bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a program for automatic identification of productivity of construction workers
Authors: Kasai Ryuji , Goso Takashi , Osawa Tetsuro
Published: June 2023

In the Japanese construction industry, work environment and productivity data of construction projects are collected and analyzed by on-site engineers as individual data based on attendance and performance records. Therefore, productivity data are not uniformly collected and cannot be considered as highly reliable. Therefore, in this study, a prototype of a system is developed that automatically collects data regarding the workers’ activities using sensors and analyzes the working environment and productivity of construction projects. Although image analysis is typically employed for capturing workers’ activities, it is extremely costly and time-consuming for collecting and discriminating data. In addition, it is not practical because it requires adjusting the system to suit the changing environment of the construction site each time. Accordingly, we have conducted motion-detection using accelerometers, gyro-sensors, and GPS that can be attached to individual workers. We have constructed a hierarchical system that combines a phase to detect large acceleration changes that trigger motion, a phase to discriminate periodic motion, and a phase to classify motion by machine learning. The system classified motions into three productivity types: “direct work,” “support,” and “delay.” As a result of applying this system to the sensing data of workers performing road pavement construction-related works, the system discriminated with an overall accuracy rate of 42%. Furthermore, because of the wide range of behaviors that correspond to each productivity behavior category, a large amount of data must be read from the site adopting the system for obtaining training data to perform final behavior classification by machine learning based on the sensing data. Therefore, a system relying on machine learning may not be able to achieve a higher accuracy; thus, in the near future, we aim to automatically discriminate the nine categories of productivity behaviors shown in previous studies.
Questionnaire on employee awareness of disaster mitigation measures in municipal governments
Authors: Goso T , Kakuzaki T
Published: June 2023

In the event of a disaster, municipal governments are expected to fulfil several responsibilities. However, owing to organizational reforms, cost reductions, and workforce reductions experienced by Japanese municipal governments in the 1990s and 2000s, they have arguably become incapable of providing effective community-based administration. In this context, a questionnaire survey was conducted on the employees of municipal governments in coastal regions of Japan where earthquakes and tsunamis are commonly anticipated. An attempt was made to evaluate the current state of disaster awareness within organizations and among staff members based on the survey results and clarify organizational and individual issues. Those surveyed were 288 officials with significant disaster response roles. The questionnaire survey was conducted to evaluate their understanding of various disaster response measures and their knowledge of their responsibilities. In the questionnaire, three disaster phases were considered: the predisaster, rescue, and reconstruction phases. The responses of each employee corresponding to each phase were recorded. The results indicate that, although various plans were well known to all participants to a certain extent, the level of understanding varied between departments. In addition, departmental employees who were often involved in disaster mitigation were concerned about the coherence and effectiveness of the operations undertaken in various plans. Thus, these issues should be considered in future reviews of disaster response plans. Despite considerable progress in the development and distribution of emergency plans, much remains to be done to raise awareness regarding specific action plans among the staff. This concerns the specificity, coherence, and effectiveness of each plan rather than the knowledge of the personnel.
Study on the Conditions for setting Target Prices in Japanese Grant Aid Projects
Authors: Takatsu H
Published: June 2023

Japan has been implementing grant aid projects for developing countries for many years, but in recent years, many projects have experienced unsuccessful bidding (i.e., all bid prices are higher than the target price), due to a gap between the project target price and the bid price. For public works contracts in Japan, contracts may not be signed for more than the target price under any circumstances. Therefore, if the bid price exceeds the target price, a tender cannot be completed. The estimation method used for Japanese grant aid projects uses estimation standards developed for domestic construction projects in Japan with some modifications for overseas projects, but it is not possible to fully include the cost of the following risks in the target price; therefore, the difference between the target price and the bid price is assumed to occur. The target price is used as the reference price so that the final contract price may exceed the target price; instead, the price, including the upfront cost, is used as the maximum price for the project. In this way, the rate of unsuccessful bids for Japanese grant aid projects in bilateral contracts may decrease and the discrepancy between the target price and the bid price may disappear.
Analysis of urban drainage system to avoid rain water overflow on the access road to Juanda Airport
Authors: Fikri Adams Nur Oktalinov , Tjendani Hanie Teki , Oetomo Wateno
Published: June 2023

