后悬架疲劳试验失效分析

某车型的后悬架在做完单侧垂直载荷耐久性试验后，在桥架与支架的焊接处出现开裂。对失效件进行了化学分析、金相检验、扫描电镜观察和力学性能测定，并与未失效件作了对比。结果表明，在桥架和支架的焊接热影响区发生了组织变化，导致该区域硬度下降，因此在做完疲劳试验后即出现开裂。     

Failure Analysis of Primary Suspension Spring of Rail Road Vehicle

WAG-9-type electric rail vehicle, of Indian Railways’ fleet used for goods train hauling and maintained at Ajani, Nagpur Electric Loco Shed of central railway, has a history of frequent failure of middle axle primary inner suspension spring. The study of failures revealed that this specific component fails at a very high rate. The failure investigation starts the experimental spectroscopy analysis to find chemical composition for different failed specimens of springs, and it is observed that all parameters are within the recommended range. Also the stiffness of primary middle axle and end axle suspension springs has been checked on spring testing machine to measure deflection of spring, and it is as per recommended values. Further static stress analysis is carried out using analytical and finite element analysis for various phases of operation of rail vehicle like straight track, curved track and also for tractive effort. The static stress analysis has not revealed the cause of failure, and hence the dynamic analysis is performed. For dynamic analysis, dynamic model of suspension system is considered and analyzed using analytical method, finite element method and using MATLAB Simulink model. The vibration response of actual suspension system is also measured using FFT analyzer. It has been seen that the frequency of excitation and the natural frequency of the system are very close to each other which has resulted into suspension vibration amplitude of 6–8 mm. Fatigue analysis is carried out using finite element method to investigate the effect of dynamic loading on the failures of suspension spring. This analysis revealed that the middle axle inner suspension spring has finite life and due to which spring failure occurs earlier.     

扭力梁式后悬架模态与疲劳实验研究

扭力梁式后悬架是汽车行驶系统中重要的承重构件,在不同的行驶工况下,会受到不同幅值和不同频率的激励。在激励频率和扭力梁式后悬架固有频率接近或相同时,会产生共振,进而发生疲劳断裂。通过对扭力梁式后悬架进行模态实验,获得该结构的固有频率和模态振型。对同一型号的扭力梁式后悬架进行弯曲、扭转疲劳实验,得到其疲劳破坏的具体形式。对产生破坏的扭力梁式后悬架进行模态实验,对未损坏和损坏的扭力梁式后悬架各自的固有频率和模态振型进行对比分析,发现产生疲劳破损的扭力梁式后悬架在某一阶频率下的模态振型有较大变化,结构的固有频率值和固有频率分布的变化并不很大。     

汽车俯仰与跳动复合运动的分析

为了减少俯仰运动,后悬架应该比前悬架有较高的弹簧刚度。研究表明:汽车前后频率和阻尼比用俯仰和跳动总功率表示;跳动总功率在最小俯仰总功率的最佳频率比时,几乎达到最大值,较高的后频和较高的阻尼比减少了俯仰运动。     

单气室油气弹簧的优化设计研究

摘要：讨论了某军用越野车单气室油气弹簧的优化设计。首先建立油气弹簧的单缸数学模型,进而建立油气悬架系统1/2车辆模型的数学模型。然后根据越野车的特点,以车辆的平顺性和轮胎的接地性作为目标函数,以前、后油气弹簧的主要参数包括主活塞直径、阻尼孔水力直径、单向阀水力直径以及平衡位置时副气室和蓄能器内气体体积与压力作为设计变量,结合约束条件,建立了基于1/2车辆模型的油气弹簧优化设计数学模型,并应用粒子群算法进行了求解。结果分析表明,优化设计后的油气悬架系统的综合性能提高了37.33%。     

汽车后驱动桥断裂失效分析

汽车后驱动桥由多个零件焊接而成,在行驶约790000 km时该零件发生断裂。通过宏观分析、显微组织分析、化学成分分析以及断口形貌分析后认为,该零件断裂性质为疲劳断裂,主要原因为被焊接的两个零件尺寸差异较大,局部形成应力集中,再加上焊接热影响区存在焊接应力和魏氏体组织,并在汽车行进中不断受到颠簸和震动造成该区域产生裂纹源,进而在运行一定时间后发生疲劳断裂。     

Composite integrated rear suspension

Fiber reinforced plastics are undergoing extensive studies as potential structural materials for automotive applications. This paper describes the design, fabrication, weight analysis and testing of a composite integrated rear suspension in a Ford Escort vehicle. This suspension utilizes a transverse FRP leaf spring to integrate the functions of the production Escort stamped steel lower arms and coil springs. The spring was designed using previously developed composite design procedures. The results show concept feasibility, a vehicle weight saving of 7 lb, good ride, noise, vibration and harshness (NVH) characteristics. A reduction in roll stiffness points out the need for development in the design of the center clamp attachment to the body structure. This study demonstrates the viability and potential of fiber reinforced composites in automotive suspension systems.     

