LOAD AND STRESS ANALYSIS DESIGN VERIFICATION OF THE HOIST CAGE FOR FIRE BRIGADE KENNEMERLAND

Transcription

1 LOAD AND STRESS ANALYSIS DESIGN VERIFICATION OF THE HOIST CAGE FOR FIRE BRIGADE KENNEMERLAND Authors: T.A. de Jong Document number: VIS_0101 Issue number: 1.00 Issue date:

2 Contents 1 Introduction Fundamentals for the Analysis Co-Ordinate System Load Cases Analysis Method Acceptance Criteria Analysis Hoist Cage Finite Element Model Hoist Cage Analysis Results Hoist Cage Conclusion Visser Leeuwarden 2

3 1 Introduction This document presents the agreed load and stress analysis that has been done to verify the design of the Hoist Cage for Fire Brigade Kennemerland. The following describes first the fundamentals for the analysis of the system and the specified load case for the design verification. After that the actual load and stress analysis for the Hoist Cage is described. Visser Leeuwarden 3

4 2 Fundamentals for the Analysis This section describes the fundamentals for the analysis done for the Hoist Cage. The following points will be described: (1) the Co-Ordinate System, (2) the Load Cases, (3) the Analysis Method and (4) the Acceptance Criteria. 2.1 Co-Ordinate System During the design and development there is a co-ordinate system defined. The load and stress analysis described in this report makes use of this co-ordinate system and is shown in Figure 1. x y z x-direction y-direction z-direction Figure 1: Co-Ordinate System Hoist Cage System 2.2 Load Cases For the design of the Hoist Cage it is necessary to make a load and stress analysis to prove the structural integrity of the Hoist Cage. For the load and stress analysis of the Hoist Cage the following load case applies, namely: (1) Hoist Cage (Diver Seat) According to the specification of the customer the Hoist Cage (Diver Seat) needs to withstand the following force, namely: 150 kg ( 1.500N) in the y-direction. 2.3 Analysis Method The Fire Brigade Hoist Cage is analysed according to the Finite Element Method. The Finite Element Method is a widely used numerical tool for engineering issues. The tool is today available in every 3D CAD Software Package. The FEM Module that was used for this analysis is Hypermesh. Visser Leeuwarden 4

5 2.4 Acceptance Criteria The load and stress principles state that the permissible stress is calculated as the quotient of the material load limit and a safety factor. For this analysis the assumption is made that all material properties are assumed linear. So, for the acceptance criteria we use the following quotation to calculate the permissible stress, namely: σ permissible = 1 S σ 0,2 σ 0,2 = Yield Stress Material S = Safety Factor The safety factor used for this Finite Element Analysis is 3,0. Advised for welded structural and securing areas. Visser Leeuwarden 5

6 3 Analysis Hoist Cage This chapter describes the actual results of the load and stress analysis that was done for the Hoist Cage. First the FE model for the analysis will be explained, i.e. base structure, analysis assumptions, boundary conditions/loads and the material properties. After that the actual load and stress analysis results will be described. 3.1 Finite Element Model Hoist Cage Base structure The base structure of the Hoist Cage is made of an aluminium frame structure. This aluminium frame structure is finished with an aluminium sheet metal plate which gives the frame structure the diver seat functionality. To prove the structural strength of the Hoist Cage, only the aluminium frame structure with the lifting eye bolts is analysed. Figure 2 shows this base structure. Figure 2: Base Frame Structure Hoist Cage Analysis Assumptions For the Finite Element Analysis of the Base Structure the following assumptions are made, namely: The structure ends are welded to each other, All the material properties are assumed to be linear, Yield Strength for respective materials is considered for the acceptance criteria. Boundary Conditions/Loads Figure 3 shows the applied boundary conditions for the Finite Element Analysis of the Hoist Cage. Though, simplifications were made to the Finite Element Model. Visser Leeuwarden 6

7 Lifting Eye Bolts are made as boundary conditions for the FE Analysis Figure 3: Boundary conditions Base Structure Hoist Cage Analysis Figure 4 shows how the load is applied in the FE Model according to the load case described in section 2.2 of this analysis report. 150 kg gravity load Hoist Cage y-direction Figure 4: Load assumption Hoist Cage Analysis Material properties Table 1 shows the material properties of the base aluminium frame structure of the Hoist Cage and the lifting eye bolts that are used for the Finite Element Analysis. Yield Strength (MPa) Material Properties E-Modules Density No. Part Name Material (MPa) (kg/m 3 ) 1 Frame Aluminium AW-6060 T ,33 2 Eye Bolt Stainless Steel A ,30 Table 1: Mechanical Properties Materials Hoist Cage Poisson s Ratio Visser Leeuwarden 7

8 3.2 Analysis Results Hoist Cage Below the results of the Finite Element Analysis are described for Hoist Cage for Fire Brigade Kennemerland. The results are described for displacements and von Mises Stresses for the defined load case. Displacement The displacement results for the load direction of Hoist Cage is shown in Figure 5. The maximum displacement for a 1.500N load is 18,6 mm. Figure 5: Displacement Result FE Analysis Hoist Cage Von Mises Stress The von Mises Stress for the 1.500N load case is summarized in Table 2. Also shown in Figure 6 is the von Mises Stress plot for the Hoist Cage analysis. Yield Strength No. Part Name Material (MPa) Maximum von Mises Stress (MPa) y-direction 1 Frame Aluminum AW-6060 T ,1 2 Eye Bolt Stainless Steel A ,9 Table 2: Summary Result von Mises Stress FE Analysis Handgrip Visser Leeuwarden 8

9 z-direction frame structure Figure 6: von Mises Stress FE Analysis Hoist Cage z-direction eye bolt Visser Leeuwarden 9

10 4 Conclusion For the load and stress analysis of the mounting points of the handgrips and the driver seat there is an acceptance criteria defined in section 2.4 of this analysis report. The acceptance criteria are the following for the used materials, namely: Basic Frame Structure σ permissible = 1 S σ 0,2 = = 50,0 MPa 3 σ 0,2 = Yield Stress Material = 150 MPa (Material: Aluminium AW6060 T66) S = Safety Factor = 3 Lifting Eye Bolt σ permissible = 1 S σ 0,2 = = 150,0 MPa 3 σ 0,2 = Yield Stress Material = 450 MPa (Material: Stainless Steel A2) S = Safety Factor = 3 The obtained results of the FE Analysis for the Hoist Cage are: Aluminium Frame Structure y-direction = 42,1 MPa (< 50 MPa), Stainless Steel Lifting Eye Bolts y-direction = 59,9 MPa (< 150 MPa). The obtained von Mises Stress results for the defined load case is less than the permissible stress of the material. Thus, the design of the Hoist Cage for Fire Brigade Kennemerland is predicted to be structural adequate for the lifting of a 150 kg person with a safety factor greater than 3,0. Visser Leeuwarden 10