Evaluation of Localized Necking Models for Fracture Prediction in Punch-Loaded Steel Panels

The ductile fracture of thin-shell structures was studied here using a localized necking model. The punching experiments for unstiffened and stiffened panels were compared with numerical predictions using a combined ductile fracture and localized necking model using shell elements. The plasticity and fracture model parameters of JIS G3131 SPHC steel were identified by performing calibration experiments on standard flat bars, notched tension, central hole tension, plane strain tension, and shear specimens. The plasticity beyond the onset of necking was modeled using the Swift hardening law. The damage indicator framework with a combined Hosford–Coulomb fracture model and the domain of shell-to-solid equivalence (DSSE) were adopted to characterize the fracture initiation. The model parameters were calibrated based on the loading paths to fracture initiation, which were extracted from a non-linear finite element (FE) analysis. The presented HC–DSSE model was validated using punch tests and was able to predict fracture initiation with good accuracy.

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Analysis of Interface Deformation of Steel-Concrete-Steel Sandwich Beam

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.525-526.357 ◽

2012 ◽

Vol 525-526 ◽

pp. 357-360

Author(s):

Pei Xiu Xia ◽

Guang Ping Zou ◽

Zhong Liang Chang

Keyword(s):

Sandwich Beam ◽

Analytical Models ◽

Sandwich Beams ◽

Interface Deformation ◽

Simply Supported ◽

Interface Slip ◽

Steel Panels ◽

Uniformly Distributed Loads ◽

Relationship Of ◽

The Relationship

The effect of the interface slip is neglected in most studies on calculating deflection of sandwich beams. By taking a simply supported sandwich beams under uniformly distributed loads as an example, simplified analytical models of the interface slip are established, and corresponding clculation formulas of interface slip between steel panels and concrete and section curvatures are derived. The formula for deflection of sandwich beams are then presented. This formula reflects the relationship of influence each other between the interface slip and deflection.

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Experimental and Numerical Investigation on the Influence of Process Speed on the Blanking Process

Journal of Manufacturing Science and Engineering ◽

10.1115/1.1445152 ◽

2002 ◽

Vol 124 (2) ◽

pp. 416-419 ◽

Cited By ~ 10

Author(s):

A. M. Goijaerts ◽

L. E. Govaert ◽

F. P. T. Baaijens

Keyword(s):

Stainless Steel ◽

Constitutive Model ◽

Numerical Simulations ◽

Ferritic Stainless Steel ◽

Fracture Criterion ◽

Fracture Initiation ◽

Rate Dependence ◽

Numerical Predictions ◽

Punch Velocity ◽

Blanking Process

In a previous work a numerical tool was presented which accurately predicted both process force and fracture initiation for blanking of a ferritic stainless steel in various blanking geometries. This approach was based on the finite element method, employing a rate-independent elasto-plastic constitutive model combined with a fracture criterion which accounts for the complete loading history. In the present investigation this work is extended with respect to rate-dependence by employing an elasto-viscoplastic constitutive model in combination with the previously postulated fracture criterion for ferritic stainless steel. Numerical predictions are compared to experimental data over a large range of process speeds. The rate-dependence of the process force is significant and accurately captured by the numerical simulations at speeds ranging from 0.001 to 10 mm/s. Both experiments and numerical simulations show no influence of punch velocity on fracture initiation.

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The Effect of Stitching on Compression Behavior of Stiffened Composite Panels

10.1115/imece2001/amd-25416 ◽

2001 ◽

Author(s):

Sung S. Suh ◽

H. Thomas Hahn ◽

Nanlin Han ◽

Jenn-Ming Yang

Keyword(s):

