Instantaneous Modulus Research Articles

Deformation Model of Chains and Networks with Extendable Bonds

The nonlinear stress–strain response of synthetic and biological networks and gels manifested in a monotonic increase of an instantaneous modulus is a result of the nonlinear deformation of individual network strands. To describe this behavior, we develop a nonlinear network deformation model, which relates macroscopic stress–strain response with force-elongation behavior of polymer chains with bending rigidity and extendable bonds. In particular, network mechanical properties such as structural shear modulus, extensibility ratio, and bond deformation modulus are expressed in terms of chain bending constant, Kuhn length, bond elastic constant, and chain sizes in undeformed and fully extended states. The chain deformation model is tested by molecular dynamics simulations of deformation of coarse-grained chains with harmonic and finitely extensible nonlinear elastic (FENE) bonds and is applied to analyze the DNA deformation data. The network model predictions are confirmed by molecular dynamics simulations of diamond networks made of coarse-grained chains and are used to describe experimental data for biological networks of collagen, fibrin, and neurofilaments.

Comprehensive investigation of the viscoelastic properties of PMMA by nanoindentation

Instrumented nanoindentation (NI) was used to examine the viscoelastic properties of poly(methyl methacrylate) (PMMA) as an amorphous polymer model. An evaluation combining adhesive contact and empiric spring–dashpot models has been applied to obtain the instantaneous elastic modulus E0 and the infinitely elastic modulus E∞ from nanoindentation creep curves. The value of E0 has been compared to moduli obtained with atomic force microscopy-based nanoindentation (AFM-NI) and compression tests. Furthermore, the elastic modulus has been evaluated by the method introduced by Oliver and Pharr (O&P) for the NI and AFM-NI results. Comparison of the elastic modulus E0 from the creep measurements of NI and AFM-NI to compression tests reveals good agreement of the results. However, only the O&P based AFM-NI results yield to lower values.

Springback behavior and a new chord modulus model of copper alloy during severe plastic compressive deformation

Abstract The copper alloy in the unloading process after severe plastic compressive deformation (SPCD) exhibits obvious nonlinear stress-strain relationship and hysteresis behavior, and generates severe springback deformation. The severe strain hardening and softening effects occurring in the SPCD and the anisotropy of the material will affect the springback behavior of the material. In this paper, the samples obtained along the different directions (rolling direction, short-thickness direction, transverse direction, and 45° direction) of copper alloy hot-rolled plates were used to perform the quasi-static single pass compression tests with different deformation ratios (0.25 %–90 %). The springback behavior of the copper alloy under the SPCD was investigated. The effects of the strain hardening, strain softening and anisotropy on the springback behavior of the material were revealed. The variation relationships of the instantaneous tangent modulus and the chord modulus in unloading with stress and strain at different deformation stages (elastic stage, yield stage, strain hardening stage, and strain softening stage) were analyzed. A new chord modulus in a power exponential form was proposed. According to the unloading characteristic of the SPCD, the Yoshida-Uemori chord modulus model and the QPE model were modified. The applicability and accuracy of the unloading chord modulus models for the SPCD were evaluated and compared by using the power exponential chord modulus model, the modified QPE chord modulus model, the modified Yoshida-Uemori chord modulus model, and the Yoshida-Uemori chord modulus model, respectively. Besides, based on the proposed chord modulus model in a power exponential form, a 1-D E T model in a power exponential form was also proposed to describe the nonlinear unloading process and the variation of the slope of the unloading curves after the SPCD. The results indicated that the springback behavior of SPCD is obviously different from those of small plastic compressive deformation and elastic compressive deformation. The proposed chord modulus model in a power exponential form can accurately predict the chord modulus and springback strain in the unloading after the SPCD.

Assessment of Native Human Articular Cartilage: A Biomechanical Protocol.

