Function Of Contact Force Research Articles

Experimental Study of Inconel 718 Surface Treatment by Edge Robotic Deburring with Force Control

We present the results of investigations into the application of robotics for deburring and chamfering to a predefined geometric quality. The robotic application was used for a part of the manufacturing process of an aircraft engine detail. Aircraft engine diffuser machining requires manual deburring of many edges. Finishing by hand results in several non-conforming quality details for each diffuser. This paper presents the concept of edge deburring with a controlled force progression pneumatic tool. A specific methodology was used to select and optimise the edge deburring process for robotic chamfering processing to a finer machining tolerance. The investigated machining process included a measurement system for the determination of the manufactured chamfer as a function of contact forces with feed force progression. The investigation work discussed in the paper helped to identify a specific interval of processing parameters, including the contact force and TCP motion velocity at which deburring is effective and a chamfer with specific geometric tolerance is produced. The experimental part of the investigation was conducted at a preset feed force of the high-speed machining file, tool ref. FDB150. The experimental machining sample was made from poorly machinable titanium alloy (Inconel 718), a material applied in the aerospace industry. The machining process optimisation included an approximation of the chamfer width definition points. The resulting function provided a derivative, defining the chamfer value change rate and corresponding to the actual machining tool infeed. The experimental measurement results were compared to the assumed quality indicators, by which a group of suboptimal parameters was defined.

P348Assessment of left atrial septal wall displacement and phrenic nerve pace capture as a function of contact force

P348Assessment of left atrial septal wall displacement and phrenic nerve pace capture as a function of contact force

Investigating the Behavior of Railway Short Panels Under Lateral Impact Loading: A Laboratory Study

A number of lateral impact tests were performed on two short panels with five and seven concrete sleepers, using a specific apparatus called pendulum loading test device (PLTD). In order to monitor the performance of panels under the exerted lateral impact loads, a comprehensive measurement setup was adopted for both panel and PLTD hammer. Subsequently, the contact force, inertia force and lateral displacement of each sleeper were recorded. The experimental results disclosed that a maximum number of five sleepers participated in the lateral load bearing process, each of which had the average contribution of 46, 17, 17, 11 and 9 % to the total lateral force. Moreover, it was revealed that 60 and 40 % of the total lateral resistance mobilized by the panel against lateral impact loads were provided by panel-ballast interaction and the panel inertia force, respectively. Furthermore, the dynamic lateral resistance (DLR) of panel, which is representative of the maximum panel-ballast interaction force, was found to be a function of contact force with a maximum value in the vicinity of 21 kN, and it was almost equal to its static lateral resistance (SLR).

Prolonged Intermittent Trunk Flexion Increases Trunk Muscles Reflex Gains and Trunk Stiffness.

The goal of the present study was to determine the effects of prolonged, intermittent flexion on trunk neuromuscular control. Furthermore, the potential beneficial effects of passive upper body support during flexion were investigated. Twenty one healthy young volunteers participated during two separate visits in which they performed 1 hour of intermittent 60 seconds flexion and 30 seconds rest cycles. Flexion was set at 80% lumbar flexion and was performed with or without upper body support. Before and after intermittent flexion exposure, lumbar range of motion was measured using inertial measurement units and trunk stability was assessed during perturbations applied in the forward direction with a force controlled actuator. Closed-loop system identification was used to determine the trunk translational admittance and reflexes as frequency response functions. The admittance describes the actuator displacement as a function of contact force and to assess reflexes muscle activation was related to actuator displacement. Trunk admittance gain decreased after unsupported flexion, while reflex gain and lumbar range of motion increased after both conditions. Significant interaction effects confirmed a larger increase in lumbar range of motion and reflex gains at most frequencies analysed following unsupported flexion in comparison to supported flexion, probably compensating for decreased passive tissue stiffness. In contrast with some previous studies we found that prolonged intermittent flexion decreased trunk admittance, which implies an increase of the lumped intrinsic and reflexive stiffness. This would compensate for decreased stiffness at the cost of an increase in cumulative low back load. Taking into account the differences between conditions it would be preferable to offer upper body support during activities that require prolonged trunk flexion.

