Flexible ceramic member having a pre-loaded tensile force applying means

Abstract

An elongated flexible member including a plurality of ceramic segments, each segment having at least two opposite surfaces that are flat and parallel. The segments are aligned in stacked relationship with their flat faces in abutting face-to-face relation and forced toward each other in the direction of their composite length with a force which is sufficient to maintain the segments in compression when subjected to conditions of thermal change and/or flexing of the member during use. A method for making the ceramic member is disclosed.

What is claimed is: 
     
       1. In a system including at least two members one of which is movable relative to the other and in frictional engagement therewith, such as members in a papermaking system, the improvement wherein the other member is an elongated flexible ceramic element comprising a plurality of ceramic segments, each having at least two opposite surfaces that are substantially flat and parallel, said segments being aligned with their flat faces in abutting face-to-face relation and in respective planes that are oriented substantially perpendicular to the composite length of said plurality of segments,   tension means anchored to opposite ends of said element and forcing said segments toward each other in a direction along their composite length and substantially perpendicular to their respective parallel faces with a preload force on said tension means, when said latter member is in an undeflected condition, that is at least the force calculated by the equation: ##EQU7## where: P is the preload of said tension means, in pounds;   E c  is the modulus of elasticity of the ceramic material;   A c  is the cross-sectional area of a ceramic segment in a plane perpendicular to the composite length of said elongated ceramic element in square inches;   d is the maximum anticipated deflection of said elongated ceramic element, in inches;   h is the dimension of a ceramic segment in the plane perpendicular to the composite length of said elongated ceramic element and in alignment with the direction of said deflective force, in inches;   l is the overall length of said latter member;   α s  is the coefficient of thermal expansion of said tension means;   α c  is the coefficient of thermal expansion of said ceramic;   Δ T  is the degree of temperature change anticipated, in degrees F.;   A s  is the cross-sectional area of said tension means,   E s  is the modulus of elasticity of said tension means, .[.and   L is the length of a ceramic segment, in inches,.]. but less than the amount of preload force which will compress said ceramic to over about one-half of its maximum compressive strength,     whereby loading forces exerted upon said elongated ceramic element are directed thereagainst in a direction substantially perpendicular to the longitudinal dimension thereof and deflection of said elongated ceramic element pursuant to such loading forces is compensated for in said compressed segments by further compression of said segments in those portions of the abutting faces thereof disposed along the inside of the line of curvature of said elongated ceramic element and by relief of less than all of the compression in those portions of said abutting faces that are disposed along the outside of said line of curvature of said elongated ceramic element without physical separation of said segments at their abutting faces.   
     
     
       2. An elongated ceramic element in accordance with claim 1 wherein said preload force does not exceed that preload force which will compress said segments to greater than about 20% of their maximum compressive strength. 
     
     
       3. An elongated ceramic element in accordance with claim 1 wherein said tension means forcing said segments toward each other is a nonceramic material. 
     
     
       4. An elongated ceramic element in accordance with claim 1 wherein said ceramic comprises alumina. 
     
     
       5. An elongated ceramic element in accordance with claim 4 wherein said alumina has a purity of greater than about 85%. 
     
     
       6. An elongated ceramic element in accordance with claim 1 wherein said ceramic segments are substantially identical to one another and each has an opening extending between its opposite flat and parallel surfaces, said openings in said segments being in register and said tension means extending therethrough. 
     
     
       7. An elongated ceramic element in accordance with claim 1 wherein each of the abutting flat faces of said ceramic segments is flat to within about 0.0002 inches.