Rotational Slip Research Articles

Behavior of strengthened reinforced concrete coupling beams by bolted steel plates, Part 2: Evaluation of theoretical strength

Composite beams using bolts to attach steel plates to the side faces of existing reinforced concrete (RC) coupling beams can enhance both their strength and deformability. The behavior of those composite beams differs substantially from the behavior of typical composite beams made up of steel beams and concrete slabs. The former are subjected to longitudinal, vertical and rotational slips, while the latter only involve longitudinal slip. In this study, a mixed analysis method was adopted to develop the fundamental equations for accurate prediction of the load-carrying capacity of steel plate strengthened RC coupling beams. Then, a rigid plastic analysis technique was used to cope with the full composite effect of the bolt group connections. Two theoretical models for the determination of the strength of medium-length plate strengthened coupling beams based on mixed analysis and rigid plastic methods are presented. The strength of the strengthened coupling beams is derived. The vertical and longitudinal slips of the steel plates and the shear strength of the anchor-bolt connection group is considered. The theoretical models are validated by the available experimental results presented in a companion paper. The strength of the specimens predicted from the mixed analysis model is found to be in good agreement with that from the experimental results.

Relationship between ⟨111⟩ Rotation Recrystallization Mechanism and Slip Bands with Compressive Strains during Tensile Deformation in Aluminum Single Crystals

Relationship between ⟨111⟩ Rotation Recrystallization Mechanism and Slip Bands with Compressive Strains during Tensile Deformation in Aluminum Single Crystals

MACRO- AND MICROSCOPIC APPROACHES TO PLANE STRAIN DEFORMATION STATES OF FACE-CENTERED CUBIC METALS UNDER WEDGE INDENTATION

Face-centered cubic (FCC) metals show active slip under indentation loading. In this work, both macro- and microscopic models are proposed to analyze the deformation behavior of face-centered-cubic (FCC) single crystals under wedge indentation. In the part of macroscopic approach, stress distribution and anisotropic yielding were investigated. Load-displacement relation was obtained to reveal the mechanical responses of the crystals. In the microscopic approach section, an indention induced lattice rotation zone was identified and the deformation behavior was analyzed using the single crystal plasticity theory. The crystal lattice rotation experimental results and slip line trace observations validate the analytical predictions.

Analysis of fluid flow and heat transfer in coolant ducts of friction clutches

AbstractThis paper deals with the numerical simulation of the fluid flow in coolant ducts as wall as the calculation of temperature field in fluid and solid of a friction clutch. The simulations are carried out by means of commercial software based on a finite volume method in a relative framework, where the fluid flow is not time dependent. The results in dependence of rotation speed and slip velocity show interesting secondary flow in the ducts. Different flow pattern have distinct influence on the temperature field and the heat transfer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Orientation and structure development in poly(lactide) under uniaxial deformation

Semicrystalline poly( l-lactide), or PLLA, is used in many biomedical applications, including self-expanding stents. A network model is applied to describe the deformation behaviour of semicrystalline poly( l-lactide) obtained at different drawing temperatures. Based on the present results, it is suggested that the deformation behaviour of PLLA appears to follow pseudo-affine model at the macroscopic level, but it does not follow it at the molecular level. The development of molecular orientation during drawing in both crystalline and amorphous phases was characterized by means of optical birefringence and wide-angle X-ray diffraction (WAXD). In general, high orientation is achieved at the higher drawing temperature and it is found that the crystalline and amorphous phases respond differently to network deformation. At moderate deformation temperature, the development of crystalline orientation increases slowly at a low stretch ratio followed by a rapid rise in the degree of orientation as a result of crystal rotation and crystal slip, while the amorphous chains deform in pseudo-affine manner. Drawing at a high temperature shows rapid crystalline orientation development, even at a low stretch ratio of 1.5, while molecular alignment develops steadily in the amorphous phase.

Nonlinear variations of the physical properties along the southern Ecuador subduction channel: Results from depth-migrated seismic data

