Compressive Normal Stress Research Articles

2D finite-element elastic models of transtensional pull-apart basins

A set of two-dimensional finite-element elastic models are presented to provide insights on the evolution of transtensional pull-apart basins between two right-stepping, right-lateral fault segments. Three representative fault segment interaction geometries are modelled, showing underlapping, neutral and overlapping segments. Despite the simplifications of the 2D model, overall results are obtained that might help understanding the formation of pull-apart basins. Firstly, the orientations of the local σ1 and σ3 tensional stress directions markedly depend on the segment's position. Secondly, the mean normal stress is extensional in a transtensional basin between segments, while the region outside the step is characterized by more compressive mean normal stresses. Thirdly, the angle of offset between the fault segments is one of the most important parameters controlling the geometries of the transtensional pull-apart basins: connected depocenters with basin high and lozenge shape in the case of underlapping steps, spindle shape or lazy S or Z shape in the case of neutral steps, and broadly elongate rhomboidal to sigmoidal basins in the case of overlapping steps. Generally, en-échelon basin margin system, dual opposing asymmetric depocenter, intrabasin relative structural high, and wide basin width can be used as indicators that a pull-apart basin is developing in transtension zones.

Model of heterogeneous reinforced fiber foam concrete in bending

The paper considers a model of heterogeneous reinforced fiber foam concrete, given the bimodule in the elastic formulation. Based on the proposed model the analysis of stress-strain state of an I-beam of reinforced fiber foam concrete, arbitrarily supported and loaded arbitrarily. The dependence of maximum stress on the number of rods and their location in the compressed and stretched zones. The neutral line does not coincide with the main central axis in the bimodule materials, then the values of the maximum normal stresses also vary depending on the elastic moduli relations for tension and compression. This allows us to reasonably regulate the structural features of beams when the properties of fibrous concrete are taking into account. The value of the maximum normal stresses is compared with and without the bimodule material of the beam, from which it follows that the design load capacity of the beam increases with the bimodulity of the material taken into account. The magnitude of the maximum normal stresses in reinforced beams made of concrete of a cohesive structure with allowance for bimodulity was numerically investigated. It has been established that the normal tensile stress arising in a fiber-reinforced concrete beam is higher than in a beam of concrete of a fused structure by 42%. The value of the normal compressive stress is lower by an average of 38%.

Detailed micro-modelling of the direct shear tests of brick masonry specimens: The role of dilatancy

The mechanical parameters (shear strength of bed joints) derived from triplet tests can apparently be significantly different from those obtained through the so called “shove test” procedure executed on the same type of masonry. It was observed that this discrepancy may be caused by a wrong estimation of the compressive stress in the bed joints of the shove test. This article describes a numerical technique implemented in Abaqus to provide a sound interpretation of the phenomena involved in the failure of a mortar bed joint. The level of accuracy required to accomplish the objectives of the present study has driven the attention toward the detailed micro-modelling approach. Units and mortar joints have been modelled with continuum elements whereas the cohesive interfaces with zero thickness have been used for the unit-mortar interfaces. The material nonlinearities of masonry have been attributed to mortar and unit-mortar interfaces. The dilatancy of the bed joint during the shear failure process can generate, under certain boundary conditions, a local increase of the normal compression stress. Hence, particular attention has been dedicated to the modelling of this phenomenon. Several triplet tests and shove tests have been used as experimental benchmark for the numerical simulations. With the aim to accurately calibrate the parameter that controls the dilatancy, this work has paid attention also to the numerical-experimental comparison in terms of normal expansion of the joints, whereas commonly the comparison is generally carried out only in terms of shear stress-displacement curve. With the proposed technique, the triplet test and the shove test can be simulated with great accuracy. Thanks to these features, it has been also possible to relate the two types of test by highlighting the factors that affect the local normal stress during the shear failure process, providing a more detailed explanation of why and how the shove test results must be carefully interpreted in order to derive a realistic estimate of the shear strength of bed joints.

