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Bergmark Anders,Dizdar Senad,Bengtsson Sven,Luk Sydney 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
A comparative study is made on root bending fatigue performance of spur gears and plane bending fatigue performance of notched test bars. R = 0 root bending fatigue tests are made on small spur gears with critical root radius 1.0 mm. The results are compared to plane bending fatigue tests of 0.9 mm radius notched specimens. Results are presented for tests on 4%Ni/2%Cu/1.5%Mo prealloyed PM steel with addition of about 0.6% graphite. Predicted values from the test bars coincide well with the results obtained from the gear root fatigue tests.
Controlled Microstructure for Optimum Fatigue Performance
Takeda Yoshinobu,Bergmark Anders,Alzati Luigi,Bengtsson Sven 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Optimized choice of material for two principally different types of PM components is presented. The first is characterized by high stresses in areas with high stress concentrations (for example synchronizer hubs with very sharp notches, typically <0.25mm in the pre-synchronizer slot and the inner splines). The second type has slightly larger notch radii (small spur gears and sprockets with typically notch radii between 1- 3mm). Diffusion alloyed materials are well suited for sharp notch components. Pre-alloyed materials are also well suited for applications with sharp notches if compressive residual stresses in the notch roots are created by appropriate process control. A free choice of material is available for components with the larger notch radii.
STUDY ON DYNAMIC BEHAVIOUR IN 3PB DUCTILE STEEL SPECIMEN APPLIED BY THE IMPACT LOAD
M. S. HAN,J. U. CHO,A. BERGMARK 한국자동차공학회 2005 International journal of automotive technology Vol.6 No.3
The dynamic crack growth in ductile steel is investigated by means of the impact loaded 3 point bending (3PB) specimens. Results from experiments and numerical simulations are compared to each other. A modified 3PB specimen designed with the reduced width at its ends has been developed in order to avoid the initial compressive loading of the crack tip and also to avoid the uncertain boundary conditions at the impact heads. Numerical simulations of the experiments are made by using a finite element method (FEM) code, ABAQUS. The high speed photography is used to obtain the crack growth and the data of the crack tip opening displacement (CTOD). The direct measurements of the relative rotations of two specimen halves are made by using the Moire interference pattern.
STUDY ON DYNAMIC BEHAVIOUR IN 3PB DUCTILE STEEL SPECIMEN APPLIED BY THE IMPACT LOAD
HAN M. S.,CHO J. U.,BERGMARK A. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.3
The dynamic crack growth in ductile steel is investigated by means of the impact loaded 3 point bending (3PB) specimens. Results from experiments and numerical simulations are compared to each other. A modified 3PB specimen designed with the reduced width at its ends has been developed in order to avoid the initial compressive loading of the crack tip and also to avoid the uncertain boundary conditions at the impact heads. Numerical simulations of the experiments are made by using a finite element method (FEM) code, ABAQUS. The high speed photography is used to obtain the crack growth and the data of the crack tip opening displacement (CTOD). The direct measurements of the relative rotations of two specimen halves are made by using the Moire interference pattern.
Stable and Unstable Crack Growth in Chromium Pre-alloyed Steel
Gerosa Riccardo,Rivolta Barbara,Tavasci Adriano,Silva Giuseppe,Bergmark Anders 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Sintered steels are materials characterized by residual porosity, whose dimension and morphology strongly affect the fatigue crack growth behaviour of the material. Prismatic specimens were pressed at from Astaloy CrM powder and sintered varying the sintering temperature and the cooling rate. Optical observations allowed to evaluate the dimensions and the morphology of the porosity and the microstructural characteristics. Fatigue tests were performed to investigate the threshold zone and to calculate the Paris law. Moreover tests were performed to complete the investigation. Both on fatigue and samples a fractographic analysis was carried out to investigate the crack path and the fracture surface features. The results show that the Paris law crack growth exponent is around 6.0 for sintered and around 4.7 for sintered materials. The same dependence to process parameters is not found for .