Application of the Sub-Model Method in the Engine Strength Analysis

On the basis of introducing the fundamental theory and the basic analysis steps of the sub model method, the strength of the new engine complex assembly structure was analyzed according to the properties of the engine structures, some of the key parts of the engine were analyzed with refined mesh by sub model method and the error of the FEM solution was estimated by the extrapolation method. The example showed that the sub model can not only analyze the comlex structures without the restriction of the software and hardware of the computers, but get the more precise analysis result also. This method is more suitable for the strength analysis of the complex assembly structure.

Wave load computation in direct strength analysis of semi-submersible platform structures

A wave load computation approach in direct strength analysis of semi-submersible platform structures was presented in this paper. Considering the differences in shape of pontoon, column and beam, the combination of accumulative chord length cubic parameter spline theory and analytic method was adopted for generating the wet surface mesh of platform. The hydrodynamic coefficients of platform were calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for platform with low forward speed. The equation of platform motions was established and solved in frequency domain, and the responses of wave-induced loads on the platform can be obtained. With the interpolation method being utilized, the pressure loads on shell elements for finite element analysis (FEA) were converted from those on the hydrodynamic computation mesh, which pave the basis for FEA with commercial software.A computer program based on this method has been developed, and a calculation example of semi-submersible platform was illustrated.Analysis results show that this method is a satisfying approach of wave loads computation for this kind of platform.

Installation Strength Analysis of Subsea Flowline Jumpers

A subsea flowline jumper （FJ） is a basic connected component for the wet oil tree, subsea pipeline and riser base, and it plays an irreplaceable role in the subsea production system. During the installation of FJ, collisions often happen between FJ and other equipment, which may cause serious damage. Besides, as the operating water depth increases, the demand for the installation equipments, such as the crane and winch, will increase. The research of deepwater FJ installation in China is still in the primary stage, thus an installation method for the deepwater FJ is proposed in this paper. Finite element models of a typical M-shaped FJ installation system are built to simulate the installation procedures. Analysis results show that the installation steps designed are feasible and valid for the deepwater FJ. In order to ensure the safety of the installation process, the collision-sensitive analysis for the FJ is conducted, and results show that it is necessary to set the pick up speed at a proper value, in order to avoid collision in the installation process. Besides, the mechanical characteristics of FJ during the installation are investigated under a range of environmental conditions and it is found that the maximum stress of the FJ always happens at its central position. The basic requirements for the installation equipment are also obtained through the analysis of the main installation steps.

An Integrated Structural Strength Analysis Method for Spar Type Floating Wind Turbine

An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper,and technical issues related to turbine structure modeling and stress combination are also addressed.The NREL-5MW ＂Hywind＂ Spar type wind turbine is adopted as study object.Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool,FAST,on the purpose of obtaining the dynamic characteristics of the floating wind turbine,and determining parameters for design load cases of finite element calculation.Then design load cases are identified,and finite element analyses are performed for these design load cases.The structural stresses due to wave-induced loads and wind-induced loads are calculated,and then combined to assess the structural strength of the floating wind turbine.The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

Strength analysis of molten salt tanks for concentrating solar power plants

Promoting the development of concentrating solar power(CSP)is critical to achieve carbon peaking and carbon neutrality.Molten salt tanks are important thermal energy storage components in CSP systems.In this study,the cold and hot tanks of a 100 MW CSP plant in China were used as modeling prototypes.The materials and geometric models were determined based on related specifications and engineering experience.Mechanical characteristics of the tanks under steady condition,including the deformation,stress distribution,and stress concentration,were simulated and calculated.Furthermore,the strength of the tank walls was evaluated.The findings can be used as a reference for designing the molten salt storage tank and reducing the risk during the operation.

Multi-scale strength analysis of bolted connections used in integral thermal protection system

Efficient and accurate strength analysis of bolted connections is essential in analyzing the integral thermal protection system（ITPS） of hypersonic vehicles, since the system bears severe loads and structural failures usually occur at the connections. Investigations of composite mechanical properties used in ITPS are still in progress as the architecture of the composites is complex. A new method is proposed in this paper for strength analysis of bolted connections by investigating the elastic behavior and failure strength of three-dimensional C/C orthogonal composites used in ITPS. In this method a multi-scale finite element method incorporating the global–local method is established to ensure high efficiency in macro-scale and precision in meso-scale in analysis.Simulation results reveal that predictions of material properties show reasonable accuracy compared with test results. And the multi-scale method can analyze the strength of connections efficiently and accurately.

