Fabrication and Characterization of Normal and Shear Stresses Sensitive Tactile Sensors by Using Inclined Micro-cantilevers Covered with Elastomer

2007 ◽  
Vol 1052 ◽  
Author(s):  
Masayuki Sohgawa ◽  
Yu-Ming Huang ◽  
Minoru Noda ◽  
Takeshi Kanashima ◽  
Kaoru Yamashita ◽  
...  
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Tactile Sensor ◽  
Shear Stresses ◽  
Tactile Sensors ◽  
Orthogonal Direction ◽  
Pdms Elastomer ◽  
Control Layer ◽  
Human Support

AbstractThe tactile sensors for human support robots which can detect both normal stress and shear stress and have human-friendly surface have been proposed. Micro-cantilevers adequately inclined by Cr deflection control layer were fabricated by the surface micromachining on SOI wafer. The cantilevers were covered with the PDMS elastomer for human-friendly surface. When the stress is added to the surface of elastomer, the deformation of cantilevers along with elastomer is detected as piezoresistive layer in the cantilevers. The piezoresistive response of the cantilever is analyzed by FEM calculation. The response of the fabricated tactile sensor to normal stress and shear stress was measured by output from this resistance. The tactile sensor with PDMS elastomer can detect both normal stress and shear stress. On the other hand, it hardly has sensitivity to shear stress of orthogonal direction to the cantilever. It means that the tactile sensor can distinguish the direction of shear stress. The sensitivity of tactile sensor vary widely with cantilever pattern and relation between direction of cantilever and crystallite orientation of Si. It is suggested that the sensitivity of tactile sensor can be improved by using FEM estimation and selective ion implantation.

scholarly journals A Distributed Tactile Sensor for Intuitive Human-Robot Interfacing

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Andrea Cirillo ◽  
Pasquale Cirillo ◽  
Giuseppe De Maria ◽  
Ciro Natale ◽  
Salvatore Pirozzi
Keyword(s):  
Control Strategies ◽  
Tactile Sensor ◽  
Human Machine Interface ◽  
Physical Interaction ◽  
Tactile Sensors ◽  
Recognition Algorithms ◽  
Machine Interface ◽  
Force Components ◽  
Human Robot Collaboration

Safety of human-robot physical interaction is enabled not only by suitable robot control strategies but also by suitable sensing technologies. For example, if distributed tactile sensors were available on the robot, they could be used not only to detect unintentional collisions, but also as human-machine interface by enabling a new mode of social interaction with the machine. Starting from their previous works, the authors developed a conformable distributed tactile sensor that can be easily conformed to the different parts of the robot body. Its ability to estimate contact force components and to provide a tactile map with an accurate spatial resolution enables the robot to handle both unintentional collisions in safe human-robot collaboration tasks and intentional touches where the sensor is used as human-machine interface. In this paper, the authors present the characterization of the proposed tactile sensor and they show how it can be also exploited to recognize haptic tactile gestures, by tailoring recognition algorithms, well known in the image processing field, to the case of tactile images. In particular, a set of haptic gestures has been defined to test three recognition algorithms on a group of 20 users. The paper demonstrates how the same sensor originally designed to manage unintentional collisions can be successfully used also as human-machine interface.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

AbstractAn experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τb, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τb and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τbVb. For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

Four-Wire Bridge Measurements of van der Pauw Stress Sensors on (100) and (111) Silicon

2013 ◽  
Author(s):  
Richard C. Jaeger ◽  
Mohammad Motalab ◽  
Safina Hussain ◽  
Jeffrey C. Suhling
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
Plane Shear ◽  
Plane Normal ◽  
Stress Sensors ◽  
Van Der Pauw ◽  
Contact Sensors

Four-wire resistance characterization of van der Pauw stress sensors is discussed. Under the proper orientations and excitations, the output of the four-contact sensors can be shown to depend upon only the in-plane shear stress or the in-plane normal stress difference on (100) silicon. The other stress terms are cancelled out by the symmetry of the structure, and the measurements are inherently temperature compensated. In bridge-mode, each sensor requires only one measurement and produces an output voltage that is directly proportional to the shear stress or in-plane normal stress difference, and the sensitivity is 3.16 times that of the equivalent resistor sensors, just as in the normal van der Pauw mode. Experimental, theoretical, finite-difference and finite-element and simulation results are presented demonstrating the behavior of the sensor. The two sensors can be merged into one eight-contact device, or n- and p-tye sensors can be overlaid in standard IC processes. Similar results apply to sensors on (111) silicon.

