<p>Bolted joints exhibit inherent uncertainties in their contact behavior, and the existing models often struggle to accurately predict the distribution range of contact stress. To address this issue, an approximate fitting method is employed to estimate the variation range of contact stress on micro-scale contact surfaces, resulting in a cubic expression for the pressure distribution across the contact surface. Initially, assuming a cone-like contact stress distribution, a cubic mathematical equation is derived for the contact stress in bolted structures. Subsequently, using numerical simulation techniques that comprehensively account for nonlinear factors such as bolt preload and contact friction, a finite element model of the bolted structure is established to analyze the contact state and the variation trend of contact stress under load and preload conditions. Finally, based on this model, a virtual simulation model for the frame of an aluminum alloy liquid tanker truck is constructed. The simulation results reveal that the maximum discrepancy between the simulation and experimental data is 8.26 %, with an average error of 5.55 %. These findings demonstrate that the model not only accurately captures the true stress state in the bolted region but also provides theoretical support for reliability analysis in tackling complex engineering problems.</p>