Effect Of Contact Conditions Research Articles

Effect of Contact Condition between Seal Rings on Oil Leakage from Floating Seals

Effect of Contact Condition between Seal Rings on Oil Leakage from Floating Seals

Effects of Contact Conditions at Wire–Die Interface on Temperature Distribution during Wire Drawing

The effects of contact conditions at the wire–die interface on the temperature distribution of the specimen and die are investigated to understand the wire drawing process. Finite element analysis and experiments are performed to analyze the temperature distribution of a drawn wire and die based on different contact conditions using a low-carbon steel wire. The maximum temperature (Tmax) of the die decreases as the contact heat transfer coefficient at the wire–die interface increases, whereas that of the wire increases with the contact heat transfer coefficient. The Tmax of the die and wire decreases with the thermal conductivity of the die. As the thermal conductivity of the die increases, the heat generated by friction is rapidly absorbed into the die, and the Tmax of the die decreases, thus resulting in a decrease in the surface temperature of the wire. The Tmax of both the die and wire linearly increases with the friction factor. In particular, the Tmax of the die more sensitively changes with the friction factor compared with that of the wire. The Tmax of the die linearly increases with the drawing velocity, whereas that of the wire parabolically increases with the drawing velocity. The influence of bearing length on the temperature increase in both the wire and die is insignificant.

Understanding the efficiency of roll lubrication when rolling AD33 aluminium alloy bands in industrial twin mill 175Ч300

This paper describes the results of a study that looked at the effect of contact conditions (including the use of industrial oil I40 (5%) for roll lubrication) on the deformation performance and power draw of a twin cold mill 175×300 operated by the machine building site in Dong Nai, Vietnam, when rolling 0.55 mm thick bands made of aluminium alloy AD33. The initial band size is 0.7×100×2,000 mm. The authors considered reological properties of the aluminium alloy, as well as the roll lubrication environment, to come up with a rational rolling process designed for 0.55×100 mm bands made from 0.7×100×2,000 mm rolled steel. Due to the use of industrial oil I40 (5%) in the mill 175×300, the number of passes could be reduced from three to two. The use of industrial oil I40 (5%) in the twin mill 175×300 ensured the specified precision and helped reduce the loads. Compared with dry rolling, due to the use of industrial oil I40 (5%), the rolling force could be lowered by 6 kN (8.3%) in the first pass and the power draw – by 0.025 kW (3.34%). At the same time, the second pass saved 2.96 kN (5.24%) of rolling force and 0,017 kW (3.95%) of power while ensuring the preset band thickness at the mill exit. Compared with dry rolling, when using I40 oil, the rolling force distribution efficiency along the band length rises by 22.7% in the first pass and by 14.64% in the second pass. When using I40 oil (5%), the strain distribution u nevenness along the band length drops by 39.15% — from 2.35 to 1.43% in the first pass and by 70.08% — from 3.81 to 1.14% in the second pass. When using I40 oil (5%), the thickness distribution along the length of aluminium band at the mill exit is more even than when the rolls are dry or use water. It also results in a minimized longitudinal thickness variation δh – i.e. 0.01 mm. These findings helped develop a rational rolling process for AD33 aluminium alloy bands that relies on the use of industrial oil I40 (5%) to lubricate the rolls of an industrial twin mill, while cutting the loads and saving power.

Transient Numerical Simulation the Friction Stir Welding Process of Aa 2017 Alloys, Contact Parameter Effects on Thermal History and Material Flow

The present work is a 3D transient numerical simulation of material flow and heat transfer during the FSW process. The equations of energy, conservation of mass and momentum were solved in the Eulerian coordinate, in which the spatially variable thermo-physical properties and the non-Newtonian viscosity for the flow of material was calculated taking into account the deformation velocity, the temperature and the properties of the material depending on the temperature. In the purpose of calibrating the proposed model, the effects of contact conditions at the tool / work-piece interface such as the friction coefficient and the slip coefficient on thermal cycles, distribution and the evolution of the maximum value of the temperature have been studied. However, the results obtained show a significant asymmetry of the temperature and mass distribution. Convective heat transport was an important heat transfer mechanism near the tool surface. Furthermore, the numerically simulated temperature value, cooling rates and the length of the thermo-mechanically and thermally affected zone increase with increasing slip coefficient.

