Strain Dependence Research Articles

Optical properties of InI3: Density functional theory calculations and experimental results

The electronic and optical properties of InI3 have been investigated by both experimental and theoretical approaches. The First Principle electronic structure and optical properties were calculated by Density Functional Theory (DFT) formalism using Full Potential Linearized Augmented Plane Wave plus local orbitals (FP-LAPW + lo) implementing different appropriate exchange-correlation functionals in WIEN2k code. The calculations were also carried out implementing other functionals and only TB-mBJ results tally the closest with experimental results. The optical measurements of a well characterized InI3 films indicate the band gap as of direct type and residual strain dependant. The stress free intrinsic band gap Eg = 2.8 eV (average of Eg⊥c and EgIIc) has been determined from the residual strain dependence of the band gap in closest agreement with theoretically calculated value of 2.9 eV. Both theory and experiment show that the band gap is anisotropic along and perpendicular to c-axis. The electron effective mass me*=0.79m0 and the hole effective mass mh*=0.85m0 have been determined from the band structure. The experimental and theoretical optical properties match reasonably well.

Effects of strain and hydrostatic pressure on exciton properties in asymmetric zinc-blende (In,Ga)N/GaN coupled double quantum wells

Within the effective mass approximation, we studied the light-hole and heavy-hole exciton states and their optical properties, such as oscillator strength and radiative decay time, in asymmetric zinc-blende GaN/InxGa1−xN/GaN/InyGa1−yN/GaN coupled double quantum wells. The variational method was performed under strain and hydrostatic pressure. The light-hole and heavy-hole exciton binding energies as a function of the left-well width and/or right-well width, middle-barrier thickness, and indium concentration x(y) of (In,Ga)N material are analyzed in detail. The light-hole and heavy-hole exciton binding energies show an increasing trend with increase of hydrostatic pressure. The hydrostatic pressure not only results in an increase in exciton binding energy, interband transition energy, and oscillator strength but also a decrease in the emission wavelength and radiative decay time. In addition, the biaxial strain dependence of the emission wavelength, radiative decay time, and interband transition energy of the exciton is very remarkable.

Antiferromagnetic chromium thin films as piezoresistive sensor materials

Sputter-deposited thin films of pure chromium and of chromium with small amounts of nitrogen are characterized regarding their electrical resistivity and strain dependence, i.e., piezoresistivity. They show a temperature dependent piezoresistive effect with gauge factors ranging approximately from 10 to 20. Related to this effect, they exhibit signs of a paramagnetic–antiferromagnetic transition at temperatures of 420 K and higher. For characterization, resistivity is measured at different strain levels: in a bending setup with a fixed radius and in a four-point bending system with reference strain gauges. Several parameter series of the sputter deposition of pure Cr films show that the higher gauge factor is correlated to a higher temperature coefficient of resistivity (TCR). The addition of nitrogen extends the range of TCR toward negative values, with gauge factors still in the same range as pure Cr. A Cr–N strain gauge is characterized and shows a linear, low-hysteresis strain–resistivity effect as well as a relatively large transverse sensitivity. Resistivity and gauge factor of one Cr and one Cr–N sample are measured from room temperature up to 600 K. These films have a resistivity anomaly indicating an antiferromagnetic ordering temperature TN that is much higher than in bulk Cr. The gauge factor has a maximum near TN and falls to small values at higher temperatures. The results indicate that the piezoresistivity of Cr and Cr-rich films is coupled to their spin-density wave (SDW) antiferromagnetism. Since the SDW state is known to be tunable through alloying, internal stress, and crystallinity, it appears that piezoresistivity can be influenced by these parameters as well.

Stiffness contributions of ballast in the context of dynamic analysis of short span railway bridges

Railway bridges are subjected to intensive dynamic loading. In structural calculations, the resulting response is estimated by dynamic calculations. As the basis of these calculations, the system's natural frequencies are to be numerically determined. Various studies have shown that a discrepancy between these measured natural frequencies and the numerical determination often occurs for short-frame bridges. In common practice, the ballast is assumed to be non-contributing to the global structural stiffness. In some cases, rheological models are developed to consider possible ballast stiffnesses based on small-scale model tests. The resulting spring-damper models are based on empirical values and are not directly related to the material behaviour of ballast.This paper discusses the ballast stiffness at the material level using relationships known from soil dynamics. The research shows that the material properties of the ballast can be determined in terms of stress and shear strain dependence. An equivalent ballast stiffness can be determined and considered in dynamic calculations for a known stress state and corresponding superstructure accelerations. The paper presents an approach for determining vertical and horizontal ballast stiffness according to shear strains and superstructure accelerations.This developed approach is validated by experimental tests using a small-scale bending beam and accompanying numerical calculations.Furthermore, a parameter study shows that the stiffness of the ballast does not contribute significantly to the global bending stiffness. Thus, the first bending natural frequency is hardly influenced by the ballast track.

