Evaluation of the Clamping Force of Bolted Joints Using Local Mode Characteristics of a Bolt Head

Abstract

It is important to determine and control the clamping force of a bolted joint. Due to its simple setup, the torque control method is typically used to control the clamping force when tightening bolts. After tightening, hammer tests, ultrasonic techniques and methods employing sheet materials as sensors are often used. Many methods have been proposed, but using them to determine and control the clamping force during or after tightening bolts is labor intensive or expensive. Here we conduct impact tests with an impulse hammer combined with experimental modal analysis to determine the clamping force by interpreting the change in the local mode frequency of a bolt head in the high frequency region as a function of the clamping force. To demonstrate the applicability of our method, we also investigate its limits with regard to bolt sizes. Keywords Vibration • Non-destructive testing • Clamping force • Bolted joint • Experimental modal analysis IntroductionMultiple bolts are often used to join or restrain the components of a structure. Because loosening of these bolts may damage the structure, it is important to be able to monitor and control the clamping force of bolted joints [1]. Methods Naoki Hosoya B

Analysis of three-layer gasket performance affected by flange surface

“…A bolted flange connection is a complicated mechanical system with components that must be carefully chosen and constructed to enable dependable sealing under a variety of operating circumstances. The proper operation of the joint depends on all of the numerous components of the completed bolted flange connection [1][2][3][4][5].…”

A Review of Bolt Tightening Force Measurement and Loosening Detection

“…Analytical analysis indicates that the natural frequency (mode) of the washer decreases as the clamping force decreases [101]. Under this concept, Hosoya et al [102] suggested using local mode frequency of the bolt head to evaluate the clamping force. Experimental results verified the monotonic relationship between the bolt clamping force and the local mode frequency of the bolt head.…”

“…The smaller bolt size (or bolt mass) requires a higher frequency region of excitation in order to catch the change of the local mode frequency when the bolt clamping force changes. For joints with multiple bolts, the position of the bolt increases the difficulty in using this method and more systematic studies are needed [102]. Based on a model of a prestressed one-dimensional beam with elastic supports at both ends, the boundaries of stiffness in terms of the bolt tension is related to the natural transverse frequency-as the bolt is gradually tightened, the squared normalized natural transverse frequency experiences nonlinear-to-linear change.…”

Influence of Symmetry of Tightened Parts on the Force in a Bolted Joint

“…As part of the research into the current state of the field of bolted joints, the first phase of the literature search focused on various methods of measuring bolt preload other than the use of strain gauges, such as using ultrasound, piezoelectric sensors, special impact testing of a bolt head [1] or using automatic digital image correlation [2]. However, it is necessary to consider the fact that the measurement will take place during operation (i.e., there is influence of dynamic impacts, noise, vibrations).…”

“…As part of the research of the current state of the field of bolted joints, the literature focusing on various alternative measurement methods, such as in [1,2], was investigated In the area of this bolt placement, no suitable space was found either for the installation of the sensor, if the bearing plate was not reconstructed, or for the strain gauges. Another suitable place to mount strain gauges was on the four legs of the frame.…”