Development of a Simplified Procedure for the Determination of the Ultimate Load and Associated Spindle Torque of Propeller Blades

2016 ◽  
Vol 60 (03) ◽  
pp. 171-185
Author(s):  
Claas Fischer ◽  
Wolfgang Fricke ◽  
Andreas Junglewitz
Keyword(s):  
Stress Distribution ◽  
Numerical Simulations ◽  
Ultimate Strength ◽  
Ultimate Load ◽  
Plastic Material ◽  
Plastic Behavior ◽  
Simplified Approach ◽  
Elastic Plastic ◽  
Blade Tip ◽  
Propeller Blades

Blade deflection observed in experiments regarding the ultimate strength of controllable pitch propeller blades does not agree with the one that is assumed in the load case for the blade failure load currently defined in the Polar Class Rules. The reason is that a failure of the blade tip due to large plastic deformation is not taken into account, but can occur in reality if the load is applied relatively close to the trailing edge of skewed propellers. The plastic blade deformation can be computed by numerical simulations using an elastic-plastic material curve. These simulations, however, are time consuming and, hence, unpractical in the daily design process of propeller blades. Therefore, a simplified approach to determine the ultimate load and the associated spindle torque of the blade is presented. It requires elastic finite element (FE) analyses with varying point of load application, geometrical data, and a simplified material curve. The critical blade section is determined from highly stressed locations found in the elastic FE analysis. Afterward, the ultimate bending moment which the section can carry is determined by assuming a linear strain distribution over the thickness and a definite limit strain on the pressure surface. This allows the stress distribution to be transferred directly from the material curve. The ultimate load is determined by integrating the stress distribution over the section thickness and along the chord length, the latter in a simplified way. The approach is supported by various numerical simulations showing the fundamental elastic-plastic behavior of propeller blades and their response due to superimposed bending and torsional loads. In conclusion, the ultimate strength is mainly controlled by bending loads and the approach considers a failure of the blade tip, leading to more realistic spindle torques compared to the approach in the Polar Class Rules.

Stress Analysis of SS316L Tube Die Expansion for High Pressure Gas Coolers

2020 ◽  
Author(s):  
Zijian Zhao ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Residual Stress ◽  
High Pressure ◽  
Plastic Material ◽  
Research Work ◽  
Material Behavior ◽  
Isotropic Hardening ◽  
Plastic Behavior ◽  
Expansion Process ◽  
Elastic Plastic ◽  
Stress States

Abstract SS316L finned tubes are becoming very popular in high-pressure gas exchangers and particularly in CO2 cooler applications. Due to the high-pressure requirement during operation, these tubes require an accurate residual stress evaluation during the expansion process. Indeed, die expansion of SS tubes creates not only high stresses when combined with operation stresses but also micro-cracks during expansion when the expansion process is not very well controlled. This research work aims at studying the elastic-plastic behavior and estimating the residual stress states by modeling the die expansion process. The stresses and deformations of the joint are analyzed numerically using the finite element method. The expansion and contraction process is modeled considering elastic-plastic material behavior for different die sizes. The maximum longitudinal, tangential and contact stresses are evaluated to verify the critical stress state of the joint during the expansion process. The importance of the material behavior in evaluating the residual stresses using kinematic and isotropic hardening is addressed.

Elastic-plastic model for the mechanical properties of paperboard as a function of moisture

2020 ◽  
Vol 35 (3) ◽  
pp. 353-361
Author(s):  
Gustav Marin ◽  
Mikael Nygårds ◽  
Sören Östlund
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Linear Relation ◽  
Plastic Material ◽  
Moisture Ratio ◽  
Plastic Behavior ◽  
Compression Tests ◽  
Elastic Plastic ◽  
Hardening Modulus ◽  
Two Parameters

