Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

A study on editing method of road load spectrum of automobile rubber isolator using time-frequency domain methods

2022-03-29
2022-01-0272
In order to enhance the efficiency of durability testing of automobile parts, a time-frequency domain accelerated editing method of road load time series of rubber mount on powertrain was discussed. Based on Stockwell Transform method and Accumulative Power Spectral Density, a new time-frequency domain accelerated editing method (ST-APSD) was proposed. The accumulative power spectral density was obtained by ST of the load time series signal of automobile powertrain rubber mounting force which is acquired by the real vehicle in the test field. Based on the accumulative power spectral density, the threshold value was proposed to identify and delete the small damage load fragments, and then the acceleration spectrum was obtained.
Technical Paper

Thermomechanical behavior of an automotive exhaust aftertreatment application

2022-03-29
2022-01-0277
An aftertreatment system is the back-end component of an automotive exhaust system, used mainly to reduce pollutant emissions. This system is exposed to high thermal loads which can exceed temperatures of 900 oC , usually they operate at temperatures under 600 oC - 700 oC, depending of the engine application. The durability assessment of a system under thermomechanical loads can be challenging due to the complexity of the technical problem, which involves complex material behavior at high temperatures and results in high thermomechanical strains and stresses. This study presents a computational approach for the lifetime assessment of an exhaust aftertreatment system subjected to thermomechanical loading. The method is composed of a fluid flow analysis to compute the temperature fields which are mapped to a mechanical analysis combined with a nonlinear elastoviscoplastic material behavior. Lastly, the lifetime of the overall assembly is assessed through a fatigue analysis.
Technical Paper

An experimental approach for exploring electrified sliding wear of EVs powertrain gears in a pin-on-disc tester

2022-03-29
2022-01-0320
In contrast to conventional powertrains from internal combustion engine vehicles (ICEV), the tribological performance of powertrains of electric vehicles (EVs) must be further evaluated by considering new critical operation conditions such as electric environments. The operation of any type of electric motor produces shaft voltages and currents generated during rotation. Furthermore, the common application of inverters to convert DC voltage of the battery into AC voltage in EVs, intensifies this problem. It has been widely reported that the induced shaft voltages and currents can cause premature failure problems in a series of powertrain components such as bearings, seals, pads, and gears due to accelerated wear and/or fatigue. It is ascribed to effects of electric discharge machining (EDM), also named, sparking wear caused by shaft currents and poor dielectric strength of lubricants.
Technical Paper

Fatigue Durability Development for Cab of Light Truck Based on Virtual Proving Ground Technology

2022-03-29
2022-01-0319
The boundary load of the light truck cab fatigue analysis is the force of the cab mounting system, which cannot be directly measured. In the absence of a physical prototype, the fatigue load of the cab cannot be extracted through virtual iteration. Aiming at the problem of fatigue analysis in the early stage of the car-free cab, the virtual proving ground technology is used to extract fatigue load and do fatigue analysis in this paper. Using the virtual road as the excitation, the simulation analysis of the whole vehicle virtual proving ground is carried out, and the wheel center load and the cab mounting force are obtained. Comparing the simulation load with the signal required on the proving ground, it is found that the extracted virtual load is consistent with the actual vehicle load in the time domain and frequency domain. The retention of pseudo-damage of the six-component load of the wheel center can meet the precision control requirements of the vehicle load decomposition.
Technical Paper

Development of FE modeling Procedures for Laser Welded Aluminum Structures in An Electric Vehicle Battery Module and Validation by Test Data

2022-03-29
2022-01-0317
High strength and thin materials are widely adopted in modern electric vehicles for lightweight design to achieve high energy efficiency. For battery modules, 5000 and 6000 aluminum are typically utilized as a structural material with a thickness range between 1 to 5 mm. Laser welding is one of the most optimum welding tools for joining such a thin material due to its unique advantages, e.g., high welding speed, high accuracy, high energy yet the smallest possible heat affect zone, etc. This paper aims to develop a simplified yet effective FE modeling procedure to simulate the laser welding effects on the aluminum structures used in electric vehicle battery modules. A sequentially-coupled thermo-mechanical analysis procedure is developed to determine the softened zone size for aluminum weldments. Then a tie-rupture weld model incorporates the softened zone to predict the weld failure strength.
Technical Paper

