英语翻译0 .These elements are generated at room temperature,so t

英语翻译
0 .These elements are generated at room temperature,so their addition will have a
cooling effect on the pre-existing melt pool.There will be a heat redistribution period,which is
usually very short as compared with the time elapsed between two element generation procedures.
This is done in accord with the assumption that the clad powder gets melted as it hits the liquid
metal,with the advantage that the cooling effect of the powder on the whole melt pool is handled
by means of heat conduction —that is,in a way which is consistent with conservation of energy.
Some preplaced clad material is considered in the computational domain,corresponding to the
experimental procedure of preplacing some powder to enhance coupling of laser energy to the
workpiece.The moving heat source starts its movement with its center still at the top of the
preplaced clad material; subsequent element generation is only allowed to occur if some melting of
the substrate has taken place (fig.3).As for deformation,the generated elements are strain and
stress free.
T = 585 C
isotherm
t=0.08s
Figure 3.Isotherm corresponding to the substrate liquidus temperature.
2.Modeling
2.1 Heat Transfer modeling
The laser beam is gaussian in shape and results are generated for fixed values of absorbed
power during each computer run.This is an approximation,because the amount of energy
imparted to the workpiece varies with time.Nevertheless,since the process is taking place at
steady-state for the most part,one can assume that an average absorptivity can be defined.This
value can be calculated —for each particular experimental setup— by calibrating the model with the
help of experimental results.Then the total power,which is an important process parameter,can be
easily accessed.Of course,a complete description of the total process absorptivity should include
the dependencies of the surface absorptivities (clad and substrate) on temperature and angle of
incidence,plus the losses associated with the beam focusing optics and also from the interaction
between the beam and the traveling particles.The latter results in a shadowing effect,in which the
clad material particles partially block laser irradiation of the melt pool.To account for this,one
needs to know particle size,shape and distribution in the jet; a full discussion should include
energy absorption at each particle and also account for multiple reflections between particles and
from particles to the melt pool.This has been discussed in some of the previously mentioned
references and also by Marsden et al

0. 这些元素在室温下产生的,因此他们的加入将有预先存在的熔池的冷却效果. 将有一个热再分配时期,这通常很短,两个元素之间生成程序所经过的时间进行比较. 这样做是符合的,该包粉末得到融化,因为它击中了液态金属的优点,即在总体上粉冷却熔池作用是通过热即在传导的方式方法处理的假设这与节约能源是一致的. 一些预置复合材料被认为是计算领域,对应于preplacing一些粉末,以提高激光能量耦合到工件的实验过程. 移动热源中心的开始,它的运动仍然在预置复合材料的顶部;后续元素一代只允许发生如果一些已发生熔化基材（图3）. 至于变形,生成的元素是应变和应力自由. T = 585吨= 0.08s C等温线图3. 等温线所对应的衬底液相温度. 2. 建模2.1传热模拟的激光束的形状和结果高斯吸收功率为固定值的每一台计算机运行过程中产生的. 这是一个近似值,因为能量传递到工件随时间变化的. 不过,因为该进程正在以稳态的大部分地方,人们可以假设平均吸收率可以被定义. 这个值可以计算为每个特定的实验装置由校准与实验结果有助于模型. 然后,总功率,这是一个重要的工艺参数,可以很容易地访问. 当然,一吸的全过程的完整描述应该包括表面的温度和吸光入射角（包层和基材）的依赖,再加聚焦从梁之间的相互作用也束光学和相关的损失旅游颗粒. 在遮蔽效应,其中复合材料颗粒部分阻断熔池的激光照射后的结果. 为了说明这一点,我们需要知道粒子的大小,形状和喷射分布;充分的讨论应包括在每个粒子的能量吸收,也为粒子和粒子之间的多次反射熔池帐户. 这已经讨论了在前面提到的一些参考,也由马斯登等