Stress Loss of Pre-Tensed CFRP Strips Strengthening Square RС Column

2021 ◽  
Vol 871 ◽  
pp. 321-329
Author(s):  
Zhao Qi Wu ◽  
Min Shi ◽  
Sheng Ping Wu ◽  
Hua Li ◽  
Han Liu
Keyword(s):  
Stress Concentration ◽  
Initial Stress ◽  
Experimental Test ◽  
Geometric Dimension ◽  
Confined Concrete ◽  
Cross Sectional ◽  
Cross Sectional Size ◽  
Protective Cover ◽  
Working Principle ◽  
Cfrp Strip

Pre-tensing the CFRP strip strengthening RC column can improve the strain lag of the confined concrete and avoid unloading of column in advance. The pre-stress of strip has an important influence of strengthen. Stress loss of the strip pre-tensed by using the device proposed were investigated by using an experimental test. Firstly, the reasons for the stress loss of strip were analyzed according to the working principle of the device and the strengthening procedure. Then the primary causes of the stress loss, such as friction, relaxation and removing device, were experimentally tested. The influence of the pretension, detail and sectional geometric dimension on the stress loss of the strip were studied. The results show that all three types of pre-stress losses increase significantly with the initial stress. Increasing the cross-sectional size would reduce the relaxation and unwinding losses, but it has little effect on friction losses. The influence of fillet radius on the pre-stress loss was negligible, but in order to avoid premature tearing of local CFRP caused by stress concentration, the chamfer should be made as large as possible within the thickness of concrete protective cover. The test also found that friction was the main cause of stress loss, and friction loss accounts for more than 90% of the total loss.

Infrared Diagnostics of Free Charge Carriers in Silicon Nanowires

2019 ◽  
Vol 18 (03n04) ◽  
pp. 1940030 ◽  
Author(s):  
A. I. Efimova ◽  
E. A. Lipkova ◽  
K. A. Gonchar ◽  
A. A. Eliseev ◽  
V. Yu. Timoshenko
Keyword(s):  
Silicon Nanowires ◽  
Crystalline Silicon ◽  
Free Charge Carrier ◽  
Charge Carrier Concentration ◽  
Attenuated Total Reflection ◽  
Free Charge ◽  
Cross Sectional ◽  
Text Type ◽  
Cross Sectional Size ◽  
Potential Applications

Free charge carrier concentration in arrays of silicon nanowires (SiNWs) with cross-sectional size of the order of 100[Formula: see text]nm was quantitatively studied by means of the infrared spectroscopy in an attenuated total reflection mode. SiNWs were formed on lightly-doped [Formula: see text]-type crystalline silicon substrates by metal-assisted chemical etching followed by additional doping through thermoactivated diffusion of boron at 900–1000∘C. The latter process was found to increase the concentration of free holes in SiNWs up to [Formula: see text][Formula: see text]cm[Formula: see text]. Potential applications of highly doped SiNWs in thermoelectric energy converters and infrared plasmonic devices are discussed.

scholarly journals Failure analysis of a 40 ton crane hook at a Hot Strip Mill

2018 ◽  
Vol 165 ◽  
pp. 10006 ◽  
Author(s):  
Souvik Das ◽  
Goutam Mukhopadhyay ◽  
Sandip Bhattacharyya
Keyword(s):  
Heat Treatment ◽  
Stress Concentration ◽  
Treatment Process ◽  
Fatigue Crack Initiation ◽  
Hot Strip Mill ◽  
Heat Treatment Process ◽  
Cross Sectional ◽  
Cast Structure ◽  
Hot Strip ◽  
Beach Marks

There have been accounts of repeated failure of crane hooks at the coil yard of a Hot Strip Mill which pose a serious threat to safety in the area. More than 4 hooks failed in less than 5 years. The crane hook (rated for 36000 kg) failed from the threaded shank while lifting a load of 18143 kg. The metal in the hook was revealed by chemical analysis to be killed IS: 4367 20C15 steel. The hook rod failed from a step where there was a cross sectional change and the locations were associated with machining and chatter marks. Such cross-sectional changes are the potential sites of stress concentrations leading to crack initiations. Fracture surfaces of broken pieces of hook reveal initiation of beach marks from both sides with granular rough surface at the middle of fracture zone. Beach marks initiated from both sides indicate origin of reverse bending fatigue. Distinct granular rough zone at the middle is due to final brittle fracture. Microstructure of the polished sample revealed numerous inclusions which indicate that the steel was not clean .Such a huge number of inclusions are not desirable as they can act as stress concentration sites and lead to fatigue crack initiation. Etched microstructure of failed hook reveals coarse cast structure having inhomogeneous microstructure with a mixture of ferrite and pearlite (which meant lower fatigue strength). This inhomogeneous coarser cast structure is outcome of lower reduction ratio during rolling followed by improper heat treatment process. The fracture was concluded to have occurred due to stress concentration from the step region due to inferior material (Inclusion and Improper Heat treatment process). Preventive maintenance and condition monitoring procedures should be applied to identify and minimize the risk(s) Establishment of an NDT procedure for regular basis inspection of the structural members (welded joints and hookshaped steel rods during incoming inspection and in-service).

Structural Design of a Multifunctional Morphing Fowler Flap for a Twin-Prop Regional Aircraft

2018 ◽  
Author(s):  
Francesco Rea ◽  
Francesco Amoroso ◽  
Rosario Pecora ◽  
Maria Chiara Noviello ◽  
Maurizio Arena
Keyword(s):  
Finite Element ◽  
Analysis Tool ◽  
Load Path ◽  
Element Analysis ◽  
Cross Sectional ◽  
Aerodynamic Performances ◽  
Cross Sectional Size ◽  
Elementary Methods ◽  
Minimum Number ◽  
Mode 3

In the framework of Clean Sky 2 Airgreen 2 (REG-IADP) European research project, a novel multifunctional morphing flap technology was investigated to improve the aerodynamic performances of the next Turboprop regional aircraft (90 passengers) along its flight mission. The proposed true-scale device (5 meters span with a mean chord of 0.6 meters) is conceived to replace and enhance conventional Fowler flap with new functionalities. Three different functions were enabled: overall airfoil camber morphing up to +30° (mode 1), +10°/−10° (upwards/downwards) deflections of the flap tip segment (mode 2), flap tip “segmented” twist of ±5° along the outer flap span (mode 3). Morphing mode 1 is supposed to be activated during take-off and landing only to enhance aircraft high-lift performances and steeper initial climb and descent. Thanks to this function, more airfoil shapes are available at each flap setting and therefore a dramatic simplification of the flap deployment system may be implemented. Morphing modes 2 and 3 are enabled in cruise and off-design flight conditions to improve wing aerodynamic efficiency. The novel structural concept of the three-modal morphing Fowler flap (3MMF) was designed according to the challenges posed by real wing installation issues. The proposed concept consists of a multi-box arrangement activated by segmented ribs with embedded inner mechanisms to realize the transition from the baseline configuration to different target aero-shapes while withstanding the aerodynamic loads. Lightweight and compact actuating leverages driven by electromechanical motors were properly synthesized to comply with stringent requirements for real aircraft implementation: minimum actuating torque, minimum number of motors, reduced weight, and available design space. The methodology for the kinematic design of the inner mechanisms is based on a building block approach where the instant center analysis tool is used to preliminary select the locations of the hinges’ leverages. The final geometry of the inner mechanisms is optimized to maximize the mechanical advantage as well as to provide the kinematic performances required by the three different morphing modes. The load-path was evaluated, and the cross-sectional size of leverages was subsequently optimized. Finally, actuating torques predicted by instant center analysis were compared to the calculated values from finite element analysis. The structural sizing process of the multi-box arrangement was carried out considering elementary methods, and results were compared with finite element simulations.

Numerical study on rehabilitation of the U-rib butt weld fatigue crack in orthotropic steel deck using carbon fiber reinforced polymer strip

2021 ◽  
Author(s):  
Mukai Zhou ◽  
Jiang Xu ◽  
Zhilin Lv ◽  
Xuhong Qiang
Keyword(s):  
Fatigue Crack ◽  
Stress Concentration ◽  
Carbon Fiber ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Butt Weld ◽  
Reinforced Polymer ◽  
Weld Fatigue ◽  
Cfrp Strip

<p>The U-rib butt weld fatigue crack is a typical crack form in orthotropic steel bridge decks. However, there is no completely mature rehabilitation method so far. In this paper, the carbon fiber reinforced polymer (CFRP) strip is used to reduce the stress concentration at the crack tip. Finite element model of U-rib segment was established and parameter analysis was conducted to investigate the influence of the CFRP strip design parameters on the rehabilitation effect. The results indicate that the influence of the three parameters on the reduction of stress concentration is: CFRP layer number &gt; paste width &gt; paste area. Specifically, it is recommended that number of CFRP layers does not exceed 3. For paste width and area, it is only required that the CFRP strip can cover the cracked area.</p>

Developing of the optimal shape and reinforcement structure of the specimen for adequate determination of the tensile strength in unidirectional composites

2021 ◽  
Vol 87 (2) ◽  
pp. 43-55
Author(s):  
A. N. Polilov ◽  
D. D. Vlasov ◽  
N. A. Tatus’
Keyword(s):  
Stress Concentration ◽  
Specimen Thickness ◽  
Fem Modeling ◽  
Cross Sectional ◽  
Reinforcement Structure ◽  
Unidirectional Composites ◽  
Manufacturing Testing ◽  
Rectangular Strips ◽  
Specimen Shape

