of 2.829×10-5 Mpa and a MAPE of 0.228%. It significantly outperforms the Caputo fractional derivative model by demonstrating a substantial enhancement with a 37% decrease in RMSE and a 36% reduction in MAPE. Further analysis of individual tomato fruit reveals the LSTM model's performance, with the minimum RMSE recorded at the septum position being 3.438×10-5 Mpa, 31% higher than the maximum RMSE at the locule position. Similarly, the lowest MAPE at the septum stands at 0.375%, outperforming the highest MAPE at the locule position by a significant margin of 90%. Moreover, the LSTM model consistently reports the smallest discrepancies between the predicted and observed values compared to classical stress relaxation models. This accuracy suggests that the LSTM model could effectively supplant classical stress relaxation models for predicting stress relaxation changes in individual tomato fruit.

Grain structure tailoring strategy for heterogeneous lamella SiCp/2024Al composites with exceptional strength-ductility synergy

In this work, a novel grain structure tailoring strategy using one-stepped planetary ball milling, different from conventional powder metallurgy routes that pre-prepared components with different microstructures and then mixed them up, was implemented to fabricate micro- and nano-sized SiC particles (m- & n-SiCp)/2024Al composites with heterogeneous lamella structure. The controllable transformation from homogeneous to heterogeneous grain structures is achieved via nonuniformly distributed n-SiCps induced local grain refinement. Heterogeneous lamella composites exhibit a superior modulus-strength-ductility synergy of 95.3 GPa in Young's modulus, 750.7 MPa in tensile strength and 4.9 % in uniform elongation, particularly with no less than 145 % and 175 % improvements in ductility and toughness, compared with homogeneous composites. Compressive stress relaxation experiments were conducted to reveal the structural dependence of plastic deformation behaviors. Sustainedly rising hetero-deformation induced (HDI) stress produced by extra geometrically necessary dislocation (GND) accumulation at heterogeneous soft/hard domain interfaces and sequential activation of multiple dislocation mediated mechanisms based on load transfer in heterogeneous lamella composites contribute to the enhanced strain hardening capacity, which offers intrinsic toughening. Also, extrinsic toughening originates from enhanced microcrack multiplication and crack-tip blunting.

Design of Shiitake Mushroom Robotic Picking Grasper: Considering Stipe Compressive Stress Relaxation

In order to realize the automatic picking of shiitake mushrooms and reduce the risk of damage to shiitake mushrooms in the picking process, this paper designed a shiitake mushroom picking grasper. First, this paper carries out mechanical tests of compression and stress relaxation on sections of shiitake mushroom stipes, and establishes the component stress relaxation equations of shiitake mushroom stipes. The compression mechanical characteristics of the entire mushroom stipe are then analyzed using finite element analysis, with a mean square error of less than 5% compared to actual results. Second, based on the actual picking experience, this paper proposes an “L”-shaped three-finger picking grasper, and analyzes the mechanical relationship between the grasper’s gripping force, twisting separation torque, and servo output torque. Furthermore, according to the mechanical constitutive model of mushroom stipes, the optimal twisting separation torque and corresponding servo motor output torque for the grasper are determined. The picking grasper designed in this paper was tested for picking mushrooms of different growth periods, and the test results show that the picking grasper designed in this paper is able to grasp and separate the mushrooms quickly and without damage.

Quantitative evaluation of residual stress and microstructural effects on the surface hardness of machined Ti-6Al-4 V alloy with microscopic characterization techniques

The surface hardness of machined Ti-6Al-4 V components has a significant influence on the service performance and fatigue life. It’s acknowledged that the hardness value of machined surface is dependent on microstructure and residual stress, however, the quantification of their influence levels on surface hardness is still an unresolved issue, which limits the potential for further enhancing the mechanical property of machined parts. Furthermore, it’s difficult for current studies to fully reveal the mechanism of hardness fluctuation due to release of residual stress. To address these gaps, this study presents a novel method for quantitatively evaluating residual stress and microstructural effects on the machined surface hardness using microscopic characterization techniques. The microstructures of machined Ti-6Al-4 V workpiece were characterized by electron backscatter diffraction (EBSD), and the microstructural hardening effects were analyzed. The residual stresses release and evaluation were performed by the Focused Ion Beam-Digital Image Correlation (FIB-DIC) ring core method, then the surface hardening originated from residual stress and microstructural effects can be assessed by nano-indentation measurements. The results show that the surface hardness increase induced by the combined effects of compressive residual stress and microstructure, where the microstructural hardening can be strengthening by obtaining smaller grain size and high proportion low grain boundary, and the higher magnitudes of compressive residual stress can also enhance the hardness increase. The surface softening induced by compressive residual stress relaxation with no obvious microstructural alterations was observed and the maximum softening reached 14.54% in this study. The findings are beneficial for understanding the mechanical property strengthening mechanism of the machined parts.