A Multi-axle and Multi-Type Truck Classification Model for Dynamic Load Recognition

2022-03-29
2022-01-0137
Overloading of trucks can easily cause damage to roads, bridges and other transportation facilities, and accelerate the fatigue loss of the vehicles themselves, and accidents are prone to occur under overload conditions.In recent years, various countries have formulated a series of management methods and governance measures for truck overloading.However, the detection method for overload behavior is not efficient and accurate enough.At present, the method of dynamic load identification is not perfect.
Technical Paper

Numerical and experimental fatigue investigation on a battery support plate for the pure electric vehicle

2022-03-29
2022-01-0256
As the international community strengthens the control of carbon dioxide emissions, electric vehicles have gradually become a substitute for internal combustion engine vehicles. The battery pack is one of the most important components of electric vehicles. The strength and fatigue performance of the battery support plate not only affect the performance of the vehicle but also concern the safety of the driver. In the present study, the frequency domain fatigue life of the battery support plate estimation is virtually performed on a full-scale finite element model and verified by a random vibration test. Then, with the RMS stress as the optimization objective, the frequency domain fatigue topology optimization of the battery pack support plate was carried out. The results show that the optimized structure is not only lighter in weight, but the stress at dangerous locations is significantly reduced, and the fatigue life meets the performance requirements.
Technical Paper

Natural rubber life estimation through an extreme learning machine

2022-03-29
2022-01-0251
In engineering applications, rubber isolators are subjected to continuous alternating loads, resulting in fatigue failure. Although some theoretical models are used for the fatigue life estimation of rubber materials, they do not comprehensively consider the influences of multiple factors. In the present study, a model based on the extreme learning machine (ELM) is established to estimate fatigue life of natural rubber (NR) specimens. The mechanical load (engineering strain peak), ambient temperature (23℃, 60℃ and 90℃) and shore hardness (N45 and N50) of NR specimens are used as the input variables while the measure average fatigue life as the output variable of the ELM. The regression results and predicted life distribution of the established ELM model are encouraging. For comparison, the back propagation neural network (BPNN) model and the support vector machine (SVM) model are also implemented.
Technical Paper

Loading Classification for Fatigue Design applied to Automotive Time-Series

2022-03-29
2022-01-0254
This study focuses on variable amplitude loadings applied to automotive chassis parts experiencing carmaker’s specific proving grounds. They are measured with respect to time at the wheel centres and composed of the six forces and torques at each wheel, within the standard vehicle reference frame. In the scope of high cycle fatigue, the loadings considered are supposedly acting under the structure yield stress. Among the loadings encountered during the vehicle lifetime, two classes stand out: • Driven Road: loads measured during the vehicle manoeuvre (cornering, braking). • Random Road: random loads mainly coming from the road asperity. To separate both effects, a frequency decomposition method is proposed before applying any lifetime assessment methods. The usual rainflow counting method is applied to the Driven Road signal. These loadings, depending on the vehicle dynamic, are time-correlated. Thus, the load spectra is set only thanks to the vehicle accelerations time-measurement.
Technical Paper

A fatigue life prediction method of rubber material for Automobile vibration isolator under road load spectrum

2022-03-29
2022-01-0253
Automobile rubber isolator was subjected to random load cycle for a long time in the service process, and its main rubber material for vibration isolation was prone to fatigue failure. Since the traditional Miner damage theory overlooked the load randomness, it had a prediction error problem. In order to improve the prediction accuracy of rubber fatigue life, the traditional Miner damage theory was modified by random uncertainty theory to predict the rubber fatigue life under random load. Firstly, the rubber dumbbell-shaped test column, which was vulcanized from rubber materials commonly used in vibration isolators, was taken as the research object. The uniaxial fatigue test of rubber under different strain amplitudes and strain mean values was carried out. Then the fatigue characteristic curve of rubber with equivalent strain amplitude as the damage parameter was established.
Technical Paper

Comparing stress gradient and other concepts for fatigue analysis of notched components

