Weight Reduction Of Automobiles Research Articles

Development Trend in Composition Optimization, Microstructure Manipulation, and Strengthening Methods of Die Steels under Lightweight and Integrated Die Casting.

In the general environment of lightweight automobiles, the integrated die-casting technology proposed by Tesla has become the general mode to better achieve weight reduction in automobiles. The die-casting mold required by integrated die-casting technology has the characteristics of large scale and complexity. Hence, higher requirements are put forward for the comprehensive performance of the die steel. Despite the stagnation in the progress of conventional strengthening methods, enhancing the performance of die steel has become increasingly challenging. Indeed, it necessitates exploring novel die steel and optimizing heat treatment and reinforcement technologies. This article summarizes and analyzes the development status of die steel and corresponding heat treatment and microstructure manipulation as well as strengthening methods and elaborates on an excellent nano-strengthening technology. Furthermore, this review will aid researchers in establishing a comprehensive understanding of the development status of die steel and the processes utilized for its strengthening. It will also assist them in developing die steel with improved comprehensive performance to meet the high demand for mold steel in the integrated die-casting technology of the new era.

Enhancement of resistance element welding of AA6061 to DP600 steel by using external magnetic field

The application of aluminum (Al)/steel hybrid structure has a broad prospect in automobile weight reduction. In this work, AA6061/DP600 steel was joined using a resistance element welding (REW) method to achieve high strength and plasticity. To modify the deviation of weld nugget and increase the diameter of nugget, annular permanent magnet was designed and used. The effect of external magnetic field on microstructure evolution and mechanical properties was investigated. An electromagnetic stirring effect was generated inside weld nugget, resulting in a larger bonding area between Q235 rivet and DP600 steel. Convection in weld nugget contributed to restraint of dendrite growth and changes in heat distribution, leading to grain refinement at weld nugget. The microstructure of weld nugget and heat affected zone (HAZ) was bainite in magnetically assisted resistance element welding (MA-REW) specimens. The microhardness distribution presented a symmetrical distribution in both horizontal and vertical direction of cross section while the highest microhardness value occurred in weld nugget. Compared to REW specimens, MA-REW specimens achieved improvement of 10.2 % in peak load and 26.8 % in displacement during the tensile test. When the welding current reached 11 kA, the fracture mode of MA-REW specimen transformed from interfacial fracture to button fracture. Enlarged weld nugget size and refined grains were responsible for the improved performance.

Optimal Design of Leaf Springs Using Composite Materials

Abstract: The present work is to emphasizing the reduction in weight of suspension system by using composite materials instead of customary leaf springs. Also improve the level of suspension by using of composite materials. The leaf spring is one of the potential items for weight reduction in automobiles as it accounts for 10% - 20% of the unsprang weight. The process is beginning with the selection of composite materials. The selection process is focused to the checking of property of the material be chosen. After the verification, the manufacturing is done by the proper methods. Then the design calculation is done for both ordinary and novel spring system. Based on the results, the design calculation for deflection and weight of springs is compared. Keywords: Suspension Systems, Leaf Spring, Unsprung weight, Composite, Weight Reduction.

Achieving safety and weight reduction in automobiles with the application of composite material

In the present scenario of cutthroat competition in automobile industry, the importance for sleek and efficient models of automobiles with aesthetics and passenger comfort is paramount. In addition to the comforts like air conditioning and spaciousness etc., the ‘suspension’ is also significant in the selection of an automobile. The main focus of this paper is on weight reduction by replacing conventional spring steels with composite materials. A successful attempt has been made at Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad laboratories to fabricate the composite leaf spring, which is having equivalent properties of Maruti800 car leaf spring. The transverse failures in steel leaf springs lead to rear axle dislocation. This problem could be successfully eliminated with composite leaf springs since the general failure in unidirectional reinforcement composites is in longitudinal direction. This paper suggests the design improvements in this direction.

