Analysis Of Mechanical Structures Research Articles

Structural Design and Mechanical Properties Analysis of Fused Triply Periodic Minimal Surface Porous Scaffold

Structural Design and Mechanical Properties Analysis of Fused Triply Periodic Minimal Surface Porous Scaffold

Structural and mechanical modeling of density and stiffness of hybrid composite reinforcement

A structural-mechanical analysis of the influence of high-modulus fibers on the physical and mechanical properties of hybrid composite reinforcement has been performed. In the introduction, the need for a detailed physical and mechanical analysis of the properties of combined composite reinforcement is updated due to the insufficient study of many issues. Despite the progress made in the field of modeling structural composite reinforcement and the development of its production technology, many issues related to its strength are not well understood, which is the main constraint in the adoption of scientifically based standards for assigning mechanical characteristics, control and testing methods. The aim of the study is to develop methods and use them to carry out a structural-mechanical analysis of the influence of the type and content of high-modulus fibers on the density and elastic moduli of hybrid composite reinforcement. In the main part of the article, mathematical modeling of the possible mechanism of destruction of combined rods with different content of high-modulus reinforcing fibers and base fibers was carried out. At the first stage, a structural-mechanical analysis of the factors contributing to the increase in the moduli of longitudinal elasticity described by the “rule of mixtures” was carried out. In this case, the influence of the mass and volume content of high-modulus fibers on the density of the hybrid composite, as well as its moduli of longitudinal and transverse elasticity, was modeled. The results obtained make it possible to modernize the method of predictive assessment of the density and elasticity moduli of composite building reinforcement and can be used by engineering and technical workers of manufacturers and consumers of such reinforcement, as well as in the educational process in the training of engineering personnel of the construction profile.

Sensitivity study of numerical and geometrical parameters for structural mechanical analyses in the automatic design process of hydraulic machines

In the present paper a sensitivity study of numerical and geometrical parameters related to structural mechanical analyses of a hydraulic machine is presented. The sensitivity study is carried out for the blades of two different hydraulic machines, a propeller blade of a submersible vehicle and a runner blade of a kinetic river turbine. The focus of this work is on static structural mechanical analyses, which are performed with the open source finite element program CalculiX. Parameters for the sensitivity study are numerical parameters like the global mesh size as well as the local mesh refinement at certain locations of the blade. Furthermore, the sensitivity of geometrical parameters such as the blade thickness at different locations or the shape of the fillet is investigated. The results of the sensitivity study show that the numerical parameters have a small influence compared to the geometrical parameters. The most dominant geometrical parameter is the blade thickness at the hub. In case of a high load due to the centrifugal force, the influence of the blade thickness at the tip of the blade increases.

Rendering Abstract Notation of Kinematic Chains to Modified Franke’s Notation Form

To bring about innovation in the development of any product, it is required that the designer explores multitude design concepts right at the conceptual design phase of the product development cycle. At this phase, results of structural synthesis and analysis of mechanisms have been shown to serve as an invaluable tool in the attempt to infuse novelty in the design being conceptualized. There are several studies available in literature dealing with structural enumeration of kinematic chains. Invariably, all these studies culminate in reporting the results in an abstract form such as link adjacency matrix or its simpler variants like joints’ lists, etc. Certainly, it will be more useful to designers if the chain were reported in the pictorial form since it will be more intuitive for designers to fruitfully relate what is in his mind as an unformulated idea to what is directly visible as a sketch. This paper presents the results of a computer based method that converts link adjacency matrix into modified Franke’s notation format. The way to draw full-fledged chain from its modified Franke’s notation form is explained. Chains containing 8 or more links and possessing 1 to 5 freedoms have been sketched and made available in the form of a PDF file.

Preparation and Characterization of 3D Printed Porous 45S5 Bioglass Bioceramic for Bone Tissue Engineering Application.