The access road to Juanda Airport from Jalan Raya Waru (Aloha Resto) Sidoarjo is frequently flooded when it rains with a height of more than 30 cm along 1.6 km. This greatly annoys the flow of traffic to the airport. The airport can only be passed through this street and the Juanda Airport toll road. This research was conducted by observing and recording conditions during the occurrence of floods and analyzing the drainage facilities in the research area based on the 5-years design discharge because this location is a densely populated residential and industrial area. The results showed that the addition of channel capacity using U-ditch was not able to accommodate the 5-year planned discharge of approximately 2.670 m3/sec. Since around the industrial location, there is a natural water reservoir that can keep water up to 3.526 m3/sec, it is necessary to add a water pump to drain water to the temporary water reservoir location so that water does not stagnate on the access road to Juanda Airport.
Infrastructure development strategy based on the accessibility to tourism location (case study of Bali Province-Indonesia)
Authors: Suthanaya P A , Suwarningsih R
Published: June 2023

As one of the famous tourist destinations in Indonesia, Bali has many places or tourist areas that can be visited. Economic of Bali Province was highly dependent on tourism industry. The development and spatial distribution of the tourism locations were not evenly distributed. This has resulted in the development and economic disparities between regencies. This is a challenge on how to develop a more balanced economic development between regencies. One way to assess the spatial distribution of tourism development is by evaluating the accessibility to tourism location. This study aims to analyze the accessibilities to tourism location and propose the infrastructure development strategy to improve the accessibility of the regencies with low accessibility values. Accessibility was measured based on travel distance and time. The spatial distribution of the accessibility value was measured based on the Z-score. The results indicate that the highest level of accessibility was found in Denpasar city. On the other hand, low accessibility values were found in Jembrana, Tabanan, Buleleng, and Karangasem regencies. Several solutions were proposed to increase accessibility such as road widening, building toll road, building shortcuts, and railroad development.
Solution to the traffic problems of long and deep water straits–smart submerged floating tunnel and its research
Authors: Xiang Y Q , Chen J , Shen Y G , Yang Y S
Published: June 2023

Submerged floating tunnel (SFT) is a new type of structure across long and deep water straits and waterways with good application prospects. The structure is different from the traditional large-span bridges and immersed tunnels, which can effectively avoid difficulty under the construction of bridges foundation in deep water straits and channel, the high cost of large span bridge, influence of typhoons and heavy fog et al. severe weather on the vehicle driving on the bridges, a series of technical problems confronted under the construction of immersed tunnel or tunnel excavation in complex marine geology and the deep sea and risk control and so on. This paper, in the light of the characteristics of submerged floating tunnels and the requirements of marine deep water environment, discusses some of technical challenges faced in the designing and building the SFT, points out that it is necessary to systematically study the design and load condition, the smart composite material and shape optimization, the calculation theory and method for analyzing the structural behavior, the structure safety evaluation, construction methods and key technology, and engineering risk analysis, smart monitoring, evaluation and control, code or guide for design and construction of SFT. It lays foundation for design, construction and engineering risk analysis, etc. of submerged floating tunnel across the long and deep waterways in the future.
Climate change effect on water balance for water critically in upper Bogowonto Watershed, Indonesia
Authors: Kurniyaningrum E , Kurniawan M.A.
Published: June 2023

The impact of climate change has hit Indonesia, especially in Central Java Province. Based on rainfall data between 1981-2017, there has been a trend of changes in intensity and a shift in rainfall patterns with an increase in temperature of 1.04°C/year. The focus of this study is in Bogowonto Watershed is located in Purworejo Regency, where the development of land cover has been increased and affected water demand in the area around the study location. The purpose of this study was to determine the conditions of rainfall due to climate change based on land cover conditions. The analytical method in this study is related to water availability with FJ. Mock and climate change with GCM with RCP scenario. The results obtained are: (1) The condition of annual rainfall in Bogowonto Watershed is still in the moderate category, with an annual rainfall of 2064.3 mm. Annual rainfall fluctuations are in adequate amount (200-500 mm per year); (2) The calculation of the WHC value of 104.92 shows that the ability of the land in the study area to store and bind water is low due to the type of soil that has shallow to moderate soil solum and the structure of the soil is kersai and sandy. Types of vegetation cover in the form of secondary crops with shallow parakaran zones also affect the value of WHC; (3) Meteorological water balance analysis can be concluded that the availability of water from rainfall in this area is quite high; (4) Water criticality index has a value of 0.66 which is included in approaching critical if water resource conservation is not carried out; (5) based on the results of climate change that occurs, for the next 40 years there will be changes in the intensity and pattern of rainfall distribution if climate change cannot be controlled and (6) The carrying capacity of Bogowonto watershed needs to be maintained by promoting plantation of useful vegetation in surrounding area of watershed.
Deployment and use of Artificial Intelligence (AI) in water resources and water management
Authors: Mahardhika Sakti Prajna , Putriani Okkie
Published: June 2023