Topology Optimization Design and Strength Analysis of the Hoist Bracket for Rescue Helicopters

The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket's structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.

Design and Overall Strength Analysis of Multi-Functional Elastic Connections Floating Breakwater System

As a new type of marine structure,floating breakwater can provide suitable water area for coastal residents.In this paper,a multi-module floating breakwater with three cylinders was designed.According to the characteristics of each module,the elastic connector was created.The cabins with functions such as living,generating electricity and entertainment were arranged.A linear spring constrained design wave(LSCDW)method for strength analysis of floating marine structures with multi-module elastic connections was proposed.The numerical model was verified by 1:50 similarity ratio in the test tank.According to the analysis of design wave and extreme wave conditions,considering the mooring loads and environmental loads and connector loads,the overall strength of breakwater was analyzed by LSCDW method.These studies can provide new insights and theoretical guidance for the design of multi-module floating structures.

Application of dynamic analysis of strength reduction in the slope engineering under earthquake

At present,the methods of analyzing the stability of slope under earthquake are not accurate and reasonable because of some limitations. Based on the real dynamic tensile-shear failure mechanism of slope,the paper proposes dynamic analysis of strength reduction FEM (finite element method) and takes the reduction of shear strength parameters and tensile strength parameters into consideration. And it comprehensively takes the transfixion of the failure surface,the non-convergence of calculation and mutation of displacement as the criterion of dynamic instability and failure of the slope. The strength reduction factor under limit state is regarded as the dynamic safety factor of the slope under earthquake effect and its advantages are introduced. Finally,the method is applied in the seismic design of anchors supporting and anti-slide pile supporting of the slope. Calculation examples show that the application of dynamic analysis of strength reduction is feasible in the seismic design of slope engineering,which can consider dynamic interaction of supporting structure and rock-soil mass. Owing to its preciseness and great advantages,it is a new method in the seismic design of slope supporting.

Relationships between femoral strength evaluated by nonlinear finite element analysis and BMD,material distribution and geometric morphology

Precisely quantifying the strength of the proximal femur and accurately assessing hip fracture risk would enable those at high risk to be identified so that preventive interventions could be taken.Development of better measures of femoral strength using the clinically

用于抵抗扭转采取边缘弹性约束下的单轴压缩下板材极限强度:一种新的综合方法

The ultimate strength of platings under compression is one of the most important factors to be addressed in the ship design.Current Rules for ship structural design generally provide explicit strength check criteria against buckling for simply supported and clamped platings.Nevertheless,ship platings generally exhibit an intermediate behaviour between the simple support and the clamped conditions,which implies that the torsional stiffness of supporting members should be duly considered.Hence,the main aim of this study is the development of new design formulas for the ultimate strength of platings under uniaxial compression,with short and/or long edges elastically restrained against torsion.In this respect,two benchmark studies are performed.The former is devoted to the development of new equations for the elastic buckling coefficients of platings with edges elastically restrained against torsion,based on the results of the eigenvalue buckling analysis,performed by Ansys Mechanical APDL.The latter investigates the ultimate strength of platings with elastically restrained edges,by systematically varying the plate slenderness ratio and the torsional stiffness of supporting members.Finally,the effectiveness of the new formulation is checked against a wide number of finite element(FE)simulations,to cover the entire design space of ship platings.

STRESS ANALYSIS AND GEOMETRICAL CONFIGURATION SELECTION FOR MULTILAYER PIEZOELECTRIC DISPLACEMENT ACTUATOR

Multilayer piezoelectric ceramic displacement actuators are susceptible to cracking in the region near the edge of the internal electrode, which may cause system damage or failure. In this paper, the stress distribution of a multilayer piezoelectric composite is investigated in a working environment and the optimized geometrical con?guration of the piezoelectric layer is obtained. The stress distribution in the structure and the stress concentration near the edge of the internal electrode, induced by non-uniform electric ?eld distribution, are analyzed by moir′e interferometry experiment and ?nite element numerical simulation. Based on the above analysis, two optimized geometrical models are presented for the purpose of geometrical con?guration selection, with which stress concentration can be reduced signi?cantly while the feasibility of the machining process and the basic structural functions occurring in the conventional model are retained. The numerical results indicate that the maximum stress in the optimized models is e?ectively diminished compared to the conventional model. For instance, the peak value of the principal stress in the optimized model II is 93.1% smaller than that in the conventional model. It is proved that stress concentration can be e?ectively relaxed in the latter of the two optimized models and thus the probability of fracture damage can be decreased.

