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optimization of multi-pass gmaw of steel structures using ansys and lab view.

by:VENTECH     2020-03-05
The microstructure of the metal determines its tensile strength, hardness and other mechanical properties.
, Is a function of its chemical composition, initial structure and the thermal process experienced during welding.
In theory, if the known thermal history and the metal\'s response to a specific thermal history, then the resulting micro-
Structure and mechanical performance can be predicted.
When the transverse shrinkage is uneven along the depth of the welded plate, corner deformation often occurs in the butt weld.
The limitation of strain on this deformation may result in a higher residual stress.
In arc welding, controlling angular deformation without increasing residual stress is an important task.
This is possible plastic pre-
Bending or elastic pre
Tighten the plate in the opposite direction of deformation, and then weld the plate.
For this purpose, the degree of angle distortion should be known for a specific set of operating parameters. The non-
Uniform expansion and shrinkage due to thermal cycling during welding results in residual stress in the manufactured components.
The estimation of residual stress is important to understand the bearing capacity and its stress corrosion cracking tendency.
In this paper, a new finite element model is introduced in detail, which can predict the temperature time history, angle deformation and residual stress with sufficient accuracy.
Data acquisition: Data Acquisition is the process of sampling signals that measure the physical conditions of the world, and converting the obtained samples into digital values that can be manipulated by computers.
Data Acquisition System (
Short for DAS or NASDAQ)
The analog waveform is usually converted to digital values for processing.
A sensor is a sensor that converts physical properties into corresponding electrical signals.
In most cases, the signal may need to be filtered or amplified.
Various other examples of signal regulation may be bridge completion, current or voltage excitation for the sensor, isolation, and linearity.
For the purpose of transmission, a single-ended analog signal that is more sensitive to noise can be converted to a differential signal.
After digitization, the signal can be encoded to reduce and correct transmission errors.
Industrial USB is the name of the USB protocol used in industrial environments for data acquisition, automation, and production machine control.
Recently, USB is strictly regarded as a consumer communication bus, usually used for PC peripherals.
However, the popularity of USB in the industrial field has attracted more and more attention. USB 9213 16-
The 24-bit C series ch TC, with a transmission rate of 480 Mbit/s, provides a solution for realizing portable high-speed diagnostic systems. High-
USB 9213 speed transfer rate is 480 Mbit/s, easy to install due to plugand-
Playback portability.
Residual stress: Residual stress is the stress that occurs during the unloading phase of the locked material.
They can significantly reduce the life of the components, and in most cases they cannot withstand loads that match the original specification of the metal strength.
When the materials are not processed, they are formeduniformly. The non-
Uniformity treatment creates stress in the form of compression and stretching throughout the material, which is balanced.
When the crack begins to expand in the material on the surface, this is due to the failure of the surface tension to yield strength.
Many materials and metals fail due to this phenomenon, because it is almost impossible to produce metal parts without causing a certain degree of residual stress in the material.
They are not only very harmful, but also very difficult to detect.
Residual stress measurement techniques: Residual stresses are difficult to measure because they are stresses already present in the material without applying any external load.
There are various ways to measure from the hole-
The neutron diffraction method is used to measure the borehole with a variable band to eliminate stress.
The development of finite element analysis: the development of finite element analysis models that attempt to predict the process began in Rosenthal\'s 1940 (Ref. 1)
With the emergence of powerful computers and general finite element software, butit is growing rapidly (Ref: 2-10). S. W. Wen (Ref. 2)
Submerged arc welding of steel wire (SAW)
Machining using the universal finite element software package ansys.
Roelens uses a commercial package (Ref. 11)
For a few more
Passsee welding process, where the FE model developed was validated in five cases based on experimental measurements of thermal history, phase distribution, and residual stress. P.
Tekriwal et al (Ref. 8)
The finite element program and some user subroutines are used to obtain numerical results.
The data generated in this study can be used to determine heating and cooling rates, weld shape, and heat-affected zones (HAZ). L. Fu. etal. (Ref. 9)
The finite element method is used to analyze the coupled thermal mechanical problems in the process of friction welding.
M. Use the heat transfer and parameter design function of the finite element program ANSYS. R. Frewin et al (Ref. 10)
Calculate the temperature distribution of laser welding and the dimensions of the melting and heat-affected zones.
In the above research work, for some difficult finite element models, double elliptical thermal distribution or Gaussian thermal distribution are used as thermal loads.