Atomistically-informed continuum modeling and isogeometric analysis of 2D materials over holey substrates

This work develops, discretizes, and validates a continuum model of a molybdenum disulfide (MoS2) monolayer interacting with a periodic holey silicon nitride (Si3N4) substrate via van der Waals (vdW) forces. The MoS2 layer is modeled as a geometrically nonlinear Kirchhoff–Love shell, and vdW forces are modeled by a Lennard-Jones (LJ) potential, simplified using approximations for a smooth substrate topography. Both the shell model and LJ interactions include novel extensions informed by close comparison with fully-atomistic calculations. The material parameters of the shell model are calibrated by comparing small-strain tensile and bending tests with atomistic simulations. This model is efficiently discretized using isogeometric analysis (IGA) for the shell structure and a pseudo-time continuation method for energy minimization. The IGA shell model is validated against fully-atomistic calculations for several benchmark problems with different substrate geometries. Agreement with atomistic results depends on geometric nonlinearity in some cases, but a simple isotropic St.Venant–Kirchhoff model is found to be sufficient to represent material behavior. We find that the IGA discretization of the continuum model has a much lower computational cost than atomistic simulations, and expect that it will enable efficient design space exploration in strain engineering applications. This is demonstrated by studying the dependence of strain and curvature in MoS2 over a holey substrate as a function of the hole spacing on scales inaccessible to atomistic calculations. The results show an unexpected qualitative change in the deformation pattern below a critical hole separation.

Analysis of Active and Passive Deformation of Expanded Polystyrene Foam under Short-Term Compression

In this paper, we undertake a detailed analysis of the active and passive deformation of expanded polystyrene (EPS), which is used as a thermal insulating layer in building partitions, under short-term compressive loading. The values of residual strain in 10-40 kg/m3 density EPS after monotonically increasing loading under active deformations of 20%, 30%, 40%, 50%, and 60% with the following complete removal are determined. These values are a physical sign of the elastic-plastic state of EPS. It has been shown that the final destruction of cells takes place in EPS when the active strain reaches 50%. Empirical equations are proposed to estimate the residual strain of EPS based on density with determination coefficients varying from 0.744 to 0.986 at a confidence level of 90%. Moreover, graphical interpretations with regression equations for residual strain dependence on density and compressive strength, as well as density and active strain, were proposed with determination coefficients equal to 0.779 and 0.717, respectively.

Uncovering cross-bridge properties that underlie the cardiac active complex modulus using model linearisation techniques

The properties underlying cardiac cross-bridge kinetics can be characterised by a muscle’s active complex modulus. While the complex modulus can be described by a series of linear transfer functions, the biophysical mechanisms underlying these components are represented inconsistently among existing cross-bridge models. To address this, we examined the properties commonly implemented in cross-bridge models using model linearisation techniques and assessed their contributions to the complex modulus. From this analysis, we developed a biophysical model of cross-bridge kinetics that captures the three components of the active complex modulus: (1) the elastic modulus at low frequencies that arises from allowing the proportion of cross-bridges in the post-power stroke state to increase with sarcomere length, (2) the increase in elastic modulus at high frequencies that arises from the dependence of cross-bridge strain on sarcomere velocity, and (3) the negative viscous modulus which signifies the production of work by cross-bridges arises from either a sarcomere length or strain dependence, or both, on the rate of change of cross-bridge proportion in the post-power stroke state. While a model that includes all these features can theoretically reproduce the cardiac complex modulus, analysis of their transfer functions reveals that the relative contributions of these components are often not taken into account. As a result, the negative viscous component that signifies work production is not visible because the complex modulus is dominated by the effects of sarcomere velocity on cross-bridge strain.

