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STATISTICAL ANALYSIS OF LOW CYCLE FATIGUE PROPERTIES IN METALS FOR ROBUST DESIGN

General Motors Global Technical Center-Abolhassan Khosrovaneh
General Motors Technical Center India-Karthigan Ganesan, Biswajit Tripathy
  • Technical Paper
  • 2019-28-2576
To be published on 2019-11-21 by SAE International in United States
Objective: In ground vehicle industry, strain life approach is commonly used for predicting fatigue life. This approach requires use of fatigue material properties such as fatigue strength coefficient (σf'), fatigue strength exponent (b), fatigue ductility coefficient (εf'), fatigue ductility exponent (c), cyclic strength coefficient (K′) and cyclic strain hardening exponent (n′). These properties are obtained from stable hysteresis loop of constant amplitude strain-controlled uniaxial fatigue tests. Usually fatigue material properties represent 50th percentile experimental data and doesn't account possible material variation in the fatigue life calculation. However, for robust design of vehicle components, variation in material properties need to be taken into account. In this paper, methodology to develop 5th percentile (B5), 10th percentile (B10) and 20th percentile (B20) fatigue material properties are discussed. Possible material variation in fatigue life prediction is included as B5, B10 and B20 fatigue material properties. Methodology: Fatigue strength coefficient (σf') and fatigue strength exponent (b) are obtained by performing a linear regression on true stress amplitude (∆σ/2) versus reversals to failure (2Nf) in log-log scale. Fatigue ductility coefficient (εf')…
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Determine Thermal Fatigue Requirements for PEPS Antenna Copper Wire over Vehicle Lifetime with defined Reliability Requirements.

GMTCI-Abhinav Jauhri
  • Technical Paper
  • 2019-28-2582
To be published on 2019-11-21 by SAE International in United States
Reliability states the degree to which the result of a measurement, calculation, or specification can be depended on to be accurate. And, tests according to GMW specifications represents a minimum of 15 years of vehicle life time with defined Reliability and Confidence level. In this work, actual number of thermal cycles for Thermal Fatigue tests (Thermal Shock and Power Temperature Cycle) are calculated for Copper Wire whose Coffin Manson exponent is 5. Overstressing the PEPS Antenna under thermal fatigue requirement (defined number of thermal cycles based on Reliability and Confidence requirements) will lead to broken Copper wire which will result in component’s functional failure and thus impossible to continue reliability testing. The objective of this paper is to determine thermal fatigue requirements for Antenna’s Copper wire whose Coffin Manson exponent is 5. Testing with exact number of thermal cycles will reduce the validation failures owing to broken Copper wire and thus save incurred revalidation cost. The current study is limited to only adjusting the thermal fatigue requirements (Number of Thermal Cycles) for only specific E/E…
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Design Analysis and Simulations of Components of an All-Terrain Vehicle

BITS Pilani-Pranjal Shukla, Konark Joshi, Utkarsh Rastogi, Ajith Reddy Moola
  • Technical Paper
  • 2019-28-0049
Published 2019-10-11 by SAE International in United States
A single seater All-Terrain Vehicle (ATV) is conceptualized in this paper which covers the extent of designing and simulations ranging from static structural, fatigue analysis, explicit dynamics etc. Solidworks and Ansys Workbench have been used as the tools for the simulation. Our aim was to design and fabricate a vehicle which is light weight (<200Kgs), easily maneuverable in harsh driving conditions and also scores high in affordability and maintenance.This report also contains the design consideration of the chassis, steering, suspension, braking, powertrain. Simulation results of components like hubs, knuckles, A-Arms, chassis are done with special focus on modelling based on real time forces and behaviors. MATLAB Simulink models are used and explained for the suspension model.The vehicle was fabricated in-house using various fabrication methods of TIG Welding, Vertical CNC machines etc. The strength tests for the specimens of welding were checked for the safety of the chassis. The vehicle was tested on tracks for braking, steering and acceleration and further modifications were made in the design to incorporate the iterations.
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Design Analysis and Development of High-Speed Rotating Fatigue Testing with Integrated by Twisting Test

Avinash Prakash Barve, Rahul Jangam, Adm Aman Soni, Pravin Pandagre, Hardik Bhautkar, Bhushan Chapke, Shantanu Bankar, Faisal Hussain, Adm Paresh Setiya
  • Technical Paper
  • 2019-28-0053
Published 2019-10-11 by SAE International in United States
The fatigue testing machine mostly used for industrial or laboratory applications are limited to performing single fatigue tests with high leading cost. In the present paper the experimental setup of the traditional fatigue testing machine is integrated with torsional test, to experimentally study the effect of fluctuating stresses on the material under service. In contradiction to earlier machines, the machine herein developed provides uniform bending and twisting moment distribution along the length of the test specimen. The machine performs fatigue test and torsional test, which provides the extreme force needed to understand the properties and behavior of materials. The machine consists of an electric motor to provide the required torque and two circular arms with adjustable chucks to fit test samples of various sizes. The machine provides computerized data for failed samples with data pertaining to each sample. The experimental model is designed and fabricated to match our customers unique test objective. Fatigue failures are reported 75% of documented materials failure and occur catastrophically. Fatigue life can be tested on loading conditions and it is…
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Systematic Work Flow for Fatigue Life Prediction of Automotive Components

