Loading...
Search for:
shearing-force
0.005 seconds
Effect of Lumbar Spine Lordosis on Intervertebral Joint Load Sharing Using Musculoskeletal and Finite Element Modeling
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
There is a large, at times contradictory body of investigations relating low back pain and spinal curvature in sagittal plane. The previous studies have not been subject-specified, and they have not considered the active tissues in the models. The mechanical load has a significant impact on the prevalence of low back pain and the geometry of lumbar spine in the sagittal plane is one of the most important characteristics in determining the load sharing of the spine. Thus, it is essential to know how the geometry load affects the load sharing of the lumbar spine. As a matter of fact, the purpose of this project is to know how the geometry of the lumbar spine affects the load sharing. Thus,...
Mechanical properties of graphene cantilever from atomic force microscopy and density functional theory
, Article Nanotechnology ; Volume 21, Issue 18, Article number 185503 , 2010 ; 09574484 ; Iraji Zad, A. (Azam) ; Ahadian, M. M ; Sharif University of Technology
Abstract
We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been derived from the AFM data. Force displacement curves using the Derjaguin–Müller–Toporov (DMT) and the massless cantilever beam models yield a Young modulus of Ec ~ 37, Ea ~ 0.7 TPa and a Hamakar constant of ~ 3 × 10 − 18 J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated...
On the resolution of existing discontinuities in the dynamic responses of an Euler-Bernoulli beam subjected to the moving mass
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Saeedi, K ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
The dynamic response of a one-dimensional distributed parameter system subjected to a moving mass with constant speed is investigated. An Euler-Bernoulli beam with the uniform cross-section and finite length with specified boundary support conditions is assumed. In this paper, rather a new method based on the time dependent series expansion for calculating the bending moment and the shear force due to motion of the mass is suggested. Governing differential equations of the motion are derived and solved. The accuracy of the numerical results primarily is verified and further the rapid convergence of this new technique was illustrated over other existing methods. Finally, it is shown that a...
Evaluation of 1991 NIOSH Lifting Equation in Controlling the Biomechanical Loads of the Human Spine
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
The 1991 NIOSH Lifting Equation (NLE) is widely used to assess risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses two biomechanical models of the spine to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies).Severallifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the models. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding the recommended limits. The NIOSH vertical multiplier is the likely...
A Study on the Effect of Different Lubrication Methods on Surface Integrity and Tool Wear during Ultrasonic-Assisted Milling of CFRP
, M.Sc. Thesis Sharif University of Technology ; Akbari, Javad (Supervisor)
Abstract
The aim of this study was to compare the effect of different cooling conditions (dry, flood, mql) on machined surface parameters (smoothness and protrusion of fibers) and tool erosion in carbon fiber reinforced plastic composite materials (CFRP) in the presence of ultrasonic vibrations or without it. Is. Today, carbon fiber reinforced plastic composite materials or CFRP have become one of the most widely used materials in industry due to their strength and light properties. For example, these materials have been used in the manufacture of products from commercial aircraft to shoes, tennis rackets, golf clubs, fishing rods, etc. The combination of carbon fibers woven with resin in alternating...
The seismic performance of new detailing for RCS connections
, Article Journal of Constructional Steel Research ; Volume 91 , 2013 , Pages 76-88 ; 0143974X (ISSN) ; Attari, N. K. A ; Kazemi, M. T ; Sharif University of Technology
2013
Abstract
Over the past few decades considerable experimental and numerical studies have been conducted on the Reinforced Concrete columns to Steel beams (RCS) connections. Most of those researches have focused on studying the joint failure modes and ultimate joint strength of specimens utilizing strong beams and columns with weak joints. In this paper, two interior RCS connections were designed based on the Strong Column-Weak Beam (SCWB) criterion. Both specimens were tested under quasi-static reversed cyclic loading. The tested specimens were modeled by a finite element method, which verified with experimental results. Several models with different joint details were investigated using the verified...
Characterization of line nanopatterns on positive photoresist produced by scanning near-field optical microscope
, Article Journal of Nanomaterials ; Volume 2015 , September , 2015 ; 16874110 (ISSN) ; Yasrebi, N ; Rashidian, B ; Sharif University of Technology
Hindawi Publishing Corporation
2015
Abstract
Line nanopatterns are produced on the positive photoresist by scanning near-field optical microscope (SNOM). A laser diode with a wavelength of 450 nm and a power of 250 mW as the light source and an aluminum coated nanoprobe with a 70 nm aperture at the tip apex have been employed. A neutral density filter has been used to control the exposure power of the photoresist. It is found that the changes induced by light in the photoresist can be detected by in situ shear force microscopy (ShFM), before the development of the photoresist. Scanning electron microscope (SEM) images of the developed photoresist have been used to optimize the scanning speed and the power required for exposure, in...
Evaluation of the vertical distribution of base shear force in base-isolated structures
, Article Scientia Iranica ; Volume 14, Issue 1 , 2007 , Pages 11-22 ; 10263098 (ISSN) ; Ebrahimi, M ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
Application of the base-isolation systems, as a means to limit the seismic-induced response of structures, has attracted the attention of many engineers and researchers. Due to their importance, the Uniform Building Code (UBC) has incorporated a special section for the seismic analysis and design of base-isolated structures since its 1991 edition. The present work investigates the vertical distribution of the lateral seismic force for base-isolated structures provided by the 1997 edition of UBC (UBC97). Different 6 and 8-story, 3-D base-isolated structural models with LRB isolators are considered, having a variety of effective periods and effective damping ratios. The UBC97 analysis...
