Buckling of Stiffened Panels and Its Mitigation

2014 ◽  
Vol 30 (04) ◽  
pp. 201-206
Author(s):  
N. R. Mandal ◽  
Sree Krishna Prabu ◽  
Sharat Kumar
Keyword(s):  
Process Control ◽  
High Speed ◽  
Control Method ◽  
Plate Thickness ◽  
Control Measures ◽  
Thin Plates ◽  
Welding Distortion ◽  
Stiffened Panels ◽  
Distortion Control ◽  
Buckling Distortion

The increased use of thin plates, like in ships for high-speed operation, results in significantly increased distortion. In-process control of welding distortion is more desirable than post welding rectification from the point of manufacturing efficiency. This can be achieved by suitably designing and also implementing one or more of the distortion control measures as is suitable for a particular manufacturing situation. In this study, an investigation on buckling phenomenon in fabrication of stiffened panels was carried out. Analytical formulae were used to calculate the weld-induced compressive stresses. Critical buckling stresses considering appropriate buckling coefficient for typical stiffened panels as used in shipbuilding practice were calculated. The predictions from these analytical tools were compared with experimental observations. The experimental results compared fairly well with those of the calculated ones. In the present study the panel design aspect as well as thermomechanical tensioning scheme were studied with regard to buckling mitigation. It was observed that when choosing suitable stiffener spacing in conjunction with plate thickness, buckling distortion can be significantly reduced. Distortion mitigation through thermomechanical tensioning was also found to an effective yet simple-to-implement method of buckling distortion control. However, further investigation is necessary toward fully establishing the method of thermomechanical tensioning. Once this method is established, this pre-tensioning technique can be applied as an active in-process control method to avoid buckling distortion in stiffened panels.

A Proper Groove Design for Distortion Control of the Multi-Pass Weldment at Pressure Vessel

2003 ◽  
Author(s):  
Sung-Yun Kim ◽  
Sang-Beom Shin ◽  
Ha-Geun Kim
Keyword(s):  
Pressure Vessel ◽  
Plate Thickness ◽  
Angular Distortion ◽  
Welding Distortion ◽  
Bending Rigidity ◽  
Element Analysis ◽  
Predictive Equations ◽  
Groove Design ◽  
Distortion Control ◽  
Shrinkage Force

The purpose of this study is to establish a proper groove design for multi-pass butt weldment with narrow groove of pressure vessel to control welding distortion. To do it, the behavior of angular distortion and longitudinal shrinkage force of the simple butt weldment were evaluated using a finite element analysis and experiment. The effective bending rigidity of the multi pass butt weldment with welding pass was defined as a function of the effective thickness of weld throat. Based on the results, the predictive equations for the welding distortion of the multi-pass both side weldment were established as function of heat input and effective bending/in-plane rigidity of the weldment. Using the equation, a proper ratio of the groove height can be determined to control the distortion for the multipass both side weldment with reference to various groove shape and plate thickness.

Welding Distortion Simulation of Large Stiffened Plate Panels

2008 ◽  
Vol 24 (01) ◽  
pp. 50-56
Author(s):  
Pankaj Biswas ◽  
N. R. Mandal
Keyword(s):  
Structural Integrity ◽  
Plate Thickness ◽  
Welding Current ◽  
Fusion Welding ◽  
Welding Distortion ◽  
Element Analysis ◽  
Stiffened Panels ◽  
Analysis Methodology ◽  
Current Voltage ◽  
Plate Panels

Fusion welding leads to heat-induced distortion. These deformations may adversely affect the structural integrity and subsequent alignment of the adjacent panels. The extent of distortion depends on several parameters such as welding speed, plate thickness, welding current, voltage, restraints applied to the job while welding, as well as sequence of welding. Welding being a transient phenomenon, finite element analysis of large stiffened panels is virtually not possible. In the present work, an analysis methodology based on the quasi-stationary nature of welding and the resulting symmetric behavior of the stiffened panels has been developed for studying the distortion pattern of orthogonally stiffened large plate panels. The effect of filler metal deposition has been taken into account by implementing element birth and death technique. The numerical model yielded results comparing well with the ex- perimental results.

