Three-dimensional Load Research Articles

Design and Sensitivity Analysis Simulation of a Novel 3D Force Sensor Based on a Parallel Mechanism.

Automated force measurement is one of the most important technologies in realizing intelligent automation systems. However, while many methods are available for micro-force sensing, measuring large three-dimensional (3D) forces and loads remains a significant challenge. Accordingly, the present study proposes a novel 3D force sensor based on a parallel mechanism. The transformation function and sensitivity index of the proposed sensor are analytically derived. The simulation results show that the sensor has a larger effective measuring capability than traditional force sensors. Moreover, the sensor has a greater measurement sensitivity for horizontal forces than for vertical forces over most of the measurable force region. In other words, compared to traditional force sensors, the proposed sensor is more sensitive to shear forces than normal forces.

BEARING BOUNDARY ELEMENT METHOD BASED ON GEOMETRICALLY SIMILAR ROLLER CONDITIONS

To solve the three-dimensional pressure and load distribution of roller bearings, a new boundary element method (BEM) is presented in this report. First, a discrete model of the initial location roller was established, and the other rollers' discrete data could be obtained using geometrically similar conditions of this model. Based on the three-dimensional elastic contact BEM, all of the bearing rollers could be described as one object; therefore, the roller bearing problem of a multi-object contact system could be simplified as the problem of a three-object contact system. Bearing boundary elements were used to realize the discontinuous traction on the contact area, and the Hertz contact theory was used to revise the contact widths between the rollers and the bearing races, including the inner and outer races. A coupling matrix equation was established, and the boundary matrix equation's condensation process was illustrated. A bearing-BEM program was compiled based on geometrically similar roller conditions, in which a four-row tapered roller bearing in a rolling mill was simulated. The bearing contact pressure and load, roller contact widths and number of contact rollers were obtained. Lastly, the simulation result was compared with that of the traditional bearing-BEM (T-BBEM) and the experimental data, which proved the validity and effectiveness of the developed method.

Simulation of multi-stage nonlinear bone remodeling induced by fixed partial dentures of different configurations: a comparative clinical and numerical study.

This paper aimed to develop a clinically validated bone remodeling algorithm by integrating bone's dynamic properties in a multi-stage fashion based on a four-year clinical follow-up of implant treatment. The configurational effects of fixed partial dentures (FPDs) were explored using a multi-stage remodeling rule. Three-dimensional real-time occlusal loads during maximum voluntary clenching were measured with a piezoelectric force transducer and were incorporated into a computerized tomography-based finite element mandibular model. Virtual X-ray images were generated based on simulation and statistically correlated with clinical data using linear regressions. The strain energy density-driven remodeling parameters were regulated over the time frame considered. A linear single-stage bone remodeling algorithm, with a single set of constant remodeling parameters, was found to poorly fit with clinical data through linear regression (low [Formula: see text] and R), whereas a time-dependent multi-stage algorithm better simulated the remodeling process (high [Formula: see text] and R) against the clinical results. The three-implant-supported and distally cantilevered FPDs presented noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs showed bone resorption or no visible bone formation in some areas. Time-dependent variation of bone remodeling parameters is recommended to better correlate remodeling simulation with clinical follow-up. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodeling. Caution should be exercised when selecting the cantilever FPD due to the risk of overloading bone resorption.

Spine loading during the application and removal of lifting slings: the effects of patient weight, bed height and work method

The biomechanical loading on the lumbar spine was assessed as 12 female nurses applied and removed slings under two patients of differing weights (54 and 100 kg), using two work methods, and while working at three bed heights (56, 71, 93 cm). Three-dimensional spine loads at the L2/L3, L3/L4, L4/L5 and L5/S1 disc levels were measured using a validated EMG-assisted biomechanical model. Anterior/posterior (A/P) shear loading at the L5/S1 level consistently exceeded the tolerance threshold limit for disc failure. The peak compression values exceeded the 3400 N tolerance threshold for several participants when placing the sling under the 100-kg patient. In general, working from both sides of the bed generated slightly higher A/P shear loading than the one-sided method. Raising the bed significantly decreased compression and A/P shear forces. Therefore, raising the bed to at least the nurse’s knuckle height is recommended when applying and removing patient slings.Practitioners Summary: We investigated the spine loading associated with placing and removing slings used for the mechanised lifting of patients. Peak compression and anterior shear forces exceeded recognised thresholds when placing slings underneath heavier patients. Raising the bed to at least knuckle level helps mitigate these spinal loads.