Beneficial Effect ◽

Compression Behavior ◽

Stiffened Panels ◽

Shell Elements ◽

Stitch Density ◽

Stiffened Composite Panels ◽

Out Of Plane ◽

Post Buckling ◽

Post Impact ◽

Good Agreement

Abstract Failure of stiffened panels under compression is preceded by buckling of their skin and hence is affected by the presence of out-of-plane stresses. One of the promising methods of preventing premature delamination is stitching. The present paper discusses the effect of such stitching on compression behavior of blade-stiffened panels that were fabricated from plain weave AS4/3501-6 through resin film infusion process. Kevlar 29 yarn was used at a stitch density of 9.92 stitches per cm2. Some of the panels were damaged by drop-weight impact before compression testing. For comparison purposes unstitched panels with the same materials and dimensions were also tested under the same loading conditions. Stitching resulted in a 10% improvement in strength in the absence of any intentional damage. The beneficial effect of stitching was most obvious when the panels were impacted on a flange: a 50% improvement was observed in post-impact strength. However, stitching could not prevent stiffener from failure when impacted directly. Thus stitching had no beneficial effect when impact occurred on a stiffener. A buckling and post-buckling analysis was carried out using 3-D shell elements on the Abaqus. Predictions were in fairly good agreement with the experimental data.

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IP Paging for Mobile Hosts in Distributed and Fixed Hierarchical Mobile IP

Security, Design, and Architecture for Broadband and Wireless Network Technologies ◽

10.4018/978-1-4666-3902-7.ch012 ◽

2013 ◽

pp. 154-169

Author(s):

Paramesh C. Upadhyay ◽

Sudarshan Tiwari

Keyword(s):

Cellular Networks ◽

Mobile Ip ◽

Performance Evaluations ◽

Mobility Ratio ◽

Analytical Models ◽

Original Form ◽

Mobile Hosts ◽

Micro Mobility ◽

Mobility Protocols ◽

Ip Paging

The concept of Paging has been found useful in existing cellular networks for mobile users with low call-to-mobility ratio (CMR). It is necessary for fast mobility users to minimize the signaling burden on the network. Reduced signaling, also, conserves scarce wireless resources and provides power savings at user terminals. However, Mobile IP (MIP), a base protocol for IP mobility, does not support paging concept in its original form. Several paging schemes and micro-mobility protocols, centralized and distributed, have been proposed in literature to alleviate the inherent limitations of Mobile IP. In this paper, the authors propose three paging schemes for Distributed and Fixed Hierarchical Mobile IP (DFHMIP) and develop analytical models for them. Performance evaluations of these schemes have been carried out and results have been compared with DFHMIP without paging and with Dynamic Hierarchical Mobile IP (DHMIP) for low CMR values.

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IP Paging for Mobile Hosts in Distributed and Fixed Hierarchical Mobile IP

International Journal of Wireless Networks and Broadband Technologies ◽

10.4018/ijwnbt.2011040106 ◽

2011 ◽

Vol 1 (2) ◽

pp. 62-76 ◽

Cited By ~ 1

Author(s):

Paramesh C. Upadhyay ◽

Sudarshan Tiwari

Keyword(s):

Cellular Networks ◽

Mobile Ip ◽

Performance Evaluations ◽

Mobility Ratio ◽

Analytical Models ◽

Mobile Users ◽

Original Form ◽

Mobile Hosts ◽

Mobility Protocols ◽

Ip Paging

The concept of Paging has been found useful in existing cellular networks for mobile users with low call-to-mobility ratio (CMR). It is necessary for fast mobility users to minimize the signaling burden on the network. Reduced signaling, also, conserves scarce wireless resources and provides power savings at user terminals. However, Mobile IP (MIP), a base protocol for IP mobility, does not support paging concept in its original form. Several paging schemes and micro-mobility protocols, centralized and distributed, have been proposed in literature to alleviate the inherent limitations of Mobile IP. In this paper, the authors propose three paging schemes for Distributed and Fixed Hierarchical Mobile IP (DFHMIP) and develop analytical models for them. Performance evaluations of these schemes have been carried out and results have been compared with DFHMIP without paging and with Dynamic Hierarchical Mobile IP (DHMIP) for low CMR values.

