Hole Deformation Research Articles

Defect chemistry and thermodynamic properties of proton dissolution into BaZr0.9Y0.1O3 − δ

Proton concentration in BaZr0.9Y0.1O3−δ was measured by highly-accurate thermogravimetry as functions of temperature and p(H2O), and thermodynamic properties of the proton dissolution were discussed. Apparent Gibbs free energy change of the proton dissolution reaction changes with proton concentration even at a constant temperature. This means the proton dissolution in BaZr0.9Y0.1O3−δ is not ideal-solution-like. The deviation from the ideal solution became more significant with increasing temperature i.e. decreasing the proton concentration. This indicated the interaction between oxygen vacancies or electron hole, dopant-defect interaction, or lattice deformation may cause the proton dissolution in BaZr0.9Y0.1O3−δ especially at higher temperature.

Electron\u2013acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V−1 s−1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

Study on pilot hole deformation by punching

Progressive die has some forming stages. The feeding of sheet material is necessary to obtain a forming product. In general, the sheet material used in the forming process is located using a pilot pin and pilot hole. It is important for keeping feeding accuracy that the deformation of the pilot hole is decreased in the punching stage of progressive die forming. In this paper, the deformation of a pilot hole by punching is discussed on the basis of the results of an experiment. A pilot hole and pilot pin were deformed by punching under various experimental conditions in this study. The deformation of the pilot hole and pilot pin decreased with increasing distance between the punch and pilot hole. Increasing the distance between the pilot pin and punch was effective for decreasing the dimensional changes of the pilot hole and the deflection of the pilot pin. The material flow in the lateral direction was observed using indentations produced by a micro-Vickers hardness testing machine. The material flow decreased with increasing distance from the punch. It is concluded that the material flow is useful data for deciding the positions of the pilot hole and pilot pin.

Thermoelastic analysis of a two-dimensional decagonal quasicrystal with a conductive elliptic hole

A general solution in terms of the Stroh-type formalism for quasicrystals is developed for two-dimensional thermoelastic deformation. The solution is then applied to analyze the deformation of a conductive elliptic hole embedded in the decagonal quasicrystal plane which is under a remotely uniform heat flow. The hoop stresses around the elliptic hole are derived in an exact closed form. When the thermal conductivity inside the hole is neglected, the present results are reduced to the existing solutions in the literature. Some numerical examples are provided to show the effects of the geometrical shape of the hole and the thermal conductivity inside the hole on the hoop stresses. The results show that along the hole the variations of the hoop stress of the phonon field are completely different from those of the phason field. Compared to the corresponding insulated case, consideration of a conductive elliptic hole would lead to very different and interesting thermoelastic behaviors.

A comparison of split sleeve cold expansion in thick and thin plates

Split sleeve cold expansion is a widely used process in the aerospace industry to enhance the fatigue life of rivet holes in the aircraft structures. In the experimental investigation presented in this article, the full-field in-plane residual strains and the out-of-plane surface deformations around open cold-expanded holes were measured using stereoscopic digital image correlation in aluminium specimens of two different thicknesses giving thickness-to-diameter ratios of 0.25 and 1. The results demonstrate that the mechanics of hole deformation is significantly different for the thick and thin specimens. The specimens of 1.6 mm thickness underwent a combination of global bending and significant local warping during the cold expansion process. This localised warping caused a decrease in the minimum principal residual strains close to the edge of the hole, which cannot be predicted by the existing theoretical models as they do not account for the complex out-of-plane deformations that have a significant influence on the shape of the resulting residual strain profiles. In contrast, 6.35-mm-thick specimens did not bend globally mainly because of the higher second moment of area of their cross sections. The material close to the hole edge bulges out from both the faces of the specimen as a result of plastic deformation during the cold expansion process and the out-of-plane deformations are much more localised and lower in magnitude in comparison to the thin specimens. The plastic zone developed around the expanded hole is more axisymmetric and larger in size for the thick specimens. These results imply that the existing split sleeve cold expansion process is not as effective in creating a uniform compressive residual elastic stress field around the fastener holes in thin as it is in the thick specimens.

Non-linear regime of the Generalized Minimal Massive Gravity in critical points

The Generalized Minimal Massive Gravity (GMMG) theory is realized by adding the CS deformation term, the higher derivative deformation term, and an extra term to pure Einstein gravity with a negative cosmological constant. In the present paper we obtain exact solutions to the GMMG field equations in the non-linear regime of the model. GMMG model about $AdS_3$ space is conjectured to be dual to a 2-dimensional CFT. We study the theory in critical points corresponding to the central charges $c_-=0$ or $c_+=0$, in the non-linear regime. We show that $AdS_3$ wave solutions are present, and have logarithmic form in critical points. Then we study the $AdS_3$ non-linear deformation solution. Furthermore we obtain logarithmic deformation of extremal BTZ black hole. After that using Abbott-Deser-Tekin method we calculate the energy and angular momentum of these types of black hole solutions.

Bearing factors of cold-formed stainless steel double shear bolted connections at elevated temperatures

A numerical investigation on double shear bolted connections of cold-formed stainless steel at elevated temperatures is described in this paper. A finite element model is developed in this study. The model was verified against stainless steel double shear bolted connection tests. It is shown that the finite element model is able to predict the test strengths and failure modes of the connections. Therefore, an extensive parametric study of 225 stainless steel double shear bolted connections at 5 different temperature levels was performed. Based on both the test and numerical results, bearing factors are proposed for the bearing strengths of stainless steel double shear bolted connections at elevated temperatures. Two sets of bearing factors are proposed based on the true plastic strains in the bolt hole and the bolt hole deformation. The connection bearing strengths obtained from the tests and finite element analysis were compared with the nominal strengths calculated using the current American, Australian/New Zealand and European specifications for stainless steel structures as well as the modified design rules in this study. In calculating the nominal strengths of the connections, the material properties of stainless steel obtained at elevated temperatures were used. It is shown that the modified design rules provided more accurate predictions compared to the current design predications for bearing strengths of stainless steel double shear bolted connections at elevated temperatures. The reliability of the current and modified design rules was evaluated using reliability analysis.

에폭시 프라이머 도료의 에어리스 스프레이 분사 시간에 따른 팁 노즐 침식마모경향과 분사특성 연구

Airless spray which is widely used for painting to ship blocks and hull sides is the coating method for attaching atomized paint material to the substrate using spray tip nozzle with compressed air. When the paint material which has high solid contents such as epoxy primer paint is atomized by passing through spray tip nozzle with high pressure, the nozzle composed of tungsten carbide(WC) undergoes the erosive wear, leading to widening of nozzle hole. The deformation of nozzle hole induces improper spray pattern and coating failures such as finger pattern and sagging because the conditions of spray pump pressure and paint flow rate for developing full spray pattern are changed. In this study, an appropriate replacement cycle of spray tip was predicted by measuring the erosive wear tendency as increasing the spraying time of epoxy primer paint.

면외변형의 영향을 받는 알루미늄합금 일면전단 볼트접합부의 내력평가에 관한 실험적 연구

Many researchers have studied the structural performance of bolted connection with aluminum alloys and design specifications for in-plane fracture (net-section, bearing and block shear fractures) of bolted connection have been improved by their study results. However, it can be known from study results conducted by Kim et al. that curling (out-of-plane deformation) could be negative effect (strength reduction) on ultimate strength of single shear bolted connection fabricated with 3.0mm thick aluminum alloy(6061-T6) plate. Strength reduction for curled single shear specimens obtained from the comparison of test results for double shear bolted connections ranged from 4% to 30%. In this paper, additional experiments are performed in order to investigate the influence of curling on ultimate strength and curling occurrence condition for 4.0mm thick bolted connection. Main variables are end distance and edge distance. In all specimens, strength reduction by curling was observed. Strengths obtained from test results were compared with design strengths predicted by AISI (American Iron and Steel Institute) and AAA (American Aluminum Association) design rules. Bearing factor considering curling effect and hole deformation limit was discussed.

An alternative evaluation method for friction condition in cold forging by ring with boss compression test

Ring compression test (RCT) is a very popular method used to quantitatively evaluate friction conditions at the tool–workpiece interface by measuring the variations of the inner diameter of the ring in metal forming. There are many possibilities for measuring the inner diameter variations in RCT because of non-uniform deformation of the inner hole during the test. Such non-uniform deformation of the inner hole causes difficulties in precise measurement of the inner diameter and hence the accuracy of the derived friction coefficient. To avoid the disadvantage in dimension measurement of the conventional RCT, an alternative method for evaluating friction conditions in cold forging named ring with boss compression test (RCT-B) is proposed. By the introduction of the RCT-B concept, finite element simulation results under different friction conditions were obtained. Results showed that the shape of the outer boss remains stable during the compression deformation and allows the diameter of the outer boss to be measured more easily and accurately. The calibration curves of the RCT-B concept were constructed by using FE simulation, which cover the range of friction conditions in cold forging process. Finally, the RCT-B method was successfully applied to determine the friction factors of four different lubricating conditions in compression of aluminum rings. Furthermore, the phenomena with different lubricating conditions between the upper and lower die–workpiece interfaces were also studied using both simulation and experimental testing. The results show that it is possible to quantitatively assess the difference of friction conditions at the upper and lower die–workpiece interfaces by simply checking the inclined angle of the outer boss with the RCT-B method.

Quantitative analysis of deformation in hollow cylinder tests on anisotropic clay formations

A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay. The aim of this testing program is to better understand the anisotropic deformation during the excavation. The testing conditions are similar to those to be experienced by host rocks around disposal galleries for radioactive waste. X-ray computed tomography is performed at different steps for each test with the samples remaining inside the loading cell. Initial analysis of the tomography images allows of the observation of the deformation of the central hole. In addition, particles manual tracking and 3D volumetric digital image correlation processing methods are considered being used to analyze the particles displacements and the boundary deformation of the sample quantitatively. An unsymmetrical damaged zone is induced around the hole, with a reverse deformation trend being found at the boundary after unloading, which indicates that the significant anisotropic deformation of boom clay can be induced by mechanical unloading.

SOME ASPECTS OF DYNAMIC RIVETING SIMULATIONS

Riveting is a commonly used (especially in aircraft structures) method of joining metal and composite components. The methods of forming solid shank rivets can be classified in two types: static and dynamic. The static method is the most efficient one. Regrettably, its application is limited. A popular upsetting tool used in an aircraft is a pneumatic riveter. The rivet driving requires a few hammer strokes. The total stress in a riveted joint depends on the residual and applied stress. Residual post-riveting stress fields are widely accepted to have a beneficial influence on the fatigue life of aircraft structures. The analysis is carried out for a solid mushroom rivet (made of PA25 alloy) joining two sheets (made of 2024T3 alloy). Nonlinear dynamic simulations of the upsetting process are carried out. Simulation of the riveting process is significantly influenced by a material model. The numerical calculations are performed for three different cases of upsetting described by the formed rivet head diameters 1.4d, 1.5d and 1.6d, respectively. The rivet head diameter and, consequently, the residual stress state depend on hammer stroke energy. It has a significant influence on a plastic region around the rivet hole, whereas the influence of a number of strokes can be neglected. The strain rate in both local and global (average) formulation is analysed in the paper. For one hammer stroke, the global strain rate of the rivet shank is about 1.0 thousand per second. The local strain rate is about two times greater than the global one, so a strain rate factor has an effect on the residual stress state. For a few hammer strokes, the strain rate is lower than for one stroke; however, it increases a little in each stroke. The hole deformation can be treated as a function of the internal energy of the sheet. The lower total energy of the part the greater influence of the strain rate on the internal energy is observed.

Off-diagonal deformations of kerr black holes in Einstein and modified massive gravity and higher dimensions

We find general parameterizations for generic off-diagonal spacetime metrics and matter sources in general relativity (GR) and modified gravity theories when the field equations decouple with respect to certain types of nonholonomic frames of reference. This allows us to construct various classes of exact solutions when the coefficients of the fundamental geometric/ physical objects depend on all spacetime coordinates via corresponding classes of generating and integration functions and/or constants. Such (modified) spacetimes display Killing and non-Killing symmetries, describe nonlinear vacuum configurations and effective polarizations of cosmological and interaction constants. Our method can be extended to higher dimensions which simplifies some proofs for embedded and nonholonomically constrained four-dimensional configurations. We reproduce the Kerr solution and show how to deform it nonholonomically into new classes of generic off-diagonal solutions depending on 3-8 spacetime coordinates. Certain examples of exact solutions are analyzed and that are determined by contributions of new type of interactions with sources in massive gravity and/or modified f(R,T) gravity. We conclude that by considering generic off-diagonal nonlinear parametric interactions in GR it is possible to mimic various effects in massive and/or modified gravity, or to distinguish certain classes of "generic" modified gravity solutions which cannot be encoded in GR.

Influence of interference fit size on hole deformation and residual stress in hi-lock bolt insertion

The interference fit can improve the fatigue performance of mechanical joints and is widely used in aircraft assembly. In this paper, specimens of lap plates and several interference fit sizes were designed, and then the interference fit hi-lock bolt insertion was carried out in an experimental test. Using the commercial finite element software ABAQUS, a two-dimensional axisymmetric finite element model was established to simulate the bolt insertion process. The finite element model was validated by comparison of experimental results and finite element prediction for insertion force and protuberance height. After the interference fitted bolt insertion, the changing characteristics of the non-uniform hole expansion and protuberance were presented with increases in interference fit size. Under low level of interference fit, the tensile hoop stress was produced mainly on the hole wall, and changed into compressive hoop stress when interference fit size is larger. The maximum tensile hoop stress point on faying surfaces went away from the hole wall with interference fit size increasing.

Including realistic tidal deformations in binary black-hole initial data

A shortcoming of current binary black-hole initial data is the generation of spurious gravitational radiation, so-called junk radiation, when they are evolved. This problem is a consequence of an oversimplified modeling of the binary's physics in the initial data. Since junk radiation is not astrophysically realistic, it contaminates the actual waveforms of interest and poses a numerical nuisance. The work here presents a further step towards mitigating and understanding the origin of this issue, by incorporating post-Newtonian results in the construction of constraint-satisfying binary black-hole initial data. Here we focus on including realistic tidal deformations of the black holes in the initial data, by building on the method of superposing suitably chosen black hole metrics to compute the conformal data. We describe the details of our initial data for an equal-mass and nonspinning binary, compute the subsequent relaxation of horizon quantities in evolutions, and quantify the amount of junk radiation that is generated. These results are contrasted with those obtained with the most common choice of conformally flat (CF) initial data, as well as superposed Kerr-Schild (SKS) initial data. We find that when realistic tidal deformations are included, the early transients in the horizon geometries are significantly reduced, along with smaller deviations in the relaxed black hole masses and spins from their starting values. Likewise, the junk radiation content in the $l=2$ modes is reduced by a factor of $\sim$1.7 relative to CF initial data, but only by a factor of $\sim$1.2 relative to SKS initial data. More prominently, the junk radiation content in the $3\leq l\leq8$ modes is reduced by a factor of $\sim$5 relative to CF initial data, and by a factor of $\sim$2.4 relative to SKS initial data.

Free-volume hole relaxation in molecularly oriented glassy polymers.

The free-volume hole relaxation in polycarbonate and poly(methyl methacrylate) with different levels of molecular orientation was studied by positron annihilation lifetime spectroscopy at variable pressures. The molecular orientation was achieved through a simple shear process performed at different temperatures and extrusion rates. It has been demonstrated that the β relaxation is largely responsible for the free-volume hole anisotropy after simple shear orientation. Upon the removal of mechanical force, the deformation of the free volume is mostly reversible at temperatures much lower than the glass transition. No strong correlation between macroscopic deformation and the free-volume hole deformation was found regardless of molecular orientation.

Black strings from minimal geometric deformation in a variable tension brane-world

We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the Eötvös branes, where the variable brane tension is related to the Friedmann–Robertson–Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geometric deformation of a black hole on the variable tension brane, the black string has a throat along the extra dimension, whose area tends to zero as time goes to infinity.

Cutting and deformation of deep holes in continuous-casting rollers

A hybrid tool for producing deep holes in the rollers of continuous-casting machines is proposed. The tool ensures high precision and machining quality and also reduces machining costs.

Research on the influence rules of hole type on the quality of sheet embedded cold-pressing joining

The method of embedded cold-pressing joining could achieve the joining of sheets with different thickness and the joining of dissimilar sheets. Besides, it could meet the lightweight request easily. This article expounded the joining mechanism of this method deeply. To expound the joining mechanism of this method, this article has taken aluminum and stainless steel as examples. In addition, numerical stimulation studies of different hole types’ connecting processes had shown that it was easier to reach plastic yield conditions for aluminum and deform it under the same load conditions. The deformation achieved was significantly greater than that for stainless steel. The width increment of the joining parts increased with the increase of the load pressures; however, the thickness changes of the joining parts behaved in an opposite manner. When the pressing volume of the punch reached 2.4 mm, with the width increment of aluminum sheets of the square hole reaching 2.78 mm, which was the maximum width increment, followed by the hexagonal hole, and the round hole being a minimum. Hole type had a small influence on the width of stainless steel sheets. The experimental results of different hole type joining process indicated that compared with round hole and hexagonal hole, the filling of the square hole was relatively difficult. In case of unreasonable process schemes, defects such as “fake joining,” “offset loading” and “hole deformation” would occur. Thus, this article provided a theoretical basis for the scheme establishment and quality control of the embedded cold-pressing joining process.

Exact asymptotically flat charged hairy black holes with a dilaton potential

We find broad classes of exact 4-dimensional asymptotically flat black hole solutions in Einstein-Maxwell theories with a non-minimally coupled dilaton and its non-trivial potential. We consider a few interesting limits, in particular, a regular generalization of the dilatonic Reissner-Nordstr{\"o}m solution and, also, smooth deformations of supersymmetric black holes. Further examples are provided for more general dilaton potentials. We discuss the thermodynamical properties and show that the first law is satisfied. In the non-extremal case the entropy depends, as expected, on the asymptotic value of the dilaton. In the extremal limit, the entropy is determined purely in terms of charges and is independent of the asymptotic value of the dilaton. The attractor mechanism can be used as a criterion for the existence of the regular solutions. Since there is a `competition' between the effective potential and dilaton potential, we also obtain regular extremal black hole solutions with just one U(1) gauge field turned on.