Evaluation of a leaf spring failure

The determination of the point of failure during an accident sequence of a rear leaf spring in a sport utility vehicle is presented in terms of fracture surface analysis and residual-strength estimates. Marks at the scene of the accident pointed to two possibilities for the point of failure: marks in the roadway at the start of the accident sequence and a rock strike near the end of the sequence. Evidence from rust and chemical contamination on the fracture pointed to the spring having been cracked in half prior to the accident. Extensive woody fracture and secondary cracking at the midplane of the spring was evidence for segregation and weakness in the spring. Stress estimates for the effect of both the weakness and prior cracking on the residual strength of the spring revealed reductions in strength of the spring that could produce fracture at the start of the accident sequence. The point of failure of the spring was placed at the start of the accident sequence.     

Overlaying welding technology and performance of axle tube remanufacturing

Screw failure is one of the main scrap forms for rear axle tube, and thread turning after surfacing is a common means of remanufacturing. This paper takes rear axle tube as the main research topic, which is made of 40Mn and provided by an axle company. Manual electric arc welding, CO2 shielded arc welding and argon shielded arc welding are carried to overlay the damaged thread. The deposited metal consists of two welding material lays.Welding process and overlay properties are characterized by the test and analysis of microstructure, residual stress and hardness of surfacing layers. The results show that
argon shielded arc welding is an effective method to repair the failure thread; its microstructure of fusion area is meticulous and uniform; its residual compressive stress (absolute value) of welding surface is the biggest among the three welding methods; its hardness curve is relatively flat and appropriate for turning.     

考虑随机因素的汽车悬架参数多目标稳健优化

为了稳健地提高汽车平顺性,减少轮胎对路面破坏。以某载货汽车的四自由度悬架模型为研究对象,同时考虑制造精度的影响,以车身垂直加速度、前后轮胎动载荷的均方根值的统计均值和方差为目标函数,采用蒙特卡罗抽样法和自适应多目标遗传算法对悬架参数进行稳健优化。结果表明：优化后的悬架弹簧刚度减少而阻尼系数增大,性能有大幅度改善,与传统的优化设计相比更符合实际情况,且具有更强的抗干扰能力。     

Failure analysis of an automobile damper spring tower

The cause of a passenger car’s damper spring tower early failure is investigated in this paper. Inspection of the road surface, tire inflation pressure, suspension, and service load are firstly done in order to determine the further test procedures and analysis methods. The static stress of the spring tower caused by the body weight is calculated by finite element model. Public road tests with an equipped car are carried out to simulate the real usage by the customers. With the measured strain signals of different test conditions and local strain–life method, fatigue life prediction is made. The calculated fatigue life coincides with the actual failure mileage, and it turns out that the broken spring damper causes the early failure of the spring tower. It is suggested that more emphasis should be taken on the durability design and test of the spring damper.     

55CrSi弹簧钢失效分析与研究

本文利用扫描电镜对弹簧钢的金相组织、断口及表面进行观察分析,研究其失效原因,结果表明此弹簧钢断裂为早期疲劳断裂,裂纹源萌生于并圈处,由于该处间隙过小,一则不能保证喷丸的效果,二则增加疲劳过程的接触疲劳应力及加重表面损伤,另外该处喷丸微细粒子未清洗干净,相当于表面有一夹杂在运行时遗留在并圈处表层,导致表面损伤,并诱发微裂纹而导致弹簧早期疲劳断裂。     

J型夹子失效分析

某混凝土搅拌车上的U型夹子在使用中发生断裂。采用化学成分分析、宏观检验、力学性能测试及金相检验等方法对断裂U型夹子进行了分析。结果表明：由于螺母未紧到位产生空隙,导致压板位置松动而使U型夹子在使用过程中受到的剪切力增大,加之其显微组织存在缺陷,造成其断裂失效。     

Failure analysis of an automobile valve spring

This paper presents the failure analysis of an automobile valve spring which failed in service. The fractured surfaces as well as the surface of the spring material close to the fractured surface were examined in a scanning electron microscope at suitable magnifications. Optical microscopy was performed to evaluate the basic microstructure of the as-received material. Detailed electron microscopic studies have indicated that the failure was due to the presence of non-metallic inclusions near the surface of the spring material.     

