Nominal Pressure Research Articles

Stability of bucket movement and directionof movement of the continuous unit to form the underlying layer of the road

Introduction.The unit of continuous action for the formation of the underlying layer is designed to increase labor productivity in the construction of roads and other objects, for the construction of which it is necessary to remove the upper layer of soil. The working bodies of the unit are buckets that cut and transport soil. To balance these forces and moments in the transverse-vertical plane, relative to the direction of movement of the buckets, support bars with support hydraulic cylinders are used. To create and regulate the pressure in the support hydraulic cylinders, two hydraulic pneumatic accumulators for controlling the supporting strips are installed on the power device. Part of the forces and moments through the supporting strips, support hydraulic cylinders, the frame of the working part of the unit is transmitted to the energy device that serves to drive the unit. During the operation of the unit, the resistance of the soil to cutting changes continuously. Therefore, the forces and moments transmitted to the energy device change. During operation, the stability of the rectilinear course of the unit is necessary. To ensure the stability of the movement of buckets and the direction of movement of the unit, you should first consider the process of filling the buckets with soil.The method of research.On the basis of the constructive layout, the number of buckets filled with soil was revealed. Suppose the filling of buckets with soil occurs gradually and evenly. Hence, an increase in the load on the right and left support bar was revealed by each subsequent bucket as it is filled. By adding the vertical forces, the value and position of the total load on the supporting bars are determined. The resistance to the movement of the left and right wheels of the working part of the unit, due to the load from the buckets to the supporting strips, the gravity of the raised soil, the gravity of the working part of the unit, is determined. The total horizontal force, the impact of soil on the buckets, directed along the course of the unit, was revealed. The method of calculating the position of the thrust vector of the energy device is given.Results.On the basis of the developed technique, the diameters of the support hydraulic cylinders and the nominal pressure in the hydraulic pneumatic accumulators of the control of the right and left support strips were determined. A constructive layout of the hinged energy device and a system for automatic adjustment of the position of the thrust vector of the energy device depending on the properties of the developed soil is proposed.Conclusion.On the basis of theoretical studies, the diameters of the support hydraulic cylinders and the nominal pressure in the hydraulic pneumatic accumulators of the control of the right and left support strips were calculated. An example of calculating the position of the thrust vector of an energy device is given. The constructive arrangement of the system of automatic adjustment of the position of the thrust vector of the energy device depending on the properties of the developed soil and the general layout of the energy device is proposed. The conducted theoretical studies allow to ensure the stability of the movement of buckets and the direction of movement of the continuous unit for the formation of the underlying layer of roads.

Verification of the differences of scoring effect in current scoring balloons.

The characteristics of each scoring balloon seem to be different because material or configuration of scoring element in each device is unique. The aim of this study is to clarify the difference of scoring effect among 3 different scoring devices. We prepared 3 different scoring devices [Wolverine™Cutting Balloon™(CB), ScoreFlex™NC (SF), NSE Alpha™(NSE), n = 5 respectively. Balloon diameter is 3mm and 2 types of silicone tubes with different elasticity [140kPa (tube S) and 576kPa (tube H), respectively. Inner diameter is 3mm]. We dilated each balloon in each silicone tube with nominal pressure (NP) and 20 atmosphere (HP) and took a picture using a micro CT. We measured penetration depth of all scoring elements into silicone tube wall and calculated their percentage using the following formula; penetration depth/original scoring element height × 100. We also observed the deformation of scoring element during balloon inflation in each device. Scoring element of CB cut deeper into both tubes significantly than SF and NSE at both pressure (40.5% vs 25.1% and 16.8% at NP and 86.1% vs 33.5% and 29.1% at HP in tube S, p < 0.01, respectively, 62.6% vs 33.5% and 17.0% at NP and 93.3% vs 45.1% and 36.5% at HP in tube H, p < 0.01, respectively). Although no deformation of scoring element was recognized in CB, some deformations were observed in 50% of NSE and 40% of SF (p = 0.0377). Scoring balloon with sharp and firmly fixed scoring elements like CB may show definite scoring effect.

