Mechanical Performance Of Structures Research Articles

Metastructure based broadband structural stealth with material-structure-function integration

Broadband microwave absorption is difficult to be realized in traditional coating form as multiple electromagnetic resonances are difficult to be generated even with dielectric-magnetic loss composites. Narrow absorption band confines the practical usage of the novel electromagnetic nano composites. Herein, the structural stealth concept is proposed to overcome the narrow-band absorption problem with the effect carrier of metastructure. The gradient honeycomb metastructure (GHM) was designed and optimized with module stack large mutation genetic algorithms. The structural design, fabrication, experimental verification and parameter adjustment were included in the closed loop with material-structure-function integration. Multiple resonance effects were introduced in the gradient designs. GHM achieved −10 dB absorption bandwidth in 1.92–17.6 GHz and three deep absorption peaks were introduced by three layers of electromagnetic resonant honeycomb. Broadband absorption in oblique incidence from 30° to grazing angle 85° was achieved to overcome the oblique absorption degeneration problems of traditional nano lossy composites. The structural mechanical performance was high with the maximum equivalent tensile strength of 108.6 MPa and the maximum flexural load of 0.873 kN. The results showed the importance of structural stealth with material-structure-function integration to design metastructure for broadband microwave absorption, which provided a promising approach to achieve broadband microwave absorption.

Monitoring and assessment of mechanical response of large-scale prefabricated structures in underground subway stations during construction process

Mechanical performance of prefabricated structural components during construction is critical for ensuring long-term safety and durability of prefabricated underground stations (PUS). This study aims to address the issues of structure mechanical performance of large-scale prefabricated components during assembling process. First, a strain transfer model for five-layered armored fiber optic is proposed and validated experimentally through test. Second a PUS-based distributed fiber optic sensors (DFOS) monitoring system was established. Third, a PUS based hierarchical performance assessment framework was constructed. Finally, a PUS based theoretical Construction Intelligent Monitoring Assessment Model (CIMAM) was established to quantitively assess structure safety level. A case study of Shenzhen Metro PUS was performed, and the results showed that: (a) PUS-based DFOS monitoring system presents high accuracy and high resolution, (b) The monitoring system reflects the PUS reactions during the whole construction process with good adaptability and intelligence, (c) PUS-CIMAM results show that the assembly process of components is a significant control link, particularly the performance of large-span roof during assembling process is a key controlling component, and (d) PUS-CIMAM reveals the adjacent ring construction has a disturbing effect.

Simulation Analysis and Lightweight Design of Automotive Transmission Shafts Based on Optistruct

The transmission shaft is an important power transmission assembly in the automotive transmission system. Its structural mechanical performance is crucial for the comfort and safety of the vehicle. For this purpose, the transmission shaft of commercial vehicles is taken as the research object. Mechanical simulation analysis is conducted based on the finite element analysis software of Optistruct to investigate the stress and displacement distribution of various components on the transmission shaft under maximum torque and to verify its strength and stiffness. In addition, based on the stress distribution and manufacturing process requirements of the transmission shaft, a lightweight design is carried out for the transmission shaft components. The research results indicate that using simulation analysis methods can quickly obtain the force transmission path of the transmission shaft assembly and introducing manufacturing process requirements for lightweight design not only meets the manufacturing requirements but also has a more uniform stress distribution. The overall structure of the transmission shaft has been reduced from 23.8 kg to 16.8 kg with a weight reduction of 30%. The lightweight design method described in this article can quickly achieve weight reduction goals while meeting the structural strength of the transmission shaft.

Topology optimization with text-guided stylization

We propose an approach for the generation of topology-optimized structures with text-guided appearance stylization. This methodology aims to enrich the concurrent design of a structure’s physical functionality and aesthetic appearance. Users can effortlessly input descriptive text to govern the style of the structure. Our system employs a hash-encoded neural network as the implicit structure representation backbone, which serves as the foundation for the co-optimization of structural mechanical performance, style, and connectivity, to ensure full-color, high-quality 3D-printable solutions. We substantiate the effectiveness of our system through extensive comparisons, demonstrations, and a 3D-printing test.