Unidirectional composites exhibit the highest strength when stretched along the fibers. However, the proper determination of the strength faces great methodological difficulties. The main problems of tensile testing of polymer composites consisted in developing of the specimen shape and the method of specimen fixation which ensure the minimum impact of the stress concentration near the grips on the strength measurements. A conventional shape of the specimen with fillets is unsuitable for unidirectional polymers due to the splitting occurred in the fillet zones upon loading. Therefore, the specimens are usually standardized in the form of rectangular strips fixed using pads or special grips which provide constant transverse forces. However, with such a specimen shape, a significant stress concentration inevitably occurs at the edge of grips and the lower the ratio of the interlayer shear modulus to the longitudinal Young’s modulus, the greater the stress concentration impact. For the purpose of the most correct determination of the strength we propose to use specimens with smoothly varying dimensions at the same cross-sectional area which ensures keeping the total number of unbroken fibers in each section. The specimen thickness decreases when moving from the working part of the specimen to the gripping part, whereas the width (while maintaining the section area) grows to prevent the specimen collapsing resulting from transverse forces in standard self-tightening grips. Analytical and FEM modeling is performed to select a rational contour shape. Technological equipment has been developed and a procedure of manufacturing testing specimens has been worked out. The tensile test of specially manufactured curvilinear reinforced specimens showed higher strength values compared to standard rectangular strips or specimens with semicircular fillets.

scholarly journals Balloon-based measuring system for compliance investigations

2018 ◽  
Vol 4 (1) ◽  
pp. 539-542
Author(s):  
Wolfram Schmidt ◽  
Carsten Tautorat ◽  
Kerstin Schümann ◽  
Peter Behrens ◽  
Niels Grabow ◽  
...  
Keyword(s):  
Balloon Catheter ◽  
Measuring System ◽  
Lumen Area ◽  
Cross Sectional ◽  
Technical Limitation ◽  
Elastic Tubes ◽  
Starting Point ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Working Principle

AbstractFor the development of new stent designs, the compliance of the surrounding biological tissue has to be considered. We expect to obtain parameters for simulation, stent dimensioning, and the forces acting on the stent after implantation. Starting point of the investigations is the commercially available Metricath system allowing cross-sectional lumen area measurements of arteries. Its working principle is based on the pressure-volume relationship using a balloon catheter, which is inflated to a specific pressure of about 250 mmHg and conforms to the shape and size of the lumen. However, for compliance charts multiple pressure levels and a larger pressure range are needed. To overcome this technical limitation, the Metricath balloon catheter is combined with a new inflation device, called pV-Monitor. The presented cross-sectional lumen area measurements in rigid tubes and compliance investigations of elastic tubes demonstrate the feasibility of the pV-Monitor system.

Modeling growth stocks via birth-death processes

2003 ◽  
Vol 35 (3) ◽  
pp. 641-664 ◽  
Author(s):  
S. C. Kou ◽  
S. G. Kou
Keyword(s):  
Size Distribution ◽  
Death Process ◽  
Cross Sectional ◽  
Share Prices ◽  
Cross Sectional Size ◽  
High Volatility ◽  
Growth Stocks ◽  
Future Growth ◽  
Modeling Growth ◽  
Birth Death

The inability to predict the future growth rates and earnings of growth stocks (such as biotechnology and internet stocks) leads to the high volatility of share prices and difficulty in applying the traditional valuation methods. This paper attempts to demonstrate that the high volatility of share prices can nevertheless be used in building a model that leads to a particular cross-sectional size distribution. The model focuses on both transient and steady-state behavior of the market capitalization of the stock, which in turn is modeled as a birth-death process. Numerical illustrations of the cross-sectional size distribution are also presented.

scholarly journals Mechanical Compromise of Partially Lacerated Flexor Tendons

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Jaclyn Kondratko ◽  
Sarah Duenwald-Kuehl ◽  
Roderic Lakes ◽  
Ray Vanderby
Keyword(s):  
Stress Concentration ◽  
Cross Section ◽  
Viscoelastic Properties ◽  
Maximum Stress ◽  
Surgical Repair ◽  
Cross Sectional ◽  
Flexor Tendons ◽  
Percent Loss ◽  
Before And After ◽  
Insight Into

Tendons function to transmit loads from muscle to move and stabilize joints and absorb impacts. Functionality of lacerated tendons is diminished, however clinical practice often considers surgical repair only after 50% or more of the tendon is lacerated, the “50% rule.” Few studies provide mechanical insight into the 50% rule. In this study cyclic and static stress relaxation tests were performed on porcine flexor tendons before and after a 0.5, 1.0, 2.0, or 2.75 mm deep transverse, midsubstance laceration. Elastic and viscoelastic properties, such as maximum stress, change in stress throughout each test, and stiffness, were measured and compared pre- and post-laceration. Nominal stress and stiffness parameters decreased, albeit disproportionately in magnitude, with increasing percent loss of cross-sectional area. Conversely, mean stress at the residual area (determined using remaining intact area at the laceration cross section) exhibited a marked increase in stress concentration beginning at 47.2% laceration using both specified load and constant strain analyses. The marked increase in stress concentration beginning near 50% laceration provides mechanical insight into the 50% rule. Additionally, a drastic decrease in viscoelastic stress parameters after only an 8.2% laceration suggests that time-dependent mechanisms protecting tissues during impact loadings are highly compromised regardless of laceration size.

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