The demand for water resources is continuously increasing as the world population grows, and this is putting significant pressure on the available water supply. According to estimates, the world will face a 0% gap between water demand and supply by 2030 under current practices. Moreover, the shortage of water resources, unpredictable hydrological conditions, and extreme weather events such as floods and droughts pose a severe threat to stability and prosperity. One way to address this issue is by utilizing artificial intelligence (AI) to develop efficient water treatment plants and optimize water resources to reduce energy costs in the long run. AI can be employed in water management to analyze data, create regression models, and develop algorithms that aid in building effective water supply systems and networks, as well as assessing the health of water resources. The application of AI in water management and infrastructure can lead to the development of intelligent water systems that are sustainable, cost-effective, and adaptable to changing conditions. This technology allows for optimization of water management solutions and prediction of potential damage. Through a literature review that examines the intersection of Artificial Intelligence and Civil Engineering in the context of Water Resources and Water Management, this study highlights the potential of AI to transform water management practices. Bibliographic mapping using VosViewer is proposed as a means of directing future research in this area.
Carburization behavior at elevated temperatures and mechanical properties of a hot stamped complex phase steel
Authors: Risse J H , Sippel F , Merklein M
Published: June 2023

As a lightweight construction strategy, hot stamped parts of ultra-high-strength steels with tailored properties are increasingly used for crash relevant components in car bodies, e.g., as B-pillars. With the process of tailored carburization, parts can be reinforced locally without increasing the sheet metal thickness. Thus, this process has the potential to be applied to lightweight components for no deformation zones, e.g., in the battery housings. Standardly, carburization is performed at 950 °C, with the highest strengths achieved at long times of up to 6 h, which prolongs the total process time. By raising the temperature, the carbon diffusion increases, which enables a reduced heat treatment time and, consequently, a shorter process time. Therefore, the objective of this study is to investigate the influence of elevated carburization temperatures on the mechanical properties of a carburized and hardened complex phase steel, CP-W® 800. A single carburization step at the enhanced temperatures leads to an embrittlement of the samples. Hence, an additional diffusion-annealing step is implemented to homogenize the carbon content, without enlarging the total heat treatment time. Depending on the time allocation of carburization and diffusion, the application of the diffusion annealing step results in higher strengths and ductility compared to only carburized samples.
Numerical analysis of the load paths and the resulting damage evolution during deep drawing of dual-phase steel
Authors: Müller Martina , Herrig Tim , Bergs Thomas
Published: June 2023

Within the deep drawing process chain, damage develops and evolves – starting with foreign particles from the slag as well as non-metallic inclusions leading to voids, which develop, accumulate and ultimately lead to failure. This damage accumulation and evolution along the process chain decisively influences the performance of components. Accordingly, the influence on the damage accumulation and evolution offers a lever to increase the performance of components. The final damage state in the component has been shown to be dependent on the prevailing load path by means of the stress and strain states along the process route. The investigation of the stress and strain states requires numerical modelling. From the models, the load path can then be extracted and a correlation can be obtained with the damage that results. The present work investigates the load paths during deep drawing of u-shaped profiles as a function of process set-up and process parameters of dual-phase steel DP800. The resulting load paths are extracted, analyzed and correlated with the numerically predicted damage.
Part quality improvement in flexible roll forming of a combined variable width and depth component
Authors: Abeyrathna B , Rolfe B , Taube R , Oxley B , Weiss M
Published: June 2023

