Download or read book Investigation of Resistance Spot Weld Failure in Tailored Hot Stamped Assemblies written by Cameron O'Keeffe and published by . This book was released on 2018 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results from the mechanical characterization of resistance spot welds within hot stamped USIBOR® 1500-AS steel sheet (1.2 and 1.6 mm thickness) with tailored properties. Three parent metal conditions, ranging from a fully martensitic (495 HV) to a mixed ferritic-bainitic microstructure (211 HV), were obtained using in-die heating (IDH) to control the cooling (quench) rate during the hot stamping process. Flat sheets and hat channel geometries were produced through die quenching in which the die was maintained at 25, 400, and 700°C with strengths of 1,548, 817, and 671 MPa, respectively. The as-quenched sheets were resistance spot welded and mechanically tested in lap shear, cross tension, V-bend, and JIS tensile coupon geometries to characterize the mechanical response of single welds under various loading orientations. Hardness testing was conducted on the welds to investigate the hardness (strength) distribution in the welded region, heat affected zone (HAZ) and parent metal. The drop in hardness within the HAZ increased as the parent metal strength increased, such that the hardness of the HAZ was similar for all three spot welded parent metals (211-318 HV). In the mechanical testing, strain localized in the HAZ (or nugget) with the result that the strength of the welds was relatively constant for all die quench conditions. For the range of material conditions considered, the lowest weld strength 4.0-4.5 kN was measured in the cross-tension tests compared to 12.1-15.0 kN for the lap shear tests (data for 1.2 mm sheet). A new mechanical test, termed the “Caiman”, was developed to study groups of welds under both static and dynamic Mode I structural loading. Channel sections comprising of fully quenched material as well as hot stamped components with tailored, lower strength flanges were joined via spot welding. The experiments subjected the welded regions to Mode I tensile loading to investigate how failure propagated along the spot weld line. It was found that the energy absorption within the welded connections was higher for the lower strength (tailored) parent metal conditions, largely due to activation of plastic deformation within the parent metal as opposed to the fully martensitic condition for which deformation was confined to the weld nugget or HAZ. High speed thermal imaging was shown to be an effective method to detect failure of individual welds and track failure propagation within the welded assembly due to local adiabatic heating associated with weld fracture or pullout. Temperature increases of 7 °C were typical of quasi-static loading whereas increases of 80 °C were observed under dynamic loading. It was determined that initiation of the first weld failure was delayed slightly under dynamic loading (relative to quasi-static); however, failure propagation after initiation was more rapid for dynamic loading for a given load point displacement. Numerical simulations of the lap shear and cross tension single weld experiments were used to calibrate weld failure models within the commercial finite element software LS DYNA, with relatively good correlation to the experimental data. The calibration exercise revealed the importance of simulation of the post failure response, in particular the use of the “fade energy” numerical parameter, to more accurately capture the energy released during the weld fracture event. The weld failure models calibrated from the single weld tests were applied to simulate the static and dynamic Caiman experiments without additional “tuning”. For the quasi-static Caiman simulations, the predicted load-displacement response and failure propagation were relatively accurate, with higher errors for the fully martensitic case since the HAZ was not modelled. The dynamic simulations aligned relatively well with the experimental results.

Download or read book Resistance Spot Welding and In process Heat Treatment of Hot Stamped Boron Steel written by Jeff Shao-Chun Hou and published by . This book was released on 2016 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Escalating environmental concerns have prompted efforts to reduce vehicle weight and carbon emissions, resulting in increased application of advanced high strength steels (AHSS). 22MnB5 hot stamping grade AHSS, namely USIBOR 1500P, provide high strength to weight ratio allowing sheet thickness reduction to decrease weight, while maintaining high safety characteristics. Resistance spot welding (RSW) has been the predominant welding process for automotive assemblies. Welding hot-stamping AHSS has introduced new challenges for achieving acceptable welds. The added alloying elements and high hardenability characteristics resulting in low weldability and weld toughness complicates this initiative. The current study examines the effects of in-process weld tempering with secondary current pulse has on the weld toughness during RSW of USIBOR steels. RSW and weld tempering were tested on USIBOR at two different surface conditions; as-delivered and hot-stamped. Joint performance properties, micro-hardness map profiles, and failure modes of welds for both tempered and non-tempered conditions are detailed. Furthermore, a relationship between resulting joint performance and microstructural evolution is produced. The objective of this work is to optimize in-process tempering parameters, analyze metallurgical evolution of the weldments, and compare the effects on mechanical performance for both tempered and non-tempered welds.

