Linear Voltage Displacement Transducers Research Articles

Enhancing poplar-wood properties through nano-silica fortified polyvinyl-acetate impregnation

ABSTRACT The effects of pressure impregnation of nano-SiO2 fortified polyvinyl acetate (PVAc) in plantation-grown poplar-wood (Populus deltoides) on a few important physical properties, such as density, water absorption, swelling (tangential and volumetric) and surface hardness, were evaluated. Real-time tangential swelling, swelling rates and anti-swelling efficiency of the nano-wood composites were also determined using a customized linear voltage displacement transducer (LVDT)-based swell-o-meter. The dynamic light scattering technique was used to evaluate the dispersion stability and average particle size of the nano-SiO2 fortified polyvinyl acetate before impregnating in wood. The changes in the microstructure, crystallinity, and chemical interactions of nanoparticles, resin and wood elements that occurred in nano-wood composites were studied using scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy techniques. Wood impregnated with 3% nano-SiO2 fortified 20% polyvinyl acetate exhibited the lowest tangential swelling after 2 h of water immersion, while the highest anti-swelling efficiency after saturation was achieved with 3% nano-SiO2 fortified 15% polyvinyl acetate. Mechanical test results also indicated improvement in the end- and side-surface hardness of the wood impregnated with 3–5% nano-SiO2-fortified 20% PVAc. This study provides valuable insights into the potential of using fast-grown low-density poplar-wood impregnated with nano-SiO2 fortified PVAc for various value-added interior applications.

Analytical and experimental study of shape memory alloy reinforcement on the performance of butt-fusion welded joints in high-density polyethylene pipe

In this article, a shape memory alloy wire is employed as confinement to enhance the flexural rigidity of the butt-fusion welded joints in the high-density polyethylene pipes. To this end, analytical and experimental studies are considered, when the shape memory alloy wire is wrapped around a butt-fusion joint and an internal pressure is applied to the high-density polyethylene pipe. To investigate the efficiency of shape memory alloy wire jacket on the performance of butt-fusion welded joint in high-density polyethylene pipe, two cases of perfect butt-fusion joint and imperfect butt-fusion joint are tested. The influence of the number of shape memory alloy wire jacket on the high-density polyethylene pipe joints as well as the effect of different flexural rigidities of the wire and high-density polyethylene pipe, and different diameters are evaluated. The deformation is measured using linear voltage displacement transducer and digital image correlation analysis at different location of the pipe length. In addition, radial strain of the pipes due to bulging is measured by electronic resistance strain gauges. Results show that the shape memory alloy wire jacket has a significant effect (33%) on enhancing imperfect butt-fusion welded joint of high-density polyethylene pipes.

Experimental Study for Structural Behaviour of Precast Lightweight Panel (PLP) Under Flexural Load

Precast lightweight concrete slab is first fabricated in workshop or industrial before construction and then transported to site and installed by skilled labour. It can reduce construction time by minimizing user delay and time for cast-in-situ to increase workability and efficiency. is environmental friendly and helps in resource reduction. Although the foamed concrete has low compressive strength compared to normal weight concrete but it has excellent thermal insulation and sound absorption. It is environmental friendly and helps in resource reduction. To determine the material properties of foamed concrete, nine cubes and six cylindrical specimens were fabricated and the results were recorded. In this study, structural behaviour of precast lightweight panel (PLP) with dry density of 1800 kg/m3 was tested under flexural load. The results were recorded and analysed in terms of ultimate load, crack pattern, load-deflection profiles and strain distribution. Linear Voltage Displacement Transducers (LVDT) and strain gauges were used to determine the deflection and strain distribution of PLP. The theoretical and experimental ultimate load of PLP was analysed and recorded to be 70 and 62 kN respectively, having a difference of 12.9%. Based on the results, it can be observed that PLP can resist the adequate loading. Thus, it can be used in precast industry for construction purposes.