Recapitulating the mechanical properties of articular cartilage (AC) is vital to facilitate the clinical translation of cartilage tissue engineering. Prior to evaluation of tissue-engineered constructs, it is fundamental to investigate the biomechanical properties of native AC under sudden, prolonged, and cyclic loads in a practical manner. However, previous studies have typically reported only the response of native AC to one or other of these loading regimes. We therefore developed a streamlined testing protocol to characterize the elastic and viscoelastic properties of human knee AC, generating values for several important parameters from the same sample. Human AC was harvested from macroscopically normal regions of distal femoral condyles of patients (n = 3) undergoing total knee arthroplasty. Indentation and unconfined compression tests were conducted under physiological conditions (temperature 37 °C and pH 7.4) and testing parameters (strain rates and loading frequency) to assess elastic and viscoelastic parameters. The biomechanical properties obtained were as follows: Poisson ratio (0.4 ± 0.1), instantaneous modulus (52.14 ± 9.47 MPa) at a loading rate of 1 mm/s, Young's modulus (1.03 ± 0.48 MPa), equilibrium modulus (7.48 ± 4.42 MPa), compressive modulus (10.60 ± 3.62 MPa), dynamic modulus (7.71 ± 4.62 MPa) at 1 Hz and loss factor (0.11 ± 0.02). The measurements fell within the range of reported values for human knee AC biomechanics. To the authors' knowledge this study is the first to report such a range of biomechanical properties for human distal femoral AC. This protocol may facilitate the assessment of tissue-engineered composites for their functionality and biomechanical similarity to native AC prior to clinical trials.

The Interrelated Mechanics of Poroelastic Gels in Time- and Frequency-Domain Detected by Indentation

The force response of poroelastic materials including poroelastic gels to indentation is known to be time- and space-dependent (i.e., a function of indenter shape and size). Despite the complexity of the poroelastic response and in contrast to viscoelastic mechanics, poroelastic mechanics can be captured in terms of several intrinsic mechanical properties, such as elasticity, permeability, and Poisson ratio. While these intrinsic properties can be found from time-domain or frequency-domain master curves, indentation is usually conducted and analyzed only in the time domain using stress-relaxation or creep experiments. This paper advocates using frequency-domain analysis of poroelastic gels by reviewing and analyzing the relevant works of the literature. The analysis and methods, proposed here, enable researchers to characterize dynamic moduli of poroelastic gels in frequency domain using only a few experimental defining parameters. The authors have intentionally provided extensive details and background, to make this work useful for researchers who consider using frequency-domain analysis for the first time. This work reviews and explains the instantaneous elastic modulus, depicted over normalized time as a unifying and understandable set of master curves for time-domain stress relaxation tests on poroelastic gels for cylindrical, conical, and spherical indenters. The dynamic elastic modulus, depicted over normalized frequency, are derived symbolically and numerically and explained for the first time as master curves with simple transfer function in the frequency domain for presenting poroelastic mechanics of gels.

ОТХОДЫ ДРЕВЕСИНЫ И СТЕКЛОВОЛОКНО В КОМПОЗИЦИОННЫХ МАТЕРИАЛАХ ДЛЯ ИЗДЕЛИЙ ТРАНСПОРТНОГО СТРОИТЕЛЬСТВА

The results of experimental-theoretical work on the creation of new polymeric materials based on wood waste are considered. This material can be used in the outer layers of a wood-based polymer fiberglass composite in order to increase its strength properties. Instantaneous elastic moduli, conditional tensile strengths, and Poisson's ratio were determined, and the potential chemical activity of the components of the wood-based polymer fiberglass composite was revealed. The fiberglass polymer composite on the furfural-acetone monomer showed good performance when used as a structural composite of containers for storing aggressive liquids, chemically resistant tiles for shop floors, etc., which are exposed to electric current, aggressive liquids, and temperature. This material can be used in wood chemical production, capacities of energy chemical plants, furfural production, as well as in the outer layers of wood-based polymer fiberglass composite in order to increase its strength properties, specifically crack resistance. The basic compositions of the polymer fiberglass composite and its basic regulatory mechanical characteristics are given. This development is a kind of continuation of the theme of the use of forest industry waste for the production of competitive composite materials. This material will allow to utilize a huge amount of forest industry waste. In addition, the use of wood waste as a building material will make it possible to replace wood in some areas, which in turn will reduce logging and increase woodworking efficiency. All this will undoubtedly lead to an improvement in the ecological situation.

Tissue optical properties combined with machine learning enables estimation of articular cartilage composition and functional integrity.

Absorption and reduced scattering coefficients ( ) of biological tissues have shown significant potential in biomedical applications. Thus, they are effective parameters for the characterization of tissue integrity and provide vital information on the health of biological tissues. This study investigates the potential of optical properties ( ) for estimating articular cartilage composition and biomechanical properties using multivariate and machine learning techniques. The results suggest that μa could optimally estimate cartilage proteoglycan content in the superficial zone, in addition to its equilibrium modulus. While could effectively estimate the proteoglycan content of the middle and deep zones in addition to the instantaneous and dynamic moduli of articular cartilage.

