IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 05, 2015 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 1098 Analysis of Plates Welded With Stiffeners under Harmonic Loading Ch.Goutham 1 D.Vijay Praveen 2 Dr.M.Venkateswara Rao 3 1 PG Student 2 Assistant Professor 3 Head of the Department & Professor 1,2,3 Mechanical Department 1,2,3 Bapatla Engineering College, Bapatla Abstract— In this paper we are going to study the structures of plate with spot welded stiffeners using Ansys(14.5) software under the loading conditions for Harmonic analysis. These structures mainly consists two parts i.e. Upper and lower part which are joint together using spot weld. Spot welding is most preferred and widely used method for joining the metal sheets in automotive and many other industrial assembly operations. The finite element (FE) modelling of plates with spot welded stiffened structures and its Harmonic analysis is research area of this paper. In FEA study, modal analysis method is used to find the natural frequencies of all test structural models. Key words: Stiffeners, Harmonic Loading, Spot welding I. INTRODUCTION A spot weld is materialized by clamping the sheets with two pincers while applying a force and transmitting current. The electrical resistance of contacting sheets generates sufficient heat at the metal surfaces to melt the metal. Thus nugget develops and sheet metals are joined. Automotive bodies and many other structures are composed of metal sheets joined by spot welds. Spot weld joints provides localized connection thus lead to high stress concentration in the joined plates. Excessive stresses and premature failure occurs due to improper design. A designer significantly concentrates the strength of component by introducing the changes in its geometry and weld patterns that will reduce the vibration of the structural models. Also increases the strength of the structures. Stiffeners are secondary plates or sections which are attached to beam webs or flanges to stiffen them against out of plane deformations. Longitudinal web stiffeners, which are aligned in the span direction and Transverse stiffeners, which are aligned normal to the span direction of the beam. The optimum design of geometry and weld patterns can be obtained optimal performance i.e. good strength to the composed structures. II. LITERATURE REVIEW In the literature, there are some studies about Vibration Analysis of stiffened shells and plates with stiffeners welded to them. Pravin Nana Jadhav [1], discussed about the effect of spot weld patterns and profiles of stiffeners on the vibration characteristics of plates with spot welded stiffeners. There are some studies about optimization of spot welded structures. Ahmet H Er`tas, Fazil O.Sonmez [2] optimized the spot welded plates for maximum fatigue life. They suggest that number of spot welds significantly affects the fatigue strength. Sheet thickness and material are studied to the strength requirements of the structures. The effect of the size of the welds diameter and pitch of the weld on the account of absorbed energy is studied [3]. The residual stresses produced in each nugget have significant effect on the natural frequency of the plate, where natural frequency increases when residual stresses are included. This effect varies depending on the boundary conditions of the plate and on the distribution of the weld spots [4]. Guidelines for spot welds CWELD and ACM2 are analysed and proposed [5]. The effect of laser spot welding technique and the design adjustments are studied [6-7]. The effect of growth in nugget size with spot welding has a great impact in natural frequencies of the model [8]. The behaviour of a spot welded structure under dynamic loads is strongly influenced by the number and locations of the resistance spot welds [9]. Some researchers have published regarding vibration analysis of stiffened laminated plates and shells. It was found that stiffeners profile and its arrangement have great effect on the natural frequencies and mode shapes of the plates. Experimental analysis of composed structures, including setup is studied to find the natural frequencies using FFT analyzer This study of harmonic analysis of plates with spot welded stiffeners includes study of spot weld arrangement and stiffener parameters such as profile, dimensions and arrangement. Good agreement of optimum design of structure due to FEA study. III. DEFINITION OF HARMONIC RESPONSE ANALYSIS Any sustained cyclic load will produce a sustained cyclic response (a harmonic response) in a structural system. Harmonic response analysis gives you the ability to predict the sustained dynamic behavior of your structures, thus enabling you to verify whether or not your designs will successfully overcome resonance, fatigue, and other harmful effects of forced vibrations. Three harmonic response analysis methods are available: full, reduced, and mode superposition. (A fourth, relatively expensive method is to do a transient dynamic analysis with the harmonic loads specified as time history loading functions. The ANSYS/Linear Plus program allows only the mode superposition method. Before we study the details of how to implement each of these methods, let's explore the advantages and disadvantages of each method. The full method is the easiest of the three methods. It uses the full system matrices to calculate the harmonic response (no matrix reduction). The matrices may be symmetric or unsymmetric. The advantages of the full method are: It is easy to use, because you don't have to worry about choosing master degrees of freedom or mode shapes. It uses full matrices, so no mass matrix approximation is involved. It allows unsymmetric matrices, which are typical of such applications as acoustics and bearing problems. It calculates all displacements and stresses in a single pass. It accepts all types of loads: nodal forces imposed (nonzero) displacements, and element loads (pressures and temperatures).It allows effective use of solid model loads. A disadvantage of the full method is that no