Cantilever Force Research Articles

Cantilever Force Distribution on Jack-Up Rig

Cantilever is the most important structure of the jack-up rig. Jack-up usually has three working conditions: drilling condition, storm condition, preloading condition. The fulcrums of the cantilever in the drilling condition are less than the other two. So the distribution of the cantilever force in the storm and preloading conditions becomes extremely complicated with the increase of fulcrums. In order to facilitate the evaluation of jack-up rig strength, a simplified analytical method and a finite element method (FEM) are presented to distribute the cantilever force on a jack-up rig during the storm and preloading conditions. For the simplified analytical method, the fulcrum force is obtained from the distance between the fulcrum and the position of the cantilever resultant force. For the FEM, the cantilever is assumed to be perfect rigid body without any strain. The fulcrum force is calculated according to the balance of the fulcrum forces. Both results of fulcrum force are analyzed and compared. It is shown that they are in good agreement. Thus both methods can be applied in distributing the cantilever force to evaluate the strength of jack-up rig.

Effect of cobalt doping on the mechanical properties of ZnO nanowires

In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases were close to theoretical strength indicating high quality of NWs. Dependence of mechanical properties on NW diameter was found for both doped and undoped ZnO NWs.

Employing electro-mechanical analogies for co-resonantly coupled cantilever sensors

Abstract. Understanding the behaviour of mechanical systems can be facilitated and improved by employing electro-mechanical analogies. These analogies enable the use of network analysis tools as well as purely analytical treatment of the mechanical system translated into an electric circuit. Recently, we developed a novel kind of sensor set-up based on two coupled cantilever beams with matched resonance frequencies (co-resonant coupling) and possible applications in magnetic force microscopy and cantilever magnetometry. In order to analyse the sensor's behaviour in detail, we describe it as an electric circuit model. Starting from a simplified coupled harmonic oscillator model with neglected damping, we gradually increase the complexity of the system by adding damping and interaction elements. For each stage, various features of the coupled system are discussed and compared to measured data obtained with a co-resonant sensor. Furthermore, we show that the circuit model can be used to derive sensor parameters which are essential for the evaluation of measured data. Finally, the much more complex circuit representation of a bending beam is discussed, revealing that the simplified circuit model of a coupled harmonic oscillator is a very good representation of the sensor system.

Prolonged controlled mechanical ventilation in humans triggers myofibrillar contractile dysfunction and myofilament protein loss in the diaphragm

BackgroundProlonged controlled mechanical ventilation (CMV) in humans and experimental animals results in diaphragm fibre atrophy and injury. In animals, prolonged CMV also triggers significant declines in diaphragm myofibril contractility. In...

In vitro experimental investigation of the forces and torque acting on the scaphoid during light grasp.

The aim of this study was to measure the magnitude and direction of forces and torque within osteotomized scaphoids within cadaveric wrists during grasping movement of the hand. The mechanical contributions of clinically relevant individual wrist-crossing tendon groups were investigated. Wrists of eight forearms were immobilized in the sagittal, transverse, and coronal plane on a fixation device with unhindered axial gliding. The scaphoid was osteotomized and the fragments stabilized using an interlocking nail. The nail served as a sensor for measurement of inter-fragmentary forces orthogonal and torque around the sensor axis. Thus, torque and cantilever forces were measured which originated between the fragments through co-contraction through the activity of wrist-crossing tendons. Grasping movement of the hand induced a mean maximum torque of 0.038 ± 0.051 Nm and a force of 4.01 ± 1.71 N on the scaphoid. The isolated activation of thumb tendons resulted in a torque of 9.9 E-3 ± 7.7 E-3 Nm and a force of 1.42 ± 0.49 N. Despite immobilization of the wrist, grasping movement of the hand caused substantial forces and torque within the osteotomized scaphoid bone in varying directions and severity among different specimens. These factors may contribute to the development of nonunions and malunions in unstable scaphoid fractures through interfragmentary micromotion. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1734-1742, 2016.