Experimental study of laminated glass window responses under impulsive and blast loading

Laminated glass panes are widely adopted as blast-resistant glass windows to mitigate the hazard from ejecting fractured glass fragments. The response of laminated glass windows under blast loads is often predicted by equivalent static analysis or simplified equivalent single degree of freedom (SDOF) analysis. The equivalent SDOF and equivalent static analyses are also respectively adopted in UFC and ASTM design guide for glass window designs. Owing to the inherent problems, the SDOF analysis can only predict the global responses of glass windows and the predictions are not necessarily always satisfactory. Therefore the accuracy and applicability of the SDOF analysis is sometimes questioned. Often numerical simulations and/or experimental tests have to be carried out for reliable predictions of laminated glass window responses to blast loads. In this study, experimental tests on laminated glass windows subjected to impact and blast loads were carried out to evaluate the accuracy of available analyses and design methods. Pendulum impact tests were conducted first on laminated panes of various thicknesses. Full-scale field blast tests were performed on laminated glass windows of dimension 1.5 m × 1.2 m. Glass pane deflections were monitored by mechanical linear voltage displacement transducer (LVDT) and high-speed cameras. The responses of the tested windows are compared with the estimations of SDOF models and design standards in this paper. Available blast testing data by other researchers are also included together with the current testing data to evaluate the accuracy of the SDOF and equivalent static analyses defined in the design guides. The adequacy of these simplified approaches in predicting laminated glass window responses to blast loads is discussed.

Shear behaviour of prestressed steel fibre concrete box-beams

Six full-scale prestressed concrete box-beams are tested to study the effects of steel fibres on the increase in shear strength of beams. Beams are cast with no traditional transverse steel reinforcement. The amount of steel fibres and shear span-to-effective depth ratio are the main variables studied. The beams are subjected to concentrated vertical loads up to their maximum shear capacity using two actuators in load and displacement control mode. During the load tests linear voltage displacement transducers (LVDTs) are used to measure displacements at several critical points on the web in the end zone of the beams. Several LVDTs are also placed under the beams at the points of loading to measure the actual total and net displacements of the beams. From the load tests it is observed that the shear capacities of the beams increase with an increase in the amount of steel fibres and decrease as the shear span-to-effective depth ratio increases.

Reverse shoulder arthroplasty glenoid fixation: is there a benefit in using four instead of two screws?

To allow osseous integration to occur and thus provide long-term stability, initial glenoid baseplate fixation must be sufficiently rigid. A major contributing factor to initial rigid fixation is baseplate screw fixation. Current baseplate designs use a 4-screw fixation construct. However, recent literature suggests adequate fixation can be achieved with fewer than 4 screws. The purpose of the present study was to determine whether a 4-screw construct provides more baseplate stability than a 2-screw construct. A flat-backed glenoid baseplate with 4 screw hole options was implanted into 6 matched pairs of cadaver scapulas using standard surgical technique. Within each pair, 2 screws or 4 screws were implanted in a randomized fashion. A glenosphere was attached allowing cyclic loading in an inferior-to-superior direction and in an anterior-to-posterior direction. Baseplate motion was measured using 4 linear voltage displacement transducers evenly spaced around the glenosphere. There was no statistical difference in the average peak central displacements between fixation with 2 or 4 screws (P=.338). Statistical increases in average peak central displacement with increasing load (P<.001) and with repetitive loading (P<.002) were found. This study demonstrates no statistical difference in baseplate motion between 2-screw and 4-screw constructs. Therefore, using fewer screws could potentially lead to a reduction in operative time, cost, and risk, with no significant negative effect on overall implant baseplate motion.

Modeling, validation and analysis of mechanical stress generation and dimension changes of a pouch type high power Li-ion battery

Mechanical stress is generated in electrode particles of a Lithium ion Polymer Battery (LiPB) during charge and discharge. The stress can cause cracks and fractures in the solid particles over time when cells are cycled, which leads to a disorder and a fracture of the electrodes. In order to understand the mechanism, a stress model for a pouch type high power LiPB is developed based on electrochemical and thermal model, where the stress induced by the ion concentration in the electrode particles is considered. The stress in the particles causes changes in the electrode volumes and leads to changes in the thickness of a battery cell, which is measured using a device designed with two linear voltage displacement transducers (LVDT). This model is validated against experimental data obtained from a pouch cell. Analysis shows that the magnitude of stress depends upon locations and C rate, while the thickness of a single cell is mainly affected by the state of charge (SOC), but not C rate.

