Research

25 pages, 5897 KiB

Open AccessArticle

A Simplified Method for Evaluating the Dynamic Response of the Metal Sandwich Structure under Explosion Load

by Kun Liu, Hewei Liu, Yao Li, Zeping Wang and Jiaxia Wang

Metals 2022, 12(11), 1933; https://doi.org/10.3390/met12111933 - 11 Nov 2022

Cited by 2 | Viewed by 1302

The metal sandwich structure is characterized by light weight, high stiffness, and high-impact energy absorption capacity, which is considered a good alternative protective structure in explosion scenarios. In this paper, four design forms of the metal sandwich structure are introduced, and the dynamic [...] Read more.

The metal sandwich structure is characterized by light weight, high stiffness, and high-impact energy absorption capacity, which is considered a good alternative protective structure in explosion scenarios. In this paper, four design forms of the metal sandwich structure are introduced, and the dynamic response of the metal sandwich structure under explosion load is researched. Then, a new analytical method is proposed to predict the dynamic response of the metal sandwich structure under explosion load, and numerical simulations are carried out to verify the accuracy of the proposed analysis method. The proposed analytical method is designed for aerial explosions without considering the fluid–structure interaction. In addition, a series of parameter studies are carried out, including the influence of the face sheet aspect ratio, the core height, and the thickness of the face sheet and core on the dynamic response of the sandwich structure under explosion load. The research in this paper has reference value for the anti-explosion design of the metal sandwich structure and will provide a useful reference for the design and optimization of the metal sandwich structure. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

14 pages, 5665 KiB

Open AccessArticle

Time-Domain Inversion Method of Impact Loads Based on Strain Monitoring Data

by Fanchao Wang, Kai Zheng, Bihao Chen, Yinghao Peng, Kun Liu and Dewen Tang

Metals 2022, 12(8), 1279; https://doi.org/10.3390/met12081279 - 29 Jul 2022

Cited by 1 | Viewed by 1030

Abstract

A helicopter deck is the main load-bearing component under the emergency landing conditions for helicopters. However, it is generally difficult to directly obtain the landing load from measurements due to the high randomness of the landing position. As the main design load of [...] Read more.

A helicopter deck is the main load-bearing component under the emergency landing conditions for helicopters. However, it is generally difficult to directly obtain the landing load from measurements due to the high randomness of the landing position. As the main design load of the helicopter deck, the emergency landing load is very important to its structural design. A large design load value leads to an overly conservative structural design and affects the control of the ship’s weight and center of gravity, while a small design load may lead to a lack of security and affect the safety of the helicopter and the ship. As a result, the time domain inversion method, which is based on strain monitoring data, is an important and effective method for obtaining the helicopter emergency landing load. In this study, a grillage model experiment was conducted to study the time domain inversion method. The helicopter impact load was simulated by falling body impact, and the impact load history and structural strain response were recorded by sensors. The grillage model impact load was calculated with different inversion methods, including the direct inverse, truncated singular value decomposition (TSVD), and Tikhonov regularization methods. The solution accuracy of different methods and number of sensors needed were compared. The results demonstrated that the Tikhonov regularization method based on four measurement points along with the L-curve determination criterion showed a better performance for capturing the impact load time history features. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

26 pages, 11013 KiB

Open AccessArticle

Experimental and Numerical Simulation of the Dynamic Response of a Stiffened Panel Suffering the Impact of an Ice Indenter

by Tongqiang Yu, Jiaxia Wang, Junjie Liu and Kun Liu

Metals 2022, 12(3), 505; https://doi.org/10.3390/met12030505 - 16 Mar 2022

Cited by 3 | Viewed by 1726

Abstract

At a laboratory scale, the response of a stiffened panel subjected to the impact of an ice indenter was studied by both experimental and numerical means. The experiment was conducted using a Falling Weight Impact Tester, and the impact force and deformation data [...] Read more.

At a laboratory scale, the response of a stiffened panel subjected to the impact of an ice indenter was studied by both experimental and numerical means. The experiment was conducted using a Falling Weight Impact Tester, and the impact force and deformation data of the stiffened panel were measured and recorded. The experimental results showed that the ice indenter could cause significant indentation to the stiffened panel and experienced severe crushing and scattering itself. Finite element analysis was performed to reproduce the structural deformations in an appropriate manner, and a constitutive model with a multisurface yield criterion and a dynamic empirical failure criterion for ice material was developed. Good agreement was obtained, and the influences of various parameters in the constitutive model and the performance of other different material models are discussed. The purpose of this study is to present an experimental and numerical study on a scenario of high-energy collision between a hull structure and an ice block, the conclusions of which can be very useful for studying ship-ice collisions and guiding engineering applications. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