2022-03-29
2022-01-0252
Nowadays simulation of the fatigue life is an essential part of the development of components in the automotive and machinery industry. Weak points can be identified fast and reliable with respect to stiffness, strength and lightweight. A pure virtual optimization of the design can be performed without the need of prototypes. Only for the production release a final test is necessary. A lot of parameters influence the fatigue life as the local stress, material, surface roughness, size of the component, temperature etc. Notches have the strongest impact on fatigue life, depending on radius and shape. Stresses at the notch base are increased because the load flow is forced through a reduced cross section, or changes its direction around an inwardly curved edge. But notches cause not only an increase of the local stress. Also, the local fatigue strength is increased because of a support effect from the neighboring areas, where the stress is already reduced.
Technical Paper

Improving Keyhole Stability During Laser Welding of AA5xxx Alloys

2022-03-29
2022-01-0247
Laser welding of the magnesium-bearing AA5xxx aluminum alloys is often beset by keyhole instability, especially in the lap through joint configuration. This phenomenon is characterized by periodic collapse of the keyhole leaving large voids in the weld zone. In addition, the top surface can exhibit undercut and roughness. In full penetration welds, keyhole instability can also produce a spikey root and severe top surface concavity. These discontinuities could prevent a weld from achieving engineering specification compliance, pose a craftsmanship concern, or reduce the strength and fatigue performance of the weld. In the case of a full penetration weld, the spikey root could compromise part fit-up and corrosion protection, or damage adjacent sheet metal, wiring, interior components, or trim.
Technical Paper

Fatigue Damage of Trim Dies Manufactured or Reconditioned by Different Routes

2022-03-29
2022-01-0245
The compression fatigue behavior of sheet metal trimming die is studied. The trim dies were manufactured or reconditions through different fabrication processes and heat treatment conditions. An accelerated lab testing method is developed to evaluate die damage resistance under compressive cyclic load applied at the tool edge, analogous to sheet metal trimming die operation. The metal removal volume at the sheared edges were measured by image processing to quantify the degree of fatigue damage as a function of loading cycle number. The fatigue microstructural damage were examined with optical and scanning electron microscopies. The simulated die performances are compared among different die processing routes. A phenomenological trim die damage rate model in Paris law form was obtained and tuned with experimental data for tool life prediction.
Technical Paper

The investigation of a contact and element-based approach for Cohesive zone modelling in the simulation of Delamination propagation

2022-03-29
2022-01-0259
The CAE industry always moves towards new ways to improve the productivity, efficiency and to reduce the solution times. Conventional method of Cohesive Zone Modelling has drawback of higher computation and modelling time. Due to this problem, sometimes Engineers need to avoid simulations and rely only on some sort of approximation of crack from previous designs. This approximation can lead to either product failure or overdesign of the product. A new approach is discussed in this paper to simulate crack initiation and propagation with Cohesive Zone Modelling. Conventional method uses Cohesive zone modelling with Hex or Penta elements by assigning material with cohesive properties, which increases computation and modelling time. The new approach models Cohesive zone as contact between two bodies, thus eliminating the need to use cohesive elements which will essentially reduce the computation time as well as modelling time.
Technical Paper

Fatigue life prediction method for natural rubber material based on Extreme Learning Machine

2022-03-29
2022-01-0258
Uniaxial fatigue tests of rubber dumbbell specimens under different mean and amplitude of strain are carried out. An Extreme Learning Machine (ELM) model optimized by Dragonfly Algorithm (DA) is proposed to predict the fatigue life of rubber based on measured rubber fatigue life data. Mean and amplitude of strain and measured rubber fatigue life are taken as input variables and output variables respectively in DA-ELM model. For comparison, genetic algorithm (GA) and particle swarm optimization (PSO) are used to optimize ELM parameters, and GA-ELM and PSO-ELM models are established. The comparison results show that DA-ELM model performs better in predicting the fatigue life of rubber with least dispersion. The coefficients of determination for the training set and test set are 99.47% and 99.12%, respectively. In addition, a life prediction model equivalent strain amplitude as damage parameter is introduced to further highlight the superiority of DA-ELM model.
Technical Paper

