Beam Assembly Research Articles

Analyzing effects of damping materials on automotive bumper beam assembly under different velocity conditions

Automotive bumper beams play a very crucial role in absorbing impact energy during crash collisions and reducing damage from the front or rear ends of the vehicle during low or high-velocity impact. This paper discusses the impact of different energy-absorbing materials introduced between the fascia and the metallic beam. A novel recipe, with combinations ranging from 0% to 50% and 20% to 80% of Polypropylene (PP) with Ethylene vinyl acetate (EVA) and Polypropylene (PP) with Ethylene propylene diene monomer (EPDM), was prepared by weight and comparative study based on their impact strengths was done both experimentally and numerically. The mechanical properties of the polymer blends have been determined under tensile, compressive, and impact testing. Results obtained from numerical simulation analysis lie in reasonable agreement with the experimental findings. The tensile and compression test results show that polymer blend PP/EPDM-50/50 is the best selection as an energy absorber due to its ductility and toughness properties which is evident from experimental testing. The introduction of this blend in front of the metallic strip (bumper beam) has significantly supported the improvement in the energy-absorbing capacity and impact strength.

Self‐Sustained and Coordinated Rhythmic Deformations with SMA for Controller‐Free Locomotion

This study presents a modular, electronics‐free, and fully onboard control and actuation approach for shape memory alloy (SMA)‐based soft robots to achieve locomotion tasks. This approach exploits the nonlinear mechanics of compliant curved beams and carefully designed mechanical control circuits to create and synchronize rhythmic deformation cycles, mimicking the central pattern generators prevalent in animal locomotions. More specifically, the study elucidates a new strategy to amplify the actuation performance of the shape memory coil actuator by coupling it to a carefully designed, monostable curve beam with a snap‐through buckling behavior. Such SMA‐curved beam assembly is integrated with an entirely mechanical circuit featuring a slider mechanism. This circuit can automatically cut off and supply current to the SMA according to its deformation status, generating a self‐sustained rhythmic deformation cycle using a simple DC power supply. Finally, this study presents a new strategy to coordinate (synchronize) two rhythmic deformation cycles from two robotic modules to achieve efficient crawling locomotion but still use a single DC power. This work represents a significant step toward fully autonomous, electronics‐free SMA‐based locomotion robots with fully onboard actuation and control.

Fabrication of thin-walled hat-shaped beams from ultrahigh strength steel by laser-assisted robotic roller forming

Laser-assisted robotic roller forming (LRRF) can be applied to forming ultrahigh strength sheets to products with high geometrical accuracy. In this study, the geometrical profiles and three-point bending performance of thin-walled hat-shaped beams formed by LRRF and robotic roller forming (RRF, i.e., without laser heating) were experimentally investigated. It is found that the geometrical distortion resulted from the accumulation of longitudinal tension during multi-pass roller forming is significantly alleviated by LRRF. In addition, the bending performance of LRRF beam assembly is ameliorated at the initial deformation stage of three-point bending. The improvement is ascribed to a smaller bending radius and the alter of mechanical properties at the laser heat-affected zone. The lower geometrical precision of beams formed without laser heating results in early failure of spot welds of the beam assembly during three-point bending. LRRF beam assembly exhibits larger displacements at failure, and the failure mode is cracking at the edge of the laser-irradiated region. The pronounced microstructure differences on both sides of the crack suggest that the obvious laser-induced mechanical property gradients are responsible for the failure of LRRF beam assembly during three-point bending.

