Browse Topic: Fatigue

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Durability Validation of Full Vehicle Structures Using Strain Correlation and RLDA-Based Simulations2026-26-05231/16/2026
Durability validation of full vehicle structures is crucial to ensure long-term performance and structural integrity under real-world loading conditions. Accurate strain correlation between physical testing and finite element (FE) simulations plays a key role in the validation, ensuring reliable predictions of vehicle durability. In this paper, a comprehensive methodology for strain correlation on a full vehicle subjected to torture track testing is implemented. Strategic placement of strain gauges is determined through a combination of static analysis, modal analysis, and identification of critical stress regions in the FE model. Strain gauges were installed on key structural locations of a prototype to capture strain responses under severe loading environments. Simultaneously, vehicle wheel loads were recorded on the torture track to build a detailed Road Load Data Acquisition (RLDA) dataset at critical hard points, Loads measured in terms of wheel loads (WFT) are fed to MBD model to
JAJU, MAYUR, Dokhale, Sandeep, Gadre, Nilesh, Patil, Sanjay
Next-Gen Driver Health and Wellness Platform for Fatigue Detection and Emotional Wellbeing Monitoring2026-26-06391/16/2026
Driver fatigue and emotional distress are major contributors to traffic accidents, especially among long-haul and professional drivers, making their detection a critical area in road safety and public health. While existing research has explored various sensor-based and wearable solutions to monitor driver states, these approaches often suffer from high cost, intrusiveness, or limited scalability. Camera-based systems have recently gained attention for being less invasive and more practical for real-world deployment; however, many still depend on multiple sensors or cloud-based processing, which raise concerns around energy consumption, privacy, and integration complexity. To address these gaps, we present a sustainable, camera-only Driver Health and Wellness Platform for real-time fatigue detection and emotional wellbeing monitoring. The system leverages a single in-cabin camera and applies lightweight, edge-optimized computer vision models to analyze facial features, eye dynamics
Iqbal, Shoaib, Imteyaz, Shahma
Assessing the impact of hole piercing edge quality on fatigue samples for S550MC steel sheet.2026-26-03061/16/2026
The exceptional strength, formability, and weldability of S550MC steel sheets make them a cornerstone material in the automotive industry. These properties translate into the creation of high-performance automotive components like chassis parts, structural reinforcements, and safety cages, ultimately contributing to enhanced vehicle safety and overall performance. Furthermore, S550MC steel boasts excellent fatigue resistance, a critical factor for ensuring long-term reliability in demanding automotive applications that experience repeated stress cycles. However, beyond its inherent properties, optimizing the performance of S550MC components hinges on a nuanced understanding of the critical relationship between hole edge quality and fatigue failure. This meticulous study delves into the impact of hole-piercing clearance on the quality of the hole edges in modified fatigue samples manufactured from S550MC steel, and its effect on the fatigue life. The surface morphology was assessed
Nahalde, Sujay, Hingalje, Abhijeet, Ughade, Vikas, Singh, Udita, More, Hemant
Experimental and Numerical Investigation of Modal Behaviour in Electric Two-Wheeler Frames2026-26-03101/16/2026
This research investigates the dynamic characteristics of an electric two-wheeler chassis through a combined experimental and numerical approach. The study commences with the development of a detailed CAD model, which serves as the basis for Finite Element Analysis (FEA) to predict the chassis's natural frequencies and mode shapes. These numerical simulations offer initial insights into the structural vibration behaviour crucial for ensuring vehicle stability and rider comfort. To validate the FEA predictions, experimental modal analysis is performed on a physical prototype of the electric two-wheeler chassis using impact hammer excitation. Multiple response measurements are acquired via accelerometers, and the resulting data is processed to extract experimental modal parameters. The correlation between the simulated and experimental mode shapes is quantitatively assessed using the Modal Assurance Criterion (MAC). This matrix provides a measure of the consistency and similarity between
Das Sharma, Aritrya, Iyer, Siddharth, Prasad, Sathish, Anandh, Sudheep
Investigating Thermal Fatigue Cracks in Exhaust Manifolds of Longitudinally Mounted 1.2L 4-Cylinder Engines2026-26-04881/16/2026
This study addresses the challenge of ensuring the durability of closed couple exhaust manifolds in the compact engine bays of modern vehicles, focusing on a longitudinally mounted 1.2L 4-cylinder engine. The original sheet metal Exhaust manifold design failed thermal fatigue bench durability test, requiring a complete redesign to improve strength without changing materials. Initial simulation predictions significantly deviated from physical test results, with repeated cracks observed during accelerated thermal fatigue bench testing, despite simulations predicting a higher number of cycles before failure. This difference highlighted the need for a deeper understanding of the manifold's failure modes, primarily thermal fatigue, and mechanical vibration during engine transients. The design of experiment (DOE) approach was used to find the effect of different parameters e.g., gas temperature, surface temperature, air flow, thermal gradient, on the durability result & also to understand
Krishnan, K.S.Gopala, Mishra, Ashutosh, Yadav, Sanjay Kumar, Kumar, Deepak, Tripathi, Manas, kumar, prabhakar
Comprehensive Durability Assessment of Planet Carrier in Heavy-Duty Tipper Gearboxes Using RLDA Torque Data2026-26-04431/16/2026
In heavy-duty tippers, where challenging conditions demand high torque, planet carriers play a crucial role by enabling efficient load distribution and torque transmission while supporting gear ratio and speed variation in space-constrained systems such as automatic transmissions, hybrid drivetrains, and electric vehicles. This paper focuses on the comprehensive durability performance assessment of planet carriers using duty cycles derived from RLDA measurements for a heavy-duty tipper gearbox development program. The existing Design Validation Plan (DVP) for the planet carrier considers first gear utilization of 10-15% at 40% vehicle overload, in line with historical data. However, recent trends in mining applications revealed vehicle overloads of 55-65%, leading to an increase in first gear utilization (25-35%). This shift presents challenges for OEMs to enhance design durability while incorporating additional safety margins to meet the demands of a competitive, cost-driven market