Numerical Study of Cruciform Specimens for Biaxial Tensile Tests

2016 ◽  
Author(s):  
Luis F. Puente Medellín ◽  
Antonio Balvantin ◽  
J. A. Diosdado-De la Peña
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Normal Stress ◽  
Sheet Metal ◽  
Numerical Study ◽  
Tensile Tests ◽  
Thickness Reduction ◽  
Shear Stresses ◽  
Normal Stress Distribution ◽  
Biaxial Tensile

This paper presents a numerical study of different geometries of cruciform specimens for biaxial tensile tests. The aim of these specimens is to be used on fixtures for biaxial tests mounted in universal testing machines. For the study, a model of isotropic material for steel sheet metal specimens was considered. Thus, only the mechanical properties of the sheet metal in the rolling direction were considered in the simulations. In this numerical analysis, the normal stress distribution and the consequent shear stress were studied. Additionally, the effect of the inclusion of multiple slots as well as a thickness reduction on the normal and shear stresses were assessed. Hence, a specimen in which a uniform normal stress distribution with zero shear stress, is necessary. The results of the analysis show that a specimen with features, multiple slots and a thickness reduction in the central area, provides a better performance in the simulations than dismissing any of these characteristics. Finally, a specimen model suitable for the mentioned test is proposed according to the obtained numerical results and the feasibility of manufacture of the experimental sample-test.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

Abstract An experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τ b, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τ b and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τ b Vb . For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

scholarly journals Numerical Analysis of Shear and Particle Crushing Characteristics in Ring Shear System Using the PFC2D

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 229
Author(s):  
Sueng-Won Jeong ◽  
Kabuyaya Kighuta ◽  
Dong-Eun Lee ◽  
Sung-Sik Park
Keyword(s):  
Shear Stress ◽  
Numerical Analysis ◽  
Normal Stress ◽  
Numerical Results ◽  
Particle Flow Code ◽  
Shear Stresses ◽  
Particle Crushing ◽  
Ring Shear ◽  
Peak Shear Stress ◽  
Residual Shear Stress

The shear and particle crushing characteristics of the failure plane (or shear surface) in catastrophic mass movements are examined with a ring shear apparatus, which is generally employed owing to its suitability for large deformations. Based on results of previous experiments on waste materials from abandoned mine deposits, we employed a simple numerical model based on ring shear testing using the particle flow code (PFC2D). We examined drainage, normal stress, and shear velocity dependent shear characteristics of landslide materials. For shear velocities of 0.1 and 100 mm/s and normal stress (NS) of 25 kPa, the numerical results are in good agreement with those obtained from experimental results. The difference between the experimental and numerical results of the residual shear stress was approximately 0.4 kPa for NS equal to 25 kPa and 0.9 kPa for NS equal to 100 kPa for both drained and undrained condition. In addition, we examined particle crushing effect during shearing using the frictional work concept in PFC. We calculated the work done by friction at both peak and residual shear stresses, and then used the results as crushing criteria in the numerical analysis. The frictional work at peak and the residual shear stresses was ranged from 303 kPa·s to 2579 kPa·s for given drainage and normal stress conditions. These results showed that clump particles were partially crushed at peak shear stress, and further particle crushing with respect to the production of finer in shearing was recorded at residual shear stress at the shearing plane.

scholarly journals Effect of Particle Shape on the Deformation and Stress Reduction of a Gravel Soil Due to Wetting

2021 ◽  
Author(s):  
Reza Mahinroosta ◽  
Vahid Oshtaghi
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Stress Reduction ◽  
Particle Shape ◽  
Shear Loading ◽  
Shear Stresses ◽  
Direct Shear ◽  
Gravelly Soil ◽  
Particle Shapes ◽  
Angular Particles

Abstract In this paper, the effect of particle shape is investigated on the stress reduction and collapse deformation of gravelly soil using medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. The Micro-Deval test was used to produce sub-angular particles from angular particles with continuous smoothening of the corners of the particles. Two series of soil specimens were obtained with the same rock type, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. For instance, dry soil specimens under several normal pressure were subjected to shear loading while inundated at several levels of shear stresses. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress level in both types of particle shapes, with higher values in angular particle shapes. The wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.

Effect of Residual Shear Stresses on Released Strains in Isotopic and Orthotropic Materials Measured by the Slitting Method

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Mahmood M. Shokrieh ◽  
Saeed Akbari R.
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Surface Strain ◽  
Strain Gauges ◽  
Orthotropic Materials ◽  
Back Surface ◽  
Shear Stresses ◽  
Plane Shear ◽  
Slitting Method ◽  
Out Of Plane

This paper investigates the effect of shear stresses on the determination of residual stresses in isotropic and orthotropic materials by the slitting method. A great deal of research effort is focused on the estimation of the residual stress component normal to the slit face using strain data measured by strain gauges installed on the top or the back surface of the stressed specimens. However, the slitting process will also release two in-plane and out-of-plane shear stress components, which may influence the measured strains. For the two specimens of carbon/epoxy and glass/epoxy laminated composites as well as a steel specimen, the distribution of released strains on the top and the back surfaces due to the shear stresses is calculated using finite element method and compared with those due to the residual normal stress. The results show that on the back surface, the shear stresses have a very small effect on the measured strains. However, on the top surface, strains due to the residual shear stresses are significant compared with those due to the residual normal stress and cannot be ignored. A method using two top surface strain gauges in both sides of the slit is presented to separate the effects of normal and shear stresses from each other. Also, strains due to the in-plane and the out-of-plane shear stresses could be isolated from each other. If these separations could be carried out successfully, the residual shear stress can be calculated by the proposed formulation.

Normal fluid stresses are prevalent in rotary ventricular assist devices: A computational fluid dynamics analysis

2018 ◽  
Vol 41 (11) ◽  
pp. 738-751 ◽  
Author(s):  
Dominica PY Khoo ◽  
Andrew N Cookson ◽  
Harinderjit S Gill ◽  
Katharine H Fraser
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Normal Stress ◽  
Ventricular Assist Devices ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Ventricular Assist ◽  
Assist Devices ◽  
Normal And Shear Stresses

Despite the evolution of ventricular assist devices, ventricular assist device patients still suffer from complications due to the damage to blood by fluid dynamic stress. Since rotary ventricular assist devices are assumed to exert mainly shear stress, studies of blood damage are based on shear flow experiments. However, measurements and simulations of cell and protein deformation show normal and shear stresses deform, and potentially damage, cells and proteins differently. The aim was to use computational fluid dynamics to assess the prevalence of normal stress, in comparison with shear stress, in rotary ventricular assist devices. Our calculations showed normal stresses do occur in rotary ventricular assist devices: the fluid volumes experiencing normal stress above 10 Pa were 0.011 mL (0.092%) and 0.027 mL (0.39%) for the HeartWare HVAD and HeartMate II (HMII), and normal stresses over 100 Pa were present. However, the shear stress volumes were up to two orders of magnitude larger than the normal stress volumes. Considering thresholds for red blood cell and von Willebrand factor deformation by normal and shear stresses, the fluid volumes causing deformation by normal stress were between 2.5 and 5 times the size of those causing deformation by shear stress. The exposure times to the individual normal stress deformation regions were around 1 ms. The results clearly show, for the first time, that while blood within rotary ventricular assist devices experiences more shear stress at much higher magnitudes as compared with normal stress, there is sufficient normal stress exposure present to cause deformation of, and potentially damage to, the blood components. This study is the first to quantify the fluid stress components in real blood contacting devices.

scholarly journals Ice At Melting Point Sliding Over A Pebble Slab–A Film

1979 ◽  
Vol 23 (89) ◽  
pp. 411
Author(s):  
W. F. Budd ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Graphite Particle ◽  
Time Lapse ◽  
Shear Stresses ◽  
Cold Room ◽  
Set Up ◽  
High Normal Stress ◽  
Dial Gauge ◽  
Movie Camera

Abstract A time-lapse movie technique has been developed to study processes taking place near the interface when ice under high normal stress slides over a rough slab for shear stresses and sliding velocities comparable to those of real glaciers. The “sledge rig” described by Budd and others (1979) was set up with one of the strips of ice (160 mm long and 23 mm wide) close to the edge of the pebble slab on which it rested. The normal stress was applied by loading the rig with lead to 5 bars. The shear stress was applied by a direct load on a cable over a pulley while the rig rested on the slab on a strong table. Shear stresses in the range 1 to 2 bars were used giving velocities from about 50 to 500 m a–1. Beyond 2 bars it was found that acceleration would set in, so this was avoided. A time-lapse movie camera was set up beside the rig to focus first on the whole configuration and then on the ice and interface as a close-up. A flash light was set up behind the rig to shine through the ice strip. A scale rule was placed along the slab under the ice strip. A dial-gauge micrometer was also used to monitor displacement. A time-lapse frequency of about 1 frame per 8 s was found to give a suitable speed. An automatic control triggered the camera and flash and also recorded the number of frames. A number of different markings were tried on the ice to indicate the relative ice deformation. Small graphite particle tracers were found the most successful. A number of runs have been filmed showing the ice sliding speed increasing with increasing shear stress. The tests were carried out in a cold room at a temperature close to 0°C. Copies of the film can be made available at cost. The authors were greatly assisted by Mr David Gardner of the Department of Educational Technology of Melbourne University by the provision of the filming equipment and general support for the operation.

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