Bending Fatigue Behaviour of Laminated Sandwich Beams

2012 ◽  
Vol 445 ◽  
pp. 548-553 ◽  
Author(s):  
Onur Coskun ◽  
Halit S. Türkmen
Keyword(s):  
Free Vibration ◽  
Vibration Frequency ◽  
Mechanical Performance ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Bending Stiffness ◽  
Bending Test ◽  
Sandwich Beams ◽  
Bending Fatigue ◽  
Free Vibration Frequency

In this study, the bending fatigue behaviour of laminated sandwich beams, which are made of carbon/epoxy face sheets and aramid honeycomb core, has been investigated experimentally. The wet hand lay-up technique is used and curing is processed on the heated vacuum table at an elevated temperature to manufacture the sandwich beams. The experimental set-up for bending fatigue test provides a cantilever in one end and a cyclic load at the free end with constant displacement amplitude at room temperature. The load applied to the beam is measured using a load cell during the bending test. Different displacement amplitudes are performed. Mechanical properties, bending stiffness and free vibration frequency of the sandwich beam are investigated. The bending test of the beams and vibration identification test using a vibration analyzer, a hammer and an accelerometer are performed to measure the bending stiffness and determination of free vibration frequency of the clamped sandwich beams before starting and after completion of the fatigue tests. The bending stiffness and free vibration frequencies before and after the fatigue tests are compared to understand the effect of repeated loadings on the mechanical performance of the laminated sandwich beams.

Improving four-point bending performance of marine composite sandwich beams by core modification

2020 ◽  
Vol 54 (8) ◽  
pp. 1049-1066
Author(s):  
F Balıkoğlu ◽  
N Arslan ◽  
TK Demircioğlu ◽  
O İnal ◽  
M İren ◽  
...  
Keyword(s):  
Bending Strength ◽  
Mechanical Performance ◽  
Composite Beams ◽  
Bending Stiffness ◽  
Bending Test ◽  
Sandwich Composite ◽  
Foam Core ◽  
Sandwich Beams ◽  
Bending Performance ◽  
Four Point Bending

The aim of this study was to improve four-point bending performance of foam core sandwich composite beams by applying various core machining configurations. Sandwich composites have been manufactured using perforated and grooved foam cores by vacuum-assisted resin transfer moulding method with vinyl-ester resin system. The influence of grooves and perforations on the mechanical performance of marine sandwich composite beams was investigated under four-point bending test considering the weight gain. Bending strength and effective bending stiffness increased up to 34% and 61%, respectively, in comparison to a control beam without core modification. Analytical equations were utilised for calculating the mid-span deflection, equivalent bending stiffness and ultimate bending strength of the sandwich beams. Finite element analysis was also performed to analyse the flexural response of the specimens taking into account the combined effect of orthotropic linear elasticity of the face sheet and the non-linear behaviour of the foam core.

Fatigue Behaviour of DLC Coated Al 7075-T6 Alloy in an Aggressive Mixture

2014 ◽  
Vol 627 ◽  
pp. 81-84 ◽  
Author(s):  
Sergio Baragetti ◽  
Riccardo Gerosa ◽  
Francesco Villa
Keyword(s):  
High Performance ◽  
Contact Fatigue ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Structural Elements ◽  
Pvd Coatings ◽  
Bending Fatigue ◽  
Al 7075 ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

7075-T6 aluminium alloy is commonly adopted in high performance structures and components. Its fatigue behaviour is however dramatically worsened by exposure to aggressive environments. The deposition of PVD coatings, which are commonly adopted to increase the surface properties of structural elements in terms of hardness, contact fatigue and wear resistance, could be beneficial also for the fatigue behaviour of a 7075-T6 substrate in an aggressive environment. In the present work, Diamond Like Carbon (DLC) PVD coated 7075-T6 specimens immersed in methanol have been analysed, by means of step-loading rotating bending fatigue tests (R = -1) at 2·105 cycles. Coated specimens were tested in laboratory air for comparison, and uncoated polished samples were studied in both the environments to obtain reference values. SEM micrographs of the fracture surfaces were taken to investigate the effects of the corrosive environment on the failure mechanism.

Dry Friction Effect on the Work of Viscous Torsion Damper

2016 ◽  
Vol 817 ◽  
pp. 13-18
Author(s):  
Celina Jagiełowicz-Ryznar
Keyword(s):  
Friction Coefficient ◽  
Free Vibration ◽  
Friction Force ◽  
Vibration Frequency ◽  
Forced Vibration ◽  
Dry Friction ◽  
Viscous Damper ◽  
The Real ◽  
Free Vibration Frequency ◽  
Marine Engines

The results of crankshaft forced vibration calculations, including the dry friction force which can be formed in the viscous damper bearing sliding, were presented. This problem concerns the big dampers used in the marine engines. The friction force influence is presented using the function {sign}. Low values of friction coefficient, corresponding to the conditions similar to the real ones, were assumed. In the range of tested value, it was found that the vibration increases linearly, and system free vibration frequency doesn’t change practically.

scholarly journals Cyclic fatigue behaviour of hydrothermally aged 3Y-TZP ceramics in 4-point bending tests

2021 ◽  
Vol 15 (2) ◽  
pp. 184-194
Author(s):  
Renato Souza ◽  
Roberto Duarte ◽  
Manuel Alves ◽  
Juliana Daguano ◽  
Santos dos ◽  
...  
Keyword(s):  
Bending Strength ◽  
Ceramic Materials ◽  
Cyclic Fatigue ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Bending Test ◽  
Test Results ◽  
Transformation Toughening ◽  
Bending Tests ◽  
M Phase

Fatigue is one of the most important properties to be considered in ceramic dental implants due to cyclic mechanical stresses arising from the chewing process. In this work, the fatigue behaviour of hydrothermally degraded ZrO2-based ceramics stabilized with 3mol% Y2O3 (3Y-TZP) was studied in 4-point bending tests. Samples of 3Y-TZP were compacted (100MPa), sintered at 1475 ?C for 2 h, polished and hydrothermally degraded in an autoclave as described in the ISO-13356 standard. The samples were characterized by their relative density, crystalline phase composition, microstructure and surface roughness. The highly dense (>99.6%TD) sintered 3Y-TZP ceramics has only tetragonal t-ZrO2 phase, even after hydrothermal ageing. Furthermore, the ceramic materials presented a Vickers hardness of 12.7?0.2GPa, a fracture toughness of 7.1?0.3MPa?m1/2 and a 4-point bending strength of 940.1?67MPa. Based on the bending test results 5 different stress levels for the fatigue tests were selected and conducted by cyclic 4-point bending obtaining the S-N curve. Weibull statistics was used for the statistical analysis. The fatigue tests indicate that the limit of fatigue resistance of this 3Y-TZP ceramics is around 550MPa, i.e. higher than the limits established in the ISO-13356 standard for the use of Y-TZP ceramics for the manufacture of implants. The fatigue behaviour of the investigated 3Y-TZP ceramics was related to the toughening mechanisms acting in Y-TZP ceramics, such as transformation toughening related to t?m phase transformation and microcracking.

Effect of the shot peening process on the fatigue strength of SAE 5160 steel

2018 ◽  
Vol 233 (12) ◽  
pp. 4328-4335 ◽  
Author(s):  
Héctor E Jaramillo S ◽  
Nelly Alba de Sánchez ◽  
Julian A Avila D
Keyword(s):  
Fatigue Strength ◽  
Shot Peening ◽  
Base Material ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Correlation Factor ◽  
Bending Test ◽  
Three Point Bending ◽  
Before And After ◽  
Almen Intensity

The fatigue behaviour of SAE 5160 steel was evaluated before and after applying a shot peening process by using different Almen intensities and surface coverings (uncovered, partial coverage and total coverage). In the high-cycle fatigue tests, maximum stresses of 0.8 Sut, 0.7 Sut and 0.6 Sut were applied in the three-point bending test on an Instron 8872 servo-hydraulic machine at a frequency of 10 Hz and a constant stress ratio of Smin/ Smax = 0.2 for all tests. The fatigue tests were performed based on the ASTM E8, the specimens were classified into six groups for each stress evaluated, and each group consisted of three standardised specimens (ASTM E466). Also, yield strength, ultimate strength, hardness and microhardness were obtained. The Wilcoxon’s non-parametric test was used to statistically compare all the mechanical properties obtained from the base material with those obtained after the application of the shot peening, for the different surface coverings and Almen intensities. The results showed that the shot peening process significantly increases the fatigue strength of the material, with a 94% increase in fatigue strength of the fully coated specimens. However, no significant increase in fatigue strength was found due to a change in the Almen intensity value. A high correlation factor was found between the increase in the ultimate resistance and the increase in Almen intensity; however, for the yield stress the correlation was medium and inverse. For hardness and microhardness, the correlation factor was very low. Finally, the microhardness values revealed a 3% increase in Vickers microhardness of the shot peening specimens compared to the untreated specimens.

Isospectral Euler-Bernoulli beams with continuous density and rigidity functions

1987 ◽  
Vol 413 (1844) ◽  
pp. 235-250 ◽  
Keyword(s):  
Boundary Condition ◽  
Free Vibration ◽  
Exact Solutions ◽  
Vibration Frequency ◽  
Flexural Rigidity ◽  
Homogeneous Case ◽  
Continuous Density ◽  
Free Vibration Frequency ◽  
End Conditions ◽  
Vibration Frequency Spectrum

Isospectral systems are those that have exactly the same free-vibration frequency spectrum with respect to a given boundary condition configuration. In this paper, seven different classes of inhomogeneous Euler-Bernoulli beams with continuous density and flexural rigidity functions are found that are analytically solvable and that are isospectral with a homogeneous beam in the clamped-clamped configuration. Of these exact solutions, one class is isospectral with the homogeneous case in all ten distinct configurations obtainable from clamped, sliding and two antiresonant end conditions, whereas another class is isospectral in the six configurations with clamped, hinged or free end conditions. A connection with inverse problems is discussed.

Contact and bending fatigue behaviour of austempered ductile iron gears

2017 ◽  
Vol 232 (6) ◽  
pp. 998-1008 ◽  
Author(s):  
Carlo Gorla ◽  
Edoardo Conrado ◽  
Francesco Rosa ◽  
Franco Concli
Keyword(s):  
Ductile Iron ◽  
Contact Fatigue ◽  
Research Programme ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Austempered Ductile Iron ◽  
Fatigue Properties ◽  
Bending Fatigue ◽  
Metallurgical Analysis ◽  
Single Tooth

In the present paper a research programme aimed at investigating both the bending and contact fatigue properties of an austempered ductile iron applied to gears is presented, in order to determine reliable values of the limits, which take into account the influence of the production process, to be applied in the design of gearboxes. The bending fatigue tests are performed according to the single tooth fatigue approach and the pitting tests are performed with a back-to-back rig. Metallurgical analysis is performed on the failed specimens, in order to understand the origin and the propagation of the failures and to appreciate the influence of the micro-structure on the performances obtained.

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