Effects of gradient on stress distribution in rotating functionally graded solid disks

Xu-Long Peng,Xian-Fang Li 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.5

"This paper presents the elastic analysis of a rotating sandwich solid disk composed of three-layered perfectly-bonded composites. The center and outer regions of the solid disk are two homogeneous isotropic media, and the middle region is a transition zone made of functionally graded materials (FGM). Two cases are considered. One is on FGM with power-law gradient. For this case, explicit expressions for full elastic fields are derived. The other is on FGM with any radial nonhomogeneity, for which an analytic approach is proposed to reduce the problem into a Fredholm integral equation. The validity of the latter method is ensured by comparing numerical results of the elastic fields with the exact ones for the case of power-law gradient. For a general case, the current study presents the influences of the gradient, width variation of the FGM, and rotational velocity on the distribution of the radial and hoop stresses for a rotating composite disk made of aluminum and zirconia. The method presented in this paper may help engineering designers in choosing appropriate gradients and materials to acquire the optimal state of a rotating functionally graded disk."

Correlation between Severity of Synovitis and Clinical Features in Rotator Cuff Tears

Doohyung Lee,Kwang-Hyun Lee,Jo Young-Hoon,Il-Han Joo,Hee Jae Lee,Soo-Young Jeong,Bong Gun Lee 대한정형외과학회 2021 Clinics in Orthopedic Surgery Vol.13 No.1

Background: Rotator cuff tears can be asymptomatic in some cases; however, even when the tear size is small, clinical symptoms can be very severe. This suggests that symptoms of rotator cuff tears are related to factors other than the size. Although synovitis has been cited as one of the factors, there is no grading system for synovitis in rotator cuff tears. Moreover, there are few studies that evaluated the relationship between synovitis and clinical features in patients with rotator cuff tears. Methods: Patients with medium-sized rotator cuff tears, who were scheduled for arthroscopic repair, were recruited for this study. The glenohumeral joint was divided into 4 quarters. Then, vascularity and hypertrophy of the joint were graded in each quarter using a modified scoring system. Clinical assessment was performed preoperatively and at 3 months and 6 months after surgery. Finally, correlation between the severity of synovitis and clinical features was analyzed. Results: The intraobserver correlation coefficient was 0.815 to 0.918 and the interobserver correlation coefficient was 0.779 to 0.992 for the single measurement. Vascularity was significantly correlated with the range of motion, strength, and constant score within 6 months after surgery. Hypertrophy was correlated with the range of motion within 6 months after surgery. Conclusions: Synovitis in the shoulder with rotator cuff tears can be graded by using our modified scoring system. The severity of synovitis was closely related to the clinical features after surgery. Therefore, when treating patients with rotator cuff tears, treatment of synovitis should also be considered.

Finite element based stress and vibration analysis of axially functionally graded rotating beams

Khalid H. Almitani,M.A. Eltaher,Alaa. A. Abdelrahman,Hanaa E. Abd-El-Mottaleb 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.1

This study presents a comprehensive numerical dynamic finite element analysis to investigate the dynamic behavior and induced stresses of axially functionally graded rotating beam, for the first time. The material properties of the rotating beam are assumed to continuously vary nonlinearly along the longitudinal direction according to the power law. Based on Timoshenko beam theory (TBT), the Hamiltonian principle is applied to derive governing equations of motion. The dynamic finite element equation of motion for axially functionally straight rotating cantilever beam is derived. Both stress and vibration responses are detected and analyzed. The proposed computational procedure is verified by comparing the obtained results with the corresponding results in the literature and good agreement is observed. Effects of the material gradation index and the rotating speed on the dynamic behavior of functionally graded rotating cantilever are investigated and analyzed. The obtained results show the significant effect of the material gradation index and the rotating speed on the dynamic behavior of axially functionally graded beams. The proposed model can be used effectively in design of wind turbine, rotation shafts and turbomachinery systems.

Influence of porosity and axial preload on vibration behavior of rotating FG nanobeam

Ehyaei, Javad,Akbarshahi, Amir,Shafiei, Navvab Techno-Press 2017 Advances in nano research Vol.5 No.2

In this paper, a nanobeam connected to a rotating molecular hub is considered. The vibration behavior of rotating functionally graded nanobeam based on Eringen's nonlocal theory and Euler-Bernoulli beam model is investigated. Furthermore, axial preload and porosity effect is studied. It is supposed that the material attributes of the functionally graded porous nanobeam, varies continuously in the thickness direction according to the power law model considering the even distribution of porosities. Porosity at the nanoscopic length scale can affect on the rotating functionally graded nanobeams dynamics. The equations of motion and the associated boundary conditions are derived through the Hamilton's principle and generalized differential quadrature method (GDQM) is utilized to solve the equations. In this paper, the influences of some parameters such as functionally graded power (FG-index), porosity parameter, axial preload, nonlocal parameter and angular velocity on natural frequencies of rotating nanobeams with pure ceramic, pure metal and functionally graded materials are examined and some comparisons about the influence of various parameters on the natural frequencies corresponding to the simply-simply, simplyclamped, clamped-clamped boundary conditions are carried out.