Flexible Roll Forming (FRF) is an advanced manufacturing process that can be used to form long and complex part families from hard to form materials for the automotive and truck industry. However, depending on the part complexity and material strength shape defects such as end flare, springback and twist can occur. In this work a high strength automotive part (Sled runner) is produced from 3 high strength steels; the complex component combines shape variations in width and depth. The optimum forming sequence is identified to produce the part without any flange wrinkles. In addition to this, a new over forming technique is introduced to overcome end flare and springback. The experimental results are evaluated and discussed with numerical analysis and suggest that the presented forming technology enables the manufacture of high strength components in accordance with automotive specifications and quality standards.
On-line quality control and tool wear evaluation in trimming process by data analytics techniques
Authors: Garcia-Llamas E. , Castro J. M. Gonzalez , Ramirez G. , Pujante J.
Published: June 2023

Sheet metal is an extremely common form of use in broad engineering sectors and represents the main consumption of steel and aluminum in Europe. All production processes where sheet metal is used require cutting operations. Therefore, it is an extremely relevant procedure, common and of great economic importance in material-intensive sectors such as automotive, construction and engineering. In a competitive environment where the demand for quality increases continuously and using harder to process high-performance materials, online monitoring and quality control become an attractive prospective. In this regard, application of data analytics techniques offers a promising toolset for fast and efficient analysis. This work presents a pilot demonstration of an instrumented sheet metal cutting line that integrates online quality control and predictive maintenance concepts, namely detection of wear in tools as well as problems arising from the raw material and process. Automated sequential cutting was performed using a straight trimming die mounted on a hydraulic press to cut High-Mn TWIP steel strip. Three piezoelectric force sensors were located in the trimming tool, collecting cycle data. Tests performed included studying the effect of blunting on the M2 (1.3343) tool, as well as the influence of correct lubrication. The resulting data were analyzed through the extraction of several parameters from each cycle to correlate die wear-induced force response evolutions with the shear-induced deformation in High-Mn TWIP steel sheets. Extracted parameters were the maximum and minimum force of each cycle and the impulse (integrated force over time) was computed and segmented by plastic deformation and crack contributions. Our analysis show that advanced algorithms can be used to analyze sensor data on an automated installation, revealing OK/NOK conditions and anomalous events.
Application of a neural network for predicting cutting surface quality of punching processes based on tooling parameters
Authors: Schenek A , Görz M , Riedmüller K R , Liewald M
Published: June 2023

Punching represents one of the most frequently used manufacturing processes in the sheet metal processing industry. Thereby, one of the most important quality criteria for such punching processes constitutes the geometric shape of the cutting surface. High cutting surface qualities are usually characterized by the lowest possible edge draw in, a high clean cut, as well as a small fracture surface and a low burr height. In this respect, conventional punching processes can only produce clean cut proportions (CCP) up to 20-50% of the sheet thickness. By means of the so called “concave punch nose design” developed at the Institute for Metal Forming Technology, the geometry of conventional punches could be optimized in such a way that the clean-cut proportion along the cutting surface is significantly increased. The findings reported about in this paper show that the quality parameters of the sheared component edges thereby show highly nonlinear relationships to the tooling and sheet metal material parameters used. In order to quantify these effects, the data from several numerical punching simulations is used to pretrain an artificial neural network (ANN). Input data for the neural network included features of the punch geometry, the size of the clearance, the sheet thickness and the material data of the semi-finished product. The output of the neural network is precise predictions of the achievable cutting surface quality parameters. The experimentally validated findings presented in this paper show that the process design for novel punching processes such as cutting with concave punch nose design is possible, when using a modern machine learning approach.
Formability evaluation based on a constitutive model with stress rate direction dependency considering bifurcation modes
Authors: Oya T , Ito K , Uemura G , Mori N
Published: June 2023

Accurately predicting the fractures that occur in materials during forming not only improves quality, but also reduces the amount of material that is discarded. Therefore, as a key technology for digital transformation to achieve carbon neutrality, it is necessary to improve the accuracy of forming analysis and establish an efficient method for predicting forming limits. Formability assessment is typically performed using ductile fracture criteria or experimental forming limit diagrams (FLDs), which require prior fracture testing. The authors have established a forming evaluation method based on three-dimensional local bifurcation theory as a versatile method that does not require destructive testing. This method can follow abrupt changes in the stress field, such as localized necking, by using a flow rule that takes into account the directionality of the stress rate. In this study, the proposed method is applied to the tensile testing and the forming analysis of a square cup drawing to analytically verify the location and onset time of local bifurcation modes that may lead to fracture.
Local and global forming potential of present dual-phase steel developments
Authors: Beier Thorsten , Woestmann Stefan , Sikora Sascha
Published: June 2023

