Lateral Constrain Research Articles

Fine Detection and Analysis of Hidden Karst in Wellsite with Quasi-Three-Dimensional TDEM Based on Lateral Constraint

Considering that karst caves, underground rivers, and dissolution fractures in shallow carbonate formation in the Sichuan Basin are extremely developed, leakage, failure and plugging difficulties are easy to occur in the drilling process. The TDEM was used to carry out the exploration of hidden karst geological bodies in well QM2, and the quasi-three-dimensional inversion based on lateral constrain was used to invert the TDEM data. Three NW trending anomalous bands were identified in the lower Triassic Jialingjiang Formation within the range of drilling, consisting of seven relatively low-resistivity anomalous zones. Under the guidance of TDEM quasi-three-dimensional inversion resistivity data, the low-resistivity karst development area is avoided, and the specific drilling location of well QM2 is determined. No karst cave and underground river were drilled in the later drilling process of well QM2, as well as no instability phenomenon occurred. It indicates that the TDEM detection results are consistent with the actual drilling, and the quasi-three-dimensional TDEM inversion interpretation data based on lateral constraints is reliable and can accurately detect the buried karst in the wellsite.

Numerical modelling of a catamaran float-over deck installation for a spar platform with complex hydrodynamic interactions and mechanical couplings

Multi-body system is becoming common in engineering practice, such as the catamaran float-over installation for a Spar platform, one of the most complex marine systems. Gap resonance phenomenon occurs in the catamaran float-over system due to strong hydrodynamic interactions, inducing inaccuracy in evaluations of the hydrodynamic coefficients. To obtain reasonable hydrodynamic coefficients, the damping lid method in AQWA, which provide viscous correction for the potential flow theory, is first validated and then applied to the model in this study. It is found that the damping lid is capable of dealing with the gap resonance phenomenon. With the introduction of the damp lid method in the catamaran float-over system with α = 0.20, the relative error between frequency-domain and time-domain declined from 690% to 1.7%. Based on the corrected frequency-domain results, a time-domain model, considering various types of mechanical coupling components in the float-over system, including LMUs, DSUs, steel-to-steel impacts on LMUs, lateral constrains of LMUs and DSUs, sway fenders, hawsers and the mooring system. Simulations for first contact stage and last contact stage under different incident wave angle are performed. It is observed that the relative motions under quartering sea in first contact stage are the largest. Furthermore, in order to reveal the coupling mechanism, different configurations of the barges and Spar are investigated for the first contact stage under irregular waves. It is found that the relative heave motions on the LMUs are larger when the deck and barges are rigidly connected to form a catamaran-barge.

The Postbuckling Behavior of Compressed Elastica Inside a Flexible Tube: Experimental and Numerical Investigation

Abstract The postbuckling behavior of an elastic fiber subjected to lateral constraints is of practical importance in a wide range of medical and engineering applications. The vast majority of existing studies have adopted the assumption that the lateral constrains are fixed in space and rigid. This assumption is often far from the reality of the physical complexity of the abovementioned systems. In this paper, we study analytically, numerically, and experimentally the behavior of an elastic fiber that is subjected to compressive force and constrained by a flexible tube. The latter marks a point of departure from available research. Our experiments provide quantitative information related to the overall behavior of the system, like force-shortening relation and deflection of the flexible tube. That information is complemented by finite-element simulations that enable in-depth analysis of the deformation of the fiber as well as contact characteristics between the fiber and the inner wall of the flexible tube. Finally, a simple mathematical model, aimed at providing analytical insights, is presented. Overall, the theoretical, numerical, and experimental results are in very good agreement. They highlight the fact that the behavior of a compressed fiber that is constrained by a deformable tube significantly deviates from that of a fiber constrained inside a rigid cylinder. Moreover, it is shown that the overall behavior as well as the evolution of contact between the fiber and the cylinder heavily depends on the ratio between the stiffness of the fiber and the lateral stiffness of the tube.