Evolution and Redistribution of Residual Stress in Welded Plates During Fatigue Loading

2022-03-29
2022-01-0257
The presence of residual stresses affect the fatigue response of welded components. In the present study of a thick welded cantilever specimen, residual stresses were measured in an as-welded A36 steel sample and in a sample subjected to a short history of bending loads where substantial local plasticity is expected at the fatigue hot-spot weld toe. Extensive XRD measurements describe the residual stress state in a large region in front of the weld toe both in an untested as-welded sample and in a sample subjected to a short load history that generated an estimated 0.01 strain amplitude at the stress concentration zone at the weld toe. The results show that such a test will significantly alter the welding induced residual stresses. Fatigue life prediction methods need to be aware that such alterations are possible and incorporate the effects of such cyclic stress relaxation in life computations.
Technical Paper

Fatigue Endurance Limit of Fasteners in Automotive Application

2022-03-29
2022-01-0260
Fastener commonly used in automotive industry plays an important role in the safety and reliability of the vehicle structural systems. In practical application, bolted joint would never undergo fully reversed loading, there always will be positive mean stress on bolt. The mean stress has little influence on the fatigue life if the maximum stress is lower than a threshold, which is the yield stress of the bolt. However, when the sum of the mean stress and the stress amplitude exceeds the yield stress, the endurance limit stress amplitude decreases fast as the mean stress increases. The purpose of this paper is to research fatigue endurance limit of fastener and establish the threshold for safe design in automotive application. In order to obtain the fatigue endurance limit at different mean stress levels, various mechanical tests were performed on M12x1.75 and M16x1.5 Class 10.9 fasteners using MTS test systems.
Technical Paper

An Engineering Approach to Consider Stress Concentrations in Fatigue Life Predictions on Automotive Body Structures

2022-03-29
2022-01-0261
This paper proposes a new procedure for more accurate durability predictions on the edges of structural components especially on notch regions. Current CAE procedures based on elemental stress often require iterative mesh refinement to correlate predictions to experimental cracking on the edges of components. The new proposed procedure is based on element nodal stress. It is first studied theoretically on a rectangular plate with different element sizes and options and demonstrates an improvement over elemental stress methods. It is then studied on multiple examples of experimental cracks and successfully predicts issues where current elemental stress methods do not. In addition, it avoids the iterative mesh refinement associated with current methods. In summary, the new method based on nodal stress is more accurate, more efficient, and improves first time through capability on the edges of structural components.
Technical Paper

Fatigue Life Prediction and Correlation of Engine Mount Elastomeric Bushings using A Crack Growth Approach

2022-03-29
2022-01-0760
Abstract: In passenger car, suspension link bushings, engine and transmission mount bushings and bump-stops are made of elastomer material, to maximize the durability and comfort. Thus, deformation behavior of rubber and its durability is important for product design and development. In virtual engineering, simulating rubber fatigue is a complex exercise, since it needs right modeling strategy and coupon based testing material data. Principal stretches based Ogden model is used to characterize the hyper elastic deformation behavior of natural rubber. Fatigue crack growth approach used here for the fatigue analysis. Engine torque strut mount is used to control the engine and transmission fore aft motion and it is connected between body and Power Train (PT) system. Powertrain events are predominant for damage contribution of mount failure. So, it is important to predict fatigue life of mount elastomer bushing under Powertrain loading.
Technical Paper

Random Vibration Fatigue Evaluation of Plastic Components in Automotive Engines

2022-03-29
2022-01-0765
Light weighting in modern automotive powertrains call for use of plastics (PP, PA66GF35) for cam covers, intake manifolds and style covers, and noise encapsulation covers. Conventionally, in early stage of design these components are evaluated for static assembly loads & gasket compression loads at component level. However, engine dynamic excitations which are random in nature make it challenging to evaluate these components for required fatigue life. In this paper, robust methodology to evaluate the fatigue life of engine style cover assembly for random vibration excitations is presented. The investigation is carried out in a high power-density 4-cylinder in-line diesel engine. The engine style cover (with Polyurethane foam) is mounted on cam cover and the intake manifold using steel studs and rubber isolators to suppress the radiated noise.
X