DEM Modeling of Crushable Grain Material under Different Loading Conditions

This paper deals with the effect of contact conditions on the crushing mechanisms and the strength of granular materials. The computation of crushable grain material under different loading conditions is performed using 3D model of discrete element method (DEM). The crushable macro-grain is generated from a large number of identical spherical micro-grains which are connected according to the bonded particle model. First, the parameters of the proposed DEM model are calibrated to match the force-displacement curve obtained from Brazilian Tests performed on cylinders made of artificially crushable material. The damage profile right at the point when the force-displacement curve reaches its maximum is seen to replicate the same crack patterns observed in Brazilian test experiments. Then, parametric investigations are performed by varying the coordination number, the contact location distribution, and the contact area. The results show that these parameters play a significant role in determining the critical contact force and fracture mechanism of crushable particles compared to a traditional macro-grain crushing test. Increasing distribution and coordination number of the macro-grain increases particle strength when large area contact is permitted. However, for linear contact area, the effect of increasing coordination number on particle strength is marginal.

Interlayer Gap Effect on the Dynamics and Strength of Two-Layer Metal Composite Cylinders under Internal Explosion

The effect of contact conditions and the gap between the metal and composite layers on the stress-strain state and strength of a two-layer metal composite cylinder under internal explosive loading in air is numerically studied. It is accepted that in the absence of a gap between the metal and composite layers, there is no interference. The problem was considered on the basis of the general equations of theories of elasticity and plasticity in a one-dimensional formulation (plane strain state), which makes it possible to neglect the peculiarities of loading and deformation along the cylinder length. In the absence of an initial gap, the case of perfect contact between the layers was also studied. The inner layer is made of one or another isotropic elastoplastic steel with significantly different yield strengths (steels 20 and 40KhNMA), the outer one is made of an elastic-to-failure cylindrically transtropic circumferentially reinforced composite The dynamic 1D boundary-value problem was solved using the training version of the LS-DYNA software, which is part of the ANSYS commercial application package. The solution method is the Wilkins finitedifference integro-interpolation algorithm included in above software version. It has been established that the strength of the metal composite cylinder under internal explosion is determined by the strength of the outer composite layer under tension in the radial direction and depends nonlinearly and nonmonotonically on the initial gap between the layers. The maximum strength is realized under perfect or non-perfect contact with zero initial gap, and the minimum strength is realized at the initial gap that is roughly equal to a half of the maximum displacement of the inner steel shell in the case of absence of the outer composite layer. To make the reinforcing inner layer, it is inexpedient to use, in terms of strength, structural alloy steels with high yield strength; the steels with low yield strength are more efficient.

Effect of Contact Conditions of Torsional Wave Elastographic Probe on Human Cervix

There is a challenge in characterizing the soft tissue mechanical functionality in cylindrical geometries by current elastography techniques applied to small organs. Torsional waves are a type of shear elastic waves that propagate through soft tissue radially and in depth in a curled geometry, ideally suited to explore structures such as the cervix. Here, a sensor based on a novel arrangement of concentric sandwiches of piezo- and electromechanical elements is prototyped and tested to quantitatively assess stiffness in human cervix. The purpose is to determine the robustness of a torsional wave elastography (TWE) sensor prototype to quantify cervical stiffness, as a first step to validate a reliable measurement protocol using TWE. An array of tests designed to validate a set of hypothesis about the contact conditions were performed on up to 3 different nonpregnant voluntary women. The mechanical properties were reconstructed from the recorded TWE signals, and the outcomes were statistically analyzed to validate the contact condition hypothesis. The results suggest that, although future tests need to be performed to fully assess the repeatability and quality of the measurements, some characteristics of the measurement protocol become clear; in particular: (1) the use of speculum is recommended since it not only stabilizes the measurements, but also corrects and stabilizes the orientation of the cervical neck, and allows to visually verify the positioning and alignment of the probe, while not significantly increasing discomfort to women during this test; (2) the use of lubricant gel has no significant effect on the measurement quality; (3) 1cm off-centering from external cervical os is not acceptable; (4) a range of applied force between 500-2000 N does not significantly vary measurement signal quality, but the reconstructed value of the shear modulus does vary, probably due to its constitutive nonlinearity; (5) breathing movements affects measurements, but short duration of TWE pulse (0.3 s) allows to take measurements in apnea.