Design and analysis of a novel mechanical loading machine for dynamic in vivo axial loading

This paper describes the construction of a loading machine for performing in vivo, dynamic mechanical loading of the rodent forearm. The loading machine utilizes a unique type of electromagnetic actuator with no mechanically resistive components (servotube), allowing highly accurate loads to be created. A regression analysis of the force created by the actuator with respect to the input voltage demonstrates high linear correlation (R(2) = 1). When the linear correlation is used to create dynamic loading waveforms in the frequency (0.5-10 Hz) and load (1-50 N) range used for in vivo loading, less than 1% normalized root mean square error (NRMSE) is computed. Larger NRMSE is found at increased frequencies, with 5%-8% occurring at 40 Hz, and reasons are discussed. Amplifiers (strain gauge, linear voltage displacement transducer (LVDT), and load cell) are constructed, calibrated, and integrated, to allow well-resolved dynamic measurements to be recorded at each program cycle. Each of the amplifiers uses an active filter with cutoff frequency at the maximum in vivo loading frequencies (50 Hz) so that electronic noise generated by the servo drive and actuator are reduced. The LVDT and load cell amplifiers allow evaluation of stress-strain relationships to determine if in vivo bone damage is occurring. The strain gauge amplifier allows dynamic force to strain calibrations to occur for animals of different sex, age, and strain. Unique features are integrated into the loading system, including a weightless mode, which allows the limbs of anesthetized animals to be quickly positioned and removed. Although the device is constructed for in vivo axial bone loading, it can be used within constraints, as a general measurement instrument in a laboratory setting.

A cadaver model evaluating femoral intramedullary reaming: a comparison between new reamer design (Pressure Sentinel) and a novel suction/irrigation reamer (RIA)

Objective To compare the intramedullary pressures developed during reaming of cadaveric femurs with the Synthes Reamer/Irrigator/Aspirator (RIA) reamer and the Zimmer Pressure Sentinel (PS) reamer, controlling for the force and speed of reaming. Method Fifteen matched pairs of frozen unpreserved femurs were used in the study. Two pressure transducers and two thermocouples were screwed into holes drilled into the femoral shaft. The femurs were stabilized in the vertical position by mechanically attaching them to a custom jig equipped with a load cell to detect the vertical component of force applied to the reamer. Proximally a linear voltage displacement transducer (LVDT) was attached to the reamer to record the continuous position of the reamer. All femurs were reamed to a diameter 2 mm larger than the narrowest point of the canal. Proximal and distal pressures, proximal and distal temperatures, applied vertical force and displacement were measured continuously throughout the reaming process. Maximum and minimum, and average proximal and distal pressures for each reamer were obtained and compared using paired t-tests. Averages were also calculated and compared in the same manner. A p-value of <0.05 was considered statistically significant. Results The maximum, minimum and average intramedullary pressures during reaming were significantly lower with the RIA system than the PS reamer. In general, the pressures produced by the RIA system were consistently below atmospheric pressure for the majority of the reaming time. This was not true for the PS system. No appreciable temperature changes were observed during any of the trials. Conclusion The RIA reaming system significantly reduces the intramedullary pressures produced during the reaming process compared to the PS reaming system.

Muscle moment arms of the gibbon hind limb: implications for hylobatid locomotion

