Axial Slip Research Articles

Axial rod slip at the end-of-construct screw in scoliosis surgery: relevance, occurrence and prevention

PurposeDespite standardized biomechanical tests for spinal implants, we recently recognized pedicle screw failure to maintain the rod fixated as a clinical concern in scoliosis surgery. This occurrence study investigates the risk and magnitude of axial rod slip (ARS), its relation with technique and preventive measures.MethodsRetrospective multicenter review of all primary scoliosis cases (2018–2020) with > 1 year FU from three centers, instrumented with uniplanar screws and 5.5 mm CoCr rods (Mesa 2, Stryker Corporation, Kalamazoo, MI, USA). ARS was defined as > 1 mm change in residual distal rod length from the screw in the lowest instrumented vertebra (LIV) and assessed by two independent observers. Slip distance, direction, relation to distal screw density and time of observation were recorded, as well as the effect of ARS on caudal curve increase. To prevent slip, more recent patients were instrumented with a different end-of-construct screw (Reline, NuVasive Inc. San Diego, CA, USA) and analyzed for comparison.ResultsARS risk was 27% (56/205) with a distance of 3.6 ± 2.2 mm, predominantly convex. 42% occurred before 4 months, the rest before 1 year. The caudal curve substantially increased three times more often in patients with ARS. Interobserver reliability was high and slip was in the expected direction. ARS was unrelated to distal screw density. Remarkable variation in ARS rates (53%, 31%, 13%) existed between the centers, while there was no difference in mean screw density (≈1.3 screws/level) or curve correction (≈60%). Revision surgery for ARS was required in 2.9% (6/207). Using the different end-of-construct screw, ARS risk was only 2% (1/56) and no revisions were required.ConclusionThis study demonstrates the prevalence of axial rod slip at the end of construct in scoliosis surgery and its clinical relevance. While minimal ARS can be subclinical, ARS should not be mistaken for adding on. The most severe ARS predominantly occurred convex at the high-loaded distal screw when L3 was the LIV. Longer constructs (LIV L3 or L4) have a higher risk of ARS. The minimal risk of ARS with another end-of-construct screw underscores the influence of screw type on ARS occurrence in our series. Further research is essential to refine techniques and enhance patient outcomes.

Effect of interference magnitude on fretting wear and fatigue strength of scaled press-fitted railway axles

Railway axles represent a typical example of interference fit structures that are vulnerable to fretting fatigue induced by rotational bending loads. This study investigated the influence of interference magnitude on the fretting wear and fatigue of scaled press-fitted railway axles. In this study, the fretting fatigue strength was tested at three interference magnitudes within the standard range, and the fretting wear and fretting cracks were analyzed. The results indicate a trend where the fretting fatigue strength initially rises and then declines with increasing interference magnitude. 3D finite element models, with and without considering the fretting wear, were developed to investigate the variation in contact parameters in the press-fitted region, and the Smith-Watson-Topper multiaxial fatigue model was employed to evaluate the fretting fatigue behavior. The results demonstrate that the competition between contact pressure and axial slip produces relatively slight fretting wear when the interference magnitude takes the middle value, thereby causing a minor stress concentration and ultimately leading to higher fretting fatigue strength.

Study on the static stability of aluminum alloy single-layer spherical reticulated shell

In order to study the static stability of an aluminum alloy single-layer spherical reticulated shell, a static loading test of a K6 reticulated shell with 3 rings, a 4 m span, and a 1/7 height-to-span ratio is carried out. The deformation, internal force distribution, and failure mode of the reticulated shell model are discussed. By comparing the monotone tensile test and simulation of the single member, the simulation method of rivet used in the finite element model (FEM) is obtained, and the bending stiffness and axial slip stiffness of gusset joints are calculated. Considering the joint stiffness in the FEM, the simulation results and the test fit well, indicating that the influence of the joint stiffness on the static stability of the reticulated shell cannot be ignored. In addition, by comparing the effect of different parameters of joint stiffness, the axial slip stiffness should be considered in the stability design of reticulated shells.