We use two high-quality pre-stack depth-migrated multichannel seismic profiles acquired to quantify physical properties variations of underthrust sediments along the first ~ 30 km of subduction off the erosional southern Ecuadorian margin. Seismic data show three zones along the subduction channel (referred to as Zones I, II and III) characterized by distinct velocity and velocity-derived physical properties, which are in agreement with values estimated from experimental results of deformation in granular media. These three zones result from transformational changes of underthrust sediments governed by fundamentally different physical processes that control their mechanical behavior at increasing confining pressures. Based on our observations and its comparison with experimental results, we argue that the transformations undergone by underthrust sediments as they dip into the subduction zone are the following: within Zone I, progressively increasing velocity (and decreasing velocity-derived porosity) indicates continuous sediment compaction, which must be accompanied by effective fluid drainage along the décollement and/or across the accretionary wedge. The underthrust material is here unconsolidated from a mechanical point of view. Laboratory experiments indicate that the dominant processes at this range of pressures are grain rolling, particle rotation and frictional slip at grain contacts. Within Zone II, velocity (and porosity) remains constant for ~ 16 km (SIS-72) and ~ 12 km (SIS-18). This suggests undrained conditions resulting in growing fluid overpressure at the subduction channel. Grain deformation is similar to Zone I. Within Zone III, velocity increases and porosity falls rapidly, indicating sediment compaction and subsequent release of over-pressured fluids, where grain deformation is likely to be elastic. This might be the dominant process until the grains attain their crushing strength, resulting in granular cataclasis and, eventually, in the collapse of the system. We suggest that over-pressured fluid release may induce hydrofracturation and it is likely to increase inter-plate coupling down from Zone III.

Evaluating the effects of the magnitude and amplification of pseudo-static acceleration on reinforced soil slopes and walls using the limit equilibrium Horizontal Slices Method

The effects of horizontal and vertical pseudo-static forces on reinforced soil structures are investigated in the paper. In particular, the effects of the magnitude and amplification of the ground acceleration on the seismic stability of reinforced soil slopes and walls have been investigated using the Horizontal Slices Method (HSM). The HSM is a limit equilibrium method for the analysis of reinforced soil structures, which offers a number of benefits over conventional vertical slice methods. First, a parametric study using acceptable geotechnical, geometrical and design parameters was undertaken. The results of the parametric analysis are presented in dimensionless form relating to the force required to maintain stability of the slope ( K) and the required length of the reinforcements ( L c/ H). Different rotational and planar slip surfaces are shown for various slopes and walls with different geotechnical strength parameters. Second, the capability of the HSM to consider the effect of earthquake amplification on the stability analysis of reinforced soil structures was considered. It has been shown that the effect of horizontal seismic acceleration on the response of reinforced slopes and walls depends mainly on the geotechnical strength parameters. The effect of vertical seismic acceleration on the performance of reinforced slopes is not significant for low values of horizontal seismic acceleration. It has been concluded that ignoring the effect of the amplification phenomenon could result in an underestimated design.

Using a structural approach to identify relationships between soil and erosion in a semi-humid forested area, South India

Biogeochemical and hydrological cycles are currently studied on a small experimental forested watershed (4.5 km 2) in the semi-humid South India. This paper presents one of the first data referring to the distribution and dynamics of a widespread red soil (Ferralsols and Chromic Luvisols) and black soil (Vertisols and Vertic intergrades) cover, and its possible relationship with the recent development of the erosion process. The soil map was established from the observation of isolated soil profiles and toposequences, and surveys of soil electromagnetic conductivity (EM31, Geonics Ltd), lithology and vegetation. The distribution of the different parts of the soil cover in relation to each other was used to establish the dynamics and chronological order of formation. Results indicate that both topography and lithology (gneiss and amphibolite) have influenced the distribution of the soils. At the downslope, the following parts of the soil covers were distinguished: i) red soil system, ii) black soil system, iii) bleached horizon at the top of the black soil and iv) bleached sandy saprolite at the base of the black soil. The red soil is currently transforming into black soil and the transformation front is moving upslope. In the bottom part of the slope, the chronology appears to be the following: black soil > bleached horizon at the top of the black soil > streambed > bleached horizon below the black soil. It appears that the development of the drainage network is a recent process, which was guided by the presence of thin black soil with a vertic horizon less than 2 m deep. Three distinctive types of erosional landforms have been identified: 1. rotational slips (Type 1); 2. a seepage erosion (Type 2) at the top of the black soil profile; 3. A combination of earthflow and sliding in the non-cohesive saprolite of the gneiss occurs at midslope (Type 3). Types 1 and 2 erosion are mainly occurring downslope and are always located at the intersection between the streambed and the red soil-black soil contact. Neutron probe monitoring, along an area vulnerable to erosion types 1 and 2, indicates that rotational slips are caused by a temporary watertable at the base of the black soil and within the sandy bleached saprolite, which behaves as a plane of weakness. The watertable is induced by the ephemeral watercourse. Erosion type 2 is caused by seepage of a perched watertable, which occurs after swelling and closing of the cracks of the vertic clay horizon and within a light textured and bleached horizon at the top of black soil. Type 3 erosion is not related to the red soil–black soil system but is caused by the seasonal seepage of saturated throughflow in the sandy saprolite of the gneiss occurring at midslope.

