Numerical Prediction of Maximum Load-Carrying Capacity of Cracked Alloy 690TT Steam Generator Tubes

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Jun-Young Jeon ◽  
Yun-Jae Kim ◽  
Jin-Weon Kim ◽  
Kuk-Hee Lee ◽  
Jong-Sung Kim
Keyword(s):  
Steam Generator ◽  
Test Data ◽  
Carrying Capacity ◽  
Damage Model ◽  
Maximum Load ◽  
Simulation Method ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Steam Generator Tubes ◽  
Strain Model

This paper presents a finite element (FE) simulation technique to predict maximum load-carrying capacity of cracked steam generator tubes and its application to Alloy 690TT tubes. The simulation method is based on a simplified version of the stress modified fracture strain model. The damage model is determined from tensile test and one cracked tube test data. Predicted maximum pressures are compared with 23 test data of axial through-wall and surface cracked Alloy 690TT steam generator tubes. Comparison with experimental data shows good agreement.

Maximum load carrying capacity of mobile manipulators: optimal control approach

Robotica ◽  
2009 ◽  
Vol 27 (1) ◽  
pp. 147-159 ◽  
Author(s):  
M. H. Korayem ◽  
A. Nikoobin ◽  
V. Azimirad
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Carrying Capacity ◽  
Nonholonomic Constraints ◽  
Maximum Load ◽  
Mobile Manipulators ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYIn this paper, finding the maximum load carrying capacity of mobile manipulators for a given two-end-point task is formulated as an optimal control problem. The solution methods of this problem are broadly classified as indirect and direct. This work is based on the indirect solution which solves the optimization problem explicitly. In fixed-base manipulators, the maximum allowable load is limited mainly by their joint actuator capacity constraints. But when the manipulators are mounted on the mobile bases, the redundancy resolution and nonholonomic constraints are added to the problem. The concept of holonomic and nonholonomic constraints is described, and the extended Jacobian matrix and additional kinematic constraints are used to solve the extra DOFs of the system. Using the Pontryagin's minimum principle, optimality conditions for carrying the maximum payload in point-to-point motion are obtained which leads to the bang-bang control. There are some difficulties in satisfying the obtained optimality conditions, so an approach is presented to improve the formulation which leads to the two-point boundary value problem (TPBVP) solvable with available commands in different softwares. Then, an algorithm is developed to find the maximum payload and corresponding optimal path on the basis of the solution of TPBVP. One advantage of the proposed method is obtaining the maximum payload trajectory for every considered objective function. It means that other objectives can be achieved in addition to maximize the payload. For the sake of comparison with previous results in the literature, simulation tests are performed for a two-link wheeled mobile manipulator. The reasonable agreement is observed between the results, and the superiority of the method is illustrated. Then, simulations are performed for a PUMA arm mounted on a linear tracked base and the results are discussed. Finally, the effect of final time on the maximum payload is investigated, and it is shown that the approach presented is also able to solve the time-optimal control problem successfully.

Development of Z-Factor for Circumferential Part-Through Surface Cracks in Dissimilar Metal Welds

2008 ◽  
Author(s):  
D.-J. Shim ◽  
G. M. Wilkowski ◽  
D. L. Rudland ◽  
F. W. Brust ◽  
Kazuo Ogawa
Keyword(s):  
Correction Factor ◽  
Carrying Capacity ◽  
Limit Load ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Surface Cracks ◽  
Crack Driving Force ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
J Estimation

Section XI of the ASME Code allows the users to conduct flaw evaluation analyses by using limit-load equations with a simple correction factor to account elastic-plastic fracture conditions. This correction factor is called a Z-factor, and is simply the ratio of the limit-load to elastic-plastic fracture mechanics (EPFM) maximum-load predictions for a flaw in a pipe. The past ASME Section XI Z-factors were based on a circumferential through-wall crack in a pipe rather than a surface crack. Past analyses and pipe tests with circumferential through-wall cracks in monolithic welds showed that the simplified EPFM analyses (called J-estimation schemes) could give good predictions by using the toughness, i.e., J-R curve, of the weld metal and the strength of the base metal. The determination of the Z-factor for a dissimilar metal weld (DMW) is more complicated because of the different strength base metals on either side of the weld. This strength difference can affect the maximum load-carrying capacity of the flawed pipe by more than the weld toughness. Recent work by the authors for circumferential through-wall cracks in DMWs has shown that an equivalent stress-strain curve is needed in order for the typical J-estimation schemes to correctly predict the load carrying capacity in a cracked DMW. In this paper, the Z-factors for circumferential surface cracks in DMW were determined. For this purpose, a material property correction factor was determined by comparing the crack driving force calculated from the J-estimation schemes to detailed finite element (FE) analyses. The effect of crack size and pipe geometry on the material correction factor was investigated. Using the determined crack-driving force and the appropriate toughness of the weld metal, the Z-factors were calculated for various crack sizes and pipe geometries. In these calculations, a ‘reference’ limit-load was determined by using the lower strength base metal flow stress. Furthermore, the effect of J-R curve on the Z-factor was investigated. Finally, the Z-factors developed in the present work were compared to those developed earlier for through-wall cracks in DMWs.