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On the Use of Strain Path Independent Metrics and Critical Distance Rule for Predicting Failure of AA7075-O Stretch-Bend Sheets

Materials ◽

10.3390/ma13173660 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3660

Author(s):

Andrés Jesús Martínez-Donaire ◽

Domingo Morales-Palma ◽

Carpóforo Vallellano

Keyword(s):

Equivalent Plastic Strain ◽

Sheet Thickness ◽

Critical Distance ◽

Uniform Strain ◽

Forming Limit ◽

Limit Curve ◽

Proportional Loading ◽

Forming Limit Curve ◽

Stretch Bending ◽

Numerical Predictions

The strain-based forming limit curve is the traditional tool to assess the formability of metal sheets. However, its application should be restricted to proportional loading processes under uniform strain conditions. Several works have focused on overcoming this limitation to characterize the safe process windows in industrial stretch-bend forming processes. In this paper, the use of critical distance rule and two path-independent stress-based metrics are explored to numerically predict failure of AA7075-O stretch-bend sheets with 1.6 mm thickness. Formability limits of the material were experimentally obtained by means of a series of Nakazima and stretch-bending tests at different thickness-over-radius ratios for inducing controlled non-uniform strain distributions across the sheet thickness. By using a 3D calibrated finite element model, the strain-based forming limit curve was numerically transformed into the path-independent stress and equivalent plastic strain polar spaces. The numerical predictions of necking strains in the stretch-bending simulations using the above approaches were successfully compared and critically discussed with the experimental results for different values of the critical distance. It was found that failure was triggered by a critical material volume of around the half thickness, measured from the inner surface, for the both path-independent metrics analyzed.

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An Efficient and General Finite Element Model for Double-Sided Incremental Forming

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4033483 ◽

2016 ◽

Vol 138 (9) ◽

Cited By ~ 11

Author(s):

Newell Moser ◽

David Pritchet ◽

Huaqing Ren ◽

Kornel F. Ehmann ◽

Jian Cao

Keyword(s):

Finite Element ◽

Incremental Forming ◽

Mesh Size ◽

Element Model ◽

Explicit Finite Element ◽

Fully Integrated ◽

Shell Elements ◽

Mass Scaling ◽

Element Simulation ◽

Element Type

Double-sided incremental forming (DSIF) is a subcategory of general incremental sheet forming (ISF), and uses tools above and below a sheet of metal to squeeze and bend the material into freeform geometries. Due to the relatively slow nature of the DSIF process and the necessity to capture through-thickness mechanics, typical finite element simulations require weeks or even months to finish. In this study, an explicit finite element simulation framework was developed in LS-DYNA using fully integrated shell elements in an effort to lower the typical simulation time while still capturing the mechanics of DSIF. The tool speed, mesh size, element type, and amount of mass scaling were each varied in order to achieve a fast simulation with minimal sacrifice regarding accuracy. Using 8 CPUs, the finalized DSIF model simulated a funnel toolpath in just one day. Experimental strains, forces, and overall geometry were used to verify the simulation. While the simulation forces tended to be high, the trends were still well captured by the simulation model. The thickness and in-plane strains were found to be in good agreement with the experiments.

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Ultimate strength formulation of stiffened panels under in-plane compression or tension with cracking damage

Journal of Naval Architecture and Marine Engineering ◽

10.3329/jname.v15i1.31668 ◽

2018 ◽

Vol 15 (1) ◽

pp. 1-16

Author(s):

Mohammad Reza Zareei ◽

Mehdi Iranmanesh

Keyword(s):

Risk Assessment ◽

Regression Analysis ◽

Closed Form ◽

Ultimate Strength ◽

Nonlinear Fem ◽

Stiffened Panels ◽

Plane Compression ◽

Steel Panels ◽

Stiffened Steel

The aim of the present study is to develop closed-form formulations for predicting the ultimate compressive and tensional strength of stiffened steel panels with crack damages. First, a numerical database is generated. This database includes the ultimate strength levels of stiffened steel panels with cracks subjected to axial compressive or tensile loads. It was carried out with a series of nonlinear FEM analyses by varying the size of crack damage. In the following sections, regression analysis is used for deriving the empirical formulations. The results of the present paper can be used for the reliability and risk assessment of structures, including stiffened steel panels with cracks.

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