First of all, there is an abundant literature by Kalthoff, Giovanola, IV Rokach, Fenchung and Vecchio, and myself among others. The main difference between these 2 tests is that for a 3/4 point bend test, the bc's at the supports should be included, with potential development of plasticity and loss of contact. With the 1 point, all you need is the force or displacement to be prescribed at the impact point, hoping you have no plasticity or damage there. The specimen (usually a beam) is modelled as free-free. It works very nicely with low toughness materials. The main issue with all these tests is the correct determination of the fracture time... Hope it helps!
1 vs 3/4 point impact
Hi Chau
First of all, there is an abundant literature by Kalthoff, Giovanola, IV Rokach, Fenchung and Vecchio, and myself among others. The main difference between these 2 tests is that for a 3/4 point bend test, the bc's at the supports should be included, with potential development of plasticity and loss of contact. With the 1 point, all you need is the force or displacement to be prescribed at the impact point, hoping you have no plasticity or damage there. The specimen (usually a beam) is modelled as free-free. It works very nicely with low toughness materials. The main issue with all these tests is the correct determination of the fracture time... Hope it helps!
Best wishes,
Dany
D. Rittel
merittel [at] technion.ac.il
www.technion.ac.il/~merittel