Range Of Test Speeds Research Articles

Throttling effect on the availability and sustainability of a gasoline-fuelled spark ignited multi-cylinder engine

Large energy waste is one of the internal combustion engine challenges, making it unsustainable and unfriendly to the environment. Charging the spark ignition engine with the required fuel-air mixture is associated with a particular quantity of energy loss due to flow throttling. Throttle position effect on the availability, sustainability, and environmental trends of a gasoline, spark-ignited engine was evaluated based on thermodynamic analyses of real experiments. The availability and sustainability analyses were performed utilizing the relations governing the thermodynamic system under various engine speeds (1500–4000 rpm) at part and wide-open throttle (POT and WOT) conditions. The results indicated that the WOT position mostly ensures the best sharing of useful availability, i.e., 2% greater, more sustainable, i.e., 3% better, and environmentally friendly, i.e., 16% healthier, engine operation for the entire tested speed range. On the other hand, an optimum engine speed, mostly 3000 rpm, of the tested engine yielded the maximum efficiencies, i.e., 3% higher, lowest entropy production, i.e., 15% lower, and best availability proportions, as well as the most sustainable and environmentally friendly operation mode. Furthermore, a considerable perspective of the waste heat recovery of the associated availability with exhaust gases was achieved under POT and WOT conditions. The acquired improvement in engine efficiency based on the recovery potential was in the range of 3% to 19.7% and 13.6% to 24% for the WOT and POT conditions, respectively. However, the detected recovery rate and efficiency improvement were randomly tended with engine speed variation. In terms of the recovery potential, the highest engine efficiencies were about 46% and 50% at 3000 rpm, for the POT and WOT conditions, respectively. Finally, in average around 10% and 52% increment with 20% and 24% reduction was detected for the environmental impact of the CO2, NOx, CO and HC, respectively, under the WOT condition in comparison with POT condition.

Hydrodynamic Tests of Innovative Tourist Submarine

This paper deals with the resistance, towing, seakeeping, and open water propeller tests of an innovative tourist submarine model. Tests were performed in a 276 m long towing tank. As the submarine model is a complex structure composed of various parts attached to the pressure hull, the largest possible model, in the scale of 1:5.0, was produced, considering the towing tank depth and the capabilities of the measurement equipment. Resistance tests were performed in deep water and on the surface in calm water. The tested speed range in both cases was up to 5.5 knots. To ensure the avoidance of free surface effects, resistance tests in deep water were performed for different draughts and then extrapolated to infinite water depth. Smaller effective powers were found for the surface condition. The results are compared to an independently performed computational fluid dynamics (CFD) analysis using OpenFOAM. A fair agreement between the experimentally and numerically predicted effective power is found, while the reasons for the differences found are explained. The free submarine model was towed with a rope performed for the speed range 1.7 kn–3.5 kn, and the towing force in the rope was measured. Seakeeping tests in irregular beam waves at zero speed were performed to check the flooding risk on open hatches. Open water tests of the main thrusters for propelling the submarine were conducted, indicating that both power demand and propeller thrust are slightly larger compared to the initial estimates.

ANALYSIS OF TEST EQUIPMENT FOR INVESTIGATION OF MATERIALS UNDER A STRONG LOAD APPLICATION

An analysis of modern testing equipment to establish the mechanical properties of different in structure and origin of building materials. As a result, it was established, that the most effective for testing are foreign electromechanical and servo-hydraulic machines of different configurations. It is determined that this type of technical systems allows to study different types of materials, including high-strength, compressive, tensile, bending and other types of loads in accordance with current international regulations. The article analyzes the principles of operation of the universal test machine INSTRON and the universal servo test machine UIT STM 100S. The configuration of such modern technical systems involves the availability of electronic computers and software, which allows testing in automatic mode, program research factors, determine the current and maximum values of mechanical properties of building materials, perform mathematical calculation of characteristics, reproduce information on the device screen, build research diagrams in electronic and printed form. It has been found that the advantages of such test machines are a load of up to 60 tons. It was determined that the universal machine UIT STM 100S is characterized by a large traverse stroke and a wide range of test speeds, which allows to expand the solution of quality control problems in industry. It is also established that the UIT STM 100S has software that includes a standard library of test methods according to regulatory documentation. The advantages of such a machine are the possible expansion of the standard information base necessary for the operation of the standards or the installation of an additional software module that provides the ability into independently supplement the standard library. Given the wide range of measurements of the universal testing machine UIT STM 100S, we envisage its use for the study of deciduous and coniferous wood in modern rigid test mode.

Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton

BackgroundWalking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the metabolic penalty of the exoskeleton mass make it challenging to develop an exoskeleton that can reduce the metabolic energy during both gaits. Here we show that the metabolic energy of both walking and running can be reduced by regulating the metabolic energy of hip flexion during the common energy consumption period of the two gaits using an unpowered hip exoskeleton.MethodsWe analyzed the metabolic rates, muscle activities and spatiotemporal parameters of 9 healthy subjects (mean ± s.t.d; 24.9 ± 3.7 years, 66.9 ± 8.7 kg, 1.76 ± 0.05 m) walking on a treadmill at a speed of 1.5 m s−1 and running at a speed of 2.5 m s−1 with different spring stiffnesses. After obtaining the optimal spring stiffness, we recruited the participants to walk and run with the assistance from a spring with optimal stiffness at different speeds to demonstrate the generality of the proposed approach.ResultsWe found that the common optimal exoskeleton spring stiffness for walking and running was 83 Nm Rad−1, corresponding to 7.2% ± 1.2% (mean ± s.e.m, paired t-test p < 0.01) and 6.8% ± 1.0% (p < 0.01) metabolic reductions compared to walking and running without exoskeleton. The metabolic energy within the tested speed range can be reduced with the assistance except for low-speed walking (1.0 m s−1). Participants showed different changes in muscle activities with the assistance of the proposed exoskeleton.ConclusionsThis paper first demonstrates that the metabolic cost of walking and running can be reduced using an unpowered hip exoskeleton to regulate the metabolic energy of hip flexion. The design method based on analyzing the common energy consumption characteristics between gaits may inspire future exoskeletons that assist multiple gaits. The results of different changes in muscle activities provide new insight into human response to the same assistive principle for different gaits (walking and running).

The effect of vehicle weight on the sound produced by transverse rumble strips

Transverse rumble strips (TRS) are commonly used as traffic calming measure in the vicinity of premises. So far research have been extensively concentrated on the effect of vehicle type and speed on the noise produced by TRS, and very little research focused on the effect of vehicle weight. Do these vehicles produce extremely higher sound level parallel to their heavier weight? This is important as in reality, traffic flow consist of light, medium and heavy vehicles, which are also important sources of noise. This study investigated the effect of vehicle weight, such as gross vehicle weight (GVW) when transited on TRS, particularly with emphasis on impulsivity content. The objectives of this research were to: (1) determine the effect of GVW on noise generation when a vehicle transits on TRS and (2) assess the effect of GVW on the impulsivity of noise. Data from vehicles with weight between 800 kg - 8000 kg were collected based on previous research where these vehicles were tested on speed values of 30km/h and 50km/h. It was found that when the vehicles transited on TRS, the generated noise was strongly related with the vehicle weights (R2=0.71) higher than those normal road surface (R2=0.49). However, the changes of noise were not well represented by direct relation. It was found that TRS can increase and decrease the sound pressure level, depending on GVW, but on average, TRS can increase the sound pressure level by 1 dBA. Despite that, TRS was found to have an impulsive characteristic within the tested speed range. This finding can facilitate the authority to evaluate the environmental noise produced by TRS.