Polymer materials to produce wrist-hand orthoses using the additive method

Wrist-hand orthosis was developed using PolyJet Matrix (PJM) and Fused Filament Fabrication (FFF) additive technologies. MED610 and PLACTIVE were used as the filament. The orthosis was divided into parts A and B. The accuracy of both parts was checked using an optical scanner. The PJM method was more accurate. The compressive strength and stress relaxation of the orthosis were also tested. Greater strength was achieved for part A made using PJM technology, and for part B made using FFF technology.

Single crystal polarization-orientation Raman spectroscopy of zeolite LTA with confined S3− anions - High dielectric constant nanoporous material

We apply polarization-orientation Raman spectroscopy, as an alternative to X-ray diffraction, to LTA single crystals containing S3− in sodalite cages additionally to S8 rings in large cavities. The sample was obtained via sulfur vapor adsorption at ∼550 °C (LTA-S-550). We show that S3− is located in the (110) plane with its 2-fold axis along the LTA 4-fold axis. The anion position suggests strong interaction of its terminal atoms with Na+ localized in LTA 6-membered rings. The anions display optical absorption band at ∼590 nm (2.1 eV) and resonant Raman enhancement. We observe a record-high S3− bond-bending mode frequency ∼274 cm−1 due to a strong bond-angle contraction. This leads to the Fermi resonance of its overtone with the symmetric bond-stretching mode in the frequency range of 544–552 cm−1. An anomalous Raman downshift of the S3− bond-stretching modes with a decrease of temperature is observed and attributed to partial compressive stress relaxation. Luminescence band at ∼845 nm is observed suggesting considering LTA-S-550 as an interesting light-emitting material. We discuss a role of S3− in the high dielectric constant up to ∼160 and a possible contribution of the anion to the ion-exchange selectivity to Sr2+/Cs+ enhancements of LTA with sulfur.

A novel and sustainable rubber composite prepared from electric arc furnace slag as carbon black replacement

Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and its production process is no more sustainable and on the other side its price increases annually. For these reasons, sustainable alternative fillers are being studied. In the present research the main waste of the steel industry, namely the steel slag from electric arc furnace (EAF), is investigated as non-conventional filler for a nitrile butadiene rubber matrix (NBR). The slag has been characterized to ensure its safe reuse as filler according to the heavy metals leaching. The slag filled compounds have been characterized and compared to CB filled compounds, in terms of processability by rheometric parameters, mechanical properties, Payne effect, and physicochemical properties to investigate the filler-matrix interaction. From the obtained results, it was shown that EAF slag-filled NBRs are comparable to CB filled NBRs in terms of crosslink kinetics and, when compared at the same hardness level, are comparable in terms of viscosity, stiffness, and elongation at break, while when compared at the same filler volume fraction are similar in terms of compression set and stress relaxation.

