Creep behaviour of nodular cast irons with three different matrix compositions and microstructures has been investigated up to fracture in the elastic regime for temperatures between 650
°C and 900
...°C. The elastic stress levels were chosen taking into account the non-linear dependence between elastic stresses and corresponding strains. Results show that austenitic cast irons are more creep resistant than ferritic ones. However, all materials obey to a single Monkman–Grant law. Fracture of samples with short life times is dominated by the plastic straining of the matrix independently of their metallurgical state. Creep fracture of long life time samples is controlled by diffusion mechanisms like cavity nucleation on the grain boundaries. It is shown that the damage growth in secondary and tertiary creep regimes can be represented by a single parameter whatever the creep mechanisms and the metallurgical properties of nodular cast irons.
Purpose
Mesenchymal tumours require high-dose radiation therapy (RT). Small bowel (SB) dose constraints have historically limited dose delivery to paraspinal and retroperitoneal targets. This ...retrospective study correlated SB dose–volume histograms with side-effects after proton radiation therapy (PT).
Patients and methods
Between 1997 and 2008, 31 patients (mean age 52.1 years) underwent spot scanning-based PT for paraspinal/retroperitoneal chordomas (81 %), sarcomas (16 %) and meningiom (3 %). Mean total prescribed dose was 72.3 Gy (relative biologic effectiveness, RBE) delivered in 1.8–2 Gy (RBE) fractions. Mean follow-up was 3.8 years. Based on the pretreatment planning CT, SB dose distributions were reanalysed.
Results
Planning target volume (PTV) was defined as gross tumour volume (GTV) plus 5–7 mm margins. Mean PTV was 560.22 cm
3
. A mean of 93.2 % of the PTV was covered by at least 90 % of the prescribed dose. SB volumes (cm
3
) receiving doses of 5, 20, 30, 40, 50, 60, 70, 75 and 80 Gy (RBE) were calculated to give V5, V20, V30, V40, V50, V60, V70, V75 and V80 respectively. In 7/31 patients, PT was accomplished without any significant SB irradiation (V5 = 0). In 24/31 patients, mean maximum dose (Dmax) to SB was 64.1 Gy (RBE). Despite target doses of > 70 Gy (RBE), SB received > 50 and > 60 Gy (RBE) in only 61 and 54 % of patients, respectively. Mean SB volumes (cm
3
) covered by different dose levels (Gy, RBE) were: V20 (n = 24): 45.1, V50 (n = 19): 17.7, V60 (n = 17): 7.6 and V70 (n = 12): 2.4. No acute toxicity ≥ grade 2 or late SB sequelae were observed.
Conclusion
Small noncircumferential volumes of SB tolerated doses in excess of 60 Gy (RBE) without any clinically-significant late adverse effects. This small retrospective study has limited statistical power but encourages further efforts with higher patient numbers to define and establish high-dose threshold models for SB toxicity in modern radiation oncology.
The ferromagnetic sheet metal blanking is widely used for the manufacturing of rotating electrical machines. However, the optimization of the designed machines depends on full understanding of the ...shearing process. The material mechanical state and magnetic properties near the cut edge depend on various parameters like geometric configuration (shape of the tools, punch blade radius), clearance, frictional contact at the interfaces and the punch speed. Several studies of the blanking process have been proposed to assess the influence of these parameters, but only a few are concerned with the punch velocity. In this paper we use a rate dependent constitutive model for the blanking process investigation to improve the accuracy of the predictions. A 0.65
mm thickness sheet of a non-oriented full-process FeSi (3
wt.%) steel is used. The material testing and the characterization are carried out in order to fit the constitutive model parameters to the experimental data. Classical tensile tests and video-tensile tests are combined to establish the sheet metal constitutive law. The identified model is, then, used for numerical simulations (which are performed using ABAQUS/Explicit software) of various blanking tests: the clearance is ranging from 3.8% to 23%, punch velocity of 23
mm/s and 123
mm/s. In order to validate this work the numerical results obtained are compared to the measurement. The comparisons relate to the punch force and the punch penetration at fracture that are affected by the clearance and the strain rate.
Punching electrical steels drastically alters their magnetic properties near the cutting edges, which should be accounted for when designing machines. A simple magneto-mechanical coupled finite ...element analysis, suitable for fully processed grades, is proposed in order to model the consequences of this local degradation of the material on the global behavior of a machine. The model is used to study the effective section of the teeth of a punched stator; calculated results are compared with experimental data and a good agreement is found.
This study presents an extended in situ magnetic characterisation of a non-oriented (NO) Fe–(3 wt.%)Si steel. An appropriate experimental device was created and magnetic measurements were performed ...under uniaxial tensile stresses approaching and exceeding the macroscopic elastic limit
σ
e and in the corresponding unloaded states. Both Barkhausen noise and B–H hysteresis loops were measured. The sensitivity to stress was found to be qualitatively similar to that of polycrystalline iron. The different stages of the tensile deformation (perfectly elastic stage, microplastic yielding stage, the two strain-hardening stages) were clearly identified by the magnetic parameters. In the plastic strain domain, the coercive field H
c and the inverse of the initial relative permeability 1/
μ
r
i linearly increase, while the maximal relative permeability
μ
r
max and the Barkhausen noise peak height BN
max linearly decrease with the applied stress
σ. The remnant induction
B
r keeps a low and constant value. Furthermore, a linear dependence of 1/
μ
r
i,
H
c,
μ
r
max and BN
max on the kinematic hardening
X was found. By using measurements on prestrained specimens under reloaded elastic stresses, an accurate identification of the effect of dislocations acting as pinning sites and of the magnetoelastic effect of long-range internal stresses was proposed.
The reduction of grain size down to several tens or hundreds of nanometers leads to the enhancement of radiation resistance of metals. Based on this approach, the aim of the Labex EMC3 (Energy ...Materials and Clean Combustion Center) project "Naninox" is (1) to study the stability of the microstructure of a nanostructured 316 stainless steel under ion irradiation and (2) to link between this microstructure and the properties (corrosion resistance and the microhardness) of the steel (thanks to a better irradiation resistance, a better corrosion resistance and higher mechanical properties after irradiation are expected in the ultra-fine grained stainless steel). Ultrafine grained 316L austenitic stainless steel samples have been produced by high pressure torsion (HPT) at 430°C and then ion irradiated in Jannus facilities (CEA Saclay) at 450°C and 5 displacements per atoms (dpa). Their microstructure is characterized before and after irradiation by atom probe tomography, X-ray diffraction and transmission electron microscopy. Corrosion behavior in NaCl solution is tested and nano-indentation tests are performed. The first results obtained by atom probe tomography described in this paper indicate that the microstructure of ultrafine grain 316 austenitic stainless steel is more stable under irradiation than the microstructure of a coarse grain 316 austenitic stainless steel.
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