Download or read book Investigation of Failure Mechanisms of Resistance Spot Welds in Automotive Steels Using Various Techniques written by Feng Yu and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strength Investigation on Resistance Spot Welding of Low Carbon Steel and Stainless Steel written by Mohd Nur Syaffiq Mahmood and published by . This book was released on 2013 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resistance spot welding (RSW) had been widely used in automotive industry; because of their advantages easily to process and low cost, high speed and high production, suitability for automation. About 2000-7000 spot welds were used in joining modern vehicles. This project deals with the investigation of failure mode and mechanical properties of weld joint of low galvanized steel and stainless Steel. The main objective of this project is strength investigation using RSW of low carbon steel and stainless steel. For design of experiment, Taguchi method was employed by using Minitab software, and total nine sets experiment with 3 type of parameter (current, squeeze time, pressure) were conducted. The studies of mechanical properties, are consists of various tests; Tensile test, Coach Peel test, Hardness test, microstructure to analyze and investigate the weldability of galvanized Steel and stainless Steel sheet. Visual inspection was done to determine the failure mode of the spot welding. As a result, tensile test have larger strength variation than the coach-peel test. Wider width and depth of weld nugget affect the weldability of the welding. Different parameters were obtained for optimum parameter for tensile test and coach peel test by using Taguchi method. Almost pullout failure mode occurs where failure at heat affected zone (HAZ) around the nugget circumference.

Download or read book Proceedings of the 61st Conference of Metallurgists COM 2022 written by Metallurgy & Materials Soc. of CIM and published by Springer Nature. This book was released on 2023-01-05 with total page 975 pages. Available in PDF, EPUB and Kindle. Book excerpt: These Proceedings represent the metallurgical engineering and materials science research presented at the 61st Annual Conference of Metallurgists. The collection themed ‘The Pathway to Net-Zero’ presents findings on a wide range of topics including: Processing of Critical Materials Towards Sustainable Circularity: Mining to Materials Deep Decarbonization Pathways for Pyrometallurgical Processes: Opportunities & Challenges Energy and Environmental Materials Light Metals for the Transportation Industry Advances in Materials Manufacturing VI – Existing and Emerging Materials Electrochemical Degradation of Multi-component Materials

Download or read book Resistance and Ultrasonic Spot Welding of Light weight Metals written by Ying Lu (Ph. D. in welding engineering) and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-materials vehicle structures, employing light-weight metals such as advanced high strength steels (AHSS), aluminum alloys, can satisfy the ever-increasing requirement of light-weighting and fuel efficiency, as well as maintaining or improving the crash resistance of vehicles. The present research provides a fundamental understanding of the process-microstructure-mechanical properties of resistance and ultrasonic spot welding of light-weight metals. The dissertation consists of three main parts: (1) study of the relationship of process-microstructure-mechanical properties for resistance spot welded two sheets (2T) and complex stack-ups of ultra-high strength grade of AHSS, (2) development of a novel technique, namely Ultrasonic Plus Resistance Spot Welding, for dissimilar metal joining of Al to steel, and (3) investigation of the bonding mechanism of USW of Al by in-situ relative vibration measurement. In the first part, softening in subcritical heat affected zone of resistance spot welded hot-stamped boron steels is investigated by weld microstructure characterization and tempering kinetics of martensite. The local constitutive behavior of the potential failure locations is extracted and incorporated into performance model to investigate its effect on the accuracy of deformation and failure prediction. A major challenge for RSW of complex stack-ups with large thickness ratio is the limited nugget penetration into the thin sheet at the outside of the stack-up. The effect of welding current, electrode force, electrode material/size on nugget formation and the possible ways to improve nugget penetration into the thin sheet are investigated for 3T and 4T stack-ups of AHSS. The second part of the dissertation is focused on the development of a new dissimilar metal joining method, namely ultrasonic plus resistance spot welding (abbreviated as U+RSW) for Al/Steel. The bonding mechanisms have been investigated through numerical simulation to validate the concept. The third and last part of the dissertation is to understand the bonding mechanism in USW. Particularly, the relative motion of the sonotrode, aluminum specimens, and anvil in USW is investigated using an in-situ velocity measurement technique, Photonic Doppler Velocimetry (PDV). The relative motion analysis is correlated to destructive testing results, including lap-shear tensile testing and weld microstructure characterization, to understand and quantify bond formation during USW. In summary, the present research studies the process-microstructure-property relationships of resistance spot welding of AHSS, dissimilar metal welding of Al to steel, and ultrasonic spot welding of Al. An improved fundamental understanding is developed for (1) heat conduction, electric current flow, mechanical stress and deformation, and nugget formation in 2T and complex stack-ups of resistance spot welded ultra-high strength steel, (2) tempering kinetics of martensite and SCHAZ softening, (3) microstructure-specific constitutive behaviors, (4) weldability, intermetallics, and strength of dissimilar metal joint between Al and steel in U+RSW, and (5) bonding mechanism in USW. Such new knowledge is essential to ensure sound multi-materials vehicle structures employing various light-weight metals to satisfy the ever-increasing demand for fuel efficiency and crash resistance.

