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Journal Article

A Review on Electromagnetic Sheet Metal Forming of Continuum Sheet Metals

2019-05-29
Abstract Electromagnetic forming (EMF) is a high-speed impulse forming process developed during the 1950s and 1960s to acquire shapes from sheet metal that could not be obtained using conventional forming techniques. In order to attain required deformation, EMF process applies high Lorentz force for a very short duration of time. Due to the ability to form aluminum and other low-formability materials, the use of EMF of sheet metal for automobile parts has been rising in recent years. This review gives an inclusive survey of historical progress in EMF of continuum sheet metals. Also, the EMF is reviewed based on analytical approach, finite element method (FEM) simulation-based approach and experimental approach, on formability of the metals.
Journal Article

A Study on Lightweight Design of Automotive Front Rails Using Tailored Blanks by Nonlinear Structural Optimization

2018-11-07
Abstract Tailored blanks offer great lightweighting opportunities for automotive industry and were applied on the front rails of a sedan in this research. To achieve the most efficient material usage, all the front rail parts were tailored into multiple sheets with the gauge of each sheet defined as a design variable for optimization. The equivalent static loads (ESL) method was adopted for linear optimization and the Insurance Institute for Highway Safety (IIHS) moderate overlap frontal crash as the nonlinear analysis load case. The torsion and bending stiffness of the sedan body in white (BIW) were set as design constraints. The occupant compartment intrusion in IIHS moderate overlap front crash was set as design objective to be minimized. The optimal thickness configuration for the tailored front rail designs was obtained through ESL optimization for multiple mass saving targets.
Journal Article

Aerodynamic Analysis of Cooling Airflow for Different Front-End Designs of a Heavy-Duty Cab-Over-Engine Truck

2018-04-07
Abstract Improving the aerodynamics of heavy trucks is an important consideration in the strive for more energy-efficient vehicles. Cooling drag is one part of the total aerodynamic resistance acting on a vehicle, which arises as a consequence of air flowing through the grille area, the heat exchangers, and the irregular under-hood area. Today cooling packages of heavy trucks are dimensioned for a critical cooling case, typically when the vehicle is driving fully laden, at low speed up a steep hill. However, for long-haul trucks, mostly operating at highway speeds on mostly level roads, it may not be necessary to have all the cooling airflow from an open-grille configuration. It can therefore be desirable for fuel consumption purposes, to shut off the entire cooling airflow, or a portion of it, under certain driving conditions dictated by the cooling demands. In Europe, most trucks operating on the roads are of cab-over-engine type, as a consequence of the length legislations present.
Journal Article

Artificial Lightning Tests on Metal and CFRP Automotive Bodies: A Comparative Study

2019-01-07
Abstract Carbon fiber reinforced plastic (CFRP) has been used in automobiles as well as airplanes. Because of its light weight and high strength, CFRP is a good choice for making vehicle bodies lighter, which would improve fuel economy. Conventional metal bodies provide a convenient body return for electric wiring and offer good shielding against electromagnetic fields. Although CFRP is a conductor, its conductivity is much lower than that of metals. Therefore, CFRP bodies are usually not useful for electric wiring. In thunderstorms, an automotive body is considered to be a Faraday cage that protects the vehicle’s occupants from the potential harms of lightning. Before CFRP becomes widely applied to automotive bodies, its electric and electromagnetic properties need to be investigated in order to determine whether it also works as a Faraday cage against lightning. In this article, CFRP and metal body vehicles were tested under artificial lightning.
Journal Article

CFD Windshield Deicing Simulations for Commercial Vehicle Applications

2018-04-06
Abstract Windshield deicing performance is a key metric for HVAC system development and optimization within the sphere of commercial vehicle design. The primary physical parameters that drive this metric are pressure drops in the HVAC ducting, flow rate of the air through the system, and the transient vent temperature rise affected by engine coolant warm-up. However, many design engineers also have to take underhood and instrument panel (IP) space constraints into consideration while trying to optimize a new HVAC system design. This study leverages historical deicing simulation methodologies in conjunction with modern computational horsepower so as to optimize the HVAC ductwork in the studied commercial truck at the beginning of the design phase. By iterating on a design in the computational domain under steady-state and transient flow and thermal conditions, a robust HVAC system design can be created even prior to the prototyping stage of development.
Journal Article

