Differential Displacement Research Articles

Imaging study of midface growth with bone-borne trans-sutural distraction osteogenesis therapy in growing cleft lip and palate patients

Trans-sutural distraction osteogenesis (TSDO) promotes midface growth in growing cleft lip and palate (CLP) patients with midfacial hypoplasia. The superficial skeletal changes after therapy revealed rotation advancement of the midfacial skeleton associated with differential displacement in each segment, but reports rarely focus on the changes of internal structures, including circummaxillary sutures, the maxillary tuberosity and the maxillary sinus, which may play a crucial role during this process. This study evaluated the computed tomographic (CT) images of 26 growing CLP patients who received bone-borne TSDO therapy. The results revealed that the most prominent new bone formation occurred in the pterygomaxillary suture and pushed the P-point forward. The maxillary first molar exhibited significantly greater advancement compared with the P-point due to the growth of the maxillary tuberosity. The contribution ratio values of the advancement of the maxillary tuberosity and P-point to the maxillary first molar were 26% and 74%, respectively, in UCLP and 25% and 75%, respectively, in BCLP. Furthermore, the maxillary sinus volume was also significantly increased. In conclusion, midface growth with bone-borne TSDO therapy depends on both secondary displacement promoted by sutural bone formation mainly in the pterygomaxillary suture and primary displacement by growth of the maxillary tuberosity and maxillary sinus volume.

A Linear Differential Inductive Displacement Sensor With Dual Planar Coils

A non-contact displacement sensor employing a couple of planar coils etched on printed circuit boards (PCBs) and an E-type soft ferromagnetic core is proposed here. The E-type soft ferromagnetic core moves over two triangular shaped spiral coils etched on a couple of PCBs. The variation in the inductances of the two coils has a cubic polynomial relationship with the displacement of the core. An appropriate signal conditioning technique operates on the inductances and provides an output that varies linearly with the displacement. The symmetrical structure of the sensor provides negligible cross axis sensitivity. Simulation studies and results obtained from a prototype sensor having a 70-mm range and a resolution of $2~\mu \text{m}$ , built and tested, establish the efficacy of the proposed technique. The worst-case nonlinearity observed from the prototype is 0.4%.

Repair assessment for distortion-induced fatigue cracks in a seismically retrofitted double-deck bridge complex

Many steel bridges in the United States designed before the mid-1980s are highly susceptible to distortion-induced fatigue cracking. This vulnerability is substantially increased if the out-of-plane driving force caused by differential girder displacement is increased for any reason. This research examines one such case where a double-deck bridge complex, originally built in the 1960s, was retrofitted to improve seismic performance. As part of the retrofit, single angle K-type diaphragms were replaced with stiffer double-angle cross-type diaphragms. This seismic retrofit led to an increase in web-gap stresses, and within approximately one year following the retrofit, inspectors identified numerous fatigue cracks in the web of longitudinal girders where connection plates terminate near top flanges. A repair measure was implemented to provide a positive connection between the connection plate and the girder flange. The purpose was to reduce the high stress concentrations in the web-gap region by restricting the out-of-plane distortion in the web-gap region. Field tests were carried out in addition to developing finite element (FE) models to investigate the efficacy of the repair technique. The results confirmed a significant decrease in the web-gap stress after implementation of the repair, and a subsequent FE analysis showed that the new load path through the repair angle section did not introduce a new fatigue sensitive area. In fact, the repair resulted in stresses well below the constant amplitude fatigue threshold (CAFT) for this type of detail.

