Steady-state Creep Research Articles

Influence of Ta on the intermediate temperature creep behavior of a single crystal superalloy

The influence of Ta on the intermediate temperature creep behavior and deformation mechanism in a Ni-based single crystal superalloy has been investigated at 760 oC and 750 MPa. The results indicate that there is a significant increasing of creep rupture life after the addition of Ta. Lattice misfit between γ and γ′ phase at 760 oC increases in the Ta-containing alloy. Microstructure showed that the formation of stacking faults in the γ matrix and denser dislocation network at the γ/γ′ interfaces caused by Ta addition are found during the primary creep stage. And a large amount of stacking fault locks which act as an important pattern in the strengthening generate in the γ′ precipitates, resulting in a lower steady state creep rate and longer steady state creep life in Ta-containing alloy. And possible formation mechanism of the stacking fault locks is also discussed.

Creep Rupture and Permeability Evolution in High Temperature Heat-Treated Sandstone Containing Pre-Existing Twin Flaws

Utilizing underground coal gasification cavities for carbon capture and sequestration provides a potentially economic and sustainable solution to a vexing environmental and energy problem. The thermal influence on creep properties and long-term permeability evolution around the underground gasification chamber is a key issue in UCG-CCS operation in containing fugitive emissions. We complete multi-step loading and unloading creep tests with permeability measurement at confining stresses of 30 MPa on pre-cracked sandstone specimens thermally heat-treated to 250, 500, 750 and 1000 °C. Observations indicate a critical threshold temperature of 500 °C required to initiate thermally-induced cracks with subsequent strength reduction occurring at 750 °C. Comparison of histories of creep, visco-elastic and visco-plastic strains highlight the existence of a strain jump at a certain deviatoric stress level—where the intervening rock bridge between the twin starter-cracks is eliminated. As the deviatoric stress level increases, the visco-plastic strains make up an important composition of total creep strain, especially for specimens pre-treated at higher temperatures, and the development of the visco-plastic strain leads to the time-dependent failure of the rock. The thermal pre-treatment produces thermal cracks with their closure resulting in increased instantaneous elastic strains and instantaneous plastic strains. With increasing stress ratio, the steady-state creep rates increase slowly before the failure stress ratio but rise suddenly over the final stress ratio to failure. However, the pre-treatment temperature has no clear and apparent influence on steady creep strain rates. Rock specimens subject to higher pre-treatment temperatures exhibit higher permeabilities. The pre-existing cracks close under compression with a coplanar shear crack propagating from the starter-cracks and ultimately linking these formerly separate cracks. In addition, it is clear that the specimens pre-treated at higher temperatures accommodate greater damage.

Short-term creep and low cycle fatigue unified criterion for a hybridised composite material

The objective of this work is to determine a low cycle fatigue criterion for a thermoplastic matrix composite reinforced with both short and continuous fibres. The proposed criterion is based on the steady state creep strain rate and unifies the results for different fibre orientations, stress ratio, frequency and water content. The criterion is applicable in low cycle fatigue and creep. By means of this criterion, the Monkman–Grant relationship is verified both for creep and low cycle fatigue and offers interesting perspectives for numerical approaches.

Ultra-high-temperature creep behavior of a single-crystal nickel-based superalloy containing 6% Re/5% Ru

The creep behavior and influence factors of a nickel-based single-crystal superalloy containing 6% Re/5% Ru (mass fraction) at ultra-high-temperatures were studied through microstructural observations and ultra-high-temperature creep property measurements. The results indicated that the alloy's creep life at 1170 °C/110 MPa was 193 h. During steady-state creep, the alloy's deformation mechanism involved a large number of dislocations sliding in the γ matrix and climbing over the rafted γ' phases. With the increase in the content of refractory elements, the resistance of dislocation movement in the γ matrix increased. In the later stage of ultra-high-temperature creep, the dislocations shearing into the γ' phase could cross-slide from the {111} plane to the {100} plane to generate the Kear–Wilsdorf (K-W) dislocation locks. A greater number of K-W dislocation locks could inhibit the sliding and cross-sliding of dislocations to enhance the alloy resistance, which was one of the reasons for the smaller strain rate and better creep resistance. The larger effective stress in the necking area could initiate the dual-orientation slip of the dislocations, causing the rafted phase to twist. Crack initiation occurred in the kinking area. The initiated crack propagated along the direction perpendicular to the stress axis and expanded until fracture. This process was considered to be the alloy's deformation and damage mechanism during ultra-high-temperature creep. The Ru dissolved in γ' phase could replace Al atoms. The interactions of Ru with Re and W atoms in the high-concentration Re/Ru alloy caused more Re and W atoms to dissolve in the γ' phase, delaying elemental diffusion and depressing dislocation movement. This was the main reason for the retention of more K-W dislocation locks and the good resistance during creep at ultra-high temperatures.

