Cross Section Of Rod Research Articles

Longitudinal Fracture Analysis with Taking into Account the Elongation Speed of Inhomogeneous Rod Subjected to Centric Tension

The present theoretical study deals with longitudinal fracture of a structural component representing inhomogeneous rod that is loaded in centric tension at its lower end. The upper end of the rod is clamped. The rod is continuously inhomogeneous in radial direction. Besides, the rod exhibits non-linear elastic mechanical behaviour. The parameters involved in the non-linear constitutive law used when analyzing the longitudinal fracture behaviour are smooth functions of the running radius of the rod cross-section. The basic aim of the paper is to analyze the longitudinal fracture with taking into account the influence of the rod elongation speed. The case when the elongation varies with time at a constant speed is treated in detail. The necessary equations for deriving the parameters of the stressed and strained state of the rod are formulated. The problem for determination of strain energy release rate (SEER) for the longitudinal crack in the rod is solved with considering the effect of the elongation speed.

Exploiting a Built-In Simultaneity: Perhaps, the Simplest Way to Show that the One-Way Speed of Light is Measurable in Principle

We consider a physical system composed of a rod of length AB = L rotating uniformly. Two points on the rod cross-sections at A and B are connected in a way that reflects the simultaneity built-in into the system. This preset simultaneity can be exploited to synchronize two distant clocks, one at A and the other at B, with an internal procedure that, in principle, may differ from Einstein synchronization. The natural built-in simultaneity can be used for testing the one-way light speed and Lorentz invariance. PACS: 03.30.+p, 42.25.Bs, 45.50.−j.

Real-time modeling of the riveting process forces for aircraft panel structures

The riveting of large panels in aircraft manufacturing requires an automatic drilling and riveting machine capable of precise and stable operation. However, the significant nonlinearity and time-varying nature of riveting process forces severely impact the control capacity and operational accuracy of these machines. So, the objective is to provide technical assurance for the precise operation of the machine and ensure high-quality riveting of the panels. Therefore, a real-time modeling method for the automatic riveting process forces on aircraft panels is proposed, which focuses on the rivet die's downward compression displacement as the core variable and accounts for the non-uniform deformation of rivets. This method assumes a constant volume for the rivet rod. It combines power-law hardening and Coulomb's friction theories to establish three sub-models for different riveting stages: the elastic stage, the plastic deformation stage, and the driven head formation stage. Further, considering the continuity of rivet's deformation, rivet rod's cross-section stress, and the driven head dimensions changes with the driven head's downward compression displacement, a novel real-time continuous dynamic load model for the full compression riveting process of a single-rivet is developed. The results indicate that the model is effective, with a maximum deviation of 7.50 % between experimental and predicted values, demonstrating its accuracy and reliability. In conclusion, this research provides a real-time, continuous description of the riveting process force, enabling automatic machines to promptly detect defects and deformations in the riveting.

Numerical Study of Control Rod's Cross-Section Effects on the Aerodynamic Performance of Savonius Vertical Axis Wind Turbine with Various Installation Positions at Suction Side

Numerical Study of Control Rod's Cross-Section Effects on the Aerodynamic Performance of Savonius Vertical Axis Wind Turbine with Various Installation Positions at Suction Side

Modeling and experimental investigations of mechanical properties of hybrid composite rods with gradient composition