Advances in Automated Eddy-Current Characterisation of Carbon Fibre Composites

Ply wrinkles in CFRP laminates are common and can lead to significant failure in composite structures if not properly assessed during the design, manufacturing, and service phases. Evaluating wrinkle geometries can be difficult as they are influenced by multiple factors, such as asymmetry, wavelength, and amplitude, which impact the structure's mechanical performance. High-frequency eddy current testing has proven effective for detecting in-plane waviness and out-of-plane wrinkles. However, the complex nature of CFRP structures and electrical anisotropy may hinder the effectiveness of an eddy current in-line monitoring system if not taken into account. In this study, an advanced modelling approach is employed to simulate the structural variation of the conductivity tensor. A designated wrinkle area, characterized by reduced electrical conductivity, is integrated with structural modelling to replicate a realistic coupon sample containing a wrinkle defect. Four proposed configurations are used to virtually test the samples, and their detection capabilities are analyzed quantitatively.

Auxetic effects in the large deflection bending characteristics of FG GRMMC shallow arches

Shallow arches are ubiquitous in long-span buildings, bridge structures, and tunnels. Uniform loading can cause large deflections characterized by snap-through, which can ultimately lead to structural failure. In this work, nonlinear bending of functional graded graphene reinforced metal matrix composite (GRMMC) shallow arches with auxetic properties is studied using higher order shear constitutive equations based on the von Kármán nonlinear theory of beam. Asymptotic solutions for an arch with simply and clamped supported ends are derived using a two-perturbation approach. The results show that the the initial thermal stress-induced deformation of the members increases with increasing environmental temperature. The generated auxetic effect in the structures due to Negative Poisson's Ratio (NPR) will act to resist bending deformation. This strengthening effect is more noticeable with increase in the deflection, especially in the first snap-through. In addition, the elastic foundation increases the global stiffness of the arch, thus enhancing its bending stiffness. The current work not only provides a theoretical foundation for understanding the interrelationship between the auxetic effect and mechanical performance of structures but also offers guidance for designing metamaterial structures.

Combined effect of fiber hybridization and matrix modification on mechanical properties of polymer composites

Glass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites’ tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC]S, [CGCGCG]S, and [G6C6] were manufactured. Fiber hybridization dramatically improved tensile strength between 51% and 76% compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10% and 16% concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5% and decreases by 7% for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70% for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis.

On the modeling of circular piezoelectric transducers for wave propagation-based structural health monitoring applications

Structural Health Monitoring (SHM) techniques have an important role in the performance of mechanical structures. In particular, piezoelectric transducers (PZT) have been employed for establishing damage detection processes in SHM systems. However, despite their wide use, there is limited information in the literature regarding important characteristics for SHM applications, such as the shape, dimensions and frequencies to use, which can affect the performance of the system used to detect the damage. This article investigates longitudinal and flexural waves for applications using circular piezoelectric transducers bonded to thin plates. The methodology allows one to obtain optimal frequencies to create and capture both types of waves and understand the influence of the geometric characteristics of these transducers on the damage detection. Numerical simulations are carried out to show that a change in the parameters of the piezoelectric transducers can maximize the waves amplitudes incoming at the sensor. Results from experimental tests are presented to demonstrate the proposed methodology. New equations are introduced and they compute output voltage and determine optimal frequencies to monitor the structure. The findings contribute to establishing a more efficient design of a damage detection process involving plate-like structures in SHM systems based on wave propagation.

Micro-scale residual stress and deformation analysis in bimetal bronze-stainless steel samples produced by laser powder bed fusion technology

Additive manufacturing technologies attract significant interest as a route to fabricate structural elements with complex net shapes. 3D printing may offer the option of combining dissimilar materials within one build, like dissimilar metals in the case of laser powder bed fusion. The strength of bimetallic interfaces formed by immiscible metals such as stainless steel and copper alloys depends on the mechanism of bonding, the presence and nature of defects, and residual stresses, placing the focus of interest on the structure–mechanical performance relationship in the vicinity of the bimetallic interface. In this article, we report an investigation of laser powder bed fusion fabrication of thin plate bimetallic bronze-stainless steel samples. Sample characterization was performed using several techniques including surface topography and fractography, energy dispersive X-ray spectroscopy, electron backscatter diffraction, mechanical testing with digital image correlation mapping of strains during in situ tension inside scanning electron microscope. Spatially resolved evaluation of the local residual stress was carried out using the Korsunsky Focused Ion Beam micro-ring-core drilling method (FIB-DIC). Pure bronze and stainless steel samples fabricated separately possessed good strengths (ultimate tensile strengths of 150 MPa and 850 MPa, respectively) and significant amounts of ductility (local strains to failure of 0.8% and 1.2%, respectively), in spite of the presence of a relatively coarse and porous structure. Although the values for the bimetallic sample were somewhat reduced, they also demonstrated good mechanical properties, with the ultimate tensile strength of 105 MPa and 0.7% ductility. The fracture of bimetal takes place within the bronze at a distance of about 150 μm from the interface. The present report discusses the insights obtained, and charts the pathways towards further improvement of bimetal joint strengths through simple modifications of the laser powder bed fusion printing procedures.

