1. Introduction
The automobile chassis or frame is one of the base elements that provides the necessary strength and solidity to the motor vehicle in various loading and unloading conditions. The design structure and used material of the chassis structure significantly affects its strength and weight [
1]. Automotive chassis or frames are basically manufactured from steel and holds the entire body and engine part of an automotive vehicle [
2]. Chassis provides the initial required strength needed for supporting vehicular components [
3]. The continuous demand for the improvement in design analysis of heavy motor vehicle chassis frames, considering a decrease in ‘weight’, has been the major challenge for the automotive industry, where optimization techniques can be used in efficient design improvement of chassis to meet industry requirements. To accomplish a significant weight decrease and quality extension, these optimization approaches should be further stretched out to decide the optimal design [
3]. It has been demonstrated that the optimization techniques are very encouraging methods for systematic design development in engineering, especially the automotive sector, which shows the real-life simulation before the actual manufacturing of the component or assembly [
4].
The studies conducted by Chiandussi et al. [
5], Pedersen [
6] and Duddeck [
7] are very fascinating in this direction, in which they addressed the optimization of suspensions, layout profiles and body parts. Ketan Gajanan Nalawade et al. [
8] conducted structural analysis on TATA 407 truck chassis using ANSYS FEA software. The new material used for analysis was E-glass and compared with structural steel. The findings showed that a 60–68% weight reduction is possibly through the use of E-glass; the deformation is also within acceptable limits, but the stress generated is higher than steel. Abhishek Sharma et al. [
9] have conducted a static structural analysis on TATA LPS 2515 EX chassis using ANSYS FEA software. The material used for the analysis were AISI 4130 alloy steel and ASTM A710 STEEL GRADE A (CLASS III) and the cross sections analysed for the chassis were B type, C type and I type. The findings showed that the best material for this application is AISI 4130 steel, which is lighter than other materials. The box channel shape cross section exhibits higher durability and lower deformation; therefore, it is best suited for the chassis design of heavy trucks. Abhishek Singh et al. [
10] have conducted FEA analysis on TATA LP 912 chassis using Altair Hyper work software. The material used for analysis was alloy steel and the cross section used was C type, I type, a rectangular box (solid) and a rectangular box (hollow). The findings showed that the rectangular (solid) section is more robust than other type of cross sections. Anurag Singh et al. [
11] have designed a truck chassis using the CAD software CREO and had performed static analysis using ANSYS software in order to investigate the various stresses acting on it and their resultant deformation. Since the truck chassis has to carry a large amount of load, its design should be such that it can withstand all the forces acting on it. Here in this paper, after modelling the 3D design of the chassis using CREO, the design was imported into the ANSYS workbench in IGES file format. Selecting HLSA steel as the material used for the chassis, the static analysis was performed to observe the maximum principal stress, maximum shear stress and corresponding Von Mises stress. The maximum deformation observed was 0.0084 mm and the design was found to be safe.
Nikhil Tidke [
12] conducted an FEA analysis on Eicher E2 vehicle chassis using ANSYS FEA software. The materials used for the analysis were ASTM A710 steel, ASTM A302 steel and metal alloy 6063-T6, and model was subjected to constant loading. The cross sections used for the analysis were C type and rectangular box. The structural analysis has shown that “Rectangular box section have additional strength than C cross section and the Rectangular box sections have low deflection, lowest stress, and deformation” [
12]. Mostly, the chassis cross-members placed at different locations are made of steel [
13,
14]. Dabade et al. [
15] have presented a review on the application of the Taguchi method in optimizing the design of various automobile components. The author has emphasized the usage of the Taguchi method in experimental designing and development of robust products. Hsua et al. [
16] has worked on optimization of the body cage using a FEM-based Taguchi method. The effect of various factors, such as thickness and other dimensions, on the strength and safety factor was evaluated. The individual contribution of each optimization variable was also presented by the researcher. Aluminium alloy and alloy steel are the ideal materials for a rigid and lightweight structure, such as automotive chassis, but they are not economically feasible [
17].