Effect of Contact Conditions between Assemblies of Fine Gear on Stress Distribution

Effect of Contact Conditions between Assemblies of Fine Gear on Stress Distribution

Optimization of fretting resistance of modular stem

The modular neck hip prostheses mechanical failure can have several causes, separated or combined such as fretting, corrosion, wear and fatigue. Corrosion mechanism is overcome by specific heat treatment. The fatigue mechanism occurrence is delayed by forging process coupled with finishing process such as shot penning. The breakage of the modular neck becomes mainly related to fretting issues. This is firstly due to the amplitudes of micro-movements of a mismatched geometric tolerance. The effect of contact condition on the fretting behaviour should also be put in relationship with to the used material performances. This study aims to highlight the effect of design parameters on the modular stem fretting resistance. The overall analysis of the results from the design of experiments carried out have shown that a trade-off should to be found between parameters since their variation could be beneficial for fretting wear resistance while becoming unfavorable for fretting fatigue, according to the evaluation criteria.

Effect of contact conditions on limiting state parameters, elasticity moduli and failure modes of rock specimens under compression

The study is devoted to effect of contact friction on failure, ultimate stress and moduli of elasticity in rock specimens under compression. It is found that dependence of the listed characteristics on friction coefficient is incremental. The author reveals zones of full contact and slide.

The Effects of Contact Conditions on the Onset of Shear Instability in Cold-Spray

Using ABAQUS/Explicit, the effects of contact conditions between the particle and substrate, including tangential friction, normal constraint, and contact geometry on the plastic deformation during the cold-spray process are studied. It was found that the onset of shear instability, an event often used to indicate the establishment of bonding, is very sensitive to the choice of contact conditions. This suggests that the onset of shear instability does not serve as an accurate means to identify the plasticity threshold responsible for bonding. On the other hand, it is demonstrated that the evolution of the overall equivalent plastic strain (i.e., $$\overline{\text{PEEQ}}$$ ) and the overall von Mises stress, being linearly proportional to each other, are both independent of contact conditions. Furthermore, it is shown that an energy value, defined as the product of the $$\overline{\text{PEEQ}}$$ and the von Mises stress integrated over all particle elements, can quantitatively represent the energy dissipated via plastic deformation while being independent of contact conditions. The $$\overline{\text{PEEQ}}$$ and associated energy value as defined may provide robust tools to assess the plasticity and the consequent bonding during cold-spray.

Simulation and Experimental Observations of Effect of Different Contact Interfaces on the Incremental Sheet Forming Process

Incremental sheet forming (ISF) is a promising forming process perfectly suitable for manufacturing customized products with large plastic deformation by using a simple moving tool. Up to now, however, the effects of contact conditions at the sheet interface are not well understood. The aim of this work is to study the effect of tool type and size on the formability and surface integrity during the forming process. Experimental tests were carried out on aluminum sheets of 7075-O to create a straight groove with four different tools (ϕ 30,ϕ25.4,ϕ20 andϕ10mm). One tool tip was fitted with a roller ball (ϕ 25.4mm) while the other three were sliding tips. The contact force, friction and failure depth were evaluated. A finite element (FE) model of the process was set up in an explicit code LS-DYNA and the strain behavior and thickness distribution with different tools were evaluated and compared with the experimental results. This study provides important insights into the relatively high formability observed in the ISF process. Microscopic observations of the surface topography revealed that a rolling tool tip produced better surface integrity as compared with a sliding tool tip, wherein, distinct scratch patterns in the tool traverse direction were evident.