Interaction between eye movements and adhesion of extraocular muscles

The contact and pull-off tests and finite element simulations were used to study the extraocular muscle-sclera adhesion and its variation with eye movement in this research. The effect of the adhesion on the eye movements was also determined using equilibrium equations of eye motion. The contact and pull-off tests were performed using quasi-static and non-quasi-static unloading velocities. Finite element models were developed to simulate these tests in cases with high unloading velocity which could not be achieved experimentally. These velocities range from the eye's fixation to saccade movement. The tests confirmed that the pull-off force is related to the unloading velocity. As the unloading velocity increases, the pull-off force increases, with an insignificant increase at the high ocular saccade velocities. The adhesion moment between the extraocular muscles and the sclera exhibited the same trend, increasing with higher eye movement velocities and higher separation angles between the two interfaces. The adhesion moment ratio to the total moment was calculated by the traditional model and the active pulley model of eye movements to assess the effect of adhesion behavior on eye movements. At the high ocular saccade velocities (about 461 deg/s), the adhesion moment was found to be 0.53% and 0.50% of the total moment based on the traditional and active pulley models, respectively. The results suggest that the adhesion behavior between the extraocular muscles and the sclera has a negligible effect on eye movements. At the same time, this adhesion behavior can be ignored in eye modeling, which simplifies the model reasonably well. Statement of Significance1. Adhesion behavior between the extraocular muscles and the sclera at different indenter unloading velocities determined by contact and pull-off tests. 2. A finite element model was developed to simulate the adhesive contact between the extraocular muscles and the sclera at different indenter unloading velocities. The bilinear cohesive zone model was used for adhesive interactions. 3. The elastic modulus and viscoelastic parameters of the extraocular muscle along the thickness direction were obtained by using compressive stress-relaxation tests. 4. The influence of the adhesion moment between the extraocular muscles and the sclera on eye movement was obtained according to the equation of oculomotor balance. The adhesion moment between the extraocular muscles and the sclera was found to increase with increased eye movement velocity and increased separation angle between the two interfaces.

Effects of applied strain, magnetic field, and temperature on the compressive stress relaxation behavior of magneto-sensitive elastomers

Effects of applied strain, magnetic field, and temperature on the compressive stress relaxation behavior of magneto-sensitive elastomers

Characterization of the Age-Related Differences in Porcine Acetabulum and Femoral Head Articular Cartilage.

The use of porcine animal models for cartilage injury has increased recently due to their similarity with humans with regard to cartilage thickness, limited intrinsic healing of chondral defects, and joint loading biomechanics. However, variations in the mechanical and biochemical properties of porcine hip articular cartilage among various tissue ages and weightbearing (WB) regions are still unknown. This study's aim was to characterize the mechanical and biochemical properties of porcine hip articular cartilage across various ages and WB regions. Articular cartilage explants were harvested from WB and non-weightbearing (NWB) surfaces of the femoral head and acetabulum of domesticated pigs (Sus scrofa domesticus) at fetal (gestational age: 80 days), juvenile (6 months), and adult (2 years) ages. Explants underwent compressive stress-relaxation mechanical testing, biochemical analysis for total collagen and glycosaminoglycan (GAG) content, and histological staining. Juvenile animals consistently had the highest mechanical properties, with 2.2- to 7.6-time increases in relaxation modulus, 1.3- to 2.3-time increases in instantaneous modulus, and 4.1- to 14.2-time increases in viscosity compared with fetal cartilage. Mechanical properties did not significantly differ between the WB and NWB regions. Collagen content was highest in the NWB regions of the juvenile acetabulum (65.3%/dry weight [DW]) and femoral head (75.4%/DW) cartilages. GAG content was highest in the WB region of the juvenile acetabulum (23.7%/DW) and the WB region of the fetal femoral head (27.5%/DW) cartilages. Histological staining for GAG and total collagen content followed the trends from the quantitative biochemical assays. This study provides a benchmark for the development and validation of preclinical porcine models for hip cartilage pathologies.

Determination accuracy enhancement of viscoelastic constitutive model of optical glass

This study proposes an effective method for improving the determination accuracy of the viscoelastic constitutive model via the combination of uniaxial creep with stress relaxation and the use of creep data to correct stress relaxation curves, known as “stress relaxation and creep correction (SRCC).” A typical molding glass was selected as the study material to fit and correct the constitutive model using the new method, and glass was regarded as a thermorheologically simple material to describe the temperature-dependent viscoelasticity. Glass cylinders were used in uniaxial compression stress relaxation experiments, which were conducted on a molding machine, and the experimental results were fitted with the generalized Maxwell constitutive model. The constitutive model was corrected further by optimization of the long-term modulus based on the SRCC method, and friction coefficients were calibrated under different molding conditions to improve the simulation accuracy. To verify the accuracy of the corrected constitutive model, we constructed a two-dimensional axisymmetric numerical model of molding biconvex aspheric lens and extracted and compared the molding displacement curves with experimental data. The results indicate that more accurate guidance for the optimization of the glass molding process can be provided based on the corrected model.