Numerical study on the strength enhancement of circular castellated steel beams with triangular corrugations and casing assembly

Modern buildings utilize steel-castellated beams to support extensions and reduce dead weight. However, the presence of castellations weakens the structure and creates additional failure mechanisms. Corrugations and castellations were combined in this study to strengthen the web. Using the ABAQUS software, a circular castellated-triangular corrugated steel beam with a perforated casing was modeled and analyzed. Triangular corrugations with corrugation angles of 30° and 45° and circular castellations with S/D ratios of 0, 1.1, 1.5 and 2 were used. The beam sections had a span of 2000 mm, depth of 300 mm, flange width of 150 mm, flange thickness of 16 mm and web thickness of 5 mm. The ultimate load of the beam assembly was determined using GMNIA on a simply supported beam with mid-point loading. A study on a flat web beam with the same dimensions and S/D ratios was conducted to understand and compare the behavior of the new corrugated–castellated assembly with and without casing. 22 configurations in the proposed castellated-corrugated assemblage, including a plain web, were modeled and analyzed. The results show that, compared with castellations in plain web beams, more than 60% of the load-carrying capacity was observed on a 30° corrugated-castellated beam with a casing assembly. In addition, the mass-to-capacity ratio of the same beam was higher.

Design and kinematic analysis of a multifold rib modular deployable antenna mechanism

Abstract. Aiming at the urgent need for the development of space deployable antenna with large aperture and a high storage rate, a new configuration of a multifold rib modular deployable antenna mechanism is proposed. The overall structure scheme design of the antenna is carried out, and the structure composition of the module, the principle of structural topology transformation, and the scheme of mechanism deployment and locking are expounded. According to the shape and constraint relationship of the structure deployment and folded state, and based on basic theory of robotics, calculation and the analysis of key structural parameters and the included angle of rib units are carried out, and the parameterized mathematical model is established. The detailed structural design is carried out, and then the complex structures such as the center beam assembly, diagonal beam assembly, and outer beam assembly are introduced in detail. The kinematic simulation of the mechanism is carried out by using ADAMS software, and the variation law of the motion parameters is analyzed. Finally, the prototype of a hexagonal prism single-module principle is developed, and a deployment function test and verification are carried out. The simulation and test results show that the proposed mechanism can realize the motion change from folded to deployed, and no problems such as interference or clamping are observed in deployment, which verifies the correctness and the feasibility of the structural scheme and principle. Moreover, the proposed new configuration scheme not only retains the characteristics of modular structure, such as good universality and easy expansion, but also has a high storage rate and structure efficiency rate. The research results have a high reference value and relevance for basic theoretical research and the engineering application of a space deployable antenna.

Research on the Key Technology of Prefabrication and Assembling of the Viaduct Substructure in the Urban Central Area of the Middle Earthquake Region

Facing the difficulty of construction of viaducts in the central area of the city with short construction period and large daytime traffic. Relying on the Nairobi Airport viaduct project in Kenya, the problems in the construction of this project and the special seismic intensity of the area were analyzed. The key technologies in the design and construction of the bridge substructure using prefabricated assembly technology were studied, and a reasonable substructure analysis was put forward. Block principle and assembly connection plan, and focus on the key construction technology of pier column and cap beam assembly. Through the research on the key technology of substructure design and prefabrication assembly and the application of engineering examples, the problem of viaduct construction in urban restricted road sections in the earthquake zone with moderate intensity is effectively solved.

Large Area Detection of Microstructural Defects with Multi-Mode Ultrasonic Signals

Cyclic loading or other stresses can lead to development of cracks and crack growth in mechanical structures, leading to eventual failure. While ultrasound imaging can be used for non-destructive testing of such structures, conventional ultrasound techniques are often limited by crack size, density, and areal coverage. An effective characterization of real-world, large-area structures is required at an early damage stage to prevent catastrophic failure and predict remaining life. In this study, a new nonlinear ultrasonic testing (NUT) method is proposed for large-area monitoring of practical structures with arbitrary complexity by using multiple-mode guided-wave ultrasonic signals. The proposed guided-wave NUT technique requires single-element transducers, simple electronics, and a mixed time-frequency domain signal processing. As a proof-of-concept demonstration, numerical simulations and experiments are performed on an A36 carbon steel beam assembly with previously formed microstructural defects that cause nonlinearities in ultrasonic response. The quadratic dependence of the nonlinear wave excitation on the input ultrasonic signal amplitude is shown by numerical simulations, and such a nonlinear ultrasonic response is experimentally observed in the zone with a high density of microstructural defects.

