Investigation on the Structure Strength and Stability of Ring Stiffened Cylindrical Shell With Long Compartment and Large Stiffener

2017 ◽  
Author(s):  
Yan Feng ◽  
Hui Li ◽  
Chenfeng Li ◽  
Junjie Ruan ◽  
Qiyou Zhang ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Shell Structure ◽  
Failure Modes ◽  
High Strength Steels ◽  
High Strength ◽  
Theoretical Method ◽  
Utilization Efficiency ◽  
Stiffened Cylindrical Shell ◽  
Vessel Structure ◽  
Current Design

With the increasing status of the sea, the research and manufacture of submersible vessel will be paid more attention. In order to enlarge the submergence depth and utilization efficiency of submersible vessel space, long compartment structures of high strength steels and in various forms are widely adopted. The strength problem of such structure is easy to be guaranteed, while the resulting stability problem is becoming more and more serious. For a ring-stiffened cylindrical shell structure with long compartment, one or two large stiffeners are used on the shell structure to ensure its overall stability. This paper studies the strength and stability of the long compartment cylindrical shell structure, with a special emphasis on the stability problems of overall long compartment structures and large stiffeners. The failure modes and critical load under deep water are analyzed by a theoretical method and also a finite element method. The formula for calculating the large stiffener of submersible vessel structure is derived based on the theory of elastic mechanics, and the defect and deficiency of the formula used in the current design specification is pointed out. The influence of large stiffener position and structure form on the critical pressure of submersible cylindrical shell structure is studied. The results of theoretical analysis and numerical simulation are also compared and discussed.

Probability Analysis of Critical Load of Sphere-Cylinder Combined Shell Structures

2016 ◽  
Author(s):  
Weijun Xu ◽  
Yan Feng ◽  
Xiaotian Wang
Keyword(s):  
Cylindrical Shell ◽  
Critical Load ◽  
Shell Structure ◽  
Failure Modes ◽  
Simulation Method ◽  
Probability Analysis ◽  
Shell Structures ◽  
Probability Models ◽  
Stiffened Cylindrical Shell ◽  
Spherical Structures

The critical load of submersible structures is normally analyzed in deterministic method. However, some factors including structural sizes, material properties and the location of the components, etc., have random characteristics due to smelting and construction process. In other words, the critical load of submersible structures has uncertainty, so these parameters should be considered as random variables. In terms of sphere-cylinder combined shell structures, the critical loads on the cylindrical shell and spherical structures should be considered together to avoid the influence of boundary conditions on the analysis results. This paper focuses on the probability analysis of sphere-cylinder combined shell structures under critical load. According to the GJB calculation method of submarine design, the security calibration ranges of ring-stiffened cylindrical shell and spherical shell are determined, and seven kinds of failure modes of sphere-cylinder combined shell structure are supposed. The corresponding probability models of sphere-cylinder combined shell structure have been established, and the reliability calculations of each failure mode are conducted in FOSM method, JC method and Monte Carlo simulation method. Considering the correlation between different failure modes, reliability series model of sphere-cylinder combined shell structure is applied in the probability analysis. It is verified by comparison of ring-stiffened cylindrical shell and sphere-cylinder combined shell, with the increase of the structure components, the reliability of structure system shows a decline tendency.

scholarly journals An enhancement of the current design concepts for the improved consideration of residual stresses in fatigue-loaded welds

2021 ◽  
Vol 65 (4) ◽  
pp. 643-651
Author(s):  
Th. Nitschke-Pagel ◽  
J. Hensel
Keyword(s):  
Residual Stresses ◽  
State Of The Art ◽  
High Strength Steels ◽  
High Strength ◽  
Design Tools ◽  
Design Concepts ◽  
Treatment Processes ◽  
Real Distribution ◽  
Current Design ◽  
Reliable Knowledge

AbstractThe consideration of residual stresses in fatigue-loaded welds is currently done only qualitatively without reliable knowledge about their real distribution, amount and prefix. Therefore, the tools which enable a more or less unsafe consideration in design concepts are mainly based on unsafe experiences and doubtful assumptions. Since the use of explicitly determined residual stresses outside the welding community is state of the art, the target of the presented paper is to show a practicable way for an enhanced consideration of residual stresses in the current design tools. This is not only limited on residual stresses induced by welding, but also on post-weld treatment processes like HFMI or shot peening. Results of extended experiments with longitudinal fillet welds and butt welds of low and high strength steels evidently show that an improved use of residual stresses in fatigue strength approximation enables a better evaluation of peening processes as well as of material adjusted welding procedures or post-weld stress relief treatments. The concept shows that it is generally possible to overcome the existing extremely conservative but although unsafe rules and regulations and may also enable the improved use of high strength steels.

