Damage Tolerance Assessment of Multi-Hull Aluminum Vessels Using Global Finite Element Methods

2021 ◽  
Author(s):  
Spencer Johnson ◽  
Boyden Williams ◽  
Christopher Palm
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
High Speed ◽  
Damage Tolerance ◽  
Element Model ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Hull Structure ◽  
Class Dynamic ◽  
Critical Locations

As aluminum high-speed multi-hulls continue to grow in size, capacity and operational sea state, a need is growing to understand the damage tolerance of these structures. This paper presents a Linear Elastic Fracture Mechanics (LEFM) approach to performing damage tolerance assessments of aluminum hull structures using the hydrodynamic analysis and global finite element model developed as part of a class Dynamic Loading Approach (DLA) notation. The LEFM approach is used to calculate the stress intensity factor (K) and the critical crack length throughout the model to screen the entire hull structure and identify fracture critical locations. This paper also investigates the use of elastic-plastic fracture mechanics to predict potential critical crack growth locations, rates, and directions. Fracture critical locations identified and visualized through the analysis provide the ship designer with tools to develop damage tolerant structures. The results of the analysis can also assist owners and regulatory bodies in developing structural inspection and repair plans.

Evaluation of Existing Fracture Mechanics Models for Burst Pressure Predictions, Theoretical and Experimental Aspects

2014 ◽  
Author(s):  
Samarth Tandon ◽  
Ming Gao ◽  
Ravi Krishnamurthy ◽  
Shahani Kariyawasam ◽  
Richard Kania
Keyword(s):  
Fracture Mechanics ◽  
High Speed ◽  
Base Material ◽  
Element Model ◽  
Burst Pressure ◽  
Critical Crack ◽  
Integrity Assessment ◽  
Seam Weld ◽  
Crack Location ◽  
Weld Area

The predictions of burst pressure and leak/rupture have significant impact on the pipeline integrity assessment results, and subsequently on the extent of the required mitigation and re-inspection interval. There are models available for burst pressure and leak/rupture prediction in the literature, namely API-579, CorLas®, and NG-18 (Modified Ln-Sec). In this paper, evaluation of existing fracture mechanics models for burst pressure and leak/rupture prediction for external crack and crack like features including stress corrosion cracks (SCC) are performed. Both theoretical and practical aspects of each model are discussed in detail. An experiment is set up to conduct fifteen full scale burst tests of 20-inch, 34-inch and 36-inch diameter joints removed from the pipeline field. Among them, seven pipe joints are with base material SCC, four joints with seam weld cracks, three joints with linearly aligned crack-like features surrounded with shallow base material SCC, and one joint with crack-like feature in the Weld area. A high speed camera is utilized to capture rupture events. The rupture events can be stable tearing, crack coalescence and unstable propagation of a critical crack or multiple closely aligned cracks in a crack colony which are responsible for the rupture. Detailed profile measurements of the critical crack/s for burst pressure predictions are done from the fracture surfaces. Relevant material properties are measured for each joint in base material or seam weld location depending on the crack location. Burst pressure predictions are performed with models available in API-579, CorLas®, and Modified NG-18. An elastic-plastic finite element model is generated to quantify the effective stress intensity factor with and without the end cap effects during the burst testing. The accuracy and conservatism of the models evaluated are analyzed. Implications of the findings are discussed.

Cracks and Structural Redundancy

1996 ◽  
Vol 33 (04) ◽  
pp. 290-298
Author(s):  
Arne Stenseng
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Finite Element Model ◽  
Fatigue Cracks ◽  
Element Model ◽  
Intensity Level ◽  
Critical Crack ◽  
Critical Crack Length

This paper proposes a way to use finite element models to determine the effect of fatigue cracks in ship structures. Cracks of different lengths are modeled and the maximum nodal stress at the crack tip is used to estimate the stress intensity level. The calculated stress intensity factor is substituted into fracture mechanics equations to calculate the rate of crack growth and the critical crack length. The main advantage to calculating the stress intensity factor from an appropriate finite element model is that load redistribution effects are included. Since the ship structure is redundant, load shedding and multiple load paths can significantly reduce the propagation rate and thereby improve the safety of the structure. Including the crack in the finite element model also makes it possible to study the crack's impact on the stress levels in surrounding structure. The method is independent of the cause of structural failure, hence this kind of analysis can be used to investigate the effects of cracks created by fatigue, collision, or grounding damage.

Research on the Effects of Welding Sequence on Welding Residual Stress of High-Speed Train Based on SYSWELD

2011 ◽  
Vol 399-401 ◽  
pp. 1806-1811
Author(s):  
Yong Hong Chen ◽  
Peng Chen ◽  
Ai Qin Tian
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
High Speed ◽  
Element Model ◽  
Welding Residual Stress ◽  
High Speed Train ◽  
Distribution Law ◽  
Element Analysis ◽  
Welding Sequence ◽  
Maximum Residual Stress

The finite element model of the roof of aluminum high-speed train was established, double ellipsoid heat source was employed, and heat elastic-plastic theory was used to simulate welding residual stress of the component under different welding sequence based on the finite element analysis software SYSWELD. The distribution law of welding residual stress was obtained. And the effects of the welding sequence on the value and distribution of residual stress was analyzed. The numerical results showed that the simulation data agree well with experimental test data. The maximum residual stress appears in the weld seam and nearby. The residual stress value decreases far away from the welding center. Welding sequence has a significant impact on the final welding residual stress when welding the roof of aluminum body. The side whose residual stress needs to be controlled should be welded first.

