Stainless Steel Cylindrical Shell Research Articles

Backscattering enhancements by partially exposed cylindrical shells due to reflected flexural waves at air–water interfaces

For smooth curved objects in contact with a flat interface, the propagation paths of supported surface elastic waves can be altered by the interface, thereby enhancing the characteristics of the backscattered echo returns. In this study, backscattering experiments are conducted on an empty stainless steel cylindrical shell that breaks through an air–water interface and is insonified from below at grazing incidence. The shell has a thickness-to-radius ratio of 5%. The frequencies of interest fall within the vicinity of and below the coincidence frequency, which corresponds to a ka range of 13.8–20.1. The experimental results demonstrate that, for the partially exposed cylindrical shell, the flexural waves can traverse the interface and circumnavigate the shell multiple times. The flexural waves experience mode transitions upon passing through the interface, existing as a0− waves below the interface and a0 waves above the interface. Simultaneously, the flexural waves undergo partial reflection each time they pass through the interface, guiding them to follow a reverse path and generating a periodic series of echo returns, which leads to the enhancement of backscattering. The shift in resonance frequency in relation to the changing exposure is analyzed and predicted using the phase matching theory.

Uncovering the fracture behavior of metallic cylindrical shells under internal explosive loadings via careful design of densely-arranged multi-point photon Doppler velocimetry measurements

While the expanding process of cylindrical shells under internal explosive loadings is fundamental and ubiquitous in engineering applications, the comprehensive understanding of the underlying mechanism is still a challenge due to the limitation of the spatial resolution on the current diagnostic techniques. To address this issue, an improved densely-arranged multi-point photon Doppler velocimetry (DMPDV) technique with enough spatial resolution to capture the local dynamical evolution was carefully designed. The DMPDV technique was then applied to investigate the expanding behavior of an explosively driven 304 L stainless steel cylindrical shell. As a step beyond the coarse understanding of the overall dynamical response, the expanding process can then be demonstrated comprehensively with more exact concentrations on one fragment. By the combination of DMPDV and high-speed photography, we uncovered the evolution of the expanding process which can be divided into three stages: (1) In the beginning, due to the symmetries of the specimen and the loading, the cylinder expands uniformly and all the velocity-time curves at different hoop positions are coincide with each other. (2) after the emergence of cracks at the outer surface of the cylinder, the velocity-time curves start to separate from each other and are regularly arranged according to their test positions. (3) following the penetration of the crack through the thickness of the cylinder, there is a reverse in the velocity-time curves and the fragments begin to rotate, the rotation angle can be estimated using the velocity difference. The hidden mechanism is then revealed with the help of unloading wave theory and rigid body dynamics. Here the second stage is dominated by unloading wave while the last stage is controlled by the denotation products. These experimental results provide deep insight into the detailed fracture behavior of expanding cylindrical shell and are further validated by the Mott wave models as well as numerical simulations, respectively.

Microstructure, Mechanical Properties and Cross‐sectional Behaviour of Additively Manufactured Stainless Steel Cylindrical Shells

AbstractPowder bed fusion (PBF) is an additive manufacturing method that enables complex metallic components to be manufactured with high precision. The microstructure, mechanical properties and cross‐sectional behaviour of PBF additively manufactured stainless steel circular hollow sections are investigated through experiments in this paper, with a view to applications in construction. The experimental programme included tensile coupon tests, microstructural characterisation, initial geometric imperfection measurements and compression tests on PBF 316L stainless steel cylindrical shells with large diameter‐to‐thickness (D/t) ratios. Advanced measurement methods – 3D laser scanning and digital image correlation, were employed to measure the specimen geometries prior to testing and deformation fields during testing, respectively. The possible anisotropy in mechanical properties was examined through tensile coupon tests and correlated with the underlying microstructural and textural features. Compression tests were performed to investigate the resistance against local buckling of thin‐walled cylindrical shells produced by PBF. All cylindrical shells buckled below their yield loads with a chequerboard failure mode and revealed the anticipated trend of reducing capacity relative to the yield load with increasing local slenderness, reflecting the increasing susceptibility to local buckling.