Three-dimensional (3D) printing technology provides advanced technical support for designing personalized bone tissue engineering scaffold. In this study, two porous diffusing models, namely, average and layered perforated cylindrical scaffolds, were designed for bone tissue engineering scaffold. The designed models were fabricated by liquid crystal display mask stereolithography printing. Structural design and finite element mechanical analysis were conducted. 45S5 bioglass was selected as the raw material for preparing the printing inks for bone tissue engineering scaffolds. By adjusting the viscosity and temperature of the slurry, the maximum proportion of 45S5 bioglass (40 wt%) was added into the photosensitive resin for preparing 3D printing slurry. Our results indicated that an optimized sintering condition includes the debinding rate (0.5°C/min), and temperature raising rate (5°C/min) and sintering temperature (1100°C) were proposed to sinter 45S5 bioceramic scaffolds. The amorphous 45S5 bioglass showed good crystallization after sintering, and the scaffold porous structure showed good integrity. Micropores were observed in the struts which interconnected with each other. Moreover, the porosities were tested as 57% and 45% with a uniform pore distribution. The shrinkage rate was about 10% during sintering process due to binder burning and crystallization shrinkage. The compressive strength of the sintered scaffold was 0.71 ± 0.048 MPa and 2.13 ± 0.054 MPa, respectively, which are consistent with the finite element mechanical analysis simulation results. In conclusion, the layered perforated 45S5 bioglass scaffold shows good mechanical properties and porosity, indicating that it could be a promising candidate for bone tissue engineering.

Spatial distribution characterization of the Temperature-induced gradient viscoelasticity inside asphalt pavement

Under the influence of continuous periodic changes of various meteorological factors, there will be an inhomogeneous temperature field inside the asphalt pavement, which will cause a continuous gradient viscoelasticity of asphalt concrete with depth. In order to perform the structural mechanics analysis accurately, the temperature field gradient effect and the temperature-induced gradient viscoelasticity distribution inside the asphalt pavement should be revealed first. In this research, based on the heat conduction theory, a temperature field finite element analysis (FEA) model of a semi-rigid base asphalt pavement was established to investigate the distribution behavior of the temperature gradient along the depth. Dynamic modulus tests were conducted to survey temperature effect on the viscoelastic parameters of asphalt concrete. Eventually, the intrinsic relationship between temperature, depth, and viscoelastic parameters was integrated, and the relaxation time shift method was proposed to quantitatively characterize the temperature-induced gradient viscoelasticity at different depths. It is found that the temperature varies in a cubic parabolic fashion along the depth under the most significant positive and negative temperature gradient conditions. The relaxation time shift method can be effectively used to characterize the distribution of the relaxation modulus and relaxation time spectrum of asphalt concrete under the influence of temperature. It is easy to be programmed to fully consider the inhomogeneous temperature field, and applicable to both traditional and gradient FEA. The change of parameters of generalized Maxwell model for asphalt concrete with temperature is essentially the result of relaxation spectrum shifting along the relaxation time axis at different temperatures. When the temperature is high, the viscosity decreases, the relaxation spectrum shifts to the direction of decreasing relaxation time, the relaxation modulus of asphalt concrete decreases, and vice versa.

Experimental study of admixture on Bentonite clay reinforced concrete as a partial substitute to cement

The mortar mixtures were prepared in various proportioned with cement to sand ratio of 1:3 and 1:4. The reinforced concretes were cast for the same flow level but different percentages of clay (0, 5, 10 & 15%) dosage. The prepared motor concrete subjected for structural study and mechanical property analysis. In FTIR spectra shows predominant peaks are observed the presence of admixture and clay in the concrete motor. The XRD spectra indicates the formation tetrahedrally arrangement of silicate and octahedrally arrangement of aluminate groups in clay mixed concrete. The surface morphology significantly improved upon adding of different admixture as examined in SEM image. The mechanical study revealed that the compressive strength increases with increase in clay percentages up to C-2 (10 wt %) due to the strong adhesion because of mixture of water reduce and water repellent which makes better compact and reduce porosity. The addition of slump flow improved due to presence of polycarboxylate ether and the evident workability loss started after the resting time of 25 min.

