《ANSYS接触分析精华》.doc

FAQs on CONTACT – ANALYSIS Terminology: STS – Surface to Surface Contact. NTS - Nodes to Surface Contact .NTN - Node to Node Contact. FKN or Kn - Normal Contact Stiffness. E - Young’s Modulus. ICONT - Initial Contact value. PMIN PMAX - Minimum and Maximum initial Penetration range. PINB - Pinball region Radius. FTOLN - Penetration tolerance. Mu - Friction Coefficient FAQ# 1. On what factor can a contact analysis be judged as OKAY? Answer: Penetration In physical reality, penetration between 2 contacting bodies never occurs. This is a mathematical creation so as to activate a contact stiffness between two bodies. Keeping penetration to a minimum is a best way to simulate a contact analysis. For achieving this, the contact Stiffness may be specified as high as possible as long as a converged FE solution is possible. FAQ# 2. What affects the accuracy and convergence of a contact analysis? (FKN) Stiffness used for the Contact is a major factor affecting Convergence of Contact problems. Using higher values of Stiffness may diverge the solution. Its advised to start with a small enough value and get a converged solution. Re-solve with increased value of stiffness so long as the problem stops converging. Trial and Error + Experience will help you predict the Contact Stiffness needed to solve a Contact Analysis. Another recommended practice is to run the analysis with an initial small contact stiffness and then slowly increase the stiffness over a series of load steps. This will ramp the contact stiffness value from the initially considered Stiffness, thus improving convergence behavior. The results for the last load-step would have been analyzed with more stiffness and hence would be more accurate than previous results. FAQ# 3. What is Hertz Stiffness? How is it calculated? Hertz Stiffness provides an approximate value for the Penalty Stiffness value. Kh = L*E where, Kh -- Hertz Stiffness. L -- Size/edge length of the element at the contact surface E -- Young’s