Experimental tests of steel balcony connections – part 2

Nucleus pressure was measured within porcine intervertebral discs (IVDs) with a novel in-fiber Bragg grating (FBG) sensor (0.4 mm diameter) and a strain gauge (SG) sensor (2.45 mm). To validate the accuracy of a new FBG pressure sensor designed for minimally invasive measurements of nucleus pressure. Although its clinical utility is controversial, it is possible that the predictive accuracy of discography can be improved with IVD pressure measurements. These measurements are typically obtained using needle-mounted SG sensors inserted into the nucleus. However, by virtue of their size, SG sensors alter disc mechanics, injure anulus fibers, and can potentially initiate or accelerate degenerative changes thereby limiting their utility particularly clinically. Six functional spinal units were loaded in compression from 0 N to 500 N and back to 0 N; nucleus pressure was measured using the FBG and SG sensors at various locations along anterior and anterolateral axes. On average maximum IVD pressures measured using the FBG and SG sensors were within 9.39% of each other. However, differences between maximum measured pressures from the FBG and SG sensors were larger (22.2%) when the SG sensor interfered with vertebral endplates (P < 0.05). The insertion of the FBG sensor did not result in visible damage to the anulus, whereas insertion of the SG sensor resulted in large perforations in the anulus through which nucleus material was visible. The new FBG sensor is smaller and less invasive than any previously reported disc pressure sensor and gave results consistent with previous disc pressure studies and the SG sensor. There is significant potential to use this sensor during discography while avoiding the controversy associated with disc injury as a result of sensor insertion.

Wearable devices and smart sport equipment are being increasingly used in amateur and professional sports. Smart sport equipment employs various sensors for detecting its state and actions. The correct choice of the most appropriate sensor(s) is of paramount importance for efficient and successful operation of sport equipment. When integrated into the sport equipment, ideal sensors are unobstructive, and do not change the functionality of the equipment. The article focuses on experiments for identification and selection of sensors that are suitable for the integration into a golf club with the final goal of their use in real time biofeedback applications. We tested two orthogonally affixed strain gage (SG) sensors, a 3-axis accelerometer, and a 3-axis gyroscope. The strain gage sensors are calibrated and validated in the laboratory environment by a highly accurate Qualisys Track Manager (QTM) optical tracking system. Field test results show that different types of golf swing and improper movement in early phases of golf swing can be detected with strain gage sensors attached to the shaft of the golf club. Thus they are suitable for biofeedback applications to help golfers to learn repetitive golf swings. It is suggested that the use of strain gage sensors can improve the golf swing technical error detection accuracy and that strain gage sensors alone are enough for basic golf swing analysis. Our final goal is to be able to acquire and analyze as many parameters of a smart golf club in real time during the entire duration of the swing. This would give us the ability to design mobile and cloud biofeedback applications with terminal or concurrent feedback that will enable us to speed-up motor skill learning in golf.

Paper presents theoretical analysis and results of experimental tests of three prefabricated balcony sets in natural scale with dimensions (width x length x height): 2.0 m x 2.78 m x 0.186 m (in a slope to 0.17 m) and one with dimensions: 2.0 m x 2.78 m x 0.2 m, consists of reinforced concrete slabs connected with each other with steel balcony connections. The impact of variable parameters (elongation of anchorage of balcony connections in ceiling slab, concreting of test elements in two stages, using of muffs as couplers to connect the longitudinal reinforcement bars in balcony sets and different height of the balcony slab) on the load bearing capacity of the elements are analysed. In the paper also the test stand was described. During the experimental tests, the crack morphology was determined, displacements and crack widths were measured. The paper contains a review of the scientific papers in the field of balcony connections.

