The Introduction of Pro-EMFATIC For Femap

Transcription

1 Che-Wei L. Chang PhD The Introduction of Pro-EMFATIC For Femap Femap Symposium 2014 May 14-16, Atlanta, GA, USA FEMAP SYMPOSIUM 2014 Discover New Insights

2 Table of Contents What Is Pro-EMFATIC? What Is Pro-EMFATIC For Femap? Why Use Pro-EMFATIC with FEA? Pro-EMFATIC Product Highlights Page 2

3 What Is Pro-EMFATIC? - It calculates fatigue damage, life, and durability Pro-EMFATIC is a CAE software package that predicts fatigue life, fatigue damage, and durability (a.k.a. fatigue safety factor) of mechanical structures using crack-initiation life criterion equations. Common Material Failures: 1.Overload: predicted by FE stress analysis - FEMAP with NX Nastran 2.Fatigue: calculated using various life criteria - Pro-EMFATIC Cyclic Loading How to gauge durability against the goal? Can it last for 10K duty Cycles? How durable/safe is the structure? How much fatigue damage accumulated? Page 3 Where are the critical fatigue locations?

4 What is Pro-EMFATIC for Femap? - A fatigue solution embedded in Femap Pro-EMFATIC works with Femap as an integrated module. Taking the stress and/or strain results in FEMAP, Pro- EMFATIC calculates the life, damage and safety factor of mechanical structures and products. The fatigue and durability results from Pro-EMFATIC can be stored and displayed using the post-processing tools in Femap. Femap Pro-EMFATIC for Femap Loading definition with cycles counting Fatigue Material Kt, ms, md, mt, mo Stress/ Strain of FEA Fatigue Loading Fatigue/Cyclic Properties Notch/ Surface/ Life Criterion EQ. Fatigue Evaluation Size/ Loading/ influencing factors Page 4 Life/Damage/Safety Factor

5 What is Pro-EMFATIC for Femap? - Working with both FEA results and Test measurements Durability evaluations using both FEA and Test results: Evaluations based on FEA results in Femap Evaluations based on measured stress/strain histories and/or cyclic loads Measured s/e time histories Measured s/e Page 5

6 Why Use Pro-EMFATIC with FEA? - A complementary solution that extend the capability and value of FEA Like FEA, Durability analysis helps reduce time and cost for physical prototyping/testing Durability testing generally requires more time and resource than the other tests Most of the mechanical structure is designed to endure repeated duty cycles (load sequences). In each duty cycle, the loads (stresses) applied to the material may not be high enough to cause any yield or rupture concern. However, the loading cycles may still cause material fatigue and thus failure. Pro-EMFATIC for FEMAP is used to predict such failure and assess the durability against the design goals. Femap offers traditional FEA: Strength Analysis rates material s ability to resist failure (Yield/Rupture) due extreme loads Buckling Solvers calculate the loads causing structure instability Eigen and response analyses predict the resonance, beatings, and vibrations Pro-EMFATIC for Femap Offers a complete set of fatigue and durability solutions Durability rates material s ability to sustain failure due to repeated (cyclic) loading Page 6

7 - Overall capabilities/features Predict life of mechanical products Evaluate damage of mechanical parts Assess durability (a.k.a. fatigue safety factors) against the designed goals Find the critical fatigue locations on mechanical parts Identify the most-damaging loading direction on structures Integrated solutions for Femap users Page 7

8 - Fatigue Material Data Management An XML-based material data system is used to create, edit, evaluate, select, and manage material properties for various fatigue evaluations Users can create fatigue material libraries and share them with colleagues Page 8

9 - Fatigue Loading Definition Pro-EMFATIC provides 3 loading modes using existing FE results: Duty Cycle Loading Path Superposition Scale Function ^ S ( t) Fm( t) m Sm Loading Superposition Page 9

10 - Stress/Strain Life Evaluation Pro-EMFATIC provides more than a dozen life criteria for fatigue evaluations and covers most of the methods commonly used in the industry for high-, low-cycle fatigue evaluations. Pro-EMFATIC offers fatigue calculations for uni-axial, biaxial, and multi-axial loading, and users can choose the corresponding life criterion accordingly. Stress-Based Life Palmgren-Miner Rule Modified-Miner Rule W n 1 1 W n 2 2 = W N W = N W n k k = W N 1 2 k W 1 +W 2 + +W k =W k ni i 1 N i 1 Strain-Based Life High-Cycle Fatigue Low-Cycle Fatigue Page 10 Notch factor Surface factor Size factor Load factor DS zero-mean S m correction N predict life and cumulative fatigue damage due to complex loading conditions. How long will it last? Where are the critical fatigue locations?

11 - Life Evaluation For Welds (1993 revision) Weld Life Page 11 BS7608 Standard: B,C,D,E,F,F2,G,W,S,T

12 - Life Evaluation For Pressure Vessel (2010 revision) Common fatigue loadings: Internal and external pressure Impact, including frequent pressure fluctuations Self weight and carried weight, including static and dynamic pressure from fluids Other parts, equipment, insulation, erosion/corrosion protective lining, piping, etc. Locally established loadings such as wind, snow, vibration, seismic movement Reactionary force from supporting rings, saddle, etc. Temperature fluctuations Event 1:Large-Scale temperature change during heating and cooling # of Cycles: 2000 Event 2:Incidental drop in pressure # of Cycles:350 Pro-EMFATIC ASME BPVC Life Event3:Excessive waterflow # of Cycles:300 Page 12

13 - Fatigue Safety Factor Evaluation Safety Factor Can it last for the designed life-span? Where are the weak spots? critical locations S a S -1 B S a S -1 A A C B O Page 13 M N O S u M N S u S m S m

14 - Rain-flow Counting Different methods can be used to identify and count fatigue cycles from time histories of stress or strains. Among them, the Rainflow counting method is the most widely accepted and commonly used counting method. Using Rainflow counting, a time history is re-sequenced into various numbers of fatigue loading cycles of stress (or strain) amplitudes with mean stresses. Once the loading cycles are identified and the number of cycles counted, the fatigue damage of each cycle can be calculated and then linearly combined into a cumulative damage for the whole loading history. S (t) Pro-EMFATIC s advanced Rainflow Counting method that Rainflow Counting Speeds up the counting for long histories by 3-5x. Counts both uniaxial and biaxial loading histories Page 14

15 - Transform FEA tensors for S-N (Scalar) evaluations Pro-EMFATIC for FEMAP uses an advanced free-face transformation technology (for both shell and solid elements) that greatly improves both accuracy and speed for large-size FE fatigue evaluations. 1.transform FEA tensor results onto the tangent plan at the center of element free-faces 2.search for the effective loading directions and calculates the damages accordingly Scalar Tensor Page 15

16 - Searching for max-damage loading direction on element free faces For non-proportional multi-axial loading, the principal loading axes change from time to time. Pro-EMFATIC for FEMAP provides the max-damage-direction searching function, through which the user can find the effective loading direction for fatigue evaluations. damage_3 damage_2 damage_1 Most-damaging loading direction w/ max fatigue damage Δθ Δα θ Page 16

17 - Performance A. SMP for large models and long loading histories B. Free-Face approach dramatically speeds up the fatigue evaluations for thick solid-element models Page 17

18 Thank You Femap Symposium 2014 May 14-16, Atlanta, GA, USA FEMAP SYMPOSIUM 2014 Discover New Insights