Effects of Food Texture on Three-Dimensional Loads on Implants During Mastication Based on In Vivo Measurements.

The mechanisms by which the loads exerted on implants that support prostheses are modulated during mastication remain unclear. The purpose of this study was to evaluate the effects of food texture on 3-dimensional loads measured at a single implant using a piezoelectric transducer. Two subjects participated in this study. The transducer and the experimental superstructure, which had been adjusted to the subject's occlusal scheme, were attached to the implant with a titanium screw. The foods tested were chewing gum and peanuts. The mean maximum load on the implant in each chewing cycle was significantly higher during peanut chewing than during gum chewing. The direction of maximum load was significantly more widely dispersed during peanut chewing than during gum chewing. The range of changes in load direction during the force-increasing phase of each chewing cycle was significantly wider during peanut chewing than during gum chewing. The load on the implant was affected by food texture in both subjects. This measurement method can be useful to investigate the mechanisms of load modulation on implants during mastication.

Three-Dimensional Numerical Study of the Conical Nozzle Side Loads during Staging

AbstractThe objective of this paper is to numerically investigate the three-dimensional side loads and associated flow physics of a conical nozzle during the fire-in-the-hole staging event of the multistage rocket. The transient flow in nozzle is examined by a three-dimensional time-accurate numerical method with the start-up process of the upper-stage motor and the prescribed nominal separating motion of the lower stage. The impacts of asymmetric lateral motion due to non-nominal staging movement on the nozzle side loads are also numerically analyzed. These motion deviations include the relative angle between axes of two stages, relative lateral displacement between two stages, superposition of relative angle with relative lateral displacement, and angle of thrust vector control. As presented in the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage. With the location of shockwave reflection approaching the dome of lower stag...

PREDICTING THE WEAR OF SOFT-ON-HARD BEARING COUPLES FOR HUMAN HIP PROSTHESIS USING FINITE ELEMENT CONCEPTS

Wear of bearing couples is one of the major concerns in artificial hip implantation. To minimize the wear of hip bearing surfaces, several new materials have been introduced and tested including metal-on-metal, ceramic-on-ceramic and hard-on-hard combinations. The present study involves prediction of wear on ultra-high molecular weight polyethylene (UHMWPE) cup against Co–Cr, alumina and zirconia femoral head by applying the three-dimensional (3D) physiological loads as well as angular motions on these bearing couples to calculate the contact pressure using finite element concepts. The linear and volumetric wear of bearing surfaces increase with increase in gait cycles. Overall, the Zirconia–UHMWPE combination showed least wear, when compared with Alumina–UHMWPE and Co–Cr–UHMWPE combinations. The present study also revealed that the Zirconia–UHMWPE combinations showed less volumetric wear than the Alumina–Alumina bearing which is at present used in artificial hip resurfacements.

Influence of different loads on the stresses of multistage axial compressor rotors

Multistage axial compressors are widely used in the gas turbine engines. The strength of rotors is one of the key factors for the reliability of multistage axial compressors. The stresses of rotors at real working conditions can be caused by the centrifugal load, thermal load, and aerodynamic load. It is important to figure out the roles and the mechanism of the three kinds of loads in the stresses generating process. In this paper, the stresses of rotors in a typical five-stage axial compressor are calculated with different kinds of loads by solid–fluid coupling method. The results show that the proportion of the stress caused by centrifugal load is more than 80% of the total stress, which is dominant. The maximum proportion of the stress caused by thermal load is about 20% of the total stress at the front stages. However, the influence of thermal load is quite different from the first stage to the last stage. It is surprising that thermal load can decrease the stresses of the last stage rotor, which is mainly because of the variation of radial temperature gradient at disks for different stages. The proportion of the stress caused by aerodynamic load is usually less than 4%, and it tends to make the stresses at the suction side of the blades lower and enlarge it at the pressure side. According to the above results, centrifugal load is necessary of consideration at the conceptual design phase for the multistage axial compressor rotors. At preliminary three-dimensional design phase, centrifugal load and thermal load should be considered together. At optimized three-dimensional design phase, aerodynamic load cannot be neglected and all the three loads should be considered.