The Elastic-Softening Failure of Floating Beams

1988 ◽  
Vol 32 (01) ◽  
pp. 37-43
Author(s):  
Paul C. Xirouchakis
Keyword(s):  
Carrying Capacity ◽  
Maximum Load ◽  
Point Load ◽  
Negative Stiffness ◽  
Load Carrying Capacity ◽  
Perfectly Plastic ◽  
Load Carrying ◽  
Elastic Perfectly Plastic ◽  
The Moment ◽  
Elastic Softening

The solution is presented for an infinite elastic-softening floating beam under a point load. The response depends on two nondimensional parameters: the negative stiffness coefficient that characterizes the descending part of the moment-curvature curve, and the nondimensional softening region half-length. The solution exhibits two important features that the elastic-perfectly plastic solution does not show. First, in certain ranges of parameters, the elastic-softening beam has a clearly defined maximum load carrying capacity. Second, in some other ranges of parameters, the elastic-softening beam has a minimum load or residual strength. The beam stiffens up upon further deformation due to the reactions of the water foundation. Critical softening parameters are calculated that separate stable from unstable behavior.

Progressive Failure Analysis of an Integral Composite Joint for Thrust Reverser Cascade

2019 ◽  
Vol 795 ◽  
pp. 325-332
Author(s):  
Ji Shen Yang ◽  
Hong Yu Qi ◽  
Xiao Guang Yang ◽  
Duo Qi Shi
Keyword(s):  
Carrying Capacity ◽  
Composite Structure ◽  
Progressive Failure ◽  
Damage Model ◽  
Research Work ◽  
Failure Behavior ◽  
Load Carrying Capacity ◽  
Composite Joint ◽  
Bending Load ◽  
Load Carrying

The research work in this paper is focused on studying the failure behavior of an integral π-shaped laminated composite structure subjected to a bending load. A progressive damage model based on the 3D Tsai-Wu failure criterion and a developed gradual degradation model was employed to simulate and assess the load-carrying capacity, the onset and propagation of damage, and the failure mechanisms. For this unique π-shaped composite structure, disbonding was found to be the dominant damage mode under bending load, and the approximate maximum load could be maintained for a brief time during the final failure due to the gradual loss nature of the load-carrying capacity. The extent of damage was found to be more serious on the side of Rib II compared to the other side.

AN IMPROVED ANALYTICAL METHOD FOR RESTRAINED RC STRUCTURES SUBJECTED TO STATIC AND DYNAMIC LOADS

2013 ◽  
Vol 14 (01) ◽  
pp. 1350052 ◽  
Author(s):  
LI CHEN ◽  
QIN FANG ◽  
ZHIKUN GUO ◽  
JINCHUN LIU
Keyword(s):  
Test Data ◽  
Carrying Capacity ◽  
Analytical Method ◽  
Action Theory ◽  
Reinforcement Ratio ◽  
Dynamic Resistance ◽  
Load Carrying Capacity ◽  
Membrane Action ◽  
Rc Structures ◽  
Load Carrying

Once a RC structure is laterally restrained, both the static and dynamic load resistances will be enhanced due to the membrane action. Despite this known advantage, the apparent lack of systemic and efficient methods of analysis poses a drawback in the design and assessment of blast-resistant RC structures. First, a simplified membrane action theory was presented by modifying the maximum membrane force design method (MMFM) for predicting the total static resistance-deflection curves of restrained beam-slab RC structures. Second, a series of constrained beams were tested to validate the new theory, for which better agreement was observed between the test data, the results predicted by the proposed theory and those by MMFM. The results show that the static load carrying capacity and membrane force increase with increasing restraint stiffness, and the smaller the reinforcement ratio is, the larger the load carrying capacity increases. Third, based on the improved compressive static membrane action theory, a new analytical method was developed to investigate the dynamic responses of restrained RC structures subjected to blast loads, using an equivalent single degree of freedom system that combines the three-parameter elasto-viscoplastic rate-sensitive material model with the proposed static theory. Good agreement is observed between the test data and the analytical results. Finally, it is demonstrated that the dynamic resistance capacity increases with increasing load rate and restraint stiffness and with decreasing tensile reinforcement ratio, but the larger the dynamic resistance is, the larger the plastic deformation of the structure.

scholarly journals Whey protein sweetened with Stevia rebaudiana Bertoni (Bert.) increases mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Yago Carvalho Lima ◽  
Mirian Ayumi Kurauti ◽  
Gabriel da Fonseca Alves ◽  
Jonathan Ferezini ◽  
Silvano Piovan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Whey Protein ◽  
Mitochondrial Biogenesis ◽  
Carrying Capacity ◽  
Stevia Rebaudiana ◽  
Maximum Load ◽  
Protein Supplementation ◽  
Load Carrying Capacity ◽  
Leaf Extracts ◽  
Load Carrying