The respiration rate (RR) is a vital sign in physiological measurement and clinical diagnosis. RR can be measured using stretchable and wearable strain gauge sensors which detect the respiratory movements in the abdomen or thorax areas caused by volumetric changes. In different body locations, the accuracy of RR detection might differ due to different respiratory movement amplitudes. Few studies have quantitatively investigated the effect of the measurement location on the accuracy of new sensors in RR detection. Using a stretchable and wearable inkjet-printed strain gauge (IPSG) sensor, RR was measured from five body locations (umbilicus, upper abdomen, xiphoid process, upper thorax, and diagonal) on 30 healthy test subjects while sitting on an armless chair. At each location, reference RR was simultaneously detected by the e-Health sensor, and the measurement was repeated twice. Subjects were asked about the comfortableness of locations. Based on Levene's test, ANOVA was performed to investigate if there is a significant difference in RR between sensors, measurement locations, and two repeated measurements. Bland-Altman analysis was applied to the RR measurements at different locations. The effects of measurement site and measurement trials on RR difference between sensors were also investigated. There was no significant difference between IPSG and reference sensors, between any locations, and between the two measurements (all p > 0.05). As to the RR deviation between IPSG and reference sensors, there was no significant difference between any locations, or between two measurements (all p > 0.05). All the 30 subjects agreed that diagonal and upper thorax positions were the most uncomfortable and most comfortable locations for measurement, respectively. The IPSG sensor could accurately detect RR at five different locations with good repeatability. Upper thorax was the most comfortable location.

The interaction properties between natural fiber and matrix play an important role in the mechanical performance of composite materials. The adhesion properties and the mechanical interaction between an Ichu fiber (Stipa obtusa) treated with sodium hydroxide and a cementitious matrix were studied by conducting experimental, numerical, and analytical pull-out tests. Through the experimental tests, the force–displacement curve for a fiber length embedded 5 mm deep in the cementitious matrix, maximum force, cohesive parameters, and the type of interface failure were determined. The results were used to calibrate the numerical and analytical models for different lengths of fiber (3, 5, 7, 9, and 11 mm) embedded in the cementitious matrix. The numerical model was implemented in the finite element software Abaqus CAE, and the analytical formulation considered the fiber embedded in a half-space continuous medium. From the experimental test, the force–displacement curve, interfacial shear strength of 0.124 MPa, and the softening type slip were obtained, despite obtaining the hardening-type slip in certain tests. The numerical and analytical results of the load–displacement curve closely approximate the experimental results. This study provides a numerical and analytical model to simulate the alkali-treated Ichu fiber–cementitous matrix interface.

Experimental Tests and Numerical Models of Double Side Non-Welded T RHS Truss Joints

The development of any manufacturing industry is not possible without the rational use of resources, so it is difficult to imagine modern production in which dosing is not used. The accuracy and productivity of dosing equipment is the basis of all known technological processes, since the quality of the final product depends on it. Belt feeders are small-sized and highly productive equipment, which is a vital necessity of continuous technological processes. The main requirement for a belt feeder is the maximum possible accuracy at an already set speed of movement of the load (line productivity). However, one should not forget about the peculiarities of the behavior of different types of products that can be weighed. The weighing accuracy of a belt feeder also depends on its design features, namely on the accuracy of the drive, tension or support rollers, the quality of the belt, and the design of the strain gauge assembly. Experiments on calibration in statics and the behavior of the feeder in dynamics will allow us to evaluate possible behavior options during operation in real conditions. The purpose of the experiments is the initial setup of the experimental setup for further research into the relationship of belt speed / product type / dosing accuracy. The article describes the structure of the experimental setup, the composition of the measuring part of the laboratory setup, as well as the methodology for collecting and processing experimental data. The main attention of the experimental part is paid to the dynamic mode of operation and its impact on the strain gauge assembly. The main issues that arise in the dynamic mode are outlined, namely Special attention is paid to the dynamic feed mode, in which the loads on the measuring element – the strain gauge sensor – change. The key problems that arise in this mode are indicated: fluctuations in the output signal (change in mass values), the influence of the product movement speed, the physical and mechanical characteristics of the product. The results of the experiments are the voltage/mass curves in the static mode and voltage/mass/speed in the dynamic mode, a comparative analysis of the measurement results. According to the research results, an adaptive control system for a belt feeder will be developed, which can be implemented in all industries where belt feeders are used.

Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoimpedance characteristics that can be tapped to sense strain. This paper presents the details of novel foil-based strain gauge sensor configurations comprising carbon nanotube yarn. The strain gauge sensors were designed considering parametric studies that maximize the sensitivity of the sensor to mechanical loading. The fabrication details of the strain gauge sensors that exhibit the highest sensitivity, based on the modeling results, are described including the materials and procedures used in the first prototypes. Details of the calibration of the strain gauge sensors are also provided and discussed in the context of the electromechanical characterization when bonded to metallic specimens. This characterization included studying their response under monotonic and cyclic loading. It is shown that these strain gauge sensors consisting of carbon nanotube yarn are sensitive enough to capture strain. Previous modeling results indicated the potential of the strain gauges to exhibit gauge factors higher than those of metallic foil strain gauges.

