Finite Element Simulation of Bar-Plate Friction Welded Joints Steel Product Subjected to Impact Loading

Transcription

1 Finite Element Simulation of Bar-Plate Friction Welded Joints Steel Product Subjected to Impact Loading Yohanes, a,* Muftil Badri, a Panji Adino, a Dodi Sofyan Arief, a and Musthafa Akbar, a a) Department of Mechanical Engineering, Universitas Riau, Pekanbaru, 28293, Indonesia *Corresponding author: yohanes_tmesin@yahoo.com Paper History Received: 1-October-215 Received in revised form: 2-November-215 Accepted: 23-Nevember-215 ABSTRACT The results of dynamic finite element simulation are presented for stress distributions in a bar-plate friction welded joints steel alloy subjected to impact loading. This paper examines the effects of different location of contact area and mass of pendulum on the penetration of bar-plate friction welded joints steel alloy at impact loading. Accurate approach of mechanical behavior such as stress distribution, stress concentration for bar-plate friction welded joints steel product subjected to impact loading is needed to experimental design. This approach is based on the finite element simulation. In the finite element simulation, the ANSYS code was employed. It was found that the impact response of bar-plate friction welded joints steel alloy is significantly influenced by location of contact area and mass of pendulum. Advanced finite element simulation approach must be applied for impact assessments of friction welded structure under impact loading, to avoid unsafe designed obtained from the static criteria. KEY WORDS: bar plate, location of contact area, mass of pendulum, impact response. 1. INTRODUCTION Friction welding has come to assume a position of importance in the fabrication industry. The advantages of the process are, among others, high reproducibility, short production time and low energy input. Friction welding has made possible welding of dissimilar metals such as titanium alloys, aluminum alloys and new materials to which the conventional welding techniques cannot be applied. A precise knowledge of the mechanical behavior of the friction welded joints subjected to impact loading is required for their further wide applications in the fabrication industry [1]. Many approaches have been outlined the research workers and they can mainly be summarized as analytical, numerical and simulation [2]. Accurate approach of mechanical behavior such as stress distribution, stress concentration for bar-plate friction welded joints steel product subjected to impact loading is needed to experimental design. This approach is based on the finite element simulation. In this study, a finite element simulation has been developed to analyze three-dimensional impact stress propagation. The friction welding parameters were maintained constant. Using the computer program, loading conditions to obtain stress distribution are examined changing the parameters such as location of contact area and mass of pendulum. 2. LITERATURE REVIEW If the uniform impact loading of cross-sectional area A, density ρ, travelling with speed v, strikes the tip of cantilever length l, and sprays laterally, then suppose the plastic hinge which force to be at distance x from the tip [3]. The equation for horizontal motion is F R = ( f 2) + my (1) where f is the acceleration of the tip, m the mass of the beam per unit length, R the shear force at distance y from the tip and F = Aρv 2. Note at the moment of impact force applied by a square ended jet is Aρvc is just the steady state force. If a lead bullet, mass m, length b moving with speed v, spreads out laterally on impinging with the cantilever tip, it wolud be necessary to treat the impact as if the bullet was a jet rather than a rigid body, then Aρb and hence x = 3bM p /m, where M p is the fully plastic bending moment. 47 Published by International Society of Ocean, Mechanical and Aerospace Scientists and Engineers