AbstractTo verify a linear relation between normalized mechanical property and moisture ratio, in-plane tensile tests were performed on four types of paperboard from different manufacturers. Tensile properties were normalized with respect to the property at standard climate (50 % RH, 23 °C). Short-span Compression Tests were also performed to investigate if the relation was linear also for in-plane compression. The tests were performed at different relative humidity (20, 50, 70 and 90 % RH) but with constant temperature (23 °C) in MD and CD, respectively. The linear relation was confirmed for the normalized mechanical properties investigated. In fact, when also the moisture ratio was normalized with the standard climate, all paperboards coincided along the same line. Therefore, each mechanical property could be expressed as a linear function of moisture ratio and two parameters. Moreover, an in-plane bilinear elastic-plastic material model was suggested, based on four parameters: strength, stiffness, yield strength and hardening modulus, where all parameters could be expressed as linear functions of moisture ratio. The model could predict the elastic-plastic behavior for any moisture content from the two parameters in the linear relations and the mechanical properties at standard climate.

Preparation and Stress Calculation Analysis of Light Elastic-Plastic Material

2011 ◽  
Vol 189-193 ◽  
pp. 1432-1436
Author(s):  
Lin Chen ◽  
Jin Liang Duan ◽  
Ge Li ◽  
Jian Guo Wang
Keyword(s):  
Elastic Modulus ◽  
Stress Distribution ◽  
Plastic Material ◽  
Strain Curve ◽  
Mass Ratio ◽  
Stress Strain Curve ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Calculation Analysis ◽  
Heavy Rail

Based on the photo-elastic method, four groups of different ratio light elastic-plastic material were prepared by changing the epoxy resin, the firming agent, the plasticizer mass ratio; and the light elastic-plasticity material stress-strain curve and its elastic modulus E and Poisson's ratio were obtained through the stretch experiment. The light elastic-plastic rail models were made by 1:5, and the computation analyzes stress distribution of the rail head of the heavy rail and carried on the static examination. The stress stripe chart change rule of the light elastic-plasticity material during load and unload process was observed.

Ultimate Strength of Aluminum Plates and Stiffened Panels for Marine Applications

2004 ◽  
Vol 41 (03) ◽  
pp. 108-121
Author(s):  
Jeom Kee Paik ◽  
Alexandre Duran
Keyword(s):  
Aluminum Alloys ◽  
Ultimate Strength ◽  
Material Properties ◽  
Plastic Material ◽  
Steel Structures ◽  
Material Model ◽  
Stiffened Panels ◽  
Elastic Plastic ◽  
Steel Panels ◽  
Aluminum Plates

The use of high-strength aluminum alloys in marine construction has certainly obtained many benefits, particularly for building fast ferries and also for military purposes. It is commonly accepted that the collapse characteristics of aluminum structures are similar to those of steel structures until and after the ultimate strength is reached, regardless of the differences between them in terms of material properties. However, it is also recognized that the ultimate strength design formulas available for steel panels cannot be directly applied to aluminum panels even though the corresponding material properties are properly accounted for. This is partly due to the fact that the stress versus strain relationship of aluminum alloys is different from that of structural steel. That is, the elastic-plastic regime of material after the proportional limit and the strain hardening plays a significant role in the collapse behavior of aluminum structures, in contrast to steel structures where the elastic perfectly plastic material model is well adopted. Also, the softening in the heat-affected zone significantly affects the ultimate strength behavior of aluminum structures, whereas it can normally be neglected in steel structures. In this paper, the ultimate strength characteristics of aluminum plates and stiffened panels under axial compressive loads are investigated through ANSYS elastic-plastic large deflection finite element analyses with varying geometric panel properties. An "average" level of welding-induced softening and initial imperfections is assumed for the analyses. Closed-form ultimate compressive strength formulas for aluminum plates and stiffened panels are derived by regression analysis of the computed results.

Elastic-Plastic Analysis of the Circle-Castellated Steel Beam Using Finite Element Method

2011 ◽  
Vol 422 ◽  
pp. 854-857 ◽  
Author(s):  
Jun Li ◽  
Jia Wei Xiang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Distribution ◽  
Steel Beam ◽  
Plastic Behavior ◽  
Uniform Pressure ◽  
Bear Capacity ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Element Method

The elastic-plastic behavior of the circle-castellated steel beam is analyzed using finite element method. Stress distribution, expansion of plastic zone and flexural deflection are investigated under two simulation loads of the uniform pressure and concentration force. The results show that this kind of beam provide references for us to strengthen structural bear capacity.

