Deflection Tests Research Articles

Enhancement of surface & bulk mechanical properties of Flax reinforced composites with different carbon allotropes

In this study, the effects of carbon allotropes on surface and bulk properties of flax fiber-reinforced composites (FFRC) are examined. Flax reinforced composites were prepared using two different nanofillers as FG & GO. Various surface and bulk properties like heat deflection, hardness, impact & tensile-strength & flexural-strength tests were performed. Addition of nanofillers like GO/ FG enhances the entire surface and bulk properties. Experimental values manifests that at 0.75 wt% of GO, the FFRC has better impact and tensile-strength, hardness, flexural-strength and heat deflection that is 30%, 15%, 18%, 20% and 13% respectively. But for FG as nanofillers, have manifested better properties when contrast to the GO and pure the FFRC. The properties like impact & tensile-strength, hardness, heat deflection & flexural-strength test are improved by 36%, 18%, 22%, 22% and 15% respectively. It was found that, after the addition of optimum weight % of nano-fillers, there was a degradation of surface and bulk properties.

Anaology of Jute Fiber with Mud Crab Shell and Mussels Shell Powder Filler Reinforced Isopthalic Polyester Resin Based Composites

Jute fibers are totally biodegradable and recyclable substances, i.e., environmentally friendly substances. The contemporary annual global production of jute fiber is ready 3. 2 million tons and used for diverse packages. Various research is being accomplished to discover a suitable substitute for the nonbio degradable plastic strengthened composites, which has a negative effect at the environment. The mercerization technique is executed the use of 8% of sodium in water to form the sodium hydroxide (NaOH). The property of the fabric is similarly promoted with the aid of adding mud crab shell powder and mussels shell powder all through the hand moulding process. The composite fabric is evolved with the assist of isophthalic polyester resin with 2% of accelerator and hardener used at the side of it. Experiments are executed as according to ASTM requirements to discover the mechanical properties. In addition to mechanical properties HDT(Heat Deflection Test) and rate of burning test are done. With help of the studies and study,Jute fabric mat can be used as an alternate for plastic components (non bio degradable).

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for Supercritical Carbon Dioxide Turbomachinery: Design and Proof of Concept Testing

Abstract The following paper presents a new type of gas lubricated thrust bearing that utilizes additive manufacturing or also known as direct metal laser melting (DMLM) to fabricate the bearing. The motivation for the new bearing concept is derived from the need for highly efficient supercritical carbon dioxide (sCO2) turbomachinery in the mega-watt power range. The paper provides a review of existing gas thrust-bearing technology, outlines the need for the new DMLM concept, and discusses proof-of-concept testing results. The new concept combines hydrostatic pressurization with individual tilting pads that are flexibly mounted using hermetic squeeze film dampers (HSFD) in the bearing-pad support. This paper describes the thrust-bearing concept and discusses the final design approach. Proof-of-concept testing in air for a 6.8 in. (173 mm) outer diameter thrust gas bearing was performed; with thrust loading, up to 1500 lbs (6.67 kN) and a thrust runner speed of 10krpm (91 m/s tip speed). The experiments were performed with a bent shaft resulting in thrust runner axial vibration magnitudes of 2.9 mils (74 μm) p-p and dynamic thrust loads of 270 lbs (1.2 kN) p-p. In addition, force deflection characteristics and stiffness coefficients of the bearing system are presented for an inlet hydrostatic pressure of 380 psi (2.62 MPa). Results at 10 krpm show that the pad support architecture was able to sustain high levels of dynamic misalignment equaling 6 times the nominal film clearance while demonstrating a unit load-carrying capacity of 55 psi (0.34 Mpa). Gas-film force deflection tests portrayed nonlinear behavior like a hardening spring, while the bearing pad support stiffness was measured to be linear and independent of gas film thickness.

On the Relation between Strength and Stiffness of Cable Tray

In order to realize the optimal design of the cable supporting system for the purpose of material saving and energy saving and green manufacturing, the strength-stiffness ratio is proposed in the paper in nondimensional form, which defines quantitatively the relation between the static load strength and stiffness of the cable tray. On the premise of ensuring service safety, the correlation between the strength and stiffness of the cable tray under static load is discussed extensively through the theoretical analysis of the mechanical model. The weakest link in the carrying capacity of the cable tray as well as the issue that needs to pay attention is proposed in the process of design and the test of the cable tray. A reasonable strength-stiffness ratio will help to make full use of the potential of material strengths. The value of the strength-stiffness ratio is obtainable by means of the finite element method or by the loading test of the cable tray. It is shown through the analysis that the value of the strength-stiffness ratio being setting in the range close to but less than 1 will make comparatively reasonable material utilization and will help the deflection test going smoothly to obtain a relatively safer allowable working load for the cable tray.