A mechanical pivot-shift device for continuously applying defined loads to cadaveric knees.

Current techniques to study the biomechanics of the pivot-shift utilize either static or poorly defined loading conditions. Here, a novel mechanical pivot-shift device that continuously applies well-defined loads to cadaveric knees is characterized and validated against the manual pivot-shift. Six fresh-frozen human lower limb specimens were potted at the femur, mounted on a hinged testing base, and fitted with the mechanical device. Five mechanical and manual pivot-shift tests were performed on each knee by two examiners before and after transecting the ACL. Three-dimensional kinematics (anterior and internal-rotary displacements, and posterior and external-rotary velocities) and kinetics (forces and moments applied to the tibia by the device) were recorded using an optical navigation system and 6-axis load cell. Analysis of variance and Bland-Altman statistics were used to gauge repeatability within knees, reproducibility between knees, agreement between the mechanical and manual test methods, and agreement between examiners. The forces and moments applied by the device were continuous and repeatable/reproducible to within 4/10% of maximum recorded values. Kinematic variables (excluding external-rotary velocity) were qualitatively and quantitatively similar to manual pivot-shift kinematics, and were more repeatable and reproducible. The presented device induces pivot-shift-like kinematics by applying highly repeatable three-dimensional loads to cadaver knees. It is based on a simple mechanical principle and designed using easily obtainable components. Consequently, the device enables orthopaedic biomechanists to easily and reliably quantify the effect of ACL injury and reconstruction on pivot-shift kinematics.

Dynamic Green׳s function for a three-dimensional concentrated load in the interior of a poroelastic layered half-space using a modified stiffness matrix method

This paper presents a new modified stiffness matrix method for the dynamic response analysis of a three-dimensional poroelastic layered half space subject to internal concentrated loads. This three-dimensional problem can be simplified as two two-dimensional problems consisting of the in-plane response and the anti-plane response. Similar to the principle of displacement method in structural mechanics, firstly, the top and bottom surfaces of a loaded layer are fixed, and the reaction forces at two “fixed ends” can be obtained using the superposition of the particular and homogeneous solution. Secondly, the displacement at the layer interface can be obtained using a direct stiffness method. In the loaded layer, the Green׳s function is decomposed into the particular solution, the homogeneous solution and the reaction solution, and the particular solution can be replaced by the analytical solution for the poroelastic full space. With this technique, the convergence problem due to the improper integral can be addressed with sources and receivers at similar or at the same depth, and a fictitious surface does not need to be introduced as in the traditional method. Finally, the results of the dynamic response of a poroelastic layered half space are presented both in the frequency and time domain.

Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures.

This study aimed to investigate the effect of attachment type on the load transmitted to implants and the residual ridge in a mandibular two-implant-supported overdenture in a model study. Ball attachments, locator attachments, and round-bar attachments were selected and examined. Static and dynamic vertical loads of 100 N were applied in the right first molar region. The load on the implants was measured by piezoelectric three-dimensional force transducers, and the load on the residual ridge beneath the denture base was measured using a tactile sheet sensor. The load on the implants with ball attachments was significantly higher than that with the other two attachments. The load on the residual ridge with round-bar attachments was significantly higher than that with the other two attachments. Our findings indicate that the three-dimensional load on implants and the residual ridge beneath the denture base is significantly associated with the type of attachment used in implant-supported overdentures.

Determination of the Thermal Load Distribution in Internal Traverse Grinding using a Geometric-Kinematic Simulation

During grinding processes, numerous grains interact with the workpiece material producing mechanical and thermal loads on the surface. In the field of thermal simulation of grinding processes, a widely used approach is to substitute numerous cutting edges by a single moving distributed heat source of a specific geometrical shape referring to the theory of Carslaw and Jaeger. This heat source is then moved across the modelled workpiece according to the specific kinematics of the grinding process.The geometrical shape of the substituted heat source can usually be determined using different approaches, e. g., predefined distribution functions or, more precisely, based on measurements of the shear stress within the contact zone. Referring to the state of the art, it is not possible to measure the shear stress within the contact zone during internal traverse grinding with roughing and finishing zone because of its very complex engagement conditions and the non-rectangular shape of its contact zone.In this work, a novel approach to determining a heat source distribution based on a geometric-kinematic simulation for internal traverse grinding is presented. This simulation identifies the ideal geometrical interaction of workpiece and grinding wheel. For this purpose, the specific material removal rate for each grain is calculated and accumulated with respect to the contact zone resulting in a three-dimensional thermal load distribution. This heat source can be used in finite element simulations to determine the thermal load on the workpiece.