Tribological performances of hybrid composites of Epoxy, UHMWPE and MoS2 with in situ liquid lubrication against steel and itself

In this paper, hybrid polymeric composites of epoxy with two solids (UHMWPE and MoS2) and one liquid (base oil SN150) fillers were prepared to improve the thermal, mechanical and tribological properties for load bearing applications. Due to relatively high friction of solid lubricants compared to liquid lubricants, base oil was incorporated into the epoxy composite as liquid filler to achieve enhanced tribological properties. All the experiments were conducted with two interfacial conditions: polymer composite against steel (EN31) and polymer composite against itself. The base oil-filled epoxy composite showed excellent tribological performance with specific wear rate in the range of 10−7 mm3/Nm and low coefficient of friction of 0.08–0.1 at a constant nominal contact pressure of 0.611 MPa and speed 1 m/s. Durable transfer film formation was identified as the main wear reduction mechanism. These fillers also made the surface of epoxy hydrophobic in nature which reduced adhesion and friction. By adding fillers, thermal degradation temperature of the composite was increased by 22.8%. The lubrication mechanism was identified as mixed lubrication with three different sub-regimes.

An injected quantity estimation technique based on time–frequency analysis

An innovative injected quantity estimation method, based on time–frequency​ analysis, has been developed for passenger car Common-Rail (CR) injection systems. This method involves capturing the pressure time history from a transducer installed along the rail-to-injector pipe, and its overall accuracy has been found to be within 1.5 mg. The dependence of the injected mass on the fuel temperature has been investigated, and the correlation of the injected mass with the nominal rail pressure and the energizing time has been evaluated for different thermal regimes. It has been verified that if the duration of the hydraulic injection is considered instead of the energizing time, the influence of the temperature on the injected mass is implicitly taken into account. Thus, the corresponding correlations between the injected mass and the duration of the hydraulic injection have been obtained for different nominal rail pressures. The duration of the hydraulic injection has been measured through an effective time–frequency analysis technique, which has been used to realize a virtual sensor of the needle lift. The experimental campaign has been performed over a wide range of working conditions for single injections, and the accuracy of the innovative prediction methodology, which can be exploited to design a closed-loop control of the injected mass, has been assessed.

Tribological investigations on aluminum alloys at different contact conditions for simulation of deep drawing processes

The tribological condition occurring in aluminum sheet forming processes remarkably affects the part quality and the tool wear. Reliable finite element (FE) models which consider the actual contact conditions are required for successful simulation of aluminum sheet forming. Therefore, tribology experiments are vital for creating contact models which represent the actual tribological system between the tool and the blank. In this work, pin-on-plate tests using plates of aluminum alloys EN AW-5182 EN and AW-6016-T4 were performed at different nominal contact pressures, sliding velocities and surface temperatures for investigating the coefficient of friction (COF). The surface topographies of the aluminum plates, before and after the pin-on-plate tests, were investigated using an optical 3D surface profiler. The obtained COF as well as the surface topographies were imported into the TriboForm R3 software for generating a multi-factor friction model (MFFM), which was subsequently applied in deep drawing simulations using the AutoForm R8 software. The simulation results based on the MFFM were compared to the results based on friction models with constant COF. Moreover, the simulations were validated with deep drawing experiments using a cross-shaped tool at three blankholder forces. The results of the tribology experiments showed that the COF tended to decrease with increasing nominal contact pressure and sliding velocity. However, at elevated temperature the COF increased for both aluminum alloys. Observation of the surface topography after the pin-on-plate tests showed that the plastic deformation of the surface asperities increased with increasing nominal contact pressure. The simulation results based on the MFFM agreed well with the deep drawing experiments at each blankholder force in terms of forming forces, thickness variations and final geometries of the parts.

Analysis of the Erosivity of High-Pressure Pulsating Water Jets Produced in the Self-Excited Drill Head.

The dynamic impact of a water jet with a periodically changing structure can be used in various industries. The paper presents a design solution for a self-excited pulse head. This head can be used in mining for drilling holes and breaking rocks. The design of the head was developed based on computer simulations, which made it possible to learn the mechanism of impulse shaping inside the head. Tests of the water jet produced in the self-excited pulsation head showed the occurrence of periodic changes in its internal structure and pulsation frequency. A significant increase in the dynamic stream pressures was demonstrated for the head working in the water environment compared to the head working in the air environment For example, for nominal medium and highest pressures, this increase is up to 82%, while for the lowest pressures (10 MPa), the pressure force values increase by 46%. It was found that an increase in the nominal water pressure causes a decrease in the frequency of hydrodynamic pulses in the head operating in both the water and air environment.

Strength of Flexible Shell of Pneumatic Springs

The strength for a flexible shell of a vehicle pneumatic spring during movement relative to a rail track has been studied in the paper. The calculation has been carried out using the finite element method implemented in the SolidWorks software environment. For this purpose, 3D drawings of a balloon-type pneumatic spring have been reproduced. A specific feature of the design is that the distance between the upper and lower bottoms in static conditions is unchanged – thanks to the body position regulator, which maintains its constancy relative to the trolley frame. The results obtained have made it possible to conclude that there are certain reserves for the level of stresses, i.e., in addition to the vertical, it is possible to take into account also transverse mutual displacements of the air spring bottoms which will occur when the trolley moves relative to the body. At the next stage, the stresses in the material of the flexible shell are investigated for mutual transverse displacements of the bottoms, which are observed with transverse displacements of the trolleys relative to the body of the vehicle when traveling along curved sections of the track. At the same time, the maximum stresses in the material of the flexible shell of the pneumatic spring are about 11 MPa, even with twice the nominal air pressure and transverse mutual displacements of the bottoms of 40 mm, that is, they are much less than the breaking strength (30 MPa). The carried out researches allow to draw a conclusion that the design and parameters of a flexible shell of a balloon-type air springs ensure its strength under operational loading schemes. Therefore, in order to improve the dynamic qualities of vehicles, it is proposed to use a flexible shell of a pneumatic spring as a component of the spring suspension.

Temperature, Pressure, and Length-Scale Dependence of Solvation in Water-like Solvents. II. Large Solvophovic Solutes.

We use molecular simulation to determine solvation free energies, isochoric solvation energies and entropies, isobaric solvation enthalpies and entropies, partial molecular volumes, and isothermal density derivatives of the solvation free energy as a function of temperature and pressure for hard-sphere solutes with diameters ranging from 4 to 36 Å in TIP4P/2005 and Jagla water-like solvents exhibiting unusual thermodynamics. An important piece of our discussion focuses on the nanometer-sized solutes, for which simulation results are found to be accounted for by the most basic classical thermodynamic treatment contemplating bulk and interfacial contributions to the solvation free energy. Thus, since water's liquid-vapor surface tension is only special inasmuch as it takes unusually large values, solvent's water-like unusual thermodynamics manifests through a term proportional to the pressure in the solvation free energy. As a result, such solvent's unusual thermodynamics is found to be relevant to the temperature and pressure dependence of the isochoric solvation energy and entropy as well as to the isothermal density derivative of the solvation free energy. This sharply contrasts with the findings of the first part of this series indicating that the solvation free energy of small hard spheres responds to temperature and pressure changes as solvent's density does, with such a contrasting picture embodying a "pressure-density dichotomy." As for the length-scale dependence, we find the zero nominal pressure and the solvent's temperature of the maximum density as singular conditions for cavity surface-area size scaling of large solutes to occur for all solvation quantities. We finally argue that the overall study undertaken in this series suggests that water's unusual thermodynamics may be relevant to the thermodynamic stability of clusters of solvophobic units in the temperature-pressure plane. Some comments on the role of solute-solvent attractive interactions are also depicted.

Effect of Lubricant Type on the Friction Behaviours and Surface Topography in Metal Forming of Ti-6Al-4V Titanium Alloy Sheets

The aim of the research described in this paper is to analyse the synergistic effect of types of synthetic oil and their density on the value of the coefficient of friction (COF) of Ti-6Al-4V titanium alloy sheets. Lubrication performance of commercial synthetic oils (machine, gear, engine and hydraulic) was tested in a strip draw friction test. The friction tests consisted of pulling a strip specimen between two cylindrical fixed countersamples. The countersamples were placed in the simulator base mounted on a uniaxial tensile test machine. Due to the complex synergistic effect of different strip drawing test parameters on the COF, artificial neural networks were used to find this relationship. In the case of both dry and lubricated conditions, a clear trend was found of a reduction of the coefficient of friction with nominal pressure. Engine oil 10W-40 was found to be the least favourable lubricant in reducing the coefficient of friction of Grade 5 titanium sheets. The two main tribological mechanisms, i.e., galling and ploughing, played the most important role in the friction process on the test sheets. In the range of nominal pressures considered, and with the synthetic oils tested, the most favourable lubrication conditions can be obtained by using a type of oil with a low viscosity index and a high kinematic viscosity.

Assessment of the effectiveness of lubrication of Ti-6Al-4V titanium alloy sheets using radial basis function neural networks

The aim of the research presented in this article was to determine the value of the friction coefficient using a simple tribological test and to build an empirical model of friction with the use of radial basis function artifi-cial neural networks. The friction tests were carried out on a specially designed friction simulator that allows a sheet metal strip to be drawn between two fixed dies. The test materials were sheets of Ti-6Al-4V titanium alloy with a thickness of 0.5 mm. The friction tests were carried out with variable contact forces of counter-samples with rounded surfaces and in various lubrication conditions. Mineral oils and bio-degradable oils with the addition of boric acid (5 wt %) were tested. Based on the results of friction investigations, neural models of friction were built using RBF artificial neural networks. The good properties of the RBF network 2:2-35-1:1 were confirmed by a high value of the determination coefficient R2 = 0.9984 and a low value of the S.D. ratio equal to 0.0557. It was found that the COF value was the highest for the average values of both the nominal pressure and kinematic viscosity. Over the entire range of nominal pressures applied, SAE10W-40 engine oil ensured the most effective reduction of the COF. The COF value was the highest for the average values of both the nominal pressure and kinematic viscosity.

Evaluation of Shock Tube Retrofitted with Fast-Opening Valve for Dynamic Pressure Calibration

Accurate dynamic pressure measurements are increasingly important. While traceability is lacking, several National Metrology Institutes (NMIs) and calibration laboratories are currently establishing calibration capacities. Shock tubes generating pressure steps with rise times below 1 μs are highly suitable as standards for dynamic pressures in gas. In this work, we present the results from applying a fast-opening valve (FOV) to a shock tube designed for dynamic pressure measurements. We compare the performance of the shock tube when operated with conventional single and double diaphragms and when operated using an FOV. Different aspects are addressed: shock-wave formation, repeatability in amplitude of the realized pressure steps, the assessment of the required driver pressure for realizing nominal pressure steps, and economy. The results show that using the FOV has many advantages compared to the diaphragm: better repeatability, eight times faster to operate, and enables automation of the test sequences.

მაღლივი კორპუსების გაზმომარაგება

When the pressure of natural gas changes, a significant level difference appears between the gas control point and the location of the consumer. In this case, the pressure value may exceed safety standards. In buildings, supplying gas to the burner with a value other than the nominal pressure causes incomplete combustion of the fuel and the formation of carbon monoxide. Leakage of natural gas at pressures above the nominal leads to a rapid increase in the percentage of gas in the room air above the lower concentration limit of explosiveness, which makes the mixture explosive. In this regard, in some countries, building codes do not allow gasification of buildings above 10 floors. In Georgia, such a ban does not exist and this problem becomes relevant, since a large number of high-rise buildings have been built in the country and almost 100% of them are gasified.

Linear and Nonlinear Normal Interface Stiffness in Dry Rough Surface Contact Measured Using Longitudinal Ultrasonic Waves

When two rough surfaces are loaded together contact occurs at asperity peaks. An interface of solid contact regions and air gaps is formed that is less stiff than the bulk material. The stiffness of a structure thus depends on the interface conditions; this is particularly critical when high stiffness is required, for example in precision systems such as machine tool spindles. The rough surface interface can be modelled as a distributed spring. For small deformation, the spring can be assumed to be linear; whilst for large deformations the spring gets stiffer as the amount of solid contact increases. One method to measure the spring stiffness, both the linear and nonlinear aspect, is by the reflection of ultrasound. An ultrasonic wave causes a perturbation of the contact and the reflection depends on the stiffness of the interface. In most conventional applications, the ultrasonic wave is low power, deformation is small and entirely elastic, and the linear stiffness is measured. However, if a high-powered ultrasonic wave is used, this changes the geometry of the contact and induces nonlinear response. In previous studies through transmission methods were used to measure the nonlinear interfacial stiffness. This approach is inconvenient for the study of machine elements where only one side of the interface is accessible. In this study a reflection method is undertaken, and the results are compared to existing experimental work with through transmission. The variation of both linear and nonlinear interfacial stiffnesses was measured as the nominal contact pressure was increased. In both cases interfacial stiffness was expressed as nonlinear differential equations and solved to deduce the contact pressure-relative surface approach relationships. The relationships derived from linear and nonlinear measurements were similar, indicating the validity of the presented methods.

NUMERICAL ESTIMATION OF DAMAGE CAUSED BY THE IMPACT OF AN EXERCISE TORPEDO ON A SUBMARINE PRESSURE HULL STRUCTURE

Torpedo combat and evasion training exercises using trials torpedoes are valuable but involve significant risks to the target submarine in the event of an accidental impact. This paper presents a study of impacts of a nominal heavyweight torpedo against a nominal submarine pressure hull, simulated using the nonlinear explicit finite element analysis code LS-Dyna. The model is validated against experimental work published by the Australian Defence Science and Technology Organisation, then expanded to a segment of a full-size submarine. Impacts were simulated at torpedo speeds of 30, 40 and 50 knots. It was found that the 30 knot impact produced no plastic deformation in the pressure hull, while the 40 and 50 knot impacts produced permanent dents of several mm depth. Reference is made to DNV GL submarine structures rules to suggest that these dents will not impair operational capability.

Influence of Equi-Biaxial Residual Stress on Spherical Indentation of Strain Hardening Materials

Residual stress plays an important role in the mechanical performance of engineering structures. In this paper, the indentation of pre-stressed strain hardening materials by a rigid sphere is simulated through the finite element method. It is shown that the mean contact pressure in the post-yield regime keeps continuously increasing with the indentation proceeding. Compared to the case without residual stress, compressive residual stress tends to increase the mean contact pressure at a given indentation depth, while tensile stress has an inverse effect. To quantitatively indicate the influence of residual stress, a nominal contact pressure is defined, which obtains its maximum value at a critical depth. The dependences of the maximum nominal pressure and the critical indentation depth on the residual stress and the material properties are determined explicitly through large numbers of simulations. Inspired by the nominal pressure deviation stemmed from residual stress, a new approach is proposed for measuring residual stress through spherical indentation tests.

Nature and timing of anatectic event of the Hida Belt (Japan): Constraints from titanite geochemistry and U-Pb age of clinopyroxene-bearing leucogranite

The Hida Belt, central Japan, is a continental fragment, which was once a part of the crustal basement of the East Asian continental margin. It consists mainly of Permo-Triassic granite-gneiss complexes with both syn-to-late-metamorphic migmatite or granite bodies. Clinopyroxene-bearing leucogranite, locally called as ‘Inishi’-type migmatite, occurs characteristically in the migmatite zone associated with amphibolite and marble. The leucogranite is characterized by the presence of coarse-grained diopside–hedenbergite series clinopyroxene and titanite in plagioclase-dominated matrix. Clinopyroxene contains abundant calcite inclusions. Euhedral titanite with high Th/U ratios (~2.8–7.8) and REE contents (~4514–14,069 μg/g) contains polycrystalline ‘granitic’ inclusions. Those mineralogical features indicate the involvement of carbonate during anatexis. Considering a nominal pressure of 0.4–0.7 GPa of the Hida gneiss, Zr-in-titanite thermometry yields a temperature of 730–810 °C and 770–850 °C at aTiO2 = 0.5 and 1, respectively. The titanites show highly variable U/Pb (238U/206Pb = 15.0–24.0) and Pb (207Pb/206Pb = 0.172–0.419) isotope ratios, and the scattered trend follows a discordia line with a lower intercept at 225.4 ± 1.9 Ma. This titanite age would represent the timing of regional anatexis that have occurred in a later stage of the regional metamorphism of the Hida Belt. A high apparent thermal gradient at middle crustal levels might have been caused by regional extension.

Influence of Narrow Rectangular Channel ( AR = 1 : 4 ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

Effective cooling of blades with a nominal pressure drop is essential for performance augmentation and thermal management of gas turbines. Hence, present work is aimed at determining the heat transfer enhancement and friction for W- and V-shaped ribs inside a rectangular cooling channel having hydraulic diameter ( D h ) of 0.048 m and aspect ratio ( AR ) 1 : 4. Ribs are fixed facing downstream with angle of attack ( α ) 45° on opposite walls. Pitch ( P ) between two successive ribs is 25 mm for both cases. Continuous V- and W-shaped ribs with height to channel hydraulic diameter ratio ( e / D h ) 0.052 and 0.0416 and pitch to height ratio ( P / e ) 10 and 12.5, respectively, have been examined for Reynolds number ( Re ) range 20000-80000. Heat transfer augmentation achieved at Re 80000 is 1.94 and 1.8 times higher than Re 20000 for V- and W-shaped ribs, respectively. Streamwise and spanwise variations in local Nusselt number ratio are highest for V-shaped ribs, which are estimated to be 31% and 12%. For W-shaped ribs, variations are 17.5% and 3.5%. Nusselt number ( Nu ) is highest along span length 0.5 w for V-shaped ribs due to dominance of apex induced secondary flow. For W-shaped ribs, Nusselt number along the span lengths is found to be nearly same view uniformity in secondary flow. Maximum enhancement ( Nu / N u o ) estimated for both the rib shapes is 3.9 at Re 20000. Due to increased rib height, friction losses for V-shaped ribs are higher than W-shaped ribs. Maximum friction loss increment is estimated to be 85% for V-shaped ribs and 42% for W-shaped ribs between Re 20000 and 40000. For both rib shapes, impact of ribs is found to be greatest at Re 40000. Thermohydraulic performance ( THP ) for W-shaped ribs is superior to V-shaped ribs. Best THP achieved for W- and V-shaped ribs are 3.7 and 3.4 at Re 20000.

A comprehensive kinetic study on the speciation from propylene and propyne pyrolysis in a single-pulse shock tube

This work is centered on the speciation from propylene and propyne pyrolysis by means of shock tube experiments and detailed kinetic modeling. A wealth of intermediates and products, covering small acyclic hydrocarbons up to four-ring aromatics, are probed from the C3 fuels pyrolysis at a nominal pressure of 20 bar over 1050–1650 K. With updates in reactions involving C3 species, our on-going polycyclic aromatic hydrocarbon (PAH) formation kinetic model can well predict the measurements obtained in the current work as well as relevant literature data. Propyne exhibits a unique two-stage decomposition profile, as the characteristic isomerization to allene dominates in its consumption at moderate temperatures below 1300 K. Overall, propylene pyrolysis results in more diverse small hydrocarbons, but much lower contents of aromatics, in comparison to propyne pyrolysis. In both studied cases, the formation of benzene is dependent upon the propargyl recombination, and since propyne decomposition induces a more rapid and more plentiful propargyl production, benzene mole fractions are much higher in propyne pyrolysis. In both cases, naphthalene is observed as the most abundant PAH species, followed by acenaphthalene. Modeling analyses indicate that similar reaction pathways are responsible for the PAH formation in propylene and propyne pyrolysis. Indene is formed from the interactions between benzene/phenyl and C3 species, through its non-PAH isomers as intermediates. The subsequent reactions of indenyl radical with methyl and propargyl are essential pathways leading to naphthalene and acenaphthalene, respectively. Naphthyl radical further participates in the formation of different larger PAHs. The methylene-substituted cyclopenta-ring species are deemed as important precursors of their aromatic isomers, as is noted from the fulvene-to-benzene, benzofulvene-to-naphthalene and 9-methylene-fluorene-to-phenanthrene conversions.

Finite element analysis of cutting balloon expansion in a calcified artery model of circular angle 180°: Effects of balloon-to-diameter ratio and number of blades facing calcification on potential calcification fracturing and perforation reduction.

Calcified artery lesions cause stent under-expansion and increase the risk of in-stent restenosis and stent thrombosis. Cutting balloons facilitate the fracturing of calcification prior to stent implantation, although vessel dissection and perforation are potential issues. In clinical practice, calcifications having maximum calcium angles ≤ 180° are rarely fractured during conventional balloon angioplasty. We hypothesize that the lesion/device diameter ratio and the number of blades facing a non-circular calcified lesion may be crucial for fracturing the calcification while avoiding vessel injury. The geometries of the cutting balloons were constructed and their finite-element models were generated by folding and wrapping the balloon model. Numerical simulations were performed for balloons with five different diameters and two types of blade directions in a 180° calcification model. The calcification expansion ability was distinctly higher when two blades faced the calcification than when one blade did. Moreover, when two blades faced the calcification model, larger maximum principal stresses were generated in the calcification even when using undersized balloons with diameters reduced by 0.25 or 0.5 mm from the reference diameter, when compared with the case where one blade faced the calcified model and a balloon of diameter equal to the reference diameter was used. When two blades faced the calcification, smaller stresses were generated in the artery adjacent to the calcification; further, the maximum stress generated in the artery model adjacent to the calcification under the rated pressure of 12 atm when employing undersized balloons was smaller than that when only one blade faced the calcification and when lesion-identical balloon diameters were used under a nominal pressure of 6 atm. Our study suggested that undersized balloons of diameters 0.25 or 0.5 mm less than the reference diameter might be effective in not only expanding the calcified lesion but also reducing the risk of dissection.

Effects of punch geometry and grain size in micron scale compression molding of copper

Mechanical size effects at small characteristic dimensions are of intense current interest. In addition to the relevance for microfabrication, microscale compression molding provides a rich laboratory in which mechanical size effects manifest in interesting ways, especially as the characteristic molding dimension approaches the average grain size of the material being deformed. We investigate the effects of punch geometry and grain size on the mechanical response and gap filling behavior in micron scale compression molding. Micron scale long rectangular single-, double-, and triple- punch molding was conducted on polycrystalline Cu with varying grain sizes. Mechanical size effects were observed regarding the compression pressure and the material flow to fill the gaps between neighboring punches. The nominal compression pressure depended significantly on the punch width in single-punch molding and on the spacing between neighboring punches in double-punch molding. Analysis of double- and triple- punch molding data showed that both the punch geometry and the grain size of the molded Cu influence the Cu gap filling behavior in significant ways. Detailed microstructural examinations of molded Cu features were carried out to elucidate the underlying mechanisms. Our findings offer new data on micron scale plasticity and test cases for validating micron scale plasticity models.