scholarly journals Analysis of Power Spinning of Cones

1960 ◽  
Vol 82 (3) ◽  
pp. 231-244 ◽  
Author(s):  
B. Avitzur ◽  
C. T. Yang

The geometry of the cone, the roller, and the spinning operation are described mathematically. A shear type of deformation is postulated, based on experimental evidence. The displacement, velocity, strain rate, and stress fields are computed for “Mises’ material,” and hence with Mises’ stress-strain rate law. The power consumed in the operation is computed from the strain rate and stress fields. The expression for the power is in a form that can scarcely be solved analytically. A numerical solution is therefore employed and results are presented in graphical forms, where the power and tangential force are plotted for a variety of the process variables. The numerical solution is compared with actual power and force measurement in experimental tests and the agreement is reasonably good.

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 249
Author(s):  
Przemysław Rumianek ◽  
Tomasz Dobosz ◽  
Radosław Nowak ◽  
Piotr Dziewit ◽  
Andrzej Aromiński

Closed-cell expanded polypropylene (EPP) foam is commonly used in car bumpers for the purpose of absorbing energy impacts. Characterization of the foam’s mechanical properties at varying strain rates is essential for selecting the proper material used as a protective structure in dynamic loading application. The aim of the study was to investigate the influence of loading strain rate, material density, and microstructure on compressive strength and energy absorption capacity for closed-cell polymeric foams. We performed quasi-static compressive strength tests with strain rates in the range of 0.2 to 25 mm/s, using a hydraulically controlled material testing system (MTS) for different foam densities in the range 20 g/dm3 to 220 g/dm3. The above tests were carried out as numerical simulation using ABAQUS software. The verification of the properties was carried out on the basis of experimental tests and simulations performed using the finite element method. The method of modelling the structure of the tested sample has an impact on the stress values. Experimental tests were performed for various loads and at various initial temperatures of the tested sample. We found that increasing both the strain rate of loading and foam density raised the compressive strength and energy absorption capacity. Increasing the ambient and tested sample temperature caused a decrease in compressive strength and energy absorption capacity. For the same foam density, differences in foam microstructures were causing differences in strength and energy absorption capacity when testing at the same loading strain rate. To sum up, tuning the microstructure of foams could be used to acquire desired global materials properties. Precise material description extends the possibility of using EPP foams in various applications.


1992 ◽  
Vol 59 (3) ◽  
pp. 497-501 ◽  
Author(s):  
H. Cai ◽  
K. T. Faber

There is experimental evidence that stress-induced microcracking near a macrocrack tip enhances the fracture toughness of brittle materials. In considering the interaction of the macrocrack with multiple microcracks using a discrete model, it is essential to use approximation methods in order to keep the amount of the computation to a tractable level. However, when crack distances are small, the results of the approximation methods can be significantly different from the numerical solution based upon the exact formulation. The results obtained by these approximation methods will be compared with the numerical solution to show the applicability ranges in which the errors are acceptably small. The use of results obtained by the approximation methods outside applicability ranges in literature is shown to lead to incorrect conclusions concerning microcrack shielding.


2004 ◽  
pp. 65-89

Abstract This chapter reviews the current technology and examines force application systems, force measurement, strain measurement, important instrument considerations, gripping of test specimens, test diagnostics, and the use of computers for gathering and reducing data. The influence of the machine stiffness on the test results is also described, along with a general assessment of test accuracy, precision, and repeatability of modern equipment. The chapter discusses various types of testing machines and their operations. Emphasis is placed on strain-sensing equipment. The chapter briefly describes load condition factors, such as strain rate, machine rigidity, and various testing modes by load control, speed control, strain control, and strain-rate control. It provides a description of environmental chambers for testing and discusses the processes involved in the force verification of universal testing machines. Specimen geometries and standard tensile tests are also described.