Biomechanical Evaluation of the Niosh Equation in Stoop Versus Squat Load-Handling Activities Using a Full-Body Musculoskeletal Model
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
Objective: To assess adequacy of the National Institute for Occupational Safety and Health (NIOSH) Lifting Equation (NLE) in controlling lumbar spine loads below their recommended action limits during load-handling activities in the stoop and squat using a detailed musculoskeletal model,that is, the AnyBody Modeling System.Background: The NIOSH committee employed simplistic biomechanical models for the calculation of the spine compressive loads with no estimates of the shear loads. In addition, NLE does not include the posture of the knee during manual material handling. It is therefore unknown whether the NLE would adequately control lumbar compression and shear loads below their...
Novel type of four-impinging-jets reactor for Oxidative desulfurization of light fuel oils
, Article Industrial and Engineering Chemistry Research ; Volume 49, Issue 19 , 2010 , Pages 9339-9348 ; 08885885 (ISSN) ; Molaei Dehkordi, A ; Shahrokhi, M ; Ebrahimi, A. A ; Sharif University of Technology
Abstract
A novel type of four-impinging-jets reactor (FIJR) has been proposed and tested successfully for the oxidative desulfurization of kerosene as a typical light fuel oil. The FIJR is characterized by a high-intensity mixing chamber located at the bottom of the reactor and equipped with four impinging jets. The influences of various operating and design parameters such as feed flow rate, internozzle distance, jet diameter, and jet Reynolds number on the performance of the FIJR have been carefully investigated. As a result of both the impinging process and shear forces exerted on the phases, the rate of desulfurization in FIJR increased significantly compared to that obtained by a conventional...
Mechanical properties of graphene cantilever from atomic force microscopy and density functional theory
, Article Nanotechnology ; Volume 21, Issue 18 , 2010 ; 09574484 (ISSN) ; Iraji Zad, A ; Ahadian, M. M ; Sharif University of Technology
2010
Abstract
We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been derived from the AFM data. Force displacement curves using the Derjaguin-Müller-Toporov (DMT) and the massless cantilever beam models yield a Young modulus of Ec ∼ 37, Ea ∼ 0.7TPa and a Hamakar constant of ∼ 3 × 10 -18J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated from...
Effect of damped outriggers arrangement on the seismic response of high-rise steel structures
, Article Scientia Iranica ; Volume 27, Issue 3 A , 2020 , Pages 1075-1090 ; Mofid, M ; Sharif University of Technology
Sharif University of Technology
2020
Abstract
Recently, a novel structural system, which is defined as a damped outrigger system, has been proposed to control the dynamic vibration of tall buildings. This paper examines the seismic performance of tall buildings involving multiple outriggers equipped with viscous dampers. In this respect, a dual structural system (braced moment frame) is selected as a bare structure. In addition, the number and position of outriggers are assumed to be variable along the structure height. Nonlinear Response History Analysis (RHA) is performed to evaluate the efficiency of the damped-outrigger system under eight-scaled ground motions. The results are presented based on the average of all ground motions....
A novel double slip loads friction damper to control the seismic response of structures
, Article Engineering Structures ; Volume 225 , 2020 ; Rofooei, F. R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, the performance of a proposed friction damper with two slip loads in controlling the seismic response of steel moment resisting buildings structures under moderate and intense earthquake excitations is investigated. The proposed friction damper initially operates with a smaller slip load and could shift to the higher slip load after a certain amount of slippage when subjected to intense ground motions. In this regard, the hysteresis behavior of the proposed double slip loads (DSL) friction damper is modeled and after necessary verifications is imported to the material library of OpenSees software to be used for parametric study. To evaluate the performance of the proposed DSL...
Shear-flexural interaction in analysis of Reduced web section beams using VM link element
, Article International Journal of Engineering, Transactions B: Applications ; Volume 20, Issue 1 , 2007 , Pages 23-35 ; 1728-144X (ISSN) ; Kazemi, M. T ; Sharif University of Technology
Materials and Energy Research Center
2007
Abstract
Reduced web section beams in shear-yielding moment-resistant steel frames are used for energy dissipating of earthquakes. The finite element analysis indicates that failure mode of these beams are governed by the combination of shear force and flexural moment. Therefore the analysis of frames with reduced web section beams needs consideration of shear-flexural interaction in those sections. In the present paper, modeling and analysis of reduced web section beams are investigated by using a special element which is called VM link element. The elastic and inelastic shear and flexural deformations and tangential stiffnesses in this link element are considered by using the multi- surfaces...
Predictive equations to estimate spinal loads in symmetric lifting tasks
, Article Journal of Biomechanics ; Volume 44, Issue 1 , Jan , 2011 , Pages 84-91 ; 00219290 (ISSN) ; Plamondon, A ; Shirazi Adl, A ; Larivière, C ; Parnianpour, M ; Sharif University of Technology
2011
Abstract
Response surface methodology is used to establish robust and user-friendly predictive equations that relate responses of a complex detailed trunk finite element biomechanical model to its input variables during sagittal symmetric static lifting activities. Four input variables (thorax flexion angle, lumbar/pelvis ratio, load magnitude, and load position) and four model responses (L4-L5 and L5-S1 disc compression and anterior-posterior shear forces) are considered. Full factorial design of experiments accounting for all combinations of input levels is employed. Quadratic predictive equations for the spinal loads at the L4-S1 disc mid-heights are obtained by regression analysis with adequate...