Parametric Equation of Stress Concentration Factor for Circular X-Joints Under Axial Loads

In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.

Stress concentration factor expression for tension strip with eccentric elliptical hole

Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli＇s photo-elastic experiment and Isida＇s formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.

Effect of Surface Topography on Stress Concentration Factor

Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.

Spectrum-Splitting Diffractive Optical Element of High Concentration Factor and High Optical Efficiency for Three-Junction Photovoltaics

A spectrum-splitting and beam-concentrating （SSBC） diffractive optical element （DOE） for three-junction pho- tovoltaics （PV） system is designed and fabricated by five-circ/e micro-fabrication. The incident solar light is efficiently split into three sub-spectrum ranges and strongly concentrated on the focal plane, which can be di- rectly utilized by suitable spectrum-matching solar cells. The system concentration factor reaches 12x. Moreover, the designed wavelengths （450nm, 550nm and 65Onto） are spatially distributed on the focal plane, in good agree- ment with the theoretical results. The average optical effic/ency of all the cells over the three designed wavelengths is 60.07%. The SSBC DOE with a high concentration factor and a high optical efficiency provides a cost-effective approach to achieve higher PV conversion efficieneies.

Three-Dimensional Stress Concentration Factor in Finite Width Plates with a Circular Hole

The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickness, hole dimensions and material properties, such as the Poisson’s coefficient. This study employs three dimensional finite element modeling to numerically investigate the effect of plate width on the behavior of the SCF across the thickness of linear elastic isotropic plates with a through-the-thickness circular hole under remote tension. The problem is governed by two geometric non-dimensional parameters, i.e., the plate half-width to hole radius (W/r) and the plate thickness to hole radius (B/r) ratios. It is shown that for thin plates the value of the SCF is nearly constant throughout the thickness for any plate width. As the plate thickness increases, the point of maximum SCF shifts from the plate middle plane and approaches the free surface. When the ratio of plate half-width to hole radius (W/r) is greater than four, the maximum SCF was observed to approximate the theoretical value determined for infinite plates. When the plate width is reduced, the maximum SCF values significantly increase. A polynomial curve fitting was employed on the numerical results to generate empirical formulas for the maximum and surface SCFs as a function of W/r and B/r. These equations can be applied, with reasonable accuracy, to practical problems of structural strength and fatigue, for instance.

A review of stress concentration factors in tubular and non-tubular joints for design of offshore installations

Tubular structures are widely used in offshore installations,trusses,high rise buildings,towers for wind turbines,ski-lift installations,lightning,road pole signals etc.,owing to their excellent structural performance and attractive appearance.Stress concentration,especially in the welded joints of these structures,is an important design consideration particularly for fatigue design.In the context of tubular and non-tubular joints,this paper provides a review of the experimental and numerical studies that have been carried out so far to determine the stress concentration factor(SCF).Emphasis is also placed on the complexity of capturing different types of stresses in tubular/non-tubular joints for estimation of SCF.Present code provisions for evaluation of SCF are also discussed.Further,a few issues,which require significant research effort to advance our understanding and to improve the current design guidelines,have been identified.©2016 Shanghai Jiaotong University.Published by Elsevier B.V.

Influence of geometric parameters on stress concentration factors of undermatched butt joint with single V-groove under three-point bending load

In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.

Parametric equations for notch stress concentration factors of rib—deck welds under bending loading

The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the approach,the notch stress concentration factors for three typical fatigue-cracking modes(i.e.,root-toe,root-deck,and toe-deck cracking modes)were thoroughly investigated in this study.First,we developed a model for investigating the effective notch stress in rib-deck welds.Then,we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib-deck weld on the notch stress concentration factors.On this basis,the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors.Finally,we employed the proposed formulas in a case study.The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results.The results of the case study demonstrate the feasibility and reliability of the proposed formulas.It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib-deck welds.

Study Two-Dimensional and Three-Dimensional of the Stress Concentration of the Traction Arm of the NEW HOLLAND TT75 Tractor in Service in CHAD

The New Holland TT75 tractors currently in service in Chad use a tractor arm with three holes, the middle one of which has recurrent failures due to traction. The purpose of this work is to use a finite element model to provide an improvement by modifying the geometric parameters to avoid premature failure of the tractor arms of the New Holland TT75. The ultimate force formula of Eurocode 3 was used to determine the maximum pressure to be applied and. A comparative traction study between the current arm and the proposed arm was performed, taking into account the variation in hole size, arm width and applied pressure for the determination of the stress concentration factor Kt. With the determination of Kt and for the arm width (w) less than or equal to 85 mm;the results showed that the proposed arm geometry is better.

STUDY ON STRESS CONCENTRATIONS IN AN INTRAPLY HYBRID COMPOSITE SHEET

A reasonably, simply and accurately modified shear-lag model was proposed. Based on the model, the stress redistributions due to the failure of some fibers in an intraply hybrid composite under tension were analyzed. The results show that the present calculating stress concentration factors very coincide with Fukuda and Chou's results, thus verifying the reasonableness and correctness of the present model and methods.