Advanced winding tension method for preventing axial slip of the center-wound roll

Center winding is one of the most suitable and universal schemes in the winding mechanism. In general, the quality of wound rolls is significantly degraded by axial slip. In this paper, an advanced winding tension method is proposed to overcome axial slip. Firstly, the axial slip mechanism is analyzed by means of the mutual mechanical relationship between the layers of the center-wound roll. Secondly, a mathematical model for overcoming axial slip was developed based on the correlation between axial slip and winding tension. Then, based on the mathematical model, a special neural network structure with back propagation training is developed so that the winding tension is dynamically updated with the winding radius. Finally, a roll-to-roll slitting system for lithium-ion battery pole pieces is proposed and used to verify the performance of the proposed method. The experiments show that there is no quality problem of axial slip in the center-wound rolls wound by the winding tension control method proposed in this paper. It shows that the winding tension control method proposed in this paper is effective in preventing axial slip.

Study on the Mechanical Properties of Continuous Composite Beams under Coupled Slip and Creep

Steel–concrete continuous composite beams are widely used in buildings and bridges and have many economic benefits. Slip has always existed in composite beams and will reduce the stiffness of composite beams. The effect of creep under a long-term load will also be harmful. Many scholars ignore the combined effects of slip and creep. In order to more accurately study the mechanical properties of steel–concrete continuous composite beams under long-term loads, this paper will consider the combined actions of slip and creep. By combining the elastic theory and the age-adjusted effective modulus method, the differential equation of the composite beam is derived via the energy variational method. The analytical solutions of axial force, deflection and slip under a uniform load are obtained by substituting the relevant boundary conditions. The creep equation is used to simulate the behavior of concrete with time in ANSYS. The analytical solution is verified by establishing a finite element model of continuous composite beams considering slip and creep. The results suggest the following: the analytical solution is consistent with the finite element simulation results, which verifies the correctness of the analytical solution. Considering the slip and creep effects will increase the deflection of the composite beam and the bending moment of the steel beam, reduce the bending moment of the concrete slab and have a significant impact on the structural performance of the continuous composite beam. The research results considering the coupling effect of slip and creep on continuous composite beams can provide a theoretical basis for related problems.

Using Transient Modeling to Define the Effects of Heave on Wellsite Operations

Summary The drilling industry is striving to be more efficient, reducing time, costs, and emissions to provide energy solutions for a more climate-conscious world. Reducing nonproductive time (NPT) and invisible lost time (ILT) by utilizing modeling software to optimize tripping operations is one method to combat this. Additional factors such as sea heave have a significant impact on tripping operations on semisubmersible drilling vessels, which do not show a linear response to increased heave. These vessels have compensation systems, but they are often not in use or not completely accurate. Typical heave experienced in the North Sea is between 0.5 and 3-m amplitude and 10–30-second heave period. In this study, transient modeling software is used to create a digital twin of the wellbore to safely predict the tripping speed and define the effect heave has on the tripping operations, from causing additional swab and surge pressures when in or out of slips to reducing tripping speed and improving efficiency by reducing mud gelling at connections. To further understand the effect heave has on tripping operations, experimental simulations of varying heave magnitude were completed in wellbore sections of 0°, 30°, 60°, and 90° inclination. Model validation was completed before running simulations. The results indicate that in horizontal holes, low heave magnitudes result in no bit or pressure response. The same cannot be said for vertical wells, which show smooth bit movement and pressure response throughout the heave magnitude spectrum. However, in a horizontal hole when the wave height is of a larger magnitude, sufficient to break wellbore friction, bit displacement is observed to display jerky axial stick and slip movement, and resultant increased swab and surge pressures are shown even when accounting for the reduced pressure fluctuations due to string eccentricity in an inclined wellbore. It is proposed that much of the related mechanical and pressure response is due to the properties of the drilling mud, string elasticity, and the forced frequency of the waves on the natural frequency of the drilling rig and drillstring. It is clear from definitive and experimental simulations that extra care must be taken when the heave is significant to maintain wellbore stability and reduce wellbore pressure cycling.