On exact rod/beam/shaft-theories and the coupling among them due to arbitrary material anisotropies

We prove the existence of an exact one-dimensional representation of the three-dimensional theory of linear elasticity for a structural member with constant, two-fold symmetric cross-section, without the use of any a priori assumptions. We show that the general problem of three-dimensional elasticity decouples into four independent one-dimensional subproblems for isotropic material: a rod-, a shaft- and two orthogonal beam-problems. A unique decomposition of any three-dimensional load case with respect to the direction and the symmetries of the load is introduced. It allows us to identify each part of the decomposition as a driving force for one of the four one-dimensional subproblems. Furthermore, we show how the coupling behavior of the four subproblems can be derived directly from the sparsity scheme of the stiffness tensor for general anisotropic materials.

Numerical investigation of the spall opening angle of surface initiated rolling contact fatigue

The spall opening angle was studied for surface initiated rolling contact fatigue with the purpose to allow assessment of the volume of detached material. The influence of friction and the crack inclination angle on the damage spread in the contact surface was investigated with the asperity point load mechanism and a simplified three-dimensional rolling contact fatigue load. Crack arrest due to crack closure was proposed as explaining mechanism for the spall opening angle of the typical v-shaped or arrowhead crack configurations. A new three-dimensional crack geometry was presented allowing the study of the spalling surface morphology in a gear application. Stress intensity factors along the crack front were computed using the eXtended Finite Element Method (XFEM) implemented in Abaqus (6.12). Both low crack inclination angles and increased friction resulted in larger spall opening angles. For cracks with small inclination angles the effects of increased friction on the spall opening angle appeared however very little. The findings increase understanding of the surface morphology and the damage process and further motivate the asperity point load mechanism as an important source for surface initiated RCF damage.

Three-dimensional chiropractor-patient contact loads during side posture lumbar spinal manipulation: a pilot study

Abstract Background Patients with low back pain often seek chiropractic care and more than ninety percent of Chiropractors use lumbar side posture manipulation for the treatment of low back pain. During this procedure chiropractors deliver forces by means of hand contact on the patient in a side lying position. The objective of this pilot study was to report on the three-dimensional forces at the hand contact between the chiropractor and the simulated patient (asymptomatic volunteers) during side posture lumbar high velocity low amplitude adjustments. Methods In 2005, two licensed chiropractors delivered spinal manipulations to the lumbar spines of the participants. A three-dimensional force transducer (Model # Mini-45, ATI-Industrial Automation, Apex, North Carolina) was used to measure the three-dimensional loads. The force-time histories were analyzed for preloads, peak loads, duration of thrusts to peak load, duration of thrust for completion, rate of loading, and magnitudes of the three forces and the resultant total force delivered by the chiropractor. Results The two chiropractors delivered a total of 14 thrusts to the five asymptomatic volunteers. Normal force (Fz) is the dominating force, followed by inferior-superior force (Fx). The lateral force (Fy) occurred in both directions. Conclusions This study reports on the three dimensional load (three forces and the total resultant force) characteristics of chiropractor-patient hand contact while delivering a chiropractic high velocity low amplitude (HVLA) manipulation in a side lying position.

Predicting wear of ceramic–ceramic hip prosthesis using finite element method for different radial clearances

Hip replacement technique is widely used in replacing the femur head and acetabular cup by materials that are highly biocompatible. Such materials undergo surface wear due to post-operative activities that are experienced by the patients who undergo artificial hip replacement. Since wear is an important tribological phenomenon, it has to be minimised. Radial clearance plays a major role in lubricating the surface of materials which come into contact and also affects the wear rate considerably. In the present work, using three-dimensional (3D) physiological gait load for normal walking cycle as well as 3D rotation of ceramic femur head inside the ceramic cup, wear of bearing surfaces is calculated using finite element method for various radial clearance values. The simulation result is validated with the previous experimental observations, and they are found to be within the allowable range. Overall, the analysis revealed that there is a negligible change in volumetric wear rate, but the linear wear and contact pressure increases for higher radial clearances.