Practical Welding Techniques to Minimize Distortion in Lightweight Ship Structures

2005 ◽  
Author(s):  
C. Conrardy ◽  
T. D. Huang ◽  
D. Harwig ◽  
P. Dong ◽  
L. Kvidahl ◽  
...  
Keyword(s):  
Best Practices ◽  
Heat Input ◽  
Steel Structures ◽  
Welding Distortion ◽  
Manufacturing Cost ◽  
Welding Operation ◽  
Welding Heat Input ◽  
Distortion Control ◽  
Thin Steel ◽  
Buckling Distortion

The trend in both military and commercial shipbuilding is the increased use of thin steel to reduce weight and improve performance. Complex panel structures have thickness transitions for weight and structural optimization with multiple inserts ranging from 5 to 45 mm. Welding practices developed for thicker plate can result in significant out-of-plane distortion when applied to thin-plate structures. Buckling distortion of complex lightweight panels has resulted in a significant negative effect on manufacturing cost and production throughput, limiting the shipbuilders’ ability to produce innovative ship designs. High fitting and welding costs are the consequence of this large welding distortion. This problem is exacerbated as the fairness requirements are tightened. New methods are needed to control distortion when welding thinner materials. To tackle the distortion problems, in 2002 Northrop Grumman Ship Systems initiated a multiyear program to develop distortion-control technology for complex panels. This paper reports the results of a study to develop “best practices” for welding of lightweight structures. Control of welding distortion for thin structures requires control of each welding operation from butt-welding of plates through to unit assembly. A general philosophy was applied to minimize welding heat input while maximizing restraint during unit construction. To achieve this, the following techniques were evaluated: * Increasing restraint during each welding operation, * Improving fitting practice, * Weld sequencing and, * Minimizing welding heat input. * Additionally, an active distortion mitigation approach, known as Transient Thermal Tensioning, was investigated for reduction of buckling distortion during thin-panel longitudinal stiffener welding. A series of tests were performed to evaluate various distortion control approaches and to optimize production processes. The culmination of the project will involve demonstrating best practices in the production of thin steel structures. A plan is also being developed for implementing the most advantageous approaches into production.

Practical Welding Techniques to Minimize Distortion in Lightweight Ship Structures

2006 ◽  
Vol 22 (04) ◽  
pp. 239-247 ◽  
Author(s):  
C. Conrardy ◽  
T.D. Huang ◽  
D. Harwig ◽  
P. Dong ◽  
L. Kvidahl ◽  
...  
Keyword(s):  
Best Practices ◽  
Heat Input ◽  
Steel Structures ◽  
Welding Distortion ◽  
Manufacturing Cost ◽  
Welding Operation ◽  
Welding Heat Input ◽  
Distortion Control ◽  
Thin Steel ◽  
Buckling Distortion

The trend in both military and commercial shipbuilding is the increased use of thin steel to reduce weight and improve performance. Complex panel structures have thickness transitions for weight and structural optimization with multiple inserts ranging from 5 to 45 mm. Welding practices developed for thicker plate can result in significant out-of-plane distortion when applied to thin-plate structures. Buckling distortion of complex lightweight panels has resulted in a significant negative effect on manufacturing cost and production throughput, limiting the shipbuilders' ability to produce innovative ship designs. High fitting and welding costs are the consequence of this large welding distortion. This problem is exacerbated as the fairness requirements are tightened. New methods are needed to control distortion when welding thinner materials. To tackle the distortion problems, in 2002 Northrop Grumman Ship Systems initiated a multiyear program to develop distortion-control technology for complex panels. This paper reports the results of a study to develop "best practices" for welding of lightweight structures. Control of welding distortion for thin structures requires control of each welding operation from butt welding of plates through to unit assembly. A general philosophy was applied to minimize welding heat input while maximizing restraint during unit construction. To achieve this, the following techniques were evaluated: increasing restraint during each welding operation, improving fitting practice, weld sequencing, and minimizing welding heat input. Additionally, an active distortion mitigation approach, known as transient thermal tensioning, was investigated for reduction of buckling distortion during thin-panel longitudinal stiffener welding. A series of tests were performed to evaluate various distortion control approaches and to optimize production processes. The culmination of the project will involve demonstrating best practices in the production of thin-steel structures. A plan is also being developed for implementing the most advantageous approaches into production.