Time-dependent behaviour of clay-concrete interfaces with different contact surface roughnesses under shear loading

Mechanical properties of the interface between a pile and soil greatly affect the bearing capacity of a pile. The creep of soil causes a long-term strength of the pile–soil interface to be smaller than its instantaneous shear strength. It is helpful to understand the settlement deformation and strength characteristics of friction piles from the micromechanism by studying the shear creep mechanical properties of the clay–concrete interface. In this work, we carry out shear creep tests on the interfaces between clay and concrete slabs with different roughnesses under different normal stresses. We analyze the influence of the joint roughness coefficient (JRC) on the long-term cohesion and long-term friction angle of the interface. We propose an instantaneous damage factor of the shear modulus and improve the Nishihara creep model with the instantaneous damage effect of the shear modulus. The experimental results show: (1) the whole process test curve of the shear creep shows that the specimen is rapidly destroyed after the transient creep stage and the steady-state creep stage, but the tertiary creep stage is not obvious. (2) The long-term shear strength of the clay-concrete interface is greatly affected by the change in the normal stress under the same JRC conditions, and the long-term shear strength of the interface increases linearly with increasing normal stress. (3) The relationship between the long-term shear strength and normal stress of the interface can be described by the Mohr–Coulomb failure criterion, and the long-term cohesion and long-term friction angle under different JRC conditions can be calculated accordingly. There exists a critical value JRCcr for the long-term cohesion, and the long-term cohesion of the interface first increases and then decreases as the JRC increases. When the long-term cohesion of the interface decreases to a certain extent, it fluctuates around the long-term cohesion value of clay. Moreover, the long-term friction angle of the interface fluctuates slightly with varying JRC, and there is no obvious change rule. (4) Considering the instantaneous damage of the shear modulus, we establish a relationship between the instantaneous shear modulus and the damage factor and introduce the damage factor into the Nishihara creep model. The shear creep mechanical parameters of the clay–concrete specimens under multistage loading are inversed.

Violation of the Stokes–Einstein relation in Ge2Sb2Te5, GeTe, Ag4In3Sb67Te26, and Ge15Sb85, and its connection to fast crystallization

Phase-change materials (PCMs) are already commercialized in optical and non-volatile memory devices. Yet, the dynamics of atomic rearrangement processes and their temperature dependence, which govern their ultrafast switching, are still not fully understood. Here we use quasi-elastic neutron scattering to investigate the liquid-state dynamics of four prevailing PCMs Ge2Sb2Te5, GeTe, Ag4In3Sb67Te26(AIST), and Ge15Sb85 above their respective melting points Tm. Self-diffusion coefficients and structural relaxation times on the timescale of picoseconds are extracted from dynamic structure factors. The results indicate an unusual systematic violation of the Stokes-Einstein relation (SER) for each PCM in high-temperature regions above Tm, where the atomic-mobility is high. This is likely related to the formation of locally favored structures in liquid PCMs. Absolute values of diffusivity in the supercooled liquid AIST are derived from crystal-growth velocity, which are almost one order of magnitude higher than that expected from the SER in the technologically relevant temperature range ~20% below Tm. This is relevant to understand the crystallization kinetics of PCMs as crystal growth is controlled by diffusivity. Furthermore, the instantaneous shear modulus is determined ranging from 2 to 3 GPa for liquid PCMs, which permits extracting viscosity from microscopic structural relaxations usually accessible to simulations and scattering techniques.

Alteration of structural and mechanical properties of the temporomandibular joint disc following elastase digestion.