Download or read book Effect of Surface Condition on Resistance Spot Welding of Advanced High Strength Steel written by Xu Han and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced high strength automotive sheet steel (AHSS) is used in body-in-white design to reduce vehicle weight while maintaining high crashworthiness. Surface coatings applied to AHSS to protect it from oxidation and decarburization during its processing and life cycle. Due to the characteristics of AHSS, including alloying content and thermal process requirements, a variation of final surface conditions is possible. The resistance welding process is affected by surface changes as it alters the electrical contact resistance. As a result, a change in resistance spot welding process window occurs. Without proper attention, this variation in the operation window could reduce the joint strength and results in an unpredictable failure by having an undersized nugget. In this study, two surface-related phenomena, internal oxidation, and zinc diffusion, were investigated to characterize their impact on resistance spot welding. Additionally, a heat input based electrical dynamic resistance approach was proposed to determine appropriate welding current given variations in the Zn diffusion layer resulting from heat treating during this hot stamping process for PHS steels. Promotion of internal oxidation is used in Zn galvanizing line to improve the wettability of the steel surface to the Zn pool via the enhancement of the reactive wetting. The presence of these internal oxides has shown to shift the weld lobe to higher currents, increasing the time required to generate an acceptable weld. Study of weld development showed that surface melting is responsible for this shift in the weld process window. The surface melting created a liquid contact surface between the faying surface, which reduced the electric contact resistance and heat generation at the weld faying surface. A smaller nugget was formed due to the reduction of heating. To compensate for this reduced heat generation, a higher welding current was required when RSW of internally oxidized samples. Zinc diffusion from the galvannealed coating to the steel substrate occurs when a galvannealed steel was exposed to elevated temperature during heat treatment in the press-hardening process. This formed a Fe-Zn diffusion layer. The thickness and composition of the diffusion layer were found to be dependent on heat-treatment conditions. With an increase in heat-treatment time, the electrical resistance of the steel sheet was observed to increase as well. With higher electrical resistance, less welding current was needed to weld the material. While a change in nugget size occurred when welding steels made using different heat-treatment conditions with constant welding parameters, the mechanical lap shear strength was not impacted. Martensite tempering in the heat-affected region was more severe in samples with a larger diameter weld nugget, which decreased the required stress for failure to occur, counter-acting the increase in strength gained from the larger nugget size. This work has shown that with a heat-treatment time ranging between 4 to 10 minutes, a robust resistance welding schedule can be determined to generate a mechanically sound weld. Dynamic electrical resistance has been used to monitor the weld quality. Heat input analysis was shown to reflect the weld development as it takes into account the full weld cycle. Heat input has shown to have a linear correlation with nugget size. Undersized nugget can be successfully detected and corrected by changing the welding current based on the heat input value calculated from dynamic resistance measurement.

Download or read book Annual Index abstracts of SAE Technical Papers written by and published by . This book was released on 2005 with total page 1016 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Resistance Welding written by Hongyan Zhang and published by CRC Press. This book was released on 2011-12-13 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drawing on state-of-the-art research results, Resistance Welding: Fundamentals and Applications, Second Edition systematically presents fundamental aspects of important processes in resistance welding and discusses their implications on real-world welding applications. This updated edition describes progress made in resistance welding research and

Download or read book Thomas Register of American Manufacturers written by and published by . This book was released on 2003 with total page 2152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vols. for 1970-71 includes manufacturers catalogs.

Download or read book Technical Literature Abstracts written by Society of Automotive Engineers and published by . This book was released on 2000 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Failure Analysis of Heat Treated Steel Components written by Lauralice de Campos Franceschini Canale and published by ASM International. This book was released on 2008 with total page 651 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1076 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Growth in Rubber Materials written by Gert Heinrich and published by Springer Nature. This book was released on 2021-03-23 with total page 491 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book summarizes recent international research and experimental developments regarding fatigue crack growth investigations of rubber materials. It shows the progress in fundamental as well as advanced research of fracture investigation of rubber material under fatigue loading conditions, especially from the experimental point of view. However, some chapters will describe the progress in numerical modeling and physical description of fracture mechanics and cavitation phenomena in rubbers. Initiation and propagation of cracks in rubber materials are dominant phenomena which determine the lifetime of these soft rubber materials and, as a consequence, the lifetime of the corresponding final rubber parts in various fields of application. Recently, these phenomena became of great scientific interest due to the development of new experimental methods, concepts and models. Furthermore, crack phenomena have an extraordinary impact on rubber wear and abrasion of automotive tires; and understanding of crack initiation and growth in rubbers will help to support the growthing number of activities and worldwide efforts of reduction of tire wear losses and abrasion based emissions.

Download or read book Ultrasonic Welding of Aluminum written by J. Byron Jones and published by . This book was released on 1955 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Welding Design Fabrication written by and published by . This book was released on 1993 with total page 1068 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thomas Register written by and published by . This book was released on 2004 with total page 2038 pages. Available in PDF, EPUB and Kindle. Book excerpt: