Hollow Profiles Research Articles

Flexural Behavior and Failure Modes of Pultruded GFRP Tube Concrete-Filled Composite Beams: A Review of Experimental and Numerical Studies

Pultruded glass fiber-reinforced polymer (GFRP) materials are increasingly recognized in civil engineering for their exceptional properties, including a high strength-to-weight ratio, corrosion resistance, and ease of fabrication, making them ideal for composite structural applications. The use of concrete infill enhances the structural integrity of thin-walled GFRP sections and compensates for the low elastic modulus of hollow profiles. Despite the widespread adoption of concrete-filled pultruded GFRP tubes in composite beams, critical gaps remain in understanding their flexural behavior and failure mechanisms, particularly concerning design optimization and manufacturing strategies to mitigate failure modes. This paper provides a comprehensive review of experimental and numerical studies that investigate the impact of key parameters, such as concrete infill types, reinforcement strategies, bonding levels, and GFRP tube geometries, on the flexural performance and failure behavior of concrete-filled pultruded GFRP tubular members in composite beam applications. The analysis includes full-scale GFRP beam studies, offering a thorough comparison of documented flexural responses, failure modes, and structural performance outcomes. The findings are synthesized to highlight current trends, identify research gaps, and propose strategies to advance the understanding and application of these composite systems. The paper concludes with actionable recommendations for future research, emphasizing the development of innovative material combinations, optimization of structural designs, and refinement of numerical modeling techniques.

Non‐Destructive and Mechanical Characterization of the Bond Quality of Co‐Extruded Titanium‐Aluminum Profiles

The transportation industry aims to improve energy efficiency and reduce CO2 emissions, with a focus on reducing vehicle mass. A key method involves advanced lightweight construction techniques using materials like aluminum alloys. Research is concentrated on developing processes to combine different materials into reinforced hybrid components, such as aluminum and titanium. This study focuses on the lateral angular co‐extrusion (LACE) process to produce hybrid hollow profiles of EN AW‐6082 and Ti6Al4V, investigating the impact of the thermomechanical processing during extrusion and heat treatment (HT) on the resulting bond quality and material properties. Various HT routes are tested to see their impact on intermetallic phase formation, longitudinal weld seams, and bonding strength. Mechanical testing evaluates the tensile strength of the joining zone, while nondestructive ultrasonic testing (UT) assesses joining zone integrity and poor bonding detection. Results indicate that HT parameters significantly influence the bond quality and mechanical properties of hybrid profiles. UT data shows a strong correlation with tensile strength and intermetallic phase growth, providing a nondestructive way to evaluate bond quality. This study highlights the potential of LACE processes and optimized HT strategies to improve the performance and reliability of aluminum–titanium hybrid components.

Improving the joint strength of thermoplastic composites joined by press joining using laser-based surface treatment

Fibre-reinforced thermoplastic composites (TPC) provide an automated and cost-effective solution for their use in lightweight structures in series production. The combination of different material configurations allows the design of highly stress tolerant components. Previous studies demonstrated that the combination of TPC sheets, TPC hollow profiles and injection moulding compounds is even suitable for crash-relevant automotive parts. All three components are combined during the injection moulding process. To prevent collapse, the part must remain in a consolidated state and cannot be preheated. However, this results in poor adhesion between the hollow profile, the bulk material, and the TPC sheet. Previous studies have shown that the bonding strength between the hollow profile and the injection moulding compound can be increased by surface pre-treatment using laser structuring and plasma technology. In this work, laser structuring is employed to enhance the bonding strength between the hollow profile and the TPC sheet. Microscopy analysis is used to investigate the resulting surface morphology. Subsequently, single-lap-shear (SLS) specimens are produced by pressing the TPC sheets onto the flat part. The resulting bonding strengths are then evaluated by tensile shear tests. The study analyses the impact of various pre-treatment parameters on the bonding strength. Furthermore, it investigates the effect of sheet temperature on the bonding strength, including specimens without pre-treatment. Finally, the results of the surface treatment of hollow composite profiles are discussed.