The temporomandibular joint disc is a fibrocartilaginous structure, composed of collagen fibers, elastin fibers, and proteoglycans. Despite the crucial role of elastin fibers in load‐bearing properties of connective tissues, its contribution in temporomandibular joint disc biomechanics has been disregarded. This study attempts to characterize the structural–functional contribution of elastin in the temporomandibular joint disc. Using elastase, we selectively perturbed the elastin fiber network in porcine temporomandibular joint discs and investigated the structural, compositional, and mechanical regional changes through: (a) analysis of collagen and elastin fibers by immunolabeling and transmission electron microscopy; (b) quantitative analysis of collagen tortuosity, cell shape, and disc volume; (c) biochemical quantification of collagen, glycosaminoglycan and elastin content; and (d) cyclic compression test. Following elastase treatment, microscopic examination revealed fragmentation of elastin fibers across the temporomandibular joint disc, with a more pronounced effect in the intermediate regions. Also, biochemical analyses of the intermediate regions showed significant depletion of elastin (50%), and substantial decrease in collagen (20%) and glycosaminoglycan (49%) content, likely due to non‐specific activity of elastase. Degradation of elastin fibers affected the homeostatic configuration of the disc, reflected in its significant volume enlargement accompanied by remarkable reduction of collagen tortuosity and cell elongation. Mechanically, elastase treatment nearly doubled the maximal energy dissipation across the intermediate regions while the instantaneous modulus was not significantly affected. We conclude that elastin fibers contribute to the restoration and maintenance of the disc resting shape and actively interact with collagen fibers to provide mechanical resilience to the temporomandibular joint disc.

An ultrasound-based approach for the characterization of fluid–structure interaction of large arterial vessels

An ultrasound-based approach to characterize the fluid–structure interaction in large arterial vessels is presented. The ultrasound-based data are fed into a new dynamic model accounting for a two-dimensional (2D) stress state, which in turn provides a better estimate of the material elasticity under dynamic loading. In order to validate the semi-empirical model, a compliant, synthetic vessel was subjected to a range of pulsatile and steady flow profiles. Ultrasound imaging was used to capture the flow field through the compliant vessel and its change in diameter over time. Internal pressure was extracted from ultrasound image velocimetry using spatial integration of the Navier–Stokes equation, and used to find the pressure–area relationship. Two constitutive laws describing a one-dimensional expansion of a cylindrical vessel, the Laplace law and one from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999), were also used to estimate the instantaneous elastic modulus. A uniaxial tensile test of the vessel material was performed to provide validation criteria. Under steady flow, the Laplace law predicted the elasticity of the vessel material with 255% error and the results from Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) had an error of 99%. In contrast, our developed 2D stress model predicted the elasticity with less than 10% error. The Laplace law and the Olufsen (Am J Physiol-Heart Circul Physiol 276(1):H257–H268, 1999) model were revealed to be flow-dependent such that the trend of the resultant elastic modulus varied for each pulsatile flow case. However, the 2D stress model showed no flow dependency, presenting consistent elasticity results across all test cases.

Tuning Viscoelasticity with Minor Changes in Speed of Sound in an Ultrasound Phantom Material

The acoustic properties of ultrasound phantom materials have always been important, but with new applications interrogating tissue mechanical properties, viscoelasticity has also become an interesting feature to consider. Along with Young's modulus, the viscous component of tissue is affected by certain diseases and can therefore be used as a biomarker. Furthermore, viscoelasticity varies between tissue types and individuals, and therefore it would be useful with a phantom material that reflects this physiological range. Here we describe a gel for ultrasound imaging with a range of mechanical properties given by mixing different ratios of two oil-based gels, clear ballistic and styrene–ethylene/butylene–styrene (SEBS). The gels were mixed in five different proportions, ranging from 0–100% of either gel. For each of the gel compositions, we measured time of flight to determine speed of sound, narrowband ultrasound transmission for attenuation, stress–relaxation for viscoelasticity, mass and volume. Analysis of the stress–relaxation data using the generalized Maxwell model suggests that the material can be described by five parameters, E0, E1, E2, η1 and η2, and that each of these parameters decreases as more SEBS is incorporated into the mixed material. Instantaneous Young's modulus (the sum of E0, E1 and E2 in our model) ranges between 49 and 117 kPa for the different ratios, similar to values reported for cancerous tissue. Despite the large span of obtainable mechanical properties, speed of sound is relatively constant regardless of composition, with mean value estimates (± 95 % CI) between 1438 ± 9 and 1455 ± 3 m/s for pure and mixed gels. This was attributed to a variation in density and Poisson's ratio, following from the relation linking them to speed of sound and elasticity. Furthermore, both speed of sound and attenuation were within a suitable range for ultrasound phantoms. Combining this ballistic gel with SEBS copolymer in oil allows for control of mechanical properties, both elastic and viscous as evaluated by the material model. Furthermore, it does so without compromising ease of use, longevity and safety of the pre-made gel.