Experimental analysis of the fatigue life of threaded pipe connections under cyclic bending

When subjected to cyclic loads, fatigue cracks can cause failure of pipe systems joined bythreaded pipe connections. In this study, the effect of contact conditions and coupling geometry isinvestigated experimentally. Fatigue tests under cyclic bending are carried out on three different threadedconnection configurations. The resulting fatigue lives are compared and fracture surfaces are investigated.The fatigue cracks are found to initiate at the last engaged thread of the pin and fatigue life can beincreased by applying PTFE tape or changing the coupling geometry.

Investigation of thermo-mechanical contact between slider and bit patterned media

Contact between a slider and bit patterned media (BPM) is investigated using finite element analysis. The effect of contact conditions and material properties at the interface between slider and disk on plastic deformation and temperature is studied. In addition, the planarization of bit pattern media on temperature and plastic deformation is investigated for different filler materials. It is found that filler material results in reduction of plastic deformation and temperature.

Effect of contact conditions during thermo-mechanical contact between a thermal flying height control slider and a disk asperity

A three-dimensional thermo-mechanical model is developed for the transient contact between a thermal flying height control (TFC) slider and a disk asperity. The effect of contact conditions is investigated, including the friction coefficient and the circumferential disk velocity. The damage of the read–write shields due to contacts with disk asperities is studied along with the maximum temperature at the location of the read element. The effect of diameter and material properties of the asperity is also investigated. Strong dependence of deformation and maximum temperature is observed as a function of the diameter and material properties of the asperity.

Method Study for Finite Element Modeling of Large Oil Storage Tanks

This article, basing on the field test stress of an oil-storage tank in the site, investigated finite element modeling method for large oil storage tanks. To study the effects of contact conditions among the tank wall, bottom plate and the foundation, the soil of the foundation, and holing on the tank stress, six different finite element models were built by ANSYS finite element analysis software. The stresses in the tank were calculated under the gravity load and the water pressure. Results of the six models have been compared with the field test values. It was obtained for the stress distribution in the tank wall, bottom plate, and big horn weld and around the manhole from which the influence scope and extent to the tank was investigated. It shows that the calculated stresses have a good agreement with measurement. The plane model has enough precision for the tank stress analysis. The contact conditions and soil affect on the stress in the scope with 0.2H and 0.24H (the height of the tank), and holing affects the adjacent area with 2D (the diameter of the manhole).

Effect of Contact Conditions on Void Coalescence at Low Stress Triaxiality Shearing

Recent numerical cell-model studies have revealed the ductile failure mechanism in shear to be governed by the interaction between neighboring voids, which collapse to micro-cracks and continuously rotate and elongate until coalescence occurs. Modeling this failure mechanism is by no means trivial as contact comes into play during the void collapse. In the early studies of this shear failure mechanism, Tvergaard (2009, “Behaviour of Voids in a Shear Field,” Int. J. Fract., 158, pp. 41-49) suggested a pseudo-contact algorithm, using an internal pressure inside the void to resemble frictionless contact and to avoid unphysical material overlap of the void surface. This simplification is clearly an approximation, which is improved in the present study. The objective of this paper is threefold: (i) to analyze the effect of fully accounting for contact as voids collapse to micro-cracks during intense shear deformation, (ii) to quantify the accuracy of the pseudo-contact approach used in previous studies, and (iii) to analyze the effect of including friction at the void surface with the main focus on its effect on the critical strain at coalescence. When accounting for full contact at the void surface, the deformed voids develop into shapes that closely resemble micro-cracks. It is found that the predictions using the frictionless pseudo-contact approach are in rather good agreement with corresponding simulations that fully account for frictionless contact. In particular, good agreement is found at close to zero stress triaxiality. Furthermore, it is shown that accounting for friction at the void surface strongly postpones the onset of coalescence, hence, increasing the overall material ductility. The changes in overall material behavior are here presented for a wide range of initial material and loading conditions, such as various stress triaxialities, void sizes, and friction coefficients.

