Browse Topic: Stamping

Items (882)
Combined with a modified Zener-Hollmon parameter, a recently proposed ductile failure criterion is further improved to predict the forming limit of boron steel at hot stamping temperatures. The ductile failure criterion takes into account the critical damage at localized necking or at fracture as a function of strain path and initial sheet thickness. The modified Zener-Hollomon parameter accounts for both effect of varying strain rate and temperature for Boron steel. Working FEM simulation, the capability of the ductile failure criterion is further demonstrated by predicting forming limit of a boron steel in an isothermal Nakajima dome test. Comparison shows the prediction matches quite well with the measurement.
Sheng, ZiQiangMallick, Pankaj
In sheet metal simulation, computation time is significantly influenced by the number of elements used to discretize the sheet blank, which covers the shape of forming tool geometry. Based on particle kinematics, motion of material point is modeled, and the concept of zero circumferential motion material line (ZML) is proposed. The slope ratio of material line (SRML) is proposed to quantify the circumferential deviation for determining the ZML. Based on the SRML, a method is developed to segment sheet blank and apply constraints. The method is demonstrated through forming simulation on a Hishida geometry. The proposed method, with its minimal to no circumferential motion along ZMLs, exhibits high level of accuracy retention while simultaneously impressively reducing computation time (up to 77%). This combination of efficiency and precision makes it a compelling approach for reducing simulation cost.
Sheng, ZiQiangAsimba, BrianCabral, Kleber
The initial powder used for the manufacturing of NdFeB permanent magnets is usually prepared through rapid cooling, either by melt spinning or strip casting. The powders produced by these two methods are suitable for different applications: while melt-spun powder is a good initial material for bonded and hot-deformed magnets, strip-cast powder is normally used for sintered magnets. To investigate the suitability of using strip-cast powder to manufacture hot-deformed magnets, NdFeB powder prepared by strip casting was hot pressed (without particle alignment) and compared with melt-spun powder prepared under the same conditions (700 °C, 45 MPa, 90 min). Although the processing parameters are the same (pressed in the same mold), the magnetic properties of the magnets made from the two powders are significantly different. Surprisingly, the magnet made from the strip-cast powder (after ball milling) shows comparable magnetic properties to those of isotropic magnets, with coercivity (HcJ) of
He, YouliangSong, ShaochangWalsh, DanBernier, FabriceMozharivskyj, YurijPeng, Philip
For electrical vehicle (EV) automotive body-in-white (BIW) structures, protection of passengers and battery in crash event becomes equally important. In addition to energy absorption, intrusion protection for battery and vehicle becomes extremely important and GPa advanced high strength steels (AHSS) including press hardened steels (PHS), DP/MP/CP/GEN3 steels have become material of choice for design for those components. Higher yield strength materials especially in 980/1180MPa MP and CP category are chosen for part design over conventional low yield strength DP. In this study, the forming characteristics including both global and local formability are evaluated and compared among 980 DP/MP grades. Formability test such as forming limit curve (FLC), true fracture strain, V bend, half dome, and hole expansion tests are conducted. Microstructure analysis to understand the effect of different grain structure and phases of DP/MP grades is also accomplished. A T-shape laboratory die trials
Shih, Hua-ChuPednekar, VasantShi, MingSingh, JatinderTedesco, SarahWu, Wei
This specification covers a magnetic nickel-iron alloy in the form of sheet and strip.