Numerical simulation of contact force on bi-directional pig in gas pipeline: At the early stage of pigging

Periodic pigging of oil and gas pipelines for dewatering, cleaning and inspecting is a standard industry procedure. Predicting the motion of a pig to estimate its velocity, position and required driving pressure is essential before pigging. To enhance these predictions, the frictional force between pig and pipeline is a key determinant and insufficient understanding of the frictional force characteristics leads to significant inaccuracies. As the frictional force acting parallel to the pipeline wall plane is a function of contact force in the radial direction, a 2D axisymmetric nonlinear finite element model was proposed to predict the contact force experienced by bi-directional pig by using ANSYS. The impacts of four parameters (including interference, thickness, chamfer dimension and clamping rate of the sealing discs) on the contact force and the deflection angle of the sealing disc are studied at different differential pressures over the pig. Results obtained in this study shows that the thickness of the sealing disc has the greatest impact on contact force of the bi-directional pig, followed by the chamfer dimension, then the clamping rate and finally the interference. A linear relationship between the contact force and the differential pressure can also be observed from the results. Research findings on the characteristic of contact force and deflection angle of sealing disc may provide useful information for the formulation of theoretical or mathematical models to predict the frictional force on the pig, and pigging risks may be efficiently reduced by establish mitigating strategies on the basis of prediction.

Application of Hall Element as Tactile Sensor Device with Sensing Function of Contact Force and Temperature

Application of Hall Element as Tactile Sensor Device with Sensing Function of Contact Force and Temperature

Statistical Design of Experiment on Contact Secondary Nucleation as a Means of Creating Seed Crystals for Continuous Tubular Crystallizers

In the pharmaceutical industry, it is often desired to produce seed crystals with an appropriate narrow size distribution of the desired polymorph. This study describes a system that generates such crystals continuously in a small-scale tubular crystallizer at low supersaturation via contact secondary nucleation. A response surface model was constructed by conducting a statistical design of experiment that models the nucleation rate as a function of contact force, area, and frequency. This model reveals that within a certain range the nucleation rate is linearly related to all three factors in this system. A combination of in-line video analysis and off-line microscope image analysis was used to determine the particle size distribution of seed crystals obtained in this system, and the majority of the crystals were found to be under 20 μm. This seems to be a feature of contact secondary nuclei in general and does not vary significantly with contact force, area, and frequency. Furthermore, the seed crystals...

Structure and electrical properties of Nb-Ge-C nanocomposite coatings

Nb-Ge-C nanocomposite thin films were deposited by dc magnetron sputtering using three elemental targets. The films consist of substoichiometric NbCx in a nanometer-thick matrix of amorphous C and Ge. Films with no Ge contain grains that are elongated in the growth direction with a (111) preferred crystallographic orientation. With the addition of ∼12 at. % Ge, the grains are more equiaxed and exhibit a more random orientation. At even higher Ge contents, the structure also becomes denser. The porous structure of the low Ge content films result in O uptake from the ambient. With higher C content in the films both the amount of amorphous C and C/Nb-ratio increases. The contact resistance was measured by four-point technique as a function of contact force between 0 and 10 N. The lowest contact resistance (1.7 mΩ) is obtained at 10 N. The resistivity varies between 470 and 1700 μΩ·cm depending on porosity and O content.

Thermal cues and the perception of force

Two experiments were conducted to examine the effect of temperature on force perception. The objective of the first experiment was to quantify the change in skin temperature of the finger as a function of contact force, in order to characterize how much temperature changes under normal contact conditions. The decrease in temperature ranged from 2.3 to 4.2 degrees C as the force increased from 0.1 to 6 N, averaging 3.2 degrees C across the nine force levels studied. The changes in temperature as a function of force were well above threshold, which suggests that thermal cues could be used to discriminate between contact forces if other sources of sensory information were absent. The second experiment examined whether the perceived magnitude of forces (1-8 N) generated by the index finger changed as a function of the temperature of the contact surface against which the force was produced. A contralateral force-matching procedure was used to evaluate force perception. The results indicated that the perceived magnitude of finger forces did not change as a function of the temperature of the reference contact surface which varied from 22 to 38 degrees C. These results provide further support for the centrally generated theory of force perception and indicate that the thermal intensification of tactually perceived weight does not occur when forces are actively generated.