(Digital Presentation) Fabrication of Microbridges Based on Ge-on-SOI and Observation of Strong Resonant Light Emission

Introduction Ge is one of the most attractive material for silicon-based optoelectronics because it can be epitaxially grown on a Si substrate, allowing us to integrate Ge based light emitters and photodetectors monolithically on the Si platform. Although Ge is an indirect band gap semiconductor like Si, by epitaxially growing Ge on the Si substrate, tensile strain is introduced into Ge, resultantly leading to the Γ-valley shifts and increase in the light emission efficiency via the direct transition. The amount of the strain induced in Ge-on-Si, however, is not sufficiently large, demanding other methods of applying large tensile strain to Ge. Fabrication of Ge microbridge structure is expected to induce the larger strain and further improve light emission efficiency [1]. In general, microbridges reported so far have been fabricated by the electron beam lithography process, which is not appropriate for mass production. In this study, we fabricate Ge microbridge by simple photolithography process based on Ge-on-Si and Ge-on-SOI structures and very strong room temperature photoluminescence is obtained and strong resonant peaks can be observed. Experimental Method Ge layers were grown on a Si (110) wafer (Ge-on-Si) or a SOI (100) wafer (Ge-on-SOI) using a two-step growth method by solid source MBE. Firstly, a 40nm thick buffer layer at a low temperature of 350 ~ 400℃. Secondly, a 500 nm thick Ge layer was grown at a high temperature of 550 ~ 650℃. Post-growth-annealing was carried out at 800℃ for 10 minutes. The microbridge structures were defined by the standard photolithography process and mesa etching was performed by the reactive ion etching. Subsequently, the Si under the bridge and pads was selectively removed by KOH etchant, leading to free-standing Ge microbridge. For the Ge-on-SOI, the underlying SiO2 layer (buried oxide) was additionally removed by HF. Results and Discussion It was observed by SEM measurements that the Ge microbridges fabricated from Ge-on-Si were slightly warped from both ends to the center of the bridges. Hydrogen gases generated due to the reaction of Si and KOH during the selective etching are considered to be responsible for the warping of the microbridges, which makes it difficult to control the strain of the Ge. The selective etching time, therefore, has to be minimized to reduce the effects of the gas generation. For this purpose, the microbridges were fabricated from Ge-on-SOI, where the floating structure can be easily formed by the etching of the buried SiO2 layer with HF and the etching time of Si with KOH was reduced by a factor of four. As a result, the warping was completely suppressed and very flat microbridges were fabricated without any warping.Photoluminescence measurements at the center of the microbridge on Ge-on-SOI were performed at room temperature. Strong PL emissions were obtained in the wavelength range of 1630-2000 nm, where several strong resonant peaks appear. This resonance is considered to occur due to reflection at the side wall of the bridge and the peaks can be well fitted with the cavity length of the bridge width. Also, we carried out PL measurements from one end to another end of the bridge, and investigated the bridge position dependence of the PL emission. It was found that the light emission intensity increased toward the center of the bridge, and the highest intensity was obtained at the center. Moreover, the strain amounts were measured by micro Raman line scan along the bridge and strain dependence of PL emission was investigated. It was also shown that the strain amount increased toward the center of the bridge and became the highest at it. It was demonstrated that the higher PL intensity can be obtained due to the higher tensile strain at the center of the microbridge. In summary, we fabricated Ge microbridge structures by photolithography process and obtained strong room temperature resonant light emission from the Ge microbridges formed from Ge-on-SOI where bridge-warping was completely suppressed by shortening the etching time. From this result, we can say that the Ge microbridge light emitting devices are very promising for applications to the light sources on the Si platform.This work was partially supported by JSPS KAKENHI (Nos. 19H02175, 19H05616 and 20K21009).[1] M. J. Suess et al, Nat. Photonics 7: 466, 2013 Figure 1

Molecular dynamics study on the thermal conductivity of a single polyethylene chain: Strain dependence and potential models’ effect

The thermal conductivity of a single polymer chain, which is an important factor in the rational design of polymer-based thermal management materials, is strongly affected by the strain state of the chain. In the present study, using non-equilibrium molecular dynamics simulations, the thermal conductivity of a single polyethylene chain, representing a typical polymer chain, was calculated as a function of strain. To investigate the effect of different modeling of covalent bonds, the results were compared for reactive and non-reactive potential models, the AIREBO and NERD potentials, respectively. When the strain ε was as small as ε < −0.03, i.e., under slight compression, the thermal conductivity values were similar regardless of the potential model and increased with increasing strain. However, the two potential models showed qualitatively different behaviors for larger strains up to ε < 0.15: the thermal conductivity calculated by the non-reactive potential continually grows with increasing strain, whereas that by the reactive potential model is saturated. The analysis of internal stress and vibrational density of states suggested that the saturation behavior is due to the weakening of the covalent bond force as the C–C bond elongates, and thus, the result of the reactive model is likely more realistic. However, for ε > 0.1, the reactive potential also produced unphysical results due to the effect of the switching function, describing the formation and breaking of covalent bonds. The present results indicate that careful selection of the potential model and deformation range is necessary when investigating the properties of polymers under tensile strain.