Design and Analysis of Typical Buoyancy Tank Riser Tensioner Systems

The method for design and analysis of a buoyancy tank riser tensioner system （BTRTS） was put forward in this paper, taking the free standing hybrid riser＇s top buoyancy tank as an example. The design procedure was discussed and was also illustrated in a flowchart, after a short description of the global arrangement, structure configuration, and the function of different types of buoyancy tanks （BT）. The objective of this paper is to describe a way of developing a BT with minimal hydro force, maximal net lift, and no redundancy of compartments. The method of determining the main dimensions of the BT, namely the length and the outer diameter, was outlined. A series of investigations was conducted for a West Africa FSHR BT design, and the effect of the ratio of the length to the outer diameter （L/D） on the hydrodynamics and the weight of the BT was discussed. The methodology of designing the internal structure of the BT was presented. The effects of the number of compartments and the dimension of the inner stem on the BT weight and strength were compared. The relationship between inner structure and the number one index of the BT as well as the riser＇s top tension factor （TTF） were illustrated for normal operating conditions and conditions with one or more compartments （or inner stem） damaged. A design instance was given in this paper, when L/D is 4-6, the BT weight and the drag force are compromised. When the BT is divided into 10 compartments, the riser TTF will reach the maximum value, and the ratio of the stem OD to shell OD is about 0.3. A global strength analysis method of the BT and the main load case matrix was also included in the paper, together with the local strength analysis of the buoyancy tank＇s pad-eye assembly.

Study on Welding-Bead Bonding Strength of Laser-Stacking Copper-Aluminum Heterogeneous Electrode Plates

In this paper,two types of copper-aluminum heterogeneous electrode plates are stacked and the finite element analysis(FEA)models of two different laser welding conditions are built by using SYSWELD welding simulation software to calculate the depth of the welding bead and the temperature distribution of the welding surface.Then,the residual stress analysis data of the welded area are exported and the residual stress is applied to the welded specimen for CAE analysis to ensure that the welding bonding strength meets the design target of a shear force of 500 N or higher.The copper-aluminum laser-stacking simulation technique in this paper can be applied to the manufacturing of copper-aluminum heterogeneous laser-welded electrodes and series-connected electrodes of automotive lithium-ion power battery modules,providing an effective analysis method for welding bonding-strength.

In situ synthesis and phase analysis of low density O'-sialon-based multiphase ceramics

In situ formed low density O＇-sialon-based multiphase ceramics were prepared by liquid-phase sintering method at 1400°C with Si3N4, SiO2 and Al2O3 as raw materials.Crystalline phases were identified by X-ray diffraction（XRD）.The quantitative phase analysis was finished by matrix-flushing method and the substitution parameter x value of O＇-sialon was estimated.The effects of sintering additives on the phase composition of the material were studied.The results show that, when using Y2O3 alone, Al6Si2O13 phase can be formed in the material, but when using Y2O3 and MgO, MgAl2O4 phase can be preferentially formed and the Al6Si2O13 is not observed.The mechanical properties of the material were measured and the relationships between microstructure and mechanical properties were discussed.The sample with Y2O3 and MgO sintering additives, using fused quartz alone as SiO2 source, displays a combination of high bending strength（163 MPa） and good fracture toughness（3.11 MPa·m1/2）.Bending strength and fracture toughness of the samples increase with the increase of the content and aspect ratio of elongated grains and decrease with the increase of the porosity.

Correlations between direct and indirect strength test methods

The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.

An Average Failure Index Method for the Tensile Strength Prediction of Composite Adhesive-bonded π Joints

An average failure index method based on accurate FEA was proposed for the tensile strength prediction of composite out-of-plane adhesive-bonded π joints. Based on the simple and independent maximum stress failure criterion, the failure index was introduced to characterize the degree of stress components close to their corresponding material strength. With a brief load transfer analysis, the weak fillers were prominent and further detailed discussion was performed. The maximum value among the average failure indices which were related with different stress components was filtrated to represent the failure strength of the critical surface, which is either the two curved upside surfaces or the bottom plane of the fillers for composite π joints. The tensile strength of three kinds of π joints with different material systems, configurations and lay-ups was predicted by the proposed method and corresponding experiments were conducted. Good agreements between the numerical and experimental results give evidence of the effectiveness of the proposed method. In contrast to the existed time-consuming strength prediction methods, the proposed method provides a capability of quickly assessing the failure of complex out-of-plane joints and is easy and convenient to be widely utilized in engineering.

