scholarly journals Baking Effect on Desorption of Diffusible Hydrogen and Hydrogen Embrittlement on Hot-Stamped Boron Martensitic Steel

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 636 ◽  
Author(s):  
Hye-Jin Kim ◽  
Hyeong-Kwon Park ◽  
Chang-Wook Lee ◽  
Byung-Gil Yoo ◽  
Hyun-Yeong Jung
Keyword(s):  
Martensitic Steel ◽  
Hot Stamping ◽  
Fuel Efficiency ◽  
Thermal Desorption Spectroscopy ◽  
Martensitic Steels ◽  
Diffusible Hydrogen ◽  
Hydrogen Flow ◽  
High Fuel Efficiency ◽  
Delayed Cracking ◽  
Coated Surfaces

Recently, hot stamping technology has been increasingly used in automotive structural parts with ultrahigh strength to meet the standards of both high fuel efficiency and crashworthiness. However, one issue of concern regarding these martensitic steels, which are fabricated using a hot stamping procedure, is that the steel is highly vulnerable to hydrogen delayed cracking caused by the diffusible hydrogen flow through the surface reaction of the coating in a furnace atmosphere. One way to make progress in understanding hydrogen delayed fractures is to elucidate an interaction for desorption with diffusible hydrogen behavior. The role of diffusible hydrogen on delayed fractures was studied for different baking times and temperatures in a range of automotive processes for hot-stamped martensitic steel with aluminum- and silicon-coated surfaces. It was clear that the release of diffusible hydrogen is effective at higher temperatures and longer times, making the steel less susceptible to hydrogen delayed fractures. Using thermal desorption spectroscopy, the phenomenon of the hydrogen delayed fracture was attributed to reversible hydrogen in microstructure sites with low trapping energy.

Martensitic Automotive Steel Sheet - Fundamentals and Metallurgical Optimization Strategies

2014 ◽  
Vol 1063 ◽  
pp. 130-142 ◽  
Author(s):  
Hardy Mohrbacher
Keyword(s):  
Steel Sheet ◽  
Hot Stamping ◽  
Sheet Steel ◽  
Boundary Segregation ◽  
Alloying Elements ◽  
Processing Route ◽  
Martensitic Steels ◽  
Austenite Grain Size ◽  
Cold Forming ◽  
Delayed Cracking

Martensitic sheet steel is increasingly being used in advanced car body construction, especially in areas where high crash loads are expected. Using such steels appropriately the weight of individual components can be reduced by up to 20 percent. Martensitic steel sheet is commercially available in the strength range of 1200 to 1900 MPa, either as cold forming or hot stamping grade. Whereas the strength of such martensitic steels is practically only a function of the carbon content, other properties such as ductility, toughness, bendability and delayed cracking resistance are severely influenced by other alloying elements and the particular thermal processing route. The paper discusses the influence of various key-alloying elements such as Nb, Mo and B on these properties and suggests routes to optimize the steel’s behavior with respect to the manufacturing and application related aspects.Keywords Martensite, prior austenite grain size, delayed cracking, grain boundary segregation, hydrogen trapping, niobium, molybdenum

Hydrogen Transport in 34CrMo4 Martensitic Steel: Influence of Microstructural Defects on H Diffusion

2012 ◽  
Vol 323-325 ◽  
pp. 485-490 ◽  
Author(s):  
L. Moli-Sanchez ◽  
F. Martin ◽  
E. Leunis ◽  
J. Chêne ◽  
M. Wery
Keyword(s):  
Diffusion Coefficient ◽  
Room Temperature ◽  
Martensitic Steel ◽  
Hydrogen Trapping ◽  
Martensitic Steels ◽  
Hydrogen Diffusivity ◽  
Apparent Diffusion ◽  
Quenched Steel ◽  
Set Up ◽  
Permeation Test

The electrochemical permeation technique was used to evaluate the effect of the microstructure on hydrogen diffusivity and hydrogen trapping at room temperature in martensitic steels. A detailed study of the electrochemical permeation technique was first performed in order to identify the boundary conditions of a permeation test in the selected experimental set-up. The validity of the apparent diffusion coefficient derived from this test is also discussed. A 34CrMo4 quenched steel has been selected and designed at three tempering temperatures (200°C, 540°C and 680°C) in order to obtain three different microstructures. According to permeation measurements, H diffusion strongly depends on the microstructure. The material tempered at 540°C exhibits the smallest diffusion coefficient and the largest fraction of reversible traps at room temperature.