Cantilever Force Sensor based on Photonic Crystals Ring Resonator: A Review

Cantilever Force Sensor based on Photonic Crystals Ring Resonator: A Review

Fabrication of wrist-like SMA-based actuator by double smart soft composite casting

A new manufacturing method for smart soft composite (SSC) actuators that consists of double casting a SSC actuator to produce an actuator with non-linear shape memory alloy (SMA) wire positioning is proposed. This method is used to manufacture a tube-shaped SSC actuator in which the SMA wires follow the curvature of the tube and is capable of pure-twisting deformations while sustaining a cantilever load. The concept is tested by measuring the maximum twisting angle and a simple control method is proposed to control the twisting angle of the actuator. Then, a soft robotic wrist with a length of 18 cm is built, its load-carrying capability is tested by measuring the cantilever force required for deforming the actuator, and its load-carrying capability during actuation is tested by loading one end with different objects and actuating the actuator. This wrist actuator shows good repeatability, is capable of twisting deformations up to 25° while holding objects weighing 100 g, and can sustain loads above 2 N without undergoing buckling.

In vivo epicardial force and strain characterisation in normal and MLP-knockout murine hearts

The study’s objective is to quantify in vivo epicardial force and strain in the normal and transgenic myocardium using microsensors.Male mice (n = 39), including C57BL/6 (n = 26), 129/Sv (n = 5), wild-type (WT) C57 × 129Sv (n = 5), and muscle LIM protein (MLP) knock-out (n = 3), were studied under 1.5% isoflurane anaesthesia. Microsurgery allowed the placement of two piezoelectric crystals at longitudinal epicardial loci at the basal, middle, and apical LV regions, and the independent (and/or concurrent) placement of a cantilever force sensor. The findings demonstrate longitudinal contractile and relaxation strains that ranged between 4.8–9.3% in the basal, middle, and apical regions of C57BL/6 mice, and in the mid-ventricular regions of 129/Sv, WT, and MLP mice. Measured forces ranged between 3.1–8.9 mN. The technique’s feasibility is also demonstrated in normal mice following afterload, occlusion–reperfusion challenges.Furthermore, the total mid-ventricular forces developed in MLP mice were significantly reduced compared to the WT controls (5.9 ± 0.4 versus 8.9 ± 0.2 mN, p < 0.0001), possibly owing to the fibrotic and stiffer myocardium. No significant strain differences were noted between WT and MLP mice.The possibility of quantifying in vivo force and strain from the normal murine heart is demonstrated with a potential usefulness in the characterisation of transgenic and diseased mice, where regional myocardial function may be significantly altered.

Single Cell Wall Nonlinear Mechanics Revealed by a Multiscale Analysis of AFM Force-Indentation Curves

Individual plant cells are rather complex mechanical objects. Despite the fact that their wall mechanical strength may be weakened by comparison with their original tissue template, they nevertheless retain some generic properties of the mother tissue, namely the viscoelasticity and the shape of their walls, which are driven by their internal hydrostatic turgor pressure. This viscoelastic behavior, which affects the power-law response of these cells when indented by an atomic force cantilever with a pyramidal tip, is also very sensitive to the culture media. To our knowledge, we develop here an original analyzing method, based on a multiscale decomposition of force-indentation curves, that reveals and quantifies for the first time the nonlinearity of the mechanical response of living single plant cells upon mechanical deformation. Further comparing the nonlinear strain responses of these isolated cells in three different media, we reveal an alteration of their linear bending elastic regime in both hyper- and hypotonic conditions.

Monitoring method of rice seeds mass in vibrating tray for vacuum-panel precision seeder

According to the physical properties of rice seeds, triaxial ellipsoidal particle models were established based on the multi-sphere approach, and simulations of seeds motion in a vibrating tray were performed using the discrete element method (DEM). It was shown that the normal impact force Fn of seeds action on the tray was mainly composed of transient impact and accumulation force sections. The value of transient impact force was not stable because it was influenced comprehensively by shape of seed, vibration parameter and seeds-mass-per-unit-area (SMA). The variation of accumulation force determined by impulse change of seeds was relatively stable. Simulation results indicated that its value was almost linearly varied with SMA under a certain vibration parameter, and a real-time monitoring method of seeds mass in a vibrating tray is presented in this paper.Two cantilever force sensors were back-to-back fixed at the bottom of seed tray. Due to a phasic difference ψ existed between the vibration inertia force and the seeds normal impact force Fn, a differential operation was performed between the output signals of two sensors to eliminate the influence of inertia force and extract Fn effectively. Then, a signal processing circuit mainly composed of differential amplifier, active low-pass filter, bias voltage circuit, envelope detector, and passive low-pass filter in series was designed to detect seeds mass. Calibration tests were carried out in laboratory with vibration frequency f and amplitude A of tray in the ranges of 9–13Hz and 3–5mm, the results showed that the comprehensive measurement errors were <3.5% with SMA κ in the range of 0.2–1.8g/cm2.

Force Transients during Stretch of Myofibrils Activated with MgADP

When muscle fibres are subjected to a fast stretch while activated, the force increases rapidly to attain a peak, hereby referred to as critical force (Pc). Although there is still uncertainty on the mechanism responsible for Pc, it has been commonly associated with the state of crossbridges attached to actin. In the present study, we used fast stretches to investigate myofibrils activated with Ca2+ or MgADP, which biases crossbridges into a strongly bound state. Isolated myofibrils were attached between an atomic force cantilever and a micro-needle using micromanipulators. A multi-channel perfusion system connected to a double-barreled pipette was used to activate myofibrils with calcium (pCa2+ 4.5) or MgADP (20mM). After force was fully developed, myofibrils were stretched by 3% of SLo at 10 SLo.s−1. MgADP activation resulted in a higher Pc (1.37 ± 0.07 P/Po) than Ca2+ activation (Pc = 1.23 ± 0.03 P/Po) without changing the critical extension required to reach such force (MgADP = 25.01 ± 1.59 nm/HSL; Ca2+ = 24.99 ± 2.68 nm/HSL). This result suggests that myofibrils activated with MgADP produce less force, but are stiffer than myofibrils activated with Ca2+. Crossbridges induced to strongly bound state via MgADP activation may cause further crossbridge formation while generating less force in comparison with crossbridges that undergo the power-stroke. However they can resist stretching when the myofibrils are stretched.

An electrospun PVDF-TrFe fiber sensor platform for biological applications

Flexible, self-powered materials are in demand for a multitude of applications such as energy harvesting, robotic devices, and lab-on-a chip medical diagnostics. Electrospinning piezoelectric fluoropolymers into nanofibers can provide these functionalities in a facile method. PVDF-TrFe was electrospun in an aligned format and interfaced with a flexible plastic substrate in order to create a platform for voltage response characterization after small force cantilever deformations. Voltage peak signals were an average of ±0.4V, and this response did not change after platform sterilization. However, when placed in cell culture media, piezoelectric response was dampened. This platform can be used for measurement and analysis of electromechanical behavior in a variety of applications, including cellular-powered nanodevices.

Measurement of cantilever spring constant using an electrostatic sensing and actuating force measurement system

We report the measurement of the spring constant of a cantilever using an electrostatic sensing and actuating force measurement system. The force measurement system consists of three main parts: a monolithic flexure stage, a three-electrode capacitor, and a digital controller. The most important feature of the system is the utilization of the three-electrode capacitor simultaneously as a position sensor and an electrostatic force generator. This allows us to constantly adjust and maintain gap distances between three electrodes, which is critical for this design to generate precise electrostatic compensation force. The force measurement system was partly upgraded and its performance was improved. The uncertainty estimation for the upgraded force measurement system is given. By measuring the spring constant of a commercially available cantilever force sensor, we demonstrate that the force measurement system is capable of calibrating the cantilever spring constant. The spring constant of the cantilever force sensor was measured to be (2227 ± 63) mN m−1 (coverage factor k = 2), corresponding to a relative expanded uncertainty of 2.8%.

Surface Magnetostriction Model for MagNEMS

In this work the in uence of surface roughness on magnetostrictive nano-actuator parameters has been analyzed theoretically. A mechanical and magnetoelastic behavior of investigated cantilever bimorphic system has been described in the frame of the simple analytical model. Realistic material parameters have been incorporated into the model for high-magnetostrictive galfenol (Fe-Ga) thin lms on silicon substrate. It has been shown that for 5 nm thick galfenol lm a at surface magnetostrictive e ects modify the cantilever de ection and force only by 3%, whereas in the case of rough surface this in uence increases to about 15%, when dimensions of roughness steps are comparable to the distances between them.

