Experimental Verification of Finite Element Approach for Designing Robust Bolted Joints Using Titanium and Titanium Alloy Bolts at Elevated Temperature

2014 ◽  
Author(s):  
Toshimichi Fukuoka ◽  
Masataka Nomura ◽  
Takao Hirai
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Titanium Alloy ◽  
Elevated Temperature ◽  
Carbon Steel ◽  
Thermal Load ◽  
Thermal Contact ◽  
Bolted Joints ◽  
Element Formulation ◽  
Clamping Force

When bolted joints are subjected to thermal load, variations of the bolt clamping force are of great concern from the view point of joint safety. It is considered that titanium and titanium alloy bolts have high possibility for clamping machines and structures subjected to thermal load. Its specific characteristic of low thermal expansion expectantly works well to mitigate the reduction of bolt clamping force caused by thermal expansion. Low weight, low Young’s modulus and high resistance to corrosion of titanium and titanium alloy are also highly attractive. In this paper, the effectiveness of the numerical method proposed in the previous study is validated by experiments using bolted joints composed of titanium bolts and carbon steel plates. Then, thermal and mechanical behaviors of titanium and titanium alloy bolts are analyzed by finite element analysis in order to examine the applicability of those bolts for the joints under elevated temperature. Numerical analyses are executed as in the manner introduced in the previous paper, i.e., by incorporating the thermal contact coefficient into the finite element formulation. Numerical results suggest that titanium and titanium alloy bolts are favorably applied to the joints made of carbon steel whose clamping forces are likely to decrease under elevated temperature.

Evaluation of Thermal and Mechanical Behaviors of Bolted Joints Made of Titanium and Titanium Alloy and its Application to Robust Joint Design

2013 ◽  
Author(s):  
Toshimichi Fukuoka ◽  
Masataka Nomura ◽  
Yusuke Takasugi
Keyword(s):  
Finite Element ◽  
Titanium Alloy ◽  
Titanium Alloys ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Thermal Contact ◽  
Bolted Joints ◽  
Element Formulation ◽  
Mechanical Behaviors ◽  
Threaded Fasteners

Titanium and titanium alloys have some excellent characteristics when used for the parts and components of machines and structures. As for bolted joints, however, they are limitedly used mainly due to the high cost. Its specific characteristics, e.g., low weight and high resistance to corrosion, are highly attractive from the engineering point of view. In this paper, thermal and mechanical behaviors of the bolted joints made of titanium or titanium alloy are comprehensively evaluated by finite element analysis, aiming at its broader use by utilizing the distinctive features of small coefficient of linear expansion and Young’s modulus. As a first step, thermal contact coefficients at the interface composed of titanium, titanium alloys and other engineering materials are measured, and then the empirical equations for evaluating the coefficients are derived in the same form proposed in the previous papers. In the next place, numerical analyses are executed by incorporating the thermal contact coefficients into the finite element formulation. Numerical results suggest that threaded fasteners made of titanium alloys are favorably applied to the joints whose clamping forces are likely to decrease when subjected to thermal load. It was also found that the aforementioned threaded fasteners are effective, owing to its low Young’s modulus, for reducing the stress amplitude generated by alternating external forces.

Finite Element Simulation of the Upset Welding Process

1991 ◽  
Author(s):  
H. A. Nied
Keyword(s):  
Finite Element ◽  
Titanium Alloy ◽  
Elevated Temperature ◽  
Welding Process ◽  
Element Model ◽  
Stress Fields ◽  
Element Formulation ◽  
Deformation Characteristics ◽  
Element Simulation ◽  
Major Process

A finite element model of an elevated temperature upset welding process was developed to simulate the process and to study the role and sensitivity of the major process parameters. Particular attention was focused on the deformation characteristics by studying the displacement and stress fields generated for the purpose of obtaining a better understanding of this solid-state welding process. The paper describes the finite element formulation, the experiments used to validate the modeling, and a selected application for upset welding of a titanium alloy.

Finite Element Simulation of the Upset Welding Process

1993 ◽  
Vol 115 (1) ◽  
pp. 184-192 ◽  
Author(s):  
H. A. Nied
Keyword(s):  
Finite Element ◽  
Titanium Alloy ◽  
Elevated Temperature ◽  
Welding Process ◽  
Element Model ◽  
Stress Fields ◽  
Element Formulation ◽  
Deformation Characteristics ◽  
Element Simulation ◽  
Major Process

A finite element model of an elevated temperature upset welding process was developed to simulate the process and to study the role and sensitivity of the major process parameters. Particular attention was focused on the deformation characteristics by studying the displacement and stress fields generated for the purpose of obtaining a better understanding of this solidstate welding process. The paper describes the finite element formulation, the experiments used to validate the modeling, and a selected application for upset welding of a titanium alloy.

Numerical Simulation of Self-Loosening of Bolted Joints under Cyclic Transverse Loads

2014 ◽  
Vol 487 ◽  
pp. 488-493 ◽  
Author(s):  
Shi Yuan Hou ◽  
Ri Dong Liao
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Step Length ◽  
Shear Loading ◽  
Bolted Joints ◽  
Shear Load ◽  
Clamping Force ◽  
The Finite Element Method ◽  
Force Amplitude ◽  
Transverse Loads

Self-loosening is one of the major failure reasons for bolted joints. Utilizing the finite element method, a 3-Dimension finite element model under dynamic shear loading is built to study the loosening of bolted fastener phenomenon. And the effect of increment step length, initial clamping force, amplitude of the shear load, thread tolerance, friction coefficients on the loosening process are studied.

Finite Element Analysis of the Thermal and Mechanical Behaviors of Bolted Joint

2003 ◽  
Author(s):  
Toshimichi Fukuoka
Keyword(s):  
Finite Element ◽  
Heat Flow ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Thermal Contact ◽  
Numerical Procedure ◽  
Pressure Vessels ◽  
Element Formulation ◽  
Bolted Joint ◽  
Flow Through

Mechanical and thermal behaviors of the bolted joint subjected to thermal load are analyzed using axisymmetric FEM, where the effects of thermal contact resistance at the interface and heat flow through small gaps are taken into account in order to accurately evaluate the variations of bolt preloads. It is expected that the numerical procedure proposed here provides an effective means for estimating the strength of such critical structures as internal combustion engines, pressure vessels, steam and gas turbines, etc. An empirical equation that can compute the thermal contact coefficient at the interface composed of common engineering materials has been proposed in the previous paper. In this study, a simple equation for evaluating the amounts of heat flow through small gaps is shown by defining apparent thermal contact coefficient. A finite element approach has been established by incorporating the aforementioned thermal contact coefficients into the finite element formulation. By use of the FE code, it is shown that among various thermal properties, coefficient of linear expansion has dominant effects on the variations of bolt preloads. The validity of the numerical approach is demonstrated by experimentation.

Numerical Analysis of the Mechanical Behaviors of Bolted Joint Under Thermal Load

2000 ◽  
Author(s):  
Toshimichi Fukuoka ◽  
Quantuo Xu ◽  
Kentaro Yoshida
Keyword(s):  
Heat Flow ◽  
Contact Resistance ◽  
Gas Turbines ◽  
Thermal Load ◽  
Internal Combustion Engines ◽  
Thermal Contact ◽  
Pressure Vessels ◽  
Element Formulation ◽  
Bolted Joint ◽  
Flow Through

Abstract A bolted joint is frequently used in practical applications under thermal load, such as in internal combustion engines, steam and gas turbines, pressure vessels, etc. In order to accurately evaluate the thermal stresses thus produced, the effects of thermal contact resistance at the interface and the heat flow through small gaps, which exist around the bolted joint, must be taken into account. An empirical equation for the thermal contact co-efficient at the interface composed of similar materials was presented in a previous paper. In this study, the thermal contact coefficient is measured for the case of dissimilar materials using the same procedure. Further, a simple equation for apparent thermal contact coefficient is proposed to calculate the amount of heat flow through small gaps. By incorporating the effects of such contact resistance into the finite element formulation, thermal behaviors of a bolted joint with typical configuration are to be analyzed as elastic contact problems in the transient temperature field. It is shown that among various factors, coefficient of linear expansion has a dominant effect on the variations of bolt stress.

A Study of Early Stage Self-Loosening of Bolted Joints

2001 ◽  
Author(s):  
Yanyao Jiang ◽  
Bin Huang ◽  
Hua Zhao ◽  
Chu-Hwa Lee
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Early Stage ◽  
Three Dimensional ◽  
Cyclic Strain ◽  
Bolted Joints ◽  
Cyclic Plasticity ◽  
Clamping Force ◽  
Element Analysis ◽  
Cyclic Plasticity Model

Abstract Both experimental investigation and finite element analysis were conducted to explore the mechanisms of the early stage self-loosening of bolted joints under transverse cyclic loading. The nuts were glued to the bolts using a strong thread locker in the self-loosening experiments to ensure that no backing-off of the nut occurred. Depending on the loading magnitude, the clamping force reduction ranged from 10% to more than 40% of the initial preload after 200 loading cycles. Three-dimensional elastic-plastic finite element analysis was conducted with the implementation of an advanced cyclic plasticity model. The finite element results revealed that the local cyclic plasticity occurring near the roots of the engaged threads resulted in cyclic strain ratchetting. The localized cyclic plastic deformation caused the stresses to redistribute in the bolt, and the result was the gradual loss of clamping force with loading cycles. The finite element results agreed with the experimental observations quantitatively. Both experiments and finite element simulations suggested that the friction between the clamped plates has an insignificant influence on self-loosening.

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