Bagane, Shivraj, Pendse, Ameya
Enhanced Methodologies for predicting Automotive Wheel Bearing life and damage using RLDA2026-26-04821/16/2026
The durability of wheel bearings is assessed in terms of raceway life and flange life. Raceway life focuses on the performance and damage tolerance of rolling elements, while flange life evaluates the structural integrity of wheel flanges under operational stresses. Traditionally, durability predictions relied on conventional design methods and analytic formulas for raceway spalling, as well as static load assumptions for flange fatigue analysis. Recently, integrating design of experiments (DOE) with traditional approaches has enhanced these methods, enabling systematic evaluation of design variables and loading conditions. This paper introduces a methodology for analysing raceway life and damage in automotive wheel bearings using RLDA (Road Load Data Acquisition) data. The process involves acquiring raw deterministic load data, filtering it to preserve high-peaked signals, and transforming the filtered data into block cycles derived from load time histories. Each block cycle contains
Narendra, Vishwanath, Mane, Yogiraj, Paua, Ketan, Singh, Ram Krishnan, Vellandi, Vikraman
Thermo-Mechanical Fatigue Assessment of Cylinder Heads Using Advanced Simulation Techniques2026-26-04651/16/2026
Thermo-mechanical fatigue (TMF) is a critical durability concern for cylinder heads in internal combustion engines, particularly under severe cyclic thermal and mechanical loads. TMF-induced damage often initiates in geometrically constrained regions with high thermal gradients and can significantly reduce component life. As performance demands increase, understanding and mitigating TMF becomes essential to ensure the structural integrity and long-term reliability of engine components. This study presents a simulation methodology for evaluating thermo-mechanical fatigue (TMF), a temperature-dependent low-cycle fatigue (LCF) mechanism that arises from repeated thermal expansion and contraction under mechanical constraints, leading to cyclic plastic deformation and damage. The methodology consists of two key phases. Phase I involves global finite element (FE) simulations—both thermal and structural—to obtain temperature and displacement fields under rated and idle engine conditions
Ghotekar, Sunil, Kumbhar, Dipak Madhukar, Pendse, Ameya
Wheel side load calculation using the strain measurement on swingarm and duty cycle development2026-26-05831/16/2026
Typically duty cycle development for any component carried out in the absence of direct acting load will be based on the measured strain from the Road Load data Acquisition(RLDA) and comparing it with the rig level testing. The biggest drawback from such an approach is the fact that the selected loads can be drastically different from the actual experienced peak load from the actual RLDA. This happens because the strain gauges will have sensitivity toward all three directional loads and sometimes due to complex structure design uni-directional sensitive locations are difficult to find out or strain gauge. This will lead to over predicting the loads in some cases and the selected load may end up yielding the component in a single cycle itself. This paper discusses the method employed to calculate the loads at the input load location using the strain gauges which are cross sensitive and using that input loads to select the loads for the testing of the component. Also it talks about the
Anandh, Sudheep, Prasad, Sathish, R S, Mahenthran
Fatigue Life Prediction Methodology for Vehicle Suspension System and correlation with Physical Test2026-26-04591/16/2026
Fatigue Analysis is a safety critical area in design engineering for load bearing members. The design of a durable suspension system forms the foundation of vehicle architecture. The challenge lies in accurately predicting fatigue in critical areas to reduce field failures, primarily due to the absence of a validated methodology for fatigue calculation. This study provides an overview of fatigue assessment for Knuckle assembly/Rear Twist Beam based on digital Road Load/test Data for Finite Element Analysis (FEA) process for design development. This study makes use of Computer Aided Engineering (CAE) solvers such as Optistruct for model setup and fatigue tool such as nCode/FEMFAT for Fatigue Analysis. The methodology used for Fatigue estimation of rear suspension components such as Rear Twist Beam and Knuckle assembly is based on Digital Road Load Data/duty cycle loads applied to the suspension components at the hard point location at assembly level. The fatigue process used for
Kokare, Sanjay, Nagapurkar, Tejas, Iqbal, Shoaib
Investigation of Fatigue Durability Failure Mechanisms in High-Pressure Hydraulic Pipes of Power Steering Systems2026-26-05421/16/2026
Abstract—The high-pressure hydraulic pipeline in the power steering system is a vital component for ensuring optimal performance. During warranty analysis, leakage incidents were observed at the customer end within the warranty period. The primary factors contributing to these failures include pipe material thickness, material composition, mechanical properties, and engine-induced vibrations. This study investigates fatigue-related failures through detailed material characterization and Computer-Aided Engineering (CAE) based on real world usage road load data collected. The objective is to identify the root causes by examining the influence of varying pipe thickness on fatigue life. The investigation discovered that crack initiation predominantly occurred on the concave side of bent pipe sections, specifically on the engine-side high-pressure steering line, which is connected to the power steering pump mounted on the engine. Fracture surfaces exhibited characteristics consistent with
SURVADE, LALIT, Koulage, Dasharath Baliram, Biswas, Kaushik
Study of Style wheel rim failure Due to Rim and disc assembly interference2026-26-05411/16/2026
This study focuses on the investigation of wheel rim failures near weld zone during repeated cornering induced by interference between the rim and disc during the wheel manufacturing assembly process. Strain gauges were employed to capture real-time stress and strain distributions at critical zones during interference fitting. The experimental results revealed that improper interference levels lead to significant stress concentrations, often surpassing the material's elastic limit, initiating micro-crack formation and promoting fatigue failure. Detailed strain analysis indicated that both radial and axial stresses contribute to long-term structural degradation. The study highlights the critical role of dimensional tolerances, surface finishes, and assembly forces in minimizing stress-induced failures. Recommendations are provided for optimizing design and assembly practices to enhance the durability and reliability of automotive wheels.