Study on theoretical modeling and mechanical performance of a spinning porous graphene nanoplatelet reinforced beam attached with double blades

In this article, theoretical modeling and vibration characteristics of a spinning double-blade beam assembly restricted by elastic supports are studied. Graphene nanoplatelet (GPL) reinforcement and porous foamed metal matrix are adopted to make up the assembly structure. Due to the nonuniformity of the porosity and graphene nanofillers, the material properties of the attached blades and beam are considered to change along the blade thickness and beam radius, respectively. They are obtained via the rule of mixture, the open-cell scheme and the Halpin-Tsai micromechanics model. These attached blades and beam are modeled in accordance with the Euler-Bernoulli beam theory and the Rayleigh beam theory, respectively. Via employing the Lagrange’s equation, the equations of motion of the double-blade beam are derived. Then, the natural frequencies of the spinning nanocomposite double-blade beam are calculated by the substructure modal synthesis method and the assumed modes method. A detailed parameter analysis is performed to study the influences of dimension, distribution pattern and weight fraction of GPLs, distribution and coefficient of porosity, length and location of the blades, stiffness and location of supports, and spinning speed on the mechanical behaviors of the double-blade beam assembly.

Multi-bolt looseness state monitoring using the recursive analytic based active sensing technique

Monitoring the looseness degree of multi-bolt connections is significant for ensuring the safety of steel structures. Among existing structural health monitoring techniques, the active sensing is preferred due to its sensitivity to structural damages. However, the energy based indicator, such as wavelet packet energy index (WPEI), is prone to saturation and fluctuation when monitoring multi-bolt looseness. In order to resolve this problem, the recurrence plots (RP), phase trajectory and recurrence quantification analysis (RQA) were employed to quantify the multi-bolt looseness by extracting nonlinear features from stress wave signals. Repeated experiments were conducted on a steel beam assembly with three bolts to verify the effectiveness of the proposed method. The experiments showed that the recursive entropy index could effectively eliminate the energy saturation and fluctuation, which enhances the performance to monitor the multi-bolt looseness state. In addition, the phase trajectory and RP could intuitively detect the location of the loosened bolt.

Using HSM Technology in Machining of Thin-Walled Aircraft Structures

Abstract Subtracting manufacturing technologies have entered that realm of production possibilities which, even a few years ago, could not be directly adapted to direct production conditions. The current machines, i.e. heavy, rigid cutting machines using high spindle speed and high feed speed, allow for manufacturing very thin and relatively long parts for use in the automotive or aerospace industry. In addition, the introduction and implementation of new 70XX aluminium alloys with high strength parameters, as well as monolithic diamond cutting tools for special machining, have had a significant impact on the introduction of high-speed machining (HSM) technologies. The main advantage of the applied manufacturing method is obtaining a very good smoothness and surface roughness, reaching even Sz = 6–10 μm and Sa <3 μm, and about four times faster and more efficient machining compared to conventional machining (for the beam part). Moreover, fixed and repeatable milling process of the HSM method, reduction of operational control, easy assembly of components and increase in the finishing efficiency compared to other methods of plastic processing (forming) are other benefits. The authors present a method using HSM for the manufacturing of aircraft parts, such as the chassis beam at the front of a commuter aircraft. The chassis beam assembly is made of two parts, front and rear, which – through a bolted connection – form a complete element replacing the previous part made using traditional technology, i.e., cavity machining, bending and plastic forming. The implementation of HSM technology eliminates many operations related to the construction of components, assembling the components (riveting) and additional controls during construction and assembly.

