Modeling and Analysis (Linear Static) on a Scissor Lift

Transcription

1 Modeling and Analysis (Linear Static) on a Scissor Lift Authors P S K Narasimha Murthy 1, D Vinod Prabhakara Rao 2, CH Sai Vinay 3 S Ramesh kumar 4, K Sai Narayan 5 ABSTRACT: Scissors lift platform has a wide range in industries and coercial uses. It is being operated with the help of hydraulic cylinder. This paper is about modelling and analysis (Linear Static) on a scissor lift which is carried out using Solid Works. This designed scissors lift can reach about 7m height placed and fixed on a platform with rigid base. Whenever a load is applied on the top of the platform, every post leg of the lift is subjected to displacement, stress, and strain. In this paper investigations and tabulated results of the displacement, stress and strain values, and the observations with regard to whether there is a change in these parameters on every leg when the lift is at the maximum height and whether these parameters get decreased when the lift height is rendered minimum, are proposed. The outcome of this work is presented in the form of analytical results which are carried out by considering three different materials at different heights, the observations of their behaviour are tabulated. INTRODUCTION Now a day's in the mercantile airline and airport manufacturing industry, ground support equipments play a major role in assisting airline (ground) crews. During the chaotic hours of an airplane arrival, ground crews are busy with the loading and unloading of luggage, catering supplies, water and also refuelling the aircraft fuel tank in order to be prepared for the next scheduled departure. These routine activities must be carefully handled according to standard procedures and protocols of airport system using definite equipment. Apart from this, safety concern is given the prime priority [2]. In order to accomplish the most out of the used areas, scissors lift platform must be given higher and higher loading capability, faster moving velocity and steady starting and stopping motions of the platform. The scissors lift mechanism is the crucial constituent part of scissors lift platform, whose force characteristics will influence the performance of the whole equipment directly. In order to solve this force characteristic the basic model is designed and analysis is done to find the stress deflections on each and every leg of the lift. It is significant for ensuring the security of baggage at high elevation work. P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 754

2 Determination of the main parameters: 1 imum working height of scissor lift 2 Length of a link Area of platform 4 Rated moving velocity upward 5 Rated moving velocity downward 6m/min THE DESIGN AND MODELLING PHASE In this research, Solid Works software was the main CAD solid modelling software used. With its extensive features and powerful modelling tools, it is fully utilized in the CAD modelling stage. The scissors lifts comprises of major components that are being assembled together to form complete scissors lifts for catering the hilift[1]. The post legs and base are two major parts that make up the whole scissors lifts binding together with bearings and centre pins. When modelling the parts, every child parts are saved as individual parts whereby when assembling the parts, all modelled child parts are then retrieved back to be assembled to build the whole scissors lifts as a complete assembly as shows the DEFLECTION CALCULATION The maximum allowable platform edge deflection calculation using the ANSI Standard MH Safety Requirements for Industrial Scissors Lifts (Revision on ANSI MH ) is using Equation (1) is[3] D = D = imum allowable platform edge deflection in () n = Number of vertically stacked pantograph leg sections L = Platform length () W = Platform width () The numbers of vertically stacked post leg sections are the number of scissors located on a single application. For the catering hi-lift used in this research, five vertically stacked post leg section was identified. From Equation (1), the maximum allowable platform edge deflection is calculated as below. D = Figure (1). Scissors lift flat form designed in solid works fig (1) P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 755

3 FINITE ELEMENT ANALYSIS (FEA) SIMULATION To run the FEA simulation using solid works software, it is necessary to generate the Finite Element Model of the scissors lifts structure. This is because, since the early days much progress has been made to finite element method of analysis and today it is viewed as a general procedure of solving discrete problems posed by mathematically defined statements with multiple of numerical experiments that can be carried out[2]. However, all the post legs are used in this analysis because taking into account, the post leg lift and sustain the load exerted on it will be safe during operation. Von-misses stress values of scissors lift at height of 3100() for alloy steel material RESULTS AND DISCUSSION The results were calculated for three different materials (alloy steel, aluminium, and stainless values of scissors lift at height of steel) at three different platform heights (at 3100() for alloy steel material- 5700, 3100, 2000 ). These three different materials and platform heights are The below tabulated values are calculated for the analysed and results are shown in the tabular applied load of 1000 Newton and 2000 Newton column. force on the lift platform.table-1 and table-2 shows the stress, displacement, strain maximum and minimum values of the scissors lift for alloy steel material. table-2 shows the values for aluminium and table-3 shoes the values for stainless steel for two different loads. From the below tabulated values it is found that at 1000N, when the lift is at maximum height then the stress concentration and deflection is more for values of scissors lift at height of aluminium least for alloy steel. At 20000N, it is 3100() for alloy steel material. more for stainless steel. The maximum deflection for aluminium platform at maximum height(5700 P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 756

4 ) for 1000N force is 6.214, from equation(1) it is found that the maximum deflection can be up to 70 so this model is sustainable at this load. As the lift height is decreasing the stress and strain and displacements are also decreasing resulting that at minimum height the model is more sustainable. Again same analysis at that same height and materials where conducted by changing the load parameter in order to see the changes in those parameters, as shown in the below tabular columns and graphs. Alloy steels.(table-1) at 1000N Sl.no Height e e e e ,259, e e e e ,321, e e e e ,590, Aluminium.(table-2) 1000N Sl. no Height e e e e ,149, e e e e ,300, e e e e ,620, Stainless Steel.(table-3) 1000N Sl. no Height e e e e ,259, e e e e ,321, e e e e ,590, Alloy Steels.(table-4) at 20000N Sl. no Height e e e e ,456,368 3, e e e e ,012, , e e e e ,505, P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 757

5 Aluminium.(table-5) 20000N Sl. no Height e e e e ,805, , e e e e ,586, , e e e e ,324, ,865.4 Stainless Steel.(table-6) 20000N Sl.no Height e e e e ,456, , e e e e ,012, , e e e e ,756, ,763.3 at 1000N at 20000N 1.40E E E E E E E E E E E E E E at 1000N at 20000N 4.00E E E E E E E E m 3100 m 2000 m 6.00E E E E E E P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 758

6 at 1000N at 20000N 50,000, ,000,000,000 40,000, ,000,000 30,000, ,000,000 20,000, ,000,000 10,000, ,000, N 20000N CONCLUSION (1) Effect of load on scissors lift through performing exact finite element analyses of the lift with different heights and materials are calculated. In order to find out the maximum deflection mathematical prograing method is used. At three different positions stress, strain and displacements are calculated. (2)When the lift is at the maximum height then for a given load the stress, strain and deflection is higher compared to the minimum height of the lift. All these parameters are proportional to the lift height. (3) When the load is N on the lift it reaches to its yield strength within the limits of the maximum stress being acted upon. The lift cannot sustain this load. The deflection is also maximum at this load thus the lift fails at this condition. REFERENCES 1. Tian Hongyu, Design and Simulation Based on Pro/E for a Hydraulic Lift Platform in Scissors Type, in science direct (march 2011), vol 16, pp Helmi Rashid, Design Review of Scissors Lifts Structure for Coercial Aircraft Ground Support Equipment using Finite Element Analysis, in science direct (dec 2012), vol 41, pp James R. Harris, Fall arrest characteristics of a scissor lift, in national safety council (Available from 15 April 2010) vol 41, pp ACKNOWLEDGMENT The authors would like to thank Dr A.Srinath and Ch.Sai Vinay who provided us with the modelling data. P S K Narasimha Murthy et al IJMEIT Volume 2 Issue 9 September 2014 Page 759