This paper simulates the discrete growth of the element along the discrete time step of the weld, and the growth rate of the element depends on the welding speed.
Temperature load (
Temperature of filling metal droplets)
The node that is applied to the element at each time step.
The results of the simulation were evaluated based on the comparison of temperature-temperature
Time Map, angular deformation and residual stress were observed through experiments.
Electric Welding process of Gas Metal: electric welding of Gas Metal (GMAW)
During the process, the continuous supply of consumables electrodes is maintained through the center of the welding nozzle.
An arc is generated when the electrode is close to the workpiece, causing the electrode tip to melt and add V-
Groove of two plates.
Continuous supply of protected gases (CO2)
It is also maintained by the ring around the feed line inside the nozzle to protect the weld from air pollution.
Mathematical description of the model: Finite element analysis of weld heat flow was performed on the components using control equations, boundary conditions and temperature loads.
The appropriate equation for transient heat transfer that does not produce any internal heat in the Descartes coordinates is as follows [[
Partial derivative. sup. 2]T/[
Partial derivative[x. sup. 2]+[[
Partial derivative. sup. 2]T/[
Partial derivative[y. sup. 2]+ [[
Partial derivative]. sup. 2]T/[z. sup. 2]= l[C. sub. p]/K([
Partial derivative]T/[
Partial derivativet)(1)
Where x, y, z = Descartes Association
The coordinate system connected to the welding plate.
K = thermal conductivity of materials (w [m. sup. -1][k. sup. -1])[C. sup. p]
= Specific heat capacity (J [Kg. sup. -1][K. sup. -1])
L = material density (kg [m. sup. -3])t = time (sec)
The initial condition is T (x, y, z, 0)= [T. sub. 0](2)
The essential boundary condition is [K. sub. n][[
Partial derivative/[
Partial derivativen]-q + h(T -[T. sub. a])+ [sigma][epsilon]([T. sup. 4]-[T. sup. 4]/[alpha])= 0 (3)where [K. sub. n]
= Thermal conductivity perpendicular to the surface (W[m. sup. -1][K. sup. -1])
Q = specified heat flow (w [m. sup. -2])
H = convection co-efficient (w [m. sup. -2][k. sup. -1])T[alpha]
= Ambient temperature (K)
Weld deposition temperature is found from the heat balance equation (Ref. 12)
In the finite element model, the same is true for temperature loads. Q/V= C [sub. 3][A. sub. w]([T. sub. d]-T[alpha])(4)
Q = net heat supplied to the workpiece (watts)
V = welding speed (m [sec. sup. -1])[A. sub. w]
= Welding area ([m. sub. 2])[T. sub. d]
= Deposition temperature ([sup. 0]K)
Assuming that the weld is deposited instantly, the weld metal remains cooled when the heat is allocated to the entire structure until the ambient temperature is returned.
The finite element equation of the above-mentioned problem is obtained by using the Galician formula.
Finite element modeling procedure: Geometric model: 3D model of actual Welded sample with dimensions of 250x100x25mm-2 Nos. with [60. sup. 0]-
The \"V\" slot between them fills the weld metal (Fig. 4)
Created using entity modeling techniques.
A complete finite element model is given in Figure 1. 5.
Entity modeling is relatively less time consuming compared to the direct generation method.
In solid modeling, the model is created using a fully developed geometry of lines, area, and volume.
Mesh Generation: selecting the right mesh is critical for the accuracy and economics of the finite element results.
When browsing the literature available in the ANSYS component module (Ref. 13)
Discover Iso-
Parameter brick (Solid 70)
Since heat flow, heat flow and temperature can be used as inputs, elements are suitable for analysis.
This element can also be used for coupling-fieldanalysis.
It can be noted here that the problem with MIG welding is the grid (
Or solve the domain, mathematically speaking)
Due to the addition of the filled metal, it continues to grow over time until the welding is completed.
Ideally, in order to obtain accurate results, an analysis of the infinite length of time should be performed, followed by a new element or element (
It will be very small in size)
Before performing an analysis for another infinitely small period of time, the filled metal should be added to the grid.
This alternate process of analyzing and redefining the mesh, along with the new boundary conditions, will continue until the entire weld is covered.
However, it is not possible from a practical point of view. We have to choose an approximate solution that uses the same scheme to alternately analyze and redefine the mesh at a level of limited time and limited size of the filling material.
In this investigation, the length of the weld (250 mm)
Divided into 25 parts and 25 times
Complete the step of passing once.
