scholarly journals Effects of Geometrical Clearances, Supports Friction, and Wear Rings on Hydraulic Actuators Bending Behavior

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Sergio Baragetti ◽  
Francesco Villa
Keyword(s):  
Experimental Data ◽  
Critical Load ◽  
Friction And Wear ◽  
Industrial Revolution ◽  
Mathematical Formulation ◽  
Buckling Load ◽  
Hydraulic Actuators ◽  
Optimum Position ◽  
Bending Stresses ◽  
Bending Behavior

Hydraulic actuators are commonly adopted in machines and structures to provide translating forces with significant magnitudes. Although their application dates back to the industrial revolution, their bending behavior under compression is typically addressed by simple Euler’s instability analysis on the rod, neglecting effects such as the cylinder inertia and stiffness, the presence of contact elements in the cylinder-rod junction and on the piston, geometrical misalignments and imperfections, and friction moments at the support. Such simplifications lead to unjustified reduced critical load calculations on the component. In the present paper, a complete mathematical formulation, which accounts for such effects, is presented and validated against experimental data. A numerical sensitivity analysis is conducted, to assess the contributions of initial rectilinear imperfections, wear rings stiffness and dimension, and supports friction on the actuator’s limit buckling load and bending behavior under compression. Results are presented, including the effect of the cited parameters on the buckling load, providing a reliable tool for the mechanical designer. In particular, an optimum position for the wear ring distance is found. Moreover, increased wear ring stiffness and reduced imperfections increase the buckling load and reduce the bending stresses before the critical load.

Tribological properties of beef tallow as lubricating grease

2017 ◽  
Vol 69 (5) ◽  
pp. 645-654 ◽  
Author(s):  
Juozas Padgurskas ◽  
Raimundas Rukuiža ◽  
Ihor Mandziuk ◽  
Arturas Kupcinskas ◽  
Katerina Prisyazhna ◽  
...  
Keyword(s):  
Critical Load ◽  
Tribological Properties ◽  
Beef Tallow ◽  
Friction And Wear ◽  
Load Level ◽  
Synthesis Process ◽  
Polymer Additives ◽  
Lubricating Grease ◽  
Content Type ◽  
Thermally Processed

Purpose The purpose of this paper is to report on the tribological properties of beef tallow grease and improvements therein through modification with special processing, polymeric compounds and additives. Design/methodology/approach Pure original beef tallow grease was used as a biological lubricating grease reference material for the tribological research. Beef tallow was modified and synthesized by adding special biological anti-oxidant additives, LZ anti-wear additives, waste polyethylene terephthalate (PET) polymer compounds and thermally processed graphite. Findings Rheometric measurements indicate that the beef tallow grease modification technology used in this study enables control of the synthesis process to produce lubricants with the required microstructure. Investigation results of the tribological properties of differently modified greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The grease compound with thermally processed graphite has good tribological properties at 300 N load levels. The critical load level of lubricating greases could be significantly increased through the use of anti-wear additives and thermally processed graphite. Originality/value Investigation results of the tribological properties of differently modified beef tallow greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The critical load level of lubricating beef tallow greases could be significantly increased using anti-wear additives and thermally processed graphite.

Evolution of hindlimb posture in nonmammalian therapsids: biomechanical tests of paleontological hypotheses

Paleobiology ◽  
2001 ◽  
Vol 27 (1) ◽  
pp. 14-38 ◽  
Author(s):  
Richard W. Blob
Keyword(s):  
Experimental Data ◽  
Biomechanical Model ◽  
Axial Rotation ◽  
Morphological Data ◽  
Upright Posture ◽  
Cross Sectional ◽  
Model Calculations ◽  
Limb Bones ◽  
Plausible Model ◽  
Bending Stresses

Analyses of limb joint morphology in nonmammalian therapsid “mammal-like reptiles” have suggested that among many lineages, individual animals were capable of shifting between sprawling and upright hindlimb postures, much like modern crocodilians. The ability to use multiple limb postures thus might have been ancestral to the generally more upright posture that evolved during the transition from “mammal-like reptiles” to mammals. Here I derive a biomechanical model to test this hypothesis through calculations of expected posture-related changes in femoral stress for therapsid taxa using different limb postures. The model incorporates morphological data from fossil specimens and experimental data from force platform experiments on iguanas and alligators.Experimental data suggest that the evolutionary transition from sprawling to nonsprawling posture was accompanied by a change in the predominant loading regime of the limb bones, from torsion to bending. Changes in the cross-sectional morphology of the hindlimb bones between sphenacodontid “pelycosaurs” and gorgonopsid therapsids are consistent with the hypothesis that bending loads increased in importance early in therapsid evolution; thus, bending stresses are an appropriate model for the maximal loads experienced by the limb bones of theriodont therapsids. Results from the model used to estimate stresses in these taxa do not refute the use of both sprawling and more upright stance among basal theriodont therapsids. Thus, the hypothesis that the use of multiple postures was ancestral to the more upright posture typical of most mammals is biomechanically plausible. Model calculations also indicate that the axial rotation of the femur typical in sprawling locomotion can reduce peak bending stresses. Therefore, as experimental data from alligators and iguanas suggest, the evolution of nonsprawling limb posture and kinematics in therapsids might have been accompanied by increased limb bone bending stress.

