Analysis Of Mechanical Structures Research Articles

Structural Design and Dynamic Analysis of Anti-Reversion Mechanism of Feed Mechanism

Because of easy for the bomb-stirring system of feed mechanism to reverse at its non-working position, which can affect the stability of the whole system. Virtual Prototyping Technology can help people to complete the design of overall structure of feed mechanism and anti-reversion mechanism of automaton. ADAMS, one kind of dynamics simulation software, can help to complete the motion characteristics analysis of anti-reversion mechanism, achieving the motion law of mechanism parts and movement dynamic characteristics, as well as verifying the rationality of the design of mechanism.

An Innovative Design and Structural Mechanics Analysis of Artificial Hip Joint

Using finite element (FE) method, this work established and comparatively analyzed the basic femoral head model, and six innovative femoral head models with different micropore surface distribution, aiming to explore the most rational surface morphology to have better effect on artificial hip implant. The inboard and outboard femur, the metal handle, and the femoral head’ stress responses were concerned. As the results showed, compared with type A (original femur head, with “smoothed” surface), the other six shaped femur head design all have reduced the maximal stress with different degrees. However, femur model surface type C arranged with 1mm-diametre distributed in three rows of micropore caused the best effect. Within the scope of the study, both micropore size and arranging way influenced the stress distribution at key components of artificial hip joint, especially the effect of micropore size exceeded arranging way of them. Based on the simulation results, it is proposed the whole rigidity of the artificial femoral head with microporous morphology, was reduced to some degree and therefore reducing the stress shielding effect, decreasing the possibility of embedded part being deformed or flexible, which is beneficial to improving life span of the prosthesis.

3D transient thermomechanical behaviour of a full scale SOFC short stack

Hermetic sealing of planar solid oxide fuel cell components is a critical issue. The long term operation and structural reliability of the fuel cell stacks depend strongly on the thermomechanically induced stress–strain behaviour of the fuel cell stack. These are especially affected through the thermal transients, which the fuel cell stack is subjected to, over time. Hence, the thermomechanical characterisation of the fuel cell stack during thermal cycling is indispensable. The current paper elucidates a fully three dimensional thermomechanical analysis of a planar type SOFC short stack over a whole thermal cycle. A coupled computational fluid dynamics and computational structural mechanics analysis has been performed. Typical stack components i.e., cell component, wire-mesh, metal frame, interconnector plates and sealant materials have been considered. The model represents the physical resolution of the air channels and the manifold regions. The non-linear elasto-plastic behaviour of the metal components as a function of temperature is considered. The study gives an insight about the transient thermal behaviour of a full scale fuel cell stack and its thermomechanical response, determining the mechanisms that trigger the thermomechanically induced stress during the heating-up, operation and shut-down stages.

Resolving the stability and structure of strontium chloride amines from equilibrium pressures, XRD and DFT

Strontium chloride octamine, Sr(NH3)8Cl2, has been shown to be a highly efficient ammonia reservoir for selective catalytic reduction of NOx gases in vehicle exhaust and to hold great potential for indirect hydrogen storage. The possible applications of such metal amines depend explicitly on the conditions for ammonia release and it is thus essential to understand the exact ab- and desorption mechanisms. Here, we apply equilibrium pressure measurements from ammonia desorption, X-ray powder diffraction and density functional theory calculations to identify thermodynamically stable Sr(NH3)Cl2, Sr(NH3)2Cl2 and Sr(NH3)8Cl2 phases. The crystal structures were solved in the space groups Cmcm, Aem2 and Pnma respectively. Controversy regarding the possible existence of a diamine phase is resolved on the basis of a combined structural and thermodynamic analysis of the ammonia release mechanisms, yielding a diamine structure with nearly the same stability as the monoamine. Depending on temperature and pressure, the diamine phase is found to have marginally higher or lower stability than the monoamine phase which explains why the diamine phase is found in some experiments and is not found in others.