Loading rate sensitivity of nickel-based single crystal superalloys characterized by nanoindentation

Nickel-based single crystal superalloys (NBSX) are extensively applied in advanced aero-engine and gas turbine blades. In this work, a new method is proposed to investigate the sensitivity of loading rate on the mechanical behavior of NBSX along the [001] direction by nanoindentation tests with different indenters. Based on the reduced modulus, the load-depth curves of a pyramidal indenter are corrected to eliminate the influence of indentation size effect and pile-up or sink-in. Results show that the hardness of NBSX increases with the loading rate, indicating the loading rate hardening effect. In the process of indentation, there is a certain softening effect. With the increase of loading rate, the creep displacement/strain rate of NBSX increases. In contrast to creep displacement, the creep strain rate declines quickly at the initial holding stage and then decreases slowly to a steady-state creep stage.

Rheological stratification in impure rock salt during long-term creep: morphology, microstructure, and numerical models of multilayer folds in the Ocnele Mari salt mine, Romania

Abstract. At laboratory timescales, rock salt samples with different composition and microstructure show variance in steady-state creep rates, but it is not known if and how this variance is manifested at low strain rates and corresponding deviatoric stresses. Here, we aim to quantify this from the analysis of multilayer folds that developed in rock salt over geological timescale in the Ocnele Mari salt mine in Romania. The formation is composed of over 90 % of halite, while distinct multiscale layering is caused by variation in the fraction of impurities. Regional tectonics and mine-scale fold structure are consistent with deformation in a shear zone after strong shearing in a regional detachment, forming over 10 m scale chevron folds of a tectonically sheared sedimentary layering, with smaller folds developing on different scales in the hinges. Fold patterns at various scales clearly indicate that during folding, the sequence was mechanically stratified. The dark layers contain more impurities and are characterised by a more regular layer thickness compared to the bright layers and are thus inferred to have higher viscosities. Optical microscopy of gamma-decorated samples shows a strong shape-preferred orientation of halite grains parallel to the foliation, which is reoriented parallel to the axial plane of the folds studied. Microstructures indicate dislocation creep, together with extensive fluid-assisted recrystallisation and strong evidence for solution–precipitation creep. This provides support for linear (Newtonian) viscous rheology as a dominating deformation mechanism during the folding. Deviatoric stress during folding was lower than during shearing in the detachment at around 1 MPa. We investigate fold development on various scales in a representative multilayer package using finite-element numerical models, constrain the relative layer thicknesses in a selected outcrop, and design a numerical model. We explore the effect of different Newtonian viscosity ratios between the layers on the evolving folds on different scales. By comparing the field data and numerical results, we estimate that the effective viscosity ratio between the layers was larger than 10 and up to 20. Additionally, we demonstrate that the considerable variation of the layer thicknesses is not a crucial factor to develop folds on different scales. Instead, unequal distribution of the thin layers, which organise themselves into effectively single layers with variable thickness, can control deformation on various scales. Our results show that impurities can significantly change the viscosity of rock salt deforming at low deviatoric stress and introduce anisotropic viscosity, even in relatively pure layered rock.

Tensile creep behavior and mechanism of CoCrFeMnNi high entropy alloy

As a potential novel superalloy, the study on the creep of high entropy alloys is of great significance. Equiatomic ratio CoCrFeMnNi with a mass of 6.7 kg was fabricated by vacuum induction levitation melting. Dendrite structure is obtained for as-cast alloy while a homogeneous equiaxed grain structure can be formed after annealing at 1273 K for 6 h. The tensile creep behavior of as-annealed alloy at 773–973 K and 50–340 MPa is systematically studied. Apparent dynamic recovery and recrystallization occur for creep at 973 K while high dislocation density can be observed for creep at 923 K and lower temperatures. Results of EDS analyses on fractured surface, stress exponent and activation energy for steady state creep rate suggest that the creep mechanism should be the dislocation viscous glide dragged by solute Mn at low stresses and low temperatures and be the dislocation climb associated with Mn diffusion at high stresses and high temperatures.