Study on Mechanical Properties of Simply-Supported Composite Beams Considering Creep and Slip

In the current industry, steel–concrete composite beams are used in large-span bridges and super-high-rise building structures due to their excellent overall performance. Concrete’s creep and slip effects in the combined structure can adversely affect the structure, thus affecting the safe use of bridges and buildings. It is necessary to study the mechanical properties of the combined structure considering creep and slip. In order to further study the mechanical properties of steel–concrete composite beams under creep–sliding coupling, in this study, based on the energy variational method principle, the energy equation of a composite beam considering creep and slip coupling is established. The second-order differential equation of the axial force of steel–concrete composite beams is derived by introducing basic assumptions. The calculation formulas for the axial force, deflection, and slip of simply-supported composite beams under different loads are obtained using different boundary conditions. Then, the creep effect of composite beams is simulated using the creep criterion in the ANSYS finite element software when the concrete material parameters change with time. The results show that a simply-supported composite beam considering both slip and creep will have a significant effect on the structure; the more strongly the studs constrain the concrete slab, the greater the adverse effect of concrete creep on the combined beam. The formula derived in this paper is consistent with the numerical simulation solution and is suitable for different creep and slip conditions. The research results can provide a theoretical basis for the calculation of the axial force, deflection, and slip of combined beams under uniform and concentrated loads in practical engineering considering slip and creep.

Study on hydrodynamic characteristics of the liquid-solid circulating fluidized bed with a central pulsating nozzle by numerical approach

• A novel LSCFB with a central pulsating nozzle is proposed. • Hydrodynamics of the riser was studied by three-dimensional numerical simulation. • With the central pulsating flow, the radial interphase mixing degree is enhanced. • Regression formulas of the axial and radial slip velocities are obtained. Pulsating fluidization is gaining increasing attention due to its superiority in efficiency improvement. A novel type of liquid–solid circulating fluidized bed with a central pulsating nozzle was proposed to improve the reaction efficiency in this work. Based on Eulerian-Eulerian two-fluid model and the kinetic theory of granular flow, the hydrodynamic characteristics in the riser was investigated by three-dimensional numerical simulation. The effects of pulsating liquid flow and particle properties on the distributions of solids holdup, the radial velocity of the particles, the slip velocity and the radial mixing degree were studied. The simulation results showed that with the addition of the central pulsating liquid flow, the particles displayed apparent radial motion, and the interphase mixing degree as well as the interphase mass transfer efficiency were enhanced. Based on the numerical results, the regression formulas of the axial and radial slip velocities were obtained respectively.

Experiments on the localized interaction at the interface fuel rod/spacer grid in pressurized water reactors

The release of fissile material into the coolant caused by fretting of the fuel rods at the interface with spacer grids is a significant safety issue and cause of financial losses in the operation of Pressurized Water Reactors (PWRs). Each fuel rod is kept in position inside spacer grids through friction from the preload exerted by retaining elements (springs and dimples). Fretting of the fuel rods occurs at the contact with the springs and dimples. In severe fretting cases the integrity of the fuel rod cladding is compromised and fission byproducts enter the primary coolant circuit. The reciprocating motion at the contact interface of the fuel rods and spacer grids resulting in material fretting is due to the Flow-Induced Vibrations (FIV) of fuel rods, caused by the unstable surrounding coolant flow, which in PWRs is predominantly parallel to the length of fuel rods (axial flow). Under specific flow conditions, fretting develops rapidly. The vibrations of fuel rods, as well as the relationship of fretting wear mechanisms with several factors associated with the fission process and coolant flow dynamics and stability (vibration amplitude, preload, oscillating loads, irradiation, axial slip, spring relaxation, temperature, oxidation, material of spacer grids and fuel rods), have been considered in the literature. However, direct experimental measurements of the contact force and axial slip during FIV have not been treated in the literature, likely because of the absence of suitable measurement methods. This gap in experimental measurement techniques is addressed in this work, specifically for the analysis of PWR fuel assemblies, by installing a piezoelectric stack and aiming laser Doppler vibrometers on a one-meter-long fuel rod, supported by two full-scale spacer grids, in-air or immersed in quiescent water. In the presence of small- and large- amplitude forced vibrations, the signal of the piezoelectric force transducer increases with the amplitude of vibration, but it is also affected by vibrations perpendicular to the excitation, which appear for large-amplitude excitations. The axial motion of the fuel rod at the spacer grid has a complex evolution and is significant for large-amplitude vibrations only. At any rate, the time histories of contact force and axial motion display the effects of impacts and slips, particularly during the tests in water. The measurement system shows that the severity of the interaction at the spacer grid interfaces is influenced strongly by the amplitude of the forced fuel rod vibrations. Since fuel rods and fuel assemblies are prone to several nonlinear phenomena, as demonstrated by recent studies, it follows that the usage of nonlinear models will be essential to numerically estimating the severity of fretting.