P, Praveen, DEsigan, Lakshmipathy, K, CHANDRAMOHAN, C, Santhosh
Accelerating Product Development Life Cycle through Digitalization of Fatigue Life for Structural Components2026-26-04961/16/2026
In today’s competitive market, accelerating product development without compromising durability is critical. Durability is a key benchmark for assessing the quality and reliability of automotive products. To meet rising customer expectations and regulatory demands, the industry must develop vehicles that offer high performance and reduced weight while ensuring safety. A well-engineered vehicle must retain structural integrity and functionality under normal operating conditions and withstand extreme load events without critical failure. Achieving this requires effective Road Load Data Acquisition (RLDA), integrated with robust design practices and efficient validation processes. However, physical RLDA is time-consuming and costly, as it depends on prototype vehicles that are often available only in the later development stages. Failures identified during these late-stage tests can delay the product launch significantly. To address these challenges, this paper introduces a digital
Kokare, Sanjay, Dwivedi, Sushil, Siddiqui, Arshad, Iqbal, Shoaib
Development of Door Impact Loads Using Frugal use of Pedal Force Sensor2026-26-05381/16/2026
The first step in designing or analyzing any structure is to understand “right” set of loads. Typically, off-road vehicles have many access doors for service/getting into cab etc. Design of these doors and their latches involve a knowledge of the closing loads when the door is shut mostly with an impact of varying magnitudes. In scenarios of these impact events, where there is sudden change of velocity within few milliseconds, produces high magnitude of loads on structures. One common way of estimating these loads using hand calculations involves evaluating the rate-of-change-of-momentum. However, this calculation needs “duration of impact”, and it is seldom known/difficult to estimate. Failing to capture duration of impact event will change load magnitudes drastically, e.g. load gets doubled if time-of-impact gets reduced from 0.2 to 0.1 seconds and subsequently fatigue life of the components in “Door-closing-event” gets reduce by ~7 times. For these problems, structures are usually
Valkunde, Sangram, Ghate, Amit, GAGARE, KIRAN
Decision-fatigue mitigation in Automotive HMI System2026-26-06521/16/2026
Abstract - With advent of digital displays in driver cabins in commercial vehicles, the drivers are getting offered with many features. Due to availability of vast number of features, drivers face decision fatigue in choosing the appropriate features. Many are unaware of all available functionalities displayed in the HMI System, leading to a bare minimum usage or complete neglect of helpful features. This not only affects the driving efficiency but also increases cognitive load, especially in complex driving scenarios. Instead of manually choosing between multiple settings, the driver can simply activate a recommendation mode, allowing the system to optimize selections dynamically. Novelty of this proposal focuses on introducing Intelligence in HMI Systems in such a way that it will maximize the usage index and reduce decision fatigue in drivers. To achieve this, an AI-driven recommendation system is introduced, based on User Customization and Adaptive Learning Model along with ML
K, Sunil, Dhoot, Disha
AI-Driven Stress and Fatigue Life Prediction of Engine Connecting Rods using Geometric Deep Learning2026-26-06331/16/2026
The connecting rod is one of the critical components of the engine which is subjected to complex cyclic loading, demanding precise evaluation of stress distribution and fatigue life. Conventional Finite Element Method (FEM)-based simulations, while accurate, are computationally expensive and time-intensive—especially when iterating through multiple design variations. To address this, we present an AI/ML-based predictive framework using Graph Neural Networks (GNNs) and Geometric Deep Learning (GDL) techniques to efficiently predict stress and fatigue life of the connecting rod. The methodology involves representing FEM mesh data as graph structures, where nodes and edges capture geometric and physical relationships. GNN architectures, including MeshCNN and PointNet++, are trained on historical simulation data to learn spatial dependencies and nonlinear mappings between geometry, load conditions, and resulting stress/life outputs. The framework significantly reduces computation time
Pathan, Mohammed Shakil, K, Karthikeyan, pilla, sashanka, S Kangde, Suhas
Structural analysis and Design optimization of Cylinder Head of Cummins Light duty Engine for Medium Wheelbase (MWB) pick-up truck2026-26-04951/16/2026
This paper presents the design, structural analysis, and risk assessment done by Cummins to evaluate the structural integrity of Light Duty engine cylinder head for a Medium Wheelbase (MWB) pick-up truck. Initially, Cummins used F2.5L (4-cylinder) engine that has 154hp, but rising market demands for more power, fuel efficiency, lower cost and weight, and future emission compliance led to customer requirements for 177hp (Drive New F2.5L, 15% uprate) and 197hp+ (Drive New F3.0L, 22% uprate) from the same base engine. The increase in power requirement possesses challenges on critical components, especially cylinder heads in terms of thermal and structural limits. This paper addresses the challenges and risks in current cylinder head design driven by new power demands, specifically reduced fatigue margins in the water jacket area and increased temperatures on the combustion face under high thermomechanical loads. It explores the design modifications made to the cylinder head design to
Pathak, Arun Jyoti, Adiverekar, Vaidehi, Singh, Rahul, Biyani, Mayur
Effect of pipe bending by rotary tube bending process on durability of frame structure2026-26-03701/16/2026
For Original Equipment Manufacturers (OEMs), ensuring the overall quality of two-wheeler frames hinges on robust process capability and meticulous design considerations. A comprehensive Computer-Aided Engineering (CAE) simulation approach, integrating manufacturing processes and design elements, is vital for achieving optimal durability. This study focuses on developing such an approach through detailed finite element analysis of Cold Electric Welded (CEW) annealed round pipes used in frame construction. We simulate the bending process, capturing structural deformation and residual stresses. A 3D mechanical model with realistic tooling geometries and contact interactions accurately represents shape changes, ovality, and wall thickness redistribution. Unlike Electric Resistance Welded (ERW) pipes, CEW pipes, due to annealing, offer a stress-free initial state, allowing precise deformation analysis. Simulation results demonstrate significant geometric alterations in the bend zone
Rajwani, Ishwar, khare, Saharash
