Static Behavior of Locally Bolted Structures under Preloading Force

In aerospace, energy, and high-end manufacturing, bolted joints’ reliability is critical for system safety. Traditional models ignoring thread geometric nonlinearity and contact mechanics cause preload decay and stress concentration prediction errors, leading to failures. This study proposes a variable-thickness disk model with parameter α to characterize bolt threads. Using elastic mechanics and parametric analysis, it investigates the static response under tension and thermo-mechanical loads. Key findings reveal that the elastic modulus dominates the stress plateau and displacement distribution, with high-strength steel exhibiting a “stress homogenization effect” that mitigates concentration. The parameter α regulates the peak position and magnitude of stress and displacement, with trapezoidal threads demonstrating 32.4% lower stress concentration sensitivity than triangular threads. Thermo-mechanical coupling analysis shows that temperature elevation (20 to 100°C) reduces the peak stress by 21.6–30.2% due to material property degradation, while α exacerbates stress concentration. This research provides a theoretical framework for precise modeling of bolt threads, enabling quantitative evaluation of geometric and material parameters on static behavior, which is crucial for preload design and reliability assessment of high-end equipment under complex conditions.