Askeri Araçlarda Kullanılan Double Wishbone ve Trailing Arm Tipi Süspansiyon Sistemlerinin Tasarımı ve Dinamik Analizi = Design and Dynamic Analysis of Double Wishbone and Trailing Arm Type Suspension Systems Used in Military Vehicles

Abstract

Askeri araçlarda yaygın olarak kullanılan Double Wishbone ve Trailing Arm tipi süspansiyon sistemlerinin karşılaştırmalı bir analizini bu çalışma ile sunulmaktadır. MATLAB Simulink kullanılarak oluşturulan matematik modellerin davranışı incelenmiş, PTC Creo yazılımı kullanılarak 3 boyutlu olarak modellenen geometriler üzerine belirlenen şartlarda kuvvetler etki ettirilerek sistem ve parça davranışları üzerine analizler ANSYS Workbench yazılımı ile gerçekleştirilmiştir. Her iki sistemin statik ve dinamik kuvvetler altına ve mukavemet davranışları incelenmiştir. Karşılaştırmanın adil olmasını sağlamak adına, her iki sistem için aynı amortisör katsayıları ve araç parametreleri kullanılmıştır. Double Wishbone süspansiyon sistemi, tekerleklerin yanal stabilitesini ve yol tutuş performansına olumlu etki eden bir tasarım olduğu ve özellikle yüksek hızlarda ve düzgün profilli yollarda üstün performans gösterdiği bilinmektedir. Ancak karmaşık tasarımı ve yüksek maliyetli bakım gereksinimi önemli bir dezavantaj yaratmaktadır. Trailing Arm süspansiyon sistemiyse konsept olarak daha basit geometriye sahip olup, özellikle zorlu arazi koşullarında çalışan ağır iş araçlarında etkili bir titreşim izolasyonu sağladığı için tercih edilmektedir. Geometrisi gereği arazi koşullarında yol profilini takip ederken izlediği eliptik bir hareket formu sayesinde, tekerleklerin zeminle temasını optimize eder ve stabiliteyi artırır. Analiz sonuçlarına göre, Trailing Arm sistemi için hazırlanan konsept tasarım, Double Wishbone sistemi için hazırlanan konsept tasarıma kıyasla daha fazla gerilmeye maruz kalmıştır. Ancak ağırlık bakımından tasarımların birbirine yakın olduğu belirlenmiştir. Sonuç olarak, her iki sistemin de kullanım alanına uygun avantajları ve dezavantajları bulunmaktadır. MATLAB Simulink kullanılarak ulaşılan sonuçlar incelenmiştir. Simülasyon sonuçları grafik ile gösterilmiş, belirli bir step değeri için m_c ve m_s için değerleri incelediğimizde m_s değerlerinin birbirine yakın olduğunu ancak m_c değerleri arasında görece yüksek bir fark olduğu görülmektedir. Bu sonuç bir engel üzerinden geçme esnasında araç gövdesine iletilen titreşimin görece daha az olacağına işaret etmektedir. Uygulanan kuvvetler ve elemanlar ve bağlantılar üzerinde bu kuvvetlere karşı gelen gerilmeler incelenmiştir. Sonuçları tablo haline getirerek değerlendirdiğimizde aynı amortisör elemanı ile oluşturulan iki sistemden Trailing Arm tipi sisteme daha fazla yay tepki kuvveti geldiğini ve dolayısıyla kol üzerinde noktasal olarak daha fazla gerilme yığılması oluştuğu görülmektedir. Çalışma, süspansiyon sistemlerinin yük altındaki mukavemet değerlerini değerlendirerek, askeri araçların zorlu operasyonel gereksinimlerine uygun sistem seçimi için yol gösterici olmayı amaçlamaktadır.