Mechanical Treatment of Crack-Arrest Holes Subjected to Distortion-Induced Fatigue

Fatigue cracking is a major concern for many aging steel bridges in the United States. A common form of crack remediation is the drilling of crack-arrest holes, increasing the crack tip radius and thus reducing the applied stress intensity. However, the majority of cracking that occurs in bridge structures is caused by distortion-induced fatigue. Cross-frame forces generated by differential girder displacement produce multiaxial, mixed-mode fatigue loading at the intersection of the girder web, flange, and connection plate, producing cracking along web-to-stiffener welds and flange-to-web welds. Crack-arrest holes are often used as a first line of defense at these cracks. However, crack-arrest holes deform out-of-plane under distortion-induced fatigue loading, and have been found to be of limited utility in this application.Previous research has shown that mechanical treatment of crack-arrest holes has the potential to improve the efficacy of crack-arrest holes for halting crack propagation for in-plane fatigue, but the performance of such treatments is unknown for distortion-induced fatigue cracks. A research program sponsored by the Kansas Department of Transportation is investigating the effectiveness of one such technology for controlling crack propagation in steel bridge girders susceptible to distortion-induced fatigue. This technology produces a cold-worked region around the crack-arrest hole, introducing a field of compressive residual stresses aimed at retarding crack propagation. Evaluation of the mechanically treated crack-arrest holes is evaluated analytically for both in-plane and out-of-plane fatigue loading. This paper presents background on the problem and preliminary findings of the study.

Evaluation of a Digital Image Correlation Bridge Inspection Methodology on Complex Distortion-Induced Fatigue Cracking

Distortion-induced fatigue cracking in aging steel bridges is a primary concern for many bridge owners and stakeholders, accounting for the majority of fatigue cracks in bridges in the United States. Currently Departments of Transportation primarily use visual inspections to locate and characterize fatigue cracks. However, this approach has drawbacks, as recent studies have shown that visual inspections are not able to consistently identify realistically-sized fatigue cracks in highway infrastructure. Additionally, it requires significant time and cost to perform visual inspections, and both inspectors and the traveling public are placed at risk during the inspection. Bridge owners and stakeholders would benefit from the development of inspection techniques that do not rely on hands-on human visual inspection – to reduce the risks of harm to the inspectors and traveling public, increase reliability, and decrease the time and cost of performing inspections.Vision-based technologies are an active area of research in the field of structural health monitoring, aimed at developing alternatives to manual inspection for identifying damage to transportation infrastructure. The majority of these studies have focused on macro-indicators of damage, including identifying excessive corrosion, concrete deck deterioration, and large displacements due to substructure movement. Digital image correlation (DIC) is one such vision-based technology that shows promise for detecting and characterizing fatigue cracks, but investigations and applications have thus far been limited to simple, in-plane cracking.Three-dimensional DIC measurements have the ability to capture full-field displacements and surface strains, allowing for the potential of identifying and characterizing out-of-plane fatigue cracks, such as those occurring on steel bridges exposed to loading through differential girder displacement. Since the majority of fatigue cracks arise from out-of-plane loading, investigating the efficacy of DIC for detecting distortion-induced fatigue cracks is of clear value.This paper describes an experimental study in which a scaled steel girder-to-cross-frame specimen was cyclically loaded to produce geometrically complex distortion-induced fatigue cracking. To examine the potential usefulness of DIC for future automated bridge inspections the resulting fatigue cracks were characterized using DIC and visual inspection. The methodology applied proved successful at quantifying certain aspects of the complex, bifurcating cracks, but had difficulty characterizing crack segments that are no longer actively loaded. Additional work is needed to improve the accuracy and reliability of the crack detection results for this technology to potentially be used as an automated inspection tool in the future.

A Condition for Singular Optimal Control Formulation for a Tandem Pair of Gravity Fed Linear DC Machine Powered Mine Locomotives

Abstract The key focus in this study is on gravity fed linear DC machines used to drive mine locomotives. A case for optimal control singularity analysis for this tandem pair of gravity fed linear DC machines on a slope is thus presented. The key operational feature is for a generator locomotive to drive a motor locomotive with gravity providing the machine disparity for generator and motor action. Optimal control formulation is extended in this study, particularly optimal control singularity formulation. The optimal controller should be able to minimize the relative displacement between the machines. Mine locomotive dynamics results are also presented to show that the differential velocity and displacement are minimized. The performance index and Lagrangian are also minimized. The optimal control formulation is demonstrated via switching function differential calculus. The solution is shown to improve mine locomotive energy performance.