Effect of indentation depth in impression creep test: conversion relationships and correction functions

ABSTRACT The impression creep test method has been used extensively to determine the in-service creep properties of power plant components from a small volume of material. In the standardisation of the impression creep test, the determination of a maximum ‘allowable’ indentation depth is an important issue. This paper presents the results of finite element analyses obtained using a simplified method based on steady-state creep, for evaluating the variation of conversion factors with indentation depth. The results obtained show that the indentation depth has a significant influence on the conversion parameters and the steady-state creep deformation rate when the indentation depth is sufficiently large. On this basis, recommendation on practical application of these conversion relationships was made to the users, and empirical formulas were provided for the possible corrections of the conversion factors. The effect of plastic zone due to initial loading on the subsequent creep was found to be insignificant.

The regularities of creep deformation and failure of the VVER’s pressure vessel steel 15Kh2NMFA-A in air and argon at temperature range 500–900 °C”

• Creep tension tests of VVER vessel steel 15Kh2NMFA-A at 500–900 °C in air and Ar and duration up to 100 hrs. • Test specimens were made of the fragment of unirradiated VVER-1000 RPV. • Secondary creep rate and time to failure were determined. • Singularity of creep process is due to the phase transformations in range from 770 to 820 °C. • The creep mechanism in 15Kh2NMFA-A steel is the same in temperature range from 700 to 900 °C. The paper presents the results of the determination the creep strength properties and both the microstructure and regularities of high-temperature creep behavior of unirradiated ferritic-pearlitic steel 15Kh2NMFA-A within the temperature range from 500 to 900 °C and the creep process duration up to 100 h. It is extremely necessary to obtain the such experimental data characterizing the creep strength properties of this steel under the condition of high-temperature creep to predict the behavior of the VVER’s RPV structure in the severe accident when the pressure vessel structure undergoes both force and high-intensive thermal action from the melted core materials. This ferritic-pearlitic steel 15Kh2NMFA-A (2% Cr, 1% Ni, 0.5% Mn, 0.5% Mo) is one of basic steel types used in fabrication of reactor pressure vessels of the VVER type designed in Russia. This investigation included several series of creep tension tests of the specimens made of 15Kh2NMFA-A steel. In addition, an analysis of the microstructure of the steel under study was carried out for a number of samples after the creep tests. For the creep tests, several sets of specimens made of the fragment of unirradiated VVER-1000 RPV. The specimen’s working part was 8 mm in diameter and the gauge length was ~50 mm. Isothermal creep tests under uniaxial tension were carried out in air up to 650 °C and in shielding argon medium within the temperature range from 700 to 900 °C. Basing on mathematical processing of test results, the values of steady-state creep rate and the values of corresponding parameters ( B ) and ( n ) were determined. The analysis of obtained results showed that within the temperature range from 750 to 900 °C, the creep mechanism of 15Kh2NMFA-A steel is the same. A sharp variation of parameters ( B ) and ( n ) (describing the steady-state creep rate of this steel) is observed within the temperature range from 500 to 750 °C. At temperature of more than 750 °C, the value log( B ) is varied within the range from −9.65 to −8.48 and the values of parameter ( n ) are within the range from 4.72 to 4.82. The results of creep tests show that both creep failure time and secondary creep rate values of the 15Kh2NMFA-A steel at 800 °C coincide very closely with the analogous ones for the specimen tests under analogous conditions at 850 °C. It is obvious that such singularity is due to the simultaneous presence of several phases in the 15Kh2NMFA-A steel during the phase transformations in temperature range from 770 to 820 °C. The formation of oxide layer on the specimen surface under the creep condition in air at temperature of 800 °C and more than the given one changes considerably the model of deformation and fracture of the investigated steel under the creep condition. We defined the parameters for the constitutive equation of the Larson-Miller type (LMP) for this steel by statistical processing the results of creep tests within the temperature range from 500 to 900 °C. The analysis of the obtained LMP equation for this steel revealed an important fact that within the range of temperature values Ac1-Ac3, where microstructure transformations of steel take place, we observe essential differences between experimental data and corresponding values defined by using the obtained LMP dependence. When estimating rupture time of this steel under the condition of high-temperature creep, such a difference between the specified values results in a considerable error (by more than the order of magnitude).

Experimental Studies of Creep of Unidirectional Composite Material of Composite Overwrapped Pressure Vessel

Experimental studies of creep of a composite material of a composite overwrapped pressure vessel are presented. Composite material was an unidirectional tape based on IMS60 carbon fibers and epoxy resin. Creep tests were carried out at various loads and temperatures, taking into account the stress level in structure and measured glass transition temperature of the material. For testing, special equipment was used to install specimens in the grips of the testing machine. According to the test results, the creep curves were obtained. Creep curves according to Findlay's model are presented. For the stage of steady-state creep, the variation of the creep rate at different temperatures were determined, and the average value of the creep rate was calculated for all tested specimens. The results of the obtained data can be used in numerical models for predicting strains of a composite overwrapped pressure vessel under creep conditions

Effect of Heat Treatment on Microstructure and Creep Behavior of Fe-40Ni-24Cr Alloy

Iron-nickel-chromium (Fe-Ni-Cr) alloy Haynes HR120 is an iron-nickel-based superalloy, which is extensively used in gas turbines. Hence, the materials for the fabrication of steam turbine blades should present great mechanical characteristics and creep properties. In this study, Fe-40Ni-24Cr was heat-treated at temperatures from 950 to 1250 °C. High temperature creep behavior and microstructure evolution of the selected heat-treated (1050 °C, 1200 °C, 1225 °C and 1250 °C) Fe-40Ni-24Cr alloy were assessed at temperatures of 800 °C and 900 °C under 100 MPa stress. The alloy consisted of titanium and niobium rich precipitates, namely NbC, (Nb,Ti)C, TiN and Ti(C,N) distributed in the matrix grain boundaries, which enhance the creep properties of the alloy. The hardness of heat-treated Fe-40Ni-24Cr alloy decreased with increasing temperature and grain size. The creep strain of the Fe-40Ni-24Cr alloy increased with escalation in the creep time and the temperature being under constant applied stress. Fe-40Ni-24Cr alloy shows a decrease in steady-state creep rate with an increase in grain size from 62 μm to 183 μm due to the grain boundary sliding mechanism and 183 μm to 312 μm due to the occurrence of dislocation climb. This result exhibited that grain size has a significant influence on the alloys’ high temperature creep properties.

Analysis of Shear Characteristics of Deep, Anchored Rock Mass under Creep Fatigue Loading

To study the influence of earthquakes and engineering disturbances on the deformation of deeply buried rock masses, shear tests were carried out on anchored sandstone rock masses, anchored marble rock masses, and anchored granite rock masses under creep fatigue loading, and a new creep fatigue model was established to characterize the deformation characteristics of anchored rock masses under creep fatigue loading. The creep fatigue curves of different lithologies clearly show three stages: creep attenuation, steady-state creep, and accelerated creep. Fatigue loading can increase the creep of anchored specimens, and the lower the rock strength is, the higher the creep variable under fatigue loading is. However, for the same rock strength, with the increase in load level, the creep variable produced by creep fatigue load presents a linear downward trend. Considering the changes in the mechanical properties of the anchored rock mass under creep fatigue loading, the creep fatigue model of anchored rock masses is established by introducing a function of the fatigue shear modulus, and the accuracy and applicability of the model are verified by laboratory creep fatigue test data. The model provides a theoretical basis for the study of anchored rock mass support under low-frequency earthquakes or blasting loads.

Roles definition of TiN particles in enhancing the creep properties of IN718C high temperature alloys

In this study, a TiN/IN718C composite was prepared by employing spark plasma sintering and induction melting methods via the addition of TiN particles to an IN718C superalloy. The creep behavior of IN718C and TiN/IN718C at 704 °C under 500 MPa was comprehensively investigated. The creep test showed that the rupture life of TiN/IN718C was 421 h, which is approximately 1.7 times longer than that of IN718C. The steady-state creep rate of TiN/IN718C (2.81 ×10−9 s−1) was one order of magnitude lower than that of IN718C. The enhanced creep behavior was attributed to the microstructure of TiN/IN718C. During casting, the TiN particles could act as an inoculant to slightly refine the Ni matrix grains. TiN particles reduced the formation of detrimental phases such as Laves and δ, facilitated the precipitation of carbides, and refined the γ′′ phases in the IN718C matrix. In addition, the transmission electron microscopy results indicated a strong adhesive interface between TiN and the Ni matrix. Therefore, the synergetic strengthening effect of the dispersed TiN reinforcements and the refined microstructure of the IN718C matrix significantly enhanced the creep behavior of the TiN/IN718C composite.