Hydrodynamics of gas flow in a rotating packed bed under floating motions: Experimental and simulation study

As a typical process intensification device, a rotating packed bed (RPB) is promising for marine gas separation and purification. Previous studies have focused on the gas-phase characteristics of onshore RPBs without the function of floating motions. In this study, the effect of the six degrees of freedom floating motions on the gas-phase characteristics was investigated by experiments and simulation. Compared to the pressure drop under stationary conditions, the pressure drop under floating motions is generally lower and fluctuates. The heave motion causes a significant deviation and oscillation in the pressure drop. The simulation results revealed that the turbulence-enhanced zone (T-E zone) and the turbulence-weakened zone (T-W zone) appeared alternately and caused an evolution of the maldistribution factor. The floating motions enhance or weaken the radial, axial, and tangential slip velocities of the gas phase, which leads to the presence of a T-E/T-W zone and variation of flow direction. The results provided a deep understanding of offshore RPBs performance.

The meshing and failure analysis of haulage wheels with the effect by shearer’s poses

The high reliability of the longwall shearer is far-reaching to the efficient operation of coal mines and the stable supply of energy. However, traction problems caused by the haulage wheel’s failure are prominent. Therefore, for exploring the damage mechanisms of the haulage wheel by the shearer’s pose and optimizing the traction structure, a meshing model between haulage wheels and pin row is established, with the non-standard center distance and the oblique angle, respectively. And the effects of the shearer’s pose of the jumping and swinging around the vertical direction on meshing performances are studied. The result indicates the radial runout of haulage wheels is the most violent when the teeth alternate meshing, and the maximum runout amplitude is 1.563 mm. With the radial runout increasing, the average peak force increases, and the stress concentration range of the tooth root expands to the pitch line position. The shearer’s swing around the vertical direction causes the axial impact force of the haulage wheel. With the swing angle increasing, the stability and safety of the haulage wheel decrease. As the velocity increases, the axial slip on the tooth surface aggravates while effective meshing width decreases when the haulage wheel is affected by oblique angle. The result provides a reference for reducing the shearer’s hauling fault.

The correlation of c-to-a axial ratio and slip activity of martensite including microstructures during thermomechanical processing of Ti–6Al–4V alloy

This study deals with the correlation of the “c-to-a” ratio of ά-martensite and the activity of basal/secondary slip systems during thermomechanical processing of Ti–6Al–4V alloy. Two martensite including microstructures (dual phase α+ά and full ά martensite) were prepared and deformed in tensile mode at 300 °C and 600 °C. The presence of ά-martensite caused the reduction of the c-to-a ratios compared to that of the as-received α+β starting microstructure. Owing to the elemental partitioning, the amount of axial ratio reduction was considerable in the case of dual phase α+ά microstructure and caused activation of pyramidal slip during low temperature tensile deformation. This promoted the wavy configuration of dislocation and led to intensified substructure development. At higher deformation temperature, where the martensite phase was almost completely converted into the fine α+β phase through reverse transformation, the c-to-a ratio reached ∼1.599 increasing the critical resolved shear stress of the secondary slip systems.

Modeling the anchoring and performance of downhole equipment using an extended Gurson model

In oil and gas (O&G) exploration the well casing, in the form of a long steel tube, maintains the opening of the drilled well hole. Mechanical equipment is often inserted into the well for the purpose of well monitoring, pressure control and various operations. This downhole equipment may be mechanically connected to the pipe casing by the outward radial motion of anchoring teeth such that the inner wall casing is indented. The connection between the tool and the casing must support significant mechanical loads in the longitudinal (axial) direction of the casing, i.e. transverse to the direction of indentation, while minimizing the indentation depth in order to preserve the stiffness and strength of the casing. Consequently, a determination of the ultimate strength of the connection is of critical importance. Failure of this connection involves intense shear of the inner wall of the casing, akin to a machining operation. The critical load for axial slip can be determined experimentally or numerically (or by combination of both). In this study, detailed simulations are performed using the shear-extended GTN (Gurson-Tvergaard-Needleman) model. The choice of model is motivated by the need to accurately the extensive plastic deformation associated with indentation as well as shear-dominated ductile failure on a sub-millimeter scale.The shear-extended GTN model requires a careful calibration of the model parameters by an accurate measurement of the material response. Accordingly, the casing steel was characterized by appropriate measurements under a range of stress states. The calibrated model was used to investigate an idealized two-dimensional representation of the anchoring problem, with a focus on the effect of indentation depth upon connection strength. Both the indentation of the casing inner wall by the anchoring teeth and the subsequent shear of the casing wall were simulated in detail to determine the load required to initiate and progress slip of the anchoring teeth. The results of these analyses show that the connection strength increases linearly with increasing indentation depth.

EVALUATION OF BOLT AXIAL TENSION FORCE AND SLIP STRENGTH FOR HIGH-STRENGTH BOLTED CONNECTIONS AFTER HEATING AND COOLING PROCESSES

EVALUATION OF BOLT AXIAL TENSION FORCE AND SLIP STRENGTH FOR HIGH-STRENGTH BOLTED CONNECTIONS AFTER HEATING AND COOLING PROCESSES

Non-linear Radiation and Navier-slip effects on UCM Nanofluid Flow past a Stretching Sheet under Lorentzian Force

In the present article, the novel contributions are modelling of Upper convected Maxwell nanoflow under Lorentzian influence over a stretching surface and investigating it using bvp4c procedure with MATLAB software. The boundary is set fixed with axial slip. Non-linear energy distribution is incorporated. Similarity variables are utilized to transmute non-linear PDEs of the basic fluid model to coupled system of ODEs. Computed numerical results are better compared with the past literature work to evidence its efficacy. The nanoflow momentum, energy, species diffusion are visualized graphically and analyzing the performance of proficient physical quantities on shear stress, energy dispersion coefficient, mass diffusion coefficient scatter of the system are seen through tables. Presence of magnetic field reduces friction at the wall and acts as a cooling agent.Navier slip increases the friction factor near the wall. Non-linear radiation transfers more heat from the system. Energy transfer coefficient is high in linear thermal rather than non-linear thermal distribution.

Internal energy activation stimulus on magneto-bioconvective Powell-Eyring nanofluid containing gyrotactic microorganisms under active/passive nanoparticles flux

Influence of Stephan blowing on a three-dimensional hydro magneto-bioconvective Eyring-Powell nanofluid containing Gyrotactic microorganisms under active and passive nanoparticle flux conditions is investigated in this paper. The presence of non-linear radiation along a bidirectional stretched surface is also deliberated throughout this analysis. A comparative study is made up for active and passive nanoparticle volume control. The study is relevant to novel microbial fuel cell technologies combining the nanofluid with bioconvection phenomena. The Prandtl’s boundary layer equations, approximated by Oberbeck-Boussinesq’s are studied under suitable boundary conditions. Similarity transformation is used to transform the governing boundary layer equations to dimensionless nonlinear ordinary differential equation model. The non-linear model is then resolved by combining the Runge–Kutta method and the MATHEMATICA software. The dimensionless velocity, temperature, nanoparticle concentration and density of motile microorganisms together with the wall shear stress, Nusselt, Sherwood and density of motile microorganism number are graphically presented to visualize the effects of particular parameters. A novel idea of Stefan blowing on three-dimensional space taking into consideration the non-linear radiation is implemented in the investigation of Eyring-Powell flow over a deformable sheet under the effects of slip and activation energy for the first time. Axial Newtonian slip decreases the momentum of the nanoflow while tangential slip augments the flow. Bio-convection parameter reduces the nanoparticle concentration of the rescaled density of motile microorganisms. Skin friction factor is dominant in passive nanoparticles flux rather than active nanoparticles flux. Passive nanoparticles help in smooth delivery of drugs which is seen here for zero mass flux. Energy transfer rate is high compared to active nanoparticle volume control. A zero mass flux acts as a cooling agent in this study by diffusing more heat from the system.