Investigation on the technology of soft recovery of fragment produced by metal cylindrical shell subjected to explosive loading

According to the requirements on the soft recovery of fragments of expanding cylindrical metal shells under explosion loading, this paper presents a recovery device combining low density polyurethane foam and water medium through theoretical analysis and numerical simulation. Compared to traditional recovery device designed with a single material, the combined recovery device can reduce the amplitude of impact pressure, which is produced by the initial interaction of low impedance polyurethane foam with high speed fragments, by about 1/3 compared to the impact pressure produced by water, and maintain the high decay rate of fragment speed. It can also make full use of the advantages of high density of water medium when the fragment speed is less than 0.5 km/s, which can reduce the decay thickness of the recovery device based on single polyurethane foam. Based on the device, the recovery experiment of expansion and fracture of 304 stainless steel cylindrical shell under explosive loading is carried out. Through the measurement of the wall velocity of the recovery tank and the appearance inspection after the experiment, it is implied that the wall and bottom of the recovery tank are in good condition and can be reused. According to the statistics of the recovered fragments, the recovery rate of the fragments is more than 85%, and the internal and external interfaces of fragments are highly recognizable, the turning blade lines on the surface of the fragments are clearly visible, and several non-penetrating cracks are visible, which verified that the impact damage of the recovery device to the fragments is significantly reduced. Acording to the fracture and surface information of the fragments, the approximate position of the fragments in the metal cylindrical shell is inferred.. Finally, the statistical results of the average thickness and mass distribution of the recovered fragments are given.

Buckling of externally pressurized cylindrical shell: A comparison of theoretical and experimental data

This study examined the buckling of unstiffened cylindrical shells under external pressure. Six stainless steel cylindrical shell specimens were tested, with a length-to-radius ratio, L/R, ranging from 1 to 7. The wall thickness, diameter, axial length, and geometry of each specimen and the material properties of the corresponding sheets were measured. All cylindrical specimens were subjected to external pressure in a pressure chamber; the buckling load and final collapsed mode were recorded. This paper presents a comparison among theoretical calculations, finite element (FE) results, and experimental data for externally pressurized cylindrical shells. In the numerical calculations, true geometry, average wall thicknesses, and elastic–perfectly plastic modeling were considered. Deviation between theoretical and FE results was 0%to − 22%, and it increased with the length-to-radius ratio. Experimental results are consistent with FE results, with deviation of 2–9%, and final collapsed modes of all shells are consistent.

Experimental analysis of heat conduction in a high diameter ratio annular gap filled with a rarefied gas

A first experimental attempt has been realized in order to measure the heat transfer between a heated platinum wire having a diameter (d) of 0.15 mm, disposed along the axis of a cylindrical shell in stainless steel having an inner diameter (D) of 100 mm, and air from atmospheric conditions down to 10−3 mbar. Temperature differences between the wire and the external stainless steel cylindrical shell in the range of 50–125 K were imposed and the heat power transferred from the wire to the surround was measured as a function of the gas pressure. The experimental results demonstrates that for an accurate measurement of the heat conduction when the pressure goes down to 0.05 mbar is very important to be able to quantify accurately the radiative contribution which becomes predominant at low pressure. The main limitations of the test rig described in this paper have been analysed in order to highlight the modifications which can be suggested to obtain experimental results comparable with theoretical models.

Containment capsule stresses for encapsulated phase change materials

The encapsulation of a phase change material to store thermal energy is considered here for concentrated solar power systems. The stress distribution in a spherical nickel shell of 250 μ thickness formed around a ball of zinc by the electroless deposition process and a stainless steel cylindrical shell containing zinc are considered. The effect of external forces and imperfections within the shell structure that could affect the deformation are also modeled. The aim of the simulations performed is to establish a suitable thickness for the encapsulating material. It is concluded that while the shell can deform and safely withstand the anticipated expansion of the zinc, the added effects from point loads caused by the weight of the surrounding encapsulated capsules and other possible imperfections in the capsule structure could cause failure. A three-dimensional finite element model is used to establish the stresses in cylinders of different aspect ratio caused by the expansion of zinc as it melts inside of the encapsulation. The amount of void space that must be left inside of the capsule, so that the expansion of the zinc during phase change and the increase in gas pressure inside of the vessel will not cause failure of the shell, is determined from simulations. Results indicate that the cylinder with welded ends could easily contain up to 86% of the initial volume full of zinc with only a very small amount of plastic deformation, less than 0.5% strain, corresponding to an internal pressure of 2.03 MPa.