scholarly journals A Critical Review of Supersonic Flow Control for High-Speed Applications

2021 ◽  
Vol 11 (15) ◽  
pp. 6899
Author(s):  
Abdul Aabid ◽  
Sher Afghan Khan ◽  
Muneer Baig
Keyword(s):  
Supersonic Flow ◽  
Flow Control ◽  
Active Control ◽  
Critical Review ◽  
High Speed ◽  
Passive Control ◽  
Control Method ◽  
Sudden Expansion ◽  
Control Approach ◽  
Cost Efficient

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

scholarly journals Design and validation of an MPC controller for CMG-based testbed

2021 ◽  
Author(s):  
Matteo Facchino ◽  
Atsushi Totsuka ◽  
Elisa Capello ◽  
Satoshi Satoh ◽  
Giorgio Guglieri ◽  
...  
Keyword(s):  
Predictive Control ◽  
Attitude Control ◽  
High Speed ◽  
Control Method ◽  
Input Constraints ◽  
Virtual Reference ◽  
Control Moment ◽  
Pyramidal Configuration ◽  
Actuation Systems ◽  
Constraints Satisfaction

AbstractIn the last years, Control Moment Gyros (CMGs) are widely used for high-speed attitude control, since they are able to generate larger torque compared to “classical” actuation systems, such as Reaction Wheels . This paper describes the attitude control problem of a spacecraft, using a Model Predictive Control method. The features of the considered linear MPC are: (i) a virtual reference, to guarantee input constraints satisfaction, and (ii) an integrator state as a servo compensator, to reduce the steady-state error. Moreover, the real-time implementability is investigated using an experimental testbed with four CMGs in pyramidal configuration, where the capability of attitude control and the optimization solver for embedded systems are focused on. The effectiveness and the performance of the control system are shown in both simulations and experiments.

High Speed Impact Behaviour of Thermo-Mechanically Processed AA 6082-T6 Thin Plates

2018 ◽  
Vol 5 (9) ◽  
pp. 17203-17212 ◽  
Author(s):  
Rahul Dubey ◽  
Srinivasa Rakesh ◽  
R Velmurugan ◽  
R Jayaganthan
Keyword(s):  
High Speed ◽  
Thin Plates ◽  
Impact Behaviour ◽  
High Speed Impact

Multimode Adaptive Control for Tank Gun Control System Based on Tracking Differentiator

2011 ◽  
Vol 383-390 ◽  
pp. 79-85
Author(s):  
Dong Yuan ◽  
Xiao Jun Ma ◽  
Wei Wei
Keyword(s):  
Adaptive Control ◽  
Control System ◽  
High Speed ◽  
Control Method ◽  
Reference Model ◽  
Gun Control ◽  
Math Model ◽  
Tracking Differentiator ◽  
Switch Control ◽  
Model Reference Adaptive

Aiming at the problems such as switch impulsion, insurmountability for influence caused by nonlinearity in one tank gun control system which adopts double PID controller to realize the multimode switch control between high speed and low speed movement, the system math model is built up; And then, Model Reference Adaptive Control (MRAC) method based on nonroutine reference model is brought in and the adaptive gun controller is designed. Consequently, the compensation of nonlinearity and multimode control are implemented. Furthermore, the Tracking Differentiator (TD) is affiliated to the front of controller in order to restrain the impulsion caused by mode switch. Finally, the validity of control method in this paper is verified by simulation.

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