2 The last result could be obtained directly from considerations of the impulsive force F acting for time t, when impulse F, t is delivered. If there is zero shear at the hinge, F t = ( m x)u (2) where u denotes the downward speed of the centroid of length x at the end of time t. Consider the same 3D solid structure whose domain is divided in a proper manner into a number of tetrahedron elements with four nodes and four surfaces, as shown in Fig. 1. A tetrahedron element has four nodes, each having three DOFs [4]. 3. FINITE ELEMENT SIMULATION 3.1 Location of contact area and mass of pendulum Location of contact area was determined the maximum stress at the friction welded joint of bar and plate. Five locations designated as impact loading to the bar is shown in Fig. 2. location of contact area friction welded joints Figure 1: A tetrahedron element (u, v and w), making the total DOFs in a tetrahedron element twelve, as shown in Figure 1. The nodes are numbered 1, 2, 3 and 4 by the right-hand rule. The local Cartesian coordinate system for a tetrahedron element can usually be the same as the global coordinate system, as there are no advantages in having a separate local Cartesian coordinate system. In an element, the displacement vector U is a function of the coordinate x, y and z, and is interpolated by shape functions in the following form, which should by now be shown to be part and parcel of the finite element method: h ( x y, z) N( x, y z) d e U, =, (3) It was mentioned that there are six stresses in a 3D element in total. The stress components are {σ xx σ yy σ zz σ yz σ xz σ xy }. To get the corresponding strains, {ε xx ε yy ε zz ε yz ε xz ε xy }: ε = LU = LNde = Bde (4) where the strain matrix B is given by B = LN = x z y y z x z y x N (5) Figure 2: Schematic of impact loading from different location of contact area but the same mass of pendulum Four steel pendulum with different mass was adopted as the impact bodies. The dimensions mass of each pendulum are 18, 2, 22, 24 and 26 kg. 3.2 Material model Table 1 shows the physical and mechanical properties of the pendulum model obtained by properties of steel Bohler EMS 45 [4]. These properties were applied for the material model of finite element simulation. Table 1: Physical and mechanical properties of pendulum model Physical Properties Density 785 kg/m 3 Young s Modulus 2 GPa Linier Elastic Poisson s Ratio.3 Bulk Modulus GPa Shear Modulus 76.9 GPa Plasticity Yield Strength MPa Strength Ultimate Tensile Strength 72.9 MPa Bar -plate products were modeled as a single component, so that the heat affected zone (HAZ) region that occurs is ignored. However, the meshing of products focused on the welded joint. In the pendulum system simulation that has been imported is composed of three parts, the shaft of the pendulum and products as shown in Fig. 3. Axis is added for the purpose of reference pendulum to swing in simulation. Axis is defined by type (stiffness behavior) rigid, while the pendulum and the products 48 Published by International Society of Ocean, Mechanical and Aerospace Scientists and Engineers

3 defined flexible so that the non- linear and strain effects on the pendulum and products. pendulum shaft c. bar-plate product Figure 5: Finite element mesh of welded joint modeling Figure 3: Simulation system of pendulum impact The connection between the geometry of the system being simulated, there are 2 types: joints and contacts. Connection on the shaft is Body- Ground with type Fixed Support, as well as on the product side of the plate. Contact between impactor and products are defined by the type of frictionless with contact namely the front side impactor and target round- bar on the product. 3.3 Meshing and boundary conditions Meshing the pendulum and the product is applied the type tetrahedron. In general, the size of the mesh is applied automatically (default size) as shown in Fig. 4 and 5. a. impactor b. pendulum Figure 4: Finite element mesh of pendulum and impactor modeling bar-plate product The impact load that occurs in pendulum and product caused by the free fall pendulum motion in the presence of gravity, so gravity applied to y-axis direction (downward direction of t y- axis). In the analysis, simulations conducted at an interval of 1 second (end time 1 s). 3.4 Solutions The type of solutions was determined is von mises stress. In the simulation was applied three equivalent stress, the first to focus on product geometry selection, then focus on the pendulum arm, the last at the impactor. The simulation results assessed sufficient the requirements are met pendulum impact testing such as: the maximum stress location is at the welded joint on the bar-plate product, in the absence of the pendulum stress is large enough, or the yield strength of the material passes through the EMS RESULTS AND DISCUSSIONS Table 4 shows simulation result of impact stress in welded joint for different mass of pendulum. The value of stress exceeds σ u friction welded joints and base metal products. The value maximum stress that occurs in the arm and impactor limited to fracture. After the product is fracture, the stress value on the arms and impactor is negligible, due to decrease of stress. Table 4: Simulation result for different mass of pendulum No. Mass of pendulum (kg) Stress in a welded joint (MPa) Figure 6 shows the finite element simulation of stress distributions within a bar-plate friction welded joint with different location of impact loading. From the simulation results, the location, x = 1 mm produce the maximum stress at a bar plate friction welded joint, this is evidenced by experiment, that is only at x = 1 mm which cause fractures the product, while the loading 49 Published by International Society of Ocean, Mechanical and Aerospace Scientists and Engineers