Characterizing and producing from reservoirs in landslides: challenges and opportunities

Abstract Landslides can consist of rotational slips, translational glide blocks, topples, talus slopes, debris flows, mudslides and compressional toes which can combine in different proportions to form complex landslides. The mass movement can be subaerial or submarine, occur over wide ranges of scale and can vary in rate from creep to catastrophic failure. Complexity of the landslide reflects the controlling factors including the strength of the deforming material and triggering mechanisms such as earthquakes, imposed load, increasing topographic relief and removal of toe material. Processes of landslide deformation include slip on discrete surfaces, distributed shear within the landslide, vertical thinning and lateral spreading through shear, fluidization, porosity collapse and loss of material from the top or toe of the complex. These processes control the quality of the resultant reservoirs. This leads to a greater range of reservoir types than conventional faulted reservoirs, with a proportionate upside and downside potential and difficulty in quantifying uncertainty. This paper uses examples from the literature, outcrops and subsurface datasets (including the Statfjord Field and the Halten Terrace in Norway) to outline the complexity of reservoirs in landslides and the challenges and opportunities in finding and producing them. We present workflows for seismic and subseismic characterization for exploration and reservoir scale based on geomorphological principles. Seismic mapping is achieved by classifying the form of the reflectors (both slip surfaces and the bounding envelope of the landslide) from an atlas of geometric and structural styles and is applied to both the Halten Terrace example and the Statfjord Field. We present a new workflow for reservoir characterization in which integration of structural, biostratigraphic, sedimentological and dynamic data gives key information on process, timing and heterogeneity of the reservoir. For the Statfjord field, important maps of the landslide block stratigraphy derived from a subcrop map and communication maps based on a c . 130 well dataset can be correlated to outcrop analogues and used to develop a predictive tool for landslide reservoir extent and quality, both in this field and others.

Stability of Spoil Piles at Two Coal Mines in Turkey: Geotechnical Characterization and Design Considerations

One of the major problems in surface mining of coal is the stability of disposed overburden materials. Geotechnical considerations are thus very important in rational planning for disposal, reclamation, treatment, and utilization of mine waste material. The subject of this study is the stability of spoil piles at open pit coal mines located in the Central Anatolia, Turkey. The coal is produced from two adjacent open pits. While a large portion of the spoil piles dumped at the Central Pit has experienced slope failure, no spoil pile instability has been experienced at the South Pit. This article outlines the results of field and laboratory investigations to describe the mechanism of the spoil pile failure in the Central Pit and the geotechnical design considerations for the spoil piles at the South Pit based on the experience gained from the previous spoil failures. Limit equilibrium analysis carried out for the large-scale spoil failure indicated that deep-seated sliding along the interface between underclay and dragline spoil piles and rotational slip through the overburden spoil material may be all occurring simultaneously as water migrates through these areas. Sensitivity analyses revealed that spoil pile instability is not expected at the South Pit when the currentmore » spoil placement method is used as long as the generation of high water pressures in the spoil piles is not permitted. Comparisons between the results of finite element analysis and long-term monitoring data also confirmed the results of sensitivity analyses and indicated a vertical deformation associated with compaction of the spoil material.« less

Molecular Orientation Distributions in Uniaxially Oriented Poly(l-lactic acid) Films Determined by Polarized Raman Spectroscopy

Molecular orientation distributions in the crystalline and amorphous regions were studied for uniaxially oriented poly(l-lactic acid) (PLLA) films using polarized Raman spectroscopy. By combining wide-angle X-ray diffraction and birefringence measurements, the tilt angle between the principal axis of the Raman tensor and the molecular chain axis was determined for Raman bands assigned to the crystalline regions only, and also to those being independent of morphology. The changes of the molecular orientation distribution functions during the drawing were analyzed in detail. The PLLA molecules in the crystalline regions were found to be highly oriented at a draw ratio of 4.5, probably as a result of crystal rotation and crystal slip. In contrast, the development of molecular orientation in the amorphous regions appeared to take place by pseudo-affine deformation. The results suggest that the film needs to be stretched to draw ratios above 4.5 to achieve successful molecular orientation in the amorphous regions.