The issue of dosing and weighing materials will remain relevant for many years to come. The need to measure a required amount of material can be found in almost every area of activity – from microscopic substances to massive materials, compounds, and aggregates. Therefore, the search for the most optimal and efficient solutions in this field remains a constant and pressing task. The primary characteristics of a weighed material are the accuracy of its weighing and the speed of the weighing process. The presented gravitational feeder is a high-performance device that ensures continuous material weighing in flow, without interruptions or stoppages. However, its weighing accuracy depends on many design features, especially the main working body – the curvature radius that receives the material flow. Accordingly, conducting experiments to calibrate the gravitational feeder allows one to understand how static and dynamic operating conditions affect measurement accuracy, which can characterize the system’s behavior during real-world operation. The aim of the study is to configure an experimental setup for conducting tests to optimize the design, determine the optimal parameters of the curved working body, and identify the most effective tilt angle of the working element relative to the vertical axis. This work provides a detailed description of the construction of the experimental setup, methods of material feeding, parameters of the variable tilt angle of the feeder’s working plane, as well as the methodology for collecting and processing experimental data. Special attention is paid to the dynamic feeding mode, in which the load on the measuring element – the strain gauge sensor – changes. Key issues arising in this mode are identified: signal fluctuations, the influence of the tilt angle, and the physical and mechanical properties of the bulk material. A comparative analysis of measurement results under different conditions was conducted, calibration curves were constructed, and the dependencies between mass and voltage were interpreted. Based on the results of the study, recommendations were developed for adjusting the feeder control system considering changes in technological conditions. The methodology can be implemented in automated production lines, particularly in the food, chemical, and pharmaceutical industries. The presented data have practical value for process engineers, equipment developers, and researchers in the field of conveying and dosing systems.

The market of LNG (Liquefied Natural Gas) carrier is remarkably expanded in the last four or five years, and lots of LNG vessels are being built in many shipyards in the world. Membrane-type MARK-III LNG CCS (Cargo Containment System) is used more and more in the construction of LNG carrier, and it has already taken considerable market share in the business of LNG vessel. No matter how many researches have been carried out on the structure of LNG CCS, most of them are mainly focused on its macroscopic behaviors, e.g. structural response of LNG CCS under sloshing load. MARK-III secondary barrier is a matter of primary concern recently, and as already known, its major function is to protect the inner hull structure from the leakage of LNG when the primary barrier of corrugated membrane fails. A closed boundary of secondary barrier for liquid tightness is mainly sustained by the boding between flexible and rigid triplexes, where the adhesive material such as epoxy green glue is applied. The thickness of adhesive glue is about 0.4mm which is extremely thin compared with those of the other structural components of MARK-III CCS. The conventional macroscopic approach hardly gives proper description about the structural behavior of secondary barrier which requires much finer representation with the resolution of glue thickness. Most recently, even though there is an example of research on the structural responses of MARK-III secondary barrier by carrying out structural analysis using microscopic approach, it still is necessary to verify the results of structural analysis base on the experimental evidences. This research deals with an experimental study on the structural behavior of the secondary barrier of MARK-III LNG CCS. The full-scale specimen of MARK-III CCS is prepared and installed in cryogenic chamber which is quite large enough to completely enclose the specimen. As the actual secondary barrier is loaded mainly with thermal loading due to cryogenic temperature and mechanical loading due to hull deformation, the specimen undergoes cryogenic temperature maintained by the chamber and mechanical loading given by the actuator of testing machine. The structural response of secondary barrier in the specimen is maintained and controlled in such a way that the response is almost the same as that of actual secondary barrier in LNG CCS. Through the intensive study on the type and size, the specimen is so designed as to sufficiently realize the structural behavior of the secondary barrier in the actual operating condition. Since the strain gauge is elaborately installed into the thin layer of adhesive glue in the secondary barrier, it is possible to measure its precise response and to capture the realistic structural behavior of the glue. FBG (Fiber Bragg Grating) sensor is also installed in the same specimen, and the structural response of the secondary barrier is measured simultaneously, which provides data of comparison to confirm the reliability of experimental results. It is necessary to verify the performance and feasibility of the strain gauge and FBG sensor prior to actual application into the specimen, because the strain gauge and FBG sensor work in extremely thin layer under cryogenic environment. Therefore, simple tensile test is carried out, and the strain gauge and FBG sensor are examined. During cooling down process, thermal loading is increased until the temperature of secondary barrier reaches −110°C, which is maintained for a few hours to stabilize the structural response of specimen. Continually, the 4-point bending test is carried out to give additional mechanical loading which is monotonously increased until the loading reaches the ultimate strength. The strain gauge and FGB sensor measure and record the strain at each testing location during the whole process of experiment. The specimen of EC (Conventional Epoxy) glue has the smallest ultimate strength, but nevertheless it has sufficient safety factor with respect to the level of loading in actual vessel, and the EHP (Epoxy Glue with the Treatment of Hot Pad) and PU (Polyurethane) glues have much more. The experiment is simulated numerically using FEM. The material data are directly obtained through various material tests. Microscopic approach is adopted, and therefore extremely fine mesh model of which element size is almost equal to glue thickness near the secondary barrier is developed, which makes it possible to represent realistic structural behavior of adhesive glue precisely. The loading and boundary conditions are carefully arranged to embody the experimental circumstances correctly. Finally, it is possible to estimate the degree of discrepancy between the results of experiment and numerical simulation, and the correlation factor can be obtained by studying the discrepancy. The correlation factor is the final result in this research, which can be applied to the structural analysis for actual secondary barrier of MARK-III LNG CCS and improve the results of the analysis.

