Pengaruh Penambahan Serat Kawat Bendrat Terhadap Kuat Lentur Beton Geopolimer

Currently, innovation continues to be developed to replace cement with other materials so that the use of cement as a building material can be reduced. Utilization of coal waste (fly ash) is an alternative to subtitude cement. From previous studies, fly ash mixed with alkaline materials in the form of NaOH and Na2SiO3 in a ratio of 1:5 can produce geopolymer concrete. This geopolymer concrete research was continued by adding bendrat wire fibers into the geopolymer concrete mixture. The method used in testing the aggregate, testing the compressive strength of normal concrete K225, testing the flexural strength of normal concrete and geopolymer concrete refers to SNI. Another additional material that is mixed is bendrat wire fiber. The research was carried out in the form of making flexible beams of 10 cm x 10 cm x 50 cm with fiber variations of 0%, 0.5%, and 1,0% at the age of 14 and 28 days. The results of the flexural strength test of the BN beam at the age of 28 days can withstand loads than BG. The average flexural strength obtained with variations of BN, BN+SB 0.5% and BN+SB 1.0% respectively were 2.796 MPa, 3.113 MPa, and 3.879 MPa. The results of testing the average flexural strength of geopolymer concrete beams at 28 days, obtained variations of BG, BG+SB 0.5%, and BG+SB 1.0% respectively were 0 MPa, 0.055 MPa and 0.104 MPa. In addition, geopolymer concrete cannot be used as a beam and the addition of bendrat wire fiber to geopolymer concrete cannot withstand the tensile load on the concrete.

Modeling of centrifugal deployment of three-section minisatellite boom

The aim of the article is to model the processes of centrifugal deployment of a three-section boom and preliminary analyze the feasibility of this deployment method for an Earth remote sensing (ERS) minisatellite (MS). During the research, methods of theoretical mechanics, multibody dynamics, control theory, and computer modeling were used. Centrifugal deployment of multi-section booms have been successfully used on spin stabilized satellites, but not on ERS satellites, which have other features of operation and require additional studies. The main part of the MS is a platform to which a transformable antenna is attached by means of a transformable boom. Before deployment, the stowed boom and antenna are attached to the MS platform. The boom sections are connected by joints with one rotational degree of freedom and deployed sequentially due to centrifugal forces when the MS rotates in the required direction. Each of the boom joints has a locking mechanism that latches when a predetermined deploy angle is reached. To model the processes of the boom deployment, the MS is presented as a system of connected bodies, where the platform and the stowed antenna are absolutely rigid bodies, and the boom consists of three flexible beams of a tubular cross-section. The differential equations of the MS dynamics during the deployment are obtained using the Lagrangian formalism, which are supplemented by algebraic equations describing the constraints from the joints. The scenarios of the boom deployment with a constant control torque and a constant angular velocity of the MS are considered. These scenarios are simulated, and estimates of the control actions needed to ensure full deployment of the boom and the stabilization of the MS after latching of the joints are calculated. Dependences of variations of the loads on the boom structure during deployment are obtained. The simulation results allow us to conclude that it is feasible to implement the method of the boom centrifugal deployment for the MS, which can perform fast rotations about the three axes of the body reference frame. Implementation of this method allows designers to reduce mass of the MS because it does not require any servo drives in the boom deployment system.

Dynamical behavior of coal shearer under the influence of multiple factors in slant-cutting conditions

Aiming at the problem of severe vibration and abnormal wear and tear of various components in coal shearer under slant-cutting conditions, a non-linear dynamics model with 13 degrees of freedom for a coal shearer under slant-cutting conditions is developed using vibration mechanics and multi-body dynamics theory, and the characteristics of the slide shoes-middle groove contact, the ranging arm-haulage unit connection with gaps and the guidance sliding boots-pin rail multi-surface contact with gaps are described based on three-dimensional fractal theory and Hertz contact theory. Based on Huco's law, the ranging arm and the hydraulic rod are assumed to be flexible beams, the rigidity characteristics of the ranging arm itself, the connection characteristics of the haulage unit and the fuselage are described, a drum correction load with a traction speed correction factor is proposed as the external excitation of the system, and the model is solved and analyzed. The research results show that the change of traction speed has a greater influence on the vibration swing angle and displacement of the front drum, front ranging arm and front walking unit, and the vibration swing angle and displacement of the three increase with the increase of traction speed, while the change of coalface hardness coefficient has less influence on the vibration displacement of the key components of the coal shearer. Under the working parameters of v = 3 m/min and f = 3, the swing angle and displacement of the front ranging arm and front drum fluctuate in the ranges of − 0.4–0.1 rad and – 15–15 mm respectively; the vibration acceleration is – 300–300 rad/s2 and – 200–200 mm/s2 respectively, the main vibration frequencies are 16.63 Hz and 12.14 Hz respectively, and finally the results are verified by experimental methods.