Probabilistic fracture mechanics analysis of linear-elastic cracked structures by spline fictitious boundary element method

Abstract The inherent uncertainties in crack geometry, material properties and loadings have large influence on fracture response characteristics of cracked structures. This paper presents the probabilistic fracture mechanics analysis of linear-elastic cracked structures subjected to mixed-mode loading conditions using the spline fictitious boundary element method (SFBEM). The response surface method (RSM) is used to predict the fracture probability of the cracked structure. To determine the unknown coefficients of the response surface function, the SFBEM based on the Erdogan fundamental solutions for infinite cracked plates is adopted to perform deterministic analyses of stress intensity factors (SIFs) corresponding to different test points with given parameters. Numerical examples based on mode-I and mixed-mode crack problems are presented to illustrate the present method. The results show that the predicted failure probability obtained by the present approach is accurate in comparison with the Monte Carlo simulation (MCS) results. Since a much lesser number of numerical tests are required in RSM as compared with that needed in MCS, and since the SFBEM based on the Erdogan fundamental solutions has been used to conduct the numerical tests, reliability analysis of cracked structures can be performed efficiently using the present method.

Electrochemical Redox Mechanism in 3.5 V Li2-xFeP2O7 (0 ≤ x ≤ 1) Pyrophosphate Cathode

Li2FeP2O7 pyrophosphate is the latest phosphate-based polyanionic cathode material operating at 3.5 V (vs Li+/Li). Capable of two-dimensional Li+-ion diffusion, the pyrophosphate has a complex three-dimensional crystal structure, rich in Li–Fe antisite defects. The electrochemical (de)lithiation of pristine Li2FeP2O7 involves permanent structural rearrangement, as reflected by the voltage drop between the first and subsequent charging segments. The current article presents the structural analysis of the electrochemical redox mechanism of Li2FeP2O7 cathode coupling in situ and ex-situ structural characterization. Contrary to previous reports, it involves a single-phase redox reaction during (de)lithiation cycles involving a minimal <2% volume expansion. Further, it forms a rare example of cathode showing positive expansion upon delithiation similar to LiCoO2. The mechanism of single-phase (de)lithiation and related (ir)reversible structural arrangement is elucidated.

Structure Improvement and Mechanical Analysis on Data Transmission Antenna

Data transmission antenna plays an important role in transmitting data from satellite. The structure of antenna consists of four parts, including a feed tube, a reflecting surface, a brace and a adapter. Due to the unreasonable structure design and coarse mechanical analysis, the initial data transmission antenna was broken at the corner of a spiral in the process of random vibration test. In this paper an improvable method is brought up and mechanical analysis is carried out, the result shows that the first frequency raises from 324Hz to 328Hz and the stress root mean square decreases from 62MPa to 37MPa in X-direction random vibration. Of course, the improved antenna passes the random test.

The Optimal Design of Vertical Hammer Mill Based on Pro/E

Vertical hammer mill is widely used in food and feed processing factory. It contains the rotor, sieve plate, machine body, feeding device, discharge device, diver device and etc. Traditional design method used two-dimensional drawings to express three-dimensional information of parts, which was abstract and difficult to be modified. This research utilized 3D software Pro/E to carry out three-dimensional designing, modeling, virtual assemble and motion simulation, and used structural mechanics analysis module Pro/Mechanical to carry out finite element analysis of key parts to optimize design of vertical hammer mill. In the designing process designer can easily modify the parameters, and directly observe the shape, location and movement of parts, which can greatly improve the design efficiency and level.

Structural Analysis of Mechanism with Compound Hinges in Ordinal Single Opened Chain Theory

The coupling degree and structure factor of mechanism are the important parameters for the research of principle of mechanism structure, kinematics and dynamics in the ordinal single opened chain method, This article presents the algorithm of coupling degree for the kinematic chain with compound hinges on the basis of that for the kinematic chain without compound hinges and the dual-color topology graph, through which the mechanism with compound hinges can be decomposed into basic kinematic chains, the correctness of the algorithm has been verified by the practical example.