Exhaust Hot end system Transient Heat Transfer Analysis using Heat Transfer Coefficient (HTC) approach, Thermo-Mechanical Fatigue Analysis to evaluate thermal durability and physical validation through Thermo-Shock Testing2026-26-02241/16/2026
Exhaust system suppliers are continuously enhancing their processes by adopting advanced simulation techniques and expedited testing procedures for optimizing exhaust systems. This aims to reduce time to market, accelerate vehicle launches, and ensure first-time right and consistent compliance with performance and durability standards. Traditionally, the CFD team conducts Conjugate Heat Transfer (CHT) analysis on the exhaust hot end system using input conditions such as engine-out gas temperature and maximum mass flow rate. The CAE team then performs steady-state heat transfer analysis by sharing the structural CAE model with CFD for CHT skin temperature mapping. Once steady state heat transfer analysis complete, skin temperature plots are to be compared with CFD to match CHT temperature results. These results are used for steady-state thermo-mechanical analysis across all heat-up cycles and assume system under ambient temperature for all cool-down cycles to evaluate system thermal
Natarajan, Suresh, J Y, Raja Shangara Vel
Risk assessment of cold side components using quick modal analysis correlation technique.2026-26-04411/16/2026
Abstract: Modal analysis is performed to determine the natural frequencies and mode shapes of a structure or system. It helps engineers understand how a system vibrates and how external forces, such as mechanical loads, might excite unwanted resonances. To check the stresses due to vibration inputs, certain G levels are assumed, and stresses are scaled to those vibration levels. This gives an understanding of the stresses of component with respect to its EFR limit and design margins are calculated. But, assumed acceleration levels in pre-prototype stage level can over predict or under predict the design margins. A quick modal analysis corelation technique can be used by using test measured accelerations conducted at prototype stage of the program. In this work, a modal analysis corelation technique is used to perform risk assessment of intake manifold. The intake manifold failed due to high vibration levels which were not captured from high cycle fatigue analysis with assumed G-level
Bale, Shrikant Bhaskar, Bawache, Krushna
Evaluation of Shear Trim Edge in HSLA Steel for Automotive Application2026-26-02861/16/2026
Quality of the Shear Trimmed edge of HSLA 550 steels is significantly affected by process variations such as Shear Trimming Clearance, trim tolerance, burr height and clamping force. All these parameters largely influence the characteristics of the Shear Affected Zone, a region on sheet metal where it undergoes deformation during the trimming process. The Shear Affected Zone is predominantly vulnerable to failure due to work hardening and the effects of strain rate, induced by the tonnage during the trimming operation. To assess the edge ductility of these materials, Tensile, Fatigue Strength, Die Punch Clearance, Roughness and Hardness Tests are carried out. These tests are crucial for applications that demand high formability and resistance to edge failure. Virtual simulation of edge trimming operation using elastoplastic material models in LS-Dyna have been performed to gain insights into burr formation and damage evolution during shearing. These simulations act as a precursor to
Thota, Badri Vishal, Kashyap, Amit, Bhuvangiri, Jaydev
CAE driven seam weld optimization for stiffness and fatigue calculations2026-26-04781/16/2026
Structural parts are joined using seam welds, spot welds and bolted connections. The strength and stiffness of any structural part are strongly influenced by the properties of their joints. Seam welds are used extensively in the automotive industry to join panels. The design and the positioning of the seam welds have a significant impact on the technical cost of the project. In the automotive industry, structural optimization and fatigue simulation have become standard applications during any development process. The conventional approach in identifying the position and number of seam welds and its length is time consuming and leads to over design. Current paper highlights developing a simulation process for seam weld optimization in identifying the optimal position and length of seam welds. The optimization workflow is set up in CAE with design objective of minimizing the number of seam welds and finding the optimal length by meeting stiffness targets and fatigue life of seam welds
Gudipati, Raja Shekar Reddy
FATIGUE FAILURE ANALYSIS FOR AUTOMOTIVE TRASNMISSION2026-26-05771/16/2026
A fatigue failure in the transmission input shaft was identified during a bench-level endurance test under 2nd gear loading conditions. The test transmission’s input shaft comprises fixed 1st, reverse, and 2nd gears, with the remaining gears mounted as floating. The shaft was subjected to cyclic torsional loads, and failure occurred after a defined number of cycles. Metallurgical analysis revealed a brittle fracture surface with crack initiation at the outer surface, propagating to core in a helical pattern, ultimately resulting in complete shaft fracture. To monitor and replicate the failure, the test setup was instrumented with a Reilhofer Delta Analyzer for early fault detection. TTL signals from accelerometers mounted on the transmission and a bench speed sensor were fed into the system, which generated FFT spectra and trend indices. A warning alarm triggered upon deviation in the trend index, indicating premature damage initiation. The test was subsequently halted for component
Navale, Pradeep, Kushwaha, Rakesh, Patel, Hiral
Integrating Road Load Data Acquisition and Signal Processing Techniques to Generate Reliable Drive Files for Electrodynamic Shakers in Testing the Exhaust Systems of Off-Highway Applications2026-26-05521/16/2026
Generating a reliable drive file for an electrodynamic (ED) shaker from Road Load Data Acquisition (RLDA) and validating its correlation with real-world conditions through damage and fatigue analysis is crucial for accurate component testing, particularly in complex systems like off-highway exhaust systems. This paper presents a methodology for creating such a drive file and establishing its validity, highlighting the necessity of ED shakers for simulating the intricate dynamic loads experienced by these systems. The process begins with acquiring comprehensive RLDA under representative operational conditions of the off-highway vehicle. Drive files are generated using this data, which records accelerations at important exhaust system mounting locations. Advanced signal processing techniques are employed to condense the raw RLDA into a format suitable for shaker control. To establish proper correlation, the generated drive file is used to excite the exhaust system on an ED shaker
Khaire, Santosh Ramdas, Khaire, Rushikesh, Yadav, Dnyaneshwar
Accurate Component Load Prediction with Hybrid Test – FEA Approach.2026-26-03661/16/2026