Deflection test and modal analysis of lightweight timber floors

In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors, and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort, this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house. In this paper, the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal, static uniform load and concentrated load deflection value testing. The evaluation of the deflection value of the floor structure, the mode shape, the coupling of the fundamental frequency mode parameters, and the vibration comfort were also studied. The results show that the fundamental frequency simulation value, one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472 (BS6472-1:2008). That is, the floor structure is not lower than 8 Hz design requirements, and meets the frequency of BS-6472(BS6472-1:2008). The weighted root mean square acceleration is lower than the requirement of 0.45 m/s2; the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413, 31.847 and 48.921 Hz, and the fundamental frequency mode is the bending vibration in the length and width directions. The second order is the bending mode in the length direction, and the third order is the bending mode in the width direction. The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction; and the second-order natural frequency is the second-order bending vibration shape in the X direction. when the uniform load is mainly the weight of floor own, the simulated maximum deflection value is 1.0658 mm; the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design, and the simulation is the largest. The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint, which meets the requirements of National Building Code of Canada-2015 (NBCC). The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm; the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical. The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.

Experimental appraisal for characterizing laboratorial and field performance parameters of pervious concrete pavement

Abstract Loratorial tests with pervious concrete comprised porosity and hydraulic conductivity as well as mechanical parameters as compressive, indirect tensile and bending strengths besides assessing its static and dynamic elasticity moduli. Later, a pervious sidewalk area of 1.0 x 8.65 square meters was built in order to determine the variation of the infiltration rate along time; over such experimental sidewalk, impact deflection tests performed allowed to assess back calculated moduli of the pervious concrete layer, resulting 33% to 13% lower than conventional concretes. A mechanistic analysis allowed to estimate the required thickness of concrete for heavy- and light-traffic areas. Tests disclosed no significant difference among the different concrete mixes, with 25% porosity and 0,1 cm/s permeability. Initial sidewalk infiltration rate of 0.5 cm/s dropped 50% four months after construction. It was verified that pervious concrete thicknesses for trucks and buses use are far higher than conventional concrete pavements.

Creep stability of the DART/Hera mission target 65803 Didymos: II. The role of cohesion

The binary asteroid 65803 Didymos-Dimorphos is the target of the first asteroid deflection test (NASA's Double Asteroid Redirection Test, DART) and the first binary asteroid system that will be characterized by a rendezvous mission (ESA's Hera). The cohesive strength of the fast-spin-primary Didymos is a key factor that could affect the impact outcome and stability of this system. To support the preparation and data interpretation of these missions and gain a better understanding of the formation and evolution of this system, we investigate the structural stability and cohesive strength of Didymos based on current observational information. We use the Didymos radar shape model to construct rubble-pile models consisting of ~40,000 to ~100,000 particles with different arrangements and size distributions. To investigate the effect of cohesion on the structural stability and dynamical behaviors of Didymos, we explicitly simulate the YORP spin-up process of these rubble-pile models from a slow spin state to Didymos' current spin state using a high-efficiency soft-sphere-discrete-element-model code, pkdgrav. We test the creep stability of Didymos' rubble-pile representation with different values of cohesion and derive the critical amount of cohesion to maintain stability. The results show that Didymos should at least have a minimum bulk cohesion on the order of 10 Pa to maintain its structural stability if the interparticle tensile strength is uniformly distributed. Since the surface particles are less bonded by cohesive contacts than the interior particles, the internal macroscopic cohesion is about three times the surface macroscopic cohesion. We find that the bulk density and particle arrangement and size distribution of Didymos have significant influences on its critical cohesion and failure behaviors, indicating different binary formation pathways. With the critical cohesion, Didymos is at the edge of maintaining a stable shape, and a rapid small decrease in its spin period would excite its rubble-pile structure and lead to reshaping or mass shedding. Whether the DART impact could partially or globally destabilize this system requires further investigation of the full two-body gravitational dynamics and the ejecta evolution. With the expected measurements returned by DART's onboard cubesat LICIACube in 2022 and Hera in 2027, the correlations between Didymos' physical properties and failure behaviors found in this study may be possible to constrain the mechanical properties and evolutionary history of this binary system.