Carbon Fiber/Epoxy Mold with Embedded Carbon Fiber Resistor Heater - Case Study

2018-04-07
Abstract The paper presents a complete description of the design and manufacturing of a Carbon Fiber/epoxy mold with an embedded Carbon Fiber resistor heater, and the mold performances in terms of its surface temperature distribution and thermal deformations resulting from the heating. The mold was designed for manufacturing aileron skins from Vacuum Bag Only prepreg cured at 135°C. The glass transition temperature of the used resin-hardener system was about 175°C. To ensure homogenous temperature of the mold working surface in the course of curing, the Carbon Fiber heater was embedded in a layer of a highly heat-conductive cristobalite/epoxy composite, forming the core of the mold shell. Because the cristobalite/epoxy composite displayed much higher thermal expansion than CF/epoxy did, thermal stresses could arise due to this discrepancy in the course of heating.
Journal Article

Comparison of Various Drag Reduction Devices and Their Aerodynamic Effects on the DrivAer Model

2018-07-05
Abstract In this study, two types of drag reduction devices (a horizontal plate, and a vertical plate) are used to weaken the downwash of the upper flow and c-pillar vortex of the DrivAer notchback model driving at high speed (140 km/h). By analyzing and comparing 15 cases in total, the aerodynamic drag reduction mechanism can be used in the development of vehicles. First, various CFD simulation conditions of a baseline model were compared to determine the analysis condition that efficiently calculates the correct aerodynamic drag. The vertical plate and horizontal plate applied in the path of the c-pillar vortex and downwash suppressed vortex development and induced rapid dissipation. As a result, the application of a 50-mm wedge-shaped vertical plate to the trunk weakened the vortex and reduced the drag by 3.3% by preventing the side flow from entering the trunk top.
Journal Article

Design of High-Lift Airfoil for Formula Student Race Car

2018-12-05
Abstract A two-dimensional model of three elements, high-lift airfoil, was designed at a Reynolds number of ?????? using computational fluid dynamics (CFD) to generate downforce with good lift-to-drag efficiency for a formula student open-wheel race car basing on the nominal track speeds. The numerical solver uses the Reynolds-averaged Navier-Stokes (RANS) equation model coupled with the Langtry-Menter four-equation transition shear stress transport (SST) turbulence model. Such model adds two further equations to the ?? − ?? SST model resulting in an accurate prediction for the amount of flow separation due to adverse pressure gradient in low Reynolds number flow. The ?? − ?? SST model includes the transport effects into the eddy-viscosity formulation, whereas the two equations of transition momentum thickness Reynolds number and intermittency should further consider transition effects at low Reynolds number.
Journal Article

Determination of Influence of Parameters on Undercarriage Shock Absorber

2018-12-31
Abstract The simple oleo pneumatic (shock absorber) model was developed using the available computational fluid dynamics (CFD) program to understand how various parameters influence the performance of the undercarriage shock absorber. The study is divided into two parts: first part is focused on the influence of orifice geometry and the second part of the study is focused on the other parameters including chamber geometry. Both the studies are carried out using design of experiments (DOE) for the same output characteristics (response). In this study, the impacts on the flow behavior due to the orifice shapes are also studied. The results and the other outcomes are shown in the form of DOE parameters such as main effect plots and interaction plots.
Journal Article

Effect of Welding Parameters on the Microstructure and Tensile Properties of Friction Stir-Welded DP600 Steel

2019-07-02
Abstract The aim of this study was to investigate the effect of friction stir welding (FSW) parameters on the microstructure and tensile properties of dual-phase (DP) steels. In this regard, DP600 steel sheets were joined using FSW under different tool rotational (ω) and transverse speeds (v). Optical microstructure of the stir zone exhibited a mixture of bainite, Widmanstatten ferrite, grain boundary ferrite, and ferrite-carbide (FC) aggregate, which resulted in a hardness increase compared to the base metal (BM). The fraction of bainite and Widmanstatten ferrite in the stir zone increased with increasing the welding heat input. Formation of a softened zone in the subcritical area of the heat-affected zone (HAZ) resulted in the reduction of ultimate tensile strength and total elongation compared to those for the BM, while the yield strength was only marginally affected.
Journal Article

Electrifying Long-Haul Freight - Part I: Review of Drag, Rolling Resistance, and Weight Reduction Potential