Neighbourhood effect of two short dents on buckling behaviour of short thin stainless steel cylindrical shells

Generally, thin cylindrical shells are susceptible for geometrical imperfections like non-circularity, non-cylindricity, dents, swellings etc. All these geometrical imperfections decrease the static buckling strength of thin cylindrical shells. In this work, neighbourhood effect of two circumferential short dents on the buckling behaviour of thin short stainless steel cylindrical shell is studied in detail. The dents are modelled on the FE surface of perfect cylindrical shell at half the height of the cylindrical shell by varying the centre distance between the dents. These cylindrical shells are analysed using non linear FE static buckling analysis and their buckling behaviours are compared with that of cylindrical shell with a short circumferential dent. It is found that the effect of two short dents and its nearness effect seem to be negligible compared with the effect of single dent in reducing the buckling strength of cylindrical shell.

Parametric study on buckling behaviour of thin stainless steel cylindrical shells for circular dent dimensional variations under uniform axial compression

It is well known that thin cylindrical shell structures have wide applications as one of the important structural elements in many engineering fields and its load carrying capacity is decided by its buckling strength which in turn predominantly depends on geometrical imperfections present in it. Geometrical imperfections can be classified as local and distributed geometrical imperfections. But in this work, only local geometrical imperfection namely dent is considered for analysis. The main aim of this study is to determine the more influential dimensional parameter out of two dent dimensional parameters, one is the extent of dent present over a surface area and the other is dent depth, which affect the buckling strength of the cylindrical shells drastically. To account for the parameter “extent of dent present over an area”, the dent is considered as circular dent and its amplitude is considered as dent depth. For this purpose, finite element (FE) models of cylindrical shells with a circular dent at half the height of cylindrical shells having different dent sizes are generated. These FE models are analyzed using ANSYS nonlinear buckling analysis. It is concluded that extent of dent present over an area is more influential than dent depth. To verify this conclusion further, FE models of cylindrical shells with two circular dents at half the height of cylindrical shell placed at 180° apart having different dent sizes are generated and analyzed. Keywords: Thin cylindrical shell, Buckling strength, Geometrical imperfections, Dents.

Experimental investigation of bottom target detection by single channel iterative time reversal.

Iterative time reversal process will gradually lead echo waves to converge to a dominant narrowband resonant mode of the target and enhance the return level in noisy and reverberant environment. This technique is used in bottom target detection and an experiment has been performed in the Yellow Sea, China. The experiment is in a monostatic configuration, and the target, which is a 53 cm external diameter and 260 cm long stainless steel cylindrical shell with concrete interior, is resting on the seafloor, and the directional transceiver, which is a transmitter and receiver couple, is located right above the target. First, a broadband interrogation pulse is launched, and the echo is measured and a bandpass filter is applied to avoid transceiver response peak, then the signal is time reversed and retransmitted, and repeat above procedures iteratively. The bottom reverberation will gradually be suppressed, and the center frequency of converged signal corresponds to a target resonance frequency, which is different from inhomogeneous bottom response in no target case. The existence of target is determined by this important acoustic signature, and the results illustrate the feasibility of this method. [Work partially supported by the CAS Innovation Fund.]

