A Unified Theory of Cavitation Damage

1963 ◽  
Vol 85 (3) ◽  
pp. 365-373 ◽  
Author(s):  
A. Thiruvengadam
Keyword(s):  
Yield Stress ◽  
Strain Energy ◽  
Functional Relationship ◽  
Present Theory ◽  
Experimental Results ◽  
Unified Theory ◽  
Cavitation Damage ◽  
Dynamic Yield ◽  
Critical Cavitation ◽  
Damage Number

The Cavitation Damage Number proposed by the author has been modified to incorporate the concept of strain-energy instead of the dynamic yield stress of the material. The correlation between the Cavitation Damage Number and the Number of Cavities has been extended to different materials and different sizes. A third nondimensional number known as the Inception of Damage Number has been derived and correlated with the critical cavitation parameter. Detailed investigations in the threshold zone indicate the validity of the functional relationship between the critical cavitation parameter and the Inception of Damage Number. In this paper, the part played by each parameter is analyzed and some of the experimental results arrived at by earlier investigators are explained in the light of the present theory.

The Use of Strain Energy and Fracture Correlation to Determine Life Expectancy for Notched Components

2009 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross ◽  
M.-H. Herman Shen
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Cross Section ◽  
Strain Energy ◽  
Notch Root ◽  
Stress Gradient ◽  
Strain Curve ◽  
Experimental Results ◽  
Cyclic Process ◽  
Notched Components

An energy-based method for predicting fatigue life of half-circle notched specimens, based on the nominal applied stress amplitude, has been developed. This developed method is based on the understanding that the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where the density of each can be determined by measuring the area underneath the monotonic true stress-strain curve and measuring the sum of the area within each Hysteresis loop in the cyclic process, respectively. Using this understanding, the criterion for determining fatigue life prediction of half-circle notched components is constructed by incorporating the stress gradient effect through the notch root cross-section. Though fatigue at a notch root is a local phenomenon, evaluation of the stress gradient through the notch root cross-section is essential for incorporating this method into finite element analysis minimum potential energy process. The validation of this method was carried out by comparison with both notched and unnnotched experimental fatigue life of Aluminum 6061-T6 (Al 6061-T6) specimens under tension/compression loading at the theoretical notch fatigue stress concentration factor of 1.75. The comparison initially showed a slight deviation between prediction and experimental results. This led to the analysis of strain energy density per cycle up to failure, and an improved Hysteresis representation for the energy-based prediction analysis. With the newly developed Hysteresis representation, the energy-based prediction comparison shows encouraging agreement with unnotched experimental results and a theoretical notch stress concentration value.

Magnetic field dependent steady-state shear response of Fe3O4 micro-octahedron based magnetorheological fluids

2018 ◽  
Vol 20 (30) ◽  
pp. 20247-20256 ◽  
Author(s):  
A. V. Anupama ◽  
V. B. Khopkar ◽  
V. Kumaran ◽  
B. Sahoo
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Rheological Behaviour ◽  
Magnetorheological Fluids ◽  
Shear Response ◽  
Field Dependent ◽  
Dynamic Yield ◽  
Magneto Rheological

The magneto-rheological behaviour of fluids containing soft-ferrimagnetic Fe3O4 micro-octahedrons (M = magnetization, τY = dynamic yield-stress and H = applied-magnetic-field).

Modal Strain Energy Based Damage Detection Applied to a Full Scale Composite Helicopter Blade

2013 ◽  
Vol 569-570 ◽  
pp. 457-464 ◽  
Author(s):  
Fabio Luis Marques dos Santos ◽  
Bart Peeters ◽  
Herman van der Auweraer ◽  
Luiz Carlos Sandoval Góes
Keyword(s):  
Structural Health Monitoring ◽  
Damage Detection ◽  
Health Monitoring ◽  
Rotor Blade ◽  
Strain Energy ◽  
Full Scale ◽  
Experimental Results ◽  
Main Rotor ◽  
Helicopter Blade ◽  
Main Rotor Blade