Modern car bodies are constantly relying higher proportions of high and ultra-high strength steels. In the past, the increase in material strengths led to a conflict regarding the complexity of component geometries. Limits of material formability are reached and compromises had to be made in part design. By integrating application-oriented problems into the material development, these limits are expanded with respect to the given requirements. Within the present study, for several dual-phase steels with a tensile strength ≥800 MPa, practical laboratory tests are presented and their benefits in press shop application. In particular influencing factors on stretch flange formability are presented and discussed for example cutting parameters, anisotropy, time between cutting and forming or the orthogonal strain gradient.
An evaluation method for experimental necking detection of automotive sheet metals
Authors: Pham Quoc Tuan , Islam Md Shafiqul , Barlo Alexander , Sigvant Mats
Published: June 2023

In sheet metal stamping, the occurrence of strain localization in a deformed sheet is considered a failure. As so, sheet metal’s formability is conventionally evaluated using the Forming Limit Diagram (FLD), which separates the principal strain space into safety and unsafety regions by a Forming Limit Curve (FLC). This study presents an evaluation method for detecting strain localization based on Digital Image Correlation (DIC) during the experiment. The commercial DIC software ARAMIS is adopted to monitor the strain-field distribution on the deformed specimen’s surface. A detailed analysis of the proposed method is presented considering Nakajima tests conducted for two automotive sheet metals: AA6016 and DP800. The identified FLC based on the proposed method is compared with that of well-established methods such as ISO 12004:2-2008 and time-dependent methods. For both investigated materials, the proposed method presents a lower FLC than the others.
Edge fracture of the first and third-generation high-strength steels: DP1000 and QP1000
Authors: Li Z , Chang Y , Rong J , Min J , Lian J
Published: June 2023

Advanced high-strength steels (AHSS) have shown profound progress in improving tensile ductility or global formality in the last decades over three generations. For a complete assessment of both the global and local formability, this study aims to characterize and compare the tensile and edge fracture behavior of the first and third-generation AHSS (dual-phase steel and quenching & partitioning steel) with the same nominal strength level of 980 MPa. Uniaxial tensile tests are performed to characterize the tensile properties. Hole expansion tests are conducted with two edge conditions based on separated preparation techniques (waterjet with polishing and punching) to investigate the edge fracture for both materials. The hole expansion ratios and edge fractures are compared between two materials and two edge conditions. It is concluded that the investigated QP1000 has promoted global formability while the DP1000 shows better local formability due to its damage-tolerant and crack-resistant responses.
Strain evolution during hole expansion testing of 800 MPa tensile strength hot-rolled steels
Authors: Plosila P , Kesti V , Kaijalainen A , Vierelä R , Rautio P , Kömi J
Published: June 2023

One limitation of the standardized ISO 16630 hole expansion test is that it provides only one result: limiting hole expansion ratio (HER). In practice, steels with similar HER values can have different cut edge forming behavior due to possible differences in strain localization tendencies. Digital image correlation (DIC) strain measurement during formability testing allows more in-detail analysis of strain-state near the cut edge. In this paper, strain evolution during hole expansion testing was investigated for three 800 MPa tensile strength grade hot-rolled strip steels. The steels were selected to have differences in microstructures and anisotropies of mechanical properties. Two different hole expansion test methods with DIC strain measurement were utilized to investigate different edge loading scenarios: in-plane stretching with a flat-top punch and more out-of-plane stretching with a hemispherical punch. Test holes were prepared according to ISO 16630 standard. In order to examine strain evolution and localization during testing, strains were measured with circle-shape sections around the hole in various distances from the cut edge. Strain localization behavior was investigated in different sheet directions and the effect on the hole expansion ratio was evaluated. Results show considerable differences in the cut edge forming behavior between the investigated materials.
Accuracy of stretch flange formability prediction by considering strain gradient for actual car body parts
Authors: Iizuka E , Okada A
Published: June 2023