Enhancing Stiffness and Oil Resistance of Fluorosilicone Rubber Composites through Untreated Cellulose Reinforcement.

Fluorosilicone rubber, essential in automotive and aerospace owing to its excellent chemical resistance, plays a pivotal role in sealing technology, addressing the industry's evolving demands. This study explores the preparation and properties of fibrillated cellulose-reinforced fluorosilicone rubber composites to enhance their stiffness and oil resistance. Fibrillated cellulose sourced as a wet cake and subjected to processing and modification is incorporated into a fluorosilicone rubber matrix. The resulting composites are analysed by tensile and compression tests, along with compressive stress-relaxation testing in air and in an oil-immersed environment. The findings demonstrate significant improvements in the mechanical properties, including an increased Young's modulus and elongation at break, whereas the tensile strength remained uncompromised throughout the testing procedures. Morphological analysis of the fracture surfaces revealed a remarkable interfacial affinity between the fibrillated cellulose and rubber matrix, which was attributed in part to the modified fatty acids and inorganic nanoparticles. The presence of fibrillated cellulose enhanced the stress-relaxation characteristics under oil-immersion conditions. These results contribute to the domain of advanced elastomer materials, with potential for applications requiring enhanced mechanical properties and superior oil resistance.

Impedance variation of the gap sensing coil-type conductive polymer composite in the compressive loading and stress relaxation phases

The coil made of conductive polymer composite has the potential to be utilized as the flexible contactless gap and compressive stress sensor. To solve the problem of the stress measurement in the compressive loading and relaxation phases, the impedance-changes of the coil-type composite at the contactless stage and the loading and relaxation phases have been studied. The data at the contactless stage show that the amplitude/angle is attenuated/enlarged when the gap decreases. The data at the compression stage show that the impedance amplitude/angle is attenuated/enlarged when the stress increases in the loading phase and decays/grows exponentially with time in the relaxation phase. The spring-dashpot models for the compressive impedance relaxations have been established. The changing-ratio of the impedance in the loading phase is far higher than that in the relaxation phase; the changing-ratio decreases with time in the relaxation phase; and therefore there is a changing-ratio-threshold which can be used to judge whether the coil-type composite is in the loading or relaxation phase. Accordingly, a procedure to measure the gap and the stress in the loading and relaxation phases has been designed. The aforementioned results have laid preliminarily the foundations to use the coil-type composite to measure the stress and the gap.

Residual stress mapping in additively manufactured steel mould parts using asymmetric and multiple cuts contour method

The distribution of residual stress in additively manufactured (AM) complex structures can be intricate, exhibiting large gradients. Accurate measurements with high spatial resolution at significant depths are crucial for understanding the residual stress distribution in AM parts. In this study, the contour method, with asymmetric and multiple cuts, is employed to map residual stresses on various cross-sections of AM steel mould parts with inner channels. The resulting residual stress maps are compared for different states: as-built, shot-peened, and shot-peened plus heat-treated, in order to quantify the stress relaxation effect of each processing step. In the as-built state, elevated levels of tensile stress are observed around the perimeter, with a substantial stress gradient throughout the depth. Compressive stresses are distributed over a larger interior region, but with lower magnitudes compared to the tensile stresses. Upon shot-peening, the tensile stresses are reduced by approximately 300 MPa around the perimeter, with limited relaxation up to a depth of 1 mm compared to the as-built state. In the shot-peened and heat-treated state, a more significant stress relaxation is observed across the cross-sections. The maximum relaxation in tensile stress reaches approximately 1200 MPa, while the maximum compressive stress relaxation amounts to around 500 MPa, both compared to the as-built state. The stress maps effectively identify regions experiencing significant stress states, and the two-dimensional comparisons between different stress states provide crucial information for enhancing and validating AM models and processing techniques.