Comparative Study of Joint Performance According to Joining Methods Between Al7075-T6 and SPFC590DP for Lightweight Car Body

The necessity of dissimilar joining between aluminum alloy and steel is increasing in order to meet the demand for weight reduction in automobiles. However, dissimilar joining between 7000 series aluminum alloy and steel is challenging with mechanical joining methods such as self-piercing rivet(SPR) and flow drill screw(FDS) without hole processing. In this study, mechanical performances of dissimilar joints between 3 mm thick Al7075-T6 and 1 mm thick SPFC590DP were evaluated for use in lightweight B-pillar assembly. Self-Piercing Rivet(SPR) and Flow Drill Screw(FDS) with one-hole processing, bolt/nut and blind rivet with two-hole processing and adhesive bonding were compared with respect to joint performance. In SPR joining, rivet did not penetrate and rivet buckling occurred in the rivet due to the thickness and high strength of the Al7075-T6. By processing pre-hole on Al7075-T6 and applying an additional Al5052-H32 sheet to induce mechanical interlock in SPR joint, it became possible to join Al7075-T6 to SPFC590DP with an SPR. The tensile shear load of the SPR joint was 9.8 kN. In FDS joining, it is also necessary to process pre-hole on Al7075-T6 since the fastener could not penetrate the Al7075-T6. The tensile shear load of the FDS joining was 8.1 kN. In bolt/nut and blind rivet joining, the tensile shear load were measured respectively 11.1 kN and 5.2 kN. In adhesive bonding with 1K glue, the tensile shear load was measured 18.5 kN when the interfacial surface was roughened with a sand paper.

Optimization of process parameters of recycled carbon fiber-reinforced thermoplastic prepared by the wet-laid hybrid nonwoven process

The wet-laid hybrid nonwoven process can produce affordable carbon fiber-reinforced thermoplastic (CFRTP) because of its process simplicity, which can promote the application of CFRTP products in automobile weight reduction. The wet-laid hybrid nonwoven process involves two procedures, mainly: prepare preforms by a papermaking-like process and heat-molding compression. The parameters of heat-molding compression affect the quality of CFRTP directly, but there are not enough researches focusing on the effects of heat-molding compression parameters. This study aims to optimize the wet-laid hybrid nonwoven process to prepare recycled CFRTP. A proper carbon fiber content was determined firstly. Then, response surface methodology was used to optimize the heat-molding compression parameters. The effects of fiber length on composite properties were also investigated. The results showed that the fiber content of 30 wt% was the most suitable. The optimized heat-molding conditions were temperature, pressure, and time of 190°C, 2 MPa, and 10 min, respectively, leading to the lowest void content of 0.9%. CFRTP comprising carbon fibers with a length of 6 mm had the best properties, with the tensile strength of 59.34 MPa and flexural strength of 145.91 MPa.

(Keynote) EIS Study of Galvanic Corrosion of Al Alloy Coupled with High Strength Steel in Simulated Atmospheres