Sensing the stress in steel by capacitance measurement

This paper provides the first report of the sensing of stress in a metal (namely steel and stainless steel) by capacitance measurement. The method involves the measurement of the in-plane capacitance (2 kHz) between two coplanar electrodes that are on the same surface of the specimen. The capacitance decreases with increasing normal compressive stress. The fractional decrease in capacitance (up to 20%) is higher than the compressive strain calculated based on the elastic modulus by orders of magnitude. The capacitance decrease is essentially reversible and is attributed to the direct piezoelectric effect. Because an LCR meter is not designed to measure the capacitance of an electrical conductor, it is essential for a dielectric film to be positioned between the electrode and specimen. Two configurations are used for the electrodes. Configuration I involves aluminum foil as the electrode and a stack of 3 layers of double-sided adhesive tape as the dielectric film; no pressure is used. Configuration II involves copper sheet as the electrode and a glass fiber polymer-matrix composite film as the dielectric film, with normal pressure applied to the stack. The fractional decrease in capacitance per unit stress is much greater for configuration I than configuration II. Configuration I is better for sensing low stresses, whereas configuration II is better for sensing high stresses. Configuration I is less expensive and more practical than configuration II.

Plastic strain recovery in nanocrystalline copper thin films

Plastic strain recovery is a distinctive behavior of nanocrystalline thin film metals whereby plastic strain induced via application of an external load is gradually recovered over a time period of hours to days after load removal. Previous studies to model plastic strain recovery assumed that grain boundary sliding or grain boundary diffusion with heterogeneous diffusivity was the dominant deformation mechanism. In this study we propose that grain boundary diffusion in the presence of nanoscopic voids can lead to plastic strain recover without having to assume a sliding or heterogeneous diffusivity on grain boundaries. To model the system numerically in the context of the finite element method, we include a diffusion zone (DZ) and a cohesive zone (CS) on the grain boundaries and also include the possibility of plastic deformation in the surrounding grains. Our results suggest that diffusion leads to a mass flux toward the “void tips” (i.e. intersections of the voids and grain boundaries) as the external load is applied. Upon removal of the load, the additional material that accumulated near the void tips introduces a compressive residual normal stress on the grain boundary. The gradient of grain boundary residual stress leads to diffusion flux away from the void tip along the grain boundary in addition to diffusion flux to the void surface from the grain boundary. This redistribution of mass leads to a reduction in specimen length that is interpreted in terms of plastic strain recovery. With time the diffusion flux reduces the grain boundary stress gradient to the point where further grain boundary diffusion flux becomes negligible, after which diffusion flux occurs predominantly from the grain boundary at the void tip to the void surface. Since only one mass flux route remains active, the predicted plastic strain recovery rate is smaller. These simulation results are consistent with our experimental results that indicate plastic strain recovery exhibits two characteristic rates: a “fast” strain rate of about [10−7]s−1 followed by transition to a “slow” strain rate of about [10−9]s−1.

Discussion on the installation checking method of precast composite floor slab with lattice girders

Based on the installation checking requirements of China’s current standards and the international norms for prefabricated structural precast components, it proposed an installation checking method for precast composite floor slab with lattice girders. By taking an equivalent composite beam consisted of a single lattice girder and the precast concrete slab as the checking object, compression instability stress of upper chords and yield stress of slab distribution reinforcement at the maximum positive moment, tensile yield stress of upper chords, slab normal section normal compression stress and shear instability stress of diagonal bars at the maximum negative moment were checked. And the bending stress and deflection of support beams, strength and compression stability bearing capacity of the vertical support, shear bearing capacity of the bolt and compression bearing capacity of steel tube wall at the bolt were checked at the same time. Every different checking object was given a specific load value and load combination. Application of installation checking method was given and testified by example.

The parameters effect on the structural performance of damaged steel box beam using Taguchi method

In the current study, the influence of notch or opening parameters and the positions of the applied load on the structural performance of steel box beams up to failure was investigated using Finite Element analysis program, ANSYS. The Taguchi-based design of experiments technique was used to plan the current study. The plan included 12 box steel beams; three intact beams, and nine damaged beams (with opening) in the beams web. The numerical studies were conducted under varying the spacing between the two concentrated point loads (location of applied loads), the notch (opening) position, and the ratio between depth and width of the notch with a constant notch area. According to Taguchi analysis, factor X (location of the applied loads) was found the highest contributing parameters for the variation of the ultimate load, vertical deformation, shear stresses, and the compressive normal stresses.

Large deformation electrohydrodynamics of a Skalak elastic capsule in AC electric field.

