Compressed Ring Research Articles

Analysis of Friction Factor in Cold Forging by using Ring with Triangular Boss Compression Test

ABSTRACT The ring compression test, a quantitative method to evaluate various conditions of friction at the interface of the dies and work piece by the analysis of diametric (inner) change in the dimension and height of the ring in metal forming. After the compression, it is difficult to measure the inner diameter precisely due to nonuniform deformation. To overcome these difficulties in the conventional ring compression test, an alternative method named RTB-CT is proposed in which two types of geometries of the ring were used one is the ring with the equilateral triangular boss and the other is the ring with isosceles triangular boss. In conventional approach of determination of coefficient of friction of the lubricants, the Ring compression test was used. But, the accuracy of the results through this test was directly linked to the measurements of the different parameters of the compressed ring under the application of the lubricant and due to bulging effect of the ring, the measurement of the inner diameter was difficult. In proposed RTB-CT, this difficulty was overcome by eliminating the measurement of inner diameter of the deformed ring and using a boss on the ring which makes the process of measurement easier and accurate.

Frictional behavior during cold ring compression process of aluminum alloy 5052

The friction is the considerable boundary condition in bulk metal forming. In this paper, the ring compression test was used to evaluate the friction coefficient and factor in Coulomb friction model and Tresca friction model for the plastic deformation of aluminum alloy AA5052. The micro-macro analysis method combining surface morphology and micro-texture was used to explore the friction behaviors in AA5052 cold forming process. In general, the magnitude (μ or m) of friction changes before and after a deformation threshold during ring compression. The maximum change rate of the magnitude (μ or m) before and after the deformation threshold is close to 18.5% under the present experimental conditions, and the change rate decreases with increasing loading speed. The lubrication using MoS2 is better than that using oil at lower speeds (0.15 mm/s, 1.5 mm/s), but the lubrications for MoS2 and oil are similar at higher speeds (15 mm/s). The surface roughness, three-dimensional topography, and surface texture of compressed ring have a sudden change around the deformation threshold, which deviate from the previous evolution trend. The increased friction after deformation threshold also promotes the formation of sufficient shear strain layer in the subsurface plane of the compressed ring, and then it hinders the formation of the typical deformation textures with β-oriented line and promotes the appearance of shear textures such as 001110, 111uvw and hkl110 textures.

Variation of the friction conditions in cold ring compression tests of medium carbon steel

Lubrication and friction conditions vary with deformation during metal forming processes. Significant macro-variations can be observed when a threshold of deformation is reached. This study shows that during the cold compression processing of #45 (AISI 1045) steel rings, the magnitude of friction and surface roughness (Ra) changes significantly upon reaching a 45% reduction in ring height. For example, the Ra of compressed ring specimens increased by approximately 55% immediately before and after reaching this threshold, compared to an 18% or 25%variation over a 35%-45% or a 45%-55% reduction in height, respectively. The ring compression test conducted by this study indicates that the Coulomb friction coefficient μ and Tresca friction factor m are 0.105 and 0.22, respectively, when the reduction in height is less than 45%; and 0.11 and 0.24, respectively, when the reduction in height is greater than 45%.

Poincaré series of compressed local Artinian rings with odd top socle degree

We define a notion of compressed local Artinian ring that does not require the ring to contain a field. Let (R,m) be a compressed local Artinian ring with odd top socle degree s, at least five, and socle(R)∩ms−1=ms. We prove that the Poincaré series of all finitely generated modules over R are rational, sharing a common denominator, and that there is a Golod homomorphism from a complete intersection onto R.

Non-linear finite element modelling and analysis of the effect of gasket creep-relaxation on circular bolted flange connections

It is well known that gasket creep-relaxation results in a reduction of contact pressure between the surface of a gasket and the face of a flange over an extended period of time. This reduction may result in the subsequent failure of the circular bolted flange connection due to leakage. In this paper a pair of flat and raised face integral flanges, PN 10 DN 50 (in accordance with the European EN 1092-1 standard), with non-asbestos compressed fibre ring gaskets with aramid and a nitrile rubber binder were considered. Finite element modelling and analyses were done, for both the circular bolted flange configurations, during the seating condition. The results of the finite element analyses were experimentally validated. It was found that the number of bolt tightening increments as well as the time between the bolt tightening increments had a significant impact on the effect which gasket creep-relaxation had after the seating condition. An increase in either the number of bolting increments or the time between the bolting increments will reduce the effect which gasket creep-relaxation has once the bolts had been fastened. Based on these results it is possible to develop an optimisation scheme to minimize the effect which gasket creep-relaxation has on the contact pressure between the face of the flange and the gasket, after seating, by either increasing or decreasing the number of bolt tightening increments or the time between the bolt tightening increments.

