International Journal of Modern Trends in Engineering and Research e-issn No.: , Date: April, 2016

Transcription

1 International Journal of Modern Trends in Engineering and Research e-issn No.: , Date: April, 2016 Tie Rod Analysis Using FEA And Use Of Buttress & Acme Threads Tie Rod Analysis In Automobile Prof. Saiprasad R.Mandale1, Prof. Arshad Rashid2, Prof. Karan Sharma3 1 Mechanical Engineering, MMANTC, Malegaon, mandalesai@gmail.com 2 Mechanical Engineering, MMANTC, karanu.me@gmail.com 3 Mechanical Engineering, MMANTC, arshad.rmech@gmail.com Abstract Automobile Tie rod analysis carried out using FE tool for finding out its load carrying capacity and deformation. As most of cases tie rod fail due to static loading and reaction forces from road. If stresses and vibration causing due to it are excessive system may fails. So it s necessary to identify structural behavior. This paper on analysis on structural analysis using FEA tool and analysis of failure strength of acme and buttress thread used in tie rod on M.S.rod results of tensile rupture experiments tie rods having Buttress and Acme thread to determine ultimate load as well as deformations. The results of these experiments suggest the least number of turns of the thread engagement for prevent the breakdown of threaded mild steel ties. Keywords- FEA; Modal FEA; Forces coming on tie rod. I. INTRODUCTION Tie rod of Steering system connects center link to the steering knuckle in conventional suspension system and rack to the steering knuckle in McPherson suspension system. Tie rod generally gets force from rack and transfer it to the steering knuckle to turn the wheels. Tie rod is a circular rod with threaded part, Outer end and inner end. Tie rod is mostly made up of alloy steel. Failure of tie rod may cause instability of vehicle and can cause an accident. So it s important to check the strength of tie rod. The load coming on tie rod is mostly compressive. The efforts required where car is moving are comparatively less with stationary car. The working strength of the tie rod is that of the product of the allowable working stress and the minimum cross-sectional area.if the threads are cut into a cylindrical rod that minimum area can be found at the root of the thread. Rods are often made thicker at the ends and this then means that the tie rod does not become weaker when the threads are cut into it.tie rods are connected at the ends in various ways. But it is desirable that the strength of the connection should be at least an equal strength to that of the rod. The tie rod transmits force from the steering center link or the rack gear to the steering knuckle. This will cause the wheel to turn. Failure of tie rod may occur due to improper material selection, poor design, fatigue load and wear of tie rod. Also the indications given by the tie rod before failure is very less so it can be risky. Figure

2 Figure 2 II. NEED OF ANALYSIS The overall purpose of Tie-rod is to transmit the motion from steering arm to steering knuckle and sustain the forces and vibrations caused by bumps from tires due to uneven road surfaces.the key areas for modification are identified. The main task in this study is to find the deformation and stresses induced in the Tie-rod. The load coming on tie rod is mostly compressive. The working strength (Maximum load carrying capacity P= σ.a) of the tie rod is that of the product of the allowable working stress and the minimum cross-sectional area. Tie rod is a circular rod with threaded part, Outer end and inner end. Shear and bending failure occurring in the engaged thread teeth on a tie rod in service, if the threads are cut into a cylindrical rod that minimum area can be found at the root of the thread. Rods are often made thicker at the ends and this means that the tie rod does not become weaker when the threads are cut into it. Tie rods are connected at the ends in various ways. But it is desirable that the strength of the connection should be at least an equal strength to that of the rod.suraj Joshi et al [1] concluded from their work that in order to minimize the probability of shear and bending failure occurring in the engaged thread teeth on a steel tie rod in service, the number of engaged thread turns should be kept as low as possible. A.H. Falah et al [2] the primary cause of failure of the tie rod was likely material deficiency. Failure of tie rod may cause instability of vehicle and can cause an accident III. FE-MODEL SIMULATION Finite Element Analysis (FEA) is an important engineering tool used to assist in approximating and verifying how a component will react under various external and internal loading conditions. Figure 3: Tie rod end assembly Figure 4: -Mesh of Tie rod assembly 1036