Introduction Weight reduction of automobiles is required to improve fuel efficiency. Therefore, the uses of lightweight materials such as Al alloys and CFRP is expected to increase. When an automobile is made of multi-materials, there is a concern that galvanic corrosion and crevice corrosion may occur at the joint parts.We successfully applied EIS to study corrosion of metals covered with thin solution films [1–4]. A two-electrode cell, which was composed of two identical metal plates embedded in epoxy resin with a small gap distance, was used to measure the EIS. Under very thin solution films, uneven current distribution must be considered in the EIS measurements because the current lines may concentrate on the nearest edge of the two electrodes when AC voltage is applied. The EIS characteristics of a metal/solution film interface was successfully described by an equivalent circuit of transmission line (TML) [2,3]. We reported that accurate charge transfer resistance can be obtained by curve fitting the measured EIS with a TML circuit, even if the current lines are not evenly distributed on the electrode surface [1].In this study, EIS was applied to the study of galvanic corrosion of Al alloy coupled with high strength steel under thin NaCl solution films with different thicknesses. The monitoring of the galvanic corrosion of All alloy was also carried out under a wet-dry cyclic condition by EIS. Experimental Al alloy (6016–T4, 10 mm×10 mm) and high-strength steel (980 MPa, 10 mm×10 mm) were used as specimens. They were embedded in the epoxy resin at a gap distance of 0.1 mm. A solution film of 2 M NaCl was placed on the cell surface. Three different films thickness, 0.025, 0.050 and 0.1 mm were used. The EIS was measured under the condition that the potential difference of Al alloy and high strength steel was set to zero by potentiostat. Amplitude of AC voltage applied between the two electrodes was 10 mV and the frequency range was 10 kHz to 10 mHz. Using the same cell, the galvanic corrosion under wet-dry cyclic conditions was also monitored by continuously measuring two impedance at high and low frequency. To investigate the effect of crevice, the cells with and without a crevice were employed. Result and Discussion All Nyquist plots of the galvanic couple measured under thin solution films showed two capacitive semi-circles. One semicircle with a smaller time constant can be expressed by a parallel combination of double layer capacitance Cdl and charge transfer resistance Rct for the All alloy. Another semicircle with a larger time constant can be given by Cdl / Rct for the high strength steel. The corrosion rate (CR) of the Al alloy estimated from the Rct increases with decreasing the solution film thickness. This tendency is consistent with that of the galvanic current between the two electrodes.The galvanic corrosion behavior under the wet-dry cycles in the presence of chlorides was monitored. In above experiment, the optimum frequency for monitoring Rct of the Al alloy was determined to be 0.3 Hz. Using this frequency, the corrosion rate of the Al alloy coupled with the high strength steel was monitored under the wet-dry cycles. The corrosion rate of Al alloy changed in response to the wet-dry cycles. The galvanic corrosion behavior will be discussed in the conference on the basis of the EIS monitoring data. Acknowledgements This paper is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References 1) Y. Shi, E. Tada, A. Nishikata, J. Electrochem. Soc. 162[4], C135-C139 (2015).2) A. Nishikata, Y. Ichihara, T. Tsuru, Corros. Sci. 37, 897-911(1995)3) A. Nishikata, Y. Ichihara, Y. Hayashi, T. Tsuru, J. Electrochem. Soc.144, 1244-1252 (1997)4) A. Nishikata, Q. Zhu, E. Tada, Corros. Sci. 87, 80-87 (2014)

Hot Deformation Behavior of Fe-6.8Al Low-Density and AISI 1040 Steels

Abstract Steels are the traditional choice for automobile bodies due to their low cost and good combination of strength, ductility, and formability. Aluminum-containing low-density steels have recently been materials of immense attention due to the quest for a weight reduction of automobiles. For these applications, steel parts are produced by casting, followed by forming operations at an elevated temperature. Furthermore, the application of low-density steels is highly envisaged in automobile applications. Therefore, in the present investigation, the hot deformation behavior of single phase Fe-6.8Al low-density steel, and American Iron and Steel Institute (AISI) 1040 dual phase steel has been evaluated by developing strain rate sensitivity maps. Hot compression tests were carried out at temperatures ranging between 500 and 900°C and 650 and 900°C for the Fe-6.8Al and AISI 1040 steels, respectively, at strain rates between 0.001 and 10 s−1. Microstructural features have been evaluated for both the steels and correlated to the deformation behavior. For the Fe-6.8Al steel, strain localization in the form of shear bands is detected during deformation below 600°C in the strain rate range between 1 and 10 s−1. The dynamic recrystallization of ferrite in Fe-6.8Al steel is also noted during compression at 800 and 900°C for strain rates 0.01 and 0.001 s−1. For the AISI 1040 steel, based on the microstructural features, dynamic recovery and dynamic recrystallization is reported to occur at 700 and 850°C, respectively. The optimized deformation conditions (temperature and strain rate) for the Fe-6.8Al and AISI 1040 steels are determined to be 900°C, 0.001 s−1 and 850°C, 0.001 s−1, respectively.