Effects of thickness and fibre misalignment on compression fracture in cross-ply (very) long cylindrical shells under external pressure

Combined effects of modal imperfections, transverse shear/normal deformation with/without reduced transverse shear modulus, G LT (caused by distributed fibre misalignments), on emergence of interlaminar shear crippling type instability modes, related to localization (onset of deformation softening), delocalization (onset of deformation hardening) and propagation of mode II compression fracture/damage, in thick imperfect cross-ply very long cylindrical shells (plane strain rings) under applied hydrostatic pressure, are investigated. Of special interest is the question: what are the geometric and/or material parameters that induce localized and delocalized states in imperfect cross-ply (very) long cylindrical shells under hydrostatic compression simultaneously, and what would be the consequences of such occurrences? The primary accomplishment is the (hitherto unavailable) computation of the layer-wise mode II stress intensity factor, energy release rate and kink–crack bandwidth, under hydrostatic compression, from a nonlinear finite-element analysis, using Maxwell's construction and Griffith's energy balance approach. Additionally, the shear crippling angles in the layers are determined using an analysis, pertaining to the elastic inextensional deformation of the compressed (plane strain) ring. Numerical results include effects of (i) thickness-induced transverse shear/normal deformation and (ii) uniformly distributed fibre misalignments, on localization and delocalization, and consequently on compression fracture/damage characteristics of thick imperfect cross-ply very long cylindrical shells.

Cell Biology: Cohesin Rings Leave Loose Ends

Cohesins function in almost all aspects of chromosome biology. Two new studies confirm that a subset of cohesin subunits form a flexible but compressed ring that can be opened through degradation. X-ray crystallography supports potentially differing regulation of subunit associations.

Contact solutions for a circular orthotropic beam accounting for transverse normal strain

A higher order orthotropic circular beam theory, which accounts for radial and circumferential normal strain, as well as deformations due to transverse shearing and bending, is developed using the principle of virtual work. As such, the governing differential equations are expressed in terms of the four independent stiffness quantities, EA1, EA2, GA and EI. Special cases that can be obtained by appropriate limits include a Timoshenko beam (GA, EI) and an Euler beam (EI) with or without axial extension (EA2). Using these equations the frictionless contact problem of a compressed ring is solved analytically and the significance of transverse normal strain is studied by comparing with solutions from the more elementary beam theories. Furthermore, the limitations of these theories are studied through comparison with plane elasticity solutions obtained using finite elements. The effect of the radial stiffness (EA1) on the contact pressure is quantified and shown to be important for many practical problems, such as a tire that includes the effect of a tread.

Development of the theoretical model for the optimal design of surface texturing on cylinder liner

In this paper, based on the Reynolds equation and the dynamic operation conditions of cylinder liner and piston ring of CY6102 type diesel engine, a theoretical model of the load carrying capacity and film thickness for the first compressed ring were developed. Based on the theoretical models, the effects of the texturing parameters on the load carrying capacity and film thickness were investigated under different velocities, and the ranges of optimum texturing parameters were found. An optimal texturing design method on cylinder liner was proposed. It shows that on cylinder liner, texturing with variable parameters in different velocity ranges can produce higher load carrying capacity and film thickness than that with invariable parameters.

Conformational behavior of hexahydropyrimidin-2-one and its ammonium and oxonium ions

Substituted hexahydropyrimidin-2-ones possess a broad spectrum of biological activity and can serve as radioprotectors, immunostimulators, central nervous system regulators, herbicides, and antitumor agents as well as in fine organic synthesis [1–3]. These molecules feature a highly compressed chair ring in the heteroatomic segment [4]. On the other hand, the conformational behavior of these compounds has hardly been studied. In the present work, the HF/6-31G(d) and PBE/3z methods from the HyperChem [5] and PRIRODA [6] program packages, respectively, were used in the first study of the conformational properties of hexahydropyrimidin-2-one and its ammonium and oxonium ions. These molecules, similar to cyclic carbonates [7], display interconversions between two energydegenerate compressed chair forms through a transition state (TS) close to the 2,5-twist form (2,5-T).