Experimental Study on Bending Behavior of Timber Beams Reinforced with CFRP/AFRP Hybrid FRP Sheets

2011 ◽  
Vol 255-260 ◽  
pp. 728-732
Author(s):  
Qing Chun ◽  
Jian Wu Pan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Bearing Capacity ◽  
Strain Distribution ◽  
Failure Modes ◽  
Bending Behavior ◽  
Timber Beams

Based on the experiment of timber rectangle beams made of pine and fir reinforced with CFRP/AFRP hybrid FRP (HFRP) sheets. The failure modes and bending bearing capacity and load-deflection curves and strain distribution at mid-span section were analyzed. The results showed that: Comparing with the specimens without being reinforced by HFRP, there is certain improvement in bending bearing capacity and stiffness of the specimens reinforced with HFRP respectively. Bending bearing capacity of the pine specimens improve 18.1%~62.0% and bending bearing capacity of the fir specimens improve 7.7%~29.7%. Stiffness of the pine specimens improve 13%~21%, and stiffness of the fir specimens improve 6%~10%. Based on the experimental data, the computing formulas of bending bearing capacity of timber rectangle beams made of pine and fir reinforced with HFRP were presented.

A theory for the quantification of transcapillary exchange by tracer-dilution curves

1964 ◽  
Vol 207 (1) ◽  
pp. 162-168 ◽  
Author(s):  
Pablo Martin ◽  
David Yudilevich
Keyword(s):  
Experimental Data ◽  
Turnover Rate ◽  
Mathematical Formulation ◽  
Indicator Dilution ◽  
Capillary Barrier ◽  
Dog Heart ◽  
Tracer Dilution ◽  
Isolated Dog Heart ◽  
Fractional Turnover ◽  
Dilution Curves

A mathematical formulation of the simultaneously obtained indicator-dilution curves of two tracers: one confined to plasma and another diffusible through the capillary barrier, is made. The procedure allows the estimation for the permeable substance of the fractional extraction from the blood, and the interstitial fractional turnover rate and compartment size. The experimental data is obtained in 3–4 min in isolated perfused organs. Na22 (NaCl) and siderophilin-Fe59 first circulation dilution curves obtained in the isolated dog heart are used to exemplify the procedure.

Stability Aspects of Elastomeric Isolators

1997 ◽  
Vol 13 (3) ◽  
pp. 431-449 ◽  
Author(s):  
Maura Imbimbo ◽  
James M. Kelly
Keyword(s):  
Theoretical Analysis ◽  
Critical Load ◽  
Approximate Method ◽  
Experimental Work ◽  
Complete Solution ◽  
Buckling Load ◽  
The Other ◽  
Existing Structures ◽  
End Plate ◽  
Plate Rotation

The theoretical analysis for the buckling of isolators is well known and has generally been verified by experimental work, but there are some aspects of the analysis that have not been addressed in detail. This paper will study two examples, first the effect of end plate rotation on the buckling load and, secondly, the buckling of an isolator that is made up of two bearings, one on the top of the others. The effect of end plate rotation on the buckling load arises in situations where the stiffness of the superstructure is not high enough to ensure that the isolator is constrained against rotation at the top; this is often the case when retrofitting existing structures. The influence of the flexibility of the superstructure on the horizontal stiffness of the isolator and the reduction of the critical load due to this flexibility is evaluated in the paper. The results show a significant reduction of the critical load. The second analysis presented in the paper models the buckling of a composite isolator that is made up of two bearings, one on top of the other. Two approaches for evaluating the critical load of this composite isolator are discussed, and an approximate method is developed that provides results close to the complete solution.

scholarly journals Error estimates for the unilateral buckling load of a plate involving the membrane efforts consistency error

2008 ◽  
pp. 1003-1038
Author(s):  
Mekki Ayadi
Keyword(s):  
Finite Elements ◽  
Error Estimate ◽  
Critical Load ◽  
Error Estimates ◽  
Thin Plate ◽  
Numerical Experiments ◽  
Mesh Size ◽  
Buckling Load ◽  
Plate Model ◽  
Consistency Error

The paper deals with error estimates for the unilateral buckling critical load of a thin plate in presence of an obstacle. The error on the membrane efforts tensor is taken into account. First, using the Mindlin’s plate model together with a finite elements scheme of degree one, an error estimate, depending on the mesh size h, is established. In order to validate this theoretical error estimate, some numerical experiments are presented. Second, using the Kirchhoff-Love’s plate model, an abstract error estimate is achieved. Its drawback is that it contains a hard term to evaluate.