AMS E Carbon and Low Alloy Steels Committee
Hemming is an incremental joining technique used in the automotive industry, it involves bending the flange of an outer panel over an inner panel to join two sheet metal panels. Different hemming methods are available such as Press die hemming, Table-top hemming and Robot roller hemming. Robot roller hemming is superior to press hemming and tabletop hemming because of its ability to hem complex-shaped parts and is typically used in low-volume automotive production lines. For higher production volumes, such as 120 Jobs per Hour (JPH), press hem or tabletop hem is generally preferred. However, to achieve high-volume production from roller hemming method multi station setup is used. This static multi station setup can be configured into a Turntable setup. This new method eliminates the robot load and unload time at each station in the existing setup, resulting in a 40% increase in hemming robot utilization. Therefore, this process reduces the number of robots and the required floor space
Raju, GokulRoy, AmlanSahu, ShishirPalavelathan, Gowtham RajJagadeesh, NagireddiChava, Seshadri
The photochemical etching (PCE) process is distinguished by its capacity to fabricate metal parts with unparalleled accuracy. This process sidesteps the typical stresses and deformations linked to conventional metal-working, like stamping or laser cutting, which can compromise material integrity. Such fidelity is crucial in the manufacture of components for thermal management systems, where material integrity and component precision are non-negotiable for ensuring effective heat creation or dissipation. PCE’s ability to craft parts with smooth, burr-free edges and exact dimensions means heat management components work more effectively, bolstering the reliability and extending the service life of micro electronic devices.
Soft magnetic cores of electric motors and generators are normally manufactured by stamping individual circular laminates from non-oriented electrical steel (NOES) sheets and stacking them layer by layer to reach the required height. The traditional lamination method can only achieve the average performance of the NOES since the magnetization is in all the directions of the sheet plane. Although NOES is ideal to have isotropic magnetic properties in all the directions of the sheet plane, commercially available electrical steel sheets always show apparent anisotropy in the rotating magnetization directions lying in the sheet plane. The anisotropy in magnetic properties not only causes fluctuations in the rotating magnetic field, but also leads to oscillations in electromagnetic torque, and thus needs to be minimized. In this paper, a novel electrical steel lamination technique is developed, which takes the advantage of the inherent magnetic anisotropy of electrical steel sheets to
He, YouliangSebesta, DamirPodlesny, Maciej
During the vehicle lifecycle, customers are able to directly perceive the outer panel stiffness of vehicles in various environmental conditions. The outer panel stiffness is an important factor for customers to perceive the robustness of the vehicle. In the real test of outer panel stiffness after prototype production, evaluators manually press the outer panel in advance to identify vulnerable areas to be tested and evaluate the performance only in those area. However, when developing the outer panel stiffness performance using FEA (Finite Element Analysis) before releasing the drawing, it is not possible to filter out these areas, so the entire outer panel must be evaluated. This requires a significant amount of computing resources and manpower. In this study, an approach utilizing artificial intelligence was proposed to streamline the outer panel stiffness analysis and improve development reliability. A deep learning-based prediction technology was developed to predict force
Uhm, TaekyoungOh, Seunghyeok
Multiple experimental studies were performed on galling intiation for variety of tooling materials, coatings and surface treatments, sheet materials with various surface textures and lubrication. Majority of studies were performed for small number of samples in laboratory conditions. In this paper, the methodology of screening experiment using different combinations of tooling configurations and sheet material in the lab followed by the high volume small scale U-bend performed in the progressive die on the mechanical press is discussed. The experimental study was performed to understand the effect of the interface between the sheet metal and the die surface on sheet metal flow during stamping operations. Aluminum sheet AA5754 2.5mm thick was used in this experimentation. The sheet was tested in laboratory conditions by pulling between two flat insert with controllable clamping force and through the drawbead system with variable radii of the female bead. Comparing pulling forces during
Reinberg, NataliaMurray, RyanAscencio Barrera, SindiPineda Carranza, CristinaGolovashchenko, Sergey
The application of local advanced steels has challenges to overcome such as stampability requirements to meet manufacturing processes. Several technological alternatives have been studied to improve sheet steel formability and this work focuses on material selection. Dual Phase 800 steel has an important performance for structural parts involved in body-in-white (BIW) to reach durability and material impact resistance. On those alternatives references the coating application to reduce the friction coefficient and makes the formability process easier to mitigate drawing stamping issues. The study deals with DP800 formability analysis applied in automotive seats, mainly on anchorage components, searching for alternatives to a better material stampability and local availability with a lower cost. These tests approached formability simulations and FLD (Forming Limit Diagrams) to compare the imported DP800-Uncoated and the local DP800EG + Phosphate steels. Additional tests were made for
de Campos, Kauan MoreiraPiovatto, Roberto ReatoColosio, Marco A.