Autologous peripheral blood-derived orthobiologics:Different types and their effectiveness in managing knee osteoarthritis

Knees are the most commonly impacted weight-bearing joints in osteoarthritis(OA),affecting millions of people worldwide.With increasing life spans and obesity rates,the incidence of knee OA will further increase,leading to a significant increase in the economic burden.Conventional treatment modalities utilized to manage knee OA have limitations.Over the last decade,the role of various autologous peripheral blood-derived orthobiologics(APBOs)for the treatment of knee OA has been extensively investigated.This editorial provided an overview and focused on defining and shedding light on the current state of evidence based on the most recent published clinical studies concerning the use of APBO for the management of knee OA.While numerous studies have demonstrated promising results for these preparations,a notable gap exists in the comparative analysis of these diverse formulations.This absence of head-to-head studies poses a considerable challenge for physicians/surgeons in determining the optimal preparation for managing knee OA and achieving sustained longterm results.Thus,more adequately powered,multicenter,prospective,doubleblind,randomized controlled trials with longer follow-ups are needed to establish the long-term efficacy and to aid physicians/surgeons in determining the optimal APBO for the management of knee OA.

Dynamic stress concentration of an elliptical cavity in a semi-elliptical hill under SH-waves

The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration factor(DSCF)around an elliptical cavity in a shallow,semi-elliptical hill.An infinite system of simultaneous linear equations for solving this problem was established by substituting the wave expression obtained by the Mathieu function including the standing wave expression of elliptical lining given herein into the boundary condition obtained by the region-matching method.The finite equations system with unknown coefficients obtained by truncation were solved numerically,and the results in the case of an ellipse degenerating into a circle were compared with previous results to verify the accuracy of the method.The effects of different aspect ratios,incident wave angles and aperture ratios on the dynamic stress concentration around the elliptical cavity were described.Some numerical results,when the elliptical hill was changed into a circular one,were analyzed and compared in detail.In engineering,this model can be regarded as a semi-cylindrical hill with an elliptical cylindrical unlined tunnel under the action of SH waves,and the results are significant in aseismic design.

Development of the ^(137)Cs,^(90)Sr and ^(3)H Concentrations in the Hydrosphere in the Vicinity of NPP Temelín(South Bohemia)

The paperfocuses on an analysis of the results of long-term monitoring of the concentrations of 137Cs, 90Sr and 3H in hydrosphere in the vicinity of Temelín Nuclear Power Plant (Temelín plant). The radionuclides were monitored in surface water, river sediments, aquatic flora and fish species. The main objective of the study was to analyze and integrate all of the knowledge on concentrations and behaviour of these radionuclides, which originate mainly from residual contamination, in order to assess the impacts of Temelín Nuclear Power Plant on hydrosphere in these indicators during its standard operation and possible accidents. The radionuclides were analyzed in terms of spatial and temporal variability in their concentrations and their inflows and outflows, mainly into and from Orlík Reservoir. The analysis included standard radioecological characteristics, which were applicable for assessing long-term development and behavior of radionuclides in the environment affected by their possible accidental releases on the territory of the Czech Republic or outside this territory. For all of the components of the environment, the concentrations of 137Cs and 90Sr which were used for calculation of their effective and ecological half-time, were decreasing. For 137Cs in surface water and fish, the rates of the decrease in the first and second monitoring period were different. The rate of the decrease in 90Sr concentration was invariable. The results of the monitoring showed that 86% of suspended solids and 62% of 137Cs inflowing into Orlík Reservoir accumulated in the reservoir while accumulation of 90Sr was not substantiated. Outflows of 137Cs and 90Sr activities were assessed in relation to their concentrations that were accumulated in individual basins until 1986 consequently to Chernobyl accident and tests of atmospheric nuclear weapons. The results for the whole area of the Vltava, Luznice and Otava River basins upstream from the Vltava River at Solenice showed that during the period 1986-2013 only 0.49% of 137Cs activity and 3.6% of 90Sr activity that accumulated in the basins were washed and flowed out from the area. Distribution coefficients derived from summary analysis of sediments and concentration factors for biota were calculated. Concentrations of 3H in river sites not affected by Temelín plant were slowly decreasing and their values were substantially below those from the sites affected by the plant.

Therapeutic effect of autologous concentrated growth factor on lower-extremity chronic refractory wounds:A case report

BACKGROUND Management of chronic refractory wounds is one of the toughest clinical challenges for surgeons.Because of poor blood supply,less tissue coverage,and easy exposure,the lower leg is a common site for chronic refractory wounds.The current therapeutic regimens often lead to prolonged hospital stay and higher healthcare costs.Concentrated growth factor(CGF)is a novel blood extract that contains various growth factors,platelets,and fibrins to promote wound healing process.However,there has been little research reported on the treatment of lower extremity wounds with CGF.CASE SUMMARY A 37-year-old man,without any past medical history,presented an ulcerated chronic wound on his right lower leg.The skin defect exhibited clear boundaries,with a size of 2.0 cm×3.5 cm.The depth of wound was up to the layer of deep fascia.Staphylococcus aureus was detected by bacterial culture.The final diagnosis was right lower extremity ulcers with infection.Cefathiamidine,silver sulfadiazine,and mupirocin cream were applied to control the infection.CGF gel was prepared from the patient’s blood sample,and was used to cover the wound after thorough debridement.The skin wound was successfully healed after three times of CGF treatment.CONCLUSION CGF displays an excellent wound healing promoting effect in patients with lowerextremity chronic refractory wounds.