3 Figure 5: FEM model displacement Figure 6: -FEM model stres distibution The result of simulation by FEA shown in the fig.5 and 6 Numerical calculations is performed with aid of the FEM (software Algor). All necessary input information regarding FEM analysis is shown below. Maximum stress value is lower than ultimate stress the component area shown in red is subjected to high stress due to minimum area cause due to threading. IV. USE OF BUTTRESS &ACME THREADS Analysis of thread strength necessary for structural safety, various thread are available now a day in this article we are going to analyses buttress and acme threads. Figure 7: -Threaded rod 1037

4 Figure 7(a): -Butteres thread Figure 7(b): Acme thread V. THREAD TESTING Tensile tests were conducted for two, three, four, five and six engaged thread turns, and in order to consecutive specimens. (a) Butteres thread testing: I) (For five and six engage thread pulling force are 150kN and 167kNand tie road form neck before failure The internal thread teeth on sleeve and the external thread teeth on the tie rod body were still engaged. In five threads and six Threads the break position was occurred in 10turns and 18 turns) in both cases the break is away from the end. These shows buttress thread steel tie rod having less strength to bare the load on five and sixth engaged thread turn position. II) The critical value was occurred on the four engaged thread position. Where the damaged portion of the tie rod body in thread position is more than fourth thread is engaged. In case of buttress threads to maintain the safe position four engaged thread is considered. Otherwise the failure position occurs at the fifth and sixth threaded connection. Figure 8: Result of tensile test on Bitters thread (b) Acme thread: Figure 9: Result of tensile test on Acme thread 1038

5 When acme thread are tested for two,three and four turns failure found on threaded tie rod failure in shear and pull occur on threaded tie rod, Whereas for six turns strength at breaking is 162kN at breaking with neck formation observed, The internal thread teeth on sleeve and the external thread teeth on tie rod were still engaged in good condition In six threads the break position was occurred in 18 turns in this case the break position is placed away from the end face These Shows acme thread steel tie rod having less strength to bare the load on sixth engaged thread turn position. The critical value was occurred on the five engaged thread position. Where the damaged portion of the tie rod body in thread position is more than five threads is engaged. In case of acme threads to maintain the safe position five engaged thread is considered. Otherwise the failure position occurs at the sixth threaded connection. CONCLUSION 1. Tie rod fails at junction of thread as threaded area having minimum area. 2. If threads numbers are engage more than tie rod will fail by formation of neck 3. From the presented results we can conclude that the distribution of deformation and stress do not exceed the upper limit value and that there are neither damages nor surface defects after performed tensile test.using FEM made possible to predict the whole tensile test of tie rod assembly. VI. REFERENCE- [1] Alagić I.: Design and testing of ball joint No using FEA, 8th International Research/Expert Conference TMT 2004, Neum, B&H, September, [2] Alagic I. : Using the Finite Element Method (FEM) in order to Optimize of Clamping Force for Jaw- Chucks during Machining Process of the Brake Disc, 9th International Research/Expert Conference TMT 2005, Antalya, Turkey, September, [3] Wei Duan a, Suraj Joshi b, Failure analysis of threaded connections in large-scale steel Tie rods (2011). [4] Yang X, Yang Z. Steel Tie Rod GB/T The People s Republic of China National Standards; [5] Surtees JO, Nip TF. Use of threaded rod compression stiffening in end plate connections. [6] Anthony Delugan, Understanding the Buckling behavior of a Tie-Rod using Nonlinear Finite Element, Analysis. Rensselear Polytechnic Institute.hartford, [7] Thi Mai Hoa Luong, Identification of the tensile force in tie-rods using modal analysis tests, University does Minho, 2010 [8] Michael Adam Kaiser, Advancements in the Split Hopkinson Bar, Test Faculty of the Virginia Polytechnic Institute, Blacksburg, Virginia May 1,

6