Gas Seepage Under Continuous and Step Loading Based on True Triaxial Seepage Test Apparatus

The conventional triaxial loading in gas seepage studies does not reflect the actual stressing state in the coal seam. Thus, a true triaxial seepage experimental apparatus is developed before seepage tests are conducted with it. The first group of tests is carried out with continuous axial loading under uniform lateral constrain on moulded coal specimen: one test under constant-velocity axial loading, two tests under monotonic variable-velocity axial loading, and two tests under single-cycle variable-velocity axial loading. The tests reflect the multi-step, discontinuous, stressing condition with variable-loading rate and strength in a coal seam. The law of coal deformation and gas permeability variation under constant-velocity and variable-velocity axial loading is obtained. Then, the multi-step seepage tests under different non-uniform lateral pressures are conducted, focusing on permeability variation under different triaxial stresses versus gas pressure and intermediate principal stress. The permeability increase with gas pressure decrease is confirmed and interpreted. Moreover, the turning point between Klinkenberg effect and gas wedging effect in the coal seam is determined. A simplified concept of average effective stress is put forward, and the dominant influence of this average effective stress on coal seam permeability is identified based on the concept.

Bicelles and nanodiscs for biophysical chemistry

Membrane nanoobjects are very important tools to study biomembrane properties. Two types are described herein: Bicelles and Nanodiscs. Bicelles are obtained by thorough water mixing of long chain and short chain lipids and may take the form of membranous discs of 10–50 nm. Temperature-composition-hydration diagrams have been established for Phosphatidylcholines and show limited domains of existence. Bicelles can be doped with charged lipids, surfactants or with cholesterol and offer a wide variety of membranous platforms for structural biology. Internal dynamics as measured by solid-state NMR is very similar to that of liposomes in their fluid phase. Because of the magnetic susceptibility anisotropy of the lipid chains, discs may be aligned along or perpendicular to the magnetic field. They may serve as weak orienting media to provide distance information in determining the 3D structure of soluble proteins. In different conditions they show strong orienting properties which may be used to study the 3D structure, topology and dynamics of membrane proteins. Lipid Bicelles with biphenyl chains or doped with lanthanides show long lasting remnant orientation after removing the magnetic field due to smectic-like properties. An alternative to pure lipid Bicelles is provided by nanodiscs where the half torus composed by short chain lipids is replaced by proteins. This renders the nano-objects less fragile as they can be used to stabilize membrane protein assemblies to be studied by electron microscopy. Internal dynamics is again similar to liposomes except that the phase transition is abolished, possibly due to lateral constrain imposed by the toroidal proteins limiting the disc size. Advantages and drawbacks of both nanoplatforms are discussed.

Application of spatial lateral constrained loading feedback control method in pseudo-static testing

In seismic performance testing of structures, the accurate boundary condition is the key to guarantee the accuracy of testing results. The one-way pseudo-static testing is the most common loading method in civil engineering seismic testing. However, the structures are all spatial structures in practice, therefore, the lateral constraints on specimen are necessary in one-way pseudo-static testing. The reaction devices are used to constrain the specimen laterally in traditional loading method, but the traditional loading method has some disadvantages such as high cost, large occupation of space and so on. In order to avoid those disadvantages of traditional loading method, a spatial lateral constrained loading feedback control method is proposed in this paper. In this method, the main direction loading and lateral constrain of the specimen are realized by the actuators, and the accurate control of the constraint boundary can be achieved by adjusting the position of the lateral constrained actuators. In order to verify the accuracy and feasibility of the proposed method, a pseudo-static testing of a full-scale two-story three-span single concrete frame is conducted. The experimental results show that the proposed method is reliable, and the experiment accuracy can be guaranteed.

The Impact of an Obstacle on Competitive Evacuation Through a Bottleneck

Within the last decade, a number of crowd accidents have attracted the interest of scientists to study the movement of crowd under high levels of competition. An interesting finding in crowd dynamics is that the presence of an obstacle at an appropriate distance in front of an exit can improve flow rate. A numerical simulation based on the discrete element method (DEM) and social force model was adopted in this paper in order to study the impact of obstacles on flow rate during competitive evacuation in two typical Settings with a single 0.8 m-wide exit. Setting I is a 15 m-wide room and Setting II is a 3 m wide corridor formed by the same room with lateral constrains. Numerical simulation in Setting I showed that a 1 m-obstacle at 1-m away from the exit can reduce evacuation time by approximately 49%. However, a contrasting increase of evacuation time by approximately 64% is observed in Setting II for the obstacle at the same location. To verify the findings, a number of experiments were conducted by compelling mice to escape under high competition in two similar settings. The general limitations of such experiments were accepted and described. These results were consistent with numerical simulations. This study demonstrates that whether an obstacle can improve the flow rate passing through an exit is dependent on the surrounding geometry.

A method for determining the horizontal impact load based on the rotational speed of the aircraft's wheel in a landing gear drop test

ABSTRACTThe maximum horizontal impact load experienced by an aircraft's landing gear wheel during landing is an important parameter in the landing gear's safety design and performance analysis. Using a noncontact photoelectric testing method, this paper experimentally obtained the temporally varying data of the instantaneous rotational speed for an aircraft wheel at the instant of its contact with the test platform. Moreover, the kinetic relationship between the transient rotational speed of the aircraft's wheel and the horizontal impact force was established. According to the temporally varying data measured from the transient rotational speed of the aircraft's wheel, the maximum horizontal impact load at the instant the aircraft contacted the platform was calculated. To verify the accuracy of this method in which changes in rotational speed of the aircraft's wheel determine the horizontal impact load, verification equipment without lateral constrains was designed and used for testing. The experimental results showed that the horizontal impact load determined based on the transient rotational speed of the aircraft's wheel are consistent with the results obtained using direct measurements obtained from custom-made equipment free of lateral constrains. This paper provides a new experimental method for measuring the horizontal impact load on the aircraft's wheel.

A New Method for Determining Horizontal Impact Load Based on Rotational Speed of Aircraft Wheel in Landing Gear Drop Test

The maximum horizontal impact load experienced by the aircraft landing gear wheel during landing is an important parameter in landing gear safety design and performance analysis. Using a non-contact photoelectric testing method, this paper experimentally obtained the dynamic data of the instantaneous rotational speed for an aircraft wheel when it contacts the platform. Moreover, the kinetic relationship between the transient rotational speed of the aircraft wheel and the force of horizontal impact was established. According to the change data measured from the transient rotational speed of the aircraft wheel, the maximum horizontal impact load at the instant of aircraft contact with the platform was calculated. To verify the accuracy of this method, in which changes in rotational speed determine the horizontal impact load, verification equipment without lateral constrains was established to test the horizontal impact load of the aircraft wheel. The experimental results showed that the horizontal impact load determined by the transient rotational speed of aircraft wheel is consistent with the results obtained by self-built measurement equipment without lateral constrains.

An armour-piercing projectile penetration in a double-layered target of ultra-high-performance fiber reinforced concrete and armour steel: Experimental and numerical analyses

In this paper, experimental and numerical investigations are conducted to study the dynamic response of a double-layered target of ultra-high-performance fiber reinforced concrete (UHPFRC) and armour steel subjected to an armour-piercing projectile impact. Firstly, 9 shots of ogival/conical nose projectiles penetration test on three configurations of segmented UHPFRC target with armour steel are carried out. Based on the measured penetration depth in the backing target, the ballistic efficiency of the composite targets is then analyzed quantitatively via the Differential Efficiency Factor. The meso-scale Lattice Discrete Particle Model (LDPM), which accounts for rate effect and tensile fracture, is used as the constitutive model to describe the UHPFRC material mechanical response. While the armour steel material is modeled by Johnson–Cook yield criterion with finite element method. The numerical results of both failure mode and residual penetration depth are presented and evaluated with the experimental results. Consequently, the importance of UHPFRC conditions such as fiber content, lateral constrain, lamination is addressed with respect to the validated penetration tests. Finally, the UHPFRC plate ballistic properties are analyzed through extensive perforation simulations.

Displacements prediction from 3D finite element model of maxillary protraction with and without rapid maxillary expansion in a patient with unilateral cleft palate and alveolus.