Research on performance test analysis method of mechanical structure based on measured error / virtual simulation

Mechanical errors seriously affect the transmission performance of mechanical structure, especially for high-precision mechanical structure. With the development of virtual simulation technology, the performance test of mechanical structure in virtual environment is gradually applied. Under the background, this paper takes the movable tooth reducer as the research object and puts forward a virtual performance test method by combing test errors with virtual simulation technology. The tooth profile errors of key components of the reducer are obtained by optical scanning, and the simulation test is carried out. Meanwhile, the accuracy of the simulation test is verified by the implementation of vibration test. The results show that both the simulated vibration acceleration and the experimental test vibration acceleration show a double-peak variation trend, and the frequency difference between the two peaks is less than 5%. Therefore, the simulation test method proposed in this paper can effectively evaluate the performance of mechanical structures.

Alternative Load Path Analysis for Determining the Geometric Agreement of a Cable-Stayed Bridge with Steel Truss Girders

The geometric agreement, commonly hailed as load-transferring paths within bridge structures, is significantly crucial to the bridge structural mechanical performance, such as capacity, deformation, and collapse behavior. This paper presents a methodology dependent on alternative load paths to investigate the collapse behavior of a double-pylon cable-stayed bridge with steel truss girders subjected to excess vehicle loading. The cable-stayed bridge with steel truss girders is simplified using a series-parallel load-bearing system. This research manifests that the enforced vehicle loading can be transferred to alternative paths of cable-stayed bridges in different load-structure scenarios. A 3-D finite element model is established utilizing computer software ANSYS to explore the collapse path of cable-stayed bridge with steel truss girders, taking into account chord failure, loss of cables together with corrosion in steel truss girders. The results show that chord failures in the mid-portion of the mainspan result in brittle damage in truss girders or even sudden bridge collapse. Further,the loss of long cables leads to ductile damage with significant displacement.The corrosion in steel truss girders has a highly slight influence on the collapse behavior of cable-stayed bridge. The proposed methodology can be reliably used to assess and determine the vulnerability of cable-stayed bridge with steel truss girders during their service lifetime, thus preventing structural collapses in this type of bridge.

Techno-Assessment of the Use of Recycled Plastic Waste in RE

Effectively consumed plastic waste is an emerging technical and social issue for Australia. Adding plastic waste into construction material and ensuring minimised impact to the mechanical performance of the construction material could bring significant benefits. In this study, plastic waste material was mixed into cement-stabilised rammed earth (RE) material for brick manufacture. Techno framework consisting of compressive strength test and split tensile strength derivation for structural performance assessment and life cycle assessment for determining EE(EE) performance was applied to compare recycled high-density polyethylene (HDPE) added RE with conventional bricks. The compressive properties of different mixtures were studied. The replacement of conventional rock aggregates in stabilised RE brick with recycled plastic waste was found to improve the structural mechanical performance with the developed composition. Following this, an EE analysis was important to assess whether these waste-based bricks can improve environmental performance in a cost-competitive manner while maintaining structural performance. The increase of recycled HDPE in RE was found to likely affect the EE performance of RE, which could possibly be overcome by using less energy-intensive cementitious materials and recycled HDPE.

Following the video surveillance and personal video cameras: New tools and innovations to health monitor the earthquake wave field

Video cameras are becoming essential tools for obtaining real-time information on the mechanical performance of structures and their contents during seismic events as well as information on the moving properties of propagating media, such as tsunamis, landslides, and water sloshing. Their recorded images also provide important clues on human behavior during shaking. In this paper a large set of situations obtained from published YouTube videos, involving structures, natural outfits, human behavior are presented.Video cameras cannot replace laboratory static tests or tests on shaking tables, pseudo-dynamic sub-structure testing, wind tunnels or the channel propagation of waves. However, information that is collected over time and well used is of great value, as it shows the real world without any shortcomings provoked by “similarity laws”, “boundary conditions”, or a “friction and nonlinear hypothesis”. This information should be collected even if it only serves as an “inspiration” to researchers by supporting new ideas that only visualization can provide. This type of information can be considered a random visual health monitoring system.The present paper pretends to show the added value brought by video and personal cameras to the health monitoring of the wave field. We supplement the presented observations with practical recommendations supported in a simple analysis. Once treated, the images can be used in presentations to illustrate different phenomena related to the wave propagation and effects on the built environment and can also serve as an inspiration for mathematical modeling and/or can supply information that otherwise would be lost.