A Four-Variable First-Order Shear Deformation Theory Considering the Variation of In-plane Rotation of Functionally Graded Plates

박민우,최동호 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4

This paper presents a four-variable fi rst-order shear deformation theory considering in-plane rotation of functionally graded plates. In recent studies, a simple fi rst-order shear deformation theory was developed and extended to functionally graded plates. It has only four variables, separating the defl ection into bending and shear parts, while the conventional fi rst-order shear deformation theory has fi ve variables. However, this simple fi rst-order shear deformation theory only provides good predictions for simply supported plates since it does not consider in-plane rotation varying through the thickness of the plates. The present theory also has four variables, but considers the variation of in-plane rotation such that it is able to correctly predict the responses of the plates with any boundary conditions. Analytical solutions are obtained for rectangular plates with various boundary conditions. Comparative studies demonstrate the eff ects of in-plane rotation and the accuracy of the present theory in predicting the responses of functionally graded plates.

Thermo-elastic analysis of rotating functionally graded micro-discs incorporating surface and nonlocal effects

Ebrahimi, Farzad,Heidar, Ebrahim Techno-Press 2018 Advances in aircraft and spacecraft science Vol.5 No.3

This research studies thermo-elastic behavior of rotating micro discs that are employed in various micro devices such as micro gas turbines. It is assumed that material is functionally graded with a variable profile thickness, density, shear modulus and thermal expansion in terms of radius of micro disc and as a power law function. Boundary condition is considered fixed-free with uniform thermal loading and elastic field is symmetric. Using incompressible material's constitutive equation, we extract governing differential equation of four orders; to solution this equation, we utilize general differential quadrature (GDQ) method and the results are schematically pictured. The obtained result in a particular case is compared with another work and coincidence of results is shown. We will find out that surface effect tends to split micro disc's area to compressive and tensile while nonlocal parameter tries to converge different behaviors with each other; this convergence feature make FGIMs capable to resist in high temperature and so in terms of thermo-elastic behavior we can suggest, using FGIMs in micro devices such as micro turbines (under glass transition temperature).

요추 회전도와 측만각 및 전만각과의 상관관계의 관한 고찰

한무규 ( Moo Gyu Han ),허수영 ( Su Young Heo ) 대한한의학회 한방재활의학과학회 2001 한방재활의학과학회지 Vol.11 No.1

직무 순환이 동기 부여 및 직무 만족에 미치는 영향에 관한 연구

권나경(Na Kyung Kwon),김혜린(Hye Lin Kim),서원석(Won Seok Seo) 한국조리학회 2010 한국조리학회지 Vol.16 No.4

The purpose of this study is to find out the effect of job rotation on employees` motivation and satisfaction. That is, it is the ultimate aim to know why employees want job rotation or why not, whether the rotation has an effect on their motivation, and finally whether the motivation gives direct job satisfaction. As a result of the survey, the efficiency and procedure of job rotation have influence on motivation. The employees also think that regular rotation can help them to find the proper position to meet their aptitude. And motivation also affects employees` achievement, benefits, and relationship with their bosses. Especially, when they feel great achievement and pride in their jobs, their satisfaction appeared to be very high. And when they are paid properly in comparison with their workload, or they learn special knowledge from their bosses, they usually content themselves.

Elastic wave dispersion modelling within rotating functionally graded nanobeams in thermal environment

Ebrahimi, Farzad,Haghi, Parisa Techno-Press 2018 Advances in nano research Vol.6 No.3

In the present research, wave propagation characteristics of a rotating FG nanobeam undergoing rotation is studied based on nonlocal strain gradient theory. Material properties of nanobeam are assumed to change gradually across the thickness of nanobeam according to Mori-Tanaka distribution model. The governing partial differential equations are derived for the rotating FG nanobeam by applying the Hamilton's principle in the framework of Euler-Bernoulli beam model. An analytical solution is applied to obtain wave frequencies, phase velocities and escape frequencies. It is observed that wave dispersion characteristics of rotating FG nanobeams are extremely influenced by angular velocity, wave number, nonlocal parameter, length scale parameter, temperature change and material graduation.

Effect of material inhomogeneity on the rotating functionally of a graded orthotropic hollow cylinder

H. M. Wang 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.9

The effect of the material inhomogeneity on the stress field of a rotating orthotropic infinite hollow cylinder made of functionally graded materials is investigated. The original functionally graded hollow cylinder is approximated by the laminate model, of which the solution will gradually approach the exact one with the increase in number of fictitious layers. The analysis is performed by means of the state space method. The validity of the solution is verified by utilizing the exact solution of a special non-homogeneous rotating hollow cylinder and earlier results. The distributions of the radial and tangential stresses of the internally pressurized rotating functionally graded hollow cylinder for various material inhomogeneity parameters are depicted graphically. The degree of the orthotropy on the stress fields is also discussed.