Enhancing Trapezoidal Threads Using a Parametric Numerical Approach

2015 ◽  
Author(s):  
Timothy Galle ◽  
Wim De Waele ◽  
Patrick De Baets
Keyword(s):  
Internal Pressure ◽  
Load Distribution ◽  
Static Load ◽  
Numerical Approach ◽  
Gap Size ◽  
Performance Parameters ◽  
Taper Angle ◽  
Axial Tension ◽  
Threaded Connections ◽  
Geometric Changes

A parametric program designed for modeling tapered, trapezoidal threaded connections is used in combination with Abaqus to investigate the behavior of couplings subjected to static load combinations containing make-up, axial tension and internal pressure. Three criteria are defined and used to quantify the performance of the connection: load distribution, helical gap size between the threads and the amount of global plasticity. From these parameters, the load distribution provides valuable information about the effectiveness of the load bearing characteristics of the thread and can be used to detect possible overstressing of the connection. The helical gap size is used to estimate its tendency to provide a leak tight thread seal, while the global plasticity reflects the total amount of plastic deformation within the connection. During the investigation, the effects of taper angle, load flank angle, wall thickness, size of threads and initial thread clearance are considered. The presented modeling approach consists of three parts. First, the optimal make-up position for a trapezoidal threaded 4.5 inch TN80 connection is calculated using the plasticity criterion. Next, the results for the three performance parameters as a function of both axial tension and internal pressure are discussed. Finally, after investigating the various isolated effects induced by geometric changes, a newly defined, enhanced threaded geometry is suggested and compared with the standardized API-buttress thread.

Finite Element Analysis of Load Distribution of Threaded Connections Made of Dissimilar Materials in High Pressure Facilities

2008 ◽  
Author(s):  
Takuya Sato ◽  
Kenji Yamamoto ◽  
Rixing Li ◽  
Hiroteru Ando
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Internal Pressure ◽  
Concentration Factor ◽  
Load Distribution ◽  
Dissimilar Materials ◽  
Pressure Vessels ◽  
Friction Forces ◽  
Threaded Connections ◽  
Similar Materials

Threaded connections are often used for pressure vessels in high pressure services, and they must be designed to resist the shear forces due to initial tightening and internal pressure. Many investigations of the load distribution in threaded connections have been conducted. One of the most basic investigations was the work of Sopwith, and a design formula was developed. The High Pressure Gas Safety Institute of Japan (KHK) design guide provides design methods based on a modification of Sopwith’s formula for threaded connections. These methods are limited to threads made of similar materials. However, in order to prevent such problems as seizing or corrosion, threaded connections sometimes use dissimilar materials for the female and male threads. In this case, it is necessary to determine whether the modified Sopwith formula can be applied or not. In this paper, linear finite element analyses were performed to calculate the load distribution in threaded connections of dissimilar materials, and the results were compared with those of the modified Sopwith formula. The contact pressure and the friction forces on the surfaces of the threads were considered in the analyses. Two load conditions, the initial tightening and the internal pressure, were considered. From these analyses, the following conclusions were obtained: (1) In practical material combinations with an elastic modulus ratio of 0.5∼2.0, the load concentration factor for threaded connections of dissimilar materials was almost the same as that for threaded connections of similar materials. In other words, it is not necessary to consider the effects of the material combinations in threaded connection design. (2) The load concentration factors were dependent on the load type. The load concentration factor under internal pressure was smaller than that under initial tightening.

The Effect of Axial Tension and Borehole Curvature on Torsion Limit of Drill String Threaded Connections

2021 ◽  
pp. 105555
Author(s):  
Feng Chen ◽  
Yonghao Huo ◽  
Haiyi Zhao ◽  
Qinfeng Di ◽  
Wenchang Wang ◽  
...  
Keyword(s):  
Drill String ◽  
Axial Tension ◽  
Threaded Connections

scholarly journals Comparison of Numerical Analyses with a Static Load Test of a Continuous Flight Auger Pile

2014 ◽  
Vol 22 (4) ◽  
pp. 1-10 ◽  
Author(s):  
Michal Hoľko ◽  
Jakub Stacho
Keyword(s):  
Load Distribution ◽  
Static Load ◽  
Numerical Models ◽  
Load Test ◽  
Numerical Analyses ◽  
Static Load Test ◽  
Material Models ◽  
The Common ◽  
Constitutive Material ◽  
The Impact

Abstract The article deals with numerical analyses of a Continuous Flight Auger (CFA) pile. The analyses include a comparison of calculated and measured load-settlement curves as well as a comparison of the load distribution over a pile's length. The numerical analyses were executed using two types of software, i.e., Ansys and Plaxis, which are based on FEM calculations. Both types of software are different from each other in the way they create numerical models, model the interface between the pile and soil, and use constitutive material models. The analyses have been prepared in the form of a parametric study, where the method of modelling the interface and the material models of the soil are compared and analysed. Our analyses show that both types of software permit the modelling of pile foundations. The Plaxis software uses advanced material models as well as the modelling of the impact of groundwater or overconsolidation. The load-settlement curve calculated using Plaxis is equal to the results of a static load test with a more than 95 % degree of accuracy. In comparison, the load-settlement curve calculated using Ansys allows for the obtaining of only an approximate estimate, but the software allows for the common modelling of large structure systems together with a foundation system.

Efficient numerical modelling for the design of friction damped braced steel plane frames

1989 ◽  
Vol 16 (3) ◽  
pp. 211-218 ◽  
Author(s):  
A. Filiatrault ◽  
S. Cherry
Keyword(s):  
Numerical Modelling ◽  
Performance Index ◽  
Load Distribution ◽  
Structural Response ◽  
Computer Time ◽  
Numerical Approach ◽  
Braced Frames ◽  
Friction Damping ◽  
Braced Frame ◽  
Brake Lining

A novel friction damping system for the aseismic design of framed buildings has been proposed by Canadian researchers. The system has been shown experimentally to perform very well and is an exciting development in earthquake resistant design.The design of a building equipped with the friction damping system is achieved by determining the optimum slip load distribution to minimize structural response. The optimum slip load distribution is usually determined using the general nonlinear dynamic computer program DRAIN-2D, which requires extensive computer time and is not practical for most design offices.This paper describes a new, efficient, numerical modelling approach for the design of friction damped braced frames. The hysteretic properties of the friction devices are derived theoretically and included in a friction damped braced frame analysis program, which is adaptable to a microcomputer environment. The optimum slip load distribution is determined by minimizing a relative performance index derived from energy concepts. The new numerical approach is much more economical to use than DRAIN-2D and is of great value for the practical design of friction damped braced frames. Key words: braced frames, brake lining, performance index, damping, dynamics, earthquakes, energy, friction.

Static load distribution analysis of ball screws with nut position variation

2020 ◽  
Vol 151 ◽  
pp. 103893 ◽  
Author(s):  
Chang Liu ◽  
Chunyu Zhao ◽  
Xianli Meng ◽  
Bangchun Wen
Keyword(s):  
Load Distribution ◽  
Static Load ◽  
Distribution Analysis

Low Order Static Load Distribution Model for Ball Screw Mechanisms Including Effects of Lateral Deformation and Geometric Errors

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Bo Lin ◽  
Chinedum E. Okwudire ◽  
Jason S. Wou
Keyword(s):  
Load Distribution ◽  
Static Load ◽  
High Order ◽  
Contact Model ◽  
Ball Screw ◽  
Distribution Model ◽  
Computational Time ◽  
Geometric Errors ◽  
Lateral Deformation ◽  
Low Order

Accurate modeling of static load distribution of balls is very useful for proper design and sizing of ball screw mechanisms (BSMs); it is also a starting point in modeling the dynamics, e.g., friction behavior, of BSMs. Often, it is preferable to determine load distribution using low order models, as opposed to computationally unwieldy high order finite element (FE) models. However, existing low order static load distribution models for BSMs are inaccurate because they ignore the lateral (bending) deformations of screw/nut and do not adequately consider geometric errors, both of which significantly influence load distribution. This paper presents a low order static load distribution model for BSMs that incorporates lateral deformation and geometric error effects. The ball and groove surfaces of BSMs, including geometric errors, are described mathematically and used to establish a ball-to-groove contact model based on Hertzian contact theory. Effects of axial, torsional, and lateral deformations are incorporated into the contact model by representing the nut as a rigid body and the screw as beam FEs connected by a newly derived ball stiffness matrix which considers geometric errors. Benchmarked against a high order FE model in case studies, the proposed model is shown to be accurate in predicting static load distribution, while requiring much less computational time. Its ease-of-use and versatility for evaluating effects of sundry geometric errors, e.g., pitch errors and ball diameter variation, on static load distribution are also demonstrated. It is thus suitable for parametric studies and optimal design of BSMs.

1G1 Analysis of Load Distribution in Threaded End of Pressure Cylinder in High Pressure Facilities : Influence of the taper angle

2014 ◽  
Vol 2014 (0) ◽  
pp. _1G1-1_-_1G1-2_
Author(s):  
Mitsuo KOBAYASHI ◽  
Syouhei KANEKO ◽  
Katsumi FUKUDA ◽  
Kenbai KA ◽  
Yoshiki GOTOH ◽  
...  
Keyword(s):  
High Pressure ◽  
Load Distribution ◽  
Taper Angle ◽  
Pressure Cylinder

Plastic Loads for Cones Subjected to Internal Pressure and Axial Tension

2017 ◽  
Author(s):  
J. Błachut ◽  
D. Sala
Keyword(s):  
Internal Pressure ◽  
Conical Shell ◽  
Plastic Instability ◽  
Combined Loading ◽  
Elastic Behavior ◽  
The Past ◽  
Axial Tension

The paper discusses envelopes of combined loading corresponding to: (i) first yield (ii) plastic load, and (iii) plastic instability load. The latter two were researched in the past but for a single load, only. The past idea has been expanded in the paper to two, practically relevant, simultaneously acting loads. Conical shell serves here as an example. It is shown that the ratio of area of plastic load envelope to the area associated with the first-yield envelope is 3.2 whilst the similar ratio of plastic instability to the first-yield envelope amounts to 25.8. This indicates ‘a modest’ (320 %) increase of possible range of loading, and a substantial reserve of strength above the end-of-elastic behavior (approx. 26-times).

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