In-situ analysis of the elastic-plastic characteristics of high strength dual-phase steel

Modeling the elastic behavior of dual-phase steels is complex due to the strain dependency of Young's modulus and high elastic nonlinearity. Since it is assumed that reasons for this are to be found in microstructural behavior, microscopic in-situ analysis are necessary, but due to the overlap of the martensite and ferrite peaks, the evaluation of diffraction profiles is highly complex. Within this work, CR590Y980T (DP1000) is investigated in a continuous cyclic tensile and tension-compression test under synchrotron radiation at High Energy Material Science beamline P07 in Petra III, DESY. On basis of additional EBSD measurements, an evaluation approach is shown to analyze the dual-phase diffraction profiles in such a way that martensite and ferrite can be separated for three lattice planes. The origin of the specific elastic-plastic behavior of dual-phase steels in terms of onset of yielding, anelasticity or early re-yielding is analyzed on the basis of lattice strains and interphase stresses. For this, the time-synchronously measured micro data is correlated with the macro stress-strain relationship and thermoelastic effect. The results help to better understand strain-dependent elastic-plastic behavior of DP steels on a micro level and provide great potential to improve characterization and modeling in terms of springback prediction.

Anomalous behavior of strain modulated lattice thermal transport in piezoelectric crystals and the effect of polarization

Strain is known to influence the lattice dynamics of crystalline solids. Its effect is generally expressed in a decrease of the lattice thermal conductivity as the stress is varied from compression to tension. However, the results of our ab initio calculations suggest that under a uniaxial strain along the c-axis, the lattice thermal conductivity of PbTiO3, a typical piezoelectric material, actually increases from compression to tension going through a maximum at the unstrained state. We find that both tensile and compressive strains reduce considerably the phonon mean free path. Strain also modifies remarkably the phonon group velocity and lifetime of the low-frequency acoustic modes. This unusual strain dependence largely comes from a competing effect of the electrical polarization and the elastic stiffness on the phonon velocity due to their opposite strain dependence. Based on these results, we predict an unexpected thermal transport behavior due to the piezoelectric effect and reveal the significant role of the electrical polarization in lattice thermal transport. This work may thus inspire the development of polarization engineering as a new avenue towards manipulation of heat conduction bringing to the light the previously unrecognized potential of piezoelectric materials for thermal modulation applications.

Divergence of phonon angular momentum driven by temperature and strain

Phonon angular momentum (PAM) may exhibit exotic temperature dependence as it is sensitive to the phonon lifetime. Constant phonon-lifetime approximation fails to depict such behavior. Here, we study the PAM of AlN, GaN, and graphenelike boron nitride (g-BN) monolayer with full consideration of phonon lifetime using first-principles calculations. We show that wurtzite AlN and GaN acquire divergent PAM at low temperatures from their lowest-lying phonon branches. The g-BN monolayer, on the other hand, does not have finite PAM at equilibrium structure. Rather, it shows intriguing strain dependence on PAM; the compressive strain greater than the critical size generates divergent PAM at low temperatures due to the divergent lifetime of TA phonons. As PAM couples with rotational excitations in solids associated with charge, spin, or electromagnetic fields, our study demonstrates a possibility of mechanical and thermal engineering of such excitations.

Magnetic Response Detects the Strength of Carrageenan Network.