Mechanical properties of atomic force microscopy probes with deposited thin films

Deposition of thin films on atomic force microscopy (AFM) probes is a common technique that is used to either improve the light reflectance of the back side of the probe cantilevers or to modify the surface properties of the probe tips. However, this technique also affects the force constant and resonance frequency of the AFM cantilevers. The present work investigates theoretically this effect in the approximation of very thin films. The cantilever force constant changes due to the contribution of bending moment of the elastic force in the deposited film, while the resonant frequency changes due to the film contributions to the bending force and inertia of the cantilever. It is found that the relative variations of cantilever force constant and resonance frequency depend on the film to cantilever thickness, density and elasticity modulus ratios. This theoretical prediction is confirmed by the experimental investigations on mechanical properties of silicon cantilevers covered by diamond like carbon (DLC) and fluorocarbon thin films obtained by high power impulse magnetron sputtering depositions. Moreover, the effect of film depositions on the cantilever mechanical properties is used to determine the elasticity modulus and mass density of the deposited thin films.

Impact of Constrained Dual-Screw Anchorage on Holding Strength and the Resistance to Cyclic Loading in Anterior Spinal Deformity Surgery

Biomechanical in vitro laboratory study. To compare the biomechanical performance of 3 fixation concepts used for anterior instrumented scoliosis correction and fusion (AISF). AISF is an ideal estimate for selective fusion in adolescent idiopathic scoliosis. Correction is mediated using rods and screws anchored in the vertebral bodies. Application of large correction forces can promote early weakening of the implant-vertebra interfaces, with potential postoperative loss of correction, implant dislodgment, and nonunion. Therefore, improvement of screw-rod anchorage characteristics with AISF is valuable. A total of 111 thoracolumbar vertebrae harvested from 7 human spines completed a testing protocol. Age of specimens was 62.9 ± 8.2 years. Vertebrae were potted in polymethylmethacrylate and instrumented using 3 different devices with identical screw length and unicortical fixation: single constrained screw fixation (SC fixation), nonconstrained dual-screw fixation (DNS fixation), and constrained dual-screw fixation (DC fixation) resembling a novel implant type. Mechanical testing of each implant-vertebra unit using cyclic loading and pullout tests were performed after stress tests were applied mimicking surgical maneuvers during AISF. Test order was as follows: (1) preload test 1 simulating screw-rod locking and cantilever forces; (2) preload test 2 simulating compression/distraction maneuver; (3) cyclic loading tests with implant-vertebra unit subjected to stepwise increased cyclic loading (maximum: 200 N) protocol with 1000 cycles at 2 Hz, tests were aborted if displacement greater than 2 mm occurred before reaching 1000 cycles; and (4) coaxial pullout tests at a pullout rate of 5 mm/min. With each test, the mode of failure, that is, shear versus fracture, was noted as well as the ultimate load to failure (N), number of implant-vertebra units surpassing 1000 cycles, and number of cycles and related loads applied. Thirty-three percent of vertebrae surpassed 1000 cycles, 38% in the SC group, 19% in the DNS group, and 43% in the DC group. The difference between the DC group and the DNS group yielded significance (P = 0.04). For vertebrae not surpassing 1000 cycles, the number of cycles at implant displacement greater than 2 mm in the SC group was 648.7 ± 280.2 cycles, in the DNS group was 478.8 ± 219.0 cycles, and in the DC group was 699.5 ± 150.6 cycles. Differences between the SC group and the DNS group were significant (P = 0.008) as between the DC group and the DNS group (P = 0.0009). Load to failure in the SC group was 444.3 ± 302 N, in the DNS group was 527.7 ± 273 N, and in the DC group was 664.4 ± 371.5 N. The DC group outperformed the other constructs. The difference between the SC group and the DNS group failed significance (P = 0.25), whereas there was a significant difference between the SC group and the DC group (P = 0.003). The DC group showed a strong trend toward increased load to failure compared with the DNS group but without significance (P = 0.067). Surpassing 1000 cycles had a significant impact on the maximum load to failure in the SC group (P = 0.0001) and in the DNS group (P = 0.01) but not in the DC group (P = 0.2), which had the highest number of vertebrae surpassing 1000 cycles. Constrained dual-screw fixation characteristics in modern AISF implants can improve resistance to cyclic loading and pullout forces. DC constructs bear the potential to reduce the mechanical shortcomings of AISF.

Thick-film Load-sensing bridges – Effect of Temperature and Mechanical Boundary Conditions

Although inorganic thick-film materials are usually very stable, load sensors (i.e. force, torque and pressure) based on the piezoresistive effect of thick-film resistors often exhibit some drift, with major contributions stemming from a) temperature changes or gradients, coupled with the temperature coefficient of resistance (TCR) of the sensing bridge resistors, and b) ill- defined mechanical boundary conditions, due to insufficient decoupling, plastic deformation used materials, friction or loading errors. These problems also potentially affect test samples for measuring piezoresistive response, a.k.a. the gauge factors. Here, we examine and discuss effects on the output signal of simple cantilever force sensors of two disturbances: parasitic loads and temperature gradients, and discuss / demonstrate mitigation options, and a system to reliably measure gauge factor.