2019-10-01
Abstract Electric heavy-duty tractor-trailers (EHDTT) offer an important option to reduce greenhouse gases (GHG) for the transportation sector. However, to increase the range of the EHDTT, this effort investigates critical vehicle design features that demonstrate a gain in overall freight efficiency of the vehicle. Specifically, factors affecting aerodynamics, rolling resistance, and gross vehicle weight are essential to arrive at practical input parameters for a comprehensive numerical model of the EHDTT, developed by the authors in a subsequent paper. For example, drag reduction devices like skirts, deturbulators, vortex generators, covers, and other commercially available apparatuses result in an aggregated coefficient of drag of 0.367. Furthermore, a mixed utilization of single-wide tires and dual tires allows for an optimized trade-off between low rolling resistance tires, traction, and durability.
Journal Article

Erosion Wear Response of Linz-Donawitz Slag Coatings: Parametric Appraisal and Prediction Using Imperialist Competitive Algorithm and Neural Computation

2019-03-14
Abstract Slag, generated from basic oxygen furnace (BOF) or Linz-Donawitz (LD) converter, is one of the recyclable wastes in an integrated steel plant. The present work aims at utilization of waste LD slag to develop surface coatings by plasma spraying technique. This study reveals that LD slag can be gainfully used as a cost-effective wear-resistant coating material. A prediction model based on an artificial neural network (ANN) is also proposed to predict the erosion performance of these coatings. The 2.27% error shows that ANN successfully predicts the erosion wear rate of the coatings both within and beyond the experimental domain. In addition to it, a novel optimization algorithm called imperialist competitive algorithm (ICA) is used to obtain minimum erosion wear rate of 12.12 mg/kg.
Journal Article

Evaluation of Weldability and Mechanical Properties in Resistance Spot Welding of Ultrahigh-Strength TRIP1100 Steel

2018-12-14
Abstract To use steel in the automotive industry, it is essential to characterize its weldability and weldable current range. The resistance spot welding of ultrahigh-strength transformation-induced plasticity steel (TRIP1100 steel), which is a candidate for application in an autobody, is studied here. Identifying the weld lobe and the best welding parameters and studying the microstructure and mechanical properties of the spot welds of TRIP steel were done using metallurgical techniques, tensile-shear and cross-tension tests, and fractography and microhardness testing. A partial fracture analysis (stepwise tensile test) showed a crack initiated at the tip of the notch. The best range for welding current was found to be 10-12 kA. The diameter of the weld nugget increased up to 5√t; however, it was found that at least 15% increase in the diameter of the weld nugget can result in a more favorable failure. The ductility ratio was found to be less than 0.5 for ultrahigh-strength steel.
Journal Article

Fracture-Splitting Processing Performance Study and Comparison of the C70S6 and 36MnVS4 Connecting Rods

2018-08-08
Abstract 36MnVS4 is a new connecting-rod fracture-splitting material. To explore why it has a high fracture- splitting defective index, this article simulated the fracture-splitting process of connecting rods. Comparing 36MnVS4 with C70S6, this article analyzed the stress-strain state of the groove roots, the position of crack initiation, the plastic deformation distribution of the fracture surface, and the splitting force changes in fracture splitting process. Results show that the crack initiation position of the 36MnVS4 connecting rod is relatively more scattered and random, and the crack starting point of the C70S6 connecting rod is more unique. Compared with the C70S6 connecting rod, the 36MnVS4 connecting rod has an earlier crack initiation time and smaller fracture-splitting force. Therefore, the 36MnVS4 has higher gap sensitivity and its fracture surface is more prone to tear.
Journal Article

Improving Hole Expansion Ratio by Parameter Adjustment in Abrasive Water Jet Operations for DP800

2018-09-17
Abstract The use of Abrasive Water Jet (AWJ) cutting technology can improve the edge stretchability in sheet metal forming. The advances in technology have allowed significant increases in working speeds and pressures, reducing the AWJ operation cost. The main objective of this work was to determine the effect of selected AWJ cutting parameters on the Hole Expansion Ratio (HER) for a DP800 (Dual-Phase) Advanced High-Strength Steel (AHSS) with s0 = 1.2 mm by using a fractional factorial design of experiments for the Hole Expansion Tests (HET). Additionally, the surface roughness and residual stresses were measured on the holes looking for a possible relation between them and the measured HER. A deep drawing quality steel DC06 with s0 = 1.0 mm was used for reference. The fracture occurrence was captured by high-speed cameras and by Acoustic Emissions (AE) in order to compare both methods.
Journal Article