Development of eco-efficient bricks – A life cycle assessment approach

This paper presents the results of techno-economic and environmental performance of interlocking and conventional bricks used for building wall production. Techno eco-efficiency framework consisting of compressive strength test and tensile strength derivation for structural performance assessment and life cycle assessment for determining eco-efficiency performance was applied to determine the Eco-efficient bricks. The replacement of conventional plain bricks with interlocking blocks improved the structural mechanical performance. This construction strategy could substantially reduce construction time, minimize labour cost, and increase mechanical performance. The techno-eco-efficiency framework determined that four out of five interlocking bricks using PT tendon, rebar and mortar could deliver the required level of compressive and tensile strengths with reduced level of environmental impacts in a cost competitive manner. These interlocking bricks are thus known as ‘Eco-efficient’ bricks. However, the conventional bricks are not completely eco-efficient mainly due to higher environmental impacts than the interlocking bricks and they were only found to be eco-efficient in terms of tensile strengths.

A Thompson Sampling Efficient Multi-Objective Optimization Algorithm (TSEMO) for Lithium-Ion Battery Liquid-Cooled Thermal Management System: Study of Hydrodynamic, Thermodynamic, and Structural Performance

Abstract The efficient design of battery thermal management systems (BTMSs) plays an important role in enhancing the performance, life, and safety of electric vehicles (EVs). This paper aims at designing and optimizing cold plate-based liquid cooling BTMS. Pitch sizes of channels, inlet velocity, and inlet temperature of the outermost channel are considered as design parameters. Evaluating the influence and optimization of design parameters by repeated computational fluid dynamics calculations is time consuming. To tackle this, the effect of design parameters is studied by using surrogate modeling. Optimized design variables should ensure a perfect balance between certain conflicting goals, namely, cooling efficiency, BTMS power consumption (parasitic power), and size of the battery. Therefore, the optimization problem is decoupled into hydrodynamic performance, thermodynamic performance, and mechanical structure performance. The optimal design involving multiple conflicting objectives in BTMS is solved by adopting the Thompson sampling efficient multi-objective optimization algorithm. The results obtained are as follows. The optimized average battery temperature after optimization decreased from 319.86 K to 319.2759 K by 0.18%. The standard deviation of battery temperature decreased from 5.3347 K to 5.2618 K by 1.37%. The system pressure drop decreased from 7.3211 Pa to 3.3838 Pa by 53.78%. The performance of the optimized battery cooling system has been significantly improved.

Effect of the Drying Method of Pine and Beech Wood on Fracture Toughness and Shear Yield Stress.

The modern wood converting processes consists of several stages and material drying belongs to the most influencing future performances of products. The procedure of drying wood is usually realized between subsequent sawing operations, affecting significantly cutting conditions and general properties of material. An alternative methodology for determination of mechanical properties (fracture toughness and shear yield stress) based on cutting process analysis is presented here. Two wood species (pine and beech) representing soft and hard woods were investigated with respect to four diverse drying methods used in industry. Fracture toughness and shear yield stress were determined directly from the cutting power signal that was recorded while frame sawing. An original procedure for compensation of the wood density variation is proposed to generalize mechanical properties of wood and allow direct comparison between species and drying methods. Noticeable differences of fracture toughness and shear yield stress values were found among all drying techniques and for both species, but only for beech wood the differences were statistically significant. These observations provide a new highlight on the understanding of the effect of thermo-hydro modification of wood on mechanical performance of structures. It can be also highly useful to optimize woodworking machines by properly adjusting cutting power requirements.

Analysis of Local Damages Effect on Mechanical Responses of Underwater Shield Tunnel via Field Testing and Numerical Simulation

The investigation of concrete structural performance is crucial to maintain the stability of infrastructure. In order to assess structural stability, this work focuses on the development of an integrated framework to detect damaged conditions in the field and analyze their effect on mechanical performance through nondestructive testing (NDT) technology and numerical models. First, a ground penetrating radar (GPR) and an infrared camera work collaboratively to identify the damaged positions of the concrete structure, with parameters calibrated by laboratory experiments. Then, a finite element model is established to study structural mechanical performance based on field conditions and detected results. In addition, the influenced regions induced by local damage are studied under different boundary conditions. As a case study, the devised method was employed in the Nanjing Yangtze River tunnel for stability assessment and disaster prevention. The detected results of the damaged conditions agree well with the actual conditions in the field. Numerical results show that the circumferential stress component is more significant than that observed longitudinally. The effect of local damage on stress implies a positive correlation with the rise of water pressure, in which the maximum stress response to the variation of water level is 45KPa per meter.

Mechanical properties of additively manufactured metal lattice structures: Data review and design interface

With the ever-increasing resolution of metal additive manufacturing processes, the ability to design and fabricate cellular or lattice structures is readily improving. While there are few limits to the variety of unit cell topologies that can feasibly be manufactured, there is little known about the effect that the underlying unit cell topology has on lattice structure mechanical performance. Increased knowledge of lattice structure performance based on the unit cell topology can aid in appropriate unit cell selection to achieve desired lattice structure mechanical properties. The objective in this work is to compile metal additively manufactured lattice structure characterization data found in the literature into Ashby-style plots that can be used to differentiate unit cell topologies and guide unit cell selection. Data gathered from literature encompasses over 69 papers describing 18 different unit cell topologies. Data on mechanical properties such as the effective modulus, Poisson’s ratio, yield strength, buckling strength, and plateau strength, of lattice structures from analytical models based on mathematical derivations, finite element analysis, and experimental characterization was gathered and synthesized. In total, nearly 1650 data points for experimental and finite element analysis were compiled along with a variety of analytical models for 18 different unit cell topologies. The process of gathering the data from the literature along with the assumptions used to compile the data are discussed. A graphical user interface and database were developed that allows for comparison of different lattice structure mechanical properties based on their unit cell topology. The Lattice Unit-cell Characterization Interface for Engineers (LUCIE) provides a simple format to guide engineers, scientists, and others towards understanding the relationships of the unit cell topology and the lattice structure mechanical properties, with the intent of guiding appropriate unit cell selection. Three cases studies are shown for using LUCIE to differentiate unit cell topologies for improved understanding of experimental and simulation-based results (Case Study 1), to identify unit cell topology options for reducing weight while maintaining yield stress or increasing yield stress without reducing weight (Case Study 2), and for quickly narrowing multiple options to an appropriate unit cell topology (Case Study 3).

Out-of-plane mechanical behaviors of a side hierarchical honeycomb

Hierarchical honeycombs have been extensively used as protective devices due to their superior mechanical performance. In this paper, a novel side hierarchical triangular honeycomb (SHTH) constructed by sequentially arranging a certain number of similar subtriangles on the geometrical side of an ordinary triangular honeycomb (OTH) is proposed to enhance structural mechanical performance. Experimental specimens and finite element models of SHTHs are developed to explore their mechanical behaviors under out-of-plane compression, and the numerical models are validated based on the results of crushing tests of SHTHs. Numerical comparisons of the SHTH, OTH and double-triangular honeycomb (DTH) are performed and illustrate that the SHTH has a higher collision force level and better energy absorption than the OTH and DTH due to more stable collapse deformation. Moreover, a parametric investigation of the SHTH is performed to explore the influences of the relative density, hierarchical factor and layout of the honeycomb on crashworthiness. The results show that the crashworthiness of the SHTH is improved with increasing relative density and number of layouts. Furthermore, the stable energy absorption and load bearing efficiency of the SHTH are observed when the hierarchical factor is close to 10. A theoretical model of the SHTH is also derived and validated based on simplified super folding element theory (SSFE) and numerical analysis. The findings of this study provide a new method for designing an energy absorber with excellent protective performance.

Numerical investigation and design of reinforced concrete beams with non-uniform frost damage on the compression and tension sides

This paper aims to investigate the bending behaviour of a reinforced concrete (RC) beam with different non-uniform frost damages. A multi-scale poromechanical approach is developed to build a bridge between the material deterioration process and the structural mechanical performance by considering the global heat and moisture transport and rebar confinement, as well as the local phase changes and poromechanical deformation. The real-time frost damage process is first simulated and experimentally validated for different depths of exposure on both the compression and tension sides and then used for testing the residual bending behaviour. The failure modes, load-carrying capacity and strain distribution of the reinforcement are fairly consistent with the experimental results. The bearing capacity decreases with the increment of the freeze-thaw cycles (FTC) and the frost exposure depth. Reinforcing bars can restrain not only crack propagation but also frost damage. Thus, the bearing capacity of the damaged beam on the compression side drops more than that on the tension side for the same exposure depth. Finally, an indirect method for the use of the equivalent deteriorated mechanical properties is compared with the detailed real-time simulation, and a simple design method is proposed for RC beams with partial frost damage.