Flattening of a long multilayered viscoelastic cylindrical shell with a varying wall thickness

The stability of a multilayered linearly viscoelastic cylindrical shell with a varying wall thickness under the action of uniformly distributed lateral pressure is investigated. Assuming that the shell is sufficiently long and neglecting the influence of its fastening, the problem posed is reduced to the examination of stability of a compressed ring. The urgency and importance of such problems are connected with the search for reserves of saving of materials with simultaneously increasing the bearing capacity of the structure. In solving problems of this class, the geometric nonlinearity must also be taken into account. The acquisition of efficient analytical solutions here is a rather difficult and sometimes impossible task. This is connected with the integration of nonlinear boundary-value problems with discontinuous coefficients. Therefore, to avoid the existing mathematical obstacles, the problem is solved by using a variational method of mixed type in combination with the Rayleigh–Ritz method. For a three-layer ring with a symmetric structure relative to its median surface, the effect of various geometrically nonlinear theories and of the varying wall thickness on the critical time of stability is revealed numerically.

A stability of oxide layers formed in LBE on HCM12A to external loading

Stability of oxide layers associated under applied external load was investigated for oxide layers formed on the inner surface of a steel pipe in flowing LBE with respect to fracture behavior, fracture mechanism and nano-hardness. Ring specimens obtained from the pipe were compressed by a compression test machine, and a fracture of the inner oxide layers was observed. Cracks crossed the oxide layers occurred from the interface between the oxide layers and the base metal to the surface of oxide layers and delamination of oxide layers occurred at the Fe–Cr spinel layer in flatted part of compressed ring specimen. In the compressed part of the ring specimens, all oxide layers were spalled off from the base metal. Engineering strains in the base metal near oxide layers were determined from the deformation of micro-indentation sizes. A tensile strain component to the circumferential direction was responsible for the cracking. It appears that the tensile strain component in the radial direction was responsible for the delamination of the oxide layers. Nano-hardness and Young’s modulus of each oxide layers were measured by a nano-indentation method for the evaluation of the fracture behavior. Young’s modulus of Fe–Cr spinel layer is lower than that of Fe 3O 4 layer by 10% with the same hardness in both layers, which yields excess strain to the spinel layer rather than to the Fe 3O 4 layer and consequently causes cracking.

Modeling of Scaphocephaly Using Superelastic Titanium-Nickel Rings: A Preliminary Report

As long as resection of sagittal suture eliminates craniostenosis it leads to desired cranium broadening and shortening solely in the case of children under six months of age. In the majority of cases, especially in older children, boat-shaped cranium remains rather unchanged and its effective modeling requires extensive dissection and osteotomy of the whole cranium vault (e.g., frontal, occipital and parietal bones). Lauritzen's method is an alternative solution. It consists of distraction of cranium vault bones with the aid of steel springs. In order to simplify and improve the efficacy of treatment since 2002, the authors originated the application of titanium-nickel rings to model the cranium. After the sparing excision of cranium vault sutures in the shape of letter "H" the compressed ring is given in the sagittal axis oval shape and in this form it is fixed to osseous margins. The ring's expansion at the same time broadens and shortens the cranium vault. Material was analyzed from 7 children (range, 9 months to 4 years of age), who were treated in the years 2002-2006 because of sagittal craniostenosis. Observations made so far and good treatment results indicate purposefulness of discussed treatment continuation.

Localization, Delocalization, and Compression Fracture in Moderately Thick Transversely Isotropic Bilinear Rings Under External Pressure

A fully nonlinear finite element analysis for prediction of localization∕delocalization and compression fracture of moderately thick imperfect transversely isotropic rings, under applied hydrostatic pressure, is presented. The combined effects of modal imperfections, transverse shear∕normal deformation, geometric nonlinearity, and bilinear elastic (a special case of hypoelastic) material property on the emergence of interlaminar shear crippling type instability modes are investigated in detail. An analogy to a soliton (slightly disturbed integrable Hamiltonian system) helps understanding the localization (onset of deformation softening) and delocalization (onset of deformation hardening) phenomena leading to the compression damage∕fracture at the propagation pressure. The primary accomplishment is the (hitherto unavailable) computation of the mode II fracture toughness (stress intensity factor∕energy release rate) and shear damage∕crack bandwidth, under compression, from a nonlinear finite element analysis, using Maxwell’s construction and Griffith’s energy balance approach. Additionally, the shear crippling angle is determined using an analysis, pertaining to the elastic plane strain inextensional deformation of the compressed ring. Finally, the present investigation bridges a gap of three or more orders of magnitude between the macro-mechanics (in the scale of mms and up) and micro-mechanics (in the scale of microns) by taking into account the effects of material and geometric nonlinearities and combining them with the concepts of phase transition via Maxwell construction and Griffith-Irwin fracture mechanics.

Surface modification of tool steel by MOS2 powder shooting

This paper describes surface modification of tool steel by MoS2 powder shooting technology and the lubricating ability of such MoS2 shot tool steel for metal-forming applications. This method introduces a MoS2 shot layer of approximately 1.5μm into the surface of the tool steel by shooting MoS2 powder with pressurized air. Friction measurements indicated that the friction properties of such MoS2 shot tool could be remarkably improved. Ring compression tests were performed to measure the lubricating ability of the MoS2 shot tool during large deformation processes, which indicated a lower coefficient of friction compared to the case of no lubrication. Consequently, the surface roughness of compressed ring and the seizure between tool and ring could be improved.

On the collapse of wave packets in a medium with normal group velocity dispersion

A solution to the problem of realizing the collapse of three-dimensional wave packets in nonlinear media with normal group velocity dispersion is proposed. Wave packets with pronounced hyperbolic topology are shown to collapse; i.e., the field increases infinitely near the system axis. In particular, wave collapse of the tubular axisymmetric packets occurs through the concentration of the compressed ring field distribution at the axis. The collapse is shown to stabilize due to the saturation of nonlinearity or nonlinear dissipation, which restrict the field increase and lead to the packet splitting in the transverse direction.

Synthesis and electrochemical polymerization of bis-dithienyl cyclophane

Functionalized compressed ring cyclophanes are interesting oligomers because such compounds may provide as interchain connections or recombining fluorescent center when they are polymerized into a conducting polymer. The synthesis and the electro-oxidation of bis-dithienyl cyclophane are reported along with the main electrochemical characteristics of the resulting polymer.

Modeling the Initiation and Growth of Delaminations in Composite Structures

A method for modeling the initiation and growth of discrete delaminations in shell-like composite structures is presented. The laminate is divided into two or more sublaminates, with each sublaminate modeled with four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements, and makes the two opposing shell elements act as a single shell element until a prescribed failure criterion is satisfied. Once the failure criterion is met, the connection is broken, and a discrete delamination initiates or grows. This approach has been implemented in a three-dimensional finite element code. This code uses explicit time integration, and can analyze shell-like structures subjected to large deformations and complex contact conditions. Tensile, compressive, and shear laminate failures are also modeled. This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delamination, and discusses associated implementation issues. In addition, calculated results for double cantilever beam and end notched flexure specimens are presented and compared to measure data to assess the ability of the present approach to model a growing delamination. Results are also presented for a diametrally compressed ring to demonstrate the capability for analyzing progressive failure in a highly deformed composite structure.

Aperture Synthesis Observations of CS, NH3, and Continuum in the Bipolar Flow Source NGC2071-IRS

ABSTRACT.We have made aperture synthesis observations of CS(J=l-0, 2-1) and NH3(1,1) lines and 49, 98, and 110 GHz continuum in NGC2071-1RS with the Nobeyama Millimeter Array. Wfe have obtained maps of these lines and continuum maps with 2”. 7-20” resolution, ffe have found that dense molecular gas has a disk structure with a radial scale ranging 0.01 pc - 0.1 pc and has a ring-like structure with expanding motion at the central 5000 AU region. We also have found that there exists double dust continuum sources which are separated by 2500 AU in projection and are apparently located at the inner edges of the ring. Our observational results suggest that the disk of molecular gas has a central hole formed by wind and UV radiation from a central young stellar object, the central part is expanding, and that dust continuum emission comes from tangential parts of the shock compressed ring (r~1300 AU, M(H2)~ 21-34 Mo, and n(H2)~ 109) at the most inner side of the disk structure. The other possible model of the dust continuum sources is a binary system of self-luminous young stellar objects.

Experimental and theoretical correlations for elastic buckling of axially compressed ring stiffened cylinders

Re-examination of some 85 past experiments on the elastic buckling of axially loaded ring stiffened cylinders shows the existence of two distinctive behavioural regimes. Lightly stiffened cylinders, like isotropic cylinders, buckle into non-axisymmetric modes having long axial wavelengths at loads that are sensitive to the precise magnitudes of small initial imperfections. Heavily stiffened cylinders are characterised by snap buckling into axisymmetric modes which, for elastic behaviour at least, show only limited sensitivity to initial imperfections. Each of these characteristics is shown to be predicted by the recently developed ‘reduced stiffness analysis’ method, which, despite the relatively perfect nature of test specimens, predicts reliable lower bounds to the experimental scatter. Taken together with the previously demonstrated empirical validity of the reduced stiffness analysis for the prediction of buckling modes and lower bounds to buckling loads for both isotropic and stringer stiffened cylinders, the present comparisons provide further support to the recommendation that this method be considered as an alternative basis for future design.