2013 ◽  
Vol 734-737 ◽  
pp. 2460-2464 ◽  
Author(s):  
Cheng Jiang Deng ◽  
Xiao Cong He ◽  
Bao Ying Xing

This paper studied the performance of self-piercing riveting (SPR) of aluminum and copper alloy sheet. The SPR process of two copper alloy sheets was analyzed by experimental tests and finite elements stimulation, and good agreements between the simulations and test results of SPR process were obtained. Two different specimen geometries were adopted in experiment: a lap-shear type specimen and a T type specimen. The influence of combination of different materials on the static strength of SPR joints were studied through the tensile-shear and peeling experiments, and the strength of the SPR joints were evaluated by the force-displacement curves of two type specimens. The failure mechanisms corresponding to the static strength were also discussed. On the other hand, the engineering stress - strain curves of two materials have also been studied roughly. These results could provide designer engineers with some application messages of SPR.


2011 ◽  
Vol 403-408 ◽  
pp. 651-655
Author(s):  
W. Hufenbach ◽  
M. Gude ◽  
R. Protz

This paper concerned with modeling of the strain rate dependent material behavior of 3D-textile composites with simultaneous consideration of production and operational (e.g. pores or fatigue damage) defects. Therefore an additive model in the sense of continuum damage mechanics was introduced. For the model validation extensive experimental tests on glass non-crimp fabrics reinforced epoxy (GF-NCF/EP) composites are performed. The focus is put on the influence of production and fatigue related pre-damage under subsequent highly-dynamic tensile loading. The theoretical studies shows a good coincidence with the experimentally results


Author(s):  
Andrey Biryuk ◽  
Mikhail Drobotenko ◽  
Igor Ryadchikov ◽  
Alexander Svidlov

The problem is to find the optimal shape of the gyrodine rotor and its angular rotation speed that maximizes the angular momentum relative to the axis of rotation at a fixed radius, mass and material of the rotor, taking into account the final strength of the material. The gyrodine rotor is a body of revolution, the thickness of which depends only on the distance r to the axis of rotation, r ∈ [0,R], where R is the radius of the rotor. The rotor surface is defined by rotating the curves z = ±z(r) around the axis. When the rotor is spinning, it undergoes deformation due to centrifugal forces. Normal stress fields appear: radial and annular. Assuming the rotor to be thin, deformations can be described by the functions of the radial displacement of the rotor points u(r). Stress fields can be expressed in terms of this function. The functions u(r) and z(r) are related by the equation of the elastically deformed state. This equation is supplied with the boundary conditions for the absence of radial stresses at r = R and the condition for the absence of displacement on the axis of rotation u(0) = 0. Using the numerical solution of the equation, the problem is solved for the class of conical rotors z(r) = a + br with two parameters a and b. The numerical method is used due to the fact that even in this relatively simple case the problem cannot be solved analytically. Several integrable cases are used to analyze the calculation error in the numerical solution of the problem. The dependence of the problem on the Poisson ratio μ ∈ (−1.1) is investigated, with the remaining parameters fixed. The gain in the angular momentum relative to a rotor of constant thickness is compared. The optimal steel conical rotor (μ = 0.3) is 2.068 times thicker at the center than at the edge. Its advantage in the angular momentum over the rotor of constant thickness is 3.2 %.


Author(s):  
Jean-Robert Tyran ◽  
Alexander K. Wagner

Standard economic reasoning assumes that people vote instrumentally—i.e., that the sole motivation to vote is to influence the outcome of an election. In contrast, voting is expressive if voters derive utility from the very act of expressing support for one of the options by voting for it, and this utility is independent of whether the vote affects the outcome. This chapter surveys experimental tests of expressive voting with a particular focus on the low-cost theory of expressive voting. The evidence for the low-cost theory of expressive voting is mixed.


Author(s):  
Vivek Ramadoss ◽  
Nathan Crane

Electrowetting systems are commonly studied by measuring contact angle changes with applied voltage. However many applications such as digital droplet manipulation require information about the force applied to a drop to improve performance. This paper analyses a previously demonstrated method of measuring the electrowetting forces to estimate the sensitivity of force measurements to potential errors such as droplet evaporation, variation in volume, and alignment accuracy. The most significant force errors are introduced by uncertainty in droplet volume as by evaporation. However, analysis shows that this can be controlled by lowering the measurement tip to compensate for evaporation. Errors in tangential force due to alignment are shown to be small for alignment errors below 1°.


Sign in / Sign up

Export Citation Format

Share Document