Various products such as refrigerators, mobile phones, televisions, washing machines, remote controls, telecommunication and military equipment, etc. are subjected to drop tests to assess their fragility and impact tolerance. It is difficult and expensive to understand the effect of various parameters on the product performance during the test. Finite element simulations using LS-DYNA® effectively help to understand these effects.
In this paper we have improved the stiffness of a rear panel of a washing machine by integrating new plastic parts called spacers and metal reinforcement plates. To get the best results we have considered the pre-stresses as well.
In this modern day to day life, people are looking for things to get simpler.any home appliance or any object after impacting the load it will get deformation. We have to check whether the deformations are in acceptable range or not, by using simulations. If a load is acted on washing machine, we will see deformations, to avoid these deformations, we do analysis. While transporting, the oscillating drum gets vibrate and deformations take place to avoid these deformations, we use plastic components named spacers.The main components and dimensional figure is shown in fig:1 and fig:2.
II. PROBLEM DEFINITION AND METHODOLOGY
A. Problem definition
To improve the stiffness for the rear panel of a washing machine by incorporating spacers and reinforcement plates in the design. To get the best results we have considered the pre stresses as well.
Approach: Crash or failure simulation is nonlinear explicit in nature. In other words, it is time dependent. The deformations can be calculated at any instant of time. The following step by step procedure is to be followed to accomplish crash or failure analysis of the washing machine rear panel shown in fig:3
The washing machine model was analysed for energy absorption characteristics in the following three steps:
Pre-Processing using Hyper mesh
Solution using Ls-Dyna
Post processing using Ls-PrePost
III. DESIGN AND ANALYSIS
The washing machine (585*595*850) mm or (23.03*23.4*33.4) inches is designed by using Auto CAD software as per the dimensions shown in table. The spacers are incorporated in designing the washing machine to withstand the drag forces when the washing machine is in transportation. The fig: 4 depicts, the rear view
Table: 1 Dimensions Of The Washing Machine
DIMENSIONAL VALUES (MM)
The different components used are like the rigid base, spacers and reinforcement plates. The components spacers help us to withstand drag forces while it was in transportation and the reinforcement plates helps in providing the extra strength to the washing machine both during the transportation as well in the washing machine usage. The rigid base and spacers figure is shown below.in fig:5 and fig:6
C. Pre Stress Analysis
During Assembly or Mounting process there will be some stresses developed. Those stresses will be negligible when compared to stresses after impact. But to get accurate results we have to consider those stresses as well. These are called as pre-stresses
IV. RESULTS AND ANALYSIS
The washing machine model is considered for analysing the energy absorption characteristics. An input height parameter of 30cm was given as input, and a runtime 50ms is given and the results are interpreted as follows.
A. Energy Balance Curves
According to the Law of Conservation of energy, Energy can neither be created nor be destroyed, but it can be converted from one form of energy to other form. Applying the same principle to washing machine analysis, the amount of kinetic energy lost during impact must be converted to other forms of energy such as internal energy, sliding energy and hour glass energy. It is also noted that, there may be negligible errors in calculating energy ratio because all the processes in this universe are irreversible and some losses are always included which deviates energy ratio slightly from one.
???????B. Global Stat Energy
From the Fig. 7 it is clear that the absorption of Internal Energy (IE), Sliding Energy (SE), spring and damper energy and Hour glass Energy (HE) for washing machine analysis is 82.5%, 7.2%, 10.15%, 0% respectively. The summation of all the energies leads to 99.85% which indicates the energy ratio is approximately one with an error of 0.15%. At 0 Ms, the percentage of internal energy. It shows that the kinetic energy lost during impact is appeared in the form of IE, SE and HE.
We are very grateful to our department faculty members and also to our principal, who helped us in completing this paper successfully.
As we have used reinforcement plates and spacers, we have reduced stresses and permanent deformations of a rear panel in a washing machine during drop test. Earlier when we used only bolts without the reinforcement plates and spacers the value of permanent deformations was around 9.000E-02. Now with the inclusion of the reinforcement plates and spacers in the washing machine the value of permanent deformations was around 3.000E-02. Since the permanent deformation values got reduced after using the reinforcement plates and spacers, as a result the stiffness of the rear panel also increases.
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