Fabrication and Characterization of Bulk Nanocrystalline Layer in Steel and Aluminum Alloys Formed by Shot Peening

2009 ◽  
Author(s):  
R. Waikar ◽  
Y. B. Guo ◽  
Keith A. Woodbury
Keyword(s):  
Aluminum Alloys ◽  
Shot Peening ◽  
Martensitic Steel ◽  
Bulk Material ◽  
Lower Surface ◽  
Martensitic Steels ◽  
Cross Sectional ◽  
Bulk Nanocrystalline ◽  
Nanocrystalline Layer

The formation of bulk nanocrystalline (NC) layers in AISI 1075 pearlitic and martensitic steels and aluminum alloys 6061-T6 and 7075 using air blast shot peening was studied. The cross-sectional microstructure of the samples showed a gradual reduction of the grain size near the surface. The NC layers were characterized using optical and scanning electron microscopy and nanohardness measurements. 2D surface topography of the top surface was also carried out. The roughness of the peened surfaces depends on sample hardness. The hardened AISI 1075 martensitic steel had lower surface roughness value. NC layers of 5 to 15 μm thickness were observed in the steels whereas the aluminum alloys 6061 and 7075 yielded NC layers up to 20 to 25 μm thick. The measured nanohardness in the NC layers confirmed the higher hardness of the NC layer compared with the bulk material.

scholarly journals HISTORICAL REVIEW OF DESIGN DEVELOPMENT OF MOTOR CAR GEARBOXES

2017 ◽  
Vol 2017 (1) ◽  
pp. 125-132
Author(s):  
Владимир Кучкаров ◽  
Vladimir Kuchkarov ◽  
Дмитрий Демидов ◽  
Dmitriy Demidov
Keyword(s):  
Power Flow ◽  
Main Part ◽  
Fuel Efficiency ◽  
Historical Review ◽  
Main Task ◽  
Design Development ◽  
High Fuel Efficiency ◽  
Definition Of ◽  
Absence Of Power

The paper reports the review in the development of motor car gearbox design. The main task consists in the detection of the reasons for changes in gearbox design for the definition of the field for gearbox substantiated application in motor car design. In the main part the advantages and shortcomings of manual, automated, infinitely variable and automatic gearboxes are under consideration. There are shown and analyzed functional diagrams of gearbox designs considered. In the conclusion it is pointed out that the most promising design of a gearbox is a robot gearbox with two clutches allowing the assurance of the absence of power flow break; the smoothness of gear shifts and smoothness of motion; comfort of control; high fuel efficiency; high tractiondynamic characteristics.

Hot Stamped Aluminium for Crash-Resistant Automobile Safety Cage Applications

2021 ◽  
Vol 1016 ◽  
pp. 445-452
Author(s):  
Jaume Pujante ◽  
David Frómeta ◽  
Eduard Garcia-Llamas ◽  
Maria Gimenez ◽  
Daniel Casellas
Keyword(s):  
Cycle Time ◽  
High Performance ◽  
Hot Stamping ◽  
Sheet Steel ◽  
Alloy Sheet ◽  
Process Window ◽  
Martensitic Steels ◽  
Press Hardening ◽  
Automobile Safety ◽  
Shape Complexity

Hot stamping, also known as press hardening in the context of sheet steel, has steadily gained relevance in the automotive industry, starting off as a specialist application and turning into a staple technique in the production of safety cage products in little more than a decade. However, despite the weight reduction offered by martensitic steels, further improvement could be obtained by substituting these components by high-performance aluminium. In this regard, the very same process of hot stamping could be employed to attain the required combination of shape complexity and mechanical properties at a reasonable cost for mass-market application, if the limitations imposed by cycle time and process window could be overcome. In this work, the feasibility of hot stamping of 6000-series aluminium alloy sheet is studied, first in dilatometry experiments and later in semi-industrial conditions in a pilot facility. A cycle time shortening strategy is employed, and compared to the conventional thermal cycle in terms of implementation and obtained results. In addition to basic characterization, aluminium thus processed is studied in terms of fracture toughness, in order to obtain data relevant to crashworthiness that can be readily compared with alternative materials.

Evaluation of adhesive failure cases of L joint structures under tensile loading

2018 ◽  
Vol 32 (19) ◽  
pp. 1840058
Author(s):  
Do-Hoon Shin ◽  
Dong-Keun Hyun ◽  
Yun-Hae Kim
Keyword(s):  
Low Cost ◽  
Fuel Efficiency ◽  
Tensile Loading ◽  
Failure Strength ◽  
Adhesive Failure ◽  
Manufacturing Method ◽  
High Fuel Efficiency ◽  
Wide Range ◽  
Temperature Time ◽  
Secondary Bonding

In aerospace, aircraft weight is one of the important factors essential for long range and high fuel efficiency. Instead of fastening, bonding methods like co-curing, co-bonding and secondary bonding are used on the aircraft parts. Secondary bonding was developed for integrated parts because of easy handling, less defect ratio and low cost. During manufacturing, the integrated parts using secondary bonding, bonding strength can show a wide range of failure strengths. Due to inconstant failure strength, the design value can be dropped and reinforcement methods should be applied. To avoid over-designing and to get a constant value for failure, the adhesive failure cases are studied in this project. In this study, L joining composite parts are investigated under tensile loading. Different conditions are tested to select a suitable manufacturing method for secondary bonding methods. From the experimental results, the secondary bonding was sensitive at exposed temperature/time and shape conditions of the fillet. The results show that the failure strength depends on the shape of fillet and exposed time for curing.

Estimation of Lateral/Directional Static Stability Characteristics of a Turboprop Aircraft at one Engine Inoperative Condition

2016 ◽  
Vol 842 ◽  
pp. 208-216 ◽  
Author(s):  
Ratna Ayu Wandini ◽  
Taufiq Mulyanto ◽  
Hari Muhammad
Keyword(s):  
Short Distance ◽  
Fuel Efficiency ◽  
Aircraft Design ◽  
Static Stability ◽  
Slip Angle ◽  
High Fuel Efficiency ◽  
Stability And Control ◽  
Conceptual Design Phase ◽  
The Stability ◽  
And Control

Twin engines turboprop aircraft provides the most beneficial solution to meet the needs of short distance flight due to high fuel efficiency [1]. One of the emergency conditions which has to be considered for this type of the aircraft when one engine is out operating or one engine inoperative because it involves the safety of flight. Furthermore, a safe flight with one engine inoperative is regulated by FAR/CASR Part 25 and has to be complied during certification .Stability and control characteristics of a turboprop aircraft will change significantly if one engine inoperative condition occurs during cruise phase. The rudder and/or aileron deflections to counter the yawing and rolling moments due to the thrust of the operating engine must satisfy. Recognizing the importance of that consideration, this research will estimate the stability and control characteristics of lateral/directional in one engine inoperative condition on new turboprop 80-pax aircraft design concept.This paper presents procedures for estimating the lateral/directional static stability characteristics of a 80-pax turboprop aircraft during the conceptual design phase. The size of the rudder and aileron have to be iterated to fullfil the requirements at a condition when one engine is not operative. The rudder and the aileron deflections are estimated as functions of airspeed, roll angle, side slip angle and thrust setting. It will be shown in this paper that the required rudder deflection as well as aileron deflection can satisfy to balance the forces and moments due to asymmetrical thrust condition and the minimum control speed of the aircraft can be maintained as well.

Analysis of Compression-Ignition Engine Design Concerning Engine Structural Loading Capacity

2004 ◽  
Author(s):  
Gong Chen
Keyword(s):  
Thermal Loading ◽  
Fuel Injection ◽  
Fuel Efficiency ◽  
Design Parameters ◽  
Analytical Prediction ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Exhaust Temperature ◽  
High Fuel Efficiency ◽  
Structural Loading

Present-day high-power compression-ignition engines are required in design not only to achieve a targeted high fuel efficiency, but also to meet regulated exhaust emissions standards. This paper investigates the effects of the in-cylinder combustion related design parameters, including cylinder compression ratio, fuel injection-start timing, and the amount of cylinder air charge, on engine performances and emissions as the engine structure-loading allowance is specified. Thereby the determination of those parameters to optimize the engine overall performances without exceeding the allowances in engine mechanical and thermal loading can be achieved. An enhanced understanding of those design parameters associated with the engine structural loading parameters, such as the cylinder peak firing pressure and exhaust temperature, is studied. The analytical prediction of the trade-off between those parameters with peak firing pressure contained is modeled and developed.

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