浮式海上风力发电机的时域响应结构分析

As the turbine blade size becomes larger for economic power production,the coupling effect between wind turbine and floating substructure becomes important in structural assessment.Due to unsteady turbulent wind environment and corresponding coupled substructure response,time-domain analysis is required by international electrotechnical commission and class societies.Even though there are a few numerical tools available for the time domain structural analysis based on conventional coupled motion analysis with wind turbine,the application of conventional time domain analysis is impractical and inefficient for structural engineers and hull designers to perform structural strength and fatigue assessment for the required large number of design load cases since it takes huge simulation time and computational resources.Present paper introduces an efficient time-domain structural analysis practically applicable to buckling and ultimate strength assessment.Present method is based on‘lodal’response analysis and pseudo-spectral stress synthesizing technique,which makes timedomain structural analysis efficient and practical enough to be performed even in personal computing system.Practical buckling assessment methodology is also introduced applicable to the time-domain structural analyses.For application of present method,a 15-MW floating offshore wind turbine platform designed for Korean offshore wind farm projects is applied.Based on full-blown time domain structural analysis for governing design load cases,buckling and ultimate strength assessments are performed for the extreme design environments,and the class rule provided by Korean Register is checked.

Assessment of Aged Offshore Jacket Type Platforms Considering Environmental Loads and Degradation Parameters

Offshore steel structures are a common investment in oil and gas industries operating in shallow to medium depth seas.These structures have become increasingly popular since the mid-19th century,with a typical design life of 30-50 years.Despite their popularity,the structural integrity of existing offshore structures remains a controversial topic.Environmental loads and material degradation have been identified as significant factors that can compromise the structural integrity of offshore structures.To address this issue,this study aims to investigate the reserved strength capacity of a selected offshore structure located in the Malaysian Seas.The study will explore the effect of oceanographic data,variations in vertical load,and corrosion on the structure’s main members.To determine the impact of each variable on the reserved strength ratio(RSR)of the structure,several pushover analyses were conducted with different variables.Previous literature has shown little or no relationship between seawater wave height,gravity loads,and corrosion allowance on submerged steel members and the RSR of offshore structures.However,this study aims tofill this gap in knowledge by examining these variables’effects on the RSR of offshore structures.The study’sfindings indicate that even a slight increase in wave height can significantly impact the structure’s RSR due to the increase in lateral loading,potentially leading to severe damage to structural components and the foundation model.Additionally,gravity loads had an adverse effect on the RSR of the structure when more than double the vertical load was added.Corrosion allowance was also found to impact the RSR,particularly when assuming significant wall thickness corrosion in primary members.Overall,thefindings of this study have important implications for the design and maintenance of offshore structures.The results suggest that engineers and operators should pay close attention to the potential impacts of environmental loads,such as wave height and gravity loads,and material degradation,such as corrosion allowance,on the structural integrity of offshore structures.This information can be used to optimize the design and maintenance of offshore structures,leading to safer and more efficient operations.

Small ruminant value chain in Al-Ruwaished District,Jordan

This study aims to assess the small ruminant value chain in Al-Ruwaished District,Jordan,to identify the potential intervention areas that could improve the production efficiency and guarantee the sustainability of the small ruminant sector in this area.Sheep breeding is the source of livelihood for most of the people in Al-Ruwaished District,which is characterized by the large number of sheep and goats.We surveyed 5.0% of the small ruminant holders in the study area and conducted individual interviews and surveys with the potential actors in the value chain to undertake a small ruminant value chain analysis.From the survey,we found that the small ruminant value chain consists of five core functions,namely,input supply,production management,marketing,processing,and consumption.Despite the stable impression given by the large number of holdings in the small ruminant sector,the surveyed results show a clear fragility in the value chain of small ruminants in this area.The small ruminant production system is negatively impacted by climate change,especially continuous drought.In addition,the high prices of feed that the farmer cannot afford with clear and real absence of the governmental and non-governmental support activities also impact the development of the value chain.The results of strengths,weaknesses,opportunities,and threats(SWOT)analysis reveal that the major constraints faced by this value chain could be divided into external and internal threats.Specifically,the most prominent external threats are the nature of the desert land and continuous drought,while the major internal threats are the absence of appropriate infrastructure,shortage of inputs,and weakness in the production management and marketing.We proposed solutions to these challenges to ensure the sustainability and effectiveness of the sector,such as the formulation of emergency response plans to severe weather,qualifying farmers’skills,and establishment of agricultural cooperative societies.