In order to elucidate the plastic deformation of solids, the following assumptions were made: (1) the plastic deformation of solids is classified into two main types, the one which is caused by dislocation movement and the other caused by grain boundary movement, each movement being restricted on a different shear surface, (2) the dislocation movement is expressed by a mechanical model of a parallel connection of various kinds of Maxwell dislocation flow units whereas the grain boundary movement is also expressed by a parallel connection of various kinds of Maxwell grain boundary flow units; the parallel connection in each type of movements indicates that all the flow units on each shear surface flow with the same shear rate, (3) the latter model for grain boundary movement is connected in series to the former for dislocation movement, this means physically that the applied stress distributes homogeneously in the flow system while the total strain rate distributes heterogeneously on the two types of shear planes (dislocation or grain boundary shear plane), (4) the movement of dislocation flow units and grain boundary units becomes possible when the atoms or molecules near the obstacles, which hinder the movement of flow units, diffuse away from the obstacles.
Using the above assumptions in conjunction with the theory of rate processes, generalized equations of shear stress and shear rate for plastic deformation were derived. In this paper, four cases important in practice were considered.
The authors' theory was applied to plastic deformation of ceramics, metals, alloys and single crystals. For polycrystalline substance, the flow mechanisms due to dislocation movement and grain boundary movement appear together or separately according to the experimental conditions whereas for single crystals, only the mechanism of dislocation movement appears. The parameters appearing in the flow equations $(\alpha_{d1},1/\beta_{d1})$ and $(\alpha_{gj}/x_{gj},1/\beta_{gj})$ (j=1 or 2) and the activation enthalpies $\triangle{H}_{k1}^{\neq}$ (k = d or g) were determined \and tabulated. Here, the subscript dl indicates the first kind of dislocation flow units and gj expresses the $\underline{j}$th the kind of grain boundary flow units.
The predictions of the theory were compared with experiment with good agreement. Concerning the activation enthalpies, it was found that $\triangle{H}_{d1}^{\neq} > \triangle{H}_{g1}^{\neq}$ and that the former agrees with the activation enthalpy for bulk self-diffusion whereas the latter agrees with the activation enthalpy for bulk self-diffusion whereas the latter agrees with the activation enthalpy for grain boundary self-diffusion. These facts support the adequacy of the authors' theory which is considered as a generalized theory of plastic deformation.
고체의 소성변형을 설명하기 위하여 다음과 같은 가정을 하였다. (1) 고체의 소성변형은 크게 두가지 기구 즉 dislocation 운동과 grain boundary운동에 의하여 일어난다.
(2) dislocation 운동에 있어서 유동단위들은 역학적 모형으로 나타내면 다종의 Maxwell 단위들의 평행연결형으로 되고 grain boundary 유동단위들도 다종의 Maxwell 단위들의 평행연결로 표현된다. 이를 물리적으로 설명하면 같은 부류의 유동단위들은 모두 같은 shear plane에서 같은 shear rate로 흐름을 의미한다. (3) grain boundary 유동단위들과 dislo cation 유동단위들 간은 서로 직렬연결되어 있다. 이는 물리적으로 고체내에서 stress는 균일하게 작용하나 shear rate는 shear plane의 종류( dislocation 운동면과 grain boundary운동면 )에 따라 달리 나타남을 의미한다.
(4) dislocation유동단위들과 grain boundary유동단위들의 운동은 그들의 흐름을 방해하는 장애물근방의 원자 또는 분자들이 확산해 나가므로써 가능하게 된다.
이러한 가정하에 반응속도론을 적용하여 shear rate와 shear stress를 구하는 일반식을 도출하였다. 본 연구에서는 실제로 중요한 네가지 경우에 대하여 상기 도출한 일반식을 고찰하였다.
소성변형에 대한 저자들의 이론을 요업재료, 금속, 합금 및 단 결정들에 적용하였다. 그 결과 다중결정에서는 dislocation운동과 grain boundary 운동이 실험조건에 따라 함께 또는 분리되어 나타나는 반면 단결정에서는 dislocation운동만 나타났다. 유동식에 나타나는 파라미터 $(\alpha_{di},1/\beta_{di})$와 $(\alpha_{gj}/X_{gj},1/\beta_{gj})(j=1 혹은 2)$ 및 활성화엔탈피 $\triangle H_{k1}^{\neq} (k=d 혹은 g)$ 를 구하여 예측한 소성변형은 실험과 잘 일치함을 보았다. 여기서 첨자 d1 는 첫번째의 dislocation 유동단위. gj는 j번째 grain boundary 유동단위를 나타낸다. 활성화엔탈피에 대하여 $\triangleH_{d1}^{\neq}$ 는 bulk의 자체확산에 대한 활성화엔탈피와 일치하고 $\triangleH_{g1}^{\neq}$ 는 grain boundary 자체확산에 대한 활성화엔탈피와 일치하였다. 이 사실은 저자들의 이론의 정당성을 보이고 있다.