The axisymmetric electrohydrodynamic deformation of an elastic capsule with a capacitive membrane obeying the Skalak law under a uniform AC electric field is investigated using analytical and boundary integral theory. The low capillary number (the ratio of destabilizing shear or electric force to the stabilizing elastic force) regime shows that time-averaged prolate and oblate spheroid deformations, and the time-periodic prolate-sphere, oblate-sphere breathing modes are commensurate with the time averaged-deformation. A novel prolate-oblate breathing mode is observed due to an interplay of finite membrane charging time and the field reversal of the AC field. The study, when extended to high capillary numbers, shows new breathing modes of cylinder-prolate, cylinder-oblate, and biconcave-prolate deformation. These are the results of highly compressive normal Maxwell stress at the poles and are aided by a weak compressive equatorial stress, characteristic of a capacitive membrane. The findings of this work should form the basis for the understanding of more complex biological cells and synthetic capsules for industrial applications.

Finite-element analysis of the tool tilt angle effect on the formation of friction stir welds

The tool tilt angle is one of the key process parameters determining the weld quality during friction stir welding. However, the influence of tilt angle on the weld formation has not been fully understood. Hence, in this paper, a three-dimensional thermal-mechanical coupled finite element model is established, in which the tilt angle is considered in the geometric model. This model is shown to be able to predict the in-process thermal-mechanical state variables (e.g. temperature, flow path and stress) during the welding and the post-welding morphology of the weld. The predicted temperature distribution and weld morphology agree well with the corresponding experimental results. It is shown by the simulation results that wormhole defects appear in the weld with a zero tilt angle, while no such defects are observed in the case that the tilt angle of 2° is employed. In order to get a deeper understanding of the weld formation mechanism, the thermal-mechanical condition around the tool during welding with/without tilt angle are compared and analysed. It is found from our simulation that both the peak temperature and compressive normal stress on material in the rear side of the tool are elevated by including a tilt angle of 2°. This temperature increase induced by the tilt angle will significantly soften the workpiece, meanwhile higher frictional driving force in the rear side will be generated by the increased compressive force. Therefore, the material flow in the rear side of the tool with the title angle is significantly enhanced, which contributes to avoid the generation of wormhole defect on the advancing side.

A Puck-based localisation plane theory for rate- and pressure-dependent constitutive modelling of unidirectional fibre-reinforced polymers

A new constitutive model is presented that aims to accurately tackle the effects of multiaxial loading, strain rate and hydrostatic pressure on unidirectional FRPs, while doing so in an intuitive and physically-based manner. In this model, it is assumed that yielding occurs primarily due to shear stresses acting on a critical localisation plane while normal compressive stresses on this plane have a strengthening effect similar to pressure effects in a Drucker-Prager model. In this way, the orientation of the localisation plane, which depends on the stress state of the material, deals with the issue of multiaxiality and the pressure-dependency is accounted for by the Drucker-Prager based yield criterion.The main appeal of this approach is that a complex three-dimensional problem is reduced to essentially a case of 2D plasticity, which is conceptually very simple and easier to interpret. In addition, this model is supported by a strong physical basis, as it is constructed from the well-established Mohr-Coulomb and Drucker-Prager theories.A series of experimental results are provided that support the hypotheses on which this theory is based and against which the model has been benchmarked, showing its ability to reproduce the complex observed effects of multi-axial loading, strain-rate and pressure.

Laminated element analysis to predict the shear strength of concrete beams under distributed and concentrated loads

In the present study, an advanced analytical method was developed to evaluate the shear strength of slender concrete beams under distributed and concentrated transverse loads. The concrete shear capacity of the concrete beams is mainly provided by the compression zone of intact concrete since the tension zone of the concrete beams is severely damaged by flexural cracks before shear failure. The concrete shear capacity is evaluated based on concrete material failure criteria addressing combined compressive normal and shear stresses in the compression zone along the critical shear crack surface. For complete analysis, laminated elements are applied to take into account the stress variation in each location of the compression zone. The proposed analytical method can be used not only to predict the shear strength, but also the location and the angle of the critical shear crack. The shear strength is predicted using the proposed method, and the results are compared to those of an experiment, covering a wide range of design parameters. In addition, analytical studies were performed for analytical beam models subjected to distributed and concentrated loads. Based on the analysis results, the effect of various parameters including the loading type (distributed and concentrated transverse loads) on the shear strength and the critical shear crack was investigated.

