摘要 :
We consider a nonlinear viscoelastic model of the impact of a body on a stationary Hunt-Crossley obstacle. We obtain the first integral of the equation of motion and determine the coefficient of restitution, the kinetic energy los...
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We consider a nonlinear viscoelastic model of the impact of a body on a stationary Hunt-Crossley obstacle. We obtain the first integral of the equation of motion and determine the coefficient of restitution, the kinetic energy lost at the impact, and their dependence on the impact velocity. We find the solution of the equation of motion of the body in terms of integrals by using the Lambert W-function and present the results of mathematical modeling.
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This paper deals with modeling and analysis of an impact system, which is composed of ball and plane. An impact model considering both duration of impact and energy loss is proposed. The Resultant force due to impact is formulated...
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This paper deals with modeling and analysis of an impact system, which is composed of ball and plane. An impact model considering both duration of impact and energy loss is proposed. The Resultant force due to impact is formulated by introducing a complex stiffness coefficient in Hertz's contact theory. From the expression for the resultant force, the impact system is modeled by both a nonlinear spring and a nonlinear dashpot. The characteristics of the nonlinear spring is expressed by using Hertz's theory, and that of the nonlinear dashpot is expressed by a function of the displace- ment and the velocity. The model parameters are determined by the configuration, the material value and the coefficient of restitution in the impact system. Experimellt and simulation are carried out to demonstrate the accuracy of the proposed model, and good agreement is shown.
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Theoretical and experimental investigations into the loss of the static tensile strength of a KMKU-2M.120. E01 composite after low-speed impacts of different energy have been carried out. All calculations are performed by the meth...
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Theoretical and experimental investigations into the loss of the static tensile strength of a KMKU-2M.120. E01 composite after low-speed impacts of different energy have been carried out. All calculations are performed by the method of finite elements. The drop in the strength as a function of impact energy is estimated according to two criteria: the criterion of an equivalent hole (the upper limit of loss of strength) and the criterion of concentration (the lower limit of loss of strength). The results obtained agree closely with experimental data and therefore can be recognized as reliable.
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Tires in actual service conditions operate on rough roads with a random distribution of obstacles. Rolling resistance, however, is typically measured on smooth surfaces. This paper considers the nature of tire energy loss when imp...
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Tires in actual service conditions operate on rough roads with a random distribution of obstacles. Rolling resistance, however, is typically measured on smooth surfaces. This paper considers the nature of tire energy loss when impacting obstacles. It is demonstrated by a simple example that translational energy can be "lost," even in purely elastic impacts, by trapping energy in structural vibrations that cannot return the energy to translation during the restitution phase of the impact. Tire simulations and experiments demonstrate that this dynamic energy loss can be very large in tires if the impact times are short. Impact times indicating the potential for large energy loss are found to be in the range of normal highway speeds.
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The variable capacity piston pumps are elements of the great power and highest energy efficiency hydrostatic drives. They are used in the drive systems of ship equipment such as deck cranes, steering gears, main propulsion of smal...
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The variable capacity piston pumps are elements of the great power and highest energy efficiency hydrostatic drives. They are used in the drive systems of ship equipment such as deck cranes, steering gears, main propulsion of smaller vessels. The laboratory and simulation investigations of the influence of liquid viscosity on the variable capacitydisplacement pump energy losses have not been so far performed.The paper presents results of the investigations of impact the hydraulic oil viscosity has on the volumetric losses in a piston pump operating in the full range of its capacity andoil pressure.
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摘要 :
Upper bounds on Newton’s, Poisson’s, and energetic coefficients of normal restitution for
the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating
that the upper bound on Newton’s coefficient i...
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Upper bounds on Newton’s, Poisson’s, and energetic coefficients of normal restitution for
the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating
that the upper bound on Newton’s coefficient is smaller than 1, while the upper bound on
Poisson’s coefficient is greater than 1. The upper bound on the energetic coefficient of
restitution, which is a geometric mean of Newton’s and Poisson’s coefficients of normal
restitution, is equal to 1. Lower bound on all three coefficients is equal to zero. The
bounds on the tangential impact coefficient, defined by the ratio of the frictional and
normal impulses, are also derived. Its lower bound is negative, while its upper bound is
equal to the kinetic coefficient of friction. Simplified bounds in the case of a nearly
vertical impact are also derived. DOI: 10.1115/1.3172198
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A purpose-built pendulum machine was used to study the oblique impact and the behaviour of the surface layers of a normalized low alloy steel subjected to the impact of hard α-alumina balls. The effect of relative tangential velo...
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A purpose-built pendulum machine was used to study the oblique impact and the behaviour of the surface layers of a normalized low alloy steel subjected to the impact of hard α-alumina balls. The effect of relative tangential velocity on impulses, restitution coefficient and impact energy loss, was analyzed. The morphology of the impact indentations was characterized and related to the impulses obtained. There was lip formation in the target material with ejection of a small fragile oxidized chip, at a certain critical sliding speed. The impact duration and the impulse ratio have maximum values. These values seem to be related to the critical angle of attack, common in abrasive and erosive ductile processes. The experimental results were compared with some impact models and theories.
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The coefficient of restitution (COR) is an important input parameter in the numerical simulation of granular flows, as it governs the travel distance, the lateral spreading, and the design of barriers. In this study, a new custom-...
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The coefficient of restitution (COR) is an important input parameter in the numerical simulation of granular flows, as it governs the travel distance, the lateral spreading, and the design of barriers. In this study, a new custom-built micromechanical impact loading apparatus is presented along with impact experiments on engineered and natural materials. The COR and energy loss of various grains and base block combinations are studied, including fairly regular-shaped Leighton Buzzard sand (LBS) grains as a natural soil and granite or rubber as base blocks, apart from the use of engineered materials for the grains (chrome steel balls, glass balls) and blocks (stainless steel, brass). The repeatability of the new micromechanical impact loading apparatus was checked by impacting chrome steel balls on stainless steel block. In all the test combinations, the higher and lower values of the COR are found for granite block (ranging between 0.75 and 0.95) and rubber block (ranging between 0.37 and 0.44) combinations, respectively. For the tested grain-block combinations, lower values of COR were observed for impacts between materials of low values ofcomposite Young's modulus. However, within the narrow range ofcomposite surface roughness of the tested grain-block interfaces no particular trend was observed in the COR values. Compared to glass balls and chrome steel balls, greater scatter in the COR values is observed for natural sand grains. This is due to the variation of the elastic and morphological characteristics among individual LBS grains.
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摘要 :
Upper bounds on Newton's, Poissons, and energetic coefficients of normal restitution for the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating that the upper bound on Newton's coefficient is sm...
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Upper bounds on Newton's, Poissons, and energetic coefficients of normal restitution for the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating that the upper bound on Newton's coefficient is smaller than 1, while the upper bound on Poisson's coefficient is greater than 1. The upper bound on the energetic coefficient of restitution, which is a geometric mean of Newton's and Poisson's coefficients of normal restitution, is equal to 1. Lower bound on all three coefficients is equal to zero. The bounds on the tangential impact coefficient, defined by the ratio of the frictional and normal impulses, are also derived. Its lower bound is negative, while its upper bound is equal to the kinetic coefficient of friction. Simplified bounds in the case of a nearly vertical impact are also derived.
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This paper presents an experimental investigation on low velocity impact (LVI) behaviour of flexible bio-composite laminates with different stacking sequence namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ), jute/rubb...
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This paper presents an experimental investigation on low velocity impact (LVI) behaviour of flexible bio-composite laminates with different stacking sequence namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ), jute/rubber/jute/rubber/jute (JRJRJ) and subjected to different impact energy levels using a conical shaped impactor. The performances of the proposed flexible composites are evaluated based on their energy absorption, peak force, coefficient of restitution (CoR), energy loss percentage (ELP) and failure behavior. Results indicated that JRJ provides better energy absorption and JRJRJ provides better damage resistance when subjected to LVI. Microscopic analysis revealed that the flexible composites fail mainly due to the tearing mechanism of the matrix as opposed to cracking in case of conventional stiff composites. It was also found that flexible composites are free from delamination. Compared to conventional stiff composites, there is no catastrophic failure observed in the proposed flexible composite. The overall performance evaluation of these proposed flexible composites indicates that these flexible composites can be potential sacrificial materials such as claddings used to protect primary structural components subjected to LVI. The systematic methodology employed in the present study serves as a benchmark for the effective utilization and selection of flexible composites for LVI applications.
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