Galvanic Corrosion Processes of Aluminum Coupled to Iron in Chloride Solutions at Near-Neutral pH

Multimaterial structures are effective for weight reduction of automobiles, which contributes to the prevention of global warming and the decrease in CO2 emission. Steel-aluminum joints have many advantages such as low cost, high strength, and high corrosion resistance. However, galvanic corrosion was expected to occur because the corrosion potential of aluminum alloys is usually different from those of iron and steels. Considering the galvanic corrosion processes in chloride-containing near-neutral pH solutions, the existence of surface oxides is an important factor affecting the initiation of corrosion. In this research, the galvanic corrosion behavior of aluminum alloy coupled to iron and the steel in near-neutral pH solutions was investigated. Pure iron, AISI 1045 carbon steel, pure aluminum, and A5083-O(Al-Mg alloy) were used as the specimens in this research. The surfaces of pure iron and AISI 1045 were polished down to 1 µm. Pure aluminum and A5083-O were polished down to 0.25 µm with a diamond paste and cleaned ultrasonically in ethanol before electrochemical measurements. The electrode area was ca. 1 cm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. In diluted synthetic seawater (200mg/L [Cl-], pH 8.2, naturally aerated, galvanic current was measured for 20 h using zero resistance ammeter technique. The distance between two electrodes was 1 cm. Fig. 1(a) shows the time variation of the galvanic current and electrode potential of pure aluminum coupled to pure iron. From the beginning of the immersion to 30 ks, many current transients were generated. However, after 30 ks, the galvanic current became a constant value of approximately 0.15 µA cm-2. The potential gradually decreased with time. The pH of the electrolyte decreased from 8.2 to 6.7 by galvanic corrosion. Fig. 1(b) and 1(c) shows the electrode surfaces of pure iron and pure aluminum after galvanic current measurements. Rust was observed on pure iron, and filiform corrosion was generated on pure aluminum. Anodic polarization curves were measured in diluted synthetic seawater (200mg/L [Cl-], deaerated), and the pH was adjusted to 8.2, 6.7, 5.2, 3.7, and 2.2 with NaOH or H2SO4. Potentiodynamic polarization was started from corrosion potential, and the scanning rate was 23 mV min-1. The electrode potential of pure aluminum under galvanic coupling conditions was found to be lower than the pitting potentials of pure aluminum. But, corrosion was initiated on the aluminum surface (see Fig. 1(b, c)). The galvanic corrosion behavior of pure aluminum and aluminum alloy AA5083 were discussed in terms of the surface properties of the specimens and solution chemistry. Figure 1

Viscoplastic parameter identification of temperature‐dependent mechanical behavior of modified polyphenylene oxide polymers

Modified polyphenylene oxide (MPPO) is a widely known thermoplastic polymer and is extensively utilized for weight reduction of automobiles since it possesses outstanding mechanical properties, such as resistance and toughness. In this study, the viscoplastic behaviors of MPPO with respect to changes in temperature were identified through an approximate optimization method. For this work, parameter studies were conducted with a tensile simulation of the MPPO polymer, in accordance with the modified two‐layer viscoplastic material parameters and the suggested shift parameter. The sensitivity tendency of the force‐displacement curves was captured in accordance with the material parameters. Computational experiments for obtaining calibration error data were performed using the material parameters based on interior central composite design. Surrogate models of root mean square error relative to force and displacement were generated using the response surface method. The accuracy of the surrogate models was evaluated with R‐square. Optimization for obtaining the material parameters was performed using the non‐dominant sorting genetic algorithm‐II. The results showed that the calibration error from the finite element analysis was minimized and agreed with experimental data. POLYM. ENG. SCI., 59:E200–E211, 2019. © 2018 Society of Plastics Engineers