In the 1st generation Toyota "MIRAI" fuel cell stack, carbon protective surface coating is deposited after individual Ti bipolar plate being press-formed into the desired shape. Such a process has relatively low production speed, not ideal for large scale manufacturing. A new coating concept, consisting of a nanostructured composite layer of titanium oxide and carbon particles, was devised to enable the incorporation of both the surface treatment and the press processes into the roll-to-roll production line. The initial coating showed higher than expected contact resistance, of which the root cause was identified as nitrogen contamination during the annealing step that inhibited the formation of the composite film structure. Upon the implementation of a vacuum furnace chamber as the countermeasure, the issue was resolved, and the improved coating could meet all the requirements of productivity, conductivity, and durability for use in the newer generation of fuel cell stacks.
YAMASAKI, TakenoriIKEDA, KotaroSATO, Toshiki
In today’s Automotive world, there is NO need to advocate “Light weighting”. Government policies for carbon footprint reduction combined with high safety standards are driving OEMs to adopt advanced manufacturing technologies. Steel hot forming is selected as most preferred way to reduce weight as it is easy to adopt and commercially known. It had many advantages compare to conventional cold stamping of standard and high tensile steel. The process consists of heating blank to nearly 1000 °C and quenching it in tool to for martensitic structure. Higher strength up to 2000 MPa can be achieved by this process. There are many examples where part weight is reduced by 15 to 20 % by this method. But Steel hot forming has limitation as specific density of steel is still high. Thus, there is limitation to its weight reduction capability. For further reduction, OEMs have started exploring Aluminium hot forming. This process, similar to steel hot forming improves hardness of the part by series of
NIRGUDKAR, SACHIN SURESHMelotti PhD, Federico
Vacuum suction cups are used as transforming handles in stamping lines, which are essential in developing automation and mechanization. However, the vacuum suction cup will crack due to fatigue or long-term operation or installation angle, which directly affects production productivity and safety. The better design will help increase the cups' service life. If the location of stress concentration can be predicted, this can prevent the occurrence of cracks in advance and effectively increase the service life. However, the traditional strain measurement technology cannot meet the requirements of tracking large-field stains and precise point tracking simultaneously in the same area, especially for stacking or narrow parts of the suction cups. The application must allow multiple measurements of hidden component strain information in different fields of view, which would add cost. In this study, a unique multi-camera three-dimensional digital image correlation (3D-DIC) system was designed
Guo, BichengZheng, XiaowanFang, SiyuanYang, Lianxiang
Light weighting has been one of major driver in automotive industry for few decades. Today when automobile industry is in the transition from internal combustion engine to electric vehicles it becomes even more dominant driver. Many high strength or advanced high strength steels are used in different parts of automotive body for down-gauging and light weighting. BH 220 steel is used in automotive skin panels for its bake hardening property. BH220 provides excellent combination of formability during stamping process and dent resistance in skin panel parts post painting and baking cycle. This material uses CED oven temperature for baking and provide bake hardening effect (BH effect/BH Index) in parts due to increase in yield strength by 35-70 MPa. Current national and international standards specify requirement on BH Index at 170°C for 20 minutes with 2% pre-strain. In order to optimize paint shop CED oven baking temperature, study carried out to know baking temperature effect on BH
Jain, VikasMisal, SwapnaliPaliwal, LokeshSathaye, Asmita