Similarly, for all four channels, a limited filled metal element with a total of 100 time steps has been created.
Welding speed is 1.
7mm/second, the length of the element is 10mm, and the weld metal deposition time of one element is calculated as 5. 88 seconds. Fig.
5 shows the first step of the first step analysis, of which 5.
88 Welding times were completed.
6 shows the 14-step grid for the fourth analysis.
It is important to note that the volume of the additional elements of each step and their dimensions in the welding direction are consistent with the rate of deposition of the filled metal.
The next important requirement of the grid is fine
Dimension elements near the center line of the weld.
The temperature distribution is less sensitive to the size of components far away from the welding center, and in order to reduce the cost of analysis, their dimensions increase as the elements stay away from the high heat input area.
This size control network is refined (Ref. 13).
The author tried a variety of different refinement ratios, and finally recommended the refinement ratio of the welding area to 10.
In order to obtain the global temperature history generated during the welding process, nonlinear transient thermal analysis was performed.
Mechanical and metallurgical properties of weld metal (WM), basemetal (BM)
Heat affected area (HAZ)
All temperature and temperature
TIME History is relevant.
Due to the lack of material performance information of WM and HAZ, the thermal and mechanical properties of WM and HAZ are considered to be the same as the analysis of BMin.
Consider the relevant thermal properties of the material.
All surfaces of the plate have natural convection heat transfer.
But due to the flow of the protected gas, the area below the torch nozzle experienced forced convection.
Based on the previous model (Ref. 8), h=10 w/[m. sup. 2]-[sup. 0]
K for all surfaces not affected by shielding gas, the following empirical relationship is used for the partial top surface under the nozzle of the welding gun: h = 13 [Re. sup. 0. 5][Pr. sup. 0. 33](K [Co. sub. 2])/ NPD (5)where [R. sub. e]
= Renault number [P. sub. r]
= Prandtl number [K. sub. Co2]
= Heat conductivity]Co. sub. 2]gas (W [m. sup. -1][K. sup. -1])
Nozzle = distance from Nozzle to plate (m)
Although the value of this temperature is relevant, according to the initial calculation of the Reynolds number and the Prandtl number, each point under the nozzle uses a constant value of h.
Calculate the radiation heat loss of all surfaces with equation q = [epsilon][sigma]([T. sup. 4]-[T. sub. [alpha]. sup. 4])(6)where [epsilon]= emissivity (0. 08)
Weld metal elements are generated as discussed in the 1480 [mesh generation and filling drop temperature load]degrees]c (Ref. 8, 14)
Applied to the node.
As shown in the figure, the Load step file was created. 7 and solved. Temperature-
TIME History map from time-
After the history of the four nodes (P, Q, R,S)
As shown in the figure.
Figure 4 shows8.
Calculation scheme: a calculation scheme using ANSYS software.
In turn, coupling field analysis is performed to determine the double stress and angular deformation discussed in Figure 1 of the calculation scheme7.
Node temperatures in transient thermal analysis are used as \"physical strength\" in sequential thermal stress analysis \".
In the material model, the temperature-related properties and boundary conditions of the same-sex materials are defined as inputs and solved.
Export the simulation results using the general post-processing program and in the figure13 (
Corner distortion diagramand in fig. 15(
Residual Stress Map.
Experimental Verification: The temperature time history is obtained by conducting experiments with the following settings to verify the finite element model.
EVO500 automatic MIG welding machine (
Welding Industry in Malaysiawas used. AWS ER 70S-6 (BW-2)
Copper Baotou steel wire 1.
The electrode in the form of a coil with a diameter of 2mm is welded.
Structural steel plates of size 300x150x25mm are welded together four times.
The cross section of the welter shows the edge preparation of the plate, and the weld sequence laid on the connecting surface during the four passes is shown in the figure3.
In order to achieve accurate welding speed, the servo motor drives the manipulator to carry out the plate movement on the fixed torch.
Temperature Measurement-
TIME History, angular deformation, and residual stress were completed using the following procedure. Temperature-
TIME History: K-
Transient temperatures at P, Q, R, and S positions are measured using type thermocouple.
The size details of the plate used in the experiment and the position of the thermocouple are shown in the figure4.
Use the data acquisition system to record the temperature changes during the experiment (DAS)
The pass starts at point A and ends at point B (Fig 5). Temperature-
The time history recorded using DAS is shown in the figure10.