Knowing accurate loads acting on the structure is still a main pain area for analyst. Accurate fatigue analysis through FEA is still a difficult task because of uncertainties associated with component load profile. Even for known duty cycle, approximation involved in measurements and load cascading techniques (MBD simulation models) put limits on accuracy of component load prediction. Small error in loads can lead to very large error in fatigue life calculations. Various researches proposed various innovative alternate means for accurate component load prediction and published in literature over past few decades. Author has explored and developed hybrid Test-FEA approach to estimate component loads based on robust strain-load transformation and pseudo inverse technique. This approach is based on effective use of strain transformations along with accurately measured strain data to calculate accurate load histories. The accuracy of load estimates depends upon number of factors such as
Pratap, Rajat, Apte Sr, Amol, Babar, Ranjit
Impulse Testing of Hydraulic Tubing and Fittings, S-N CurveAS4265A (Current)9/29/2025
This aerospace test standard establishes the requirements and procedures for evaluating and comparing the impulse fatigue performance of high pressure hydraulic fittings and tubing. this test method may be used to test similar fluid system components, if desired.
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Understanding the Aero-mechanical Behavior of a MGB Cooling FanF-0081-2025-02445/20/2025
The oil cooling fan of a Main Gearbox (MGB) is a mechanically-driven component whose purpose is to force an air flow through an air cooled oil cooler; its performance is crucial in ensuring that the MGB oil temperature does not exceed a predefined threshold, set to alert the crew in case of an abnormal situation. The design and the certification of a cooling fan is a process involving several steps and multiple disciplines; mechanical design, aerodynamic analysis, dedicated tests carried out both on rigs and at aircraft level need to be exploited as complementary tools to assess the correct aero-mechanical behavior of the system. The aerodynamic assessment is associated to performance, measured in terms of MGB oil temperature: considering a comparison between two cooling fans, one outperforms the other if the resultant MGB oil temperature is lower, keeping the same boundary conditions (engine torque, wind speed, ambient temperature, etc.). The correct mechanical behavior is instead
Sangiovanni, Andrea, Scaltritti, Diego, Podda, Daniele, Pisani, Paolo, Sartori, Sergio, Alari, Lorenzo
Integration of Machine Learning and Probabilistic Methods for Structural Life Assessment in Helicopter Digital TwinsF-0081-2025-02665/20/2025
Traditional safe-life methodologies for rotorcraft structural components often result in overly conservative life estimates, increasing maintenance costs and reducing aircraft availability. This study explores the integration of digital twin concepts with probabilistic modeling and machine learning to enhance structural life assessment, demonstrated through a practical case involving the Royal Canadian Air Force CH-146 Griffon helicopter. A probabilistic fatigue model determines a fatigue life distribution by incorporating material variability and uncertain operational loads inferred directly from flight data. Unlike conventional approaches, this method dynamically estimates load spectra, including uncertainty instead of relying on conservative assumptions. Monte Carlo simulations are used to quantify structural risk and assess the impact of load and material uncertainties. Sensitivity analyses highlight these uncertainties’ contributions to failure probability. The proposed approach
Asaee, Zohreh, Renaud, Guillaume, Bombardier, Yan, Cheung, Catherine
Dissertation on Planet Gear Damage Resistance CapabilityF-0081-2025-02525/20/2025
A typical helicopter drive system consists of a multi-stage gearbox with highly loaded dynamic components such as gears, shafts, and bearings, crucial for safe flight and landing. Planetary reduction stages are commonly used in the final reduction stage of rotorcraft main gearboxes due to their ability to handle high torques at high gear ratios within a compact envelope. The planet gear, a critical component in this arrangement, is subjected to significant loads on both flanks of its teeth and must meet stringent weight and assembly requirements, leading to a thin rim design with integrated bearing races. This design makes the planet gear susceptible to relevant reduction of its fatigue life. This paper explores analysis methods to evaluate the damage resistance of the planetary stage assembly, focusing on the planet gear. The study aims to assess the "growth" or "no growth" condition of the planet gear against defined flaw defects. An iterative calculation loop determines the critical
Sartori, Sergio, Simonetta, Roberto, Bordignon, Livio, Riccaboni, Filippo Davide, Occhipinti, Stefano, Motta, Nicoletta, Scaltritti, Diego
Fatigue Damage Modeling in Laminated Composite Structures Based on J-Integral CalculationF-0081-2025-04145/20/2025
Advanced structural analysis methods, known as progressive damage and failure analysis tools, are being developed to predict initiation and propagation of damage under repeated loading based on capturing individual and interacting damage modes. This work develops structural fatigue life prediction capability in state-of-the-art emerging progressive damage failure analysis tool CDMat developed at the University of Texas Arlington Advanced Materials and Structures Lab. While JIntegral, implemented in CDMat, appears as the most objective and rigorous approach to predict delamination growth-based fatigue life of composite structures, the key material properties of the J-Integral fatigue model have not been measured with the adequate accuracy. This work addressees a fundamental challenge of eliminating the established and routine assumptions and developed a methodology to determine the key material properties meeting the material input data requirements for the JIntegral based structural
Nikishkov, Yuri, Nikishkov, Gennadiy, Seon, Guillaume, Makeev, Andrew, Matthews, Peter, Shonkwiler, Brian, Haynes, Robert
Fatigue Analysis of Motorcycle Rear Swing Arm on Different Road Surfaces2024-32-00464/18/2025
The rear swing arm, a crucial motorcycle component, connects the frame and wheel, absorbing the vehicle’s load and various road impacts. Over time, these forces can damage the swing arm, highlighting the need for robust design to ensure safety. Identifying potential vulnerabilities through simulation reduces the risk of failure during the design phase. This study performs a detailed fatigue analysis of the swing arm across different road conditions. Data for this research were collected from real-vehicle experiments and simulation analyses, ensuring accuracy by comparing against actual performance. Following CNS 15819-5 standards, road surfaces such as poorly maintained, bumpy, and uneven roads were tested. Using Motion View, a comprehensive multi-body dynamic model was created for thorough fatigue analysis. The results identified the most stress-prone areas on the swing arm, with maximum stress recorded at 109.6N on poorly maintained roads, 218.3N on bumpy surfaces, and 104.8N on