3차원 정적 집중하중을 받는 복합 탄성 케이블의 정적 해석

An elastic cable with piecewise constant properties under the action of concentrated static loads is studied analytically. Analytic solutions for catenary cables are combined at the discontinuous points caused by the discontinuous elastic properties or concentrated loads. The application of the boundary conditions at both ends of the multi-component cable results in three algebraic non-linear equations for three unknown parameters, which are determined numerically. The solutions for the shape, tension, elongation, and cross-sectional contraction of the cable are expressed in closed forms. Some examples are given for cases of two- and three-dimensional loads.

Status of the ITER full-tungsten divertor shaping and heat load distribution analysis

In September 2011, the ITER Organization (IO) proposed to begin operation with a full-tungsten (W) armoured divertor, with the objective of taking a decision on the final target material (carbon fibre composite or W) by the end of 2013. This period of 2 years would enable the development of a full-W divertor design compatible with nuclear operations, the investigation of further several physics R&D aspects associated with the use of W targets and the completion of technology qualification. Beginning with a brief overview of the reference heat load specifications which have been defined for the full-W engineering activity, this paper will report on the current status of the ITER divertor shaping and will summarize the results of related three-dimensional heat load distribution analysis performed as part of the design validation.

Fully Coupled Three-Dimensional Dynamic Response of a Tension-Leg Platform Floating Wind Turbine in Waves and Wind

A dynamic model for a tension-leg platform (TLP) floating offshore wind turbine is proposed. The model includes three-dimensional wind and wave loads and the associated structural response. The total system is formulated using 17 degrees of freedom (DOF), 6 for the platform motions and 11 for the wind turbine. Three-dimensional hydrodynamic loads have been formulated using a frequency- and direction-dependent spectrum. While wave loads are computed from the wave kinematics using Morison's equation, the aerodynamic loads are modeled by means of unsteady blade-element-momentum (BEM) theory, including Glauert correction for high values of the axial induction factor, dynamic stall, dynamic wake, and dynamic yaw. The aerodynamic model takes into account the wind shear and turbulence effects. For a representative geographical location, platform responses are obtained for a set of wind and wave climatic conditions. The platform responses show an influence from the aerodynamic loads, most clearly through quasi-steady mean surge and pitch responses associated with the mean wind. Further, the aerodynamic loads show an influence from the platform motion through a fluctuating rotor load contribution, which is a consequence of the wave-induced rotor dynamics. Loads and coupled responses are predicted for a set of load cases with different wave headings. Further, an advanced aero-elastic code, Flex5, is extended for the TLP wind turbine configuration and the response comparison with the simpler model shows a generally good agreement, except for the yaw motion. This deviation is found to be a result of the missing lateral tower flexibility in the simpler model.

Three-dimensional chiropractor-patient contact loads during side posture lumbar spinal manipulation: a pilot study

Patients with low back pain often seek chiropractic care and more than ninety percent of Chiropractors use lumbar side posture manipulation for the treatment of low back pain. During this procedure chiropractors deliver forces by means of hand contact on the patient in a side lying position. The objective of this pilot study was to report on the three-dimensional forces at the hand contact between the chiropractor and the simulated patient (asymptomatic volunteers) during side posture lumbar high velocity low amplitude adjustments. In 2005, two licensed chiropractors delivered spinal manipulations to the lumbar spines of the participants. A three-dimensional force transducer (Model # Mini-45, ATI-Industrial Automation, Apex, North Carolina) was used to measure the three-dimensional loads. The force-time histories were analyzed for preloads, peak loads, duration of thrusts to peak load, duration of thrust for completion, rate of loading, and magnitudes of the three forces and the resultant total force delivered by the chiropractor. The two chiropractors delivered a total of 14 thrusts to the five asymptomatic volunteers. Normal force (Fz) is the dominating force, followed by inferior-superior force (Fx). The lateral force (Fy) occurred in both directions. This study reports on the three dimensional load (three forces and the total resultant force) characteristics of chiropractor-patient hand contact while delivering a chiropractic high velocity low amplitude (HVLA) manipulation in a side lying position.