Experimental study on deflection of recycled concrete twoway slab under concentrated load

In order to study the deflection calculation method of recycled concrete two-way slab under concentrated load, a full-scale model of recycled concrete two-way slab was designed, and the replacement rate of recycled coarse aggregate was 30%. Through the loading test, the failure mode of the two-way slab was observed, and the test data of the whole process curve of the deflection changing with the load value and the development of the mid-span deflection were obtained. Based on the current theoretical formula, this paper uses Origin software to simulate the deflection of recycled concrete two-way slabs under concentrated load on the basis of comparing the deflection test value and the theoretical calculation value, and proposes a correction coefficient for the two-way slab deflection calculation. For the proposed two-way plate deflection calculation correction factor, the existing test data is used to verify it. The results show that the deflection value calculated according to the method in this paper is relatively close to the test value. The research results can provide reference for follow-up experiments.

Rotordynamic Analysis of Gas Foil-Polymer Bearings Based on a Structural Elasticity Model of Polymer Layer along with Static-Load Deflection Tests

In this study, rotordynamic analysis is performed using a simple structural model for the polymer layer of gas foil-polymer bearing (GFPB) composed of an accumulated bump foil and a polymer layer with high structural damping. The simple model that considers the elastic behavior of a cylinder-shaped polymer layer is introduced, and the structural stiffness of the layer is estimated based on Hooke’s law for differential elements in the layer. In addition, the simple model is coupled with the structural stiffness of the bump foil in consideration with a series relationship, which represents the structural model of GFPBs. A GFPB with thickness of 2 mm is fabricated, and the structural model is validated via static-load deflection tests for the GFPB. As a result of model validation, the proposed model is found to be effective in predicting the elastic behavior under the lightly loaded condition of GFPB. Next, the static performances of GFPBs, namely, gas-film pressure, thickness, and journal positions with respect to different polymer layer thickness, are analyzed to evaluate rotordynamic stability of GFPBs. The results indicate that high thickness yields an increase in damping and a decrease in cross-coupled effects. Specifically, in this study, 3 mm-thick polymer gives the best stability performance given the predicted effective damping results. As a result, this work provides a reasonable model for structural elasticity of GFPBs and lays a foundation for the widespread use of GFPBs.

Design of experiment of material level settings on the factors affecting the quality of calcium silicate board by using the Taguchi method

The main purpose of this paper is to identify and determine the level of regulation on factors that influence the type and characteristics of the pulp so that it can produce optimal quality Calcium Silicate Boards. The experiments were carried out using the Taguchi method and using quality characteristics: strength, deflection, density, and water absorption. Then, the factors that influence product quality are the use of pulp percentage, pulp type, and pulp composition. Data processing uses two analyzes to determine the optimal level setting, which consists of mean analysis and signal to noise ratio analysis, then an experiment is carried out to confirm the predictive value of the level setting factor under optimal conditions. The results showed that the type and composition of the pulp affected the strength and density of the product, the use of the percentage of the pulp affected the deflection of the product, and all factors did not affect the absorption of product water, with an optimal level of regulation: 9.8% percentage of pulp, Y type of pulp, and 100% pulp composition. Confirmation results obtained an average value of the strength test was 154.5 kg / cm2, 13 mm for the deflection test, 1.3275 g / cm3 for the density test and 36.35% for the water absorption test.

High temperature fracture toughness of single-layer CrAlN and CrAlSiN hard coatings

Hardness and toughness are among of the most important physical properties of hard coatings and it is important to analyze them at temperatures present during coating applications. CrAlN and CrAlSiN are hard coating materials frequently used in high temperature applications. While both possess high oxidation resistance and thermal stability, they differ in their microstructure. In this work, the fracture toughness of magnetron-sputtered single-layer CrAlN and CrAlSiN hard coatings was determined up to 700 °C by in-situ scanning electron microscopy micro-cantilever deflection tests. The results show a decreasing trend of the fracture toughness with increasing temperature. While both coatings' fracture toughness trends are similar up to 400 °C, they diverge at higher temperatures. In general, the evolution of the fracture toughness with increasing temperature shows similarities to the observed changes in hardness in the same temperature range.

Indian mallow fiber reinforced polyester composites: mechanical and thermal properties

The natural fiber reinforced polymeric composites have found to be an excellent substitute for synthetic fiber based polymeric composites and are being widely utilized in several advanced engineering applications. The present experimental work deals with randomly oriented Indian mallow fiber/polyester (IMFP) composites which are fabricated by compression moulding method by varying the fiber wt. % from 10 to 50%. The prepared IMFP specimens were evaluated through various mechanical and thermal properties and the results showed that better properties were obtained in specimens with 50 wt. % fiber content. The optimum tensile strength and modulus was about 46 MPa and 3.56 GPa respectively, while the elongation at break was 1.39%. The optimum flexural and impact strength are estimated to be around 111 MPa and 14 kJ/m2 respectively. The heat deflection test (HDT) displayed that temperature withstands up to 84 °C at 50 wt. % of fiber content. The surface morphologies of the fractured composite specimens were characterized by scanning electron microscopy (SEM) analysis. The overall results confirmed the suitability of the present specimens to be employed in various light weight applications.