Chiou, Yi-Hau, Hwang, Hsiu-Ying, Huang, Liang-Yu
Usage Spectrum Contribution to Rotorcraft Dynamic Component ReliabilityF-0080-2024-00425/7/2024
Rotorcraft dynamic component fatigue lives and corresponding reliability have long been derived from three major contributors: material strength, loads, and usage. This paper provides a historical perspective of the contribution of aircraft usage to overall U.S. Army rotorcraft dynamic component reliability. A quick background of how we got to a six-nines reliability requirement is first provided. Different types of usage spectra and the nuances and trade-offs of two specific usage gathering methods, pilot surveys and usage monitoring, are discussed. Finally, I describe where usage spectrum fits into fatigue life calculations and the existing reliability policy and requirements. Each OEM (e.g., Bell Helicopter, Boeing, Sikorsky) has been free to develop their own fatigue methods over the years. These differences in method can lead to vastly different results, even with the same input parameters as evidenced by a now well-known round robin problem. There is notable variability between
Craven, Allen
A SUMS Based Usage Spectrum for the UH-60M ITE Equipped Black HawkF-0080-2024-11195/7/2024
Previous work documented the use of IVHMS data on the U.S. Army's fleet of UH-60 Black Hawk helicopters to update the fatigue lives of six specific components on the A/L and M models. This paper documents a significant expansion of the level of data applied to the usage spectrum, as well as applying it to all components on the aircraft. As a design spectrum for the yet to be fielded Improved Turbine Engine (ITE) equipped UH-60M, changes due to new engine capability needed to be addressed. The new spectrum has been developed and is being used for planning of flight testing. The spectrum along with flight test loads will be used to generate fatigue lives for the new aircraft. Once deployed for several years the spectrum will be reviewed to determine if any changes are needed. This work highlights what the Army considers to be the most significant issues when applying monitored usage to critical fatigue components, and rationale for dealing with issues such as insufficient data for
Finckenor, Jeffrey
U.S. Army Helicopter Structural Reliability and Fleet Failure Rate RequirementF-0080-2024-10885/7/2024
This paper presents a framework with associated concepts to define a method of compliance for the failure rate requirements of the Army Military Airworthiness Certification Criteria (AMACC), Chapter 5, for fleet qualification and first flight. The fleet failure rate requirement is paraphrased as less than one structural failure in 20 million flight hours at 95% confidence and applies specifically to fatigue failure of primary structural elements (PSEs). This method of compliance assumes a reliability model sufficient to support an analytical failure rate that bounds the uncertainty arising from practical constraints of an aircraft qualification program and aims to optimize the competing objectives of safety of flight and operational capability. The requirements as defined verify that the aircraft system will perform as intended for a specified fleet life and flight test program duration and serve as the analytical basis for the assessment of emergent issues identified throughout the
Janny, Stephen
Shot Peen Surface Repair: The Impact of Residual StressF-0080-2024-12275/7/2024
Shot peened components present a challenge for the structural analyst when nicks, scratches and gouges are discovered. A common repair scheme calls for blending away of the defect with an appropriate grit abrasive. Though the blending operation removes the defect, it also takes away a portion the beneficial compressive layer as well as the cold-worked material. Large repair facilities may have touch-up shot peen capability but technicians in a field repair setting typically do not. If the shot peen cannot be restored, the structural analyst must have a method to quantify the effect on fatigue life of the repaired part. The purpose of this technical paper is to substantiate analytical techniques for evaluating the fatigue life of a shot peened part after a blend operation. In addition to practical methods to estimate the magnitude of the residual stresses, a numerical method is introduced using finite element modeling of shot peen impacts with non-linear finite element code and
Conklin, Craig, Flores, Ric, Barrett, Arild
Six Nines Reliable Army Fatigue Critical Component Using Operational Loads DataF-0080-2024-11135/7/2024
This paper describes the work performed to determine a 0.999999, 6 nines, reliable fatigue critical component life using field monitored loads. The Tie Bar of the MH-47 is substantiated by Centrifugal Force (CF), which is a direct function of rotor speed, Nr, which is a monitored parameter in the Structural Usage Monitoring System (SUMS). Six nines of reliability has been the Army target for component reliability and it is generally assumed that legacy safe-life methods are near this level of reliability. With monitored loads it is possible to develop a statistical model for loads and determine an actual reliability value. This paper presents multiple methods for the Army's first attempt at establishing a retirement time using an absolute component reliability. Reliability is gained using a reduction of the Endurance Limit and mean and standard deviations of binned loads across multiple aircraft. Most notably fatigue lives can vary widely if the independent variable reliability
Finckenor, Jeffrey, Chandler, Michael, Ruffin, Aniekan, Evans, Holly
Further Applications of SUMS-based Regime Recognition in Updating the MH-47G Chinook Usage SpectrumF-0080-2024-11435/7/2024
This paper documents the re-evaluation and updates to the previous Partial Regime Recognition Spectrum effort for the MH-47G using Structural Usage Monitoring System (SUMS). Further validation of the SUMS algorithm allowed for additions to the spectrum. These additions include more refined categorization of turn and partial power descent regimes based on angle of bank and descent rates, respectively; high load prorates for turns, partial power descents, level flight, and climbs based on the Cruise Guide Indicator; exceedances of maximum density altitude; and use of occurrences for Landing and Run-On Landing regimes. Additional years of flight data from 2013 to 2019 were included in this effort. The updated usage spectrum for the Army MH-47G aircraft has been delivered to the OEM (Original Equipment Manufacturer). The OEM calculated new fatigue lives and updated the "Fatigue Substantiation Report", which will soon be fielded.