The concept of creating a functionally gradient material characterized by a smooth change in composition was used in the fabrication of hybrid composite rods. A hybrid core structure with a glass fiber core and a carbon fiber shell was adopted as the basis. To reduce the risk of delamination at the core-shell interface, a gradual transition was implemented from the core of the rod, made based on high-modulus fiber, to the outer shell composed of low-modulus fiber. The strength and modulus of elasticity in bending for hybrid composite rods were modeled. Using the proposed model, an optimal scheme for distributing glass and carbon fibers across the cross-section of a composite rod was selected. Hybrid composite rods with a diameter of 25 mm, with the same matrix (31±0,1%) and fiber (69±0,1%) content, but with different distribution patterns of glass and carbon fibers along the cross-section, were manufactured via pultrusion technique. The bending strength and stiffness characteristics of composite rods were experimentally determined. Mechanical properties of rods with different reinforcement schemes were compared: homogeneous, core-shell, single, and double gradient. The results indicate that a hybrid rod with a gradient reinforcement scheme exhibits higher values of strength and modulus of elasticity during bending. The modulus of elasticity of the rod with the "double gradient" structure was 103 GPa, for comparison, the modulus of elasticity of the rod made by the "core-shell" scheme was 82 GPa. The simulation aligns well with the experimental data.

Numerical study of effective parameters on true triaxial test results in rigid type apparatus

Operational parameters in true triaxial loading devices (TTA), such as the loading rod dimensions, friction between the loading platens and sample faces, loading gap, and one-side loading may affect the test results. Knowledge of the effect of each parameter is very important to correctly interpret rock behavior and to optimize these devices. Employing the Flac3D finite difference software, a rigid type true triaxial systemdesigned and builtat Amirkabir University of Iran (AUT-TTA) was simulated andinvestigated in this study. The results indicate that increasing the ratio of the rod cross-section to the loading platen area leads to an increase in the sample confinement, so, more uniform stress distribution occurs in the rock sample. The loading gap reduces strength of the rock specimen and leads to concentration of tensile stresses at the sample edges. The end effect leads to an increase in the stress level and a pseudo-hardening behavior in the samples. Also, the end effect is intensified under one-side loading condition compared to two-side loading. Comparison between results of AUT-TTA numerical simulation and analytical analysis (ideal conditions without considering operational parameters) indicates that the slope of the stress–strain diagram has low sensitivity to operational parameters. The most important operational factor affecting the stress level and dilatation stress is the end effect and other operational parameters have little effect. All parameters lead to an increase in the dilation strain. The clear edge and one-sided loading under low intermediate principal stresses and the end effect under high intermediate principal stresses have the greatest effect on the dilation strain.

Multiple equilibrium states of a curved-sided hexagram: Part I—stability of states

The stability of the multiple equilibrium states of a hexagram ring with six curved sides is investigated. Each of the six segments is a rod having the same length and uniform natural curvature. These rods are bent uniformly in the plane of the hexagram into equal arcs of 120o or 240o and joined at a cusp where their ends meet to form a 1-loop planar ring. The 1-loop rings formed from 120o or 240o arcs are inversions of one another and they, in turn, can be folded into a 3-loop straight line configuration or a 3-loop ring with each loop in an “8” shape. Each of these four equilibrium states has a uniform bending moment. Two additional intriguing planar shapes, 6-circle hexagrams, with equilibrium states that are also uniform bending, are identified and analyzed for stability. Stability is lost when the natural curvature falls outside the upper and lower limits in the form of a bifurcation mode involving coupled out-of-plane deflection and torsion of the rod segments. Conditions for stability, or lack thereof, depend on the geometry of the rod cross-section as well as its natural curvature. Rods with circular and rectangular cross-sections will be analyzed using a specialized form of Kirchhoff rod theory, and properties will be detailed such that all four of the states of interest are mutually stable. Experimental demonstrations of the various states and their stability are presented. Part II presents numerical simulations of transitions between states using both rod theory and a three-dimensional finite element formulation, includes confirmation of the stability limits established in Part I, and presents additional experimental demonstrations and verifications.