Investigation on the Deformation Law of Inner Waste Dump Slope in an Open-Pit Coal Mine: A Case Study in Southeast Inner Mongolia of China

The settlement and deformation of an open-pit mine waste dump were investigated by using field monitoring and numerical methods. The creep parameters of fine soil sand in the dump fill were inverted using the steady Burgers creep model, and FLAC3D software was used to simulate the dumping soil construction and development program. The results show that the settlement displacement of the dump increases with the time of dumping soil and tends to be stable after 4 years. In the creep attenuation stage of the creep process, there is a big difference between the numerical calculation and the field monitoring results in the inversion process of fine-grained soil sand parameters. In the steady-state creep stage, the numerical calculation is consistent with the field monitoring value. The height of the fill has an influence on the settlement of the fill body of the dump and the time to reach the stability. The higher the filling height is, the greater the postconstruction settlement will be, and the longer it will take to reach stability. The pushing position of the fill body has a great influence on the settlement displacement of the dump. The time and efficiency of soil discharge can be shortened by optimizing the safe distance between the filling body and the river. Based on the numerical calculation results and the empirical settlement function, an analytical method for river channel location selection of internal dump is proposed.

Impression creep deformation behaviour of FSWed AA6061 at various weld zone

ABSTRACT Impressioncreep (IC) tests were performed at three welded regions viz: nugget zone (NZ), thermo-mechanical affected zone (TMAZ) and heat affected zone (HAZ) at 326°C, 359°C and 378°C of furnace temperature and equivalent stresses of 24MPa, 28MPa and 32MPa respectively. The high temperature deformation properties were estimated by employing power law creep equation and the results were compared with the base material (BM). The rate controlling mechanism of IC process at each selected area and its correlation with the microstructural evolution throughout FSW and IC procedures were realised. The steady-state creep rate of NZ was estimated to be the highest and of BM was the lowest. The other creep parameters such as the stress exponents and the apparent activation energy for the IC process were calculated at each localised zones for the welded material and were compared with the BM. The creep deformation was found to be homogeneous at all the selected testing areas and was of dislocation type. Creep rate was found to be affected by the grain size and testing temperature. Detail microstructural analysis of the samples before and after the IC test was performed by optical microscope.

Elevated-temperature Deformation Mechanisms in a CrMnFeCoNi High-Entropy Alloy

Stress reduction creep experiments were performed on a CrMnFeCoNi high-entropy alloy at 1073 K to characterize the steady-state and transient creep properties of this material. From measurements of constant-structure creep, the activation area for deformation of CrMnFeCoNi was determined to be ∼100 b2 and to decrease with increasing applied stress, indicating the presence of both concentrated solid solution and forest dislocation control of high temperature plastic deformation. With the aid of a recent solid solution theory for high entropy alloys, quantitative separation of the two mechanisms was carried out using a Haasen plot and the results show that creep in CrMnFeCoNi relies heavily on thermal activation with the majority of creep strength coming from solid solution hardening, especially at low applied stresses. The overall analysis conducted in this study reveals that steady-state creep deformation of CrMnFeCoNi at 1073 K can be adequately described by existing concentrated solid solution hardening models and forest dislocation hardening models. This observation suggests it may be possible to develop a unified treatment of the dislocation glide kinetics for this alloy from cryogenic to elevated temperatures.

Creep behaviour of WC-12 wt% Co hardmetals with different WC grain sizes tested in uniaxial tensile and compression step-loading tests at 700 °C and 800 °C

At elevated temperatures, the material behaviour of WC-Co hardmetals shows differences under similar loading conditions depending on WC grain size and Co-content. Variations in the chemical composition and microstructure in hardmetals cause different material properties such as strength or creep resistance. In the current work, the influence of WC grain size on creep mechanism and creep resistance was investigated for WC-12 wt% Co hardmetals with 0.4 μm, 0.7 μm and 2.0 μm average WC grain size. Specimens were tested in uniaxial tensile and compression step-loading creep tests at 700 °C and 800 °C under vacuum conditions. Time-dependent creep behaviour with steady-state secondary creep was observed for all hardmetal grades investigated, with specimens creeping faster under tensile than under compressive loading. At 700 °C, the medium-grained hardmetal grade exhibited the highest minimal creep rates ε̇min compared to the submicron and ultrafine-grained grades. In contrast, the ultrafine-grained hardmetal grade showed higher ε̇min at low stresses and 800 °C, because of the high amount of grain boundary area per unit volume, which is advantageous for vacancy diffusion at grain boundaries. Therefore, the ε̇min of the medium-grained hardmetal grade was less affected by temperature than that of the finer-grained grade. Also two stress exponent n-ranges were observed at 700 °C and 800 °C: At low stress levels, n was in the range of about 1. Above a critical stress level, n reached values between about 4 and 6. Beside the influence of the WC grain size on the creep mechanism and creep resistance, damage evolution with increasing stress levels was analysed for the ultrafine-grained grade at 800 °C. The microstructures of three compression step-loading creep tested specimens were examined after maximum stress levels of −350 MPa, −950 MPa and −1350 MPa. Microstructural investigations performed via scanning electron microscopy showed that more and larger cavities had formed at WC/WC interfaces and WC/Co phase boundaries in the specimen tested up to −1350 MPa compared to the ones tested up to −350 MPa and −950 MPa.