Observation on the Clinical Effect of Breast Augmentation by Transplanting Concentrated Growth Factor and Autologous Fat

Objective To explore the effect of concentrated growth factor(CGF)combined with autologous fat transplantation in augmentation mammoplasty.Methods Clinical data of 28 female patients who underwent autologous fat by CGF mixed with purified fat between May 2015 and June 2018 were retrospectively analyzed.Clinical evaluation was performed to observe and measure the shape of the breast after breast augmentation,the increase in the value of the nipple plane measurement,and complications.Results All of 28 patients,after 12 months of follow-up,all patients no fat infection,hematoma,breast nodules and other complications.It showed that the contouring of breast were improved and more chubbiness than that before operation.The results were satisfied from patients.Conclusion Concentrated growth factor combined with autologous fat transplantation has a stable breast augmentation effect,beautiful breast shape,simple operation and small damage,which achieves breast rejuvenation.

In situ strengths of matrix in a composite

A major obstacle to achieving reasonable strength prediction of a composite only from its constituent information is in the determination of in situ strengths of the matrix. One can measure only the original strengths of the pure matrix, on the basis of which the predicted transverse strengths of a unidirectional (UD) composite are far from reality. It is impossible to reliably measure matrix in situ strengths. This paper focuses on the correlation between in situ and original strengths. Stress concentrations in a matrix owing to the introduction of fibers are attributed to the strength variation. Once stress concentration factors (SCFs) are obtained, the matrix in situ strengths are assigned as the original counterparts divided by them. Such an SCF cannot be defined following a classical approach. All of the relevant issues associated with determining it are systematically addressed in this paper. Analytical expressions for SCFs under transverse tension, transverse compression, and transverse shear are derived. Closed-form and compact formulas for all of the uniaxial strengths of a UD composite are first presented in this paper. Their application to strength predictions of a number of typical UD composites demonstrates the correctness of these formulas.

REE characteristics of the coal in the Erlian Basin, Inner Mongolia, China, and its economic value

The rare earth elements(REE)content of the coal in the Erlian Basin was determined by inductively coupled plasma mass spectrometry(ICP-MS),and it turns out that the REE content from different geological age shows a significant difference:The REE content of the coal in the Jurassic Alatanheli Group is from 152.05×10^(−6) to 1416.21×10^(−6),with an average value of 397.31×10^(−6),and the relative concentration factor shows enriched;the REE content of the coal in Early Cretaceous Baiyanhua Group is from 20.65×10^(−6) to 102.53×10^(−6),the mean value is 49.06×10^(−6),and the relative concentration factor shows normally.The REE distribution patterns samples in Jurassic and Cretaceous shows the difference:The REE pattern in Jurassic coal mainly manifests as H-type distribution,with the Y,Lu positive anomaly,it is speculated that the fluid carried REE ions into the coal-bearing basin,and the heavy REE gather in the coal due to the different chemical properties of each REE.The REE occurrence mode is presumed to be mainly organic.Flat type is the REE main distribution pattern in Cretaceous coal.The REE patterns in clastic rocks of the roof,parting and floor of coal seam are similar to the REE patterns in the coal and the most possible reason is that the REE main source is from the clastic rock.It showed that the coal of the Early Jurassic,especially of Amugulen coalfield has resource value.

Scattering of shear waves by an elliptical cavity in a radially inhomogeneous isotropic medium

Complex function and general conformal mapping methods are used to investigate the scattering of elastic shear waves by an elliptical cylindrical cavity in a radially inhomogeneous medium. The conformal mappings are introduced to solve scattering by an arbitrary cavity for the Helmholtz equation with variable coefficient through the transformed standard Helmholtz equation with a circular cavity. The medium density depends on the distance from the origin with a power-law variation and the shear elastic modulus is constant. The complex-value displacements and stresses of the in.homogeneous medium are explicitly obtained and the distributions of the dynamic stress for the case of an elliptical cavity are discussed. The accuracy of the present approach is verified by comparing the present solution results with the available published data. Numerical results demonstrate that the wave number, inhomogeneous parameters and different values of aspect ratio have significant influence on the dynamic stress concentration factors around the elliptical cavity.

轴向载荷作用下管状TY接头几何参数对应力集中系数的影响分析

In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads.Thus,the highest stress concentration factor values are observed on the vertical brace than on the inclined one.The finite element results of the tubular structures were verified by parametric equations and experimental data.A parametric study was carried out by analyses using the nonlinear regression method to obtain parametric equations.These equations are used to calculate stress concentration factors and to analyse the fatigue resistance of TY-joints due to axial loads.