Multiple equilibrium states of a curved-sided hexagram: Part II—Transitions between states

Curved-sided hexagrams with multiple equilibrium states have great potential in engineering applications such as foldable architectures, deployable aerospace structures, and shape-morphing soft robots. In Part I, the classical stability criterion based on energy variation was used to study the elastic stability of the curved-sided hexagram and identify the natural curvature range for the stability of each state with circular and rectangular rod cross-sections. Here, we combine a multi-segment Kirchhoff rod model, finite element simulations, and experiments to investigate the transitions between four basic equilibrium states of the curved-sided hexagram. The four equilibrium states, namely the star hexagram, the daisy hexagram, the 3-loop line, and the 3-loop "8", carry uniform bending moments in their initial states, and the magnitudes of these moments depend on the natural curvatures and their initial curvatures. Transitions between these equilibrium states are triggered by applying bending loads at their corners or edges. It is found that transitions between the stable equilibrium states of the curved-sided hexagram are influenced by both the natural curvature and the loading position. Within a specific natural curvature range, the star hexagram, the daisy hexagram, and the 3-loop "8" can transform among one another by bending at different positions. Based on these findings, we identify the natural curvature range and loading conditions to achieve transition among these three equilibrium states plus a folded 3-loop line state for one specific ring having a rectangular cross-section with a height to thickness ratio of 4. The results obtained in this part also validate the elastic stability range of the four equilibrium states of the curved-sided hexagram in Part I. We envision that the present work could provide a new perspective for the design of multi-functional deployable and foldable structures.

Fabrication of a gradient AZ91-bioactive glass composite with good biodegradability

This study used friction stir-back extrusion to fabricate the AZ91 + 3 wt% bioactive glass gradient composite wire. The microstructure, mechanical properties, and corrosion resistance of a material in a simulated body fluid were investigated. Three 2-mm diameter holes with varying hole patterns were drilled in the cross-section of the AZ91 rod to apply 3 wt % bioactive glass to the AZ91 matrix. The results demonstrated that the hole pattern strongly influenced the material's flow in the extruded wire's cross-section. By increasing the distance between the center of the initial rod and the center of the holes, a higher temperature and more uniform distribution of plastic strain are formed during friction stir back extrusion, resulting in uniform distribution of bioactive glass particles and α + β eutectic structure near the surface of composite wires. Introducing bioactive glass particles into the zone near the surface of the AZ91 rod results in the formation of a uniform distribution of bioactive glass particles near the surface and their absence in the central zone of the composite wire. A higher amount of discontinuous β-Mg17Al12 phase and α + β eutectic formed at the grain boundaries by increasing the temperature and plastic strain during friction stir-back extrusion. The crystallographic texture of the AZ91 rod changed from prismatic to basal and pyramidal due to the friction stir-back extrusion method. A gradient AZ91-bioactive glass composite wire with ultimate tensile strength, yield strength, elongation, and corrosion resistance 58, 64, 62, and 34%, respectively, greater than AZ91 as-cat rod can be produced by inserting bioactive glass powder using a hole drilling method and applying a friction stir back extrusion process.

Augmenting the performance of friction stir back extruded AZ91 alloy using the gradient composite design technology

This study investigates the effect of extrusion speed during friction stir back extrusion on the microstructure, mechanical characteristics, and in vitro corrosion behavior of AZ91-3 vol % bioactive glass composite wire. To that end, the bioactive glass powder was inserted into the AZ91 matrix by drilling holes in the cross-section of the AZ91 rod. The results show that the extrusion speed strongly influenced the material's flow in the extruded wire's cross-section. By adding the bioactive glass powder to the processed wire, the ultimate tensile strength and corrosion resistance increased 5 and 23% compared to the additive-free wire. By decreasing the extrusion speed to 20 mm/min, the higher amount of discontinuous β-Mg17Al12 phase and α + β eutectic formed in the grain boundaries. By applying the friction stir back extrusion process on the AZ91 rod a random crystallographic texture formed in the extruded wires. In the composite samples extruded at a rotational speed of 1200 rpm, a traverse speed of 20 mm/min, a gradient distribution, and improvement of mechanical properties (ultimate tensile strength of 332.95 MPa, yield strength of 268.33 MPa, and elongation of 9.89%) and corrosion rate (1.879 mm/year) at simulated body fluid were achieved.

