Strength Resistance of the ship condenser supports Under dynamic impact
D = 1430 mm
nominal pressure in the condenser - 0.024 MPa
inner temperature - 100 deg. С
temperature in tube - 30 deg. C
Material (GOST) - 10XCНД
Strength analysis of a ship condenser supporting elements were performed for a given shock loads. Condeser 3D CAD model is shown in Figure 1.
Project aim was to determine max. (crash) stresses for condenser supports during inertia shock loads. The dynamic load spectrum was determined using Dynamic Design Analysis Method (DDAM) module in Femap and NX Nastran software. DDAM is an engineering methodology for determining the response of a ship's onboard equipment to a shock pulse of an underwater explosion.
Figure 1. 3D CAD model of ship condeser
Mounting flanges of the ship condenser have been fixed though special NX Nastran rigid elements RBE2.
In its chain that rigid element RBE2 was constrained in one node in all linear and rotational directions: Tx, Ty, Tz, Rx, Ry and Rz.
Used approach is conservative and provides higher stress results.
Finite element model (FEM) general representation and constraints scheme are presented in Figure 2, detail welds modeling - in Figure 3.
Figure 2. FEM of the ship condenser and constraints scheme
Figure 3. Support welds representation in FEM
Load spectrum was determined via the following formulas:
Acceleration coefficients were determined according to .
FEM results showed that max. stresses were concentrated in welds and areas near support welds.
For longitudinal (X) and vertical (Y) application of shock load spectrum max. stresses aren't exceed allowable stress or have not significant exceeding.
For transverse (Z) direction of shock load spectrum max. stresses extremly exceed allowable level and appear in whole section cut of weld. In that case design need to be reviewed and update. Based on the results of the analysis, it was found that the values of the calculated stresses of the supporting elements are higher than allowable levels. Structural modifications have been proposed and developed to ensure the strength of the parts under research.
Stress distribution in condenser model can be seen in Figures 4, 5 and 6. Hot spot stress results in weld are shown in Figure 7.
Figure 4. Von Mises stress distribution [MPa] according to longitudinal (X) shock load spectrum
Figure 5. Von Mises stress distribution [MPa] according to vertical (Y) shock load spectrum
Figure 6. Von Mises stress distribution [MPa] according to transverse (Z) shock load spectrum
Figure 7. Hot spot Von Mises stress concentration [MPa] in welds