The hinge beam, as the core load-bearing component of the cubic press, faces severe fatigue fracture risks under specific working conditions. The following is a detailed analysis of the factors affecting its fatigue strength and design improvements:
1. Core Factors Affecting Fatigue Strength
The literature points out that hinge beam fatigue is highly condition-specific, mainly occurring during the synthesis of sawing-grade fine grits, ultra-fine grits, and specific type-I single crystals.
Extremely High Usage Frequency (Alternating Loads): This is the most direct cause of fatigue failure. When synthesizing fine, ultra-fine, or type-I single crystals, the single synthesis time is extremely short, only 1/7 of the time required for medium-coarse grits. This means that within the same working period, the number of synthesis cycles (pressurization-holding-depressurization) for this equipment is about 5 times that of medium-coarse grit synthesis.
Cumulative Fatigue Effect: This high-frequency reciprocating operation subjects the hinge beam to massive alternating load cycles in a short period, easily leading to ear tearing or even beam body fracture, phenomena not fully considered in traditional designs for low-frequency operations (like medium-coarse grit synthesis).
Limitations of Traditional Design Philosophy: Existing hinge beam designs are mostly derived from finite element optimization focusing on static strength analysis, often neglecting the impact of fatigue strength. Such designs fall short when facing the special product synthesis involving high-frequency operations.
2. Direction and Strategy for Improved Design
To solve these problems and improve the stability and lifespan of equipment producing fine-grain diamond, the literature proposes the following improvement directions:
Introduction of More Applicable Strength Theories: For equipment dedicated to producing fine grits, the design calculation of the hinge beam should abandon simple static analysis and adopt the third and fourth strength theories. This design basis is considered more reasonable and practical when dealing with complex stress and fatigue issues.
Manufacturing Process Innovation: From Casting to Forging:
Status Quo: Due to cost and forging technology limitations, early hinge beam designs in China mostly used casting forms.
Improvement: With the improvement of forging technology, costs have significantly decreased. For high-frequency equipment, the forged hinge beam design concept should be adopted. The forging process significantly improves the density and fiber continuity of the metal material, thereby greatly enhancing fatigue strength. The literature notes that the earliest hinge-type cubic presses in the United States used forged beam structures.
Promoting "Dedicated Equipment" Design Thinking: Future design trends should not be "one machine for multiple uses," but rather creating dedicated equipment tailored to the synthesis characteristics of different superhard materials. For the high-frequency characteristic of fine-grain diamond synthesis, the fatigue strength design of the hinge beam should be specifically reinforced, rather than simply using general-purpose models.