An Overview of Structural Design, Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser

Offshore oil and gas development plays an important part in the global energy sector. Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system. Because of the randomness and uncertainty of wave and current loads in the ocean environment, the structural design and mechanical analysis of the marine equipment can be highly complicated. Therefore, this paper reviews the recent works of the theoretical model, numerical simulation, and experimental test in three research areas: hydrodynamic analysis of offshore platforms, structural mechanics analysis of flexible pipe and cable, and monitoring technology of offshore floating structures under marine loads. By analyzing their main research methods and key technical difficulties, this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines. Also, China is relatively backward in the design of marine floating platform, the design, analysis and testing of flexible pipeline and cable, as well as the marine equipment prototype monitoring technology research. Calling for breakthroughs at the earliest possible stage in the above fields, prime research should be focused on and strategic planning should be made to deal with “key areas and stranglehold problems”. It is of great significance for the development of China’s deep-sea energy and resource development of independent technology and on time to achieve the “carbon peak” national strategic objectives.

Four-Coordinate Fe N2 and Imido Complexes Supported by a Hemilabile NNC Heteroscorpionate Ligand.

Inspired by mechanistic proposals for N2 reduction at the nitrogenase FeMo cofactor, we report herein a new, strongly σ-donating heteroscorpionate ligand featuring two weak-field pyrazoles and an alkyl donor. This ligand supports four-coordinate Fe(I)-N2, Fe(II)-Cl, and Fe(III)-imido complexes, which we have characterized using a variety of spectroscopic and computational methods. Structural and quantum mechanical analysis reveal the nature of the Fe–C bonds to be essentially invariant between the complexes, with conversion between the (formally) low-valent Fe-N2 and high-valent Fe-imido complexes mediated by pyrazole hemilability. This presents a useful strategy for substrate reduction at such low-coordinate centers and suggests a mechanism by which FeMoco might accommodate the binding of both π-acidic and π-basic nitrogenous substrates.

Mechanical and hydrodynamic effects of stent expansion in tapered coronary vessels

Percutaneous coronary intervention (PCI) has become the primary treatment for patients with coronary heart disease because of its minimally invasive nature and high efficiency. Anatomical studies have shown that most coronary vessels gradually shrink, and the vessels gradually become thinner from the proximal to the distal end. In this paper, the effects of different stent expansion methods on the mechanical and hemodynamic behaviors of coronary vessels and stents were studied. To perform a structural-mechanical analysis of stent implantation, the coronary vessels with branching vessels and the coronary vessels with large bending curvature are selected. The two characteristic structures are implanted in equal diameter expansion mode and conical expansion mode, and the stress and mechanical behaviors of the coronary vessels and stents are analyzed. The results of the structural-mechanical analysis showed that the mechanical behaviors and fatigue performance of the cobalt-chromium alloy stent were good, and the different expansion modes of the stent had little effect on the fatigue performance of the stent. However, the equal diameter expansion mode increased distal coronary artery stress and the risk of vascular injury. The computational fluid dynamics analysis results showed that different stent expansion methods had varied effects on coronary vessel hemodynamics and that the wall shear stress distribution of conical stent expansion is more uniform compared with equal diameter expansion. Additionally, the vortex phenomenon is not apparent, the blood flow velocity is slightly increased, the hydrodynamic environment is more reasonable, and the risk of coronary artery injury is reduced.

Structural analysis of ancient Chinese textile mechanisms

Abstract. China is one of the first countries that produced textiles in the world. It has designed and developed a variety of equipment to facilitate textile work, for instance, reeling wheels for fiber processing, treadle spinning wheels for spinning, and looms for weaving cloth. These textile mechanisms can be found in the literature, and there are physical objects left as well. However, due to unclear descriptions of the transmission modes in the records and illustrations, as well as the long history and vast area of their use, a variety of designs with different structures may have been produced. Based on the generalized kinematic chain concept, this paper briefly describes the historical development of textile mechanisms in ancient China and analyzes the structures of mechanisms, such as reeling wheels, treadle spinning wheels, and looms. Finally, it explores the degree of freedom of the mechanisms to find feasible designs in line with functional requirements.

Structural-mechanics analysis of the 10g transformer impact

Transportation of the power transformers from the site of production to the site of the exploitation is very complex and sensible task. During transportation, the transformer can be subjected to a variety of different impacts registered either during railway transportation or during on/off loading. The transformer should be designed to sustain the high accelerations appearing often during transportation. Transformer are usually equipped with the impact recorder to registry the acceleration behavior during the transport. In the current paper, we give an overview on the structural-mechanics analysis of 10g impact on the power transformer registered during the railway transportation of the transformer from Canada to US.