scholarly journals Fatigue fractureof the beam with an internal transverse crack under multicycle loading

2020 ◽  
Vol 17 (2) ◽  
pp. 75-81
Author(s):  
V. I. Smirnov ◽  
◽  
S. A. Vidyushenkov ◽  
S. S. Maier ◽  
◽  
...  
Keyword(s):  
Experimental Data ◽  
Kinetic Equation ◽  
Critical Load ◽  
Crack Growth ◽  
Elastic Foundation ◽  
Cross Section ◽  
Transverse Crack ◽  
Concentrated Force ◽  
Inspection Interval ◽  
Number Of Cycles

The article considers the beam on a solid elastic foundation with an internal transverse crack of circular shape. The cross-section of the beam has the form of an uneven I-beam joist. The beam is exposed to multiple effects of concentrated force. The proposed calculation scheme is aimed at determining the cyclical strength of the railway rails and specifying the inspection interval. The kinetic equation of crack growth has been obtained and the allowable number of cycles has been specified. The critical load with a single static impact is also assessed. The results are compared with the available experimental data.

Dynamic Stability of Sandwich Beams/Wide Plates Subjected to Axial Impulsive Loads

2021 ◽  
Vol 88 (4) ◽  
Author(s):  
Zhangxian Yuan ◽  
George A. Kardomateas
Keyword(s):  
Dynamic Response ◽  
Critical Load ◽  
Dynamic Stability ◽  
Sandwich Panel ◽  
Specific Impulse ◽  
Oscillation Mode ◽  
Buckling Load ◽  
Sandwich Beams ◽  
Impulsive Loads ◽  
Impulse Load

Abstract This paper presents an analysis for the dynamic stability of sandwich beams/wide plates subjected to axial impulsive loads. The formulation and solution of the problem is done by use of the extended high-order sandwich panel theory (EHSAPT). With the initial geometric imperfection included, the equations of motion in terms of seven generalized displacements are derived. The dynamic response of sandwich panels subjected to three different types of impulsive loads, namely, step, linear decay, and triangular impulse, is studied. Furthermore, the effects of the oscillation mode number, face/core materials, and geometries are investigated. It is observed that all measurements of the dynamic response, such as the maximum displacements, strains, and stresses, change at the same rate as the change of the impulse load magnitude and duration, for a specific impulse load profile. When the impulse load is lower than the static buckling load, the dynamic response is bounded no matter how long the load is applied. A step impulsive axial load with magnitude lower than the static buckling load can lead a sandwich panel to have a dynamic response as high as twice the static response. When the impulse load is higher than the static critical load, the dynamic response is unbounded with increasing load duration. However, it is possible that the dynamic response can be controlled at a low level if the duration of the impulse load is short enough, and thus, in this case, the load can safely exceed the static critical load.

The Effects on Critical Load of Metal-Matrix Composite Plates With a Hole Under In-Plane Loadings

2001 ◽  
Author(s):  
F. Okumuş ◽  
A. Turgut
Keyword(s):  
Critical Load ◽  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Numerical Solutions ◽  
Fibrous Composite ◽  
Plate Thickness ◽  
Mathematical Formulation ◽  
Shear Deformation Theory ◽  
Composite Plates

Abstract Metal-matrix composite plates consists of several layers of unidirectionally reinforced, fibrous composite laminae which have different in-plane orientations and are bonded together in a certain stacking sequence. Thus, they provide new materials with superior properties of high strength and stiffness. This study deals with analysis of rectangular metal-matrix composite laminates with circular holes under in-plane static loadings. The first-order shear deformation theory is employed in mathematical formulation. The effects on critical load by hole size, ply lamination geometry, plate thickness ratio, loading types and material modulus ratio have been investigated. The finite element method is used for finding critical loads. Numerical solutions are given in graphical forms.

Plastic Collapse Stresses for Pipes With Circumferential Twin Flaws Using Combination Rules

2018 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Yun-Jae Kim ◽  
Valery Lacroix ◽  
Bohumir Strnadel
Keyword(s):  
Experimental Data ◽  
Stainless Steel ◽  
Analytical Procedure ◽  
The Other ◽  
Plastic Collapse ◽  
Combination Rules ◽  
Steel Pipes ◽  
Other Hand ◽  
Bending Stresses

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by fitness-for-service (FFS) codes, such as ASME, JSME, BS7910, FKM, WES2805, etc. However, specific criteria of the rules are different amongst these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with circumferential twin flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with twin flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with twin flaws are compared with the stresses in compliance with the combination criteria. It is shown that the calculated plastic collapse stresses based on the combination criteria are significantly different from the experimental and analytical stresses.

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