Abstract

The rheological properties of concentrated suspensions containing 55 and 60 vol % aluminum particles are studied. This concentration range corresponds to the transition from the viscoelastic to the elastoplastic behavior of the suspensions. Moreover, this range is most favorable for powder injection molding of metals and ceramics. The measurements are performed in a rheometer at different shear stresses. Elastoplastic deformations take place at low stresses, while separation, i.e., the rupture of the adhesion contact between the bulk suspension and the boundary of a solid wall of the rheometer, is observed with an increase in the stress. The rupture of the adhesion contact occurs with time, and this process is characterized by a dependence of the lifetime (durability) of the contact on stress. This dependence is of an exponential character. The replacement of smooth working surfaces of the rheometer by rough ones leads to some increase in the stresses. This reflects the replacement of the adhesion separation by the formation of discontinuities in the bulk suspension at the asperities of the rough surface. The observed behavior of the concentrated suspensions in the aforementioned range of compositions is represented by a mechanical model, into which a new element has been introduced. It is represented by a friction pair with variable length (and, accordingly, variable friction force). The spurt arises when a threshold force that induces displacement over the friction surface is reached.

中文翻译：

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悬浮液剪切变形下的水流过渡

摘要

研究了含有55和60％（体积）铝颗粒的浓缩悬浮液的流变性能。该浓度范围对应于从悬浮液的粘弹性到弹塑性行为的转变。而且，该范围对于金属和陶瓷的粉末注射成型是最有利的。在流变仪中在不同的剪切应力下进行测量。弹塑性变形在低应力下发生，而随着应力的增加，可以观察到分离，即本体悬浮液和流变仪固体壁边界之间的粘附接触的破裂。粘附接触的断裂随时间而发生，并且该过程的特征在于接触寿命（耐久性）对应力的依赖性。这种依赖性具有指数特征。用粗糙的表面代替流变仪的光滑工作表面会导致应力增加。这反映了通过在粗糙表面的凹凸处的本体悬浮液中形成间断而替代了粘附分离。浓缩悬浮液在上述组成范围内观察到的行为由机械模型表示，已在其中引入了新元素。它由可变长度的摩擦副（以及相应的可变摩擦力）表示。当达到在摩擦表面上引起位移的阈值力时，便会出现突波。这反映了通过在粗糙表面的凹凸处的本体悬浮液中形成间断而替代了粘附分离。浓缩悬浮液在上述组成范围内观察到的行为由机械模型表示，已在其中引入了新元素。它由具有可变长度（因此具有可变摩擦力）的摩擦副表示。当达到在摩擦表面上引起位移的阈值力时，便会出现突波。这反映了通过在粗糙表面的凹凸处的本体悬浮液中形成间断而替代了粘附分离。浓缩悬浮液在上述组成范围内观察到的行为由机械模型表示，已在其中引入了新元素。它由具有可变长度（因此具有可变摩擦力）的摩擦副表示。当达到在摩擦表面上引起位移的阈值力时，便会出现突波。因此，可变摩擦力）。当达到在摩擦表面上引起位移的阈值力时，便会出现突波。因此，可变摩擦力）。当达到在摩擦表面上引起位移的阈值力时，便会出现突波。