Loading and fracture response of CFRP-to-steel adhesively bonded joints with thick adherents – Part I: Experiments

Ultrasonic impedance matching from solids to gases: Lynnworth, L.C.Institute of Electrical and Electronic Engineers. Transactions on Sonics and Ultrasonics, SU-12, No. 2, 37 (1965)

Experimental and statistical study on the irregularity of carbonation depth of cement mortar under supercritical condition

Global analysis of each structure is conducted for assumed model of this structure. Models of structures are nowadays much improved — many influences, previously omitted, are taken into account, as: spatial structure behaviour, influence of floors and walls, imperfections, and lastly real behaviour of frame joints (semi-rigid joints). Global analysis with account of semi-rigid joints is troublesome because of non-linear joint characteristics. For plane building frames, main joints characteristic is moment-rotation relationship (M-ϕ curve). Analytical modelling of these curves is based on experimental tests conducted mainly on isolated joints models, consisted of short column and beam elements connected by joint [1], [2], [3]. For many years, a lot of joint experimental tests were conducted, data bases of joints test results were created (e.g. SERICON, SCDB) and analytical models of joints were developed (linear, multilinear, polynomial, power, exponential etc.). These models, as well as these obtained using “component method” included in Annex J of EC 3 [4], are used in global frame analysis. Only one objective way for verification joints models seems to be experimental test of frames in natural scale [5], [6], [7]. Because of high cost of such tests, they are made very seldom. The paper deals with steel and composite, sway frame test conducted in natural scale on site.

The paper provides the results of experimental and theoretical test of a wavy fin and tube heat exchanger used to cool air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000&amp;lt;Re&amp;lt;4500 of the Reynolds number applying LMTD-LMED methodology, determined the dependency of the heat transfer coefficient on the supplied air flow rate with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating and 6 heat exchangers in cooling mode. After processing the results of the experimental tests, empirical equation defining the characteristics of the heat transfer coefficient of all heat exchangers were derived. The maximum heat transfer coefficient deviation is 11.6 percent. The correction factor of the wet fin (Lewis number) depending on the number of Reynolds, which ranges from 0.75 to 1.1 also is determined. Maximum capacity deviation equals 3.7 percent. The obtained equations can only be applied to a certain group of heat exchangers (with the same shape of fins or the distance between the tubes). The results of the experimental test and simulation with ANSYS program are compared and the heat transfer coefficients vary from 6.5 to 11.4 percent.