Geological study for the southern plain of alan, north of iraq using geoelectrical sounding

The present research involves geoelectrical study of the southern allan's plain, which lies between allan and atshan anticlines, in the north of Iraq. The field measurements were carried out in sixty three sounding stations, using collinear and symmetrical schlumberger array, distributed on four traverses (NE-SW direction) across the axes of anticlines surrounding the study area. The maximum interval spacing between both current and potential electrode has reached 843 and 90 meters consequently. The final interpretation result were represented with four geoelectrical section. Continuous correlation with composite stratigraphic columns of surrounding anticlines was made and five electrical zones were distinguished reflecting the soil, quaternary deposits upper and lower members of Al-Fat'ha formation as well as Euphrates formation. This study has specified two strike slip faults affected by the alpine orogeny. One transversal fault with NE-SW direction is located and clearly affects the true resistivity data and the anticlinal structure plunges in the east of the currently studying area. In addition a rotational strike slip fault has been specified, extending E-W parallel to the axes of the anticlines surrounding the area the second fault is considered as an important tectonic element in the regional geology of the north of Iraq, this element divides between the northern and the southern blocks of Mosul, which is characterized by the existence of Taurus and zagros trends consequently.

Slipped capital femoral epiphysis

This particular ailment has many designations in the literature but none is quite adequate. Here we use the terminology slipped capital femoral epiphysis (SCFE). The anatomy of the proximal femur in all mammals reflects their growth and function. The main forces acting on the head are perpendicular to the growth plate. The thick tear‐proof perichondrium‐periosteum on the femoral neck is like a stocking attached to the epiphysis and the trochanter region. Growth in length causes a strong tensile stress in the periosteum, pressing the epiphysis against the metaphysis and thus stabilizing the vulnerable growth plate—the periosteum theory. Several factors may diminish the stability of the growth plate. SCFE begins with fissures, which coalesce to a fracture in the growth plate, invisible on a radiograph. As the slip progresses, an increasing angulation between the epiphysis and the remainder of the femur occurs. Weight and muscular forces displace the epiphysis posteriorly in a flexed hip. A rift in the ventral half of the periosteal stocking occurs at the border to the perichondrium and, after that, a longitudinal rift in the periosteum at the anterior midline of the femoral neck. This rift becomes broader as the epiphysis slips posteriorly, withdrawing the ruptured periosteum. Displacement of the epiphysis is due to a rotational slip and tilt, made possible by a compression fracture in the posterior part of the metaphysis. Parts of the periosteum function as reins steering the slip direction and counteracting the displacement. SCFE may be regarded as a pseudoarthrosis in the growing cartilage of the plate. The periosteum theory extended to a pseudoarthrosis theory has been supported by findings at surgery and on true lateral radiographs of usual and unusual cases of SCFE presented in this opus. On a true lateral view, the displacement can be measured as the slipping angle (SA) based on anatomical and geometrical considerations. SA values from 95 normal hips and from 22 contralateral asymptomatic hips from SCFE patients are presented in a histogram and bar graph. Statistically, SCFE is always bilateral, but in about 1/3 of the asymptomatic, contralateral hips, the physis ossifies and closes with SA below 13°, and surgery is not necessary. It is most important that the position of the femur on the X‐ray table is exactly defined in two dimensions: 1) the angle between the femoral shaft and the tabletop (angle of elevation), 2) the degree of rotation of the femur around its axis. A precisely defined positioning of the femur is a prerequisite for an exact reproducible measurement of the SA on a true lateral view and is also valuable for the evaluation of radiographic “signs”. An aid, the Youth Hip Triangle (YHT), has been designed to facilitate positioning of the femur and measurement of SA. YHT is recommended for routine use in every X‐ray facility. The method is quick, cost effective and makes it possible to diagnose SCFE in the contralateral hip before clinical signs or symptoms have occurred.

A joint analysis of GPS motions and InSAR to infer the coseismic surface deformation of the Izmit, Turkey earthquake

SUMMARY From a joint analysis of GPS and InSAR data we have determined the kinematic coseismic surface deformation of the 1999 August 17, Izmit (Turkey) earthquake in terms of strain, rotation and fault slip. The fault slip contribution shows two distinct peaks: one of ∼4 m of slip at Golcuk, and a second of ∼2.9 m slip near Sapanca Lake. The strain field portrays four distinct quadrants reflecting the earthquake focal mechanism. The transition between the quadrants is not centred on the epicentre of the event, but shifted eastwards north of the fault and westwards south of the fault. This shift is the result of a two-stage source rupture process caused by the step-over features in the fault geometry. This rupture process also induced a distinct asymmetry in the displacement field across the fault. We obtain left-lateral shear strains along the Sakarya segment that is the result of a subsequent source nucleating at the Akyazi Gap inducing failure on the easternmost segments. Strong interaction is also observed from a consecutive source near Hersek. Finally, we deduce that the Izmit earthquake has released most of the strain that has accmulated since the last main event on this stretch of the North Anatolian fault in 1719.