The Elastic-Plastic Stress Distribution Within a Wide Curved Bar Subjected to Pure Bending

1955 ◽  
Vol 22 (3) ◽  
pp. 305-310
Author(s):  
Bernard W. Shaffer ◽  
Raymond N. House
Keyword(s):  
Stress Distribution ◽  
Convex Surface ◽  
Plastic Material ◽  
Circumferential Stress ◽  
Yield Condition ◽  
Bending Moment ◽  
Stress Distributions ◽  
Elastic Plastic ◽  
Tresca Yield Condition ◽  
Plastic Stress

Abstract Analytical expressions are obtained for the radial and circumferential stress distributions within a wide curved bar made of a perfectly plastic material when it is subjected to a uniformly distributed bending moment. The elastic stress distributions are based on the use of the Airy stress function, whereas the plastic stress distributions in this problem of plane strain are based on the use of the Tresca yield condition. It is found that as the bending moment increases in the direction which tends to straighten the initially curved bar, an elastic-plastic boundary develops first around the concave surface. It meets a second boundary, which starts sometime later around the convex surface, when the bar is completely plastic. The elastic region within the bar decreases at a fairly uniform rate as the bending moment increases to within approximately 90 per cent of the fully plastic bending moment but then it degenerates very much more rapidly until it no longer exists when the bar is completely plastic. The position of the neutral surface is independent of the applied bending moment when the stress distribution is within the completely elastic and the completely plastic ranges. Within the elastic-plastic range, however, it moves away from and then toward the center of curvature as the bending moment increases.

Numerical Study of Defect Free Elbows Subjected to In-Plane Bending Moment

2011 ◽  
Vol 189-193 ◽  
pp. 1494-1497
Author(s):  
Wang Chen ◽  
Yin Pei Wang ◽  
Pei Ning Li ◽  
Chen Jin ◽  
Xiao Ming Sun
Keyword(s):  
Numerical Study ◽  
Plastic Material ◽  
Three Dimensional ◽  
Bending Moment ◽  
Plastic Behavior ◽  
Piping System ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Bending Radius ◽  
Elastic Perfectly Plastic

Elbow is a type of components widely used in a piping system, and so it is very important to know the plastic carrying capacity of elbow. In this study, the elastic-plastic behavior of elbows with various ratios of t/rm and relative bending radius R/rm were investigated in detail by using of three-dimensional (3D) non-linear finite element (FE) analyses, assuming elastic-perfectly-plastic material behaviour and taking geometric nonlinearity into account. The analyses indicated that elbow exhibited different behavior obviously at the elastic-plastic states subjected to In-Plane opening bending moment and closing bending moment. The closed form equations of elbow involving effect of tangent pipes were established.

Effect of material's behavior on residual stress distribution in elastic–plastic beam bending: An analytical solution

2015 ◽  
Vol 231 (4) ◽  
pp. 361-372 ◽  
Author(s):  
Jalal Joudaki ◽  
Mohammad Sedighi
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Residual Stress Distribution ◽  
Material Behavior ◽  
Plastic Behavior ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Bending Radius ◽  
Beam Bending

A considerable residual stress distribution can be produced while bending of parts. This stress distribution depends on material behavior. In this article, residual stress distribution has been determined through the thickness in beam bending. For three different models of elastic–plastic behavior, the stress distribution and maximum residual stress are derived analytically. The residual stress is compared for three different bending radii as a case study. Also, finite element analysis has been carried out for two material properties. The results show that material behavior has little effect on stress distribution for large value of bending radius. As the bending radius decreases, difference of stress distribution increases rapidly among three plastic behaviors. Comparing the results of finite element and analytical stress distribution shows good accuracy for suggested formulations.

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