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为了提高石棉瓦的密实性,在生产过程中,对波形瓦坯进行压实,压实后瓦坯出现弧顶变厚、弧腰变薄的现象,称为“卡腰”图1 过去认为产生“卡腰”现象,是由于瓦型设计中采用了非对称瓦型,底弧与顶弧的连接有一条直线过渡段,加压时压力垂直向下,使瓦坯表面上各点的法向压力不等所造成的。而今经过对加压过程模具运动的轨迹及瓦坯压实变形过程的分析认为:直线过渡段和法向压力不等不是“卡腰”产生的根本原因。现分析如下: 压机模具弧形一般设计成与等厚瓦上表面弧形相同的曲线。曲线1为模具弧形;2为瓦坯上表面;3为加压后理论上等厚瓦上表面。曲线1与3相同,加压时模具顶弧顶点D的运动轨迹为直线D→E→C,σ为瓦坯压缩量。
In order to improve the compactness of the asbestos tile, during the production process, the corrugated billet is compacted. After compaction, the phenomenon that the arc top becomes thicker and the arc waist becomes thinner is called the “card waist”. The “card waist” phenomenon is due to the asymmetrical tile pattern used in the tile design. The connection between the bottom arc and the top arc has a straight transition section. When the pressure is applied, the pressure is perpendicular downwards, making the normal direction of each point on the surface of the blank. The pressure is not equal to that caused. Now the analysis of the trajectory of the movement of the die during the pressurization process and the compaction process of the green compaction considers that the linear transition section and the normal pressure are not the root causes of the “card waist” generation. The analysis is as follows: The arc of the press die is generally designed to have the same curve as that of the arc of the same thickness. Curve 1 is the mold arc; 2 is the upper surface of the tile; 3 is the upper surface of the theoretically thick tile after pressing. The curves 1 and 3 are the same. When the pressure is applied, the trajectory of the top arc D of the mold is a straight line D→E→C, and σ is the compression amount of the blank.