The effect of the strain gradient on the stretch flange deformation limit of steel sheets was investigated by hole expansion tests under various forming conditions and by FEM forming simulations. The hole expansion ratio was changed by changing the initial hole diameter and punch shapes. This study clarified the fact that deformation limit strain increases, as it does not depend on the initial hole diameter or punch shape, and thus the strain gradient increases. The deformation limit thickness strain of the stretch flange portion could be changed by changing the strain gradient. These results suggest that the formability of the stretch flange deformation area should be determined from not only the maximum principal strain but also the strain gradient. Then, the accuracy of stretch flange formability prediction by considering the strain gradient for actual car body parts in mass production was investigated. The maximum principal strain and the strain gradient of the parts were calculated by FEM or measured in the press part. These results suggest that the formability of the stretch flange deformation area for actual car body parts could not be predicted by not only the maximum principal strain or the thickness reduction, but also the conventional FLD. This investigation verified the accuracy of stretch flange formability prediction by considering the strain gradient for actual car body parts.
Forming of a cylindrical cup in 7075-T6 under warm temperature conditions
Authors: Royne S , Laurent H , Maillard A
Published: June 2023

The high mechanical properties of aluminum alloys are very interesting for reducing the weight of parts in the automotive sector. However, a formability issue prevents the use of these alloys at room temperature especially for complex shapes where part failure occurs before full drawing. The use of a warm forming process, which consists of heating the part between 150°C and 250°C for aluminium alloys, allows to increase formability and therefore to perform complex shapes. In this study, the forming of a cylindrical cup in 7075-T6 is carried out at 200° C in two steps by two successive reductions in the diameter of the blank. Numerical simulations of these two forming steps are performed with Abaqus. The influence of friction coefficient is analysed in these two forming steps by comparing the evolutions of punch force.
Determination of Edge Fracture Limit Strain for AHSS in the ISO-16630 Hole Expansion Test
Authors: Barlo A , Sigvant M , Kesti V , Islam M S , Pham Q T , Pilthammar J
Published: June 2023

With the increased demand for application of sustainable materials and lightweight structures, the sheet metal forming industry is forced to push existing materials to the limits. One area where this is particular difficult is when it comes to assessing the formability limit for sheet edges. For decades, the ISO-16630 Hole Expansion Test (HET) has been the industry standard for expressing the edge formability of sheet metals through the Hole Expansion Ratio (HER). However, in recent years, this test has been criticized for its high scatter in results for repeated experiments. This scatter has been suspected to be caused by the operator-reliant post-processing of the test, or variations in the cutting conditions for the different test specimens. This study investigates the impact of shifting the evaluation point of the test from the through-thickness crack to the onset of surface failure on the reported scatter, as well as performs inverse modeling of the Hole Expansion Test to obtain an edge limit strain value.
The Investigations on Formability of Tantalum RO5200 Thin Foils: Bio-Material.
Authors: Kulkarni Omkar , Kakandikar Ganesh
Published: June 2023

Tantalum RO5200 (TaRO5200) is an excellent and new emerging Bio-material with wide applications. The most important property of TaRO5200 is Osseointegration which helps in integration of direct structural and functional connection between living bone and the surface. The process of forming in at actual is a plastic deformation where in the material is transforming in permanently is some shape without occurrence of any type of defect of failure. Few different types of failure enlisted are local necking, wrinkling, earing etc. In recent days transforming from macro level to micro level is now trending part of life. The most difficult part in moving towards micro level forming which means forming sheets under 100 microns thickness, is control over process. Hence this gives significance and rise for the investigations over forming at micro level and prediction of mechanical and formability properties at micro level. This research work posited in this paper focusses on the plotting of Forming limit curve (FLC) which is one of the methods to investigate formability of ultra-thin foil of TaRO5200 with sheet thickness 80 microns (μm). The experiments performed for FLC plotting were based on the Nakkajima test following the ASTM 2218-14 standards. The FLCs are plotted experimentally and via numerical simulation as well which in comparison shows a good agreement. The variance obtained between experimental and numerical simulation is up to 15%. Which in another words can be stated as numerical simulation is 15% safer in design than the experimental work. The novelty of the work lies in testing of the bio material and defining FLC by performing experiments via newly designed tool for the specific sheet thickness of 80 μm following the ASTM standards. Microstructural study is also performed on the specimen prior and after forming test to analyse and understand the physics along with mechanism of the material in test. The material behaviour is also explained in the microstructural study section.
Effect of the intercritical annealing in the formability and microstructure of a medium Mn steel sheet
Authors: Hernández-Rivera J L , González-Castillo A C , Ramos Azpeitia M O , Garay-Reyes C G
Published: June 2023