Electrical steels are silicon alloyed steels that possess great magnetic properties, making them the ideal material choice for the stator and rotor cores of electric motors. They are typically comprised of laminated stacks of thin electrical steel sheets. An electric motor can reach high temperatures under a heavy load, and it is important to understand the combined effect of temperature and load on the electrical steel’s performance to ensure the long life and safety of electric vehicles. This study investigated the fatigue strength and failure behavior of a 0.27mm thick electrical steel sheet, where the samples were prepared by a stamping process. Stress-control fatigue tests were performed at both room temperature and 150°C. The S-N curve indicated a decrease in the fatigue strength of the samples at the elevated temperature compared to the room temperature by 15-25 MPa in the LCF and HCF regimes, respectively. Looking at the fracture surface, the room temperature samples at both
Gill, GurmeetBehravesh, BehzadSaha, DulalZhang, WenshengChen, JimLamonaca, GianniMills, MarieJahed, Hamid
Strict environmental regulations are driving the automotive industry toward electric vehicles as they offer zero emissions. A key component in electric vehicles is the electric motor, where the stator and rotor are manufactured from stacks of thin electrical steel sheets. The electrical steel sheets can be cut in different ways, and the cutting methods may significantly affect the fatigue strength of the component. It is important to understand the effect of the cutting processes on the fatigue properties of electrical steel to ensure there is no premature failure of the electric motor resulting from an improper cutting process. This investigation compared the effect of three different edge preparation methods (stamping, CNC machining, and waterjet cutting) on the fatigue performance of 0.27mm thick electrical steel sheets. To investigate the effect of the edge finish on fatigue behavior, surface roughness was measured for these different samples. It was determined that the CNC
Gill, GurmeetBehravesh, BehzadSaha, DulalZhang, WenshengChen, JimLamonaca, GianniMills, MarieJahed, Hamid
EV battery enclosures are a hotbed of subsystem design, materials innovation and vehicle integration. Whether you call them packs, boxes or trays, the structures that envelop and protect EV battery cells and their supporting electrical and thermal-management hardware are among the industry's top subsystem priorities. Optimizing the battery pack involves a host of manufacturing and material choices, mass and package tradeoffs, safety provisions and structural design/engineering challenges, OEM and supplier experts told SAE Media. “Do you want the battery pack bolted into the vehicle or integrated into the body structure?” asked Darren Womack, senior department manager, body and structures, at Magna's global R&D group. Hot stamping, cold stamping, roll-forming, hydroforming, casting and steel, aluminum, composites and thermoplastics - are all raising “lively discussions” in pack development, he noted at a recent meeting of analysts.
Brooke, Lindsay
Stamped components play an important role in supporting various sub-systems within a typical engine and transmission assembly. In some cases, the stamped components will not initially meet the design criteria, and material may need to be added to strengthen it. However, in other cases the component may be overdesigned, and there will be opportunities to reduce mass while still meeting all design criteria. In this latter case, multiple CAE simulations are often performed to enhance the component design by varying design parameters such as thickness, bend radius, material, etc., The conventional process will assess changes in one parameter at a time, while holding other parameters constant. Though this helps in meeting the design criteria, it is often very difficult to produce the best optimized design within the limited time span with this approach. With the aid of Altair-HyperMorph techniques, multiple design parameters can be varied simultaneously. Design of Experiments (DOE) analyses
S, SiddeshFreiman, DavidNayak, Swarnendu Bikash
An emerging challenge for the extrusion press industry is older hydraulics technology. Many presses continue using inefficient and unreliable hydraulic pumps.