From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard

Abstract. In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen, Svalbard. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle Pennsylvanian rifting, which resulted in the deposition of thick sedimentary units in Carboniferous basins like the Billefjorden Trough. The clustering of these varied tectonic settings sometimes makes it difficult to resolve the tectono-sedimentary history of individual stratigraphic units. Notably, the context of deposition of Mississippian clastic and coal-bearing sedimentary rocks of the Billefjorden Group is still debated, especially in central Spitsbergen. We present field evidence (e.g., growth strata and slickensides) from the northern part of the Billefjorden Trough, in Odellfjellet, suggesting that tilted Mississippian sedimentary strata of the Billefjorden Group deposited during active (Late/latest?) Mississippian extension. WNW–ESE-striking basin-oblique faults showing Mississippian growth strata systematically die out upwards within Mississippian to lowermost Pennsylvanian strata, thus suggesting a period of widespread WNW–ESE-directed extension in the Mississippian and an episode of localized extension in Early–Middle Pennsylvanian times. In addition, the presence of abundant basin-oblique faults in basement rocks adjacent to the Billefjorden Trough suggests that the formation of Mississippian normal faults was partly controlled by reactivation of preexisting Neoproterozoic (Timanian?) basement-seated fault zones. We propose that these preexisting faults reactivated as transverse or accommodation cross faults in or near the crest of transverse folds reflecting differential displacement along the Billefjorden Fault Zone. In Cenozoic times, a few margin-oblique faults (e.g., the Overgangshytta fault) may have mildly reactivated as oblique thrusts during transpression–contraction, but shallow-dipping, bedding-parallel, duplex-shaped décollements in shales of the Billefjorden Group possibly prevented substantial movement along these faults.

Numerical analysis of straight and curved underground pipeline performance after rehabilitation by cured-in-place method

Underground pipelines are prone to damage by corrosion in Taiwan due to the humid climate and the aging and overuse of pipelines. No-dig technologies are necessary, as the cities in Taiwan are highly populated. Rehabilitation methods, including the cured-in-place pipe (CIPP) method, provide an alternative to the new no-dig installation methods, which are comparatively more expensive. In this study, the numerical analysis software ABAQUS was used to simulate straight-line and curved underground pipelines damaged by corrosion. After calibration by small-scale physical modeling in the laboratory, numerical models were applied to the analysis of the mechanical behavior of straight-line and curved underground pipelines. To analyze the performance of the CIPP rehabilitation method, different scenarios for straight-line and curved pipelines were considered. These included before- and after-rehabilitation, different internal pressures and surface loading conditions, and different liner deformabilities and pipe-liner interface strengths. The results suggest that the CIPP method can reinforce damaged pipes by reducing stress concentration and differential displacement near the corrosion void. However, proper liner thickness, liner material properties, and pipe-liner interface strength are essential for well-designed CIPP rehabilitation.

Ultrasound-based cell sorting with microbubbles: A feasibility study.

The isolation and sorting of cells is an important process in research and hospital labs. Most large research and commercial labs incorporate fluorescently or magnetically labeled antibodies adherent to cell surface antigens for cell identification and separation. In this paper, a process is described that merges biochemical labeling with ultrasound-based separation. Instead of lasers and fluorophore tags, or magnets and magnetic particle tags, the technique uses ultrasound and microbubble tags. Streptavidin-labeled microbubbles were mixed with a human acute lymphoblastic leukemia cell line, CCL 119, conjugated with biotinylated anti-CD7 antibodies. Tagged cells were forced under ultrasound, and their displacement and velocity quantified. Differential displacement in a flow stream was quantified against erythrocytes, which showed almost no displacement under ultrasound. A model for the acoustic radiation force on the conjugated pairs compares favorably with observations. This technology may improve on current time-consuming and costly purification procedures.

Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm-2 and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm-2 and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.

Effects of asphalt overlay on XCC pile-supported embankment vibration from a moving vehicle

Vibration behaviors of the asphalt pavement-embankment-X-shaped cast-in-situ concrete (XCC) piles reinforced ground system under a moving vehicle are simulated through three-dimensional finite element approach. The influences of asphalt overlays on displacement pattern on the top of pavement, the asymmetric movement of surrounding soil around XCC piles, and the concentration coefficient after laying the overlay are investigated. The obtained results show that the dynamic displacement decreases as a consequence of the increasing stiffness of this system after laying asphalt overlays. It is also shown that the vertical displacement of soil around piles decreases as the thickness of overlays increases. Meanwhile, the asymmetric extent, in which there is an obvious differential displacement between the flat and concave area, is presented. In addition, the concentration coefficient for the embankment's top flat is significantly larger than that for the slope surface, and its increasing is caused by asphalt overlays.

Vulnerability assessment of low-code reinforced concrete frame buildings subjected to liquefaction-induced differential displacements

While liquefaction has been widely recognized as being one of the principal earthquake hazards resulting to significant economic and societal losses, research in the vulnerability assessment and quantitative evaluation of the expected physical damages to building structures is rather limited. In this respect, this study aims at the vulnerability assessment of typical low-code reinforced concrete (RC) frame buildings of various heights with shallow flexible foundations subjected to differential permanent displacements due to liquefaction. Nonlinear static analyses are carried out for each considered structural typology assuming different gradually increasing differential displacement patterns applied as quasi-static loads directly at its supports (footings). Different damage mechanisms are examined including a flexural damage of the building members and a shear failure of the columns. The proposed methodology results to the development of lognormally distributed fragility curves for different structural damage states as a function of the liquefaction induced differential displacements. It is shown that the height of the structure as well as the existence or not of a horizontal component of the differential displacements represent key factors affecting the vulnerability assessment. Vulnerability curves are also constructed to assess the expected direct losses in normalised cost terms. The whole approach is illustrated through a specific example.

Design and Analysis of Thermoplastic Metal Detector RC Car with Wireless Charging

Abstract The RC Car industry is a growing industry that will always be a past time for the older generation. This research is focused on a specific type of RC Car which is a Metal Detecting one. Metal Detectors have been developed for many years. Through research there aren’t many metal detecting RC Cars on the market. Currently it’s extremely limited in range and depth of detection. The goal of this research is to improve, build and test a new RC-metal detector technology. A thermoplastic-ABS used to build the chassis of the RC- metal detector. ABS is easily machined, sanded, glued and painted. Finite element analysis is a powerful tool that allows us to quickly analyze and refine a design. When the Chassis fixed at front Differential (Displacement), the value of the maximum stress and the deflection are higher than when the Chassis Fixed at Rear Differential. The maximum deflection is shown as about 1.339 inches. This value is the resultant of the deflection in all three directions. This research includes, a cost analysis for each piece of the car, group goals for the RC Car and Metal Detector. A working prototype is designed before moving into the final design phase in order to assure that the best possible product can be produced. There is a wireless charging station that ease the process of recharging the battery.