The use of composites in the aircraft industry has generated a great need for structural health monitoring and damage detection systems, to allow for safer use of complex materials. Such is the case with helicopter blades - these components nowadays are mostly composed of carbon fiber or glass fiber reinforced plastics laminates, epoxy and honeycomb filled core structures. The use of composite materials on the main rotor blade also allows for more complex and efficient shapes to be designed, but at the same time, their use requires an additional effort when it comes to structural monitoring, since damage can occur and go unnoticed. This work presents experimental results for structural health monitoring method based on strain energy. The test subject is a full-scale composite helicopter main rotor blade, which is a highly flexible, slender beam that can display unusual dynamic behavior with orthotropic behavior. This damage detection method is based on the modal strain properties, and a damage detection index is used to identify and quantify damage. A test setup was built to carry out an experimental modal analysis on the main rotor blade. For that purpose, a total of 55 uniaxial accelerometers were used on the helicopter blade to measure the displacement modes of the structure. To compute the strain modes from the displacement modes, central differences approximation is used. Damage is introduced on the blade by attaching a small mass to two different locations. Experimental results show the possibility of locating damage in this case.

scholarly journals Влияние гигантской магнитострикции на динамический предел текучести в условиях высокоскоростной деформации

2021 ◽  
Vol 63 (12) ◽  
pp. 2070
Author(s):  
В.В. Малашенко
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Yield Stress ◽  
High Strain ◽  
Dynamic Yield Stress ◽  
High Strain Rate Deformation ◽  
Dynamic Yield ◽  
Giant Magnetostriction

The high-strain rate deformation of crystals with giant magnetostriction is theoretically analyzed. It is shown that giant magnetostriction has a significant effect on the dynamic yield stress of crystals.

On a Simplified Method for Solving Impulsively Loaded Structures of Rate-Sensitive Materials

1965 ◽  
Vol 32 (3) ◽  
pp. 489-492 ◽  
Author(s):  
Nicholas Perrone
Keyword(s):  
Yield Stress ◽  
Rate Sensitivity ◽  
Approximate Solutions ◽  
Exponential Rate ◽  
Structural Elements ◽  
Sensitive Material ◽  
Perfectly Plastic ◽  
Simplified Method ◽  
Dynamic Yield ◽  
Constant Yield

In an attempt to assess more completely rate-sensitive material effects, two fundamental structural elements are analyzed: A wire with an impulsively loaded end mass, and an impulsively loaded ring. The ring and wire are made of perfectly plastic, rate-sensitive materials. In each case, exact and approximate solutions are obtained for an exponential rate-sensitivity law. The results suggest that very good approximations to the exact solutions may be found by utilizing a rate-insensitive material with constant yield stress equal to the initial dynamic yield stress.

scholarly journals Effects of Silicone Oil Viscosity and Carbonyl Iron Particle Weight Fraction and Size on Yield Stress for Magnetorheological Grease Based on a New Preparation Technique

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1778 ◽  
Author(s):  
Kejie Wang ◽  
Xiaomin Dong ◽  
Junli Li ◽  
Kaiyuan Shi ◽  
Keju Li
Keyword(s):  
Yield Stress ◽  
Carbonyl Iron ◽  
Silicone Oil ◽  
Weight Fraction ◽  
Iron Particle ◽  
Preparation Technique ◽  
Oil Viscosity ◽  
Dynamic Yield Stress ◽  
Carbonyl Iron Particle ◽  
Dynamic Yield

This paper investigated the effects of silicone oil viscosity (SOV) and carbonyl iron particle (CIP) weight fraction and size on dynamic yield stress for magnetorheological (MR) grease. The MR grease samples were prepared using orthogonal array L9 on the basis of a new preparation technology. The shear rheological tests were undertaken using a rotational shear rheometer and yield stress was obtained based on the Bingham fluid model. It was found that CIP fractions ranging from 65 wt% to 75 wt% and SOV varying from 50 m2·s−1 to 1000 m2·s−1 significantly affect the magnetic field-dependent yield stress of MR grease, but the CIPs with sizes of 3.2–3.9 μm hardly had any influence based on the analysis of variance (ANOVA). In addition, the yield stress of MR grease mainly depended on the CIP fraction and SOV by comparing their percent contribution (PC). It was further confirmed that there were positive effects of CIP fraction and SOV on yield stress through response surface analysis (RSA). The results showed a high dynamic yield stress. It indicated that MR grease is an intelligent material candidate which can be applied to many different areas requiring high field-induced rheological capabilities without flow for suspension. Moreover, based upon the multivariate regression equation, a constitutive model was developed to express the function of the yield stress as the SOV and fraction of CIPs under the application of magnetic fields.

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