热处理工艺对Ni-Bi合金晶界硬度影响的纳米力学探针分析

晶界脆化问题一直是提高金属材料服役性能所必须关注的重要问题,但目前并没有直接的实验方法来确定晶界的硬度,因而也无法直接判定晶界的脆化状况。以经过不同工艺热处理的Ni-Bi二元合金为研究对象,利用光学金相显微镜和透射电镜观察了合金的微观组织,同时利用纳米力学探针进行了合金晶界和晶粒基体载荷—位移曲线的测定,并计算出了晶界和晶粒基体硬度的变化规律。结果表明,Ni-Bi二元合金的晶界和晶粒基体都不存在沉淀相;晶界硬度要低于晶粒基体的硬度,而且时效时间较长的合金,其晶界硬度更低。由此,确认了纳米力学探针在测量晶界脆化方面的可行性,并分析确定了晶界软化的原因:Bi的晶界偏聚。     

Experimental milling moment model in orthogonal cutting condition: to an accurate energy balance

The control of cutting energy parameters is essential to optimize the cutting condition during the milling process. Our previous works (Cahuc et al., Int J Adv Manuf Technol 18(9):648?C656, 2001; Darnis et?al. 2000) have shown the existence of the six components of the cutting mechanical actions. Thus, the influence of geometric and kinematic parameters on the six components must be quantified. Based on the experimental approach explained in our last works (Albert et al., 2008a, b), this study proposes an energetic criterion characterizing the cutting moment in orthogonal cutting condition. Then, the energy balance has to take into account the cutting moment, highlighting the utility of this criterion. Therefore, the cutting moment model proposed allows an accurate evaluation of the energy balance and the mechanical actions (forces and moments) applied to the workpiece. Consequently, the cutting parameters can be chosen in order to optimize the cutting power consumption.     

Wie k?nnen ?rzte ethisch vertretbar Kostenerw?gungen in ihren Behandlungsentscheidungen ber��cksichtigen? Ein Stufenmodell

Definition of the problem Despite primarily required efforts to increase the efficiency of the delivery system, setting limits for health services will become inevitable in the German health care system. As far as possible, these limits should be set explicitly above the individual physician?Cpatient encounter. For pragmatic reasons, however, physicians will also have to take responsibility for the cost-dimension of their decisions in individual cases. This article, therefore, discusses the question how physicians can integrate cost-considerations into their clinical decisions on the micro level in a medically rational and ethically justified manner. Arguments We propose a four-step model for ??ethical cost-consciousness??: (1) forego ineffective interventions as required by good evidence-based medicine; (2) respect individual patient preferences; (3) minimize the diagnostic and therapeutic effort to achieve a certain treatment goal; and (4) forego expensive interventions that have only a small or unlikely (net-)benefit for the patient. Steps (1?C3) are ethically justified by the principles of beneficence, nonmaleficence, and respect for autonomy, step (4) by the principle of justice. For decisions on step (4), explicit cost-conscious guidelines should be developed locally or regionally. Conclusion Following the four-step model can contribute to ethically defensible, cost-conscious decision-making on the micro level. In addition, physicians?? rationing decisions should meet basic standards of procedural fairness. Regular cost?Ccase discussions and clinical ethics consultation should be available as decision support. Finally, an ethical algorithm for making decisions about expensive medical interventions in individual cases is presented.