Accurate estimation of clamping force is a major issue in the high-strength bolted joints. This study proposes a methodology to predict this force based on the measurement of the ultrasonic velocity using the pulse-echo method. The clamping forces of the cylinder head and main bearing cap bolts were also measured in a high-speed marine diesel engine using the torque–angle strategy. The new and used bolts were considered in both coated and uncoated conditions to investigate their effects on the clamping forces. The variations in the ultrasonic length, tightening torque, and bolt preload were measured in all stages of the assembly process. Results showed that the partial plastic deformation of threads reduced the clamping force in the first stage of tightening of new bolts. In the used bolts, preload was affected by an increase in the coefficient of friction under the bolt head. Moreover, the lack of zinc phosphate coating also increased the coefficient of friction and reduced the preload. It was concluded that the mentioned reduction can be successfully controlled by the torque–angle method. The comparison between the results of the present paper and previous studies showed that axial stress had a significant influence on the changes in the ultrasonic velocity. However, the presence of shear stress can further decrease the wave velocity. Finally, a relationship between the ultrasonic velocity variations in terms of the applied stress (up to the plastic region) was obtained in a real assembly process, and the clamping force can be estimated with an accuracy of 10%.

准确估计夹紧力是高强度螺栓连接中的一个主要问题。本研究提出了一种基于使用脉冲回波方法测量超声波速度来预测该力的方法。气缸盖和主轴承盖螺栓的夹紧力也在高速船用柴油发动机中使用扭矩-角度策略进行测量。在涂层和未涂层​​条件下考虑新的和使用过的螺栓，以研究它们对夹紧力的影响。在组装过程的所有阶段都测量了超声波长度、拧紧扭矩和螺栓预紧力的变化。结果表明，螺纹的局部塑性变形降低了新螺栓拧紧第一阶段的夹紧力。在使用过的螺栓中，预紧力受到螺栓头下摩擦系数增加的影响。此外，缺乏磷酸锌涂层也增加了摩擦系数并降低了预紧力。得出的结论是，提到的减少可以通过扭矩 - 角度方法成功控制。本文结果与以往研究结果的比较表明，轴向应力对超声速度的变化有显着影响。然而，剪切应力的存在会进一步降低波速。最后，在实际装配过程中获得了超声波速度变化与施加的应力（直至塑性区域）之间的关系，并且可以以 10% 的精度估计夹紧力。缺少磷酸锌涂层也增加了摩擦系数并降低了预紧力。得出的结论是，提到的减少可以通过扭矩 - 角度方法成功控制。本文结果与以往研究结果的比较表明，轴向应力对超声速度的变化有显着影响。然而，剪切应力的存在会进一步降低波速。最后，在实际装配过程中获得了超声波速度变化与施加的应力（直至塑性区域）之间的关系，并且可以以 10% 的精度估计夹紧力。缺少磷酸锌涂层也增加了摩擦系数并降低了预紧力。得出的结论是，提到的减少可以通过扭矩 - 角度方法成功控制。本文结果与以往研究结果的比较表明，轴向应力对超声速度的变化有显着影响。然而，剪切应力的存在会进一步降低波速。最后，在实际装配过程中获得了超声波速度变化与施加的应力（直至塑性区域）之间的关系，并且可以以 10% 的精度估计夹紧力。得出的结论是，提到的减少可以通过扭矩 - 角度方法成功控制。本文结果与以往研究结果的比较表明，轴向应力对超声速度的变化有显着影响。然而，剪切应力的存在会进一步降低波速。最后，在实际装配过程中获得了超声波速度变化与施加的应力（直至塑性区域）之间的关系，并且可以以 10% 的精度估计夹紧力。得出的结论是，提到的减少可以通过扭矩 - 角度方法成功控制。本文结果与以往研究结果的比较表明，轴向应力对超声速度的变化有显着影响。然而，剪切应力的存在会进一步降低波速。最后，在实际装配过程中获得了超声波速度变化与施加的应力（直至塑性区域）之间的关系，并且可以以 10% 的精度估计夹紧力。