In this paper, for the front wall of a certain automobile, the defects of drawing splits, excessive thinning and excessive springback in the sheet metal forming process are analyzed and predicted. The stamping process has been simulated. The influence of different technical parameters (blank holder force, stamping speed, die gap and friction coefficient) on the forming results was further investigated using the center composite experiment. Through preliminary finite element simulation, the main drawing defects and trimming springback were analyzed. The second-order response surface model was established to perform the multi-objective optimization design of the stamping process with a NGSA-II genetic algorithm. Based on the relevant simulation data, multiple springback compensations are performed on the die surface to reduce the final springback of the part to meet the requirements. Results have shown that through multi-objective optimization, the stamping dies development cycle is
Zeng, HaohanHuang, ZhaomingWang, TaoSun, HuimingWang, Liangmo
With the rising cost of fuels in addition to stricter emission standards, modern vehicles ought to be more fuel efficient. The best approach to increase fuel efficiency is to reduce the mass of vehicles. In order to produce light weight components for vehicles, topology optimization (TO) is now widely used by designers. However, the raw results obtained from TO cannot be manufactured directly and require significant reinterpretation to be able to be manufactured using traditional manufacturing processes. By considering the manufacturing process outside of TO, a sub-optimal design is obtained. The consideration of process specific manufacturing constraints within the TO ensures that a more optimal design will be produced. Previously the complex designs produced by TO have been a barrier to its implementation as the components cannot be produced without excessive costs. By coupling manufacturing constraints with TO more optimal designs can be obtained. Traditionally TO is done with a
Forward, CameronShah, VishrutKashanian, KiarashPamwar, ManishSangha, BalbirKim, Il Yong
The development of new components that have a structural commitment and still achieve mass reduction is becoming increasingly complex and sophisticated materials for production for the automotive market for commercial and passenger vehicles. To achieve this level of demand the use of composite materials such as carbon fiber, glass fiber or a compound of the two has become a reality, however the production rate was still considered a problem for medium volume parts (up to one hundred thousand parts per year). The work demonstrates the construction and simulation of a PoC (proof of concept) using these composites in a warm stamp process where the material a thermoset composite plate is preheated to the working temperature, then it is inserted in a tool preheated stamping, remaining closed for a few minutes where the material is consolidated and then the part is extracted already cured without the need for cooling, thus ensuring the projected production tackt compared to the autoclave
RICCI, MARCO TULIO DE RIBEIRODE MELLO, WELLINGTON LOMBARDO NUNESDE LIMA, RAPHAEL BARBOSA CARNEIRODE OLIVEIRA, JOSE ALBERTOPEREIRA, DANIEL ALMEIDAAGUIAR, DIMAS CAMPOS
This standard provides the following: a Definition of terms pertaining to marking. b Symbols for marking location. c Requirements and restrictions for permanent markings. d Types of marking methods. e Rules for designating marking methods. f Table listing marking methods.
E-25 General Standards for Aerospace and Propulsion Systems
Strain-rate sensitivity has been neglected in the simulation of the traditional stamping process because the strain rate typically does not significantly impact the forming behavior of sheet metals in such a quasi-static process, and traditional crank or link mechanical presses lack the flexibility of slide motion. However, the recent application of servo drive presses in stamping manifests improvement in formability and reduction of springback, besides increased productivity and energy savings. An accurate simulation of servo stamping entails constitutive models with strain-rate sensitivity. This study evaluated a few strain rate-sensitive models including the power-law model, the linear power-law model, the Johnson-Cook model, and the Cowper-Symonds model through the exercise of fitting these models to the experimental data of a deep draw quality (DDQ) steel. Curve fitting over segmented strain ranges and grouped strain rates were conducted so that the uniqueness of the identified
Wen, WeilingZou, YuDe Zhao, Arthur
Rosin is a naturally available organic material obtained especially from pine trees. It finds many usages and applications in areas like soldering, pharmaceuticals, building work, engineering field etc. In this work, an attempt has been made to study experimentally the improvement in strength of rosin at normal stove top temperature by means of combining rosin in various ratios with some important organic hardeners and chemicals of literature importance. A table top book press was fabricated for the purpose of rosin pressing using simple tools like teak wood, bolt and nuts. Experiments were conducted using commonly used kitchen gas stove, fabricated book press, rosin raw material, aluminium sulfate powder, maleic anhydride chemical, acetone, ethanol and saw dust particles for making different combination materials using rosin as the main element. Results showed that, rosin on its own without additives showed higher viscosity and brittleness. When combined with organic hardener