Nanomechanical characterization and fracture toughness of FeB and Fe2B iron borides produced by gas boriding of Armco iron

FeB and Fe2B hard ceramic phases were produced in Armco iron using gas-boriding in N2–H2–BCl3 atmosphere. This process was carried out at 920°C (1193K) for 3h and caused acceleration in the diffusion of boron into the surface of a base material in comparison with other acceptable methods of diffusion boriding. FeB and Fe2B layers were characterized by a strong zonation, obtaining the average thickness of 32μm and 125μm, respectively. Young's moduli and hardness of iron borides were measured using the nanoindenter with a Berkovich diamond tip under load of 50mN. The higher average indentation hardness (HIT=20.95±0.93GPa) and Young's modulus (EIT=308.86±26.44GPa) were characteristic of FeB phase. Fe2B boride was characterized by HIT=17.42±0.80GPa, and EIT=252.96±15.57GPa. The fracture toughness of iron borides was measured by microindentation technique using a Vickers diamond indenter under load of 100gf (about 0.981N). The average fracture toughness (Kc), measured in FeB zone, was equal to 1.79±0.70MPa·m1/2. Fe2B phase was characterized by higher fracture toughness, obtaining Kc=2.42±0.66MPa·m1/2. However, at FeB/Fe2B interface the increase in brittleness was detected. Such a situation was caused by the differences in coefficients of thermal expansion of both iron borides and their mechanical properties. It could provide the preliminary cracks at this interface after cooling. During indentation, the value of shear stress probably exceeded the value of normal compressive stress. It could cause the failure at this interface, facilitating cracks' propagation.

The Role of Geological Barriers in Achieving Robust Well Integrity

Wells play a key role in the reduction of greenhouse gas emissions. They are not only a critical element in ensuring the permanent trapping of carbon dioxide (CO2) in deep subsurface permeable formations, but they are also being recognized as an important source of natural gas emissions.The goal of well integrity is to minimize fluid migration from permeable formations through the use of barriers. Traditionally natural and man-made barriers have been regarded as separate and independent components: once the original impermeable layers such as shale or halite have been pierced by drilling, isolation must be restored by installing steel pipe and annular cement.However this picture has been blurred by the growing recognition that a particular class of rocks can prevent and control fluid leaks through a well's life, including the hundreds of years after abandonment. Creeping formations such as halides, mudstones and possibly ice can seal uncemented sections and large defects in the cement sheath. More importantly, the radial stress they exert reduces debonding and restores integrity once the cause of a microannulus has been eliminated; this makes the geological barriers self-healing, or robust.If creeping formations are to become a fundamental element in well design and evaluation, they need to be properly understood and modeled. From an engineering point of view, the identification and characterization of geological barriers should provide four sets of constitutive properties:•The ultimate radial stress exerted by the formation, as well as its anisotropy (i.e its variation around the casing circumference).•Mechanical properties of the formation to estimate leakage rates if the closure stress has been overcome and a microannulus is formed.•A time scale over which the creep deformation can seal a given defect, or an uncemented section of the annulus.•The type and extent of geochemical reactions, if any, between the formation and the leaking fluid.This paper reviews the limited available evidence on the role and characteristic of geological barriers and adds new examples that have arisen from the study of well integrity at the basin scale. A simple model captures the essential characteristics of the formations’ behavior and allows identifying the key parameters that control the beneficial aspect of formation creep on well integrity. For a cross-section at a given depth, we model the well system (casing/cement / formation and the potential defects at the interfaces) under plane-strain condition. Modeling formation creep using viscoelasticity, we obtain the time of closure of a given set of defects between the formation and the steel casing. In the absence of defects, or when the defects have already been closed, we also obtain the time evolution of the radial stress clamping the interface. The intensity of such a normal compressive stress clamping the interfaces is the key parameter controlling the occurrence of micro-annulus induced by subsequent fluid injection, such as CO2 injection, natural gas storage or reservoir stimulation.We use both an analytical approach in the simplest case of an isotropic far-field stress and a boundary integral equations method in the Laplace domain to handle more complex configurations. Our method is notably agnostic with respect to the viscoelastic constitutive law chosen to model the geological formation time-dependent behavior. We further discuss the impact of the choice of the type of constitutive law on the obtained results.Lastly, we discuss how the controlling parameters of the problem (in-situ stress, creep formation properties) can be measured or estimated from geophysical logs, geological and geomechanical information as well as active well tests. Our analysis aims at assessing the state of the art in the design and evaluation of geological barriers from a well integrity perspective. We also highlight the remaining questions to be answered by research.