On the homeotypes of kobellite

Kobellite is a Pb-Bi-Sb sulfosalt with minor amounts of (Cu, Fe) and with the crystal structure composed of two types of rods, one of which has unusual lateral extensions (‘lobes’), which depart from the usual lozenge-shaped rod cross-section in sulfosalts. Several Pb-Bi-Sb and Pb-Sb-rich sulfosalts form a small group built on similar principles. Some of them are related by homology (e.g., izoklakeite), and differ by the perpendicular dimensions of rods (length and multiplicity of atomic layers in a rod; e.g., sterryite), and especially by different combinations of archetypes and archetype portions which participate in the rods (PbS archetype and the two orientations of SnS archetype). The present article summarizes and discusses the published data on the group. Homeotypism makes the group interesting and potentially a fertile source of further structural varieties.

Mechanical and tribological behaviour of Al—Mg—Cu(p) composite cladded on AA1050 substrate

The effect of adding copper powder and changing the rotational speed of the consumable rod during friction surfacing of Al—Mg alloy on AA1050 aluminum substrate was investigated. The copper powder was inserted by drilling holes in the cross-section of the consumable rod. The coating microstructure was studied using optical and electron microscopy, and the mechanical properties of coatings were studied using a shear test. The results showed that with increasing the rotational speed of the consumable rod from 600 to 1000 r/min, the copper powder distribution becomes more uniform, and the agglomeration of copper powder occurs less frequently. The average grain size of coatings decreased from (2.0±0.1) to (0.9±0.2) μm by increasing the rotational speed from 600 to 1000 r/min. As the rotational speed increases, the copper-rich particles become smaller and are formed as CuAl2 intermetallic compounds. The maximum load required for debonding coating from substrate increases from 16.2 to 18.4 kN by increasing rotational speed from 600 to 1000 r/min. The coating with rotational speeds of 600, 800, and 1000 r/min results in 12%, 18%, and 21% lower wear rate than that of the AA1050 substrate, respectively.

Influence of Microstructure on the Mechanical and Corrosion Response of a Friction Stir-Extruded WE43 Magnesium Rod

Friction stir extrusion (FSE) was used with WE43 Mg to create a rod with a hybrid microstructure. The rod’s electrochemical corrosion response was characterized in Hank’s balanced salt solution at 37 ± 1 °C. The rod showed refined grains near the edge, while coarse grains were observed at the rod center. A larger fraction of precipitates was observed near the edge possibly hindering grain growth. The refined grains and the presence of a larger fraction of precipitates in the edge regions resulted in higher hardness owing to a confluence of precipitate hardening and solid–solution strengthening. Texture analysis of the rod cross-section exhibited a basal texture, perpendicular to the extrusion direction and populating the rod’s outer surface. In compression, the rod showed a near-base material yield strength (225.6 MPa) and a good combination of compressive strength (357.5 MPa) and ductility (~17.7%). The rod’s electrochemical corrosion response was sensitive to variations in the grain size, texture, and precipitate distribution between the rod core and edge regions. Removal of the edge region resulted in the formation of a more stable and protective film with an increase in the immersion period. The results from the study establish the ability of the FSE process to tailor the rod microstructure thereby influencing the mechanical properties and corrosion rate of Mg alloy.

Ballistic performances of the hourglass lattice sandwich structures under high-velocity fragments

In this paper, the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments. Attention is paid to elucidating the influences of rod cross-section dimensions, structure height, structure layer, and rod inclination angle on the deformation mode, ballistic performances, and ability to change the ballistic direction of fragments. The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters. In this respect, structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and, consequently, ballistic performances.

Thermally Driven Continuous Rolling of a Thick-Walled Cylindrical Rod.