Improved mechanical properties of retorted carrots by ultrasonic pre-treatments

The use of ultrasound pre-processing treatment, compared to blanching, to enhance mechanical properties of non-starchy cell wall materials was investigated using carrot as an example. The mechanical properties of carrot tissues were measured by compression and tensile testing after the pre-processing treatment prior to and after retorting. Carrot samples ultrasound treated for 10 min at 60 °C provided a higher mechanical strength ( P < 0.05) to the cell wall structure than blanching for the same time period. With the addition of 0.5% CaCl 2 in the pre-treatment solution, both blanching and ultrasound treatment showed synergistic effect on enhancing the mechanical properties of retorted carrot pieces. At a relatively short treatment time (10 min at 60 °C) with the use of 0.5% CaCl 2, ultrasound treatment achieved similar enhancement to the mechanical strength of retorted carrots to blanching for a much longer time period (i.e. 40 min). The mechanism involved appears to be related to the stress responses present in all living plant matter. However, there is a need to clarify the relative importance of the potential stress mechanisms in order to get a better understanding of the processing conditions likely to be most effective. The amount of ultrasound treatment required is likely to involve low treatment intensities and there are indications from the structural characterisation and mechanical property analyses that the plant cell wall tissues were more elastic than that accomplished using low temperature long time blanching.

Structural Study of Arch Bridge with a Span of 600m Part I: Trial Design

The trial design of a proposed arch bridge with a span of 600m is made. Static performance, static stability, and vibration characteristics of this type of bridge are discussed by structural mechanical analysis. The project’s characteristics in finish state are summarized, and it is proved to be available to use this type of arch bridge at the span of 600m.

Non-Destructive Evaluation of the Effects of Combined Bisphosphonate and Photodynamic Therapy on Bone Strain in Metastatic Vertebrae Using Image Registration

Skeletal metastases most frequently affect the vertebral column and may lead to severe consequences including fracture. Clinical management of skeletal metastases often utilizes a multimodal treatment approach, including bisphosphonates (BPs). Previous work has demonstrated the synergistic potential of photodynamic therapy (PDT) in combination with BP in treating osteolytic disease through structural, histologic, and destructive mechanical testing analyses. Recent work has developed and validated image-based methods that may be used to non-destructively determine mechanical stability in whole bones, and enable their use for additional (i.e. histologic) analysis. In this work we use an intensity-based 3D image registration technique to compare the strain patterns throughout untreated control and BP + PDT treated rnu/rnu rat spinal motion segments with osteolytic metastases. It was hypothesized that the combination treatment will reduce average and maximum strain values and restore the pattern of strain to that of healthy vertebrae. Mean, median, and 90th percentile strains in the control group were significantly higher than the treatment group. High strain areas in both groups were observed around the endplates; in the control group, large areas of high strains were also observed around the lesions and adjacent to the dorsal wall. Absence of high strains adjacent to the dorsal wall (similar to healthy vertebrae) may correspond to a reduced risk of burst fracture following BP + PDT therapy. This study demonstrates the application of non-destructive image analysis to quantify the positive mechanical effects of combined BP + PDT treatment in the metastatic spine.

Finite element implementation for computer‐aided education of structural mechanics: Frame analysis

AbstractInstructional tools for the computer‐aided education of structural analysis have been implemented as an extension of a finite element analysis program, VisualFEA. They are devised to promote understanding in structural analysis, and stimulate interest in the subject by substantiating the conceptual principles and visually exhibiting the complex computational processes with the aid of interactive computer graphics. In lieu of manipulation with pre‐supplied conditions or the input of assumed data, the instructional tools are operated through a real and practical process of structural analysis from the creation of modeling data to the presentation of solution results. The basic principles, computing formulae, and methods of analysis in structural mechanics are simulated for instructional purposes on the basis of finite element technology. VisualFEA has a number of educational functions for use in teaching and learning structural analysis. Among them, only those related to frame analysis are introduced in this article. There are numerous programs for frame analysis. However, the educational features described in this article are not common in any other programs for similar purposes. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:387–409, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.10.1002/cae.20563

The influence of quantity and distribution of cooling channels of turbine elements on level of stresses in the protective layer TBC and the efficiency of cooling