Spin coupling damp decay of force cantilever microscopy design based on Grover's algorithm magnetic resonance quantum computing

We displayed the nuclear spin coupling and dipole polarisation in magnetic resonance microscopy based on quantum calculation. When radio frequency (rf) probing operated nuclear spins on the nanometer localisation, Grover’s quantum algorithm can be realised by polarisation enhanced states using pulse sequence and width according to the interaction between RF and spins. We theoretically proposed two-qubits quantum system of density matrix to achieve quantum Grover’s algorithm in spin damp and frequency shift based on magnetic resonance microscopy. The nuclear spins were operated by pulse time sequences of cyclic adiabatic inversion, and controlled the quantum spin magnetic moment state to achieve the superposition. The resonance spins excited by radio frequency coil and magnetic tip were measured by the nuclear magnetic moment, spectrum and density matrix. The results indicated that the density matrix was used to read out quantum spectrum image. Grover’s algorithm can perform search faster than their classical counterparts. The force microscopy properties of spin damp decay holds great promise of magnetic resonance in quantum computing, quantum communication. Theoretically the algorithm is accelerated but not 100% in a rate of success.

Photothermal excitation of microcantilevers in liquid: effect of the excitation laser position on temperature and vibrational amplitude

Demands to improve the sensitivity and measurement speed of dynamic scanning force microscopy and cantilever sensing applications necessitate the development of smaller cantilever sensors. As a result, methods to directly drive cantilevers, such as photothermal or magnetic excitation, are gaining in importance. Presented is a report on the effect of photothermal excitation of microcantilevers on the increase in steady-state temperature and the dynamics of higher mode vibrations. First, the local temperature increase upon continuous irradiation with laser light at different positions along the cantilever was measured and compared with finite element analysis data. The temperature increase was highest when the heating laser was positioned at the free end of the cantilever. Next, the laser intensity was modulated to drive higher flexural modes to resonance. The dependence of the cantilever dynamics on the excitation laser position was assessed and was in good agreement with the analytical expressions. An optimal position to simultaneously excite all flexural modes of vibration with negligible heating was found at the clamped end of the cantilever. The reports findings are essential for optimisation of the excitation efficiency to minimise the rise in temperature and avoid damaging delicate samples or functionalisation layers.

Contractility of myofibrils from the heart and diaphragm muscles measured with atomic force cantilevers: Effects of heart-specific deletion of arginyl-tRNA–protein transferase

Contractile properties of myofibrils from the myocardium and diaphragm in chronic heart failure are not well understood. We investigated myofibrils in a knockout (KO) mouse model with cardiac-specific deletion of arginyl-tRNA-protein transferase (α-MHCAte1), which presents dilated cardiomyopathy and heart failure. The aim of this study was to test the hypothesis that chronic heart failure in α-MHCAte1 mice is associated with abnormal contractile properties of the heart and diaphragm. We used a newly developed system of atomic force cantilevers (AFC) to compare myofibrils from α-MHCAte1 and age-matched wild type mice (WT). Myofibrils from the myocardium and the diaphragm were attached to the AFC used for force measurements during activation/deactivation cycles at different sarcomere lengths. In the heart, α-MHCAte1 myofibrils presented a reduced force during full activation (89±9 nN/μm(2)) when compared to WT (132±11 nN/μm(2)), and the decrease was not influenced by sarcomere length. These myofibrils presented similar kinetics of force development (K(act)), redevelopment (K(tr)), and relaxation (K(rel)). In the diaphragm, α-MHCAte1 myofibrils presented an increased force during full activation (209±31 nN/μm(2)) when compared to WT (123±20 nN/μm(2)). Diaphragm myofibrils of α-MHCAte1 and WT presented similar K(act), but α-MHCAte1 myofibrils presented a faster K(rel) (6.11±0.41s(-1) vs 4.63±0.41 s(-1)). Contrary to our working hypothesis, diaphragm myofibrils from α-MHCAte1 mice produced an increased force compared to myofibrils from WT. These results suggest a potential compensatory mechanism by which the diaphragm works under loading conditions in the α-MHCAte1 chronic heart failure model.