Experimental setup for beams with adjustable rotational stiffness: An educational perspective

AbstractIn structural analysis, the rotations of beams' supports are considered either completely fixed or completely free. Therefore, supports are idealized as fixed, pinned (hinged), or roller. In real structures, regarding rotation, the support behavior is neither fully rigid nor completely free and shows a semi‐rigid behavior in most cases. In this study, an educational test setup was created for a beam with semi‐rigid supports to examine the effect of semi‐rigid support on structural behavior. In this experimental setup, support conditions with different rotational stiffness can be obtained from pinned support to fixed support, which can be easily changed between the pinned and the fixed support. The physical equivalent of the rotational stiffness concept is shown in an easy and understandable way with the theoretical equations. A simulation tool based on the derived analytical equation is also developed using Mathematica Software. The simulation tool provides the users with a way to visualize the deformation of the system. The results of beam tests with different support conditions were compared with the results of the simulation, and the effects of semi‐rigid support on the beam behavior were shown. The results revealed that the semi‐rigid supported beam assembly created can also be used to examine the behavior of frame beams under vertical load. These simple novel experimental setup and simulation tools provided are convenient and useful approaches to demonstrate the structural concepts, including the semi‐rigid support and behavior of beams in a frame structure.

Structural performance assessment of concrete components based on fractal information of cracks

Damage assessment of concrete components is of vital importance for ensuring the safety of civil structures. The occurrence and development of cracks in reinforced concrete components are highly related to the damage condition. Based on the fractal characteristics of concrete cracks, a rapid damage assessment method of concrete components using the index of Fractal Dimension ( FD ) was proposed in this paper. Damages in structural concrete components were first categorized into four empirical levels according to the so-called loading-ratio. Through image processing of the crack developments from previous studies of concrete beam and column members at different loading stages, database of crack FD versus loading-ratio for concrete beams and columns were separately built. Linear regressions correlating the crack FD s and the loading-ratios were then constructed and validated for concrete beams and columns, respectively. The loading-ratio can be predicted by the linear regression using new crack FD of the concrete component for damage assessment. The proposed method was applied to a lab-tested specimen of a reinforced concrete shear wall - beam assembly. Results show that the proposed fast structural performance assessment method is reliable for identifying potential damage levels in concrete components. • A new damage index called Fractal Dimension is proposed for damage assessment of concrete components. • An empirical relationship between fractal dimension of concrete surface cracks and damage level is constructed. • Fast damage assessment for concrete components is realized.

Evaluation of Effective Polymer Fiber Length on Energy Absorption Capacity of Reinforced Beams by EBR and NSM Methods

This study presents a comparison of two methods used for retrofitting Reinforced Concrete (RC) beams, namely, the Externally Bonded Reinforcement (EBR) and the Near-Surface Mounting (NSM) methods. A parametric analysis was carried out using variables such as the retrofitted, the retrofitting method (EBR and NSM), and the thickness of the Carbon Fiber-Reinforced Polymer (CFRP) sheets. To achieve this goal, the finite element method and ABAQUS software were employed. An un-retrofitted beam was also simulated as the control specimen for comparison. Beam responses were compared through load–displacement and energy absorption capacity diagrams. Results show that the higher energy absorption capacity in all CFRP-retrofitted RC beams, which was 1.69–5.54 times higher than in un-retrofitted beams. In the case where half of the beam was reinforced using CFRP sheets, the entire beam assembly and the CFRP sheet contributed to load-bearing, thus delaying crack nucleation in the beam and increasing its energy absorption capacity. As a result, the energy absorption capacity of the beam, in this case, was less than that obtained in the previous one where half the span of the beam was retrofitted.