16 pages, 8604 KiB

Open AccessArticle

A Novel Required Laser Energy Predicting Model for Laser Powder Bed Fusion

by Yang Liu, Mingxuan Li, Xiaofeng Lu, Xiaolei Zhu and Peng Li

Metals 2021, 11(12), 1966; https://doi.org/10.3390/met11121966 - 07 Dec 2021

Cited by 1 | Viewed by 2040

Abstract

During the process of laser powder bed fusion (LPBF) printing, the energy of heat input have a great influence on the quality of fabricated specimens. In this paper, based on the heat transfer and metallurgical mechanism, a theoretical predicting model of the required [...] Read more.

During the process of laser powder bed fusion (LPBF) printing, the energy of heat input have a great influence on the quality of fabricated specimens. In this paper, based on the heat transfer and metallurgical mechanism, a theoretical predicting model of the required laser energy to fabricate high-density LPBF components was established. The theoretical required laser energy density of AlSi10Mg, TC4 and 316L were calculated, which are 51.74 J/mm³, 104.48 J/mm³ and 69.28 J/mm³, respectively. By comparing with the experimental results in the references, it was found that the errors between them are within 10%. In addition, this article discussed the relationship between the VED and the specimen defects, and found that the changing in the VED will alter the types of specimen defects. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

21 pages, 5727 KiB

Open AccessArticle

Fracture Estimation in Ship Collision Analysis—Strain Rate and Thermal Softening Effects

by Burak Can Cerik and Joonmo Choung

Metals 2021, 11(9), 1402; https://doi.org/10.3390/met11091402 - 05 Sep 2021

Cited by 3 | Viewed by 2283

Abstract

This study examined the effects of the strain rate and thermal softening on large-scale ductile fracture in ship collisions using a rate-dependent combined localized necking and fracture model. A Johnson–Cook type-hardening model, consisting of strain hardening, rate-sensitivity, and thermal softening terms, was adopted [...] Read more.

This study examined the effects of the strain rate and thermal softening on large-scale ductile fracture in ship collisions using a rate-dependent combined localized necking and fracture model. A Johnson–Cook type-hardening model, consisting of strain hardening, rate-sensitivity, and thermal softening terms, was adopted together with an associated flow rule. The temperature was treated as an internal state variable and was calculated from the plastic strain energy using a strain-rate-dependent weighting function under fully isothermal and adiabatic conditions. At every time increment, the fracture locus was updated based on the temporal strain rate, whereas the necking locus was coupled with the hardening law, which was dependent on both the strain rate and temperature. The damage indicator framework was used to consider the non-proportional loading paths. The dynamic shell-element failure model was verified through plate-panel penetration tests and applied to a large-scale ship collision analysis involving a struck ship/ship-shaped offshore installation and a supply vessel. The effects of the loading rate and impact energy were assessed in terms of the global behavior of the structure and observed failure modes. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

15 pages, 19834 KiB

Open AccessArticle

Multi-Objective Optimization Design of Corrugated Steel Sandwich Panel for Impact Resistance

by Li Ke, Kun Liu, Guangming Wu, Zili Wang and Peng Wang

Metals 2021, 11(9), 1378; https://doi.org/10.3390/met11091378 - 31 Aug 2021

Cited by 6 | Viewed by 1524

Abstract

The application of corrugated steel sandwich panels on ships requires excellent structural performance in impact resistance, which is often achieved by increasing the weight without giving full play to the characteristics of the structure. Considering the mechanical properties of sandwich panels under static [...] Read more.

The application of corrugated steel sandwich panels on ships requires excellent structural performance in impact resistance, which is often achieved by increasing the weight without giving full play to the characteristics of the structure. Considering the mechanical properties of sandwich panels under static and impact loading, a multi-objective optimal method based on a back-propagation (BP) neural network and a genetic algorithm developed in MATLAB is proposed herein. The evaluation criteria for this method included structural mass, static and dynamic stress, static and dynamic deformation, and energy absorption. Before optimization, representative sample points were obtained through numerical simulation calculations. Then, the functional relationship between the design and output variables was generated using the BP neural network. Finally, a standard genetic algorithm (SGA) and an adaptive genetic algorithm (AGA) were used for multi-objective optimization analysis with the established function to obtain the best result. Through this study, a new design concept with high efficiency and reliability was developed to determine the structural parameters that provide the best impact resistance using limited sample points. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

25 pages, 15855 KiB

Open AccessArticle

Experimental Research and Simulation Analysis of Lightning Ablation Damage Characteristics of Megawatt Wind Turbine Blades

by Yang Zhao, Bin Yang and Yao Zhang

Metals 2021, 11(8), 1251; https://doi.org/10.3390/met11081251 - 06 Aug 2021

Cited by 4 | Viewed by 1665

Abstract

In this paper, the damage mechanism of glass fiber reinforced composite (GFRC) under lightning strike by laying and inserting copper wires in the laminate was studied. The ablation characteristics of GFRC under different lightning current components were explored. Scanning electron microscope (SEM) was [...] Read more.