Structural dimension optimization and mechanical response analysis of fabricated honeycomb plastic pavement slab

Structural dimension optimization and mechanical response analysis of fabricated honeycomb plastic pavement slab

Structural mechanics analysis of bolt joint of rigid flexible coupling manipulator

As the key connecting part of the rigid flexible coupling manipulator, the structural dynamic characteristics of the bolted joint are analyzed by using the joint simulation technology of pro/e and ANSYS. Based on the spring equivalent principle, the finite element equivalent model of bolt joint is established, the relationship equation between contact surface pressure and bolt preload is derived, and its stress state is analyzed; Based on the micro convex deformation model and Hertz contact theory, the tangential stiffness equation and normal stiffness equation of the bolted joint are derived respectively. The three-dimensional model of the bolted joint is established by using pro/e and imported into ANSYS for joint simulation. The simulation experiments reveal the influence of bolt joint vibration characteristics under different conditions from the aspects of bolt diameter, pre tightening force, bolt group number and bolt distribution. The conclusions have important engineering value for the structural optimization of rigid flexible coupling manipulator.

Determining of the Fatigue Crack Growth Rate of HSLA Steel at Room Temperature

Welded joint is a critical region of a welded structure and fracture mechanics analysis is inevitable in the structural integrity assessment of all welded structures. This paper shows the determining of parameters of the fatigue crack for constituents of welded joints produced of high strength low alloyed steel. The applied methodology refers to the Paris relation where the link was established between the variable load quantity or the corresponding stress intensity factor range and crack growth per cycle. Results have shown that the position of the notch and crack initiation affect the values of the stress intensity range of fatigue threshold ΔKth and parameters in the Paris’ equation. This is mostly expressed when determining growth parameters of the fatigue crack in heat affected zone of HSLA steel, where different changes of growth speed of the fatigue crack clearly express differences in structure of the crack pass.

Key Component Capture and Safety Intelligent Analysis of Beam String Structure Based on Digital Twins

In the construction process of beam string structures, the environmental effect and corresponding mechanical properties of the structure are complex. The problem of the misjudgment of structural safety performance caused by the uncertainty of a structural mechanical parameter analysis under various factors needs to be solved. In this study, a method for capturing key components and an intelligent safety analysis of beam string structures based on digital twins (DTs) was proposed. Combined with the characteristics of DTs mapping feedback, a component capture and security analysis framework was formed. Driven by twin framework, multi-source data for structural safety analysis were obtained and the parameter association mechanism established. Considering the space-time evolution and the interaction between the virtual and real elements of the construction process, a multidimensional model was established. Driven by the Dempster–Shafer (D–S) evidence theory, the fusion of structural mechanics parameters was carried out. The safety of the structure was analyzed intelligently by capturing key structural components, thereby providing a basis for the safety maintenance of the structure. The integration of DTs modeling and multi-source data improves the accuracy and intelligence of structural construction safety analysis. In the analysis process, capturing the key components of the structure is the core step. Taking the construction process of a string supported beam roof (symmetrical structure) in a convention and exhibition center as an example, the outlined research method was applied. Based on DTs and D–S evidence theory, the variation degree of mechanical parameters of various components under temperature was determined. By comprehensively investigating the changes of various mechanical parameters, the key components of the structure were captured. Thus, the intelligent analysis of structural safety was realized. The comparison of data verified that the intelligent method can effectively analyze the safety performance of the structure.

Land access mechanisms of Soweto farmers: Moving beyond legal land tenure for urban agriculture

Legal land tenure is often understood as an essential asset underpinning urban agriculture. However, the global land rights discussion recently moved away from a strict emphasis on legality towards a wider acknowledgement of the multidimensionality of land rights and land tenure. Based on the semi-structured interviews with farmers of Soweto at gardens in institutions and open-space gardens, and key informants we explore the mechanisms by which farmers gain, control, and maintain access to land with the aim to extend the evidence on the importance of social relations and their role in land tenure of small-scale urban farmers. Results of an in-depth qualitative analysis of structural and relational mechanisms of access to land show that farmers’ identity and ability to create and navigate through the complex web of social relations represents a vital formative force for land tenure. Building on our findings, we invite policy makers to enhance the agenda on land allocation for urban agriculture by preserving and fortifying the existing social networks and relationships. Such an approach allows for enlarging the spectrum of benefits provided by farmers to their community and vice versa, as well as for strengthening farmers’ self-esteem and internal motivation for engagement in urban agriculture. Therefore, our paper supports moving beyond the narrow notion of legal tenure for urban agriculture and embracing its more inclusive understanding by acknowledging social relations and their importance for farmers’ own perception of their land tenure.