Innovative Development of High Strength Sheet Steel for Automobile Weight Reduction

Innovative Development of High Strength Sheet Steel for Automobile Weight Reduction

Prevention of crack in stretch flanging process using hot stamping technique

Demand for enhancing of passenger safety as well as weight reduction of automobiles has increased the use of high strength steel sheets. As a sheet metal is a lightweight having high strength is suitable for producing automotive parts such as white body panel. The stretch flanging of the high strength steel sheet is a problem due to high springback and easy to crack. This study uses three methods to stretch flange the sheets; using lubricants, shear-edge polishing and hot stamping. The effectiveness of these methods will be measured by comparing the flange length of each methods can achieved. For stretch flange with lubricant and polished sheared edge, the flange length failed to achieve the target 15 mm while hot stamping improved the formability of the sheet and preventing the occurrence of the springback and crack. Hot stamping not only improved formability of the sheet but also transformed the microstructure into martensite thus improve the hardness and the strength of the sheet after been quenched with the dies.

Microstructure and Mechanical Properties of Friction Stir Welded Dissimilar Titanium Alloys: TIMET-54M and ATI-425

Weight reduction in automobiles and in aerospace industries can profoundly register for the behemoth change in the consumption of the fossil fuels and, in turn, CO2 emission. With a promising hope in hindsight for weight reduction, we have successfully produced butt joints of friction stir welded (FSWed) dissimilar, and rather novice, α-β titanium alloys—ATI-425 and TIMET-54M. The study presented in this article encompasses the microstructural and mechanical properties of the joints for two cases, (1) ATI-425 on the advancing side; and (2) TIMET-54M on the advancing side. The evolution of microstructure and concomitant mechanical properties are characterized by optical microscopy, microhardness, and tensile properties. A detailed description of the microstructural evolution and its correlation with the mechanical properties have been presented in this study. Our investigations suggest that mixing patterns are dependent on the location (advancing, or retreating) of the alloying sheet. However, the microstructure in the weld nugget (WN) is quite similar (grain boundary α, and basket weave morphology consisting of α + β lamellae) in both cases with traces of untransformed β. The thermo-mechanically affected zone (TMAZ) on the either side of the weld is primarily affected by the microstructure of the base material (BM). A noticeable increase in the hardness values in the WN is accompanied by significant deflection on the advancing and retreating sides. The tensile properties extracted from the global stress strain curves are comparable with minimal difference for both cases. In both cases, the fracture occurred on the retreating side of the weld.

衝撃荷重下における純マグネシウムの高温圧縮変形応答

Weight reduction of automobiles is one of the effective methods to reduce greenhouse gas emissions. The use of magnesium may allow weight reduction of automobiles due to the low density. However, it is difficult to apply magnesium for structural components, and plastic working methods under dynamic loading, such as high-speed rolling, are not established because the material exhibits limited ductility. To establish their method, the basic understanding about deformation mechanism under dynamic loading at elevated temperature is essential. In this study, we conducted compression test under dynamic loading at elevated temperature in order to clarify the deformation mechanism of magnesium. The results showed that high ductility was obtained over 573K while low ductility was below 473K. Deformed microstructure obtained with SEM/EBSD to clarify the effect of temperature.

TIG–MIG hybrid welding of ferritic stainless steels and magnesium alloys with Cu interlayer of different thickness

The joining of ferritic stainless steels and magnesium alloys is light and economic for weight reduction of automobiles. Unlike previous conventional welding method, a novel TIG–MIG hybrid welding is applied for the joint successfully in this study. The melted Mg weld metal wets the ferritic stainless steels surface to form a brazed Mg–Cu to steel connection when the interlayer thickness is 0.02mm. When the interlayer thickness is 0.1mm, the intermetallic compounds transition layer determined the tensile-shear strength of joints. Intermetallic compounds transition layer has been found in the 0.1mm thick interlayer joints and no particle has been found in the 0.02mm thick interlayer joints. Based on the analysis of microstructure and properties, joining and strengthen mechanisms of the joint were discovered. As the thickness of the Cu interlayer increases, the joining mechanism changed. The joining and strengthen mechanisms are mainly determined by the thickness of the interlayer. The tensile-shear strength of 0.1mm thickness Cu interlayer joints is improved by 47% compared to 0.02mm Cu.