Numerical study of electroosmosis-induced alterations in peristaltic pumping of couple stress hybrid nanofluids through microchannel

This paper presents a computational modeling approach to analyze the peristaltic pumping of couple stress hybrid nanofluids regulated by the electroosmosis mechanism through a microchannel. The effects of applied magnetic field, Joule heating and buoyancy have also been computed. In this analytical model, water-based titanium dioxide (TiO2) and silver (Ag) hybrid nanofluids have been considered. For more relevant physical problem, the axial velocity slip and thermal slip conditions have also been introduced. The nonlinear differential equations are simplified by considering the Huckel–Debye approximations as well as lubrication theory, and then the equations have been solved numerically by Mathematica 10 software via the NDsolve commands. The pertinent influences of key parameters on the axial velocity, nanoparticle temperature, Nusselt number and streamlines in the microchannel have been visualized graphically. It is observed that an increase in the thermal Grashof number produces a maximum axial velocity, and temperature of nanoparticles for both water–titanium dioxide and water–silver nanofluids. The maximum axial velocity and nanoparticle temperature occur in water–titanium dioxide as compared with water–silver. The outcomes of this model shall be very useful in the designs of smart electro-peristaltic pumps for thermal systems and drug delivery systems.

Research on the Fretting Slip Characteristics of Interference Fit Surface of Train’s Wheelset Running in Heavy Loads

Running under the condition of heavy loads and accelerating status, the fretting damage of wheelset interference fit surface brings great hidden danger to the running safety of the train. Based on heavy loads train equipment parameters and running conditions by using the finite element software ABAQUS finite element model is established and simulated by different axle load and wheel inner hole under the conditions of different amount of interference with the axle wheel seat interference fitted surface fretting slip three-dimensional distribution, and the interference fit different axial location wheel revolving process of three feature points in axial and tangential fretting slip. The results show that the axial fretting slip of the edge of the interference fit surface is much larger than that of the middle, and the outer side is larger than the inner side, with a maximum value 22 µm; tangential fretting slip of interference fit surface reaches the maximum value 9.8µm, when the node rotates by about 270°. The influence of the value of shrink fit on fretting slip is more obvious than that of loads on the axle of the wheelset.

Mechanical behavior of steel–concrete composite joints in railway hybrid cable-stayed bridges

The mechanical behavior of steel–concrete composite joints (SCCJs) on a high-speed railway hybrid cable-stayed bridge was investigated by performing a model test with a scale of 1:2.5. Structural responses that included stress distributions, deformation characteristics, crack pattern, and failure mode were presented and discussed. Two simplified formulas for deflection and rotation were proposed to evaluate the deformation performance of the SCCJ. The results indicated that the SCCJ still exhibited sufficient strength and excellent deformation performance under twice the design load for which the SCCJ could satisfy the high safety and smoothness requirements for supporting a high-speed train in motion. An uneven stress distribution among shear connectors was also found. The test results also show that the concrete girder adjacent to the SCCJ failed earlier than the SCCJ, which indicates that the flexural resistance of the SCCJ is higher than the adjacent concrete girder. Furthermore, parameter analyses that employed a nonlinear finite element model were conducted to provide an insight into the load transfer mechanism. The numerical results indicated that approximately 33.0% and 5.8% of axial force was transferred through the end and front bearing plates, respectively. The thickness of the end bearing plate would definitively influence the axial force transfer and slip distribution, while that of the front bearing plate had only a slight influence on them. The numerical results also revealed an uneven load distribution among the multilayered shear connectors.

Ductile iron pipeline response to earthquake-induced ground rupture

This article provides a comprehensive evaluation of ductile iron (DI) pipeline response to earthquake-induced ground deformation through the results of a large-scale testing program and a fault rupture test on a 150-mm DI pipeline with restrained axial slip joints. The test is used to validate a two-dimensional finite element (FE) model that accounts for soil–pipeline interaction with axial slip, pullout resistance, and rotation of pipe joints. The maximum strike-slip fault offset sustained by push-on, restrained, and restrained axial slip joints is presented as a function of the pipeline/fault crossing angle. DI pipeline performance is controlled by one of the following limit states; tensile, compressive, rotational joint capacity, or local buckling in the pipe barrel. A systematic FE assessment shows that pipelines with restrained axial slip joints accommodate 2–9 and 2–10 times as much fault offset as pipelines with push-on and restrained joints, respectively, for most intersection angles. The results of this work can be used for simplified design and to quantify the relative earthquake performance of different DI pipelines.