Effect of a Dent of Different Sizes and Angles of Inclination on Buckling Strength of a Short Stainless Steel Cylindrical Shell Subjected to Uniform Axial Compression

Generally, thin cylindrical shells are susceptible for geometrical imperfections like non-circularity, non-cylindricity, dents, swellings etc. All these geometrical imperfections decrease the static buckling strength of thin cylindrical shells, but in this paper only effect of a dent on strength of a short (L / D ∼1 and R/t = 280) stainless steel cylindrical shell is considered for analysis. The dent is modeled on the FE surface of perfect cylindrical shell for different angles of inclination and sizes at half the height of cylindrical shell. The cylindrical shells with a dent are analyzed using non-linear static buckling analysis. From the results it is found that in case of shorter dents, size and angle of inclination dents do not have much effect on static buckling strength of thin cylindrical shells, where as in the case of long dents, size and angle of inclination of dents have significant effect. But both short and long dents reduce the static buckling strength drastically.

A Study on the Structural Stress Analysis of the Steel and the GFRP Laminated Composite Cylindrical Shell with a Stiffened Circular Cutout

The strain distribution around the unstiffened and stiffened circular cutout of the isotropic stainless steel (ANSI type 304) and the GFRP laminated composite cylindrical shells subjected to axial compression are studied. The experimental results are obtained and compared with numerical analysis. In experiment, the strain is measured around the circular cutout by strain measuring system under the axial uniform compression loading. The numerical analysis is performed by the commercial finite element code ANSYS. The strain concentration factor (SCF) is defined to investigate the strain concentration around the circular cutout. The SCF of the stainless steel cylindrical shell with a stiffened cutout is decreased 39% in experiment and 50 % in numerical analysis. The SCF of GFRP laminated composite cylindrical shell is decreased 22% in experiment and 31 % in numerical analysis.

Experimental observations of Anderson localization by disorder on a framed fluid-loaded cylinder

The presence of internal structure can greatly alter the acoustic behavior of elastic systems. Many structures of interest are comprised of reinforced shells where a periodic placement of the stiffeners lead to well-known stop- and passbands for the long-range transport of vibrational energy. Various degrees of disorder are typically the norm in real systems and the phenomenon of localization can dominate the structural dynamics and lead to high degrees of apparent damping even for frequencies well inside passbands. Generally speaking, localization can result from a number of physical mechanisms that include: radiation damping, structural damping, local resonances, and Anderson localization. Experiments have been conducted on a 1.02-m-long stainless steel cylindrical shell with 80 ring stiffeners attached with a small degree of irregularity in their placement (on average δz/d is ±2.5). Out-of-plane structural velocities in the midfrequency band were derived by employing nearfield acoustic holography (NAH) for the case of radial point excitation. The experimental evidence of Anderson localization on a fluid-loaded two-dimensional system is reported here for the first time. [Work supported by NRL and ONR.]

Experimental acoustic resonance study on finite length cylindrical targets

The acoustic resonances of cylindrical finite length targets are investigated experimentally. The targets have different length-to-diameter ratios η: η=1.33 for a solid aluminium cylinder, η=1.66 for an aluminium cylindrical shell (with a ratio between the inner radius b and the outer radius a of 0.89), η=1.85 for a stainless steel cylindrical shell ( b a =0.94 ). The insonification is performed at normal or slightly oblique incidence. Resonances related to Whispering Gallery, guided waves and Scholte-Stoneley waves are identified. For a given vibration mode n it is possible to identify two resonances at frequencies close to each other. A comparison is made with theoretical values at normal incidence. The experimental resonances related to Whispering Gallery and guided waves are shifted towards the high frequencies; resonances related to Scholte-Stoneley waves are shifted towards the low frequencies.

Displacement, Resonant Frequencies, and Impedance Characteristics of a Free-End Cylindrical Shell

Dynamic tests were made on an unstiffened stainless steel cylindrical shell, 36 in. long, 12 in. diam and 116 in. shell thickness. The shell had no end plates. It was freely supported such that its end boundary conditions were free free. Resonant frequencies of the inextensional deformation types of modes, and extentional modes were experimentally obtained. Point and transfer impedance values were obtained. Longitudinal and circumferential radial displacement patterns were mapped for all resonant frequencies. Comparison was made to standard theoretical methods.