Design and development of a heavy-duty truck chassis

Project Overview Our Team undertook the design and development of a heavy-duty truck chassis, engineered to support a gross vehicle weight of up to 27 tons across a 12-meter length. The project spanned the entire design lifecycle, from conceptual design and 3D modeling to finite element analysis (FEA), geometric dimensioning and tolerancing (GD&T), and the creation of detailed manufacturing drawings. The chassis was designed to integrate critical sub-systems, including the engine, Transmission, suspension, and exhaust systems, while meeting stringent performance, safety, and regulatory requirements. Mounting Design for Sub-systems The chassis design incorporated robust mounting systems for various sub-systems, ensuring structural integrity and operational efficiency. Key mounting designs included: • Engine Mount: Engine mounts were designed to isolate vibrations from the chassis, enhancing driver comfort and protecting components from dynamic loads. Typically supporting engines weighing 1000 kg, these mounts utilized rubber isolators to dampen vibrations and were engineered to withstand the engine’s torque and weight. • EGR (Exhaust Gas Recirculation) System Mount: The EGR system mount was designed to endure high temperatures (up to 700°C) and vibrations inherent in exhaust systems. Materials such as stainless steel or heat-resistant alloys were selected to ensure durability. The mount’s design ensured proper alignment with the engine and exhaust pipes, minimizing stress concentrations and maintaining system efficiency. • Additional Sub-systems: Mounts for the Transmission, suspension components (including parabolic and elliptic springs and dampers), fuel tanks, and other systems were strategically placed around the front, middle, and rear wheels/shafts. This symmetrical arrangement optimized weight distribution and enhanced vehicle stability. Each mount was designed to accommodate specific load and environmental conditions, ensuring seamless integration with the chassis. These mounting designs were modelled using advanced CAD software, such as CATIA V5, to ensure precise fitment and compatibility with the overall chassis structure. Finite Element Analysis (FEA) Finite Element Analysis was a critical component of the design process, validating the chassis’s structural integrity under various loading conditions. The following analyses were conducted using industry-standard tools: • Static Analysis: A 12-meter chassis model with a 27-ton load was analysed, revealing a critical bending moment at the rear shaft and a flexural stress. With a yield strength of 345 MPa, the safety factor was 1.22, confirming the design’s adequacy for normal operating conditions. • Buckling Analysis: Buckling analysis identified potential instability at the rear axle, with eigenloads causing local and global buckling. To address this, vertical struts were added between tubular sections, enhancing structural stability. • Modal Analysis: Modal analysis ensured the chassis’s natural frequencies were outside the engine’s operating range (1000-2000 rpm, or 16.5–33.3 Hz) to prevent resonance. The first five natural frequencies were confirmed to be well outside this range, ensuring operational reliability. • Dynamic Analysis: Dynamic simulations assessed the chassis under various conditions: o Self-weight o Normal running (15 tons) o Humps o Curvature (torsion at 50 km/h) These analyses guided iterative design improvements, such as reinforcing critical areas and optimizing cross-sectional shapes (e.g., C, I, Hollow Rectangular) to balance weight and strength. Critical Geometric Dimensioning and Tolerancing (GD&T) Geometric Dimensioning and Tolerancing (GD&T) was integral to ensuring the chassis components could be manufactured and assembled with high precision. Key GD&T features included: • Flatness: Mounting surfaces for sub-systems, such as the engine and suspension, were specified with flatness tolerances of ±0.1 mm to ensure proper alignment and load distribution. • Positional Tolerances: Bolt holes for mounting components were assigned positional tolerances of ±0.2 mm, ensuring accurate fitment during assembly. • Profile Tolerances: Frame rails were designed with profile tolerances to maintain structural integrity and alignment, critical for the chassis’s overall performance. These tolerances were incorporated into the manufacturing drawings, adhering to industry standards to facilitate high-quality production and assembly. Manufacturing Drawings Creation Detailed manufacturing drawings were created using CATIA V5, serving as the blueprint for chassis fabrication. Key aspects included: • Geometric Model: A 3D solid model of the chassis was developed, detailing all components and their dimensions. • Cross-Section Optimization: Various cross-sections (C, I, Hollow Rectangular) were analyzed, with the final design selected based on FEA results to minimize weight while maximizing strength. • Meshing for Analysis: The model was meshed using HyperMesh, comprising 5793 elements and 5932 nodes, ensuring accurate FEA results for stress and deformation. • Material Specifications: High-strength low-alloy (HSLA) steel was chosen for its optimal balance of strength, weight, and cost, with a maximum deformation of 0.74988 mm under a 4-ton load. These drawings provided comprehensive guidance for manufacturers, ensuring the chassis could be produced efficiently and accurately. Key Technical Challenges The design process encountered several technical challenges, which were addressed through innovative engineering solutions: • Stress Management: Under torsion at 50 km/h, stresses reached 392 MPa, exceeding the yield stress of 350 MPa. This was mitigated by reinforcing critical areas and adjusting the chassis geometry to distribute loads more effectively. • Material Selection: Balancing cost, weight, and performance was challenging. HSLA steel was selected as the optimal material. • Vibration and Resonance: Ensuring the chassis’s natural frequencies did not align with the engine’s operating range required careful modal analysis and design adjustments, such as modifying tubular configurations. • Manufacturing Feasibility: The design had to be compatible with available manufacturing processes with Client’s preferred supplier, including welding and assembly. This required close collaboration with production teams to ensure feasibility without compromising performance. Company’s Contribution Our Team played a pivotal role in the project, delivering the following contributions: • End-to-End Design Leadership: Managed the entire design process, from concept development to final manufacturing drawings. • Advanced Analysis: Conducted comprehensive FEA (static, modal, buckling, and dynamic) to validate the chassis under diverse conditions, ensuring reliability and safety. • Innovative Mounting Solutions: Developed specialized mounts for sub-systems like the engine and EGR system, enhancing durability and performance. • Cross-Functional Collaboration: Worked closely with engineering, manufacturing, and regulatory teams to integrate the chassis design with other vehicle systems and ensure compliance. • Regulatory Compliance: Ensured the design met all relevant standards, facilitating market approval and customer satisfaction. Applicable Regulatory Standards The chassis design adhered to several regulatory standards to ensure safety, environmental compliance, and market readiness: • FMVSS (Federal Motor Vehicle Safety Standards): Compliance with FMVSS ensured the chassis met safety requirements for commercial vehicles, including load-bearing capacity and crashworthiness. • EPA (Environmental Protection Agency) Standards: Adherence to EPA regulations influenced the EGR system mount design, ensuring effective emissions control. • SAE (Society of Automotive Engineers) Standards: Industry guidelines from SAE were followed for chassis design, testing, and performance, ensuring reliability and durability. • Local Authority Regulations: Considerations for maximum load per wheel, front/rear free spans, total length, and traction per shaft were incorporated, as these are often regulated by local authorities. Conclusion This case study highlights our company’s expertise in designing a robust truck chassis from concept to production. By addressing critical aspects such as mounting design, FEA, GD&T, manufacturing drawings, and regulatory compliance, we delivered a high-quality product that meets performance, safety, and market requirements. The project underscores our ability to overcome complex technical challenges, leverage advanced engineering tools, and collaborate effectively to produce a reliable foundation for heavy-duty truck applications.