Kumar Ayyaswamy, John PresinS., SivakumarS., SathishRavikumar Solomon, Gnanadurai
Belt-driven starter generator claw pole electric motors are used in hybrid automobiles to start the engine, charge the battery and to power the electrical system when its engine is running. Shaft and claw pole are important components in the claw pole electric motor. The claw pole is fitted onto the shaft through press-fit force. Press-fit is a widely used fastening process to join two different components by pushing a component inside or over another component with high press force which will create a strong bond between the components. Determining press-fit force required to assemble parts is very complex since it depends on a lot of factors such as mechanical material properties of components, interference fit condition whether it is in Min, mean and max condition, amount of contact pressure induced by contact surface, co-efficient of friction created in between components. The press-fit will help to prevent loosening components from its bond at high torque and speed. More over
Neelakandan, VaratharajEkambaram, Ashok kumarGanesan, ThulasirajanRadhakrishnan, MuruganandamChakrapani Rao, Praveen
The aluminum alloy 7075 sheets have drawn more attention in recent years in the automotive industry for lightweighting. Hot stamping of high-strength aluminum alloy has been developed to improve the formability of the part without springback. Obtaining an adequate quench rate is a critical step of the hot stamping process and corresponds to good strength and corrosion resistance. This work looks at measuring the quench rate of 7075 at advanced aging (AA) and T6 condition via two different approaches: forced air and water with various temperatures. The results verify that water is a superior form of quenching, i.e., from 50°C/s to 550°C/s, the forced air-cooled quench rate is 2°C/s-10°C/s. Besides, mechanical properties such as yield strength, ultimate tensile strength, and uniform elongation were measured by tensile testing. As a result, a correlation between the quench rate and final mechanical properties was developed. In addition, microstructure and corrosion analyses were conducted
Chen, ZhongKaunitz, LeonWu, Cedric
Developing lightweight, stiff and crash-resistant vehicle body structures requires a balance between part geometry and material properties. High strength materials suitable for crash resistance impose geometry limitations on depth of draw, radii and wall angles that reduce geometric efficiency. The introduction of 3rd generation Advanced High Strength Steels (AHSS) can potentially change the relationship between strength and geometry and enable simultaneous improvements in both. This paper will demonstrate applicability of 3rd generation AHSS with higher strength and ductility to replace the 780 MPa Dual Phase steel in a sill reinforcement on the current Jeep Cherokee. The focus will be on formability, beginning with virtual simulation and continuing through a demonstration run on the current production stamping tools and press.
Macek, BryanLutz, Justin
In the recent decades, tremendous effort has been made in automotive industry to reduce vehicle mass and development costs for the purpose of improving fuel economy and building safer vehicles that previous generations of vehicles cannot match. An accurate modeling approach of sheet metal fracture behavior under plastic deformation is one of the key parameters affecting optimal vehicle development process. FLD (Forming Limit Diagram) approach, which plays an important role in judging forming severity, has been widely used in forming industry, and localized necking is the dominant mechanism leading to fracture in sheet metal forming and crash events. FLD is limited only to deal with the onset of localized necking and could not predict shear fracture. Therefore, it is essential to develop accurate fracture criteria beyond FLD for vehicle development. To enhance the accuracy of crash simulations, forming results from stamping process are generally introduced to consider work hardening and
Lee, Hwawonli, ShengjianHuang, Hui-Min (Emmy)Police, Parvath
Light-weight solutions for stamped steel components that exhibit the same or similar appearance properties for purposes of authentic feel and perception to customers will play a critical role as the progress towards reaching maximum fuel efficiency for large vehicles continues. This paper outlines the potential uses for laminated steel in large stamped steel bumper applications that would normally be stamped with thick sheet metal in order to meet vehicle level functional objectives. The paper presents the investigation of the one-for-one drop-in capabilities of the laminate steel material to existing stamping dies, special processing considerations while manufacturing, vehicle level performance comparisons, and class “A” coating options and process needs. Most of all, it will highlight the significant vehicle weight saving benefits and opportunities as compared to current production stamped steel bumpers.