This study presents a detailed comparative analysis of Double Wishbone and Trailing Arm suspension systems, which are extensively used in military vehicles. These suspension systems were evaluated through a combination of mathematical modeling, computer simulation, and finite element analysis (FEA). MATLAB Simulink was employed to develop and simulate the mathematical models, while ANSYS Workbench software was used to analyze the structural behaviors under specified loading conditions. The three-dimensional geometries of these systems were designed using PTC Creo, enabling an in-depth investigation of their static and dynamic strength behaviors. To ensure an equitable comparison, identical shock absorber coefficients and vehicle parameters were utilized for both systems. The Double Wishbone suspension system is widely recognized for its ability to enhance lateral stability and handling performance, particularly at high speeds and on smooth road surfaces. However, its complex design and high maintenance costs present significant challenges. On the other hand, the Trailing Arm suspension system, with its simpler geometry, is often preferred for heavy-duty vehicles operating in challenging off-road conditions due to its effective vibration isolation capabilities. Its design enables an elliptical motion, optimizing wheel-ground contact and improving stability on uneven terrain. The results of the analysis revealed that the concept design for the Trailing Arm system experienced higher stress levels compared to the Double Wishbone system under identical conditions. Despite this, both systems were found to be comparable in terms of weight. This indicates that each suspension system has distinct advantages and disadvantages, depending on the intended operational requirements and terrain conditions. To further enhance the applicability of this study, the same auxiliary components, such as hydropneumatic struts, were incorporated into both systems. This commonality facilitates streamlined production and spare parts management. Additionally, a hydropneumatic suspension system was selected as an alternative to conventional springs, as it allows for the adjustment of spring coefficients through varying gas pressure. This feature enables the optimization of stroke length and accommodates geometric constraints, making it particularly suitable for military applications. Hydropneumatic suspension systems, which combine liquid and gas, offer numerous advantages over traditional mechanical spring and shock absorber combinations. These systems provide superior comfort, performance, and adaptability, making them a preferred choice in automotive and industrial applications. Due to the compressive effect of gas pressure on the liquid, hydropneumatic suspensions exhibit softer and nonlinear spring characteristics compared to mechanical springs, thereby reducing the transmission of road impacts to vehicle occupants. A concept design for the Trailing Arm suspension system was developed based on the defined initial conditions. The angular movement inherent in its geometry allowed for the use of the same damping and spring stiffness coefficients as the Double Wishbone system. To maintain compatibility, a gas shock absorber was employed, and the spring stiffness was adjusted to the calculated values. The design also incorporated geometry suitable for double arm configurations and steering mechanisms, recognizing the importance of maneuverability in military vehicles. Simulation results obtained from MATLAB Simulink were analyzed and visualized graphically. These simulations demonstrated that while the sprung mass values remained similar between the systems, significant differences were observed in the unsprung mass values. This disparity suggests that the Trailing Arm system is likely to transmit less vibration to the vehicle body when traversing obstacles, thereby enhancing ride comfort. Stress analyses conducted with ANSYS Workbench showed that the Trailing Arm system experienced higher spring reaction forces and localized stress accumulation compared to the Double Wishbone system when subjected to identical loading conditions. The finite element analysis (FEA) method was employed to model the stress and strain distributions with precision. This approach involves discretizing the geometry into unit elements that form a mesh structure, enabling accurate calculations of stress and strain values for each element. The material properties, such as ductile cast iron, were defined in the software, and boundary conditions were applied to the nodes for the analysis. The results underscored the importance of material selection in managing stress concentrations and improving the durability of suspension components. The connections between components were defined according to their respective movement scenarios. For instance, rotational joints were used between the wishbone arms and the chassis, while spherical joints were defined between the hub and the arms to allow specific rotational movements. Additionally, the preload caused by vehicle weight was incorporated into the calculations to simulate static equilibrium. Static analysis revealed that the hydropneumatic element in the Trailing Arm system experienced 27% higher loads compared to the Double Wishbone system under static conditions. Dynamic analysis further indicated a 41% higher reaction force in the hydropneumatic element of the Trailing Arm system due to its geometric differences. This increase in forces directly correlates with stress accumulation, potentially reducing the service life of components subjected to continuous dynamic loads, such as suspension arms. When comparing the weights of the designed geometries, the difference between the two systems was found to be negligible at the axle level. Given the overall vehicle weight, this difference is unlikely to significantly impact performance. However, the stress concentrations observed in the Trailing Arm system highlight the importance of robust material selection and design optimization to improve its durability under demanding conditions. Overall, the Trailing Arm suspension system demonstrates superior vibration isolation under off-road conditions compared to the Double Wishbone system. This is attributed to its vertical spring-like motion, which minimizes lateral vibrations transmitted to the chassis. However, the Double Wishbone system excels in lateral stability and handling on flat roads, offering a more controlled ride but potentially transmitting higher vibrations on rough terrain. The placement of shock absorbers also plays a critical role in determining suspension performance. In the Trailing Arm system, locating the shock absorber closer to the pivot point reduces the effective spring and damping rates at the wheel due to leverage, resulting in a softer response. Conversely, the Double Wishbone system typically mounts shock absorbers closer to the wheel, providing more direct damping of vertical impacts but slightly reducing vibration isolation. From an operational perspective, the Trailing Arm suspension system is better suited for rough off-road conditions, offering enhanced stability and vibration reduction. In contrast, the Double Wishbone system provides superior control and comfort on smooth surfaces. The choice between these systems should therefore align with the specific operational requirements and terrain conditions of the vehicle. The applied forces and stresses on the suspension elements were analyzed in detail. The finite element method (FEM) was used to subdivide the complex geometry of the suspension components into smaller elements, forming a numerical model. These elements, connected at nodal points, were analyzed to determine their stress, strain, and deformation behaviors under various loading scenarios. This approach allows for the precise evaluation of the suspension system's structural integrity and performance. The results showed that material properties play a crucial role in determining the maximum stress points and the overall durability of the suspension system. Ductile cast iron, known for its high strength and toughness, was found to be a suitable material for both suspension systems. Its ability to withstand high stress concentrations makes it ideal for applications involving dynamic and static loads. Furthermore, the analysis highlighted the significance of preload conditions caused by vehicle weight. For the Double Wishbone system, the static deflection of the suspension components was calculated and incorporated into the simulations as preload values. This step ensures that the suspension system's behavior under real-world operating conditions is accurately represented in the analysis. Dynamic simulations conducted using MATLAB Simulink provided additional insights into the vibration characteristics of both suspension systems. The results indicated that the Trailing Arm system exhibited better vibration isolation under off-road conditions, primarily due to its unique elliptical motion and effective leverage. On the other hand, the Double Wishbone system demonstrated superior performance on smooth roads, with improved lateral stability and reduced body roll. In conclusion, this study provides a comprehensive evaluation of the Double Wishbone and Trailing Arm suspension systems, highlighting their respective strengths and limitations. The findings underscore the importance of selecting the appropriate suspension system based on the operational requirements and terrain conditions of the vehicle. While the Trailing Arm system offers advantages in rough off-road environments, the Double Wishbone system excels in providing a stable and controlled ride on smooth surfaces. By leveraging advanced simulation tools and finite element analysis, this study contributes to the development of more efficient and reliable suspension systems for military vehicles.