Linbo Zhu

Bio: Linbo Zhu is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Bolted joint & Flange. The author has an hindex of 8, co-authored 19 publications receiving 129 citations.

Three-dimensional finite element analysis of the mechanical properties of helical thread connection

Abstract: Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.

An Introduction to the Design and Behavior of Bolted Joints

Abstract: Although the title of this book includes the word “introduction”, the treatment of the subject is extensive and complete. The material goes well beyond the coverage of bolted joint design received in a typical undergraduate machine design course. The easy-to-read text begins with the fundamentals of bolt strength, deformation, and material selection and proceeds to cover the topics of preload, torque, and stretch control. The emphasis is on practical considerations for the efficient design of joints, including cost, ease of assembly, inspection, and disassembly. This second, revised edition has expanded the coverage of corrosion, fatigue, gaskets, and ultrasonic measurement of bolt strain. Also included are discussions of the failure modes and mechanisms of bolted joints. Case histories from industry are presented throughout the text to illustrate key points. Many up-to-date references are presented at the end of each chapter to allow the reader to pursue individual topics further, if desired. The text contains several appendices with useful tables and formulas for quick reference. The author has broad experience in the subject area from many years as a consultant to the power generation and nuclear industry, active participation on society working groups such as ASME and PVRC, as well as the presentation of numerous seminars on the topic. This book would serve as a valuable desk reference for engineers concerned with the design and performance of bolted joints.

Effects of bolt threads on the stiffness of bolted joints and bolt thread and head fillet stress concentration factors

Abstract: Axisymmetric finite element analysis (FEA) was performed on bolted joints to determine the effects of the threads on the bolt and member stiffnesses. For steel members, the member stiffness decreased 37.1, 37.7, 38.2, 41.0, and 49.4 percent for the 24, 20, 16, 12, and 8-mm-dia bolts, as the magnitude of the external load was increased. The external load was increased from zero to the value that caused the bolt force to equal its proof strength. The member stiffness for aluminum members decreased by 22. 7 and 29.9 percent for the 24 and 20-mm bolts. The cast iron members had decreases of 26.9 and 32.3 percent for the 24 and 20-mm bolts. Likewise, the aluminum/cast iron members decreased in stiffness by 25.5 and 30.0 percent for the 24 and 20-mm bolts. The member stiffness with no external load applied decreased by approximately 65 percent when changing from steel to aluminum members, 53 percent from steel to cast iron, and 60 percent from steel to aluminum/cast iron. Bolt stiffness varied less than 1.4 percent over the total range of the externally applied load for each of the bolted joint models. The decrease in bolt stiffness for the 24 and 20-mm-dia bolts was approximately 4 percent when changing from steel to aluminum members, 7 percent when changing from steel to cast iron members, and 8 percent when changing from steel to aluminum/cast iron members. Comparison is made to research results which did not include the influence of the threads.