Experimental Investigations on ThermoMechanical Tensioning (TMT), comparison with Heat Sink, and Its Application to a Grillage Structure

2020 ◽  
pp. 1-8
Author(s):  
Amith Gadagi ◽  
Nisith Ranjan Mandal ◽  
Om Prakash Sha ◽  
Sharat Kumar ◽  
Sanyappa Pujari ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Control Mechanism ◽  
Thin Plates ◽  
Experimental Investigations ◽  
Ship Structures ◽  
Buckling Strength ◽  
Distortion Control ◽  
Out Of Plane ◽  
Transverse Welds ◽  
Heat Sinking

Thin plates, which are widely used in ship structures, undergo weld-induced buckling distortions because of their lower critical buckling strength. Thus, there is a need for an active in-process distortion control mechanism in the welding involving thin plates. In this regard, a ThermoMechanical Tensioning (TMT) method was developed and implemented successfully. In the current work, experimental investigation of the effect of TMT pull on the resulting welding distortions is studied and also the TMT process is compared with a heat sinking technique. The experimental results indicate that an increase in the TMT pull would reduce the extent of weld-induced buckling distortions. The results also suggest that a complicated heat sinking technique can be effectively replaced by a TMT process in reducing the welding out-of-plane distortions. The concept of TMT is further extended to the fabrication of grillage structures used in ship structures, which includes longitudinal and transverse welds.

scholarly journals Locally Corroded Stiffener Effect on Shear Buckling Behaviors of Web Panel in the Plate Girder

2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Jungwon Huh ◽  
In-Tae Kim ◽  
Jin-Hee Ahn
Keyword(s):  
Corrosion Damage ◽  
Element Analysis ◽  
Buckling Strength ◽  
Lower Shear ◽  
Out Of Plane ◽  
Shear Buckling ◽  
Buckling Failure ◽  
Plane Displacement ◽  
The Web ◽  
Plate Girder

The shear buckling failure and strength of a web panel stiffened by stiffeners with corrosion damage were examined according to the degree of corrosion of the stiffeners, using the finite element analysis method. For this purpose, a plate girder with a four-panel web girder stiffened by vertical and longitudinal stiffeners was selected, and its deformable behaviors and the principal stress distribution of the web panel at the shear buckling strength of the web were compared after their post-shear buckling behaviors, as well as their out-of-plane displacement, to evaluate the effect of the stiffener in the web panel on the shear buckling failure. Their critical shear buckling load and shear buckling strength were also examined. The FE analyses showed that their typical shear buckling failures were affected by the structural relationship between the web panel and each stiffener in the plate girder, to resist shear buckling of the web panel. Their critical shear buckling loads decreased from 82% to 59%, and their shear buckling strength decreased from 88% to 76%, due to the effect of corrosion of the stiffeners on their shear buckling behavior. Thus, especially in cases with over 40% corrosion damage of the vertical stiffener, they can have lower shear buckling strength than their design level.

scholarly journals Influence of Gradual Damage on the Structural Dynamic Behaviour of Composite Rotors: Experimental Investigations

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2421 ◽  
Author(s):  
Angelos Filippatos ◽  
Maik Gude
Keyword(s):  
Mechanical Properties ◽  
Composite Structures ◽  
Dynamic Behaviour ◽  
Experimental Investigations ◽  
Catastrophic Failure ◽  
Structural Dynamic ◽  
Delamination Growth ◽  
Reinforced Composite ◽  
Out Of Plane ◽  
Effective Mechanical Properties

Fibre-reinforced composite structures subjected to complex loads exhibit gradual damage behaviour with the degradation of the effective mechanical properties and changes in their structural dynamic behaviour. Damage manifests itself as a spatial increase in inter-fibre failure and delamination growth, resulting in local changes in stiffness. These changes affect not only the residual strength but, more importantly, the structural dynamic behaviour. In the case of composite rotors, this can lead to catastrophic failure if an eigenfrequency coincides with the rotational speed. The description and analysis of the gradual damage behaviour of composite rotors, therefore, provide the fundamentals for a better understanding of unpredicted structural phenomena. The gradual damage behaviour of the example composite rotors and the resulting damage-dependent dynamic behaviour were experimentally investigated under propagating damage caused by a combination of out-of-plane and in-plane loads. A novel observation is the finding that a monotonic increase in damage results in a non-monotonic frequency shift of a significant number of eigenfrequencies.

