Elastic-plastic response of a sandwich cylinder subjected to internal pressure

1971 ◽  
Vol 6 (4) ◽  
pp. 273-278 ◽  
Author(s):  
H F Muensterer ◽  
F P J Rimrott

The propagation of plastic zones in a thin-walled sandwich-type cylinder has been analysed theoretically. Boundary conditions are clamped-clamped at both ends, i.e. no rotation is permitted. The material was assumed to behave isotropically and to obey the yieid criterion of Huber-Hencky-von Mises. Deformation was computed on the assumption that the vector of rate of strain was normal to the plastic-interaction curve. The predicted result was verified experimentally. Four specimens were built by lamination of a hexcell core between two concentric cylinders. In the two mild-steel specimens, the initial stage of plastic flow conformed well with the prediction. This proved that plastic flow is not initiated at the mid-position between the end constraints. In two aluminium specimens, this phenomenon of incipient plastic flow could not be observed owing to the absence of a pronounced yield point. The overall agreement was, however, satisfactory.

In previous work, stress-strain curves for the atomic lattice of certain metals have been obtained from X-ray diffraction measurements of the lattice dimensions of test specimens under tension or compression, and it has been shown that when the external yield stress is exceeded, there is a systematic departure from Hooke’s Law. It is pointed out in the present paper that this departure indicates that the external applied stress above the yield is no longer balanced primarily by simple displacement of the atoms but also by a new type of secondary internal stress brought about by the process of plastic flow; and that this secondary stress, being of a permanent nature, can be measured by the residual lattice strains exhibited by the lattice after removal of the external stress. These residual strains are measured in various directions to the stress direction for mild steel subjected to tension, and it is shown that the lattice after tension exhibits a longitudinal compression and a transverse expansion in the ratio of 2:1, which means that the density of the material is thereby kept constant. Comparisons of X-ray and mechanical measurements further show that the hysteresis loop exhibited by the external stress-strain curve of mild steel after overstrain can disappear and the linear elastic relation be recovered without any corresponding change in the internal stress, which is therefore a more fundamental physical property. It is also shown that when the elastic range is extended by overstrain in tension, there is no symmetrical increase in the elastic range in subsequent compression, thus confirming the existence and direction of the secondary internal stress. Finally, the lattice stress-strain curves are also obtained for a 0.4 % C steel (partially pearlitic) and a 0.8 % C steel (pearlitic), and by comparison with the results on pure iron and 0.1 % C steel (annealed) it is shown that the maximum residual internal strain developed by the lattice increases markedly with the fineness to which the crystallites can be broken down by the plastic deformation.


In certain problems of plastic flow, for example, a thick tube expanded by internal pressure, it is important to consider changes in the elastic strain of material which is flowing plastically in order to deduce the correct stress distribution and deformation. The usual plastic theory which neglects elastic strains in the plastic region may lead to considerable errors in certain cases. In this paper we review the theory of the deformation of a material under combined stresses which involves both elastic and plastic components of strain. The relationship between stress and strain is represented on a plane diagram, the reduced stress-strain diagram, which facilitates discrimination between the elastic and plastic components of strain and aids considerably the solution of certain problems. The diagram can also be used to express the relationships governing the dissipation of energy during plastic flow under combined stresses. The theory is applied to the deformation of a long thick tube under internal pressure with zero longitudinal extension. The solution is compared with that based on the usual theory which neglects elastic strains in the plastic region, revealing an error which reaches a maxi­mum of over 60% in the longitudinal stress distribution. The significance of the differences between the two solutions is discussed in detail.


Author(s):  
Lasinta Ari Nendra Wibawa

Crane is one of the heavy equipment that is widely used in the industry. The crane functions as a tool for lifting heavy loads and moving them from one place to another vertically and horizontally. In the LAPAN Garut office, it is used for the rocket assembly process. The study investigates the design and analysis of von Mises stress of crane structure with a capacity of 10 tons using mild steel material. The investigation was carried out numerically using Autodesk Inventor Professional 2017. The simulation results showed the Crane structure had a von Mises stress, deformation, mass, and safety factor respectively 63.73 MPa; 2,173 mm; 1.508,53 kg; and 3.25.Keywords: autodesk inventor 2017; finite element method; mild steel; stress analysis; von Mises stressABSTRAKCrane merupakan salah satu alat berat yang banyak digunakan dalam suatu industri. Crane berfungsi sebagai alat untuk mengangkat beban berat dan memindahkannya dari satu tempat ke tempat lain secara vertikal maupun horisontal. Di LAPAN Garut, Crane digunakan untuk proses perakitan roket. Penelitian ini meneliti tentang perancangan dan analisis tegangan von Mises struktur Crane dengan kapasitas 10 Ton menggunakan material mild steel. Analisis dilakukan secara numerik dengan menggunakan perangkat lunak Autodesk Inventor Professional 2017. Hasil simulasi menunjukkan struktur Crane memiliki tegangan von Mises, deformasi, massa, dan factor keamanan berturut-turut sebesar 63,73 MPa; 2,173 mm; 1.508,53 kg; dan 3,25.


1973 ◽  
Vol 95 (4) ◽  
pp. 219-223 ◽  
Author(s):  
D. M. Woo

A numerical solution for analysis of the bulging process of a thin-walled tube under internal pressure and axial force is proposed. The solution is applied to a case in which the longitudinal stress resulted from internal pressure and external compressive load is tensile along the whole length of the bulged tube. To verify whether the solution is applicable, theoretical and experimental results on the bulging of copper tubes have been obtained and are compared in this paper.


1976 ◽  
Vol 8 (2) ◽  
pp. 123-129 ◽  
Author(s):  
N. A. Makhutov ◽  
L. I. Gladshtein ◽  
Yu. M. Grachev

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