Residual Strength of Pitted Mild Steel Plates Subjected to Biaxial Compression

2016 ◽  
Author(s):  
Xiaoli Jiang ◽  
C. Guedes Soares
Keyword(s):  
Mild Steel ◽  
Pitting Corrosion ◽  
Residual Strength ◽  
Fem Analysis ◽  
Steel Plates ◽  
Biaxial Compression ◽  
Rectangular Plates ◽  
Nonlinear Fem ◽  
Unique Parameter

The present paper focus on the residual strength of pitted mild steel rectangular plate under biaxial compression. This paper aims to propose a general and practical formula to predict the residual strength of pitted rectangular plates under biaxial compression starting from the classic formula for intact rectangular plates and assessing whether it can be applicable to pitted plates, where the degree of pitting corrosion is modelled as one key parameter. Firstly, the numerical model is verified with an existing case study. Afterwards, a series of nonlinear FEM analysis are performed, changing geometrical attributes of both pits and plates, i.e., the radius and location of pits and the slenderness of plates. Based on those simulation results, it is found that the classic formula for intact rectangular plates can be applied reasonably well for pitting corroded plates. A unique parameter DOP (degree of pitting), which is easily determined, is employed to evaluate the effect of pitting corrosion with adequately accuracy and without bias to either longitudinal or transverse compressive stress. The proposed formula can provide guidance during the process of ship structural maintenance decision-making and strength reassessment conveniently.

Ultimate Capacity Behavior of Pitted Mild Steel Plates Under Biaxial Compression

2011 ◽  
Author(s):  
Xiaoli Jiang ◽  
C. Guedes Soares
Keyword(s):  
Mild Steel ◽  
Biaxial Loading ◽  
Fem Analysis ◽  
Steel Plates ◽  
Dominant Factor ◽  
Biaxial Compression ◽  
Ultimate Capacity ◽  
Thickness Loss ◽  
Loading Ratio ◽  
Corrosion Pits

The aim of the present paper is to investigate the effects of corrosion pits on the ultimate capacity of rectangular mild steel plates under biaxial compression. A series of non-linear FEM analysis on plates with partial depth pits are carried out, changing geometrical attributes of both pits and plates, i.e., the radius, depth, location and distribution of the pits and the slenderness of the plates. Possible interaction between transverse and longitudinal axial compression is studied applying different level of loading ratio and considering the effects of partial depth pitting corrosion. It is shown that biaxial loading ratio is a dominant factor affecting the behavior of pitted plates besides pits intensity and thickness loss at pits. When longitudinal compression is dominant load with loading ratio lower than 1, the interaction relationship curves for different DOP levels tend to be parallel with each other and the distance between every two parallel curves seems to be dependent mainly on the deviation of their DOP values and thickness loss at pits. Moreover, pits distribution along long and shirt edges could also affect the ultimate strength behavior of plates. The work done in the paper illustrates that the ultimate capacity of pitted plate could be derived from intact plate by introducing important influential parameters like DOP, thickness loss and possible pits distribution.

Effect of Initial Distortions on the Ultimate Capacity of Pitting Corroded Plates

2013 ◽  
Author(s):  
Xiaoli Jiang ◽  
C. Guedes Soares
Keyword(s):  
Ultimate Strength ◽  
Input Data ◽  
Fem Analysis ◽  
Influential Factors ◽  
Steel Plates ◽  
Initial Deflection ◽  
Biaxial Compression ◽  
Ultimate Capacity ◽  
Nonlinear Fem ◽  
Collapse Behavior

The aim of the present paper is to investigate the effects of the initial deflection shape on the ultimate capacity of pitting corroded plates under biaxial compression. A series of nonlinear FEM analysis of plates with partial depth pits are carried out, changing the geometrical attributes of both pits and plates, i.e., the radius, depth and location of the pits and the slenderness of the plates. A realistic thin-horse shape initial deflection and a simplified buckling shape initial deflection are assumed and compared. It is shown that the initial deflection shape has a tremendous effect on the ultimate strength of pitted mild steel plates. The ultimate strength of a pitted plate with thin-horse shaped initial deflection is generally lower than that of a plate with buckling shaped initial deflection provided that other influential factors are same. Their deviation is sensitive to plate slenderness and pit intensity. The simplified buckling shaped initial deflection could be sufficient to predict the ultimate strength of the plate under longitudinal uniaxial compression. However, in case of less predominant biaxial compression, the buckling shaped initial deflection may overestimate the prediction and give non-conservative results. In this respect, it is preferable to use the initial deflection measurements as input data for the analysis of the plate collapse behavior.

