Semi-elliptical Section Research Articles

Numerical investigation on stress concentration of surface notch on blades

Crack grinding process is the essential step in the remanufacturing pre-treatment for the compressor blade with fatigue crack. After crack grinding process, a notch will be generated on the surface of the blade. Stress concentration factor (SCF) of the surface notch is a basic parameter on remanufacturability assessment depending on fatigue behaviors. However, few equations can be employed directly to estimate SCF of surface notch in the current lecture. In the present study, stress concentration of surface notch with semi-elliptical sections on a plate with finite thickness and width has been investigated using finite element analysis. It was found that the depth and width of surface notch and the thickness of plate were the main factors that controlling the stress concentration. What is interesting in theoretical modeling is that SCF of surface notch with semi-elliptical sections with large thickness can be estimated by the simple modification of Inglis’s equation. Following, based on the modified Inglis’s equation, an empirical SCF equation of surface notch was proposed with the consideration of depth and width of the surface notch and the thickness. A reference value of SCF for the blade after crack grinding process can be provided using the equation.

Homogeneous vs. patient specific breast models for Monte Carlo evaluation of mean glandular dose in mammography

PurposeTo compare, via Monte Carlo simulations, homogeneous and non-homogenous breast models adopted for mean glandular dose (MGD) estimates in mammography vs. patient specific digital breast phantoms. MethodsWe developed a GEANT4 Monte Carlo code simulating four homogenous cylindrical breast models featured as follows: (1) semi-cylindrical section enveloped in a 5-mm adipose layer; (2) semi-elliptical section with a 4-mm thick skin; (3) semi-cylindrical section with a 1.45-mm skin layer; (4) semi-cylindrical section in a 1.45-mm skin layer and 2-mm subcutaneous adipose layer. Twenty patient specific digital breast phantoms produced from a dedicated CT scanner were assumed as reference in the comparison. We simulated two spectra produced from two anode/filter combinations. An additional digital breast phantom was produced via BreastSimulator software. ResultsWith reference to the results for patient-specific breast phantoms and for W/Al spectra, models #1 and #3 showed higher MGD values by about 1% (ranges [–33%; +28%] and [−31%; +30%], respectively), while for model #4 it was 2% lower (range [−34%; +26%]) and for model #2 –11% (range [−39%; +14%]), on average. On the other hand, for W/Rh spectra, models #1 and #4 showed lower MGD values by 2% and 1%, while for model #2 and #3 it was 14% and 8% lower, respectively (ranges [−43%; +13%] and [−41%; +21%]). The simulation with the digital breast phantom produced with BreastSimulator showed a MGD overestimation of +33%. ConclusionsThe homogeneous breast models led to maximum MGD underestimation and overestimation of 43% and 28%, respectively, when compared to patient specific breast phantoms derived from clinical CT scans.

Critical and Normal Depths in Semielliptical Channels

AbstractNormal and critical epths are important parameters in the design, operation, and maintenance of open channels. Semielliptical, prefabricated channels are widely used as tertiary canals in irrigation networks. In semielliptical channels, the governing equations are highly nonlinear in the normal and critical flow depths; thus, the solution of the implicit equations involves numerical methods. The main challenge with semielliptical sections is the calculation of the wetted perimeter. The wetted perimeter of semielliptical sections can be expressed in terms of incomplete elliptic integrals of the second kind. The elliptic integrals can be computed simply using commercial mathematical software, but most engineers who use a simple tool such as Microsoft Excel need a simple yet accurate expression for computing the wetted perimeter. Because elliptic integrals cannot be directly computed using Excel, a simple and accurate expression with maximum error less than 0.07% (near exact solution) is proposed for...

Design and Finite Element Analysis of a Hydraulic Excavator Boom

In today’s world of growing competition, all industries are trying their best to give the components of high quality with minimum expenditure. So in present work a new semi-elliptical boom has been selected to replace the conventional boom, which is usually made of rectangular. In particular, the study wants to substitute the rectangular section for Semi-elliptical section. This change lightens the weight of the boom. For this purpose, boom with semi-elliptical cross-section has been modeled using cad software pro/E wildfire 4.0. Using VB program automatic calculation module (UPAS), the static force at different working condition of the boom calculated. Then Finite element analysis has been done to determine the static stress at a given load condition using software ANSYS 12. The result shows that total weight is reduced by 5%. The value of maximum stress and displacement is 115.663MPa and 12.885 mm respectively. Thus the structure is capable of withstanding the maximum stress. The structure is failsafe. In this paper only static stress analysis is done.

Caracterización geológica del deslizamiento Chiz (Turrialba, provincia de Cartago, Costa Rica): amenaza y prevención

Nearby Chiz de Murcia, Turrialba, Costa Rica, a landslide has developed threatening several houses, a settlement located near the joint of Chiz and Reventazón rivers, a railroad, power lines and water pipes serving the population. It involves very weathered materials of the Uscari Formation (interbeddes clay and sandstone), has a semielliptical section and includes an estimated volumen of 70 000 cubic meters. Around the main landslide other unstability phenomenas have been identified, delineating an ample area of high susceptibility to landslide generation. If the landslide suddenly generates an important volume of debris, it could eventually dam the course of Chiz river, creating the possibility of triggering mud and rocks flows. The present study gives a geological view of the main landslide and its sourrounding area, and has been added a preliminary reconnaissance of the hazard.