Herz, Eric EdwinPutti, JustinMurphy, Matt
As vacuum suction cups are widely used in stamping plants, it becomes urgent and important to understand their performance and failure mode. Vacuum suction cups are employed to lift, move, and place sheet metal instead of human hands. Occasionally the vacuum cups would fail and drop parts, even it would cause expensive delays in the production line. In this research, several types of vacuum cups have been studies and compared experimentally. A new tensile device and test method was developed to measure the pulling force and deformation of vacuum cups. The digital image correlation technique has been adopted to capture and analyze the contour, deformation and strain of the cups under different working conditions. The experimental results revealed that the relevant influential parameters include cup type, pulling force angles, vacuum levels, sheet metal curvatures, etc. Also, the deformation distribution and history of the cups denote the weak part and failure mechanism during operation
Xu, WanZhang, BoyangWang, RongMa, WenGuo, BichengYang, Lianxiang
Metal panels are comprehensively applied in the automotive industry. A significant issue with metal panels is the deflection when moving in the press line of the stamping process. Unpredictable deflection could result in the cut off of the press line. To control the deflection in a safe zone, finite element tools are used to simulate the panel transform process. However, the simulation requires experimental validation where conventional displacement measurement techniques could not satisfy the requirement of vast filed displacement and accuracy point tracking. In this study, multi-camera digital image correlation (DIC) systems have been developed to track the movement of panels during the press line of the stamping process. There are some advantages of applying the DIC system, including non-contact, full-field, high accuracy, and direct measurement techniques that provide the evaluation displacement of the metal panel and press line. Nevertheless, the traditional stereo DIC system
Guo, BichengZheng, XiaowanZhang, BoyangWang, RongYang, Lianxiang
The market for electric vehicles and hybrid electric vehicles is expected to grow in the coming years, which is increasing interest in design optimization of electric motors for automotive applications. Under demanding duty cycles, the moving part within a motor, the rotor, may experience varying stresses induced by centrifugal force, a necessary condition for fatigue. Rotors contain hundreds of electrical steel laminations produced by stamping, which creates a characteristic edge structure comprising rollover, shear and tear zones, plus a burr. Fatigue properties are commonly reported with specimens having polished edges. Since surface condition is known to affect fatigue strength, an experiment was conducted to evaluate the effect of sample preparation on tensile and fatigue behavior of stamped specimens. Tensile properties were unaffected by polishing. In contrast, polishing was shown to increase fatigue strength by approximately 10-20% in the range of 105-107 cycles to failure.
Lakkonavar, VirupakshappaKavi, SwaroopJones, PeggyThompson, MargaritaLeong, Yew SumCrepeau, Paul
Third generation advanced high strength steels (AHSS) have been developed combining high strength and formability, allowing for lightweighting of vehicle structural components. These AHSS components are exposed to paint baking operations ranging in time and temperature to cure the applied paint. The paint baking treatment, combined with straining induced from part forming, may lead to increased in-service component performance due to a strengthening mechanism known as bake hardening. This study aims to quantify the bake hardening behavior of select AHSS grades. Materials investigated were press hardenable steels (PHS) 1500 and 2000; transformation induced plasticity (TRIP) aided bainitic ferrite (TBF) 1000 and 1200; and dual phase (DP) 1000. The number designations of these grades refer to minimum as-received ultimate tensile strengths in MPa. Paint baking was simulated using industrially relevant times and temperatures from 15 to 60 min and 120 to 200 °C, respectively. Samples were
Blesi, Brandon W.Smith, CharlesMatlock, David K.De Moor, Emmanuel
Titanium’s high strength-to-weight ratio and corrosion resistance makes it ideal for many aerospace applications, especially in heat critical zones. Superplastic Forming (SPF) can be used to form titanium into near-net, complex shapes without springback. The process uses a machined die where inert gas is applied uniformly to the metal sheet, forming the part into the die cavity. Standard titanium alpha-beta alloys, such as 6Al-4V, form at temperatures between 900 and 925°C (1650-1700°F). Recent efforts have demonstrated alloys that form at lower temperatures ranging between 760 and 790°C (1400-1450°F). Lowering the forming temperature reduces the amount of alpha case that forms on the part, which must be removed. This provides an opportunity of starting with a lower gauge material. Lower forming temperatures also limit the amount of oxidation and wear on the tool and increase the life of certain press components, such as heaters and platens. A variation of this process is SPF combined
Burkhart, Eve TaylorHefti, Larry
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