Velocity profile shapes in Alcator C-Mod plasmas

Abstract Toroidal rotation velocity spatial profiles ( r / a < 0.8) have been obtained from C-Mod over a wide range of operational conditions, including H-mode, I-mode, ICRF-heated L-mode and Ohmic L-mode (LOC and SOC), and in plasmas with ITBs, LH wave injection and MCFD. Peaked, flat and hollow rotation profiles have been observed. In H- and I-mode plasmas, generally with co-current peaked profiles, the peaking is correlated with temperature profile peaking, and both increase with toroidal magnetic field (decrease with ρ ∗ ). Any dependence on density peaking is unclear. For Ohmic L-mode discharges, with LOC, the velocity profiles are usually flat and most often directed co-current, while with SOC the profiles are hollow, mostly co-current at the edge and counter-current in the core. Both of these Ohmic rotation states exist with matched density and temperature profiles (and gradients), indicating that neither gradient is relevant during rotation reversals. For plasmas with LH wave injection and discharges with ITBs, the velocity profiles are hollow while the density and temperature profiles exhibit substantial peaking. Broadly speaking for all operational regimes, there is no unifying ordering of the velocity gradient with plasma parameters.

Severely weakened extrusion strengthening effect in porthole die extrusion of Al-Mg-Si alloy miniature complex hollow profile under an ultra-large extrusion ratio

Ultra-large extrusion ratio is hardly inevitable during porthole die extrusion of miniature complex hollow profile on industrial horizontal extruders. Although batch extrusion of miniature complex hollow profile has been achieved at ultra-large extrusion ratio, their microstructure and mechanical properties are still unclear. To this end, under the extrusion temperature ranging from 400 ℃ to 480 ℃, a 4×4 mm Al-Mg-Si alloy micro heat pipe profile was extruded at an ultra-large extrusion ratio of 137. The grain size and crystal orientation of the profile were obtained by metallographic and electron backscattered diffraction (EBSD) techniques, and further exploration of the microhardness, tensile properties and pressure-resisting performance were conducted. Interestingly, severely weakened extrusion strengthening effect and low sensitivity of microstructure and mechanical properties to extrusion temperature were observed. Compared to the as-cast extrusion billet, the profile exhibits slight grain refinement and improvement in mechanical performance, and the extrusion temperature does not significantly affect the microstructure and mechanical properties. Instead, as the extrusion temperature increases, the recrystallization fraction generally decreases. These abnormal phenomena are inferred from the fact that even at lower extrusion temperatures, an ultra-large extrusion ratio leads to premature dynamic recrystallization (DRX), and more abnormal growth grains are formed in the profile, weakening the mechanical properties. The higher the extrusion temperature, the earlier DRX occurs, generally forming more abnormal growth and dynamic recovery grains.

Effect of the sharp profile geometry ong the cutting forces of tire recycling tools

Objective: Study the impact of blade profile geometry on cutting forces during tire recycling, focusing on how variations in the shape and design of tools affect the efficiency and quality of the cut, as well as the tools' lifespan. Methodology: Through the construction and testing of three blade geometries, based on a prior numerical study and made from DF2 and 1.2363 steel, experiments were conducted on a Universal Testing Machine with samples of used tire rubber. Results: It was demonstrated that the hollow profile blade significantly reduces energy consumption and improves cutting performance compared to the 30° straight V profile blade, for both rubber-only samples and those with reinforcing textile fibers. Additionally, the study presented the evaluation of shear stresses using a 90° blade, indicating an average shear stress value of 8.67 MPa. Conclusion: This finding suggests that the appropriate selection of blade geometry can significantly contribute to the efficiency of the tire recycling process, offering important economic and environmental implications.

Determination Of Weld Thickness In Hollow Section Connection Under Local Buckling Effect

Hollow section profiles are widely used in the structural steel industry. An important point to take into consideration in such connections is the continuous transfer of internal forces from element to element. One of the measures taken to ensure this continuity is to use end plates. The connection between plates and elements is mainly provided by welds. The aim of this study is to determine an optimum weld thickness for connections subjected to local buckling of box-beam-columns under bending. Corner and circular fillet welds were used to join the designed plates with box columns and beams. Hollow section profile connections were experimentally studied in the Steel Structure Laboratory of the Department of Civil Engineering of Süleyman Demirel University. Results were used to develop numerical models. Ansys Workbench was used in numerical models to analyze the corner welds of different thicknesses and lengths depending on plate dimensions and to examine their behavior.

