Breviary Technical Ceramics






7.4 Design for Strength

Manufacturers and users currently assess the mechanical loading capacity of ceramic products in four ways:

  1. by experience (intuition),
  2. through the analytical calculation of stress distribution or
  3. the numerical calculation of stress distribution, or
  4. again through the calculation of stress distribution and, based on this, the local distribution of failure probability obtained through statistical methods.

The effort required for the strength-oriented design of a part increases from 1 to 4. The degree of utilisation of the material properties also increases however, through which some engineering solutions may become possible for the first time.

The design of ceramic parts for long-term use or subject to fatigue stress can be carried out using the same process. However, since the failure of these materials is generally the result of crack initiation and crack growth phenomena, the application of fracture mechanics in combination with numerical calculation methods and statistical failure models is recommended.

For many less critical applications, intuitive knowledge and approximate calculation are used in practice for the design of the part as well as the choice of material. The conditions of use are also taken into account, and the part designed accordingly. Intuitive knowledge develops out of years of experience of both the design of ceramic parts and of their behaviour in operation. Many basic rules for the design of ceramic materials (for example, compressive stress is OK, tensile stresses are critical, notches are critical, etc.) are a result of this experience. However, a mathematical description is not given here.


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