The modern turbine engines are designed to operate in the temperatures of combustion gases, of order 1800–2000K, which considerably exceed admissible values for applied metals. Therefore turbine elements should be protected against raw thermal environment to keep the acceptable lifetime and standards of safety. There are two ways of protection: (1) different cooling systems of the turbine elements and (2) thermal barrier coatings (TBC).As an example of the turbine element a nozzle guide vane was analysed. It was protected by TBC layer of 0.1mm thickness and several systems of cylindrical cooling channels. Different numbers of the cooling channels, their distribution as well as diameters were considered. The aim of the work was estimation of: the efficiency of cooling vanes, the level of Mises stresses in the vane and the influence of the protective layer TBC on the thermal response of the turbine element. All considered variants were compared.In the simulation real boundary conditions were applied, i.e. the temperature of combustion gases was 1600K and inlet velocity of cooling gas 1.23m/s. For delimitation of temperature fields the Computational Fluid Dynamics (CFD) analysis was applied, using the programme ANSYS Fluent. The turbulence model of flow k–ɛ was applied in numerical calculations and the temperature distributions were established. Computational Structural Mechanics (CSM) analysis was done with ABAQUS, taking into account temperature fields. It lead to calculation of the stress distributions in the blade and in the protective layer TBC. The most important stress concentrations took place near cooling holes, which had significant influence on endurance of the turbine elements.

A c-di-GMP Effector System Controls Cell Adhesion by Inside-Out Signaling and Surface Protein Cleavage

In Pseudomonas fluorescens Pf0-1 the availability of inorganic phosphate (Pi) is an environmental signal that controls biofilm formation through a cyclic dimeric GMP (c-di-GMP) signaling pathway. In low Pi conditions, a c-di-GMP phosphodiesterase (PDE) RapA is expressed, depleting cellular c-di-GMP and causing the loss of a critical outer-membrane adhesin LapA from the cell surface. This response involves an inner membrane protein LapD, which binds c-di-GMP in the cytoplasm and exerts a periplasmic output promoting LapA maintenance on the cell surface. Here we report how LapD differentially controls maintenance and release of LapA: c-di-GMP binding to LapD promotes interaction with and inhibition of the periplasmic protease LapG, which targets the N-terminus of LapA. We identify conserved amino acids in LapA required for cleavage by LapG. Mutating these residues in chromosomal lapA inhibits LapG activity in vivo, leading to retention of the adhesin on the cell surface. Mutations with defined effects on LapD's ability to control LapA localization in vivo show concomitant effects on c-di-GMP-dependent LapG inhibition in vitro. To establish the physiological importance of the LapD-LapG effector system, we track cell attachment and LapA protein localization during Pi starvation. Under this condition, the LapA adhesin is released from the surface of cells and biofilms detach from the substratum. This response requires c-di-GMP depletion by RapA, signaling through LapD, and proteolytic cleavage of LapA by LapG. These data, in combination with the companion study by Navarro et al. presenting a structural analysis of LapD's signaling mechanism, give a detailed description of a complete c-di-GMP control circuit—from environmental signal to molecular output. They describe a novel paradigm in bacterial signal transduction: regulation of a periplasmic enzyme by an inner membrane signaling protein that binds a cytoplasmic second messenger.

Thermal stress prediction in divertor cooling finger using the local heat transfer distribution

An approach that combines computational fluid dynamics (CFD) and structural mechanics simulation is used for evaluating stresses in a divertor cooling finger. Local distributions of heat transfer coefficient (HTC) between the helium and inner surface of the thimble are used as a boundary condition for the structural mechanics analysis. Stresses calculated with a realistic non-homogeneous HTC distribution are compared with the results where averaged HTC values in three representative zones of inner thimble surface are used. The obtained maximum stresses are considerably higher in the case of realistic non-homogeneous HTC boundary condition. The highest thermal stresses in the tile–thimble assembly are obtained on the thimble inner surface, in the region where the highest thermal gradients due to jet cooling can be observed. The results also show that tetrahedral based finite element model underestimate the computed stresses, especially when a coarse mesh is used.

Patran Based Results Processing System for Spacecraft Mechanical Analysis

Regarding the basic method and process of current spacecraft structural mechanics analysis, the paper used the secondary development language of Patran (PCL) to automatically extract the finite element model information such as mass property, material property, element property etc; According to the mission of spacecraft mechanical analysis, the obtained results were re-solved to get the required information. Executable program was written in Java to transform the extracted results into specific forms in accordance with the predetermined templates. Finally, using the forms and menu libraries provided by PCL language, graphical interfaces were created to integrate all the functions and procedures in to Patran so that the whole process could be accomplished through an intuitive graphical interface, which was user-friendly. Adoption of the result processing system on specific examples verified the feasibility of the system.