Constrained shearing of a thin crystalline strip: Application of a continuum dislocation-based model

The problem of simple shearing of a constrained thin crystalline strip posed by Shu et al. [J. Mech. Phys. Solids 49, 1361 (2001)] is reanalyzed using a nonlocal continuum dislocation-based model of plastic deformation that accounts for the flexibility of curved dislocations carrying the plastic deformation. Attention is paid to the inhomogeneous profiles of plastic slip and lattice rotation as well as to the size-dependent material response of the strip in single slip and symmetric double slip. Additional boundary conditions and an internal length scale with a clear physical interpretation appear quite naturally in the analysis.

Quantitative Characterization of Dislocation Structure coupled with Electromigration in a Passivated Al (0.5wt%Cu) Interconnects

AbstractNew synchrotron x-ray microbeam methodology is used to analyze and test the reliability of interconnects. The early stage of plastic deformation induced by electromigration before any damages become visible has been recently revealed by white beam scanning X-ray microdiffraction during an accelerated test on Al interconnect lines. In the present paper, we provide a quantitative analysis of the dislocation structure generated in several micron-sized Al grains in both the middle region and ends of the interconnect line during anin-situelectromigration experiment. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of randomly distributed geometrically necessary dislocations as well as geometrically necessary boundaries. The orientation of the activated slip systems and rotation axis depends on the position of the grain in the interconnect line. The origin of the observed plastic deformation is considered in view of constraints for dislocation arrangements under applied electric field during electromigration. The coupling between plastic deformation and precipitation in the Al (0.5% wt. Cu) is observed for the grains close to the anode/cathode end of the line.

Study concerning the effect of wheel center trajectory angle on harshness vibration

Harshness vibration can be reduced by modifying the side-view inclination angle of the wheel center trajectory, but the dynamic mechanism involved is not clearly understood. The mechanism is explained here by formulating it with equations of motion and verifying it by comparing the numerical simulation results with experimental data. It is shown that the force generated by tire rotational slip should be considered. An analytical study was made of the relationship between suspension specifications and the optimal inclination angle of the wheel center trajectory for minimizing harshness vibration.

Characteristic relations for a model for the flow of granular materials

A model for the flow of granular materials is considered which is based upon the physical and kinematic concepts of yield on a slip surface, a shearing motion across the slip surface, dilatation or contraction normal to the slip surface and rotation of the slip surface. The equations governing the model are presented in both tensorial and Cartesian equation form. For planar deformations a full analysis of the characteristic directions is carried out. The characteristic equation is a sextic polynomial with five distinct real roots defining a pair of velocity characteristic directions, a pair of stress characteristic directions and a direction associated with both the continuity equation and the slip rotation. Using the characteristic directions to define characteristic coordinates, the equations governing the model relative to these characteristic coordinates are presented. An application of the model to chute flow is considered.

Signatures of granular microstructure in dense shear flows

Granular materials and ordinary fluids react differently to shear stresses. Rather than deforming uniformly, materials such as dry sand or cohesionless powders develop shear bands--narrow zones of large relative particle motion, with essentially rigid adjacent regions. Because shear bands mark areas of flow, material failure and energy dissipation, they are important in many industrial, civil engineering and geophysical processes. They are also relevant to lubricating fluids confined to ultrathin molecular layers. However, detailed three-dimensional information on motion within a shear band, including the degree of particle rotation and interparticle slip, is lacking. Similarly, very little is known about how the microstructure of individual grains affects movement in densely packed material. Here we combine magnetic resonance imaging, X-ray tomography and high-speed-video particle tracking to obtain the local steady-state particle velocity, rotation and packing density for shear flow in a three-dimensional Couette geometry. We find that key characteristics of the granular microstructure determine the shape of the velocity profile.

Translational and rotational slip detection and control in robotic manipulation

In this paper, some results concerning the detection and control of the relative motion (slippage) of two bodies in contact are presented. Main motivation of this research can be found in advanced manipulation with robotic systems, in which, depending on the particular task to be executed, it might be desirable either to avoid or to exploit the slippage of the manipulated object. Main contribution of this paper is that, besides the linear Coulomb friction effect (and therefore translational motions), also the rotational case is addressed. Experimental results are presented considering both the detection of the motion (slippage) and its subsequent control.