Turbulence-reduced high-performance scenarios in Wendelstein 7-X

In the Wendelstein 7-X (W7-X) stellarator, turbulence is the dominant transport mechanism in most discharges. This leads to a ‘clamping’ of ion temperature over a wide range of heating power, predominantly flat density profiles where hollow profiles driven by neoclassical thermo-diffusion would be expected and by rapid impurity transport in injection experiments. Significantly reduced turbulent transport is observed in the presence of strong core density gradients found transiently after core pellet injection and irregularly after boronisation or boron pellet injection. Density peaking is also achieved in a controlled manner in purely neutral beam heated discharges where particle transport analysis reveals an abrupt reduction in the main-ion particle flux leading to significant density profile peaking not explained by the NBI particle source alone. The plasmas exhibit a heat diffusivity of around χ=0.25±0.1m2 s−1 at mid radius, a factor of around 4 lower than ECRH dominated discharges. Despite the improved confinement, the achieved ion temperature is limited by broader heat deposition and the lower power-per-particle given the higher density. This is overcome with limited reintroduction of ECRH power, where the low heat diffusivity diffusivity is maintained, the density rise supressed and ion temperatures above the clamping limit are achieved. The applicability of these plasmas for a high performance scenario on transport relevant time scales is assessed, including initial predictions for planned heating upgrades of W7-X, based on a range of assumptions about particle transport.

A universal simulation model of the continuous pipe rolling process on a controllably movable mandrel.

To study the technological process of rolling solid and hollow round profiles, it is important to have a correct mathematical description of the patterns that determine the boundaries of the deformation zone. The article analyzed scientific works that examine the calculation of geometric parameters of the deformation zone during the rolling of solid and hollow round profiles in two-roll and multi-roll calibers. As a result of the analysis, a conclusion was drawn regarding the necessity of a more detailed description of the determination patterns for the geometric boundary conditions of the deformation zone. This led to the proposal of a universal method for determining the shape of the billet and the shape of the caliber groove, as well as the derivation of the equations for the roll surface and the boundary of the contact surface of the deformation zone for various rolling schemes. The developed method allows for an increase in the accuracy of calculating the energy-force parameters of the rolling processes, including continuous rolling, in the production of solid and hollow round profiles according to the circular–oval scheme in calibers formed by any number of rolls, thanks to the consideration of a sufficiently wide range of geometric features

Experimental and finite element investigation on bolted connection in monolithic 3-dimensional cuff with pultruded box section

This article presents a concise and practical research study on the application of pultruded GFRP (Glass Fiber Reinforced Polymer) hollow sections in structural engineering. Experimental and computational investigations are conducted on the utilization of GFRP cuff components for joining tubular pultruded fiber-reinforced polymer (PFRP) beams and columns. Both adhesive bonding and bolted connections are explored for connecting PFRP box sections of beam-column interfaces. The study investigates twelve series of beam-to-column connections under monotonic loading conditions, varying cuff geometry. A finite element model is developed to represent the pultruded fiber-reinforced polymer box sections, columns, and cuff sections. The model’s accuracy in depicting frame stiffness and cuff damage patterns, considering different thicknesses and lengths of GFRP cuff connections, is validated against experimental test frame behavior. This research fills a gap in scientific inquiry regarding GFRP hollow profiles, providing valuable insights for structural engineering applications.

MATHEMATICAL MODELING OF THE HOLLOW PROFILES FORMING PROCESS

Steel alloys containing manganese and boron are increasingly being used in mechanical engineering, including automotive and agricultural sectors. Products of critical application made from such steels, including hollow ones, have a high level of mechanical properties, surface hardness, and wear resistance. These products are obtained by profiling of previously electrically welded round pipes with a hot sheet stamping or pressure treatment (drawing, cold rolling, stamping). Technological parameters of combined processing methods are determined by the results of experimental research, which, due to the complexity and cost of materials, leads to significant expenses. The application of mathematical modeling can reduce the number of experiments and forecast the quality of finished products. The research focuses on investigating the possibility of obtaining square hollow profiles by means of push-pulling through one stand of a pipe welding unit and defining the requirements for geometric parameters of the billet.

