Robust knockdown factors for the design of axially loaded cylindrical and conical composite shells – Development and Validation

Wagner, H.N.R.; Hühne, Christian; Niemann, Steffen

doi:10.1016/j.compstruct.2017.02.031

Cited by 69 publications

(27 citation statements)

References 39 publications

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“…Definisane preporuke date su u formi krivih koje pokazuju zavisnost redukcionog faktora i odnosa poluprečnika ljuske i debljine (R/t). Na slici 10 prikazane su preporuke za redukcioni faktor prema NASA SP-8007 [14], modifikovane krive u zavisnosti od odnosa dužine i poluprečnika ljuske TH -L/R=5 prema Wagner-u [18], eksperimentalni rezultati prema Flügge-u i rezultati sopstvene numeričke analize. Modifikovana kriva TH -L/R=5 prema Wagner-u [18] obuhvatila je zajednički uticaj imperfekcija u opterećenju i geometrijskih imperfekcija (SBPAsingle boundary perturbation approach), i za odnos dužine i poluprečnika ljuske L/R=5 definiše značajno niže vrednosti redukcionog faktora (KDF) od preporuka datih u NASA SP-8007 [14].…”

Section: Comparison Of the Obtained Results With Design Recommendatiounclassified

“…Na slici 10 prikazane su preporuke za redukcioni faktor prema NASA SP-8007 [14], modifikovane krive u zavisnosti od odnosa dužine i poluprečnika ljuske TH -L/R=5 prema Wagner-u [18], eksperimentalni rezultati prema Flügge-u i rezultati sopstvene numeričke analize. Modifikovana kriva TH -L/R=5 prema Wagner-u [18] obuhvatila je zajednički uticaj imperfekcija u opterećenju i geometrijskih imperfekcija (SBPAsingle boundary perturbation approach), i za odnos dužine i poluprečnika ljuske L/R=5 definiše značajno niže vrednosti redukcionog faktora (KDF) od preporuka datih u NASA SP-8007 [14]. Figure 10 shows comparisons of numerical analysis results for a cylindrical shell of 10,0 mm thick of carbon and stainless steel given in Figure 5 (with geometric imperfections from 1,0 mm to 10,0 mm), with the currently developed empirical recommendations for the knockdown factor (KDF).…”

Section: Comparison Of the Obtained Results With Design Recommendatiounclassified

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Behaviour of thin-walled cylindrical and conical shells: Carbon vs. stainless steel

Vranešević¹,

Gluhović²,

Dobrić³

et al. 2019

Građ materijali i konstrukcije

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Section: Comparison Of the Obtained Results With Design Recommendatiounclassified

Behaviour of thin-walled cylindrical and conical shells: Carbon vs. stainless steel

Vranešević¹,

Gluhović²,

Dobrić³

et al. 2019

Građ materijali i konstrukcije

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“…High quality shells may not suffer from snap-through buckling and a method which allows the quantification of the pre-snap-through imperfection sensitivity was developed by Wagner et al [20]. The single-perturbation displacement approach (SDPA) [50] relies on displacement controlled indentations to approximate the limit load for snap-through buckling as shown in Fig. 5 (middle left).…”

Section: Stacking Sequencementioning

confidence: 99%

“…This method can also be used to study the imperfection sensitivity of composite shells which was shown extensively in [49]. Studies in [50] show that the SBPA delivers robust (conservative with respect to experimental results) lower-bounds for composite shells which lead to a new design load bound for thin-walled composite cylinders which is given by equation (1):…”

Section: Introductionmentioning

confidence: 99%

Decision tree-based machine learning to optimize the laminate stacking of composite cylinders for maximum buckling load and minimum imperfection sensitivity

Wagner

Köke

Dähne

et al. 2019

Composite Structures

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Köke, H.; Dähne, S.; Hühne, C.; Niemann, S.; Khakimova, R. Decision tree-based machine learning to optimize the laminate stacking of composite cylinders for maximum buckling load and minimum imperfection sensitivity, Composite Structures AbstractLaunch-vehicle primary structures like cylindrical shells are increasingly being built as monolithic composite and sandwich composite shells. These imperfection sensitive shells are subjected to axial compression due to the weight of the upper structural elements and tend to buckle under axial compression. In the case of composite shells the buckling load and imperfection sensitivity depend on the laminate stacking sequence.Within this paper multi-objective optimizations for the laminate stacking sequence of composite cylinder under axial compression are performed. The optimization is based on different geometric imperfection types and a brute force approach for three different ply angles. Decision tree-based machine learning is applied to derive general design recommendations which lead to maximum buckling load and a minimum imperfection sensitivity.The design recommendation are based on the relative membrane, bending, in-plane shear and twisting stiffnesses. Several optimal laminate stacking sequences are generated and compared with similar laminate configurations from literature. The results show that the design recommendations of this article lead to high-performance cylinders which outperform comparable composite shells considerably. The results of this article may be the basis for future lightweight design of sandwich and monolithic composite cylinders of modern launch-vehicle primary structures. t Wall thickness of cylindrical shells tply Ply thickness u Axial shortening  Ply angle  Ply angle  Ply angle  knockdown factor Wilkins [1975]

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“…The imperfection sensitivity exhibited by cylindrical shells renders particular emphasis on their design against instability in axial compression. Therefore, robust design approaches are being developed and validated, such as single perturbation load, single perturbation displacement, single boundary perturbation approaches, and their modifications (see, e.g., [1][2][3][4][5][6][7]) in order to replace the existing overconservative design guidelines.…”

Section: Introductionmentioning

confidence: 99%

Applicability of the Vibration Correlation Technique for Estimation of the Buckling Load in Axial Compression of Cylindrical Isotropic Shells with and without Circular Cutouts

Skuķis

Ozoliņš

Andersons

et al. 2017

Shock and Vibration

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Applicability of the vibration correlation technique (VCT) for nondestructive evaluation of the axial buckling load is considered. Thin-walled cylindrical shells with and without circular cutouts have been produced by adhesive overlap bonding from a sheet of aluminium alloy. Both mid-surface and bond-line imperfections of initial shell geometry have been characterized by a laser scanner. Vibration response of shells under axial compression has been monitored to experimentally determine the variation of the first eigenfrequency as a function of applied load. It is demonstrated that VCT provides reliable estimate of buckling load when structure has been loaded up to at least 60% of the critical load. This applies to uncut structures where global failure mode is governing collapse of the structure. By contrast, a local buckling in the vicinity of a cutout could not be predicted by VCT means. Nevertheless, it has been demonstrated that certain reinforcement around cutout may enable the global failure mode and corresponding reliability of VCT estimation.

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Robust knockdown factors for the design of axially loaded cylindrical and conical composite shells – Development and Validation

Cited by 69 publications

References 39 publications

Behaviour of thin-walled cylindrical and conical shells: Carbon vs. stainless steel

Behaviour of thin-walled cylindrical and conical shells: Carbon vs. stainless steel

Decision tree-based machine learning to optimize the laminate stacking of composite cylinders for maximum buckling load and minimum imperfection sensitivity

Applicability of the Vibration Correlation Technique for Estimation of the Buckling Load in Axial Compression of Cylindrical Isotropic Shells with and without Circular Cutouts

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