Challenges in the Design and Implementation of a Steel Beam Launcher for Precast Girders Assembly

AbstractACCIONA has designed and built a Steel Beam Launcher for Precast Beam Assembly. The structure consists of two steel trusses of triangular tridimensional structure 110.90 m long and 3.755 m high. The hoist load capacity of the Beam Launcher is 110 tons and the maximum span between supports is 52 m. The main challenge for the design of the Beam Launcher has been to guarantee the safety of the works in all the maneuvers to be carried out, taking into account the determining longitudinal slope of the viaducts up to 6.0%. To take on this challenge, the Beam Launcher has been designed with a rack‐and‐pinion system, which ensures total safety in the maneuvers. The Beam Launcher has also been designed to develop all the operations required for the assembly of the Viaducts, such as lateral load of the precast beams from barges, front and rear feed of the Beam Launcher from the adjacent span and front and rear feed from a truck located on the previously poured deck. Besides, the Beam Launcher is modular to adapt to the different spans of the Viaducts, extending and decreasing its length when needed. This modular requirement governs the design of the joints in the Beam Launcher: the connections between diagonals and main chords are pinned and the connections between modules are prestressed, using both prestressed bolts and prestressed bars depending on the demanding forces.

Study of the ergonomic risk in operators of an assembly line using the RULA method in real working conditions through the application of a commercial sensor

Assessing ergonomic risk in real working conditions is a challenge for ergonomists, who use observational methods to collect information, with RULA (Rapid Upper Limb Assessment) being one of the most widely used. The disadvantage of these methods is that data collection is subjective and is based on estimates of projected angles on photos and/or videos, which leads to variations according to the criteria of each evaluator. For this reason, this work proposes the use of the Kinect V2 commercial sensor, as a tool for ergonomic assessment in real working conditions in industry. In the study, data such as planes, angles and positions of the worker were obtained, which the RULA method needs to determine the existence of ergonomic risk. The application of the sensor was carried out in real working conditions and it was performed to an operator of a bridge beam assembly line in a metalworking factory. Then, the trajectory and angle curves were obtained by means of an algorithm; and were compared with those of a standard motion capture system in a photogrammetry laboratory. Finally, the RULA score obtained by the implemented system was validated by an expert.

Study of nonlinear effects in a bolted joint using the base excitation as an input

In this paper, the nonlinearity detection, characterization and identification of a bolted beam assembly is presented. The methodology utilized in this work is based on the force reconstruction using the base excitation as an input and the nonlinear system identification. The force reconstruction procedure was carried out by exciting the bolted beam assembly at very low excitation with fully tightened bolt condition. The nonlinear effect in the bolted beam assembly was induced by reducing the bolt clamping loads. A collection of frequency response functions (FRFs) are shown at different clamping loads to detect and characterize the nonlinearities. Once the nonlinearities are detected and characterized, the restoring force surface method using the reconstructed force was used to identify the nonlinear parameters in the modal space. Four different base excitation (energy) levels with three different tightening torques were considered in the tests in order to study the energy dependence of the damping nonlinearities. In all the cases, the nonlinear system identification methodology employed was successful in identifying the damping and stiffness nonlinearities.

Nonlinear Interface Reduction for Time-Domain Analysis of Hurty/Craig-Bampton Superelements with Frictional Contact

Virtual prototyping in engineering design rely on modern numerical models of contacting structures with accurate resolution of interface mechanics, which strongly affect the system-level stiffness and energy dissipation due to frictional losses. High-fidelity modeling within the localized interfaces is required to resolve local quantities of interest that may drive design decisions. The high-resolution finite element meshes necessary to resolve inter-component stresses tend to be computationally expensive, particularly when the analyst is interested in response time histories. The Hurty/Craig-Bampton (HCB) transformation is a widely used method in structural dynamics for reducing the interior portion of a finite element model while having the ability to retain all nonlinear contact degrees of freedom (DOF) in physical coordinates. These models may still require many DOF to adequately resolve the kinematics of the interface, leading to inadequate reduction and computational savings. This study proposes a novel interface reduction method to overcome these challenges by means of system-level characteristic constraint (SCC) modes and properly orthogonal interface modal derivatives (POIMDs) for transient dynamic analyses. Both SCC modes and POIMDs are computed using the reduced HCB mass and stiffness matrices, which can be directly computed from many commercial finite element analysis software. Comparison of time history responses to an impulse-type load in a mechanical beam assembly indicate that the interface-reduced model correlates well with the HCB truth model. Localized features like slip and contact area are well-represented in the time domain when the beam assembly is loaded with a broadband excitation. The proposed method also yields reduced-order models with greater critical timestep lengths for explicit integration schemes.