Static and Dynamic Analyses of the LSES Hull Structure

1978 ◽  
Vol 22 (02) ◽  
pp. 110-122
Author(s):  
A. S. Hananel ◽  
E. J. Dent ◽  
E. J. Philips ◽  
S. H. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Surface Effect ◽  
Three Dimensional ◽  
Element Model ◽  
Finite Element Program ◽  
Hull Structure ◽  
Surface Effect Ship ◽  
Hull Design ◽  
Element Program

To avoid the conservativeness in the large surface-effect ship hull design which results from simplifying assumptions in the stress analysis, the hull structure was analyzed as a three-dimensional elastic body. The NASTRAN finite-element program, level 15.0, was selected for use in this analysis as the most suitable program available. A finite-element model representing the true hull stiffness was used in obtaining the internal load and displacement distributions. The inertia effect of the ship masses was included with each set of static loads. This was done by using the Static Analysis with Inertia Relief solution included in NASTRAN. The stress redistribution around cutouts in the hull was treated in a separate study. The interaction between hull and deckhouse was investigated by attaching a model of the deckhouse onto the hull model, and then solving for the appropriate load conditions. The natural frequencies were obtained using a reduced finite-element model of both the hull and hull/deckhouse combination. A new technique was developed for determining the dynamic stresses and their proper superposition on the static stresses.

Simulation and Experimental Research on Milling Force of High Manganese Steel

2010 ◽  
Vol 143-144 ◽  
pp. 863-867
Author(s):  
Yong Tang ◽  
Qiang Wu ◽  
Xiao Fang Hu ◽  
Yu Zhong Li
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
High Speed ◽  
Shear Failure ◽  
Element Model ◽  
Manganese Steel ◽  
High Manganese ◽  
Milling Force ◽  
High Manganese Steel ◽  
High Speed Milling

The milling process of hard-to-cut material high manganese steel ZGMn13 was simulated and experimental studied based on Johnson-Cook material model and shear failure model.The high speed milling processing finite element model has established adopting arbitrary Lagrangian-Euler method (ALE) and the grid adaptive technology,The influence of milling parameters to milling force is analyzed in the high speed milling high manganese steel process. The simulated and experimental results being discussed are matched well. It certifies the finite element model is correct.

Fracture Mechanics of Bone

1993 ◽  
Vol 115 (4B) ◽  
pp. 549-554 ◽  
Author(s):  
J. W. Melvin
Keyword(s):  
Fracture Mechanics ◽  
Bone Fracture ◽  
Longitudinal Crack ◽  
Compact Bone ◽  
Plastic Zone Size ◽  
Geometric Constraints ◽  
External Loading ◽  
Specimen Thickness ◽  
Critical Crack ◽  
Critical Crack Length

This paper reviews the progress that has been made in applying the principles of fracture mechanics to the topic of fracture of long bones. Prediction of loading conditions which result in the propagation of fractures in bones has been of interest to the field of trauma biomechanics and orthopedics for over one hundred years. Independent verifications, by various investigators, of bone fracture mechanics parameters are reviewed and investigations of the effects of bone density and specimen thickness on the critical fracture mechanics parameters and of other factors such as critical crack length and plastic zone size in bovine femoral bone, and the effects of crack velocity on fracture mechanics parameters in bovine tibial bone are discussed. It took over ten years for the techniques of bone fracture mechanics to be applied to human compact bone, due primarily to geometric constraints from the smaller size of human bones. That work will be reviewed along with other continuing work to define the orientation dependence of the fracture mechanics parameters in bone and to refine the experimental techniques needed to overcome the geometric constraints of specimen size. A discussion is included of work still needed to determine fracture mechanics parameters for transverse and longitudinal crack propagation in human bone and to establish the effects of age on those parameters. Finally, a discussion will be given of how this knowledge needs to be extended to allow prediction of whole bone fracture from external loading to aid in the design of protective systems.

Modeling and Simulation of High Speed Intermittent Cutting Based on the Finite Element Method

2013 ◽  
Vol 683 ◽  
pp. 556-559
Author(s):  
Bin Bin Jiao ◽  
Fu Sheng Yu ◽  
Yun Jiang Li ◽  
Rong Lu Zhang ◽  
Gui Lin Du ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Field ◽  
Cutting Force ◽  
High Speed ◽  
Element Model ◽  
Periodic Variation ◽  
Element Analysis ◽  
Intermittent Cutting ◽  
Element Method

In order to study the distribution of the stress field in the high-speed intermittent cutting process, finite element model of high-speed intermittent cutting is established. Exponential material model of the constitutive equation and adaptive grid technology are applied in the finite element analysis software AdvantEdge. The material processing is simulated under certain cutting conditions with FEM ( Finite Element Method ) and the distribution of cutting force, stress field, and temperature field are received. A periodic variation to the cutting force and temperature is showed in the simulation of high-speed intermittent cutting. Highest value of the milling temperature appears in front contacting area of the knife -the chip.and maximum stress occurs at the tip of tool or the vicinity of the main cutting edge. The analysis of stress and strain fields in-depth is of great significance to improve tool design and durability of tool.

Sign in / Sign up

Export Citation Format

Share Document