Weakly-singular symmetric Galerkin boundary element method in thermoelasticity for the fracture analysis of three-dimensional solids

The Symmetric Galerkin Boundary Element Method has demonstrated significant advantages for the fracture mechanics analysis of three-dimensional solid structures. However, when dealing with structures in thermal environments, strongly-singular domain integrals resulting from the temperature field require meshing of the interior of the domain. In this paper, formulation and implementation of the weakly-singular SGBEM of three-dimensional thermoelastic intact and cracked solids are presented where temperature-induced domain integrals are transformed into boundary integrals. The strong singularity of these temperature-induced integrals is reduced to the weak singularity by exploring the feature of double-layer surface integrals in the SGBEM. Obtained temperature-induced boundary integrals affect only the right-hand-side vector of the SGBEM equation, and therefore the advantages of the SGBEM, such as the symmetry of the stiffness matrix, are retained. Several examples of three-dimensional solids with or without cracks subjected to thermal loadings are presented to validate the developed methods. Advantages and disadvantages of SGBEMs with different temperature-induced boundary integrals are also discussed.

Topology optimization of the compliant mechanisms considering curved beam elements using metaheuristic algorithms

Compliant mechanisms use the flexibility of the limbs for movement and are produced monolithic, without any conventional joint. These flexible mechanisms have wide applications in several fields such as sensors, grippers, parallel mechanisms, micro-electro-mechanical systems, high-precision devices, and biomedical and surgery robots. Topology optimization is regarded as one of the most frequently used approaches for designing compliant mechanisms. The present study aimed to develop the ground structure approach by meshing the design domain using curved beam elements. Moreover, it seeks to implement three different metaheuristic algorithms, including the genetic algorithm, the imperialist competition algorithm, and the equilibrium optimizer for the topology optimization problem. The structural analysis of the compliant mechanism is necessary for determining the values of the objective functions for the optimization process. In the present study, the finite element method was used to analyze the obtained compliant mechanism. Based on the results, an optimum compliant mechanism with both straight and curved beam elements had better performance compared with a compliant mechanism with only straight beams.

In-situ construction of high-modulus nanospheres on elastomer fibers for linearity-tunable strain sensing

A flexible strain sensor is developed via one-step in-situ construction of stiff PVDF nanospheres on the surface of TPU fibers via polymeric phase and morphology control technology. It enables tunable linear sensing to strain thanks to the restricting of quick crack propagation. • Flexible fiber mat strain sensors of heterogeneous structures are developed. • The heterogeneous structure is consisted of stiff PVDF nanospheres on TPU fibers. • The structure can restrict quick micro-crack propagation throughout fiber surface. • The sensor with high-density nanospheres shows very good linearity. Wearable strain sensors with high sensitivity and linear resistance signal response to strain are urgently demanded for human–machine interface, which can be tuned by introducing uneven surface mechanics distribution onto fiber surfaces via structural heterogeneity for fibrous elastomer fiber mat sensors. Yet it is still of great challenge to build micro- or nano-scale heterogeneous structures on fiber surfaces in a facile and scalable way without using templates. Herein, we report a plastic nanosphere-decorated elastomer fiber mat strain sensor with a zoned surface strain energy release characteristic, designed based on analysis of material match and structural mechanics. Surface mechanics analysis confirms that the as-designed sensor shows a controllable strain energy release area, significantly improving sensing stability thanks to effective restriction of micro-crack propagation in conductive pathways. In particular, fibrous mat sensor with high-density nanospheres shows very low fluctuation in strain sensitivity variation (±0.05 for strain ≤ 30 %), i.e., good linearity in the resistance response to strain, while that for the control sensor is ± 10.0 for strain ≤ 16 %. Such a fiber mat strain sensor can not only be applied for real-time sensing of object deformations for human–machine interface and intelligent control, but also in hydrophobic porous elastomeric packaging materials and triboelectric devices.