Seismic Response of the Three‐Span Bridge with Innovative Materials Including Fault‐Rupture Effect

The seismic performance of the SR99 Bridge with conventional and advanced details in Seattle, Washington, was studied via a nonlinear, time history analysis of a multidegree of freedom model. The bridge consists of three spans supported on two single‐column piers and will be the first built bridge in the world in which superelastic shape memory alloy (SMA) and engineered cementitious composite (ECC) are implemented to reduce damage at plastic hinges and minimize residual displacements. Existing finite‐element formulations in the finite‐element software OpenSees are used to capture the response of the advanced materials used in the bridge. The earthquake induced by strike‐slip fault was assumed to produce a surface rupture across the SR99 Bridge. The effect of the rupture was modeled by a static, differential ground displacement in the fault‐parallel direction across the rupture. The synthetic suite of scaled bidirectional near‐fault ground motions used in the analysis contains common near‐fault features including a directivity pulse in the fault‐normal direction and a fling step in the fault‐parallel direction. Comparisons are made on behavior of two different bridge types. The first is a conventional reinforced concrete bridge and the second is a bridge with Nickel‐Titanium (NiTi) SMA reinforcing bar at the plastic hinge zone and ECC in the whole column. Fault‐parallel near‐fault earthquakes typically exhibit a static permanent ground displacement caused by the relative movement of the two sides of the fault. When the fault is located between piers, the pier shows a higher demand. Fault‐normal analysis results show effectiveness of the innovative interventions on the bridges in providing excellent recentering capabilities with minimal damage to the columns. But the maximum drift computed in the SMA bridge is slightly higher than reinforced concrete (RC) bridges, contributed by comparatively low stiffness of the superelastic SMA bars compared to the steel reinforcing bars.

A novel experimental method to characterise the shear strength of concrete based on pre-stressed samples. A comparison with existing techniques

Mode II shear fracture process can be observed in plain-concrete structures exposed to intensive loadings such as shock, blasting or projectile-impact. It is the reason why the quasi-static and dynamic shear fracturing properties of concrete need to be investigated. In previous works performed by Forquin and coauthors a passive confining cell was applied to PTS (Punch-Through-Shear) specimens in a similar way than in quasi-oedometric compression tests where metallic ring are used as passive confinement. However the change of confining level during the sample loading constitutes a main drawback of this technique. In the present work a novel testing method is proposed based on a pre-stressing of the sample. To do so, the concrete specimen is inserted into pre-stressed metallic cell. During the unloading stage confining stresses are transferred to the ligament of the sample. In a second stage, a differential displacement applied to the central part of the sample toward the side parts produces a shearing of the ligament. The experiments performed in static and dynamic conditions (SHPB testing) allow the shear response of concrete to be determined over a wide range of strain-rates. In the present communication, the testing technique and obtained results are compared to the obtained data with the previous experimental method.

Non-uniform displacement and strain between the soleus and gastrocnemius subtendons of rat Achilles tendon.

Achilles tendon (AT) comprises of 3 subtendons arising from the soleus (SOL) and the lateral (LG) and medial (MG) heads of the gastrocnemius muscle. While recent human studies show differential displacement within AT, these displacements have not been attributed to specific subtendons. We tested the hypothesis that the SOL and LG subtendons show differential displacement and strain during various combinations of SOL, LG, and MG excitations. Movement of knots, sutured onto SOL and LG subtendons of 12 Wistar rats, was videotaped, while the muscles were stimulated intramuscularly and ankle torque was assessed. When SOL only was stimulated, the plantar flexion torque was the smallest among the different conditions (P<.001). In this condition, from passive to active state, the displacement (0.57 vs 0.47mm, P=.002) and strain (8.4% vs 2.4%, P<.001) in the SOL subtendon were greater than in LG subtendon. When LG only was stimulated, a higher ankle torque was measured as compared to SOL stimulation (P<.001); the displacement was similar in both subtendons (~0.6mm), while the strain was greater in LG than in SOL (4.7% vs 1.7%, P<.001). When all 3 muscles were stimulated simultaneously, ankle torque was highest and the displacement (0.79 vs 0.74mm, P=.002) and strain (7.7% vs 4.4%, P=.003) were greater in SOL than in LG. These data show that the different subtendons of AT can experience relative displacement and differential strains. Together with anatomical dissections, the results revealed that such uniformities may be due to a lower stiffness of SOL subtendon compared to LG.

Numerical analysis of the mechanical behaviors of pressurized underground pipelines rehabilitated by cured-in-place-pipe method

Due to the humid climate in Taiwan area, the underground pipes are prone to be damaged by corrosion, which could be more severe for the environment with high salinity near the coast. In addition, the situation could be worse where the underground pipeline planning was not enforced. For example, a water pipe or a sewage pipe may be too close to a pressurized pipe, which could be corroded if the water pipe or the sewage pipe leaked. In this study, the numerical simulation software ABAQUS was used to simulate underground pipelines damaged by corrosion. The stress and displacement behavior was analyzed for scenarios with different internal pressure and surface loading conditions. In addition, the performance of the cured-in-place-pipe (CIPP) method, a trenchless rehabilitation method was also numerically analyzed. The results suggest that it can reinforce the damaged pipe by reducing the stress concentration and reducing the differential displacement. However, the design of the CIPP liner could be further optimized in terms of its design thickness.

Laboratory model tests about the sand embankment supported by piles with a cap beam

ABSTRACTPiled embankment is widely used in soft soil areas. Most researches focused on effects of embankment height-net pile spacing ratios and equal settlement plane; there are limited publications paying attention to the shape of slip surfaces occurring in the embankment. In some extreme conditions, such as the ground being quite soft or embankment height needed to be restricted, to reduce the differential settlement and lateral displacement, piles are usually installed in several rows and cap beams or isolated caps are placed on the heads of piles. In this paper, five laboratory tests were carried out to investigate the effect of embankment height on the slip surfaces and stress exerted on the subsoil. Based on the observation of the slip surface’s shape within the embankment fill, a new calculation model is proposed to predict the stress exerted on the subsoil. In comparison with the experimental results, the accuracy of this new method is verified. From the perspective of reducing the differential settlement and cost savings, the embankment height is about four times net pile spacing according to this calculation model, since continuing to increase the embankment will not make an obvious difference to the reduction of soil stress exerted on the subsoil.

Strength Analysis and Reliability Evaluation for Speed Reducers

This paper studies the structural stresses of differential drive (DD) and harmonic drive (HD) for design improvement of reducers. The designed principles of the two reducers are reported for function comparison. The critical components of the reducers are constructed for performing motion simulation and stress analysis. DD is designed based on differential displacement of the decelerated gear ring as well as HD on a flexible spline. Finite element method (FEM) is used to analyze the structural stresses including the dynamic properties of the reducers. The stresses including kinematic properties of the two reducers are compared to observe the properties of the designs. The analyzed results are applied to identify the allowable loads of the reducers in use. The reliabilities of the reducers in different loads are further calculated according to the variation of stress. The studied results are useful on engineering analysis and reliability evaluation for designing a speed reducer with high ratios.

Analysis of unsteady heat transfer of internal combustion engines’ exhaust valves

This study is concerned with the analyses of heat transfer through an exhaust valve considering the real unsteady effects during the cycle of an internal combustion engine and to identify the factors and parameters affecting the heat transfer. The valve is segmented into several zones to facilitate incorporating the boundary conditions and evaluating the heat transfer coefficient and the adiabatic wall temperature based on the finite element method. The unsteady simulations were carried out using ANSYS-APDL for the proposed thermal model. The effect of lubricating oil and the contact resistance between guide and engine block and the thermal contact between exhaust valve and seat are included, as well as the differential displacement of both the guide and engine block walls due to high working temperature. The averaged values of heat transfer coefficient and adiabatic wall temperature used in the boundary conditions are shown to underestimate the temperature maps. The cyclic boundary conditions required more run time to reach the steady state and allowed better monitoring of the thermal process. The thermal contact resistance has the main contribution in the zone of valve-seat, whereas the resistance of oil film between the guide and stem valve is shown to affect mainly heat transfer coefficient. The obtained maps of temperature reveal the locations of maximum temperatures in the exhaust valve.