The effect of carrageenan concentration on the magneto-rheological effect of magnetic gels with a magnetic particle concentration of 50 wt.% was investigated under a magnetic field of 50 mT by dynamic viscoelastic measurements. The change in the storage modulus for magnetic gels due to the magnetic field was 3.0 × 103 Pa at a carrageenan concentration of 1.0 wt.% and increased with the concentration. The modulus change showed a maximum of 2.3 × 104 Pa at ~2.0 wt.% and became lower at higher concentrations. This is an interesting phenomenon, which was first observed in this study. The critical strain, the strain where the storage modulus intersects the loss modulus in the strain dependence of the modulus, was much higher than that for carrageenan gels, indicating a strong interaction between the magnetic particles and carrageenan. At 0 mT, the critical strain for the magnetic gels increased remarkably with decreasing the concentration, indicating that magnetic gels have a structure that does not flow easily at concentrations below 1.75 wt.%. It is considered that the structure hardly flows, hindering the movement of particles. At high concentrations, the SEM photographs showed both a particle network of magnetic particles and a dense carrageenan network. It can be considered that the movement of magnetic particles was hindered due to these factors at high concentrations.

Electronic structure and thermoelectric properties of uniaxial strained SnSe from first-principles calculations

SnSe is a promising candidate of thermoelectric material for its high ZT value. To further optimize its thermoelectric performance, we systematically investigate the uniaxial strain dependence of electronic structure and thermoelectric properties for both p- and n-type SnSe based on first-principles calculations and Boltzmann transport equation. The band gap of SnSe can be significantly tuned by the uniaxial strain along b-axis. The momentum alignment and energy convergence of band structure induced by uniaxial strains are observed. The Seebeck coefficient, electrical conductivity and power factor can be significantly improved by applying suitable uniaxial strains. In particular, for p-type SnSe at 300 K, the peak value of PFxx/τ for εa = −6% is 7.6 times as large as that of unstrained SnSe. The peak values of PFxx/τ, PFyy/τ and PFzz/τ in p-type SnSe at 300 K under εb = −6% are 2.6, 2.0 and 2.3 times as large as those of unstrained SnSe, respectively. At 750 K, the peak value of PFzz/τ increases by 96.9% under εc = −6% in p-type SnSe and the peak value of PFyy/τ increases by 73.2% under εb = 6% in n-type SnSe. Our findings indicate that uniaxial strain can be an efficient strategy to modulate the thermoelectric properties of SnSe and provide a helpful perspective for its practical applications.

Evolution of electronic and magnetic properties of Sr2IrO4 under strain

Motivated by properties-controlling potential of the strain, we investigate strain dependence of structure, electronic, and magnetic properties of Sr2IrO4 using complementary theoretical tools: ab-initio calculations, analytical approaches (rigid octahedra picture, Slater-Koster integrals), and extended t-{{{mathcal{J}}}} model. We find that strain affects both Ir-Ir distance and Ir-O-Ir angle, and the rigid octahedra picture is not relevant. Second, we find fundamentally different behavior for compressive and tensile strain. One remarkable feature is the formation of two subsets of bond- and orbital-dependent carriers, a compass-like model, under compression. This originates from the strain-induced renormalization of the Ir-O-Ir superexchange and O on-site energy. We also show that under compressive (tensile) strain, Fermi surface becomes highly dispersive (relatively flat). Already at a tensile strain of 1.5%, we observe spectral weight redistribution, with the low-energy band acquiring almost purely singlet character. These results can be directly compared with future experiments.

Analysis of the evolution of the Lankford coefficient in uniaxial tensile tests and validation with grain structure analysis

Modern materials mostly exhibit a low formability or a complex material behavior. For example, the common mild steel DC06 exhibits a strain state dependency in the yield stress and a strain dependency of the Lankford coefficients. Thus it is necessary to characterize the material properties from the onset of plastic deformation up to fracture. For example in the uniaxial tensile test, the flow stress and the r-values can be determined. According to the standards, the characterization is only applicable up to uniform elongation. In the case of DC06, the uniform elongation is with 24% comparatively low in contrast to the ultimate elongation with 60%. Research has proven, that the true stress can be characterized up to high strain in the uniaxial tensile test. For the strain dependent Lankford coefficient, this validation is missing. The aim in this investigation is the analysis of the strain dependent anisotropy up to high strain levels in uniaxial tensile tests and the validation. This is done with a comparison of optically measured r-values with the grain structure evolution of the pre stretched parts. These results prove the applicability of the standardized evaluation of Lankford coefficients out of DIC data above the uniform elongation.