4 location 4 mm to 15 mm fracture occurs only in the plate product section. For pendulum impact testing with a bar 12 mm and 3 mm thick plate loading location used is 1 mm from the surface of the plate. that is still below the allowable stress of the pendulum. The maximum stress value of impactor exceeds the allowable stress of the pendulum, so that the material impactor distinguished. Based on the graph is known that the mass of pendulum 24 kg and 26 kg, the stress that occurs in the arm decreased. The maximum stress tends to occur in the lower part of the pendulum arm. The stress concentration occurs at the bottom of the pendulum arm. The heavier pendulum head reduces the pendulum motion of the upper part because the clash happens when the impact is smaller than the other pendulum. Figure 8 shows the finite element simulation of stress distributions within a bar-plate friction welded joint with different mass of pendulum. m = 18 kg m = 2 kg Figure 6: Stress distributions within a bar-plate friction welded joint with different location of contact area Figure 7 shows the comparison of stress distributions of product, arm and impactor as a simulation results. m = 22 kg Stress (MPa) 7 bar-plate 6 product 5 4 impactor arm m = 24 kg The mass of pendulum (kg) Figure 7: Comparison of stress distributions with different mass of pendulum The allowable stress of pendulum is MPa. The overall mass of the pendulum produces the stress propagation on the arm m = 26 kg Figure 8: Stress distributions within a bar-plate friction welded joint with different mass of pendulum 5 Published by International Society of Ocean, Mechanical and Aerospace Scientists and Engineers

5 Based on simulation of stress distribution is known that at the location of loading x = 1 mm, part of the plate is not carried on the fracture of bar. Broken on the product occurred in HAZ area between the bar and plate. Distance loading location close to the welded joints cause motion HAZ fracture section in the direction of the impact force generated impactor. The mass of pendulum 24 kg declared the most favored of the other pendulum mass variations, because the value of the maximum stress that occurs in most small arms compared to 18 kg, 2 kg, 22 kg in the amount of MPa and volume of material use at least when compared to 26 kg. 5. CONCLUSIONS This study constructs the dynamic finite element simulation program considering stress distributions to simulate the bar-plate friction welded joints steel product subjected to impact loading. It was found that the impact response of bar-plate friction welded joints steel alloy is significantly influenced by location of contact area and mass of pendulum. Based on the stress distribution in different location of contact area, the pendulum impact method was confirmed to be valid to predict the impact response of a barplate friction welded joints steel product. Thus, a simple impact test by free falling pendulum motion can be used to investigated the impact response of bar-plate fiction welded joints materials. Finally, advanced finite element simulation approach must be applied for impact assessments of friction welded structure under impact loading, to avoid unsafe designed obtained from the static criteria. REFERENCES 1. T. Yokoyama Impact Tensile Strength of Friction Welded Joints Between 661 Al Alloy and AISI 145 Steel. Proceeding 3 rd International Symposium on Impact Engineering Impact Response of Materials and Structures. 2. S.K. Salwan Study of Bimaterial Armour System to Hypervelocity Attack. Proceeding 3 rd International Symposium on Impact Engineering Impact Response of Materials and Structures. 3. G. R. Liu, S.S. Quek. 23. The Finite Element Method: A Practical Course. Elsevier Science Ltd. 4. Bohler Special Steel Manual, PT. Bhinneka Bajanas Sole agent, Distributor, Stock Holder, Heat treatment Service: Published by International Society of Ocean, Mechanical and Aerospace Scientists and Engineers