Evans, Holly, Chandler, Michael, Finckenor, Jeff
Fatigue Simulation Method based on the Calculation of the J-Integral in the Cohesive Zone Delamination ModelF-0080-2024-13725/7/2024
A state-of-the-art emerging progressive damage failure analysis tool CDMat has been successfully applied to multiple material systems on open-hole tension and compression, and double shear bearing laminate coupons under static and fatigue loading including simulation to ultimate failure. CDMat also successfully demonstrated component-level strength/fatigue analysis under the Air Force Composite Airframe Life Extension (CALE) and the Fail-Safe Technologies for Bonded and Unitized Composite Structures (FASTBUCs) Programs. Building on the success of CDMat an integrated software solution for certification and sustainment of rotorcraft primary composite structures is being developed. A method and an algorithm for fatigue crack growth simulation in laminated structures are proposed to improve the accuracy of CDMat fatigue predictions. The method is based on using cohesive material model, tracking material points at the crack front, and calculating the pointwise energy release rate employing
Nikishkov, Gennadiy, Matthews, Peter, Makeev, Andrew, Seon, Guillaume, Nikishkov, Yuri
Increasing the Fatigue Life of a Structural Web with a Large Rectangular Cutout Under Complex LoadingF-0080-2024-00185/7/2024
This paper details an analysis methodology for a primary structure component on a tandem rotor helicopter that has been shown to experience fatigue damage in operation. The primary structure component is a web in the aft pylon of the helicopter. The web carries a complex set of loads in flight with various forces and moments applied along its boundaries and rotor torque reacted around a large rectangular cutout in the web. Due to the complex loading applied to the web, there is no clear location that can be considered to carry a "gross" stress, rendering traditional hand calculation methods (such as the use of stress concentration factors applied to a gross stress) impractical. The analysis detailed in this paper considers the application of flight loads to Finite Element Models to determine stresses in the web, which are used to evaluate fatigue life based on various flight conditions.
Truitt, Joseph
Damage Tolerant Fracture Assessment of Cracks in Non-Standard Geometries Under Static and Fatigue Loading2024-26-02761/16/2024
Cracks on metallic components may appear due to manufacturing, handling, installation, repair, welding etc. and are controlled by quality documents. However, if cracks violate the limit defined in quality document, then either parts will be scraped or will need additional evaluation through detailed and specialized Linear Elastic Fracture Mechanics (LEFM) approach. The initial size, orientation and shape of crack, part geometry and loading highly impacts the behavior of crack growth and remaining useful life. Study has been performed to understand the effect of crack aspect ratio on stress intensity factor under different stress gradient scenario. This paper also provides the simplified methodology to address the multiple cracks in complex geometries under static and fatigue loading.
Puranik, Shashank Suresh, Pathan, Irfan, Shinde, Swapnil, Soni, Nitesh, Kindleysides, Andrew
Dynamic Stress-Strain and Fatigue Life Estimation Using Limited Set of Measured Accelerometer Data on Exhaust System using System equivalent reduction and expansion process (SEREP)2024-26-02511/16/2024
The dynamic response of structures to operating or occasional loads is crucial for design considerations, as it directly impacts the cumulative fatigue life and structural health monitoring. However, accurately determining the actual loading and structural condition, encompassing boundary conditions, environmental factors, geometry, and mechanical properties, presents challenges in practice. Significant efforts are invested in identifying these factors and developing suitable prediction models. Nonetheless, the estimated forces and boundary conditions remain approximations, leading to uncertainties and influencing the overall predicted response and resulting stress-strain analysis during subsequent evaluations. Many researchers commonly approximate the forces exciting the system using limited sets of measurement points. This approach involves estimating the forces and applying them to determine the finite element displacement and subsequent stress-strain distributions. However, this
Pratap, Rajat, Apte Sr, Amol, Poosarla, Shirdi Partha Sai
Defect based fatigue life predictions for Aluminum Castings using Simulations2024-26-02891/16/2024
Aluminum casting parts generally have inherent internal defects such as porosity which lowers the fatigue strength of such castings. Accounting for such a fatigue strength reduction for Aluminum casted parts is the primary purpose of this paper. Authors have used Murakami et al [1] approach to calculate a ‘porosity correction factor’ for fatigue. The actual material S-N curve is modified using fatigue factors to account for the fatigue strength reduction due to presence of porosity. This approach was then validated on one of the fatigue failure cases on Aluminum casted housing. There was a close match between the test data and proposed approach for fatigue prediction. With this approach, engineers will be able to do fatigue predictions in presence of material defects like porosity with simple porosity correction factor, rather than using complex modeling of porosity in FEA or using detailed fracture mechanics methods. Engineers can also be able to provide acceptable levels of porosity
Kumar, Rohit, Gawture, Majnoo M
Quantitative Criteria for Correlating Simulation-based Fatigue Life Predictions with Test Outcomes2024-26-03061/16/2024