Although steel is the primary choice of the manufacturers because of its low cost, considerable relative strength and ductileness, there are a number of composite materials [
18] that offer a proper strength and modulus better than any conventional metallic metals [
2,
19,
20,
21].
A lot of new materials have been developed which have the same load carrying capacity as those of the existing materials yet weigh significantly less than their current opponents [
22]. Composite materials [
18], with their distinctive combination of high stiffness and low CTE, offer the essential physical attributes towards lightweight and durable structures [
18]. Generous advancement in the improvement of light metal matrix composites has been accomplished in the last few years, with the goal that they could be brought into the main applications. Particularly in the automotive business, MMCs have been utilized in fibre-reinforced pistons and Al crank cases with fortified chamber surfaces [
23].
These materials have a good number of properties, including a high Young’s modulus, high compression and tensile strength, mechanical compatibility, high compression and tensile strength and economic efficiency, etc. [
23]. Such a combination of properties of composite materials can be valuable in the automotive quality and manufacturing sector where vibration, toughness and increasing fuel prices are serious concerns, along with other technical requirements [
24].
The principal objective of this paper is to reduce the weight of chassis by considering the lightweight “Unidirectional Metal-Matrix Composite Aluminium P100/6061 Al MMC” [
18] and “Discontinuously Reinforced Aluminum-Matrix Composites Aluminium Graphite Al GA 7-230” [
18,
25] materials along with optimizing the design of chassis using the Box–Behnken design scheme of the response surface method. The key considerations of a structure design are density and Young´s modulus, moment of inertia, mass and torsional stiffness [
17].
The findings presented here, are part of a detailed research study and the present research work is different from the literature with respect to the modelling, design and optimization analysis of heavy vehicle chassis for numerous effects of stress distribution with different materials. The appropriate data of an existing heavy duty truck chassis of TATA company’s, model number 1612 (St52 E = 2.10 × 10
5 N/mm
2), as a simply supported beam with overhang ladder frame, were taken for design and analysis, with the side bar of the chassis made from ‘C’ Channels having dimensions of 116 mm × 25 mm × 5 mm [
26]. Total load acting on the chassis is 257022 N [
26]. The CAD modelling and FE simulation is conducted using ANSYS software. A detailed static structural analysis is conducted in heavy motor vehicle chassis enabled to determine critical regions of high stresses and deformation. The suggestions are produced among the currently used conventional steel and suggested metal matrix composite(s). The variable selected for optimization is cross member width and the scheme of optimization is the Box–Behnken design [
27]. In the automotive industry, presently, no work has been done in improving the design of existing chassis using the advanced optimization techniques used in this work.
4. Conclusions
The static structural analysis conducted for heavy motor vehicle chassis enabled us to determine the critical regions of high stresses and deformation. The new optimized design of a chassis structure is presented using the Box–Behnken optimization scheme. The response surface plots of the different variables were generated, which enabled to determine the range of values (of variables) for which the equivalent stress deformation and mass is minimum or maximum. The weight of the chassis is affected by the width of the cross members, which was established by sensitivity plots generated using the Box–Behnken design optimization scheme.
MMCs can be a viable option for automotive components and the applicability of MMCs in a chassis structure was investigated in the current research using numerical techniques. The use of MMCs for chassis structures aided to reduce the weight of the chassis without compromising on its strength.
The most significant findings of the optimization results in case of the P100/6061 Al MMC is that cross member 2’s width has the maximum effect on equivalent stress and cross member 3’s width has the minimum effect on equivalent stress. The weight of the chassis can be reduced by nearly 68% using the aluminium P100/6061 Al MMC material. In turn, cross member 3’s width has the maximum effect on equivalent stress and cross member 1’s width has the minimum effect on equivalent stress, resulting in the weight to be reduced by nearly 70% using the aluminium Al GA 7-230 MMC. In the automotive industry, presently, no work has been done on improving the design of existing chassis using the advanced optimization techniques used in this work.
Further research can be conducted on chassis using other new materials and optimization techniques, which could provide us with better information on the effect of other design variables on equivalent stress generated on chassis under heavy loading conditions.