Design and Test of Contactless Overvoltage Sensor With Spherical Six-Electrode

Most of the available overvoltage sensors are too sensitive to the installation angle and inducing direction. Even a slight angular deflection will cause a nonnegligible error to the measurement. To reduce the impact caused by angular deflection, in this article, we propose a new spherical six-electrode overvoltage sensor to improve the measuring accuracy and stability. First, we presented the 3-D electric field ( $E$ -field) coupling mechanism, vector synthesis method, design, and output properties of the proposed sensor. Second, we obtained the relationship between the structural parameters and the equivalent capacitance by the finite-element method (FEM). Finally, we completed the steady-state test, transient test, and 3-D angular deflection test. From the results, the sensor has a broad bandwidth of 1.2 MHz, a phase error of less than 1.8°, and good linearity of the output signals. In the case of 3-D angular deviations, the mean relative error (MRE) of the sensor is lower than 2.55%, with a maximum standard deviation (SD) of 0.088%, which proves that the output of the proposed sensor is well consistent with the overvoltage signal, and its accuracy is almost immune to the angular deflection.

A Comparison on Numerical Simulation Models for Vibrational Performances of the Wood Truss Joist Floor System

Wood truss joist floors are increasingly used to replace traditional solid timber joist floors in low‐rise timber houses. An understanding of the vibration performance of wood truss joist floors is critical for the design and serviceability of the floors. It is difficult to model wood truss joist floors accurately because of the complicated boundary conditions and numerous sophisticated flexible connections. This paper discusses three simplified modeling methods for the wood truss joist floor system. The modeling results were validated by a series of static deflection tests and vibration modes and frequencies tests of a full‐size floor. And predictive analysis of human‐induced vibration of the floor was also conducted. The vibration characteristics of the wood truss joist floor were investigated. The examination of the applicability of these modeling methods was provided. The results indicate that the point loading deflection more easily affects the deflection of the adjacent joist. However, the deflection influence on other joists that are three spaces away is minimal. Walking on the wood truss joist floor produces steep vibration acceleration fluctuations at the floor center for a relatively long time period. The sheathing‐to‐joist connections and the metal plate connections of the joists have significant influences on the vibration response of the wood truss joist floor. The modeling method, which considers the flexible metal plate connections and flexible sheathing‐to‐joist connections, performs best for predicting the vibration performance of the floor.

The impact of dynamic effects filtration on the results of the comparative analysis performed with falling weight deflectometers

ABSTRACT The paper evaluates the influence of dynamic effects filtration incorporating the method of deflection frequency normalisation on the results of the comparative analysis of FWD dynamic instruments. The authors' calculations are based on a database comprising the results of comparative deflection tests conducted by use of six FWD instruments, on five different test sections, in strictly monitored on-site conditions. After analysing the results of deflection measurements subjected to the dynamic effects filtration procedure, it was possible to unambiguously determine the device for which the obtained deflection values differ most from the values obtained for other devices. The unequivocal selection of a device for comparative test results of FWD devices that had not been submitted to deflection frequency normalisation has not been possible. The calculations performed in the paper have confirmed the positive influence of dynamic effects filtration using the method of deflection frequency normalisation on the results of the comparative analysis of FWD devices.

Field and numerical investigation of full depth reclamation with Portland cement in Georgia

The Full Depth Reclamation (FDR) technique has recently become a popular rehabilitation method to reconstruct old flexible pavement. Pulverized existing roadway materials are blended with stabilizing agents such as foamed asphalt and Portland cement to form a stiff base course for the new pavement. In Georgia, Portland cement is commonly used as a stabilizing agent for FDR stabilization. One of the challenges in FDR stabilization projects is to achieve uniform stiffness throughout the stabilized layer. FDR mix design often specifies a fixed rate of stabilizing agent, which could generate a range of FDR strengths due to the inherent variability in the existing pavement. Stiffness variation in the stabilized base should be minimized for optimum long-term pavement performance. This study investigates the influence of the variability in the FDR base layer stiffness on pavement performance. A series of field and laboratory tests were performed on a pavement reconstruction project in Georgia to assess variability. Tests included Unconfined Compressive Strength (UCS) tests and deflection tests with a Light Weight Deflectometer (LWD) and Falling Weight Deflectometer (FWD). Mechanistic sensitivity analyses were performed based on the field and laboratory test results to investigate the effect of variability in FDR properties on pavement performance. The results indicate both the FDR base thickness and strength have a significant influence on the predicted pavement responses. Findings presented here will be of interest to pavement engineers involved in the design and performance modeling of FDR pavement.