Visual Assessment of Corroded Condition of Plates With Pitting Corrosion Taking Into Account Residual Strength: In the Case of Webs of Hold Frames of Bulk Carriers

2007 ◽  
Author(s):  
Tatsuro Nakai ◽  
Hisao Matsushita ◽  
Norio Yamamoto
Keyword(s):  
Ultimate Strength ◽  
Pitting Corrosion ◽  
Residual Strength ◽  
Steel Plates ◽  
Average Thickness ◽  
Loading Conditions ◽  
Equivalent Thickness ◽  
Thickness Loss ◽  
Minimum Cross Section ◽  
Corrosion Pits

Corrosion pits with a conical shape are typically observed in hold frames in way of cargo holds of bulk carriers which carry coal and iron ore. The ratio of the diameter to the depth of the typical corrosion pits is in the range between 8–1 and 10–1 and its diameter might become up to 50mm. The evaluation of residual strength of members with large uneven pitting corrosion is difficult compared with that of members with general corrosion. Therefore, it is of crucial importance to develop a method for the evaluation of residual strength of pitted members. The purpose of the present study is to investigate the effect of pitting corrosion on the ultimate strength of steel plates under various loading conditions and explore a method for the evaluation of residual thickness of pitted plates. In the present study, a series of non-linear FE-analyses has been conducted with steel plates with a variety of random pit distributions under various loading conditions such as uni-axial compression, bi-axial compression, shear and combination of these. In these analyses, random pit distributions were calculated by the previously developed corrosion model. It has been shown that equivalent thickness loss, which is defined as thickness loss of uniformly corroded plates with the same ultimate strength as the randomly pitted plates, is smaller than or equal to 1.25 times the average thickness loss. It has been also revealed that the equivalent thickness loss for the ultimate strength under the above-mentioned loading conditions is smaller than average thickness loss at the minimum cross section, where the average thickness loss at the minimum cross section almost corresponds to the equivalent thickness loss for the tensile strength. Based on these findings, a method for the estimation of equivalent thickness loss of pitted plates has been discussed using the thickness diminution-DOP relationship, where DOP (Degree of Pitting Intensity) is defined as the ratio of the pitted surface area to the total surface area.

Ultimate Compressive Capacity of Rectangular Plates With Partial Depth Pits

2010 ◽  
Author(s):  
Xiaoli Jiang ◽  
C. Guedes Soares
Keyword(s):  
Compressive Strength ◽  
Fem Analysis ◽  
Volume Effect ◽  
Steel Plates ◽  
Rectangular Plates ◽  
Ship Hulls ◽  
Single Side ◽  
Corrosion Pits ◽  
Extent Of Damage ◽  
Heavy Damage

Pitting corrosion has been one of main corrosion type of immersed ship hulls, which can bring heavy damage and even accidents to in-service ships, particularly to aged ships. To investigate the effects of pits on the ultimate compressive strength of mild steel plates, a series of non-linear FEM analysis on plates with partial depth corrosion pits are undertaken in the paper, changing the size, intensity and location of pits and the slenderness of plates. It is shown that the eccentricity induced by single side distributed pits has considerable degrading effects on the ultimate compressive capacity of plates. Although the degree of pit corrosion (DOP) does reflect the effect of pits to a large extent, it is not enough to rely on DOP exclusively to represent the extent of damage caused by pits, as “volume effect” should be considered.

scholarly journals FEM analysis for nonuniform yielding processes in mild steel plates under stretching.

1990 ◽  
Vol 56 (529) ◽  
pp. 1969-1976
Author(s):  
Misao ITOH ◽  
Fusahito YOSHIDA ◽  
Yoshimi YAMASHITA ◽  
Masanobu OHMORI
Keyword(s):  
Mild Steel ◽  
Fem Analysis ◽  
Steel Plates

Ultimate Compressive Capacity of Rectangular Plates With Partial Depth Pits

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Xiaoli Jiang ◽  
C. Guedes Soares
Keyword(s):  
Compressive Strength ◽  
Volume Effect ◽  
Steel Plates ◽  
Rectangular Plates ◽  
Nonlinear Fem ◽  
Ship Hulls ◽  
Single Side ◽  
Corrosion Pits ◽  
Extent Of Damage ◽  
Heavy Damage

Pitting corrosion has been one of the main corrosion types of immersed ship hulls, which can bring heavy damage and even accidents to in-service ships, particularly to aged ships. The aim of the present paper was to investigate the effects of pits on the ultimate compressive strength of mild steel plates under uniaxial compression. A series of nonlinear FEM analyses on plates with partial depth corrosion pits were carried out, changing the size, intensity and location of pits and the slenderness of plates. It was shown that the eccentricity induced by single side distributed pits had considerable degrading effects on the ultimate compressive capacity of plates. Although the degree of pit corrosion (DOP) did reflect the effect of pits to a large extent, it was not enough to rely on DOP exclusively to represent the extent of damage caused by pits, as “volume effect” should be considered.

scholarly journals FEM Analysis for Nonuniform Yielding Processes in Mild Steel Plates under Stretching

1992 ◽  
Vol 35 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Misao ITOH ◽  
Fusahito YOSHIDA ◽  
Yoshimi YAMASHITA ◽  
Masanobu OHMORI
Keyword(s):  
Mild Steel ◽  
Fem Analysis ◽  
Steel Plates
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