Muscles facilitate skeletal movement via the production of a torque or moment about a joint. The magnitude of the moment produced depends on both the force of muscular contraction and the size of the moment arm used to rotate the joint. Hence, larger muscle moment arms generate larger joint torques and forces at the point of application. The moment arms of a number of gibbon hind limb muscles were measured on four cadaveric specimens (one Hylobates lar, one H. moloch and two H. syndactylus). The tendon travel technique was used, utilizing an electro-goniometer and a linear voltage displacement transducer. The data were analysed using a technique based on a differentiated cubic spline and normalized to remove the effect of body size. The data demonstrated a functional differentiation between voluminous muscles with short fascicles having small muscle moment arms and muscles with longer fascicles and comparatively smaller physiological cross-sectional area having longer muscle moment arms. The functional implications of these particular configurations were simulated using a simple geometric fascicle strain model that predicts that the rectus femoris and gastrocnemius muscles are more likely to act primarily at their distal joints (knee and ankle, respectively) because they have short fascicles. The data also show that the main hip and knee extensors maintain a very small moment arm throughout the range of joint angles seen in the locomotion of gibbons, which (coupled to voluminous, short-fascicled muscles) might help facilitate rapid joint rotation during powerful movements.

Static and dynamic Young’s moduli of chalk from the North Sea

We present results from a study of dynamic and static Young’s moduli of North Sea chalk based on laboratory tests on both dry and water-saturated chalk. We obtained static moduli by using both strain gauge and linear voltage displacement transducer (LVDT) measurements. We investigated the influence of pore fluid on static and dynamic Young’s moduli and evaluated the two methods for obtaining static Young’s modulus. We obtained good agreement between dynamic and static Young’s moduli from strain gauge measurements on dry chalk, but for water-saturated chalk the dynamic Young’s modulus was larger than the measured static Young’s modulus. This difference may be caused in part by the influence of the difference in frequencies of static and dynamic measurements. Another reason for the observed difference may be a practical experimental problem that causes the measured static Young’s modulus for water-saturated chalk to be lower than the true modulus. When we compared dynamic Young’s modulus for dry chalk with that for water-saturated chalk, the dry modulus was larger than the water-saturated modulus, probably owing to shear weakening of the chalk. Young’s modulus from LVDT measurements does not relate to dynamic Young’s modulus for dry or water-saturated rock because the LVDT is not able to accurately measure the small deformations of the samples during loading at relatively low stresses.

DYNAMICS OF FRUIT GROWTH IN 'CONFERENCE' PEAR AS AFFECTED BY ROOT PRUNING, IRRIGATION AND CLIMATIC CONDITIONS

In 2002, daily fluctuations in trunk diameter and fruit diameter on ‘Conference’ pear trees were measured with linear voltage displacement transducers. On an average sunny day in July, trunk diameter started to decrease around 10 a.m. when air temperature increased. This continued until 8 p.m. when air temperature started to decline. Fruit diameter growth of ‘Conference’ ceased as soon as trunk diameter started to decrease and resumed immediately after trunk diameter started to increase. When fruit growth took place, the rate of diameter increase was fairly constant and was ~ 0.04 mm/h. Root pruning without irrigation significantly affected tree growth but not fruit growth. Fruit size increase was almost linear from early May up to harvest at the beginning of September and averaged 3.9 mm/week. Relationships between fruit growth, climatic condition, soil water availability and cultural practices are discussed

Pavement Deformation Monitoring in a Rolling Load Facility

This paper describes work undertaken to measure deformation of a pavement within the Newcastle University Rolling Load Facility (NUROLF). Precise three dimensional measurements of the pavement have been produced from stereo‐imagery taken with diVerent cameras, using both analytical and digital photogrammetric instrumentation. The photogrammetric measurements, and those from the existing system consisting of an array of linear voltage displacement transducers, have been compared with measurements produced using a digital level. Encouraging results have been achieved and photogrammetry has been shown to be capable of producing a similar accuracy to the existing system. There are many advantages associated with a photogrammetric survey but attempts to establish a permanent, automated photogrammetric system for the rolling load facility at a reasonable cost have so far been unsuccessful. It is anticipated that, with the falling cost of high resolution digital sensors, such a system will soon be possible.

Temperature, but not Growth Regulators, Influences Diurnal Stem Elongation Rhythms in Zinnia

Experiments were conducted to determine the effects of treatment with gibberellic acid (GA) on changes in diurnal growth rhythms caused by maturation and day/night temperature differential (DIF) in zinnia (Zinnia elegans Jacq. `Pompon'). Plants were treated with GA3 or with the GA biosynthesis inhibitor daminozide under three DIF regimes (+5 DIF: 21 °C DT/16 °C NT; 0 DIF: 18.7 °C constant; –5 DIF: 16.5 °C DT/21.5 °C NT), each with a daily average temperature of 18.7 °C, at two developmental stages: stage 1, the period of vegetative growth before flower bud formation; and stage 3, growth just before anthesis. Instantaneous stem elongation rates (SER) were measured using linear voltage displacement transducers. The DIF regime, as has been previously shown, influenced stem elongation primarily by altering the size of an early morning peak in SER; peak height increased as DIF became more positive. GA3 increased SER throughout the diurnal period with a proportionately larger effect on nighttime growth. Conversely, daminozide decreased SER more or less equally throughout the diurnal period. Neither GA3 or daminozide transformed growth patterns to match those of positive or negative DIF plants, but instead simply increased or decreased growth amplitude. Furthermore, neither growth regulator altered the basic diurnal SER pattern at any DIF, or influenced the observed shift to greater nighttime growth as plants matured from stage 1 to stage 3. The results suggest that neither the effects of DIF, or the age-related shift in diurnal growth distribution can be explained by changes in total availability of GA in the plant. Chemical name used: mono (2,2-dimethylhydrazide) butanedioic acid (daminozide).

In-situ measurement of the thickness changes associated with cycling of prismatic lithium ion batteries based on LiMn 2O 4 and LiCoO 2

An in-situ method for measuring the variation of battery stack thickness employing a linear voltage displacement transducer device is described. Prismatic lithium ion batteries based on the cathode active materials LiMn 2O 4 and LiCoO 2 are investigated. These batteries comprise multiple, parallel-connected bi-cells. The manganese system reveals only minor thickness variations during a single low rate, charge-discharge cycle. The maximum thickness change for the approximate 9 mm stack amounted to only 20 μm corresponding to less than a 0.2% overall variation. We determine that the battery stack is at its thickest at around 45% state of charge and at its thinnest in the fully discharged state. For the cobalt battery, more significant thickness variations are determined. This behavior is consistent with the concurrent expansion of both the anode and cathode lattices during the battery charging process. The thickness changes are shown to be reversible within a single charge-discharge cycle. As a function of battery state-of-charge, the dimensional variations were clearly demonstrated to be non-linear. The cobalt oxide battery stack was at its thickest when fully charged and at its thinnest when fully discharged. At the fully charged condition the 8.8 mm prismatic stack was shown to increase in thickness (over the fully discharge case) by about 140 μm stack representing a 1.6% overall expansion.

Temperature and Developmental Stage Influence Diurnal Rhythms of Stem Elongation in Snapdragon and Zinnia

Stem elongation rates (SERs) of `Giant Tetra' snapdragon (Antirrhinum majus L.) and `Pompon' zinnia (Zinnia violacea Cav.) were determined in three temperature regimes in which differentials had been established between day and night temperature. The differentials [expressed as day temperature - night temperature (DIF)] were +5 DIF, 21 °C day/16 °C night; 0 DIF, 18.7 °C constant; and -5 DIF, 16.5 °C day/21.5 °C night; daily average 18.7 °C. In each regimes SERs were determined for three developmental stages—vegetative, visible bud, and preanthesis. SER was measured in controlled-environment chambers under 13-hour day/11-hour night photoperiods using linear voltage displacement transducers. Snapdragon and zinnia displayed rhythmic patterns of growth with strikingly different characteristics. SER for snapdragon consisted of a large peak in growth at the day/night (D/N) transition followed by a minimum in SER at the night/day (N/D) transition. The pattern did not change through development. In contrast the SER pattern changed significantly in zinnia. At the vegetative stage, diurnal SER was dominated by a large peak after the N/D transition [an early morning peak (EMP)]. At the later growth stages, the EMP remained visible, but the proportion of growth occurring at night increased. SER was rhythmic in both species for a limited period in continuous light and constant temperature. Zinnia displayed a stronger endogenous rhythm of SER than snapdragon. In both species, only day period growth was affected by DIF. The size of EMPs in both species increased under positive DIF and decreased under negative DIF, resulting in the overall DIF effect on plant height (a progressive increase in total diurnal elongation as DIF increased from -5 to +5). Internode lengths for snapdragon and zinnia were similar for plants grown to full flower at constant 17, 20, or 23 °C (0 DIF), indicating that DIF—not average daily, night, or day temperature—is a major determinant of extension growth.

Experimental study of the thermoforming of a blend of styrene‐butadiene copolymer with polystyrene

AbstractMaterial characterization and thermoforming studies were completed using a blend of a styrene‐butadiene copolymer with polystyrene used commercially for the production of cups and dishes. This composition was thermoformed between 135 and 152°C. Studies consisted of forming 30‐mil and 46‐mil sheets at 130, 140, and 150°C at three evacuation rates in an aluminum cylindrical mold. The mold was instrumented with a pressure transducer to follow the change in pressure during forming and two Linear Voltage Displacement Transducers, which served as mold wall contact sensors. The results indicated that the process is extremely rapid (0.25–0.60 sec) for the high and medium evacuation rates. The process was found to require a low pressure differential for forming (typically &lt;4 psi). The final part thickness distribution and extension ratio data indicated that the material stretches into the approximate shape of a spherical segment, contacts the bottom/ center of the mold, contacts the sides, and finally stretches into the corners. The tensile strength and modulus of elasticity measurements of the final part were slightly less than the original sheet properties for samples measured in the machine direction but slightly greater for samples taken in the transverse direction. However, the percent elongation at break increased significantly in both the machine and transverse directions.

An experimental design for laboratory simulation of periglacial solifluction processes

An experimental slope of gradient 12° was constructed, comprising two 5 m × 2 m × 0·3 m contiguous strips of natural soils. Soil freezing and thawing took place from the surface downwards in an open hydraulic system, water being supplied at the base of each soil. Thermal conditions, porewater pressures and soil displacements were monitored using a PC-based logging system, with readings taken at half-hourly intervals. Soil surface displacements due to frost heave and solifluction were measured using linear voltage displacement transducers. Soil temperatures were determined using thermistors and semiconductor temperature sensors. Antifreeze-filled miniature ceramic-tipped pressure transducers were used to determine porewater pressure variations. The potential of this experimental approach for precise monitoring of mass movement processes associated with thawing of ice-rich soils is demonstrated.

An experimental design for laboratory simulation of periglacial solifluction processes

An experimental slope of gradient 12° was constructed, comprising two 5 m × 2 m × 0·3 m contiguous strips of natural soils. Soil freezing and thawing took place from the surface downwards in an open hydraulic system, water being supplied at the base of each soil. Thermal conditions, porewater pressures and soil displacements were monitored using a PC-based logging system, with readings taken at half-hourly intervals. Soil surface displacements due to frost heave and solifluction were measured using linear voltage displacement transducers. Soil temperatures were determined using thermistors and semiconductor temperature sensors. Antifreeze-filled miniature ceramic-tipped pressure transducers were used to determine porewater pressure variations. The potential of this experimental approach for precise monitoring of mass movement processes associated with thawing of ice-rich soils is demonstrated.

In Situ Measurements of the Thickness Changes for a Lithium Rechargeable Cell Based on a V 6 O 13 Composite Electrode during Lithium Insertion and Extraction

An in situ technique utilizing a linear voltage displacement transducer device for investigating the thickness changes occurring during the cycling of a lithium insertion type rechargeable cell based on a composite cathode is described. We believe the method is generally applicable to other battery systems which undergo expansion/contraction effects during normal operation. During cell discharge there is a gradual decrease in cell thickness, while the converse is true during the subsequent charging process. The thickness changes are highly reversible over the single cycle considered. The variation of cell thickness was approximately linear with depth of discharge. For the cell in the fully discharged state, the overall thickness change of the active cell components was ∼6%. When the thickness variation associated with the lithium electrode is excluded from the calculations, the cathode increases in thickness during cell discharge and decreases during cell charge. The changes are consistent with the literature‐reported cathode unit cell expansion/contraction effects caused by the lithium insertion/extraction processes.