Self-sustained motion can take advantage of direct energy extraction from a steady external environment to maintain its own motion, and has potential applications in energy harvesting, robotic motion, and transportation. Recent experiments have found that a thermally responsive rod can perform self-sustained rolling on a flat hot plate with an angular velocity determined by the competition between the thermal driving moment and the friction moment. A rod with a hollow cross section tends to greatly reduce the frictional resistance, while promising improvements in thermal conversion efficiency. In this paper, through deriving the equilibrium equations for steady-state self-sustained rolling of the thick-walled cylindrical rod, estimating the temperature field on the rod cross-section, and solving the analytical solution of the thermally induced driving moment, the dynamic behavior of the thermally driven self-sustained rolling of the thick-walled cylindrical rod is theoretically investigated. In addition, we investigate in detail the effects of radius ratio, heat transfer coefficient, heat flux, contact angle, thermal expansion coefficient, and sliding friction coefficient on the angular velocity of the self-sustained rolling of the thick-walled cylindrical rod to obtain the optimal ratio of internal and external radius. The results are instructive for the application of thick-walled cylindrical rods in the fields of waste heat harvesters and soft robotics.

Деформации в нестационарной стадии прессования прутка из алюминиевого сплава с малым коэффициентом вытяжки

Introduction. It is noted that extrusion is the main procurement process in the aluminum alloys forming operations. At the same time, the process has such a disadvantage as the nonstationarity of the metal plastic flow. The work aim is to establish the inhomogeneity deformation level of the pressed rod front part by numerical simulation using the finite element method. The study objectives are to formulate the extrusion process boundary conditions, to obtain a solution and to evaluate the inhomogeneity degree. Research methods: the finite element method was used to evaluate the deformed state. The actions sequence included the creation of primary deformation zone shape and the tool configuration. The mutual movement of the tool and the deformable material is set using the appropriate boundary conditions. The deformable medium is a ductile material with power-law hardening, the physical and mechanical properties correspond to the aluminum alloy of the 6000 series. Results and discussion: It is revealed that the strain degree in the pressed rod front part is extremely nonuniform distributed; differences above 300% are recorded. The strain degree distribution dependences in the rod cross sections are constructed depending on the distance from the front end at different relative radial coordinates. It is revealed that the rod central layers acquire a constant level of the strain degree earlier than the peripheral layers. The stationary process is achieved with less metal motion. The work result application scope is the technological study of rational metal cutting of aluminum alloys at the extrusion final stage in order to use recyclable waste more rationally. Conclusions. In the extrusion process with a low elongation ratio, the strain degree is distributed nonuniform both along the press rod cross and along its length. The rod front part remains weakly deformed both at the periphery and in the center in the nonstationary initial extrusion stage. It often forces to send for remelting due to the insufficiently developed metal structure. At the same time, if the limits on the minimum possible degree of deformation are set, then using the results of the calculation by the finite element method, the minimum length of the metal to be removed can be set, thereby reducing the mass of waste sent for remelting.

A geometrically exact discrete elastic rod model based on improved discrete curvature

This paper presents a discrete, geometrically exact elastic rod model based on improved discrete curvature. The model is an extension of finite difference type discretization of Kirchhoff–Love rod from Discrete Differential Geometry, with 4 unknowns, including translational displacements of the axis and the axial cross-sectional rotation. The orthogonality of the rod axis and cross-section is guaranteed by parallel transport in pseudotime. A newly defined unified discrete curvature with five weighting function schemes is presented. Three of them are proposed by reducing the max nonlinear term of the Taylor expansion of the rotation vector. Theory and numerical tests show that these three methods can increase the accuracy of the model compared to the traditional method. Scheme 5 performs the best out of the recommended schemes. A transformation of freedoms to the translational displacements and end rotations is introduced to the Discrete Differential Geometry model. By using this technique, rigid connections between rod segments, rotational boundaries and external ending moments can be realized conveniently and naturally. Important properties such as convergence, objectivity and insensitivity to the slenderness ratio are also verified and investigated with several suitable numerical examples. Furthermore, results show the use of discrete curvature has better performance for the stiff bar system with flexible connections than the continuous beam.

Rod–Airfoil Interaction Noise at Different Rod Cross Sections and Airfoil Angles

Vortex–body interaction noise from a rod–airfoil model has been investigated experimentally in an aeroacoustic wind tunnel. The model configuration varies by changing either the rod cross section (circular, square, rhombic, and elliptical) or the install angle of the airfoil at three directions (attack angle , sweep angle , and lean angle ) independently. This paper aims to assess the effects of these parameters on the characteristics of vortex–body interaction noise. A near-field microphone array was applied to locate the noise sources on the rod–airfoil model, and a far-field microphone array determined the noise level and radiation directivity. The results suggest that, in the test range, both the elliptical rod cross section and the change of the airfoil install angles can visibly reduce vortex–body interaction noise compared to the baseline rod–airfoil containing the circular rod and the airfoil at zero angles. The interaction noise level decreases with the increase of the eccentricity of the elliptical rod. Of the angles, the most effective way is the change of the sweep angle , which can achieve a noise reduction of 8 dB when reaches 20 deg, but the attack angle has more influence in reducing the vortex shedding frequency. In addition, the noise source distribution of different frequencies also changes with the variation of rod–airfoil configurations. Flow visualization using particle image velocimetry was conducted to analyze the noise change mechanism. The findings from this study are beneficial for engineers in designing low-noise components in several aeronautical and industrial applications.

Effect of Water Absorption on Flexural Properties of Kenaf/Glass Fibres Reinforced Unsaturated Polyester Hybrid Composites Rod

This study investigates the effect of water absorption on the flexural strength of kenaf/ glass/unsaturated polyester (UPE) hybrid composite solid round rods used for insulating material applications. Three volume fractions of kenaf/glass fibre 20:80 (KGPE20), 30:70 (KGPE30), and 40:60 (KGPE40) with three different fibre arrangement profiles of kenaf fibres were fabricated by using the pultrusion technique and were aimed at studying the effect of kenaf fibres arrangement profile and its content in hybrid composites. The fibre/ resin volume fraction was maintained constant at 60:40. The dispersion morphologies of tested specimens were observed using the scanning electron microscope (SEM). The findings were compared with pure glass fibre-reinforced UPE (control) composite. The water absorption results showed a clear indication of how it influenced the flexural strength of the hybrid and non-hybrid composites. The least affected sample was observed in the 30KGPE composite type, wherein the kenaf fibre was concentrated at the centre of a cross-section of the composite rod. The water absorption reduced the flexural strength by 7%, 40%, 24%, and 38% of glass/UPE (control), 20KGPE, 30KGPE, and 40KGPE composites, respectively. In randomly distributed composite types, the water absorption is directly proportional to the volume fraction of kenaf fibre. At the same time, flexural properties were inversely proportional to the volume fraction of kenaf fibres. Although the influence of water absorption on flexural strength is low, the flexural strength of pultruded hybrid composites was more influenced by the arrangement of kenaf fibre in each composite type than its fibre loading.

A Frequency-Reconfigurable Inverted-L Antenna Made of Pure Water

A pure-water inverted-L antenna with frequency reconfigurability is proposed in this letter. The radiation from the cutoff region of high-permittivity dielectric waveguide is here utilized in the proposed water antenna to realize the similar performance of a metal inverted-L antenna. According to the operational principle, the working frequency of proposed water antenna is mainly determined by the cross section of water rod rather than its length. It is found that a wide tuning range from 1.1 to 2.2 GHz can be achieved when the radius of cross section is changed from 2.5 to 5 mm. Two states with three-dimensional printed transparent double-layer resin container are selected to implement the frequency reconfigurability. By controlling the filling status of water, i.e., only occupying inner layer (state 1) or the whole container (state 2), the radius of water rod is altered. The operational frequency band of fabricated water antenna can be tuned from 1.41–2.04 GHz (state 1) to 1.07–1.33 GHz (state 2). The proposed antenna is intrinsically different from those conventional reconfigurable water wire antennas where length is usually tuned to attain frequency agility. Both wide frequency tuning range and stable broadside radiation are here achieved.