ɤ-TiAl alloy: revisiting tensile creep deformation behaviour and creep life at 832 °C

ABSTRACT Creep deformation in single-phase ɤ-TiAl alloys manufactured using different processing techniques has been an extensively studied topic owing to the high specific strength and excellent creep properties of these alloys at temperatures between 760 and 1000°C. In addition, these lightweight and creep-resistant alloys are being presently considered as replacements to the comparatively heavier Ni-based superalloys for application in the low-pressure turbine blades of the next-generation gas turbine engines. However, there is limited information on the tensile creep deformation behaviour and creep life of ɤ-TiAl alloys at 832°C where these alloys have been reported not to exhibit steady-state creep. To this end, the present work revisits the work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Saha [1] and is aimed to develop an understanding of the tensile creep deformation behaviour at 832°C and the influence of creep activation energy on the creep life of wrought single-phase ɤ-TiAl alloy for stress levels of 69.4 and 103.4 MPa at 832°C using Monkman–Grant [2] approach.

Creep Behavior of Near α High Temperature Ti-6.6Al-4.6Sn-4.6Zr-0.9Nb-1.0Mo-0.32Si Alloy

This study focuses on the microstructure characteristics and tensile and creep properties of a near α high temperature Ti-6.6Al-4.6Sn-4.6Zr-0.9Nb-1.0Mo-0.32Si alloy. Microstructure characteristics were quantitatively investigated using optical microscopy, scanning electron microscope, and transmission electron microscopy. Tensile properties were carried out at room and high temperature. Creep properties were detected under applied stresses ranging from 100–350 MPa at 873–973 K, respectively. Results showed that Widmanstätten microstructure was obtained after hot forged and heat treatment. The strength decreases and the elongation rises with temperature increasing. The ultimate strength and elongation were 1010 MPa, 12% at room temperature, and 620 MPa, 20% at 923 K, respectively. The steady state creep rates rise correspondingly with stress and temperature. Stress exponents are measured within the range of 3.0–3.5. Thus, the creep mechanism is diffusion-controlled viscous glide of dislocation. Ti3Al precipitates are observed. The boundaries and precipitates can obstruct dislocation movement to improve the creep properties. Fracture mechanism of creep is intergranular. The creep mechanism varied from climb of dislocation to sliding of dislocation solution.

Predictive Mechanistic Model of Creep Response of Single-Layered Pressure-Sensitive Adhesive (PSA) Joints.

This paper explores the uniaxial tensile creep response of acrylic-based pressure-sensitive adhesive (PSA), which exhibits a unique multi-phase creep response that does not have the classical steady-state region due to multiple transitions caused by several competing mechanisms: (i) cavity nucleation and growth in the interior of the adhesive material of the PSA system, as well as at the interfaces between the PSA and the substrate; (ii) fibrillation of the bulk adhesive, and (iii) interfacial mechanical locking between the adhesive and the bonding substrate. This results in multiple regimes of strain hardening and strain softening, evidenced by multiple regions of steady-state creep, separated by strong transitions in the creep rates. This complex, multi-phase, nonlinear creep response cannot be described by conventional creep constitutive models commonly used for polymers in commercial finite element codes. Accordingly, based on the empirical uniaxial tensile creep response and the mechanisms behind it, a new mechanistic model was proposed. This is capable of quantitatively capturing the characteristic features of the multiphase creep response of single-layered PSA joints as a function of viscoelastic bulk properties and free energy of the PSA material, substrate surface roughness, and interfacial surface energy between the adhesive and substrate. This is the first paper to present the modeling approach for capturing unique multi-phase creep behavior of PSA joint under tensile loading.