A mortar formulation for frictionless line-to-line beam contact

This paper describes the quasi-static formulation of frictionless line contact between flexible beams by employing the mortar finite element approach. Contact constraints are enforced in a weak sense along the contact region using Lagrange multipliers. A simple projection appropriate for thin beams with circular cross-sections is proposed for the computation of contact regions. It is combined with the geometrically exact beam formalism on the Lie group $SE(3)$ S E ( 3 ) . Interestingly, this framework leads to a constraint gradient and a tangent stiffness invariant under rigid body transformations. The formulation is tested in some numerical examples.

Vibration, synchronization and localization of three-bladed rotor: theoretical and experimental studies

Numerical and experimental methods in free and forced vibrations of the rotating structure consisting of the rigid hub and three flexible beams are considered. Firstly, the system of four mutually coupled dimensionless differential governing equations is presented and then forced response of the system as well as synchronization phenomenon are investigated. Next, the finite elements method is used to design the rotating structure and analyse complex dynamic response. During the numerical calculations symmetric, as well as de-tuned rotor are analyzed. Finally, results obtained from ordinary differential equations and numerical simulations are compared with experimental tests.

Fluid-Structure Interaction of Flexible Whisker-Type Beams and Its Implications for Flow Sensing by Pair-Wise Correlation

(1) Background: Sensing of critical events or flow signatures in nature often presents itself as a coupled interaction between a fluid and arrays of slender flexible beams, such a wind-hairs or whiskers. It is hypothesized that important information is gained in highly noisy environments by the inter-correlation within the array. (2) Methods: The present study uses a model sea lion head with artificial whiskers in the form of slender beams (optical fibres), which are subjected to a mean flow with overlaid turbulent structures generated in the wake of a cylinder. Motion tracking of the array of fibres is used to analyse the correlation of the bending deformations of pairs of fibres. (3) Results: Cross-correlation of the bending signal from tandem pairs of whiskers proves that the detection of vortices and their passage along the animals head is possible even in noisy environments. The underlying pattern, during passage of a vortex core, is a jerk-like response of the whiskers, which can be found at later arrival-times in similar form in the downstream whisker’s response. (4) Conclusions: Coherent vortical structures can be detected from cross-correlation of pairs of cantilever-beam like sensors even in highly turbulent flows. Such vortices carry important information within the environment, e.g., the underlying convection velocity. More importantly in nature, these vortices are characteristic elementary signals left by prey and predators. The present work can help to further develop flow, or critical event, sensory systems which can overcome high noise levels due to the proposed correlation principle.

Kinetostatic Modeling of Planar Compliant Mechanisms with Flexible Beams, Linear Sliders, Multinary Rigid Links and Multiple Loops

This paper presents kinetostatic models of planar compliant mechanisms with multinary rigid links, multinary joints, sliders and multiple loops based on the chained beam constraint model. The focus is on modelling of several building blocks of the beam type compliant mechanisms to aid in their design. The modelling approaches are based on the loop closure equations and the static equilibrium conditions. Models of the multinary rigid links, multinary joints, sliders are presented. As a result, the kinetostatic models of the compliant mechanisms can be systematically formulated by using these building blocks. Several mechanisms constructed by the building blocks are modelled and verified by finite element analyses. A case study is provided to demonstrate the application of the developed models. These models pave the way for versatile applications of the chained beam constraint model for the design and analysis of beam type planar compliant mechanisms.

Fluid-Structure Interaction of Flexible Whisker-Type Beams and Its Implication for Flow Sensing by Pair-Wise Correlation

(1) Background: Sensing of critical events or flow signatures in nature often presents itself as a coupled interaction between a fluid and arrays of slender flexible beams, such a wind-hairs or whiskers. It is hypothesized that important information is gained in highly noisy environments by the inter-correlation within the array. (2) Methods: The present study uses a model sea lion head with artificial whiskers in the form of slender beams (optical fibres), which are subjected to a mean flow with overlaid turbulent structures generated in the wake of a cylinder. Motion tracking of the array of fibres is used to analyse the correlation of the bending deformations of pairs of fibres. (3) Results: Cross-correlation of the bending signal from tandem pairs of whiskers proves that the detection of vortices and their passage along the animals head is possible even in noisy environments. The underlying pattern, during passage of a vortex core, is a jerk-like response of the whiskers, which can be found at later arrival-times in similar form in the downstream whisker's response. (4) Conclusion: Coherent vortical structures can be detected from cross-correlation of pairs of cantilever-beam like sensors even in highly turbulent flows. Such vortices carry important information within the environment, e.g. the underlying convection velocity. More importantly in nature, these vortices are characteristic elementary signals left by prey and predators. The present work can help to further develop flow, or critical event, sensory systems which can overcome high noise levels due to the proposed correlation principle.