BackgroundBoth maxillary protraction and rapid expansion are recommended for patients with cleft palate and alveolus. The aim of the study is to establish a three-dimensional finite element model of the craniomaxillary complex with unilateral cleft palate and alveolus to simulate maxillary protraction with and without rapid maxillary expansion. The study also investigates the deformation of the craniomaxillary complex after applied orthopaedic forces in different directions.MethodsA three dimensional finite element model of 1,277,568 hexahedral elements (C3D8) and 1,801,945 nodes was established based upon CT scan of a patient with unilateral cleft palate and alveolus on the right side in this study. A force of 4.9 N per side was directed on the anatomic height of contour on the buccal side of the first molar. The angles between the force vector and occlusal plane were −30°, −20°, −10°, 0°, 10°, 20°, and 30°. A force of 2.45 N on each loading point was directed on the anatomic height of contour on the lingual side of the first premolar and the first molar to simulate the expansion of the palate.ResultsThe craniomaxillary complex displaced forward under any of the loading conditions. The sagittal and vertical displacement of the craniomaxillary complex reached their peak at the protraction degree of −10° forward and downward to the occlusal plane. There were larger sagittal displacements when the maxilla was protracted forward with maxillary expansion. The palatal plane rotated counterclockwise under any of the loading conditions. Being protracted without expansion, the dental arch was constricted. When supplemented with maxillary expansion, the width of the dental arch increased. Transverse deformation of the dental arch on affected side was different from that on unaffected side.ConclusionsProtraction force alone led the craniomaxillary complex moved forward and counterclockwise, accompanied with lateral constrain on the dental arch. Additional rapid maxillary expansion resulted in a more positive reaction including both larger sagittal displacement and the width of the dental arch increase.

Stability analysis of a large landslide in hydropower engineering

This paper is devoted to stability analysis of the Zheng-Gang landslide in the Gu-Shui hydropower station in China. Based on the geological field investigations, the formation processes, the deformation mechanism related to rainfalls and the instability mode are first analyzed. Large scale direct shear tests on soils in the slip zone are performed in order to characterize influences of the content of particle and water on natural shear strength. Due to the difficulty to consider the lateral constrain and curvature effects of the bottom sliding surface, different three-dimensional models are established using the limit equilibrium method and the large strain Lagrange finite difference method. The results of stability analysis are in good agreement with the field observations. It is shown that the natural landslide is in a limit state and the creep deformation along the slipping surface is the main mechanism of landslide instability under in situ conditions.

Nanoindentation response of substrate-attached and freestanding single-crystalline Fe7Pd3 ferromagnetic shape memory thin films around the martensite transition: The impact of constraints and beyond

Ferromagnetic shape memory alloys offer great potential in the fields of engineering and medical sciences as integrated actuators or sensors. However, their physical properties, when miniaturized and connected to a substrate or mounted as active elements, are still insufficiently understood. The present work explores the impact of miniaturization and external boundaries on one of the most central features, namely twin boundary mobility. By measuring the nanoindentation response of substrate-attached films and freestanding foils around the austenite↔martensite transformation temperature in classical indentation, as well as dynamical quasi-continuous stiffness-measurement mode, dramatic softening and increasing recovery after film lift-off are discovered. The atomistics of these findings are explored with the help of classical multimillion-atom molecular dynamics simulations on indentation into martensite and austenite films on rigid or flexible substrates, as well as freestanding or mounted thin foils. They clearly demonstrate how substrate or lateral constrains hinder twin boundary motion, while complete untwinning only prevails in the presence of a flexible substrate or completely free foils. Experimentally observed pop-in events can be rationalized as local austenite→martensite transitions. Surface softness, which is observed by low indentation moduli, when compared to predictions from the bulk elastic constants, might indicate a more fundamental scenario close to the martensite transformation.

Ge-on-Si Bufferless Epitaxial Growth for Photonic Devices

Demonstration of bufferless fully crystalline Ge-on-Si is shown. Si-Ge interdiffusion is limited to 10nm. One dimension lateral constrain provides a mechanism to prevent the formation of polycrystalline material. TEM, SEM and XRD analysis confirms Ge crystallinity. PL shows that dopant concentration is retained avoiding the dopant sink that the Ge buffer provides. Dopant concentration is retained at high levels of 1019cm-3 for n-type. Preliminary results exhibit a dopant surfactant effect determining changing the required channel dimensions for crystallinity with the dopant concentration and type used.