In-situ characterization of the local mechanical behaviour of polymer matrix in 3D carbon fiber composites by cyclic indentation test

In this work, a cyclic indentation test is employed for the in-situ characterisation of the local mechanical properties of a PR520 epoxy resin matrix in a 3D carbon fiber composite. Since the evolution of indentation response with time is studied, the cyclic loading allows to characterise both the elastic and the time dependent, viscoelastic, mechanical response of the material simultaneously. The 3D carbon fiber composite used in this study contains a number of large resin pockets between fiber bundles (mesoscopic scale) with a characteristic dimension ranging from several hundred of micrometers to several millimeters. The mechanical behaviour of the polymer matrix is investigated on the external surface and in volume of the composite and compared with the neat polymer. The instantaneous elastic modulus from reloading, the energy ratio and the residual depth are determined from the cyclic material response and compared through a Student t-test based statistical analysis. Results show that there is at least 95% of probability that the neat and in-situ polymer matrix material belong to different populations. However, this difference is rather small (between 1 and 2.5%) and almost constant with cycles. Moreover, a difference between composite core and surface was measured.

Mesenchymal stem cells-derived cartilage micropellets: A relevant in vitro model for biomechanical and mechanobiological studies of cartilage growth.

The prevalence of diseases that affect the articular cartilage is increasing due to population ageing, but the current treatments are only palliative. One innovative approach to repair cartilage defects is tissue engineering and the use of mesenchymal stem/stromal cells (MSCs). Although the combination of MSCs with biocompatible scaffolds has been extensively investigated, no product is commercially available yet. This could be explained by the lack of mechanical stimulation during in vitro culture and the absence of proper and stable cartilage matrix formation, leading to poor integration after implantation. The objective of the present study was to investigate the biomechanical behaviour of MSC differentiation in micropellets, a well-defined 3D in vitro model of cartilage differentiation and growth, in view of tissue engineering applications. MSC micropellet chondrogenic differentiation was induced by exposure to TGFβ3. At different time points during differentiation (35days of culture), their global mechanical properties were assessed using a very sensitive compression device coupled to an identification procedure based on a finite element parametric model. Micropellets displayed both a non-linear strain-induced stiffening behaviour and a dissipative behaviour that increased from day 14 to day 29, with a maximum instantaneous Young's modulus of 179.9±18.8kPa. Moreover, chondrocyte gene expression levels were strongly correlated with the observed mechanical properties. This study indicates that cartilage micropellets display the biochemical and biomechanical characteristics required for investigating and recapitulating the different stages of cartilage development.

Experimental study, phenomenological and adaptive neuron analysis of creep property of Momordica augustisepala L nanofiber reinforced polyvinyl alcohol polymer film composite

The viscoelastic property of packaging material affects foods’ postharvest management and biophysical quality preservation of food. This study investigated the creep viscoelastic property of neat polyvinyl alcohol film and polyvinyl alcohol film reinforced Momordica augustisepala nanofiber composite. The applicability and comparison of Burger phenomenological and Adaptive neuron model to analyze the creep data were investigated. The instantaneous modulus and creeping speed of neat and reinforced polyvinyl alcohol were 7.53710 MPa, 10.27580 MPa and 3.00590 MPa.s, 2.85391 MPa.s, respectively. The coefficient of determination of Burger model prediction was 0.99889 and 0.99972 for neat and composite polyvinyl alcohol film, while the coefficient of determination of Adaptive neuron model was 0.99986 for both neat and reinforced polyvinyl alcohol film. The Momordica augustisepala nanofiber improved the creep viscoelastic property of polyvinyl alcohol film and Adaptive neuron model showed superiority over Burger model in prediction of experimental data. The results are vita in material design, life prediction and usage prescription.

Magnetization-affected localized flows in ferromagnetic metallic glass

In this paper, the interaction between magnetization and dynamic relaxation of heterogeneous structure in a ferromagnetic metallic glass (MG) is investigated. It is found that the magnetic state of the MG can be changed through wearing its surface. Accompanying with the change of magnetic state, the local dynamic mechanical behavior of the MG was detected by nanoindentation varies. Through analyzing with combination of the three-parameter viscoelastic model and state-transition theory, it is discovered that the microstructure of the glass can be apparently changed by magnetization with the effective size, viscosity of the liquid-like cores and the relaxation time increased by more than 3 times. Inversely, with cycling loading below the elastic limit of the MG using nanoindentation, it is revealed that localized flows of nano-liquid in the glass erase the effect of magnetization. The interaction between magnetization and localized flows relates to spin-orbit coupling in the MG; the change of magnetic state and liquid-like regions in the MG does not affect its instantaneous shear modulus associated with its ideal glassy state. The studies help understand the dynamic magneto-mechanical properties of amorphous magnetic materials, and have technological importance for their applications.