Comparitive study on the flexural behaviour of glulam built-up beams based on ambient and standard fire tests

The experimental study presented in this paper proposes a type of glulam beam with a hollow cross-section that can further optimise solid glulam beams. The study investigated the structural behaviour of glulam built-up box-section beams under four-point flexural bending at both ambient and elevated temperatures. A total of eleven 3100-mm long simply supported beam assemblies were experimentally examined: seven beams were tested at ambient temperature; and four beams were subjected to CAN/ULC-S101 standard fire. Five of the seven beam assemblies tested at ambient temperature were fabricated using self-tapping screws, while the other two assemblies were built using industrial polyurethane adhesive. Each built-up beam assembly was made of four glulam panels, all of 44 mm thickness except the bottom flange panel which had 86 mm thickness. Through ambient testing, it was concluded that when the spacing of the screws connecting the top and bottom flange panels of the built-up section to its web panels was decreased from 800 to 200 mm, the flexural resistance of the beam assembly was increased by about 45%. Whereas further reduction of the spacing from 200 to 100 mm for the screws connecting the bottom flange panel to the web panels over a distance equals to one-third of the span length of the beam from both supports, where shear stresses are maximum, increased the flexural resistance of the beam additionally by 10%. However, the experimental results of the glued beam assemblies show significantly high flexural strength that was almost equal to the calculated strength of an equivalent hollow-section glulam beam. In a subsequent phase, only the strongest beam assemblies (two screwed and two glued) were tested under the effect of standard fire while subjected to monotonic loading that caused a bending moment that is equivalent to the beam full resistance moment calculated for ambient condition. Fire tests' results show that both screwed and glued glulam built-up box-section beams can sustain the applied design load under standard fire exposure for more than 30 min without any fire protection.

Examination of erection safety of precast beam assembly using a slanted beam section based on assembly test

ABSTRACT Assembling precast frames subjected to heavy construction loads may require a significant crane operation time when they were assembled by conventional steel joints having a straight beam cut. This study proposed a method that will provide a facile and rapid assembly of heavy precast frames, having the temporary bolting be established as noncritical path. Lower flanges of wide flange beam installed at end of precast beams were partially removed to prevent bottom flange of steel beam from running into flanges of L-shaped guide pockets when steel beam was inserted in L-shaped guide pockets. Permanent connections are made by bolting L-shaped guide pockets. Stable behavior was observed during an erection test of the proposed connection. This study also aimed to investigate an assembly safety of steel beam-column joints with a skewed beam section based on a nonlinear finite element analysis. Strain and stress analysis also demonstrated that stable structural behavior of joint elements was ensured during an assembly of precast frames.

Programmable assembly of bi-walled nonuniform beams: Concept, modeling and performance

Postbuckling structural instabilities has been shown to have useful mechanical characteristics such as well deformation resistance and recovery. However, the difficulties in control and programmability, due to the complex interconnected sensitivities to geometric and material properties, severely hinder the phenomenon use in multifunctional structural applications. In this paper, we propose a concept of nonuniform beam assembly to increase the the controllability of the postbuckling response. Bilaterally constrained, nonuniform beams are theoretically investigated to obtain the buckling instability, and the predictions are compared with the experimental and numerical results with satisfactory agreements. Parametric studies are carried out to demonstrate the tunability of the reported beam assembly with respect to the geometric properties and material parameters (i.e., Young's modulus) of the nonuniform beams. Finally, the use of the proposed beam assembly method is investigated for novel applications as mechanical triggers and deformation detectors. This study demonstrates an exciting approach to tune the mechanical characteristics of engineered assembly structures for novel applications, such as material embedded mechanical sensing.