Improving the high cycle fatigue property of Ti6Al4V ELI alloy by optimizing the surface integrity through electric pulse combined with ultrasonic surface rolling process

To improve the surface integrity and high cycle fatigue property of Ti6Al4V ELI alloy, the electric pulse has been introduced into the ultrasonic surface rolling process (USRP), which is called electric pulse-assisted ultrasonic surface rolling process (EUSRP). With the help of “electroplasticity” of the electric pulse, the thickness of the surface gradient deformation layer was about three times of the USRP specimens by adjusting the pulse current level. However, the surface hardness decreases due to the continuous effect of the pulse current and the “skin effect” during treatment. It is worth noting that the higher the applied pulse current, the more severe the softening. This paradox causes the fatigue performance of EUSRP specimens lower than that of USRP specimens. To break this paradox, the EUSRP treatment is followed by a USRP treatment. The EUSRP-2 (with a pulse current of 200 A) +USRP specimens exhibit excellent surface hardness, a gradient deformation layer thickness of about 400 µm, low surface roughness and high compressive residual compressive stress. Besides, the hardening mechanisms of the different surface strengthening specimens have been quantitatively analyzed in combination with microstructure analysis. The fatigue life of Ti6Al4V ELI alloy can be improved by about 25 times at 780 MPa using the EUSRP-2+USRP treatment, the main reason for the highest fatigue life is the deepest surface gradient layer and the deepest crack initiation site. The fatigue limit of the EUSRP-2+USRP specimens is not the highest because too much surface hardening causes compressive residual stress relaxation during cycling and the beneficial effect of compressive residual stress is eliminated.

Fatigue crack initiation and growth behavior within varying notch geometries in the low‐cycle fatigue regime for FV566 turbine blade material

AbstractPlain bend bars made from FV566 martensitic stainless steel were extracted from the root of ex‐service power plant turbine blades and several industry‐relevant notch geometries were introduced. Some of the samples were shot peened. The notched bend bars were loaded plastically in the low‐cycle fatigue regime and finite element (FE) modeling carried out to investigate the effects of changing notch geometry, combined with shot peening, on fatigue behaviors such as crack initiation, short crack growth, and coalescence. Shot peening damaged the notch surface, accelerating initiation behaviors, but had a lifetime‐extending effect by retarding short crack growth in all tested notch geometries. At a total strain range higher than 1.2%, the lifetime extension benefit from shot peening was diminished due to compressive residual stress relaxation in the notch stress field. Notch geometry (and the associated varying constraint levels and stress/strain gradients) was found to have no notable difference on fatigue life when tested at identical notch‐root strain ranges.

Terrace Engineering of the Buffer Layer: Laying the Foundation of Thick GaN Drift Layer on Si Substrates

AbstractVertical GaN‐on‐Si devices are promising for the next‐generation high‐voltage power electronics with low cost and high efficiency. However, their applications are impeded by the limited thickness of crack‐free GaN layers and high threading dislocation density (TDD) in the layer. Buffer layers are crucial for stress control while they usually behave with poor surface morphology, which causes early stress relaxation in GaN and limited thickness. Hereby, a terrace engineering approach for the buffer layers is proposed. Through tuning the supersaturation ratio, the terrace width can be manipulated and an atomically smooth AlGaN buffer layer can be realized, which effectively reduces the compressive stress relaxation and provides a firm foundation for thick GaN growth. As a result, a 7.5 µm thick GaN drift layer with TDD as low as 8.6 × 107 cm−2 is achieved on Si substrates. The room temperature electron mobility of the GaN drift layer can be raised up to 1210 cm2 V−1 s−1. The fabricated PiN diode shows a high breakdown voltage of 1058 V as well as a high on/off ratio of 1012. This work thus truly demonstrates the potential of high‐performance and low‐cost GaN‐based electronic as well as optoelectronic devices on Si platforms.

Vascular Cambium—Between the Hammer and the Anvil: A Tensile Stress Hypothesis on the Mechanism of Radial Growth of Broadleaved Trees