Vibration Characteristics of Steam Turbine Blades with Straddle Mount (Effect of Contact Condition on Vibration Characteristics)

There are several kinds of blade root structures to support centrifugal forces acting on steam turbine blades such as straddle mount type root, T-root, axial or side entry root and fork type root. Steam turbine blades are surrounded by contact surfaces at a cover and the above blade root. It is known that contact conditions affect vibration characteristics of turbine blades. In this paper, the effects of contact surfaces on vibration characteristics of steam turbine blades with straddle mount type root were investigated. For that purpose, developed analysis method was applied, and natural frequencies and non-linear frequency responses of a steam turbine blade with contact surfaces at the cover and straddle mount type root were obtained using this method. From these results, it was concluded as follows. (1) Natural frequencies of the blade gradually decrease with increasing rotation speed due to the variation of contact area of the blade root. (2) The effect of friction damping at the cover was dominant and the effects at others were small. To verify these results, natural frequencies and dynamic responses of the blades during rotation were obtained in a spin pit test. Calculated results showed good agreement with experiment results and the analysis method was verified.

Effect of Contact Conditions on Growth of Small Crack in Fretting Fatigue

As the general features of fretting fatigue, initiation of fretting fatigue crack is in the very early stage of the fretting fatigue life and there are small non-propagating cracks in the test specimen that doesn't fracture at the fretting fatigue limit. In accordance with these experimental facts, fretting fatigue problem can be considered as a propagation problem of small crack. Thus, a pre-cracked specimen was used in the fretting fatigue test in this study. The objective was to consider the determinant factors of fretting fatigue strength. In the fretting fatigue test, the fretting fatigue limit of the pre-cracked specimen was once reduced and after increased with increase of the contact pressure. The reason was understood by the stress intensity factor of the pre-crack obtained by a finite element analysis. In this study, the fretting fatigue limit can be predicted by the comparison of ΔK of the pre-crack and the propagation threshold of the pre-crack ΔKth. The effect of the relative location of the pre-crack to the contact edge on the fretting fatigue strength was also discussed by both fretting fatigue test and FEM analysis.

J028024 ストレスファイバから細胞核への直接的張力伝達に関する研究 : ストレスファイバと核膜の結合状態の影響

Actin stress fibers (SFs) play important roles in cellular mechanotransduction and regulation of various cellular functions. SFs generate internal tension and contribute to physical interactions between cells and extracellular matrices. We recently found in vascular smooth muscle cells (SMCs) that the dorsal SFs running across the top surface of the nucleus have a mechanical interaction with the cell nucleus and their internal tension is transmitted directly to the nucleus. However, the effects of contact conditions between SFs and nucleus on their force transmission processes are unclear at this stage. In this study, we investigated the contact conditions between SFs and the nucleus using a laboratory-made UV laser nanoscissor. Firstly, we classified the dorsal SFs of SMCs into two types: one had line-like concentrations of intranuclear DNA along the dorsal SFs which may be due to the large compressive forces generated by the SFs (pressing SF), and the other did not have such concentrations of intranuclear DNA (attaching SF). We then cut these SFs by the laser to release their pretension, and observed the dynamic behaviour of nuclei. Following SF dissection, significant nuclear displacement and a decrease of nuclear area were observed in the pressing SF than in the attaching SF. This may indicate that SFs pressing strongly nuclear surface firmly attach to the nuclear membrane. The internal tension of the pressing SFs may be transmitted more efficiently than the attaching SFs to the nucleus, inducing conformational changes of intranuclear DNA.