Instantaneous shear modulus of Yukawa fluids across coupling regimes

The high frequency (instantaneous) shear modulus of three-dimensional Yukawa systems is evaluated in a wide parameter range from the very weakly coupled gaseous state to the strongly coupled fluid at the crystallization point (Yukwa melt). This allows us to quantify how shear rigidity develops with increasing coupling and inter-particle correlations. The radial distribution functions (RDFs) needed to calculate the excess shear modulus have been obtained from extensive molecular dynamics (MD) simulations. MD results demonstrate that fluid RDFs appear quasi-universal on the curves parallel to the melting line of a Yukawa solid in accordance with the isomorph theory of Roskilde-simple systems. This quasi-universality allows us to simplify considerably calculations of quantities involving integrals of the RDF (elastic moduli represent just one relevant example). The calculated reduced shear modulus grows linearly with the coupling parameter at weak coupling and approaches a quasi-constant asymptote at strong coupling. The asymptotic value at strong coupling is in reasonably good agreement with the existing theoretical approximation.

Rheological and tribological characteristics of mung bean-rice porridge and its impact on sensory evaluation

ABSTRACT In this study, mung beans were added to rice porridge as supplementary cereal at 0%, 25%, 50%, 75%, and 100% (beans/100 g total mixture), respectively to investigate the effect of mung beans on the rheological and frictional properties of rice porridge. During the frequency scanning experiment, the storage modulus (G’) of all samples was more substantial than the loss modulus (G’’). Moreover, the data obtained from the creep-recovery tests were modeled using Berger’s model. The addition of mung beans also increased the instantaneous elastic modulus (E1 ) and retarded elastic modulus (E2 ) values. In tribology test, the friction curves of the mung bean-rice porridge did not resemble the traditional Stribeck curve and with the increase of mung bean addition ratio and it was more difficult for the fluid (porridge) to enter the next zone. Furthermore, the sensory evaluation indicated that the rice porridge containing 25% and 50% mung beans represented the highest overall preference among evaluators. This study provided theoretical support for finding the relationship between rheology and sensory characteristics of porridges.

Effects of the high-pulsed electric field pretreatment on the mechanical properties of fruits and vegetables

A high-pulsed electric field (HPEF) technique show potentials to reduce the drying time and energy consumption of a vacuum freeze-drying technique, which can maintain the nutritional and sensory properties of the foods. It is important to understand effects of the HPEF treatment and the optimized operation parameters on changing the mechanical properties of fruits and vegetables for improvement of the vacuum freeze-drying process. The viscoelastic properties of four types of fruits and vegetables with and without the HPEF pretreatment were studied using experimental measurements of the stress relaxation and creep of the fruits and vegetables. The stress relaxation parameters of the fruits and vegetables were estimated according to the Generalized Maxwell model. The values of the equilibrium elastic modulus (Ee) decreased more than 92%, and relaxation time (T) values decreased more than 17%, after HPEF pretreatment. The creep parameters of the fruits and vegetables were estimated according to the Burger four-parameter model. The values of the instantaneous elastic modulus (E0) decreased more than 70%, the retarded elastic modulus (Er) decreased more than 92%, and the viscosity coefficient (ηr) decreased more than 94% after the HPEF pretreatment. The results showed that the HPEF pretreatment improved the vacuum freeze-drying process.

Experimental study on the mechanical properties of short-term creep in post-peak rupture damaged sandstone

The creep of rock is a slow stress adjustment deformation and an evolutional process of rock mass destruction. Therefore, rock creep plays a vital role in a variety of rock engineering. To reveal the creep properties of rock, the following work has been done. A series of triaxial creep tests has been conducted considering different low confining pressures. The creep curve is analyzed under different confining pressures, and the creep law of each stage is obtained. Many results were obtained for the influence of confining pressure on the instantaneous modulus of deformation, creep strain, creep rate and instantaneous strain. The proportion of the various stages of creep changes under different confining pressure. Due to the existence of confining pressure, the ultimate failure method of rock has also been affected. Creep data can then be fitted by the improved Nishihara model, revealing a good relationship. The conclusion of this paper can provide some significant guidance for rock engineering.