Contribution of reactive aggregates towards the performance of in-service asphalt pavements

This paper presents an assessment of the contribution of reactive aggregates on performance of asphalt pavements in service in order to better understand how to mitigate likely asphalt pavement failures resulting thereof. A petrographic and mineralogical analysis was done on rocks that were used in the asphalt mix as well as their mineral composition. Also, a visual condition survey, deflection testing and coring of the asphaltic surfacing for further analysis and testing were conducted to establish the extent of the distresses. Results showed that though aggregates tested were meeting the criteria required of a good quality asphalt concrete in relation to mechanical properties, they did not satisfy the other criteria in relation to their mineralogical composition and adhesion. Aggregates were found to be reactive and contained pyroxenes and feldspar which were responsible for deterioration in form of ‘blows ups’ and indentations observed on the pavement surface. Pyroxenes oxidised when they combined with atmospheric components due to their high iron content to form hydrated iron oxides. Feldspars experienced a hydrolytic reaction when they reacted with water to form clay minerals, potassium ions, and silica in solution. Continued exposure of reactive aggregates through water and air permeating into the open textured and cracked asphalt surface will result into total transformation of the pyroxenes into erodible iron oxides and hydroxides hence leading to further deterioration of the asphalt pavement. It is recommended that engineers consider conducting petrographic and mineralogical analysis when sourcing quarries for production of aggregates to be used in asphalt mixes.

Evaluation of Coir Geotextile Reinforcement for Low-Volume Roads

ABSTRACT Natural geotextiles play a vital role in the reinforcement and ground improvement of soft compressible soil to enhance soil strength and ensure stability. Of all the natural fibers, coir possesses high tearing strength even in very wet conditions. Hence, in this paper, the efficacy of coir geotextile in improving the functional performance of the pavement and enhancing the modulus of the subgrade soil has been investigated by visual examination and by conducting tests such as Benkelman Beam Deflection (BBD) test, geogauge and static plate load tests on the test sections constructed in the field. The obtained data reveals that the elastic modulus of the subgrade multiplies appreciably when it is reinforced with coir geotextile, thereby helping in increasing the service life of the pavement. Similar results are reflected in the pavement condition survey results as well. The improvement attained in the elastic modulus of the reinforced subgrades is 1.41 and 1.25 times of the elastic modulus of the parent soil, with coir geotextile of mass per unit being 740 g/m2 and 365 g/m2, respectively. The modified subgrade elastic modulus is given as input to the KENLAYER software and analyzed in order to prepare a design chart for coir geotextile reinforced low-volume roads.

Precast Bamboo Reinforced Furniture Elements using Self Compacting Concrete

Public furniture in India are designed based on ergonomics standards derived from the international standards proving a significant hurdle in comfort for the users. We propose to tackle this by conducting ergonomic studies of true users. This study aims to check the viability of using an eco-friendly composite as street furniture, i.e., Park Bench. Additionally, owing to the increasing negative impact steel manufacturing has on the environment, the furniture is designed using a Bamboo-SCC composite. The objective of the study is to use bamboo as reinforcement in SCC to make furniture. The furniture is made using self-compacting concrete to ensure greater stability of the bamboo reinforcement and further to increase the durability of the benches. The final product is analysed based on deflection tests, cost-benefit analysis, and embodied energy savings. It was concluded that in areas where bamboo is readily available, this project can be implemented as a more energy-efficient and low-cost option.

Effects of a propulsor on the maneuverability of an autonomous underwater vehicle in vertical planar motion mechanism tests

The effects of a propulsor on the hydrodynamic forces acting on an autonomous underwater vehicle (AUV) were investigated by towing tank model tests. A mathematical maneuvering model using a whole vehicle model was established, and captive model tests using vertical planar motion mechanism equipment were performed to obtain maneuvering coefficients. The Reynolds number of the full scale test model in the operation condition was 4.12 × 106, and the revolution rate of the propulsor was fixed at the self-propulsion point. The forces on the body and control fins were measured in static drift, control fin deflection, pure heave and pure pitch tests with and without the propulsor. The propulsor effects on the hydrodynamic force and moment were identified as spatially irregular thrust, flow acceleration around the control fins, and added mass of the propulsor. In the simulation using the component model where the propulsor effect considered as a constant thrust, the maneuverability of the AUV was overestimated compared to that of the whole vehicle model. Thus, the mathematical maneuvering model should consider propulsor-hull interactions.