scholarly journals Study on the Coupling Frequency of Double-Sided Submerged Ring-Stiffened Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Anbin Yu ◽  
Yinglong Zhao ◽  
Youqian Wang ◽  
Ben Zhang
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Hydrostatic Pressure ◽  
Water Immersion ◽  
Theoretical Method ◽  
Coupling Model ◽  
Acoustic Vibration ◽  
Stiffened Cylindrical Shell ◽  
Calculation Results ◽  
Coupling Frequency

Based on the Flügge theory and orthotropic theory, the acoustic vibration coupling model of ring-stiffened cylindrical shell is established by using the wave propagation method and virtual source method. And the effects of water immersion on both sides, free surface, and hydrostatic pressure on the cylindrical shell are considered in the coupling model. Muller three-point iterative method is used to solve the coupling frequency. The calculation results of degradation theory are compared with COMSOL’s calculation results and experimental results, respectively, which verifies the reliability of the theoretical method. Finally, the influence of fluid load, ring rib parameters, boundary conditions, hydrostatic pressure, and free surface on the coupled vibration of ring-stiffened cylindrical shell is analyzed by an example.

Dissimilar Material Joint Strength and Structure for Friction Stir Forming Process

2014 ◽  
Author(s):  
Kenneth A. Ogata ◽  
Sladjan Lazarevic ◽  
Scott F. Miller
Keyword(s):  
Failure Modes ◽  
Dissimilar Materials ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Process ◽  
Experimental Conditions ◽  
Friction Stir ◽  
Automotive Body ◽  
Neck Fracture ◽  
Ultra High Strength Steels

Mass reduction of automotive body structures is a critical part of achieving reduced CO2 emissions in the automotive industry. There has been significant work on the application of ultra high strength steels and aluminum alloys. However, the next paradigm is the integrated use of both materials, which creates the need to join them together. Friction stir forming is a new environmentally benign manufacturing process for joining dissimilar materials. The concept of this process is stir heating one material and forming it into a mechanical interlocking joint with the second material. In this research the process was experimentally analyzed in a computer numerical controlled machining center between aluminum and steel work pieces. The significant process parameters were identified and their optimized settings for the current experimental conditions defined using a design of experiments methodology. Three failure modes were identified (neck fracture, aluminum sheet peeling, and bonding delamination i.e. braze fracture). The overall joint structure and grain microstructure were mapped along different stages of the friction stir forming process. Two layers were formed within the aluminum, the thermo-mechanical affected zone that had been deformed due to the contact pressure and angular momentum of the tool, and the heat affected deformation zone that deformed into the cavity.

scholarly journals Experimental investigation of two-bolt connections for high strength steel members

2018 ◽  
Author(s):  
Yan-Bo Wang ◽  
Yi-Fan Lyu ◽  
Guo-Qiang Li
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
High Strength Steels ◽  
High Strength ◽  
Double Shear ◽  
Loading Direction ◽  
Steel Members ◽  
Edge Distance ◽  
End Distance ◽  
Bolt Spacing

This paper presents an experimental research on bearing-type bolted connections consisting of two bolts positioned perpendicular to the loading direction. A total of 24 connections in double shear fabricated from high strength steels with yield stresses of 677MPa and 825MPa are tested. Two failure modes as tearout failure and splitting failure are observed in experiments. The effect of end distance, edge distance, bolt spacing and steel grade on the failure mode and bearing behavior are discussed. For connection design with bolts positioned perpendicular to loading direction, it is further found that combination of edge distance and bolt spacing effectively determines the failure mode and ultimate load. The test results are compared with Eurocode3. An optimal combination of edge distance and bolt spacing as well as related design suggestion is thus recommended. 

Influence of Microstructure on Damage in Advanced High Strength Steels

2012 ◽  
Vol 706-709 ◽  
pp. 925-930 ◽  
Author(s):  
Frank Hisker ◽  
Richard Thiessen ◽  
Thomas Heller
Keyword(s):  
Work Hardening ◽  
Tensile Testing ◽  
Failure Modes ◽  
Tensile Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
Body Parts ◽  
Hole Expansion ◽  
Advanced High Strength Steels ◽  
Dp Steels

AHSS (Advanced High Strength Steels) combine high strength and good ductility. Their outstanding forming and work-hardening behavior predestines these steels for fabrication of strength relevant structural elements and automobile body parts. To characterize a material, not only tensile, but also hole-expansion and bending behavior are important and help predict the stretch-flange-formability. In this study, detailed analyses of the correlation between these three tests and the damage mechanisms during forming have been performed for selected steels. The results show that for AHSS one should differentiate between “local” and “global” failure. Furthermore, not only are certain materials more sensitive to local or global damage, but also various testing methods tend to provoke either local or global damage. Tensile testing provokes global failure whereas hole-expansion tends to induce local failure. A specimen fails during bending with a mixture of local and global modes. These failure modes are strongly attributed to the microstructure. DP-steels yield high elongation during tensile testing and poorer hole-expansion values. High-resolution EBSD has revealed that the microstructure of DP-steels is sensitive to localized damage, which is compensated by work-hardening around damaged regions and thus shifts the loading to un-hardened regions. This makes DP-microstructures well-suited to tensile loading but sensitive to hole-expansion. CP-steels of comparable strength show poorer tensile elongation and higher hole-expansion ratios due to a microstructure which is not sensitive to localized failure (but has limited capacity for work-hardening). The failure mode in TRIP-steels exhibits a similar character as in DP-steels, but only after the martensitic transformation of retained austenite.

Butt welded connections of high strength steel

2021 ◽  
Author(s):  
Mareike von Arnim ◽  
Jennifer Spiegler ◽  
Ulrike Kuhlmann
Keyword(s):  
High Strength Steel ◽  
High Performance ◽  
High Strength Steels ◽  
High Strength ◽  
Numerical Investigations ◽  
Design Concepts ◽  
Steel Connections ◽  
Load Carrying ◽  
Current Design ◽  
User Friendly

<p>High-performance materials such as high strength steels allow for resource-efficient innovative structures. Therefore, economical and user-friendly design concepts for welded connections of high strength steels are required. Current design rules had been developed mainly for mild steels, e.g. requiring an overmatching of the filler metal. It is not considered, that a soft area which may form in the heat-affected zone of welded high strength steel connections may lead to an overestimation of the load-carrying capacity. Besides, mixed connections as well as under- and overmatching filler metals are not included in the current design codes. Based on a large number of experimental and numerical investigations, a design concept has been developed which takes the characteristics of butt welded high strength steel connections into account. Additionally, experimental and numerical investigations are planned to transfer the new concept of design also to mixed connections.</p>

scholarly journals Experimental study of the mechanical strength and the failure of multi-sheet, multi-material spot-welded assemblies under pure and combined loading conditions

2018 ◽  
Vol 183 ◽  
pp. 02009 ◽  
Author(s):  
Rim Chtourou ◽  
Fahmi Chaari ◽  
Gregory Haugou ◽  
Nicolas Leconte ◽  
Eric Markiewicz ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Failure Modes ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Combined Loading ◽  
Strength Failure ◽  
Shear Modes ◽  
Multiple Materials ◽  
Spot Welded

Resistance Spot Welding (RSW) is widely used in the automotive industry thanks to its production convenience and cost effectiveness. Around four thousands spot welds are indeed employed to assemble the body-in-white. RSW of multiple sheets and combining multiple materials are increasingly realized. The Ultra-High-Strength Steels (UHSS) are particularly well suited for the entire range of structural parts requiring good crash resistance. However, the mechanical strength and the rupture of such new generation of RSW under multi-axial loadings is not yet well studied. The present work investigates the mechanical strength and the failure of a three-sheet spot welded assembly composed of two sheets of UHSS 22MnB5 and a third sheet of mild steel DX54D. An advanced experimental procedure is proposed for testing this assembly in pure and combined (tensile shear modes) modes I/II. Two types of specimen with different sheet thicknesses have been studied. The obtained results are analyzed to investigate the loading angle effect and the assembly configuration effect on the mechanical strength. Failure modes are also studied in relation with the increasing of the loading angle. Finally, the parameters of a macroscopic force-based failure criterion dedicated for FE crash modeling are identified.

Evaluation of Threshold Condition of Interior Annular Crack Growth in Gigacycle Regime

2013 ◽  
Vol 459 ◽  
pp. 65-69 ◽  
Author(s):  
Wei Li ◽  
Ping Wang
Keyword(s):  
Crack Growth ◽  
High Strength Steels ◽  
High Strength ◽  
Theoretical Method ◽  
Fatigue Properties ◽  
Threshold Condition ◽  
Unstable Crack ◽  
Annular Crack ◽  
Small Crack Growth ◽  
Fish Eye

Gigacycle fatigue properties with interior-induced failure of three high strength steels under different loading conditions were investigated, and an experimental-theoretical method is proposed to quantitatively evaluate the threshold condition of interior crack growth. The entire growth process consists of small crack growth within fine granular area (FGA), stable long crack growth outside of FGA within fish-eye and unstable crack growth outside of fish-eye. Based on the comparison between evaluated and experimental results, the validity of method is verified.

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