Monitoring structures using long gauge length fibre optic sensors

2007 ◽  
Vol 34 (3) ◽  
pp. 422-429 ◽  
Author(s):  
R C Tennyson ◽  
N Banthia ◽  
E Rivera ◽  
S Huffman ◽  
I Sturrock
Keyword(s):  
Thermal Loading ◽  
Structural Integrity ◽  
Local Strain ◽  
Gauge Length ◽  
Fibre Optic ◽  
Hoop Strain ◽  
Concrete Girders ◽  
Bending Strain ◽  
Bond Interface ◽  
Beam Type

Long gauge length fibre optic sensors have been installed on bridges and pipelines to monitor their long-term structural integrity. These sensors measure the average displacement or strain over their gauge length due to mechanical or thermal loading. It is shown that long gauge length sensors can provide an estimate of the maximum bending strain for beam-type structures, such as bridge girders or pipelines, subject to sag. Bending and hoop strain test results are presented for bridges with composite reinforcements bonded to concrete girders and columns that were statically loaded at various locations to assess the integrity of the bond interface. These sensors can also provide information on corrosion-induced wall thinning of pipelines based on changes in the local strain field due to internal pressure in the line. Test data are presented for measuring pipeline corrosion using different fibre optic sensor configurations.Key words: fibre optic sensors, bridges, pipelines, integrity monitoring.

On the Design of Contact Member Surface Shape of Bolted Joints to Minimize Clamping Load Loss

2018 ◽  
Author(s):  
Linbo Zhu ◽  
Yifei Hou ◽  
Abdel-Hakim Bouzid ◽  
Jun Hong
Keyword(s):  
Contact Surface ◽  
High Performance ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Bolted Joints ◽  
Surface Shape ◽  
Geometrical Shape ◽  
Joint Surfaces ◽  
Joint Contact ◽  
The Stability

Metal to metal contact between joint surfaces is widely used in bolted joints to obtain a rigid and a high performance connection. However, a significant amount of clamping load is lost when the joint is subjected to mechanical and thermal loading including creep and fatigue. In practice, to prevent bolt loosening, additional parts such as spring washers, double nut, spring lock washers, Nyloc nut and so on are used. Those methods are costly and influence the stability of the joint and affect its structural integrity. It is well established that a small compression displacement in clamping parts leads to a big clamping load loss in stiff joints. This paper discusses the relationship between connection stiffness and clamping load and presents a method that improves clamping load retention during operation by a careful design of the member contact surface shape. A single bolted joint with two clamping parts is modeled using finite element method (FEM). A method is proposed to obtain a specific stiffness by an optimized geometrical shape of the joint contact surfaces. The result shows that the contact surface shape based on a gradually varying gap can improve the retention of the initial clamping load. Furthermore, a formula of the connection stiffness based on the curve fitting technique is proposed to predict residual clamping load under different external load and loosening.

Mechanical Analysis for Thermal Grease Enhanced Modules Enclosing a Silicon Chip

1989 ◽  
Vol 111 (2) ◽  
pp. 90-96 ◽  
Author(s):  
P. A. Engel ◽  
D. H. Strope ◽  
T. E. Wray
Keyword(s):  
Heat Conduction ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Mechanical Analysis ◽  
Mechanical Stresses ◽  
Ceramic Technology ◽  
Cyclic Thermal Loading ◽  
Thermal Grease

In metallized ceramic technology substantial mechanical stresses arise in assembly, insertion and cyclic thermal loading of thermally enhanced modules. This paper describes some experimental and analytical investigations performed for safeguarding the structural integrity of modules in which heat conduction from the chip to the module cap was enhanced by a “thermal grease” compound.

Bone-Integrated Optical Microlasers for In-Vivo Diagnostic Biomechanical Performances

2019 ◽  
Author(s):  
Omar Cavazos ◽  
Maurizio Manzo ◽  
Erick Ramírez-Cedillo ◽  
Hector R. Siller
Keyword(s):  
Structural Integrity ◽  
Diagnostic Technique ◽  
Local Strain ◽  
Daily Basis ◽  
Sensing Element ◽  
Optical Resonances ◽  
Whispering Gallery ◽  
Integrated Optical ◽  
Working Principle

Abstract Bones experience mechanical loads on a daily basis. It is difficult to obtain biomechanical performances in-vivo measurements. When implants are integrated with bones after surgery, especially in aged individuals, their osseointegration can compromise the structural integrity of bones; for this reason, it is important to monitor the evolution of the mechanical properties of bones with some in-vivo diagnostic technique. In this study, we propose to integrate optical microsensing devices into bones. To simulate the working principle, a sensor is integrated with a 3-D printed bone. The sensing element is a dye-doped optical microlaser based on the morphology dependent resonance (MDR) shifts also called the whispering gallery mode phenomenon (WGM). When the microlaser is excited by a light source, the fluorescence from the dye couples with the optical resonances. These optical resonances are very sensitive to any perturbation of the microlasers’s morphology. Therefore, the local strain variation of the bone can be related to the shift of the optical resonances. This in-vivo technique monitors the biomechanical performance of bones with implants and prosthetics.

Protection Against Local Failure for Impulsively Loaded Vessels

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Alan M. Clayton ◽  
Thomas A. Duffey
Keyword(s):  
Damage Mechanics ◽  
Local Strain ◽  
Pressure Vessels ◽  
Local Failure ◽  
Hoop Strain ◽  
Direct Extension ◽  
Asme Code ◽  
Section Viii ◽  
Shell Geometry ◽  
Static And Dynamic Loading

Significant changes have been incorporated in design limits for pressurized vessels in Section VIII, Division 3 of the ASME Code, starting in 2007. There is now a local damage-mechanics based strain-exhaustion limit as well as a separate global plastic collapse limit. In addition, Code Case 2564 (Sec. VIII, Div 3) has recently been approved to address impulsively loaded vessels. Recent studies (Nakamura, T., Kaguchi, H., and Kubo, S., 2000, “Failure Strain of Thin Cylindrical Vessel Subjected to Dynamic Internal Pressure,” Design and Analysis of Pressure Vessels and Piping, Vol. 399, R. Baliga, ed., pp. 47–54 and Duffey, T. A., 2011, “Plastic Instabilities in Spherical Vessels for Static and Dynamic Loading,” ASME J. Pressure Vessel Technol., 133(5), p. 051210) have shown that local strain limits play a particularly important role for these impulsively loaded vessels. In this paper, the new local strain-exhaustion procedure, originally intended for static-pressure-loaded vessels, is evaluated for adequacy in conservatively predicting failure for impulsively loaded vessels. Based upon symmetrically loaded cylindrical shell geometry, it is found that direct extension of the new local failure rules in the ASME Code to impulsively loaded vessels is unconservative. However, a hoop-strain local failure criterion predicts failures reasonably well.

Fracture Assessment for Pressurized Water Reactor Vessel Nozzles Subjected to Pressure and Thermal Loading

2021 ◽  
Author(s):  
Qibao Chu ◽  
Qing Wang ◽  
Yonggang Fang ◽  
Wei Tan
Keyword(s):  
Crack Front ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Safety Margin ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Integrity Assessment ◽  
Main Challenge ◽  
Fracture Assessment ◽  
3D Finite Element Method

Abstract To ensure the structure integrity of the RPV, the main challenge is the embrittlement of beltline material. However, the stress of inlet or outlet nozzles of the RPV which are in general reinforced in comparison with the beltline, is more complex especially under the thermal loads. In recently studies, a lot of works have been done to show that the nozzle region may be more challenging under some conditions. In this paper, a fracture assessment for the RPV nozzles subjected to pressure and thermal loading is discussed using the software ABAQUS 6.12 and Zen Crack 7.9-3. It includes: SIF calculation based on 3D finite element method; structural integrity assessment under a typical LOCA transient; and the fatigue crack growth evaluation under cyclic loading situations. The results show that the SIF along the crack front is obviously asymmetric, and only to assess the safety of the deepest point along the crack front in the ASME and RCC-MR codes may be reconsider. If the KIa criteria is applied, under a typical LOCA transient, it is difficult to obtain an effective fracture safety margin for a 1/4 thickness crack, while based on the KIC criteria, the nozzle is shown to be safe in the case study. The shape of the surface elongated crack (which is often easily produced in the nozzle area) tends to be circle under the cyclic pressure loading situation which shows the crack shape assumed in the ASME and RCC-MR codes is reasonable.

Protective Barrier Wall Response to Sequential Blast and Fire Events

2021 ◽  
Author(s):  
Hunter Smith
Keyword(s):  
Thermal Loading ◽  
Structural Integrity ◽  
High Stress ◽  
Wall Structure ◽  
Element Analysis ◽  
Linear Dynamic ◽  
Extreme Load ◽  
Wall Panels ◽  
Non Linear ◽  
Barrier Wall

Abstract Blast and fire-resistant barrier walls are often required on offshore platforms to protect from accidental events. A wall structure designed for a probabilistic explosion event typically relies on inelastic response and plastic deformation to maintain a lightweight, efficient design. Design guides for such structures do not explicitly address how to account for the effects of interaction of blast and fire loading on structural performance and design acceptance criteria. If a wall assembly is required to provide rated fire and gas protection after an explosion event, it is generally assumed that structural integrity is maintained due to temperature increase limits (140°C) from the H-60/120 rated fire protection on the wall. This paper investigates the validity of this assumption for a typical offshore barrier wall designed to undergo permanent deformation during an initial blast event. The study was performed utilizing non-linear dynamic finite element analysis (FEA). FEA allows for design iteration, structural assessment, and validation against extreme load scenarios when testing of full-scale assembly may not be feasible. A typical wall structure was first analyzed for blast loading by non-linear dynamic structural analysis. Thermal loading from a subsequent hydrocarbon fire was then applied to observe the structural response in the post-blast damaged condition. Based on the rated temperature range, the resulting thermal expansion in the wall panels induces large stresses at the interface between wall panels and supporting steel. Non-linear FEA confirmed that yielding occurs which may increase existing plastic strains beyond design limits at locations of high stress concentration. Therefore, it is prudent to consider thermal performance in the design process, especially regarding connections and penetrations.

Protection Against Local Failure for Impulsively Loaded Vessels

2013 ◽  
Author(s):  
Alan M. Clayton ◽  
Thomas A. Duffey
Keyword(s):  
Damage Mechanics ◽  
Static Pressure ◽  
Local Strain ◽  
Local Failure ◽  
Hoop Strain ◽  
Direct Extension ◽  
Asme Code ◽  
Section Viii ◽  
Shell Geometry ◽  
Made In

Significant changes were recently made in design limits for pressurized vessels in Section VIII, Division 3 of the ASME Code. There is now a local damage-mechanics based strain-exhaustion limit as well as a separate global plastic collapse limit. In addition, Code Case 2564 (Sec VIII, Div 3) has recently been approved to address impulsively loaded vessels. Recent studies have shown that local strain limits play a particularly important role for these impulsively loaded vessels. In this paper, the new local strain-exhaustion procedure, originally intended for static-pressure-loaded vessels, is evaluated for adequacy in conservatively predicting failure for impulsively loaded vessels. Based upon a symmetrically loaded cylindrical shell geometry, it is found that direct extension of the new local failure rules in the ASME Code to impulsively loaded vessels is unconservative. However, a hoop-strain local failure criterion predicts failures reasonably well.

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