Phase-field simulation of solidified microstructure evolution in the presence of lateral constraint

Lateral constrain in the presence of melting has a significant effect on microstructure evolution of crystal growth, and this effect is related to the size and property of lateral constrain, thus determining microstructure formation during solidification. In the paper, microstructure evolution in the presence of lateral constrain during the solidification of pure Ni metal is simulated using a non-isothermal phase-field model. Effects of size and properties of lateral constrain are simulated and studied, also microstructures formed at different initial dendritic arm distances are discussed. Results indicate that the presence of lateral constrain has a direct influence on pattern evolution which determines the microstructure formation. Microstructure changes significantly with lateral constrain distance turning small, initial constrain temperature low becoming low and initial dendrite arm distance growing. Different heights of lateral constrains have almost the same effects on microstructure change during solidification.

Single- and Multigrain Luminescence Dating of Sediments Related to the Greenville Fault, Eastern San Francisco Bay Area, California

Near urban areas and extending ∼60 km along the eastern margin of the Livermore Valley, the Greenville fault is the easternmost right-lateral strike-slip fault of the San Andreas system in the greater San Francisco Bay area. Notwithstanding the 1980 Livermore earthquake sequence (mainshock M L 5.9) on the Greenville fault, there is no record of recency or of Holocene rates of activity on the Greenville fault, yet this fault exhibits clear geomorphic evidence of late Quaternary faulting. In trenches parallel and normal to the fault through alluvial fan deposits at the Laughlin Road site only pedogenic carbonate was available for ![Graphic][1] dating. Therefore, we applied several photon-stimulated luminescence (PSL) sediment-dating procedures to the silt and sand fractions of six samples. The polymineral-fine-silt multi-aliquot age estimates are generally inaccurate, but the single-grain quartz (SGQ) and multigrain quartz single-aliquot regenerative-dose (SAR) ages from sand grains are in stratigraphic sequence. In trench 3A these SAR ages range from 125±11 yrs (before 2007) within the topmost unit L to 13.45±0.79 ka in the base of the lowermost channel-fill unit G. The SAR PSL results demonstrate the importance of the use of SGQ dating for such sediments and provide the first numerical ages used to constrain the slip rate on the Greenville fault. Trench exposures reveal that unit G is an alluvial sequence infilling a paleochannel offset in a right-lateral sense along the northern Greenville fault. Age estimates from upper and middle unit G bracket deposition of subunit Gb are between 11.12±0.55 ka and 10.64±0.85 ka and those from middle and lower unit G bracket deposition of subunit Go are between 11.12±0.55 ka and 13.45±0.79 ka. These SAR PSL age estimates and measurements of the lateral offset constrain a preliminary slip-rate estimate to about 2 mm/yr or higher for the northern Greenville fault zone. [1]: /embed/inline-graphic-1.gif

Stress Analysis in Single and Multi Fastened Single-Lap Composite Joints

The use of composite materials in many engineering structures has increased recently. The structures are jointed together by single or multiple bolted mechanical fastening to transfer the loads from one member to another. Applications of such joints require adequate knowledge of stress distribution in the vicinity of the boundary of pin hole. In this study, stress analysis is conducted with finite element method to study the stress distributions in the vicinities of both single-pin and multi-pin loaded holes of multi-axial warp knit fabric composite laminates. The perfect fit condition and contact with friction between the pin and hole without lateral constrain are assumed in the analysis. Effects of friction, stacking sequence, ratio of edge distance over hole diameter, ratio of width over hole diameter, number of pins, number of rows, number of column and hole patterns are evaluated. The results show they have a significant influence on joint performance.

A Multiparticle Simulation of Powder Compaction Using Finite Element Discretization of Individual Particles

AbstractDiscrete element studies of powder compaction have become popular recently. A disadvantage of this technique is the need for simplification of the inter-particle contact behavior which limit the applicability of DEM to small relative densities. To overcome this problem, we analyze the compaction of powder by a 2-D finite element study of the compaction of 400 particles, each of which is discretized at a sufficient level to provide adequate detail of the interparticle interaction. The material is modeled as elastic-perfectly plastic. Simulations show that: (a) there is an effect of interparticle friction on the macroscopic response in the earlier stages of compaction, (b) there is significant rearrangement even in highly constrained compaction modes, (c) the absence of friction promotes inhomogeneous deformation in the compact, and (d) conditions for fragmentation develop in particles with loose lateral constrains.