The vascular cambium is the main lateral meristem responsible for the secondary growth of trees. There are a number of explicit and implicit assumptions behind this statement which allow questions to be raised about the mechanism underlying the radial growth of trees. Based on the hypothesis of the diurnal strains of plant organs, it is anticipated that the process of radial growth can be understood as an adaptation to the cyclically changing mechanical stress in the radial direction generated by the phloem during the 24 h day cycle. This qualitative hypothesis treats cambium as a tissue subjected to nighttime stretching and daytime compression in the radial direction. The proposed osmo-mechanical hypothesis of the radial growth of vascular cambium links the daily change in water status and the considerable daily strains in the xylem and phloem with the radial net expansion of a tree trunk. We highlight transpiration as a major factor influencing the secondary growth of woody plants. Thus, we indirectly relate all the biotic (e.g., insect infestation, fungi infections, injuries, shadowing, intra- and interspecies competition, parasitism, symbiosis, etc.) and abiotic (e.g., humidity, water availability, wind, injuries, shadowing, day length in a vegetative season, altitude, temperature, insolation, etc.) processes influencing transpiration with radial growth. In the proposed hypothesis, we also infer that differences in the strains in phloem and xylem are the direct source of tensile stress, tensile stress relaxation, compressive stress, and compressive stress relaxation in the vascular cambium. This sequence appears to be crucial in understanding both the process of the radial growth of trees and the formation of differential wood patterns, within the same genotype as well as in different genotypes. It also provides arguments for the discussion on the mechanisms regulating processes in the vascular cambium. It points out the important role of the variable mechanical stresses in the radial, circumferential, and axial directions and their interference in the development of this lateral meristem. Thus, this hypothesis supports the concept of the epigenetic and systemic regulation of intrinsic wood patterns and tree forms by environmental factors. The hypothesis is focused exclusively on broadleaved trees and symplastic growth. This limitation of the scope is due to a concern for clarity. In this form, the hypothesis provides an alternative explanation for a pure process of radial growth and paves the way for a better interpretation of such phenomena as earlywood and latewood formation. At the same time, this approach to the vascular cambium provides answers to many questions related to the generation of the mechanical conditions necessary for the occurrence of intrusive growth between tangential cell walls; this is of fundamental importance for fusiform initials readjustment, vessel element and fibre formation, ring-porous wood formation, etc.

Competitive effect of residual stress and surface roughness on the fatigue life of shot peened S42200 steel at room and elevated temperature

The effect of shot peening (SP) on the fatigue life of S42200 steel at room and elevated temperature is investigated. The fatigue test is carried out on a high temperature rotating bending tester. Surface integrity characterization is used to study the effect of SP on surface properties. Furthermore, Finite Element Method (FEM) combined with a fatigue damage model, namely Zheng Equation, is proposed to predict the fatigue life. The results show that SP effectively improves the fatigue life of S42200 steel under all temperatures. However, at lower temperature, higher strength SP leads to higher fatigue resistance, while at higher temperature, lower strength SP leads to higher fatigue resistance. This can be explained by the competitive effect of surface roughness and compressive residual stress (CRS) relaxation on the local stress concentration. This research can be a good guide to the application of SP at different temperatures.

Compressive mechanical properties of vitrified porcine menisci are superior to frozen and similar to fresh porcine menisci.

The common practice of freezing meniscal allograft tissue is limited due to the formation of damaging ice crystals. Vitrification, which eliminates the formation of damaging ice crystals, may allow the mechanical properties of meniscal allograft tissue to be maintained during storage and long-term preservation. The primary objective of this study was to investigate the differences between fresh, frozen, and vitrified porcine lateral menisci examining compressive mechanical properties in the axial direction. Unconfined compressive stress-relaxation testing was conducted to quantify the mechanical properties of fresh, frozen and vitrified porcine lateral menisci. The compressive mechanical properties investigated were peak and equilibrium stress, secant, instantaneous and equilibrium modulus, percent stress-relaxation, and relaxation time constants from three-term Prony series. Frozen menisci exhibited inferior compressive mechanical properties in comparison with fresh menisci (significant differences in peak and equilibrium stress, and secant, instantaneous and equilibrium modulus) and vitrified menisci (significant differences in peak stress, and secant and instantaneous modulus). Interestingly, fresh and vitrified menisci exhibited comparable compressive mechanical properties (stress, modulus and relaxation parameters). These findings are significant because (1) vitrification was successful in maintaining mechanical properties at values similar to fresh menisci, (2) compressive mechanical properties of fresh menisci were characterized providing a baseline for future research, and (3) freezing affected mechanical properties confirming that freezing should be used with caution in future investigations of meniscal mechanical properties. Vitrification was superior to freezing for preserving compressive mechanical properties of menisci which is an important advance for vitrification as a preservation option for meniscal allograft transplantation.