Investigation of planing vessels motion using nonlinear strip theory – an experimental and numerical study

ABSTRACTThis study is aimed to improve Zarnick’s (1978, A nonlinear mathematical model of motions of a planing boat in regular waves. David W. Taylor Naval Ship Research and Development Center, Bethesda, MD, USA) analytical model for motions of planing vessels. A nonlinear time domain mathematical model was developed for dynamic behaviour of longitudinal motion of high-speed planing crafts in regular waves. This model was based on two-dimensional strip theory method using expanding wedge theory and momentum. Due to the nonlinearity and complex dynamic behaviour of these vessels, the time-domain simulation was adopted. Total resistance, heave and pitch motions as well as acceleration were found very sensitive to hydrodynamic coefficients. Furthermore, a set of forced oscillation and seakeeping tests on a vessel were carried out for different conditions at the Marine Engineering Research Centre of Sharif University of Technology (MERC). The effect of velocity, wavelength, and hydrodynamic coefficients were investigated on vessel motions. According to the results, decreasing added mass coefficients, velocity of the model increases. The amplitude of heave and pitch motions declined due to an increase in velocity, within the tested speed range, or by reduction of λ/L ratio. Hydrodynamic coefficients of the mathematical model have been modified accordingly, and the model represented a better agreement with the experimental data obtained by Fridsma (1969. A systematic study of the rough-water performance of planing boats. Tech. Rep. Davidson Laboratory, Stevens Institute of Technology, Hoboken, NJ, USA). This model was applied to identify the nonlinear dynamics of these vessels in both semi-planing and planing phases that can be further expanded to hybrid vessels in the future.

DEVELOPING AND EVALUATION OF A SHELLING/CRACKING MACHINE SOME AGRICULTURAL PRODUCTS - (SHELLING OF JATROPHA FRUITS)

This study aims to develop a shelling/cracking machine for dry agricultural products and evaluate performance of developed machine for shelling of Jatropha curcas L. fruits (JCFs) cultivated in Egypt. All shelling experiments of JCFs were carried out at average moisture content of 11.45, 8.48 and 13.89 % (d.b.) for whole fruits, seeds and shells, resp. The results showed that the suggested design of the prototype achieved high efficiency in shelling of JCFs. Under the tested speed range[200 (2.094) to 600 rpm (6.283 m/s)] and the tested clearance range [12 to 16 mm], the shelling efficiency of JCFs gradually increased with increasing the tested speeds and decreasing the clearances. The speed of 600 rpm is the optimal for the shelling efficiency at clearance of 12 mm. Under the tested sample mass range[250 to 1500 g], the results showed that the mass sample of 1000 g is the optimal for shelling efficiency and productivity of machine, whereas; the mean values of broken seeds percentage (%-age) were not significantunder the tested sample mass range. Also; the results revealed that the highest value of machine productivity was 226.08 kg/h. Meanwhile; the average values of shelling efficiency, %-age of broken seeds, unshelled fruits and intact seeds were 95.90, 0.43, 4.10 and 57.93 %, resp. Further; the mean values of power consumption and specific energy requirement were 694.95 W and 3.07 W.h/kg, resp. In addition to the level of emitted noise from developed machine was 97.2 dB and should be reduced to the permissible limits (90 dB) at exposure period of 8 h/day.

A micro-cam actuated linear peristaltic pump for microfluidic applications

A linear peristaltic pump has been designed, fabricated, and tested for microfluidic applications. The operation of the pump is based on synchronously compressing the microfluidic channel with a miniature cam-follower system. The flexible microfluidic channel was fabricated with elastomer polydimethylsiloxane (PDMS) using soft lithography. The miniature cam-follower system was fabricated using three-dimensional (3D) printing technology. The prototype pump is self-priming and tolerant of bubbles. The pumping flowrate under zero back pressure increases with the rotation speed of the cams within the tested speed range. A maximum pumping flow rate of 274μL/min was achieved at a driving speed of 170rpm. The maximum back pressure was over 36kPa. The pump has simple structure, low cost, and is easy to control. It has great potential for application in high flow rate, high back pressure and none contact pumping environment for point-of-care (POC) microfluidics.

EGR Effect On Performance of a Spark Ignition Engine Fueled with Blend of Methanol-Gasoline

This paper examines the results of performance of a single cylinder spark- ignition engine fuelled with 20% methanol +80% gasoline (M20), compared to gasoline. The experiments were conducted at stoichiometric air–fuel ratio at wide open throttle and variable speed conditions, over the range of 1000 to 2600 rpm. The tests were conducted at higher useful compression ratio using optimum spark timings and adding recirculated exhaust gas with 20% to suction manifold.&#x0D; The test results show that the higher compression ratio for the tested gasoline was 7:1, 9.5:1 for M20 and 9:1 for M20 with added EGR. M20 at higher useful compression ratio (HUCR) and optimum spark timing (OST) characteristics are significantly different from gasoline. Within the tested speed range, M20 consistently produces higher brake thermal efficiency by about 6%. Also it resulted in approximately 3.06% lower brake specific fuel consumption compared with gasoline. Adding EGR to M20 caused reduction in HUCR and advancing the OST. This addition increased brake specific fuel consumption (BSFC), reduced brake thermal energy, volumetric efficiency and exhaust gas temperatures.

Design of an underwater positioning sensor for crawling ship hull maintenance robots

In recent years there has been a significant increase in the automation of ship hull maintenance tasks such as cleaning, paint stripping, and in-water inspection. This is driven by several factors including reduction in cost, environmental hazard, and impact on the health of workers. The development of autonomous systems has been limited by the availability of suitable position sensors capable of providing accurate and repeatable information to a robot control system. This paper presents the development of an optical position sensor (OPS) suitable for use both underwater and in air, and designed to operate on a crawling ship hull robot. The OPS provides dead-reckoning position data which may be used in conjunction with a landmark position sensor for navigation of a robot. The OPS was based on an optical mouse sensor and telecentric lens and has been shown to provide accurate position information over a range of test speeds and working distances and when operating under non-ideal conditions in terms of angle with respect to the ship hull surface.

Dry sliding wear response of zinc-based alloy over a range of test speeds and loads: a comparative study with cast iron

This study pertains to the observations made during the sliding wear response of a zinc-based alloy in different test conditions. The effects of sliding speed and load on the wear behaviour of the alloy have been studied. The properties evaluated were wear rate, frictional heating and coefficient of friction. The wear performance of the zinc-based alloy has been compared with that of a conventional cast iron in identical test conditions. The wear rate of the samples increased with applied load and sliding speed while the seizure resistance (load) deteriorated with speed. The zinc-based alloy exhibited less wear rate and reduced frictional heating than that of the cast iron while friction coefficient followed a reverse trend. Observed wear response of the samples has been discussed in terms of specific features like lubricating, load carrying, microcracking and thermal stability of various microconstituents of the samples, and substantiated further through the features of wear surfaces, subsurface regions and debris.

The influence of matrix modification on fracture mechanisms in rubber toughened polymethylmethacrylate

The fracture behavior of composite rubber particle-toughened polymethylmethacrylate has been investigated over a wide range of test speeds, encompassing impact conditions. When the entanglement density of the matrix was increased and its glass transition temperature reduced by copolymerization, there were significant increases in the crack initiation and propagation resistance of the particle-toughened materials at low to intermediate speeds. At impact speeds, on the other hand, where crazing became the dominant matrix microdeformation mechanism in all the materials investigated, the fracture response of the copolymer matrix was closer to that of the polymethylmethacrylate homopolymer, and the toughening effect of the rubber particles was no longer effective in either case. This is discussed in terms of the onset of the matrix β transition, associated with the transition from shear to crazing, and the α transition of the rubber domains, both of which occurred in the temperature range immediately below room temperature in low frequency dynamic torsion measurements.

Fracture resistance of mineral reinforced polyamide 6

Tensile tests have been carried out over a wide range of test speeds on compact tension specimens of polyamide 6 containing spherical silica particles, whose size and content had been adjusted to give optimum impact performance in conventional impact tests after conditioning at 50% relative humidity. The tensile test results confirmed there to be a significant improvement in the high speed crack initiation resistance at room temperature and at high moisture contents on addition of the silica particles. However, at low moisture contents and/or temperatures well below the glass transition temperature, the crack initiation resistance was reduced. It is hence inferred that for the chosen silica particle distribution, toughening requires a certain minimum level of matrix ductility in order to be effective.

Essential work of fracture of polypropylene and polypropylene blends over a wide range of test speeds

AbstractThe mechanical properties of extruded films of isotactic polypropylene (iPP) and ethylene‐propylene rubber toughened iPP (iPP/EPR) have been analyzed in terms of the specific essential and non‐essential work of fracture using high speed tensile test apparatus modified for quasi‐static testing in the range 0.0001 to 3 ms−1. Three iPP/EPR grades with modifier contents of 15, 21 and 30 vol% were investigated. As the deformation rate increased, relatively uniform necking of the whole ligament and extensive plastic deformation were progressively replaced by more localized plastic deformation in the blends, and by fully brittle fracture in the unmodified iPP. The non‐essential work of fracture and the total fracture energy were highly sensitive to these changes in deformation mechanism. However, the essential work of fracture, although dependent on the test speed, was less correlated with the extent of global plasticity.

Effects of surface-topography directionality and lubrication condition on frictional behaviour during plastic deformation

Surface-topography, friction and plasticity form a complex system at the interface of a plastic deformation operation. Surface-topography before deformation affects the frictional behaviour at the interface, which in turn affects the level and distribution of plastic deformation. The surface-topography after deformation operations is determined by a combination of the initial surface-topography, the frictional behaviour at the interface and the level and distribution of the plastic deformation. Friction testing with the asymmetric friction upsetting (AFU) test machine and subsequent surface-topography analysis help to further clarify the relationship between surface-topography, interface friction and plasticity. The frictional conditions during testing are controlled via lubricant viscosity, film thickness, surface roughness, and deformation velocity. High and low viscosity lubricants are used in conjunction with a range of test speeds to produce frictional conditions in the boundary, mixed and hydrodynamic lubrication regimes. The effect of initial surface-topography was examined by preparing five different initial specimen surfaces and recording the surface-topographies before testing. Five surface conditions were used: as received, etched, coarse ground perpendicular to test direction, coarse ground parallel to test direction and polished. A correlation between surface-topography directionality and frictional resistance has previously been observed by testing specimens with grooves machined into the surface at a range of angles [A newly developed test method for characterization of frictional conditions in metal forming, in: Proceedings of the Eighth International Conference on Metal Forming, Krakow, 2000, pp. 91–97; Steel Res. 69 (1998) (4–5) 154–160; Beurteilung des Schmierungsverhaltens unterschiedlich texturierter Oberflächen mit Hilfe des Streifenziehversuches, Diplomarbeit Universität, Gesamthochschule Duisburg, 1996]. In the current work coarse grinding is used in place of machined grooves. The scale of the effect from the surface-topography directionality is compared to the scale of the effect of lubricants, arithmetic roughness value and friction regime. Results indicate that arithmetic roughness value and lubrication regime have greater influence than directionality. These results can be explained via the application of lubrication regime theory and the importance of each component in determining the lubrication condition.

Cohesive zone modelling of crack growth in polymers Part 1 –Experimental measurement of cohesive law

The initiation, evolution, and breakdown of the craze ahead of the crack tip is known to control the onset of slow crack growth in polyethylene. Extensive craze zones and large specimen deformations in tough polymers render conventional fracture mechanics approaches incapable of achieving a valid toughness characterisation for these materials. This paper describes a novel experimental method for measuring the local work of separation in tough polyethylene, using tensile specimens with deep circumferential notches, which provide a high level of constraint. The traction–separation behaviour of the material within the constrained ligament is measured directly in situ, yielding a rate dependent cohesive law, which is believed to provide a physically based material description of the damage zone that precedes crack growth. Measurements indicate that both the local work of separation and the cohesive strength are strongly rate dependent, allowing quantification of the fracture behaviour over a wide range of test speeds and discrimination between the stress crack performances of different grades of polyethylene.

Application of the essential work of fracture concept to high temperature deformation in polyoxymethylene

AbstractEssential Work of Fracture (EWF) tests have been carried out on double edge notched samples machined from injection molded sheets of commercial grades of polyoxymethylene homopolymer with different molecular weight averages. Most of the measurements were made at 1000C and over a range of test speeds in which polyoxymethylene is anticipated to undergo a macroscopic ductile‐brittle transition with decreasing strain rate. The results reflect both the existence and the molecular weight dependence of this transition, and are argued to be valid in terms of the European Structural Integrity Society's EWF draft test protocol under certain test conditions. However, it is shown that the applicability of the test method used here becomes highly questionable for test speeds in the immediate vicinity of the transition, owing to the influence of the initial ligament length on the crack tip deformation mechanisms.

Influence of the loading rate on the fracture resistance of isotactic polypropylene and impact modified isotactic polypropylene

The fracture behaviour of an isotactic polypropylene and an impact modified isotactic polypropylene containing 15 wt% of ethylene–propylene rubber has been investigated at test speeds of between 0.1 mm/s and 14 m/s, using compact-tension specimens. The homopolymer displayed a ductile–brittle transition as the test speed was increased, which was associated with a transition from shear deformation to crazing. Deformation of the modified polypropylene was characterized by stable crack propagation over the whole range of test speeds, stress-whitening at the crack tip and, at lower speeds, by the formation of extensive shear lips on the fracture surfaces. An observed increase in the size of the crack tip damage zone with test speed suggested a transition from plane stress to plane strain conditions. This is discussed in terms of a simple model, which takes into account the variation of the sample stress state as the test speed increases.

The temperature and strain‐rate dependence of mechanical properties in polyoxymethylene

AbstractThe computer aided design approach used in current applications of semicrystalline polyoxymethylene (POM) requires high strain‐rate mechanical data. The primary aim of this work has been to measure the room temperature modulus and tensile strength of injection molded samples of POM of different molecular weights at cross‐head speeds of between 10−5 ms−1. We observe no major transition in bulk mechanical behavior in this range of test speeds, the Young's modulus E, in particular, showing little strain rate dependence. This is rationalized on the basis of tensile tests over a range of temperatures, these indicating room temperature to correspond to the plateau in the E(T) curves (Tg for these materials is taken to be −70°C, and the DSC melting onset occurs at ∼ 170°C).The tensile strength increases as ∼log(dϵ/dt) and the behavior is found to be highly nonlinear, strains to fail of the order of 1 being observed even at the highest strain rates, depending on the molecular weight. It is believed that the yield stress of th crystalline regions determines the tensile strength above Tg, the higher degree of crystallinity associated with lower molecular weights resulting in a slightly higher tensile strength. Nevertheless, failure is qualitatively brittle, with no necking and relatively little permanent deformation. This behavior is discussed in terms of morphological investigations of the fractured samples by optical and scanning electron microscopy (SEM).In attempting to relate ultimate failure to the molecular/crystalline structure of the samples, measurements of the critical stress intensity for crack initiation in mode I opening, KIC, as a function of crystallization temperature Tc have been carried out using compact tension specimens machined from injection molded and compression molded plaques. KIC increases with molecular weight and decreases with Tc at low test speeds (in spite of an increase in crystallinity with Tc). This is accounted for in terms of a crack shielding model for crack initiation and of molecular rearrangements occurring during crystallization which lead to a decrease in the effective entanglement density with Tc. The implications of this model are then compared with KIC results over a range of cross‐head speeds and temperatures.

Passing through critical speeds by changing the control gain of magnetic bearings.

In order to pass through critical speeds of the free-free mode of a flexible rotor, a method of changing the control gain of magnetic bearings depending on rotational speed is proposed in this paper. Some preliminary tests are done by applying this method to a rigid rotor. Two critical speeds of rigid mode are passed through by changing the control gain of rigidity depending on rotational speed even without the controller damping effect. The maximum amplitude can be maintained at less than 10μm within the whole range of test speeds.