Industrial Framework for Identification and Verification of Hot Spots in Automotive Composite Structures

2019-05-16
Abstract In this article, a framework for efficient strength analysis of large and complex automotive composite structures is presented. This article focuses on processes and methods that are compliant with common practice in the automotive industry. The proposed framework uses efficient shell models for identification of hot spots, automated remodelling and analysis of found hot spots with high-fidelity models and finally an automated way of post-processing the detailed models. The process is developed to allow verification of a large number of load cases in large models and still consider all potential failure modes. The process is focused on laminated composite primary structures. This article highlights the challenges and tools for setting up this framework.
Journal Article

Investigation of Passive Porosity as a Means for Bluff-Body Drag Reduction

2018-03-16
Abstract An investigation into the capability of passive porosity to reduce the drag of a bluff-body is presented. This initial work involves integrating varying degrees of porosity into the side and back faces of a small-scale model to determine optimum conditions for maximum drag reduction. Both force and pressure measurements at differing degrees of model yaw are presented, with the conditions for optimum performance, identified. At a length-based Reynolds number of 2.3 × 106, results showed a maximum drag reduction of 12% at zero yaw when the ratio of the open area on the back face relative to the side faces was between two and four. For all non-zero yaw angles tested, this ratio reduced to approximately two, with the drag benefit reducing to 6% at 10.5 degrees. From a supplementary theoretical analysis, calculated optimum bleed rate into the base for maximum drag reduction, also showed reasonable agreement to other results reported previously.
Journal Article

Investigation of Residual Stresses in Cold-Formed Steel Sections with Nonlinear Strain-Hardened Material Model

2018-09-17
Abstract In this article, forming residual stresses in cold-formed small-radius corner sections are analytically predicted with the consideration of the shift in the neutral axis and the nonlinear strain-hardened material model. The predicted forming stress results in the transverse direction show a trend of increased compressive residual stress in the outer surface and reduced tensile residual stress in the inner surface as the corner radius-to-thickness ratio increases in small-radius bends. In the longitudinal direction, there is no significant change in the residual stress values observed in the inner and outer surfaces with respect to an increase in corner radius-to-thickness ratios. But a considerable decrease in compressive residual stress and an increase in tensile stress values are observed in the midsection areas with an increase in the corner radius-to-thickness ratio.
Journal Article

Low Cycle Fatigue and Ratcheting Behavior of SA333 Gr-6 Steel at 300°C Temperature

2019-01-23
Abstract The objective of this investigation is to study the cyclic deformation behavior of SA333 Gr-6 C-Mn steel at 300°C. Low cycle fatigue tests were carried out at total strain amplitude between ±0.35 and ±1.25% at a constant strain rate of 1 × 10−3 s−1. Ratcheting tests were conducted at a various combination of mean stress and stress amplitude at a constant stress rate of 115 MPa s−1. The material SA333 Gr-6 steel exhibits cyclic hardening throughout its fatigue life. The material shows non-Masing behavior and deviation (δσo ) from Masing behavior increase with an increase of strain amplitude. Ratcheting strain accumulation increases, whereas ratcheting life decreases with an increase in mean stress or stress amplitude. With an increase in mean stress and stress amplitude, ratcheting rate also increases. The material shows hardening characteristic due to dynamic strain aging (DSA) phenomena.
Journal Article

Metallurgical Approach for Improving Life and Brinell Resistance in Wheel Hub Units

2017-09-17
Abstract Raceway Brinell damage is one major cause of wheel bearing (hub unit) noise during driving. Original Equipment Manufacturer (OEM) customers have asked continuously for its improvement to the wheel bearing supply base. Generally, raceway Brinelling in a wheel hub unit is a consequence of metallic yielding from high external loading in a severe environment usually involving a side impact to the wheel and tire. Thus, increasing the yielding strength of steel can lead to higher resistance to Brinell damage. Both the outer ring and hub based on Generation 3 (Gen. 3) wheel unit are typically manufactured using by AISI 1055 bearing quality steel (BQS); these components undergo controlled cooling to establish the core properties then case hardening via induction hardening (IH). This paper presents a modified grade of steel and its IH design that targets longer life and improves Brinell resistance developed by ILJIN AMRC (Advanced Materials Research Center).
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