Fatigue life of a component is influenced by lot of factors like material, manufacturing & geometric variations and due to this there is a huge scatter in both test & predicted life through simulations. There are different methods available to account for these variations while predicting fatigue life. However, whenever a fatigue simulation engineer tries to correlate predictions with test outcomes, he/she will face a challenge as to: How to account for scatter in test? How to compare predicted life through simulations with test data? How much difference between test outcome and predictions is acceptable? To address these challenges, authors have suggested two approaches in this paper - 1. Deterministic correlation and 2. Probabilistic correlation. This paper suggests a set of criteria under both these approaches to conclude confidently that the prediction model is able to match the test outcomes. Also, the paper highlights the kind of measurements that needs to be done and the
Dasamaneni, Vinod Kumar, Gawture, Majnoo M
Effect of tire pressure on the fatigue life of an automotive three-wheeled vehicle's chassis & body.2024-26-03651/16/2024
The need and dependency on objective measurements are increasing rapidly across all industries for reliable and faster data for product validation, and the automotive industry is no different. Objective measurements are becoming increasingly popular than subjective evaluation as they offer objectivity and repeatability. Typical industry practice for structural validation is to acquire the vehicle responses, viz. spindle accelerations, wheel displacements, wheel forces, speed, strain at a few critical locations, and others as per the requirement. Vehicle responses are usually acquired on specific road surfaces, test tracks, and proving grounds. Prior to the tests or measurements, the vehicles are configured as per the company's recommendation, such as tire pressure, camber angles, engine oil, coolant oil type and quantity, load, and load distribution, to name a few. The test vehicles with which these measurements are carried are usually only with these vehicle settings. However, the
Polisetti, Sagar
Unique Optimization Approach of Axle Component and it’s Weld Life Improvement2024-26-03161/16/2024
Axles are a prominent part of automotive design. Along with a power transmission and differential system, axles support a vehicle’s weight and road-load reactions. Axles carry different attachments such as brakes and suspensions using brackets. Welds play an important role in design and longevity of bracket assemblies. Welds can be susceptible to fractures caused by intrusions akin to cracks and/or discontinuities, compounded by stress concentration due to weld profile and welding processes. Additionally, the simultaneous optimization of both brackets and welds remains a challenge with limited available methods. While topography or shape optimization techniques can enhance bracket robustness by minimizing compliance as the objective, this approach might inadvertently elevate the likelihood of weld fracture if weld dimensions are not concurrently updated. In this endeavor, compliance is used to improve weld life without affecting bracket robustness by using the Vertex Morphing
Wagh, Pranav, Sutar, Mohan, Nilangekar, Abhijit
Development of methodology for accelerated validation of axle components in relation to static load capacity2024-26-03731/16/2024
The Indian automotive industry is striving towards more safe and durable vehicles. A need was felt to study the effect of changes in axle static loads on fatigue life of the axle components. Also, there was a need to develop generic test method, as there are no test standards or generic methods available in public domain for fatigue testing of commercial vehicle axles. The study was carried out to check direct effect of change in axle loads on various connections on axle, effect of suspension configuration and force distribution, Vehicle dynamics, etc. In this paper, an India specific generic load spectra was evaluated for accelerated laboratory validation. Paper discusses the methodology as; study of heavy commercial vehicle systems, road load data collection on identified test vehicles w.r.t. test matrix finalised, India specific test loads & load spectra development, Normalisation of axle load spectra w.r.t to static axle weights and arriving at test guidelines. Comprehensive
Kuwar, Virendra S, Thorat, Omkar, Bakal, Nikhil Rajendra, Joshi, Omkar Prakash, Pawar, Prashant R, Shinde, Vikram V, Sutar, Mohan, Potdar, Anil, TAK, SACHIN, Nilangekar, Abhijit, Kulkarni, Milind
Method Of Improving Slam Durability Fatigue Of Vehicle Liftgate Subsystem For Fast-Track Vehicle Development Cycle2024-26-03021/16/2024
ABSTRACT With reference to existing literature, most OEMs are working on reducing product development time by around ~20%, to achieve seamless integration to digital ecosystem and focusing on new features catering to dynamic customer needs. The Systems Engineering approach focuses on functions & systems rather than components. In this approach, designers (Computer Aided Design) / analysts (Computer Aided Engineering) need to understand program requirements early to enable seamless integration. This approach also reduces the number of iterative loops between cross functions thereby reducing the development cycle. In this paper, we have taken a common challenge faced by Closures (Liftgate) engineering to meet slam durability fatigue life, replicating customer normal and abusive closing behavior. For modern vehicles, with faster vehicle development process, major challenges are balancing mass with improved structural and durability performance while also considering design changes with
Subramanian, Vijayasarathy, Evans, Jon, Schoenow, James, Arikatti, Karegowda
Accelerating Full Scale Fatigue TestingF-0079-2023-181665/16/2023
Bradshaw, William, Vaddadi, Dr.
Micro-Mechanics Based Gear Tooth Contact Fatigue AnalysisF-0079-2023-181605/16/2023
Xu, Biqiang, Hansen, Bruce
Multiaxial Fatigue Damage Evaluation of Bonded Repair and Efficient Performance Evaluation of a Composite Wing SectionF-0079-2023-181625/16/2023
Lua, Jim, Kariyawasam, Supun, Cui, Xiaodong, Karuppiah, Anand, Saathoff, Caleb
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