A stochastic study of the deformation and failure strain of Au bi-crystalline nanowires with a longitudinal twin boundary

Molecular dynamics (MD) simulations have been performed to understand the deformation mechanisms and ductility (failure strain) dependence on nanowire cross-sectional size for Au bi-crystalline nanowires with a longitudinal twin boundary (LTB). Different cross-sectional aspect ratios and volume ratios of grain sizes have been constructed in the MD simulations and tensile loaded. The simulation results indicate that all nanowires exhibit a similar elastic regime till peak yield stress and yielding occurs through nucleation of 1/6<112> Shockley partial dislocations from nanowire edges. Once interacting with the LTB, there are different paths of plasticity, mainly leading to two types of mechanisms: detwinning of the LTB with reorientation of the crystal and dislocation slip. For a given shape of nanowire, we found that the competition between these two operating mechanisms is stochastic and results in a distribution of detwinned volume fractions and strain to failures. Based on the simulation results we found that the average extent of detwinning is in correlation with the volume ratio of the grains. Also, it is in a linear correlation with the average strain to failure, which suggests that the LTB affects the ductility of the nanowire. We concluded from the results that the more symmetric are the grains that composes the nanowires, the smaller is the ductility.

On the origin of elasticity and heat conduction anisotropy of liquid crystal elastomers at gigahertz frequencies

Liquid crystal elastomers that offer exceptional load-deformation response at low frequencies often require consideration of the mechanical anisotropy only along the two symmetry directions. However, emerging applications operating at high frequencies require all five true elastic constants. Here, we utilize Brillouin light spectroscopy to obtain the engineering moduli and probe the strain dependence of the elasticity anisotropy at gigahertz frequencies. The Young’s modulus anisotropy, E||/E⊥~2.6, is unexpectedly lower than that measured by tensile testing, suggesting disparity between the local mesogenic orientation and the larger scale orientation of the network strands. Unprecedented is the robustness of E||/E⊥ to uniaxial load that it does not comply with continuously transformable director orientation observed in the tensile testing. Likewise, the heat conductivity is directional, κ||/κ⊥~3.0 with κ⊥ = 0.16 Wm−1K−1. Conceptually, this work reveals the different length scales involved in the thermoelastic anisotropy and provides insights for programming liquid crystal elastomers on-demand for high-frequency applications.

A Simple Calibrated Ductile Fracture Model and Its Application in Failure Analysis of Steel Connections

A new fracture model is developed to predict the ductile fracture of structural steel under multiaxial stress states. First, the Lee–Mear void growth theory is used to establish the quantitative relationship between the stress triaxiality and material’s ductility. A stress triaxiality dependence function, which accounts for the material’s strain hardening, is derived from modifying the dilatation rate of a spherical void in a typical unit cell. Subsequently, the Tresca failure model is used in conjunction with the Swift hardening law to establish a Lode dependence of fracture strain. Then, the theoretical formula of the new fracture model is obtained by combining both stress triaxiality and Lode angle dependence functions. The proposed fracture model has a unique advantage: i.e., this model has only two material parameters. These two parameters can be easily calibrated through a simple standard coupon test, which significantly reduces the difficulty of model calibration work and facilitates its application in practical engineering. In order to verify the new fracture model, the test results of five types of Q460 steel specimens were used to calibrate the model parameters. The prediction accuracy of the new model is then checked by calculating the average error between the test results and the predicted fracture strain envelope. Finally, the new fracture model was applied in the numerical analysis of two types of steel connections. The validation of the proposed fracture model is verified by comparing the load–displacement curve and failure modes of the steel connections obtained from both test and numerical analysis.

Revisiting Frictional Characteristics of Graphene: Effect of In-Plane Straining

Supreme mechanical performance and tribological properties render graphene a promising candidate as a surface friction modifier. Recently, it has been demonstrated that applying in-plane strain can effectively tune friction of suspended graphene in a reversible manner. However, since graphene is deposited on solid surfaces in most tribological applications, whether such operation will result in a similar modulation effect becomes a critical question to be answered. Herein, by depositing graphene onto a stretchable substrate, the frictional characteristics of supported graphene under a wide range of strain are examined with an in situ tensile loading platform. The experimental results show that friction of supported graphene decreases with increasing graphene strain, similar to the suspended system. However, depending on the adherence state of the graphene/substrate interface, the system exhibits two distinct friction regimes with significantly different strain dependences. Assisted by detailed atomic force microscopy imaging, we attribute the unique behavior to the transition between two friction modulation modes, i.e., contact-quality-dominated friction and puckering-dominated friction. This work provides a more comprehensive view of the influence of strain on surface friction of graphene, which is beneficial for active modulation of graphene friction through strain engineering.