The Influence of Punch-Die Clearance on Blanked Edge Quality in Fine Blanking of Automotive Sheets

Fine blanking is a widely used process that permits the production of precise finished components which are cleanly sheared through the whole cutting surface. It can be eliminated secondary operations, such as milling, grinding, etc. Many studies on the weight reduction of automobile for fuel saving were underway. The clearance of the punch-die of a fine blanking tool is an important design factor that affects the sheared surface of a product. If the clearance is too big, a fractured surface would occur in the product while if it is too small, bulging would occur. The main objective of this paper is to provide an overview of the effect of clearance between punch and die in a fine blanking tool on quality of sheared surface. A well as to specify the effect of mechanical properties of sheared steel sheet on blanked edge quality given by ratio of hv/a0.

Light-weight design of automotive suspension link based on design of experiment

It is well known that the targeted fuel efficiency could only be achieved by more than 40% reduction of the vehicle weight through improved design and extensive utilization of lightweight materials. In order to obtain the goal of the weight reduction of automobiles, the researches about lighter and stronger suspension link have been studied without sacrificing the safety of automotive suspension. In this study, the weight reduction design process of suspension link could be proposed based on the variation of von-Mises stress contour by substituting an aluminum alloys (A356) having tensile strength of 310 MPa grade instead of STKM11A steels. In addition, the effect of the stress and stiffness on shape variations of the suspension link were examined and compared carefully. It could be reached that this approach method could be well established and be contributed for light-weight design guide and the optimum design conditions of the automotive suspension link development.

Application of Magnetic Barkhausen Noise Test System in Hot Stamping

Hot-stamped high strength steel (HSS) is widely used in body structure as a solution for weight-reduction of automobiles. In order to realize fast field measurement of mechanical properties of hot-stamped HSS parts, a magnetic Barkhausen noise (MBN) test system was developed. The system was used to measure hardness of hot-stamped bumper beam and strip with tailored properties. Results show good precision and convenience of the MBN method.

Overview of Lightweight Ferrous Materials: Strategies and Promises

Reducing the density of steels is a novel approach for weight reduction of automobiles to improve fuel efficiency. In this overview article, strategies for the development of lightweight steels are presented with a focus on bulk ferrous alloys. The metallurgical principles of these steels and their mechanical properties of relevance to automotive applications are discussed. Some of the engineering aspects highlighting the possible problems related to mass production of these steels are also considered. Application prospects of these steels vis-a-vis standard automotive steels are shown.

A Study on the Clearance Design of Fine Blanking Tool for Al Special Parts with Various Inner Corner Shapes

Fine blanking is a press-working process that permits the production of precise finished components which are cleanly sheared through the whole cutting surface. It can be eliminated secondary operations, such as milling, grinding, etc. Recently, many studies on the weight reduction of automobile for fuel saving were underway. Especially, there are many examples in which light metal like Al were applied for automotive parts. The clearance between the punch and die of a fine blanking tool is an important design factor that affects the sheared surface of a product. In a fine blanking process, the clearance is typically assigned a 0.5% material thickness. If the clearance is too big, a fractured surface would occur in the product while if it is too small, bulging would occur. In this study, a setting for optimum clearance was proposed for inner corner shapes by checking shear characteristics and bulging effects according to various clearances. After designing a special part with various corner shapes possessing Al5052 (thickness: 4 mm), a fine blanking tool was constructed and fine blanking experiments were conducted. The result could be usefully applied in fine blanking processes for Al automobile parts with corner shapes in the future.