Variable Shape Tooling for Composite Manufacturing: A Systematic Review

The choice of material, manufacturing process, and molding tool significantly affects the quality, environmental impact, and cost efficiency of composite components. Producing one-piece hollow profiles with smooth inner surfaces and undercuts presents major challenges for conventional mold concepts. There is yet no thorough review of shape-variable mandrels in composite manufacturing to be found in the literature. This paper provides an overview of research on shape memory polymers and other shape-variable materials used in tooling applications for composite manufacturing. This work covers shape memory, heat shrink, and other deformable tooling concepts that enable the production of one-piece Type V pressure vessels, air intake ducts, or curved struts and tubes. A systematic literature review in combination with a state-of-the-art open-source active learning tool ASReview is conducted. Fifteen relevant studies were identified. Research on shape-variable tooling is mainly conducted by three research groups in the USA and the PRC. The tooling is mostly made of unreinforced thermosets, especially styrene-based ones. Thermoplastic resins are less common, and reinforcements limit the usable elongation in the temporary shape. The shape variability is either a shape memory and/or a softening process, which, in all studies, is activated by heating. Release agents are widely used to ease demolding. No ecological or economical assessment of the manufacturing methods was conducted in the reviewed studies. Three fields for further research that could be identified are as follows: (1) thorough ecological end economical assessment of shape-variable mandrels in comparison with conventional tooling; (2) thermoplastic shape memory polymer mandrels; and (3) further investigation of simulation capabilities for shape memory mandrels.

Optimization design of porthole die and study on microstructures and mechanical properties for an Al–Li alloy hollow profile

In this paper, a hollow Al–Li alloy profile was taken as an example, and the optimization design method of Al–Li alloy porthole die was given. Compared with the basic die design, the optimized die reduces the standard deviations of velocity and temperature as well as the maximum equivalent stress, resulting in a significant reduction of the distortion degree of the extruded profile, and the optimized die meets the strength requirements. The microstructures, mechanical properties and strain distributions of the longitudinal welds and matrices of the extruded profile were analyzed. It is found that the longitudinal welds are well welded without macro/micro defects. The fracture of tensile specimens all occurred at the matrices instead of welds, and the mechanical properties in the thick-walled matrices are much lower than those in the thin-walled matrices. The grain size in the thick-wall matrices is much coarser and more ununiform than that in the thin-walled matrices, which is caused by the low strain in the thick-walled matrices. For increasing the strain amount and uniformity of local zone of the extruded profile, an innovative method through adding baffle-blocks in the portholes was proposed.

Improvement of core heat transport in NBI plasmas of heliotron J using high-intensity gas puffing

Controlling the heat transport profile is important for high performance in magnetically confined fusion plasmas. In this study, improved electron heat transport was achieved in neutral beam injection plasmas by applying high-intensity gas puffing (HIGP) on a stellarator/heliotron device called Heliotron J. Compared with conventional gas puffing (GP) fueling discharge, a higher and more peaked electron temperature profile was obtained, and the core ion temperature was slightly higher but similarly shaped. Using similar parameters, the electron density profile for HIGP remained similar and differed from the hollow density profile observed in electron cyclotron heating-eIBT plasma. Transport analysis using the FIT3D and TR-snap codes showed a clear reduction in the effective electron heat transport coefficient in the plasma core region. However, more detailed experiments are required to understand the mechanisms underlying this improvement fully.

Evaluating Mechanical Strength in Vertical-Axis Tidal Turbines: A Comparative Study of Internal Blade Structure and Material Selection through CFD Simulation

Due to the density of water, tidal turbine blades are subject to significantly greater stresses than wind turbine blades. Multiple blade failures occurred during prototype testing as a result of loading conditions and protracted exposure to seawater, which created a severe work environment. The structural integrity of tidal turbine blades is essential for long-term reliability and performance. Numerous investigations into structural performance have been conducted. However, previous research has centred on horizontal-axis tidal turbines, while research on small-scale vertical-axis tidal turbines is limited. This paper aims to compare the Vertical-Axis Tidal Turbine (VATT) structural performance of hollow and solid blade structures in an identical NACA profile using three distinct materials. Finite element analysis (FEA) is employed to construct a model and simulate the mechanical characteristics of VATT blades. The use of static analysis simulation is employed in order to evaluate many parameters, including stress distribution and deflection. Parametric studies are conducted to explore the impact of internal blade structure and materials on mechanical strength. The use of computational fluid dynamics (CFD) simulations is employed for the purpose of analyzing the interaction between blades of vertical axis tidal turbines (VATT) and tidal currents, thereby enabling the assessment of structural loading. According to the simulation results, the hollow profile is subject to significant deflections and stresses. Other data indicates that the utilization of stiffeners in porous structures improves material efficiency and results in lighter blades, although further analysis is needed to investigate fatigue life prediction in optimizing structural design.