Structural Behavior Analysis of Masonry Stone Pagoda Considering the Inner Construction Types of Stylobate

We have many difficulties in the modeling and analysis of masonry stone pagoda structure because this structure has the discontinuum behavior characteristics, compared with the general continuum structures. Also, we need to consider the inner construction types of stylobate for the reasonable analysis of structural mechanism of masonry stone pagoda. Most masonry stone pagoda structures built in Korea are largely classified into three parts such as top part, body part and stylobate. Specifically, the stylobate takes a very important structural part, performing the role of foundation in ordinary structures, and the reduction of stylobate’s bearing capacity has great influence on the safety of structure. As for stylobate, the construction types of inner Jeoksim result in the different structural behaviors. Therefore, this study selects three-story stone pagoda in Goseon-sa temple site that shows the typical type of stone pagoda structure in Korea. Also, this study investigates the construction types of stylobate and evaluates the structural and mechanical behaviors of masonry stone pagoda structure according to many application variables of stylobate’s Jeoksim forms. To this end, we considers the contact surface and block modelling for the discontinuum elements through the discrete element method and finite element method. Through the comparison of analysis results, we can find out the load transfer mechanism according to the inner Jeoksim types of stylobate.

Tetrapyrrole binding affinity of the murine and human p22HBP heme-binding proteins

We present the first systematic molecular modeling study of the binding properties of murine (mHBP) and human (hHBP) p22HBP protein (heme-binding protein) with four tetrapyrrole ring systems belonging to the heme biosynthetic pathway: iron protoporphyrin IX (HEMIN), protoporphyrin IX (PPIX), coproporphyrin III (CPIII), coproporphyrin I (CPI). The relative binding affinities predicted by our computational study were found to be similar to those observed experimentally, providing a first rational structural analysis of the molecular recognition mechanism, by p22HBP, toward a number of different tetrapyrrole ligands. To probe the structure of these p22HBP protein complexes, docking, molecular dynamics and MM–PBSA methodologies supported by experimental NMR ring current shift data have been employed. The tetrapyrroles studied were found to bind murine p22HBP with the following binding affinity order: HEMIN > PPIX > CPIII > CPI, which ranged from −22.2 to −6.1 kcal/mol. In general, the protein–tetrapyrrole complexes are stabilized by non-bonded interactions between the tetrapyrrole propionate groups and basic residues of the protein, and by the preferential solvation of the complex compared to the unbound components.

Investigation of a polymer metal inter‐locking technology for use in load‐bearing automotive components

PurposeThe purpose of this paper is to propose and analyse computationally a new concept for mechanical interlocking between metal and plastics. The approach utilizes some of the ideas used in the spot‐clinching joining process and is appropriately named “clinch‐lock polymer metal hybrid (PMH) technology.”Design/methodology/approachA new approach, the so‐called “direct‐adhesion” PMH technology, is recently proposed Grujicic et al. to help meet the needs of automotive original equipment manufacturers and their suppliers for a cost‐effective, robust, reliable PMH technology which can be used for the manufacturing of load‐bearing body‐in‐white (BIW) components and which is compatible with the current BIW manufacturing‐process chain. Within this approach, the necessary level of polymer‐to‐metal mechanical interconnectivity is attained through direct adhesion and mechanical interlocking.FindingsIn an attempt to fully assess the potential of the clinch‐lock approach for providing the required level of metal/polymer mechanical interlocking, a set of finite‐element based sheet‐metal forming, injection molding and structural mechanics analyses is carried out. The results obtained show that stiffness and buckling resistance levels can be attained which are comparable with those observed in the competing injection over‐molding PMH process but with an ∼3 percent lower weight (of the polymer subcomponent) and without the need for holes and for over‐molding of the free edges of the metal stamping.Originality/valueThe paper presents a useful discussion of clinch‐lock joining technology's potential for fabrication of PMH load‐bearing BIW components.