Angular distortion: With the help of the height master, angle distortion is measured using the principle of a sine rod.
Figure 1 shows a photo of the angle distribution amplitude of the welded plate. 14.
Residual stress: Cross
Sectional residual stress mapping technology (Ref. 15)
Used to measure residual stress.
This method includes experimental cutting (using wire EDM)
And measure the shape after deformation (usingCMM)
Along the cutting plane.
Then, after applying the appropriate boundary conditions, the opposite side of the profile is parsed in ANSYS software as a displacement load in the model.
This analysis will give the measured stress distribution along the cutting plane.
Figure 1 shows the resulting double response. 15.
Results and discussion 1.
This step is described in this articleby-
A step-by-step process of communication between heat transfer analysis and changing the geometry of the mesh. 2.
Comparison between predicted temperature and measured temperature
The time history of the positions of P, Q, R and S is depicted in the figure. 8 & 9.
As expected, the proposed finite element analysis gives a better \"realistic\" agreement with the experimental data. 3.
A comparison between the analog value of angular distortion and the measured value is shown in the figure
Figures 15 and 16 depict 13 and 14 and the residual stress.
This shows that the simulation can be used to predict the high accuracy of these values. 4.
The comparison of the FEA and the experimental results was carried out using peak temperature, angle deformation and maximum residual stress during each pass at the P position, as shown in Table 1.
The table value shows that the results of the finite element analysis are very consistent with the experimental results. 5.
The thermal history of the material is very important to determine the microstructure.
The structural changes experienced by the material and the strength of the welded joints.
Any suspicious critical area can be analyzed by drawing the thermal history of the area.
Figure 1 shows the thermal history of sufficient points in the heat-affected zone10.
Very high temperatures cannot be measured with simple techniques such as thermocouple.
However, in areas far away from the melting zone, temperature was measured and compared to understand the accuracy of the results of the finite element analysis. 6. Fig.
11 & 12 shows the temperature profile obtained from the fe simulation.
This information is useful for predicting the geometry of fusion and heat-affected zones. 7.
The time history curve derived from the simulation provides us with information about the maximum temperature reached, the soaking time above the recrystalline temperature and the cooling rate history. 8.
As can be seen from the thermal history, the thermal wave follows the welding sequence.
As the distance between the measurement point and the weld center line increases, the peak temperature decreases over time. 9.
As expected, during each pass of the weld, the temperature of the measurement point rises, reaching the maximum and falling.
The point closest to the center line of the pad goes through the highest temperature. 10. In multi-
By welding, the welds are laid along different welds.
Parallel to the center line of the pad, in v-
Groove butt joint between plates.
In our example, pass 1 and pass 2 are laid with lines that coincide with the center line of the pad, and pass 3 is close to the right plate (
Plate for temperature measurement)
Channel 4 is close to the left plate.
Therefore, even if the weld is laid at the same height, the maximum temperature rise measured during the fourth pass is less than the 3rd pass period. 11.
As can be seen from the experimental results, in the cooling stage of any channel, the cooling rate is steep in the initial stage, but not so steep in the later stage. 12.
Welding after pre-welding
Bending the plate to a simulation value results in a finished weld without angular deformation.
This is an experiment.
Conclusion: 1.
By using finite element analysis, metal transfer in MIG welding can be simulated, and corresponding time steps can be added to fill metal. 2.
The temperature load at the node of the element corresponding to the addition of the filled metal also gives a considerable accuracy. pass welding.
In contrast, modeling of temperature loads is much easier than modeling of welding heat sources.
Article information article history: on September 10, 2014, the revised online confirmation received on October 23, 2014 and received on November 27, 2014 on December 1, 2014 was received. The research work is funded by New Delhi AICTE under the Research Promotion Program (RPS).
On 2009, under the heading \"Simulation of residual stress and deformation of structural steel plates in multi-pass GMAWWelding and its mitigation techniques\"
2010 Fileno: 8023/BOR/RID/RPS-93/2009-10.
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Dean of Mechanical and Electrical Engineering, Faculty of Engineering, Coimbatore Avinashi Maha-641654 (2)
President Sree Sakthi Institute of Engineering, Columbia ,(3)
Principal, Engineering Institute, Coimbatore Avinashi Maharaja-
641654 correspondent: T.
Velumani, head of Mechanical and Electrical Engineering, Faculty of Engineering, Coimbatore Avinashi Maharaja-
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