Parametric analysis and its effect on machinability for Incoloy 800 with copper electrode

In Electric Spark Machining, choice of manufacturing constraints is a necessary feature. This Electrical Spark Machining is an advanced process in all manufacturing processes. For the manufacturing of sophisticated parts, which require accurate machining that time Electric Discharge Machining used. A super alloy, heat-treated tool steel, ceramics, heat resistance steels etc. which are tough to machining. For this, we use Electric Discharge Machining which also known as Electric Spark Machining. Incoloy alloy set in the group of super stainless steels. The main element of this Incoloy alloy is nickel-chromium-iron with other extra copper, molybdenum metal. High solidity at high peak temperature and super resist of erosion is the main feature of Incoloy alloy. Vast application of Incoloy 800 is like Heat exchangers, Carburizing equipments, Heating elements and nuclear steam generator tubing. In our research, we use hollow, flat, convex and concave electrode profile for machining of Incoloy 800.MRR and TWR are the parameters we analyze after the experiment.

Mechanical performance assessment of sustainable coal plastic composite building materials

This paper presents a study for developing a high filler content coal plastic composite (CPC) for use in building and construction applications as a substitute for the state-of-the-art wood-plastic composites (WPCs). The influence of coal type (bituminous, sub-bituminous) and content (up to 70 wt%) on the mechanical performance was characterized and compared with predominant commercially available WPC products. SEM micrographs revealed good adhesion between coal and the polymer at the interface with less porosity than WPCs. Additionally, particle fracture and particle pull-out failure mechanisms were evident in the SEM micrographs, with the latter being more dominant. DSC thermal analyses revealed potential chemical reactions between the coal and HDPE interfaces, resulting in enhanced composite performance. Results indicate the tensile strength for CPC material had inverse proportionality with coal content. Despite the reduction, tensile strength for CPC with 60 wt% bituminous coal was not significantly different from a typical WPC formulation. Flexural strength increased to a maximum value, at 60 wt% for bituminous coal and 50 wt% for sub-bituminous coal, followed by a decrease. CPC with 60 wt% bituminous coal possessed higher flexural strength and, in some cases, comparable flexural modulus as compared to WPC products. Flexural properties indicated that a composite deck made from the CPC material could meet or exceed the loading and deflection requirements for decking boards. FEA models indicated that a hollow deck profile would potentially have a better load-deflection curve with less localized stresses compared to common decking board profiled sections.

Atmospheric turbulence effects on hollow Gaussian Schell-model array beams.

Two types of hollow array beams with circular and rectangular distributions on propagating in atmospheric turbulence are investigated and analyzed comparatively with that in free space. Analytical formulas for the cross-spectral density function of two kinds of hollow array beam propagation in linear isotropic random media are derived and used to examine the behavior of the spectral densities. It is found that such beams possess stable hollow arrays with any dimension and lobes in free space, while such distributions only maintain small distances in atmospheric turbulence and ultimately tend to a Gaussian shape due to the turbulence destroying the hollow array profiles. The effects of the turbulence parameters on the behavior of the spectral density are analyzed in depth.

Numerical analysis of tooling design for extruding wide aluminium hollow profiles using multi-container extrusion technology

Recently a novel multi-container extrusion method has been proposed and proved feasible to simultaneously extrude multiple billets for producing thin-walled wide profiles with reduced force by experiments. Due to its different die structure compared to conventional extrusion methods, the effects of tooling geometries on the multi-container extrusion performance should be comprehensively analysed as the base of die design optimisation. In this study, the original three-container extrusion design and six modified designs were established to investigate the influence of three key geometrical variables, including container diameter, upper die height and welding chamber height, on the extrusion performance through finite element simulation. The considered extrusion performances include metal flow uniformity, extrusion force, welding pressure, die lifetime and material yield. The drawbacks of the original die design were revealed after the primary analysis of the key influencing variables and a three-step way of design improvement was proposed accordingly. Container block and upper die were optimised for the first step; welding chamber height and die bearing length were modified during the second and third steps respectively. Compared with the original design, the final optimised design can decrease the unevenness of the extrudate front shape by 75% and double the material yield, while the extrusion force, die lifetime and welding quality were basically unchanged.

Formation of non-uniform fibre distributions in winding-pultrusion process and its effect on axial compressive properties of hollow GFRP profiles

Formation of non-uniform fibre distributions in winding-pultrusion process and its effect on axial compressive properties of hollow GFRP profiles