Abstract Background A combination of resistance training and whey protein supplementation is a common practice among athletes and recreational exercisers to enhance muscle growth and strength. Although their safety as food additives is controversial, artificial sweeteners are present in whey protein supplements. Thus, natural sweeteners extracted from the leaves of Stevia rebaudiana are a potential alternative, due to their safety and health benefits. Here, we investigated the effects of whey protein sweetened with S. rebaudiana on physical performance and mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats. Methods Forty male Wistar rats were distributed into four groups: sedentary rats, trained rats, trained rats receiving whey protein and trained rats receiving whey protein sweetened with S. rebaudiana leaf extracts. Resistance training was performed by climbing a ladder 5 days per week, during 8-weeks. The training sessions consisted of four climbs carrying a load of 50, 75, 90, and 100% of the maximum load-carrying capacity which we determined before by performing a maximum load-carrying test for each animal. After this period, we collected plasma and tissues samples to evaluate biochemical, histological and molecular (western blot) parameters in these rats. Results Dietary supplementation with whey protein sweetened with S. rebaudiana significantly enhanced the maximum load-carrying capacity of resistance-trained rats, compared with non-sweetened whey protein supplementation. This enhanced physical performance was accompanied by an increase in the weight of the gastrocnemius and soleus muscle pads. Although the muscle pad of the biceps brachii was not altered, we observed a significant increase in PGC-1α expression, which was followed by a similar pattern in TFAM protein expression, two important mitochondrial biogenesis markers. In addition, a higher level of AMPK phosphorylation was observed in these resistance-trained rats. Finally, supplementation with whey protein sweetened with S. rebaudiana also induced a significant decrease in retroperitoneal adipocyte diameter and an increase in the weight of brown adipose tissue pads in resistance-trained rats. Conclusion The addition of Stevia rebaudiana leaf extracts to whey protein appears to be a potential strategy for those who want to increase muscular mass and strength and also improve mitochondrial function. This strategy may be useful for both athletes and patients with metabolic disorders, such as obesity and type 2 diabetes.

Applicability of Net-Section Collapse Load Approach to Maximum Load Predictions of Multiple Circumferential Cracked Pipes: Numerical Study

2015 ◽  
Author(s):  
Myeong-Woo Lee ◽  
Seung-Jae Kim ◽  
So-Dam Lee ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Numerical Method ◽  
Test Data ◽  
Numerical Study ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Collapse Load ◽  
Crack Geometry ◽  
Large Sets ◽  
Load Carrying

To estimate maximum load-carrying capacity of pipes with multiple circumferential cracks, the net-section collapse load approach has been proposed. Although the proposed method has been validated against pipe test data, experimental data are quite limited due to large sets of variables to be considered. In this paper, a numerical method is proposed to generate virtual pipe test data with wide ranges of crack geometry and interspacing. To get confidence of the proposed numerical method, it is firstly applied to simulate existing 4-inch diameter schedule 80 pipes with two circumferential cracks. Predicted maximum loads agree well with experimental data. Then the proposed method is applied to generate maximum loads for wider ranges of crack geometry and loading conditions. It is found that the net-section collapse load approach works well for all cases considered.

Determining maximum load carrying capacity of planar flexible-link robot: closed-loop approach

Robotica ◽  
2010 ◽  
Vol 28 (7) ◽  
pp. 959-973 ◽  
Author(s):  
M. H. Korayem ◽  
R. Haghighi ◽  
A. H. Korayem ◽  
A. Nikoobin ◽  
A. Alamdari
Keyword(s):  
Carrying Capacity ◽  
Closed Loop ◽  
Sliding Mode ◽  
Maximum Load ◽  
Open Loop ◽  
Nonlinear Observer ◽  
Flexible Manipulator ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYMaximum load carrying capacity (MLCC) of flexible robot manipulators is computed based on closed-loop approach. In open-loop approach, controller is not considered, so the end effector deviation from the predefined path is significant and the accuracy constraint restrains the maximum payload before actuators go into saturation mode. In order to improve the MLCC, a method based on closed-loop strategy is presented. Since in this case the accuracy is improved the actuators constraint is not a major concern and full power of actuators can be used. Since controller can play an important role in improving the maximum payload, a sliding mode based partial feedback linearization controller is designed. Furthermore, a fuzzy variable layer is used in sliding mode design to boost the performance of the controller. However, the control strategy required measurements of elastic variables velocity that are not conveniently measurable. So a nonlinear observer is designed to estimate these variables. Stability analysis of the proposed controller and state observer are performed on the basis of Lyapunov's direct method. In order to verify the effectiveness of the presented method, simulation is done for a two-link flexible manipulator. The obtained maximum payload in open-loop and closed-loop cases is compared and the superiority of the method is illustrated and the results are discussed.

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