1. Cyclic plasticity and low-cycle fatigue (1) Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Low-cycle fatigue of cold forging dies Dies for cold forging mainly fail due to: - fracture caused by low-cycle fatigue - wear Metallurgical analysis of worn-out dies indicates: -wear phenomena observed at low die lives are often related to low-cycle fatigue mechanisms In case of high-precision dies for net shape parts: -low-cycle fatigue is the dominating failure mechanism

2. Cyclic plasticity and low-cycle fatigue (2) Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Phases of low-cycle fatigue phase 1 cyclic loading of the undamaged material phase 2 initiation of micro cracks a < 0.1 mm phase 3 merging of micro cracks to surface defects and larger cracks 0.1 < a < 0.5 mm phase 4 growth of larger cracks a > 0.5 mm

3. Cyclic plasticity and low-cycle fatigue (3) Established within the GROWTH project GRD1-1999-10748 "Improvement of Service Life and Reliability of Cold Forging Tools with respect to Fatigue Damage due to Cyclic Plasticity (COLT)", funded by the European Community. COLT Design Manual for Cold Forging Dies Typical merging of micro-cracks in a cold forging die ©2000 by Risø National Laboratory, Denmark