The effect of temperature on the compressive strength of concrete

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Jetting of a shear banding fluid in rectangular ducts.

Non-Newtonian fluids are susceptible to flow instabilities such as shear banding, in which the fluid may exhibit a markedly discontinuous viscosity at a critical stress. Here we report the characteristics and causes of a jetting flow instability of shear banding wormlike micelle solutions in microfluidic channels with rectangular cross sections over an intermediate volumetric flow regime. Particle-tracking methods are used to measure the three-dimensional flow field in channels of differing aspect ratios, sizes, and wall materials. When jetting occurs, it is self-contained within a portion of the channel where the flow velocity is greater than the surroundings. We observe that the instability forms in channels with aspect ratio greater than 5, and that the location of the high-velocity jet appears to be sensitive to stress localizations. Jetting is not observed in a lower concentration solution without shear banding. Simulations using the Johnson-Segalman viscoelastic model show a qualitatively similar behavior to the experimental observations and indicate that compressive normal stresses in the cross-stream directions support the development of the jetting flow. Our results show that nonuniform flow of shear thinning fluids can develop across the wide dimension in rectangular microfluidic channels, with implications for microfluidic rheometry.

Microscopic Evaluation of a Damaged Press Casing and Analysis of Failure by Finite Element Method

The paper presents an instance of a failure of the casing of a press used to make hexagonal clamps on tubes used in power engineering. The failure occurred during the press operation. The results of microscopic investigations of the cracked area show that the crack was initiated by excessive accumulation of sulfide inclusions with an unfavourable banded structure that formed in the steel. An EDS analysis identified MnS involved in the crack mechanism.Moreover, an FEM simulation of the pressure distribution and an annulus model of axial loading were used to analyse the stress and strain values arising in the press casing under compression. It was found that normal compressive stresses in direction Z were much larger in the region where the crack occurred, which means that the press casing mechanical manufacturing process creates the largest stresses in the fillet radius area. On the other hand, the effect of sulphide inclusions in the material were also considered as a cause of failure.It is concluded that both these factors – equivalent stresses and the high level of sulphide inclusions in the steel structure have an impact on the press casing failure.

Direct Shear Tests of Sandstone Under Constant Normal Tensile Stress Condition Using a Simple Auxiliary Device

Tension–shear failure is a typical failure mode in the rock masses in unloading zones induced by excavation or river incision, etc., such as in excavation-disturbed zone of deep underground caverns and superficial rocks of high steep slopes. However, almost all the current shear failure criteria for rock are usually derived on the basis of compression–shear failure. This paper proposes a simple device for use with a servo-controlled compression–shear testing machine to conduct the tension–shear tests of cuboid rock specimens, to test the direct shear behavior of sandstone under different constant normal tensile stress conditions (σ = −1, −1.5, −2, −2.5 and −3 MPa) as well as the uniaxial tension behavior. Generally, the fracture surface roughness decreases and the proportion of comminution areas in fracture surface increases as the change of stress state from tension to tension–shear and to compression–shear. Stepped fracture is a primary fracture pattern in the tension–shear tests. The shear stiffness, shear deformation and normal deformation (except the normal deformation for σ = −1 MPa) decrease during shearing, while the total normal deformation containing the pre-shearing portion increases as the normal tensile stress level (|σ|) goes up. Shear strength is more sensitive to the normal tensile stress than to the normal compressive stress, and the power function failure criterion (or Mohr envelope form of Hoek–Brown criterion) is examined to be the optimal criterion for the tested sandstone in the full region of tested normal stress in this study.