Mahindra & Mahindra, Ltd.-Nitin Kumar Khanna, Baskar Anthonysamy, Krishna Shettipally, Manohar Kalal
  • Technical Paper
  • 2019-28-0021
Published 2019-10-11 by SAE International in United States
Fatigue life estimation of automotive components is a critical requirement for product design and development. Automotive companies are under tremendous pressure to launch new vehicles within short duration because of customer’s changing preferences. There is a necessity to have a comprehensive virtual simulation and robust validation process to evaluate durability of vehicle as per customer usage. Test track and field test are two of the most time-consuming activities, so there is a need of simulation process to substitute these requirements. This paper summarizes the overall process of Accelerated Durability Test with measured road loads. Based on category of vehicle, type road profiles and the customer usage pattern, the wheel forces, strains and acceleration are measured which is used to derive the equivalent duty cycles on proving ground. The wheel force transducers (WFT) are used to derive loads for fatigue life estimation. A full vehicle model is prepared in ADAMS CAR and validated through Physical testing. The loads on suspension hard points extracted from the validated MBD model. These loads at various hardpoint locations, are used…
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Critical Wear Assessment of AA8011/Hybrid Metal Matrix Composites with Surface Amendment Using Friction Stir Process

Sri Krishna College of Engg. and Tech.-Soundararajan Ranganathan, Shri Vignesh Ramachandran, Ramprakash Palanivelu, Saravanakumar Ramasamy
  • Technical Paper
  • 2019-28-0096
Published 2019-10-11 by SAE International in United States
Friction Stir Process (FSP) was employed for surface modification of steel, titanium, aluminum and magnesium-based alloy has been significantly revised through the last decade. Friction Stir Process can improve surface properties such as hardness, abrasion resistance, ductility, strength, fatigue life, corrosion resistance and formability without upsetting the bulk properties of the material. The aluminum alloy having low ductility and softness characteristics are restricted because of their poor tribological properties. Preliminary studies reveal that, an ideal circumstance is to improve the aluminum alloy material life cycles by the way of strengthening the surface layer which can be modified through reinforcing nanoparticles through FSP. The main objective of the study is to improve the surface properties of AA8011 by adding nanoparticles such as SMA and silicon nitrate (Si3N4) through friction stir process. By the way, this experiment was carried out to obtain three set of samples like virgin AA8011, AA8011 with shape memory alloy and AA8011 along with shape memory alloy and silicon nitride during FSP under optimal process parametric condition. The nanoparticles distribution was improved after…
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Tensile and Fatigue Behavior of Shallow Cryogenically Treated EN19 Alloy Steel

BSACIST-Loganathan Sekar, Tamil Arasan
SRM Institute of Science and Technology-Rajendran Raj
  • Technical Paper
  • 2019-28-0100
Published 2019-10-11 by SAE International in United States
Tensile and axial fatigue tests were conducted on shallow cryogenically treated EN19 medium carbon alloy steel to investigate its mechanical behavior. The test samples were conventionally heat treated then oil quenched at room temperature. Followed by the samples were kept for shallow cryogenic treatment to -80°C for 8 hours using liquid nitrogen. Then the samples were tempered in a muffle furnace to relieve the induced residual stresses. Tensile and axial fatigue test were carried out on both treated and non-treated samples to measure its tensile strength and fatigue behavior respectively. Microscopic examination also had done to compare the effect of shallow cryogenic treatment on its microstructure. The results exposed that there is an increase in the tensile strength and reduction in fatigue life of shallow cryogenically treated samples over base metal and improved wear resistance.
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Influence of Retained Austenite on Fatigue Performance of Carburized Gears

Comstar Automotive Tech P Ltd.-Rajeshkumar Ramasamy, Seenuvas Sivathanu, Varatharaj Neelakandan, Thulasirajan Ganesan, Praveen Chakrapani Rao
  • Technical Paper
  • 2019-28-0102
Published 2019-10-11 by SAE International in United States
SAE 8620 and 20CrMo materials were subjected to carburizing process to obtain the identical hardened layer of HRC 61-64. The carburized surface and core properties of the materials were examined and characterized through optical microstructure to measure the presence of cementite carbides and Retained Austenite (RA). From the results, it was found that the SAE 8620 and 20CrMo materials have 10 % and 14% of RA respectively. Whereas, the core and case structure were free from network carbides. The fatigue test was conducted to correlate the RA and fatigue strength of the materials. It was revealed that material with lower RA has higher fatigue strength than material with higher RA. Higher amount of retained austenite leads to reduction in amount of martensitic and compressive residual stress attributed to lower the contact fatigue strength. Untransformed austenite is metastable and is transformed to untempered martensite, which causes brittleness to the component and leads to premature failure.
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How HMI displays impact operator productivity in industrial vehicles

SAE Truck & Off-Highway Engineering: October 2019

Markus Wallmyr, head of UX at CrossControl and a researcher with Mälardalen University, wrote this article for Truck & Off-Highway Engineering magazine.-Markus Wallmyr
  • Magazine Article
  • 19TOFHP10_11
Published 2019-10-01 by SAE International in United States

The latest research indicates that well-integrated HMI (human-machine interface) systems lead to more attentive users that better retain task-related information and stay focused for longer with less reported effort. These systems also fit into the wider development trends in off-highway machines that affect operator fatigue in day-to-day tasks.

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Cab air quality: A CRITICAL COMPONENT OF OPERATOR COMFORT

SAE Truck & Off-Highway Engineering: October 2019

Jeff Moredock
  • Magazine Article
  • 19TOFHP10_04
Published 2019-10-01 by SAE International in United States

Focus on defining cab air quality, measuring it, and designing the needed performance into cabin designs and HVAC systems is intensifying.

Review the design specs for any new haul truck, excavator, dozer or other off-road machine, and you're not likely to find requirements related to cab air quality-yet. However, standards are changing and the need to optimize cab enclosure environments for air quality will grow.

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