Failure assessment of a leaf spring eye design under various load cases

This paper analyzes the capability of various leaf spring eye designs to prevent failure under braking, cornering, and pothole striking loading conditions. A leaf spring is a vital suspension component of heavy trucks, such that the failure of leaf spring eyes could cause fatal accidents. However, the current design of leaf spring support eyes is solely estimated based on the maximum vertical loads exerted on the leaf spring. The actual torsion or shear loads exerted by the ground to the leaf spring eye extremely high, but the experimental proving ground methods are too expensive to perform load analysis. In this analysis, the forces exerted on the spring eye are simulated under extreme load cases, such as braking, cornering, and pothole striking. The magnitudes of the different loadings were extracted from a multibody dynamics model and were used as the load inputs to the finite element explicit simulation. The principal surface stresses of four different spring eye designs were obtained and compared to the material yield and the ultimate tensile strengths to evaluate the sustainability of the spring eye during extreme load cases. Results show that a minimum thickness of 17 mm is sufficient for the leaf spring eye design to prevent failure under extreme torsional loadings. This research provides insightful analysis of leaf springs to prevent the occurrence of failure during engineering design.     

Design and failure modes of automotive suspension springs

This paper is a discussion about automotive suspension coil springs, their fundamental stress distribution, materials characteristic, manufacturing and common failures. An in depth discussion on the parameters influencing the quality of coil springs is also presented.

Following the trend of the auto industry to continuously achieve weight reduction, coil springs are not exempt. A consequence of the weight reduction effort is the need to employ spring materials with significantly larger stresses compared to similar designs decades ago. Utilizing a higher strength of steel possesses both advantages and disadvantages. The advantages include the freedom to design coil springs at higher levels of stress and more complex stresses. Disadvantages of employing materials with higher levels of stress come from the stresses themselves. A coil’s failure to perform its function properly can be more catastrophic than if the coil springs are used in lower stress. As the stress level is increased, material and manufacturing quality becomes more critical. Material cleanliness that was not a major issue decades ago now becomes significant. Decarburization that was not a major issue in the past now becomes essential.

To assure that a coil spring serves its design, failure analysis of broken coil springs is valuable both for the short and long term agenda of car manufacturer and parts suppliers. This paper discusses several case studies of suspension spring failures. The failures presented range from the very basic including insufficient load carrying capacity, raw material defects such as excessive inclusion levels, and manufacturing defects such as delayed quench cracking, to failures due to complex stress usage and chemically induced failure. FEA of stress distributions around typical failure initiation sites are also presented.     

Light composite elliptic springs for vehicle suspension

For composites to compete in vehicle suspension applications, it is essential to control their failure by utilising their strength in principal direction instead of shear. This can be achieved efficiently by employing a new configuration instead of existing one. This study marries between an elliptical configuration and the woven roving composites.

In this paper, the influence of ellipticity ratio on performance of woven roving wrapped composite elliptical springs has been investigated both experimentally and numerically. A series of experiments was conducted for composite elliptical springs with ellipticity ratios (a/b) ranging from one to two. Typical failure histories of their failure mechanism are presented and discussed. In general, this study demonstrated that composites elliptical spring can be used for light and heavy trucks and meet the requirements, together with substantial weight saving. The results showed that the ellipticity ratio significantly influenced the spring rate and failure loads. Composite elliptic spring with ellipticity ratios of a/b 2.0 displayed the highest spring rate.     

爆炸冲击下悬挂系统性能验证及参数分析

基于地雷爆炸冲击环境下悬挂系统抗爆炸冲击性能的研究日益受到关注。针对某特种车辆在爆炸冲击环境下悬架系统的缓冲吸能性能进行研究,通过模态分析与模态试验对比验证有限元模型的准确性;建立整车爆炸环境,利用有限元仿真的方法对比分析防雷板加速度、车身底板加速度、假人小腿受力峰值,验证悬挂系统对车辆防护性能的作用。通过改变钢板弹簧刚度和弹簧阻尼系数进行悬挂系统参数分析。研究发现:无悬挂系统和有悬挂系统相对比,假人小腿受力峰值增加了57.3%;钢板弹簧片数为3时,假人小腿受力分别比2、4片时减少5.4%、6.4%。仿真结果表明了悬挂系统在地雷爆炸冲击环境下具有吸能缓冲的作用,且悬挂系统刚度影响整车的抗爆炸冲击能力。     

Failure analysis of a passenger car coil spring

Investigation on the premature failure of suspension coil spring of a passenger car, which failed within few months after being put into service, has been carried out. Besides visual examination, other experimental techniques used for the investigation were (a) microstructural analysis and fractography by scanning electron microscopy (SEM), (b) inclusion rating by optical microscopy, (c) hardness testing, (d) residual stress measurement by X-Ray diffraction (XRD) and (e) instrumental chemical analysis. Inherent material defect in association with deficient processing led to the failure of the spring.     

油气悬架在工程车辆中的应用及关键技术

车辆悬架系统关系到汽车的行驶平顺性和操纵稳定性.传统悬架无法在各种行驶条件下提供良好的减振性能.油气悬架系统是集弹性元件与阻尼元件于一体的悬架装置.根据工程车辆实际发展现状,结合国内外油气悬架系统先进技术及工程应用,论述了油气悬架研究的关键技术.认为油气悬架是发展现代工程车辆的关键结构,能够满足工程车辆平顺性和操纵稳定方面的要求.