Neotectonics and tectonic stresses of the Sakhalin Island

The paper describes the neotectonics of the Sakhalin Island and analyzes the latest and recent tectonic stresses in the study area in order to establish their differences in the Amur and Okhotsk microplates, which boundary is confined to the Tym-Poronaisk fault, the largest NS-striking fault in the Central Sakhalin (Fig. 1). Our map of the structural geomorphological features of the study area (Fig. 2) shows three longitudinal zones: the western and eastern uplifts, and the Central Sakhalin basin between the uplifts. In the Southern Sakhalin, neotectonic stresses were studied by a combination of tectonophysical methods and the method of structural geology (Figures 3 to 6, and Table). Our study shows that the regional axes of maximum and minimum compressive principal normal stresses are primarily of the subhorizontal orientations (Fig. 5, Д ) . In the Northern and Central Sakhalin, neotectonic stresses were reconstructed by the structural geomorphology method. The compression axes are oriented sublatitudinally, with the NE-trending strike in the Northern Sakhalin (Fig. 7, A ), and the extension axes are oriented submeridionally; in the Northern Sakhalin, respectively, they are oriented in the NW direction. The results of our study of neotectonic stresses were used to construct a map of recent geodynamics of Sakhalin (Fig. 7, Б ), which shows zones differing in the geodynamic settings of the most recent faulting. According to the analysis of the recent tectonic stress with respect to the earthquake focal mechanisms in the period from 1978 to 2015 (Fig. 8), recent stresses dominating in Sakhalin have mainly the sublatitudinal low-angle orientations of the deviatoric compression axis. The submeridional low-angle orientations of the deviatoric extension axes are observed in the Northern Sakhalin and partly in the north of the Southern Sakhalin (see Fig. 8). The high-angle axes of deviatoric extension are typical of the western and central parts of the Southern Sakhalin, and such extension leads to horizontal compression and reverse faulting. In some areas of the recent stress field, the deviatoric axes of compression and extension have unstable orientations. The latitudinal boundaries of such areas are nearly coincident with the boundaries of the zones that differ in the geodynamic settings of the most recent faulting, which means that these areas and zones are reliably identified. The relative inhomogeneity of the neotectonic and recent stress fields in the Southern Sakhalin does not give grounds to distinguish differences in the state of crustal stresses in the areas located on the sides of the Southern Sakhalin fault. As a consequence, a boundary between the Amur and the Okhotsk Plate in the South Sakhalin cannot be drawn along this fault. It is most likely that this boundary coincides with the Western-Sakhalin fault in the southern areas of the study region. Our data on the Central and Northern Sakhalin does not contradict with the conclusion in [ Savostin et al., 1982 ] concerning this boundary.

On subsurface fracture opening and closure

Understanding of subsurface fracture opening and closure is of great importance to oil/gas production, geothermal energy extraction, radioactive waste disposal, and carbon sequestration and storage. Fracture opening and closure involve a complex set of thermal, hydrologic, mechanical and chemical (THMC) processes. In this paper, a fully coupled THMC model for fracture opening and closure is formulated by explicitly accounting for the stress concentration on aperture surface, stress-activated mineral dissolution, pressure solution at contacting asperities, and channel flow dynamics. A model analysis, together with reported laboratory observations, shows that a tangential surface stress created by a far-field compressive normal stress may play an important role in controlling fracture aperture evolution in a stressed geologic medium, a mechanism that has not been considered in any existing models. Based on the model analysis, a necessary condition for aperture opening has been derived. The model provides a reasonable explanation for many salient features of fracture evolution in laboratory experiments, including a spontaneous switch from a permeability reduction to a permeability increase in a static limestone experiment. The work may also help develop a new method for estimating in-situ stress in a reservoir.

A numerical study of ultraprecision machining of monocrystalline silicon with laser nano-structured diamond tools by atomistic simulation

Three-dimension molecular dynamics (MD) simulations is employed to investigate the ultraprecision machining of single crystal silicon with structured nanoscale diamond tool fabricated by laser. The advantages and disadvantages of diamond machining using structured tools are discussed in comparison with those of using non-structured tools. The von Mises stress distribution, hydrostatic stress distribution, atomic displacement, stress, the radial distribution function, cutting forces, frictional coefficient, subsurface temperature and potential energy during the nanometric machining process are studied. A theoretical analysis model is also established to investigate the subsurface damage mechanism by analyzing the distribution of residual stress during the nanoscale machining process. The results show that a structured nanoscale tool in machining brittle material silicon causes a smaller hydrostatic stress, a less compressive normal stress σxx and σyy, a lower temperature and a smaller cutting force. However, the structured nanoscale tool machining results in smaller chip volume and more beta-silicon phase. Besides, the friction coefficient for tool with V-shape groove is smaller than those for non-structured tools and other structured nanoscale tools. This means that the tool with V-shape groove can reduce the resistance to cutting during the nanoscale machining process. In addition, the results also point out that the potential energy of subsurface atoms and the number of other atoms for pyramid-structured tool are much smaller than those of using non-structured tools and other structured nanoscale tools.