scholarly journals The practice of experimental investigations of lexical tones in Baltic subdialects: some of the new insights in methodology

2020 ◽  
pp. 1-19
Author(s):  
Evaldas Švageris
Keyword(s):  
Experimental Investigation ◽  
Methodological Approach ◽  
Main Idea ◽  
Experimental Investigations ◽  
Lexical Tone ◽  
Mathematical Functions ◽  
Combined Analysis ◽  
Lexical Tones ◽  
Acoustic Correlates ◽  
The Baltic

This article provides an alternative way of experimental investigation of lexical tones in the Baltics. The main idea holds on a presupposition that the phonetic basis of prosodic elements in question can be explained in a more appropriate way in terms of a combined analysis of acoustic correlates, rather than a selective one. The lexical tone in this case may be interpreted as a factor which determines the type of acoustic correlation. Ideally, the interdependence of that sort could be defined by mathematical functions. The analysis of the empirical basis provides clear evidence in the favour of such methodological approach. Phonetic data from both, the Latvian (Valmiera) and the Lithuanian (North Žemaitian) subdialects confirmed clearly that the highest level of the tone distinction can be reached by a combined analysis of the pitch slope, pitch jerk and the duration of the long accented vowels. These results have arguably improved the interpretation of the phonetic tone structure and shed a new light on the typological links between the Baltic dialects. Finally, it presupposes that the phonetic nature of prosodic elements in some degree depends on a methodological way we choose for the investigational purposes. 

Engineering and Production Technology for Lightweight Ship Structures, Part II: Distortion Mitigation Technique and Implementation

2007 ◽  
Vol 23 (02) ◽  
pp. 82-93 ◽  
Author(s):  
T. D. Huang ◽  
C. Conrardy ◽  
P. Dong ◽  
P. Keene ◽  
L. Kvidahl ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Steel Structures ◽  
Critical Parameters ◽  
Battelle Memorial Institute ◽  
Functional Requirements ◽  
Ship Structures ◽  
Distortion Control ◽  
Us Navy ◽  
Thin Steel ◽  
Buckling Distortion

Shipboard applications of lightweight structures have increased over recent years in both military and commercial vessels. Thin steel reduces topside weight, enhances mission capability, and improves performance and vessel stability, but the propensity of buckling distortion has increased significantly. At present, several US Navy construction programs are experiencing high rates of buckling distortion on thin steel structures. The standard shipyard practice of fabricating stiffened steel panels by arc welding is one of the major contributors to this distortion. Correcting the distortion is a necessary but time-consuming operation that adds no value and ultimately tends to degrade the quality of the ship structure. With a major initiative funded by the US Navy, Northrop Grumman Ship Systems (NGSS) has undertaken a comprehensive assessment of lightweight structure fabrication technology since 2002. Through collaborative research, significant progress has been achieved in the development of distortion-control techniques. Reverse arching, transient thermal tensioning (TTT), stiffener assembly sequencing, and other preferred manufacturing techniques were developed at NGSS to reduce distortion and eliminate the high rework costs associated with correcting that distortion. Complex lightweight panel structures, which are reinforced by long slender stiffeners along with numerous cutouts and inserts, pose a major challenge for distortion control. The geometric complexity yields a more complicated buckling behavior, which drives the need to develop a more fine-tuned finite element model to determine critical parameters and heating patterns for the TTT process. NGSS has recently teamed with Edison Welding Institute (EWI), Battelle Memorial Institute, and the University of New Orleans on a Navy project to further refine TTT procedures for complex lightweight ship structures. In this paper, functional requirements and the design of TTT process and production equipment are discussed. The refined TTT process will be benchmarked by the test panel observations, and a laser scanning device, LIDAR, will be used to analyze panel distortion topography.

Design Guidelines for Doubler Plate Repairs of Ship Structures

2005 ◽  
Author(s):  
Pradeep K. Sensharma ◽  
Malcolm Willis ◽  
Aaron Dinovitzer ◽  
Nat Nappi
Keyword(s):  
Engineering Design ◽  
Low Cost ◽  
Design Guidelines ◽  
Performance Data ◽  
Ship Structures ◽  
Buckling Strength ◽  
Relative Ease ◽  
Fatigue And Fracture ◽  
Fracture Assessment ◽  
Design Guidance

The use of doubler plates or ‘doublers’ has become routine for temporary ship repairs. It is the preferred method for ships’ structural repairs for plate corrosion due to its relative ease and low cost of installation over the more costly permanent welded plate insert repair. A lack of performance data and engineering design guidance are the reasons that repairs with doublers are currently considered only temporary. This objective of this study was to develop a set of guidelines for designing and applying doubler plate repairs to ship structures. The guidelines were established using the following criteria: various stress analyses, buckling strength, corrosion types and rates, weld types, and doubler plate fatigue and fracture assessment. Studying and understanding doubler plate repair performance by comparison to that of the primary hull performance allows critical operational decisions to be made with greater ease and confidence. However, the ultimate goal of this study was to establish the design and limitations on the applications of doubler plate repairs for surface ships.

scholarly journals Detection of debonding in adhesive joints using Lamb wave propagation

2019 ◽  
Vol 262 ◽  
pp. 10012
Author(s):  
Magdalena Rucka ◽  
Erwin Wojtczak ◽  
Jacek Lachowicz
Keyword(s):  
Wave Propagation ◽  
Lamb Waves ◽  
Visual Assessment ◽  
Guided Wave ◽  
Steel Plates ◽  
Experimental Investigations ◽  
Mechanical Degradation ◽  
Adhesively Bonded ◽  
Destructive Testing ◽  
Out Of Plane

Adhesively bonded joints are widely used in many branches of industry. Mechanical degradation of this type of connections does not have significant symptoms that can be noticed during visual assessment, so non-destructive testing becomes a very important issue. The paper deals with experimental investigations of adhesively bonded steel plates with different defects. Five samples (an intact one and four with damages in the form of partial debonding) were prepared. The inspection was conducted with the use of guided wave propagation method. Lamb waves were excited at one point of the sample, whereas the out-of-plane velocity signals were recorded in a number of points spread over the area of overlap. The processing of signals consisted of calculations of weighted root mean square (WRMS). The results of the analysis showed that the WRMS maps allow for identification and determination of size and shape of debonding areas.

scholarly journals Experimental investigations of the performance of a thermoacoustic electricity generator

2019 ◽  
Vol 116 ◽  
pp. 00025
Author(s):  
Ahmed Hamood ◽  
Artur Jaworski
Keyword(s):  
Experimental Investigation ◽  
Acoustic Wave ◽  
Load Resistance ◽  
Experimental Investigations ◽  
The Novel ◽  
Working Medium ◽  
Linear Alternator ◽  
Mean Pressure ◽  
Set Up ◽  
Working Parameters

This paper presents the experimental investigation of a two-stage thermoacoustic electricity generator able to convert heat at the temperature of the exhaust gases of an internal combustion into useful electricity. The novel configuration is one wavelength and consists of two identical stages. The identical stages will have out of phase acoustic wave at similar amplitudes which allows coupling a linear alternator to run in push-pull mode. The experimental set-up is 16.1 m long and runs at 54.7 Hz. The working medium is helium at 28 bar. The maximum generated electric power is 73.3 W at 5.64% thermal-to-electric efficiency. The working parameters including load resistance, mean pressure and heating power were investigated.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: Computational Approach

2007 ◽  
Author(s):  
Satoshi Tsunoi ◽  
Akira Mikami ◽  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Analytical Model ◽  
Failure Modes ◽  
Experimental Investigations ◽  
Seismic Load ◽  
Piping System ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Seismic Loadings ◽  
Local Wall Thinning

The authors have proposed an analytical model by which they can simulate the dynamic and failure behaviors of piping systems with local wall thinning against seismic loadings. In the previous paper [13], the authors have carried out a series of experimental investigations about dynamic and failure behaviors of the piping system with fully circumferential 50% wall thinning at an elbow or two elbows. In this paper these experiments have been simulated by using the above proposed analytical model and investigated to what extent they can catch the experimental behaviors by simulations.

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