In this paper, the damage mechanism of glass fiber reinforced composite (GFRC) under lightning strike by laying and inserting copper wires in the laminate was studied. The ablation characteristics of GFRC under different lightning current components were explored. Scanning electron microscope (SEM) was used to conduct the morphology analysis at the damaged area. The results show that the high temperature induced by lightning striking leads to resin pyrolysis, glass fiber (GF) sublimation, and stress waves, which results in fiber breakage and delamination. Then, a finite element (FE) thermal-electric coupling model for predicting the lightning ablation damage of GFRC was established. The comparison between the simulation and experimental results are in good agreement, which validate the effectiveness of the proposed FE model. The relationship between the lightning ablation area and the lightning current amplitude, charge amount, and specific energy in creeping discharge and through discharge was obtained by data fitting. The whole ablation damage process was revealed by FE simulation. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

14 pages, 5509 KiB

Open AccessFeature PaperArticle

Optimal Design of the Shape of a Non-Ball Mandrel for Thin-Walled Tube Small Radius Cold Bending

by Lu Bai, Jun Liu, Ziang Wang and Shuanggui Zou

Metals 2021, 11(8), 1221; https://doi.org/10.3390/met11081221 - 30 Jul 2021

Cited by 4 | Viewed by 1754

Abstract

In the field of cold bending, it is necessary to use ball mandrels, especially to bend thin-walled tubes with a small radius. However, the bending process with a ball mandrel is complex and expensive, and it is easy to jam the core ball [...] Read more.

In the field of cold bending, it is necessary to use ball mandrels, especially to bend thin-walled tubes with a small radius. However, the bending process with a ball mandrel is complex and expensive, and it is easy to jam the core ball inside the tube. To solve these issues, we designed two kinds of hollow non-ball mandrel schemes with low stiffness that were suitable for the small radius bending of thin-walled tubes. We evaluated the forming quality of cold bending numerically and the influence of the hollow section length and thickness on the forming indices. Our results showed that the thickness of the hollow section has a greater influence on forming quality than the length. As the hollow section’s thickness increased, the wrinkling rate first declined by approximately 40% and then increased by above 50%. When the thickness was 11 mm in scheme 1 and 13 mm in scheme 2, the wrinkling rate reached minimum values of 1.32% and 1.50%, respectively. As the hollow section’s thickness increased, the flattening rate decreased by more than 60% and the thinning rate increased by about 40%. A multi-objective optimization of forming indices was carried out by ideal point method and grey wolf optimizer. By comparing the forming results before and after optimization, the feasibility of using the proposed hollow mandrel was proved, and the hollow mandrel scheme of standard cylinder is therefore recommended. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

19 pages, 11105 KiB

Open AccessArticle

Failure Mechanism and Strength Prediction Model of T-Joint of Composite Sandwich Structure

by Yang Liu, Mingxuan Li, Xiaofeng Lu and Xiaolei Zhu

Metals 2021, 11(8), 1197; https://doi.org/10.3390/met11081197 - 27 Jul 2021

Cited by 5 | Viewed by 1968

Abstract

Composite sandwich structures are widely used in many fields. T-joint plays a significant role in the composite sandwich structural connection. In this paper, a type of adhesive T-joint was manufactured and tested under bending and shearing load. According to the experiment, the finite [...] Read more.

Composite sandwich structures are widely used in many fields. T-joint plays a significant role in the composite sandwich structural connection. In this paper, a type of adhesive T-joint was manufactured and tested under bending and shearing load. According to the experiment, the finite element model was established to reveal the failure process. A strength prediction model was proposed based on the simulation. The results showed that the T-joint’s lower connector and the web’s lower face panel controlled its maximum load-bearing capacity, and the failure mode is the fiber compressive damage. The predicted ultimate bearing capacity of the T-joint showed a good agreement with the simulation, and the maximum relative error was less than 3%. Full article

(This article belongs to the Special Issue Special Materials for Shipbuilding)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Special Materials for Shipbuilding

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (9 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI