IMechE Pakistan, in its recent push towards greater industrial collaboration with the industry, has seen much success in building bridges between the two.
Shell and IMechE Pakistan took the first step towards establishing a long-term relationship. Stress Analysis of Shell’s Tank Lorries was floated by the company as student’s projects. Two student chapters, Pakistan Navy Engineering College (PNEC-NUST) and School of Mechanical and Manufacturing Engineering of National University of Sciences and Technology (SMME-NUST) worked on the project. The objective was to provide Shell with an improved design of the Tank Lorry with enhanced safety against roll over and reduced cost of operations.
CPEC and Pakistan:
中巴经济的完成Corridor (CPEC) in 2018, Pakistan will experience accelerated economic growth with increased living standards. Transportation will rise exponentially throughout the country and will necessitate regular and more increased supply of fuel to different parts of the country from the oil refineries in the south. Transportation costs will therefore play an important role in the overall profitability, scalability and market share of key players like Shell.
Ladder Frame Chassis
Tank Lorries are used for transporting several thousand liters of fuel between cities. Thechassis frameis an integral part of the lorry as it sustains the bulk of the loading experienced by the lorry and therefore, a structurally sound chassis is crucial for the lorry to perform its functions.
The chassis frame of a lorry functions not only as asupport basefor the entire structure, but is also essentially the component on which the entire loading of the vehicle is projected. The loading includes the weight of the vehicle, including body, tank (with the carried fuel) and components, to be modeled under different static and dynamic conditions for the vehicle. It is hence imperative, that the chassis must be structurally sound enough to withstand not only the static loading, but must also function properly in dynamic conditions, and especially off-road conditions whereroad bumpsare considered.
Finite Element Analysis(FEA) remains a tool of considerable importance for the modeling and analysis of such structures. The chassis frame, isolated from the vehicle, is first modeled in appropriate CAD software. FEA software models the frame structure based on specifiedboundary conditions. Based on the results of the FEA, decisions regarding design changes are easy to undertake to be able to make the best optimum choice available. The deciding factors in this analysis are the stress distribution and the maximum deflection that the structure can withhold. FEA is often used in conjecture with experimental procedures for verification of accuracy of the results.
Three load cases were defined for initial studies from literature review of existing ladder frame chassis. Bending, torsional and bump cases were identified. Under these studies, the stresses on the entire frame were mapped and critical regions located. This was essential as it assisted in improving the designs.
Regions with very low stresses like the running gear assembly were identified to undergo reduction in weight and center of mass. Enhancing the designs provide around a 50kg of weight reduction. However, these were only the initial studies. Further studies on changing the overall cross section can lead to weight reduction of up to 200kg.