Single Asperity Chemical Mechanical Wear Studied by Atomic Force Microscopy

AbstractNanometer scale wear caused by a single asperity of silicon nitride was examined by measuring the wear caused by atomic force microscope tips translated against sodium trisilicate glass, soda-lime glass, or fused silica in aqueous solutions. As a function of contact force, FN, and scan duration, t, the wear to both tip and substrate scales approximately as (FNt)0.5. Substrate wear was independent of temperature from 5°C to 60°C, whereas tip wear showed a temperature dependence on soda-lime glass corresponding to an activation energy of 60 kJ/mol on soda-lime glass.

Study of contacts in an electrostatically actuated microswitch

Surface micromachined, electrostatically actuated microswitches have been developed at Northeastern University. Microswitches with gold contacts typically have an initial contact resistance of the order of 0.1 Ω over the first 10 5 cycles of lifetime while cold-switching 4 mA, and have a current handling capability of about 20 mA. In general, the contact resistance decreases over the first few thousand switch cycles, and degrades progressively when the switches are cycled beyond approximately 10 6 cycles. In this work, the microswitch contact resistance is studied on the basis of a clean metal contact resistance model. Comparison of the measured contact resistance (measured as a function of contact force) with the characteristics predicted by the model shows approximate agreement. The discrepancies between the model characteristics and measurements are discussed briefly.

Interparticle forces and displacements in granular materials

Abstract In a micromechanics framework, the main issue is the relationship between the microscale variables and the macroscale variables. These variables are used to describe either the statics or kinematics of the system. The relationships can be classified in two ways, namely, the “averaging” relationships and the “tracking” relationships. The averaging relationships express the macroscale variable as an averaging of the microscale variables; for example, the stress as a function of contact forces. The “tracking” relationships express the microscale variable as a function of the macroscale variables; for example, the contact force at a given orientation as a function of the stress. Based on fundamental premises, a unique averaging relationship exists for either the statics or the kinematics case. However, it is generally impossible to have a unique expression of the “tracking” relationship because they are generally derived with certain assumptions. In this paper, we will present expressions of the “tracking” based on three different approaches, namely, (1) energy conservation principle, (2) representation theory, and (3) indirect scheme. The assumptions used in each approach are discussed. The results are compared among the three approaches as well as that obtained from the Discrete Element Method (DEM).

Atomic layer wear of single-crystal calcite in aqueous solution using scanning force microscopy

Scanning force microscopy (SFM) is employed to study nm-scale wear of single-crystal calcite in an aqueous solution. When the SFM tip is drawn back and forth in a linear fashion across the edge of a preexisting single atomic layer etch pit, dissolution is strongly enhanced at the point where the tip crosses the step. The wear rate as a function of contact force is consistent with a thermally activated wear process, where the activation energy is locally reduced in the strain field of the SFM tip. The activation volume for the strain dependence is on the order of the average volume per ion in the CaCO3 lattice. This study provides further support for strain enhanced nucleation of double kinks along preexisting steps.

Atomic force microscopy for the study of tribology and adhesion

The recently developed atomic force microscope (AFM) 1 allows the study of the topography of insulating surfaces on an atomic scale. In this technique a tiny force sensor is raster-scanned across the surface and probes the interaction force between sample and sensor tip. In contrast to its predecessor, the profilometer, the vertical movement of the probe is monitored with sub-angstrom resolution. With the AFM, it is possible to study the friction between sample and probing tip as a function of contact force 2. Atomic-scale frictional effects are also present in the normal AFM imaging mode. Examples of images of highly oriented pyrolytic graphite (HOPG), a model substance for AFM, will be discussed. In addition to the observation of friction, a static non-imaging mode is described which gives information on adhesion forces between sample and tip and elastic properties of the sample surface. On a larger scale, the topography determined by AFM is of great utility in understanding the tribological properties of the sample. Here we present investigations on amorphous carbon layers similar to the materials used as tribological coatings. Variations in the surface topography of different samples might be related to a different behaviour in friction and wear.