A medium Mn steel (MMS) was cast by employing a vacuum induction furnace. After that, the steel was hot rolled (HR) in order to achieve a final thickness of 1.4 mm. The microstructure of the sheet was found to be composed of martensite and a little amount of austenite, the Ultimate Tensile Strength (UTS in this processing condition was close to 1600 MPa and a negligible elongation was found. An intercritical annealing (IA) heat treatment was applied to the steel to promote the austenite reversion and increase its amount and stability. Previous thermodynamic simulations and experimental results were used to determine the temperature and time parameters of the IA. After the steel was subjected to this heat treatment, it exhibited an elongation close to 35% and an UTS close to 1100 MPa. Bendability testing was carried out in that condition in order to correlate it with the microstructural changes in the sheet. It was found that the critical bending angle was higher in the IA condition in comparison with the HR state.
Experiments and simulations of the drawing envelope of commercially pure aluminum
Authors: Carter Adrian J. , Chen Kelin , Korkolis Yannis P.
Published: June 2023

The range of blank-holding force (BHF) for which deep drawing of AA1100-H24 is successful is investigated using a combination of experiments and simulations. The experiments involve circular blanks of three different diameters: 35 mm, 37 mm and 40 mm. The thickness of the blanks is 0.51 mm. These are drawn with a punch of 20 mm diameter, i.e., at drawing ratios of 1.75, 1.85 and 2.0, respectively, using a custom, modular forming apparatus where the BHF can be controlled at will, between 0 and 2,400 N. The experiments are performed in an Instron 8872 servo-hydraulic frame that allows precise measurements of the punch force and displacement. The working envelopes are determined experimentally in the space of BHF and draw depth, which can be categorized into three regimes: wrinkling, safe and tearing. It is found that grey zones exist between the three regimes. These experiments are then simulated in Abaqus/Standard, using two types of elements: axisymmetric and shell. In the latter case, plastic anisotropy is introduced, using the Yld2000-2D anisotropic yield function. Wrinkling and tearing failure are triggered by inducing suitable geometric imperfections. It is shown that the models are able to reproduce the experiments well. This serves as a verification of the modelling framework, which can then be used for the simulations of more complex forming processes.
Experimental characterization and prediction of forming limit diagrams of PHS1800 during hot stamping
Authors: Samadian Pedram , He Ruijian , George Ryan , Butcher Clifford , Worswick Michael J
Published: June 2023

The use of press-hardening steels (PHSs) in automotive bodies creates the opportunity of producing thinner, higher-strength components. PHS1800, an Al-Si coated PHS grade with ultimate tensile strength of around 1.8 GPa after hot stamping, is a candidate material for vehicle anti-intrusion applications. The current study aims to investigate the formability of this steel during the hot-stamping process. A custom Marciniak punch test and in situ digital image correlation (DIC) techniques were used to determine the in-plane forming limits of this steel during quenching from an austenitic temperature. The carrier blank thickness and geometry were exploited to quench the surrounding material of the specimens while promoting localization in their central regions. Approximately linear strain paths ranging from uniaxial to biaxial stretching were obtained in the tests while avoiding friction and out-of-plane bending. The forming limit curves (FLCs) of the material under various hot-stamping conditions were then predicted using the Marciniak-Kuczyński (MK) model, taking into account the temperature and strain-rate histories. The predicted limit strains were in good accord with the measured data.
Strength enhancement and uniform strain distribution through cross route-constrained groove pressing
Authors: Kumar Sunil
Published: June 2023

Constrained groove pressing (CGP) is one of the severe plastic deformation techniques for sheet metals to impose large plastic strain and produce ultrafine-grained (UFG) structures without any change in dimensions. Cross route-constrained groove pressing (Cross-CGP), an advanced version of the conventional CGP process, involves two CGP cycles with an equivalent strain of 2.32 per cycle where the square sample is rotated by 90° after performing every cycle of CGP. The strain path in the sheet during conventional CGP and cross-CGP significantly affects the homogenization of mechanical properties. Sheets of low carbon steel are processed through conventional-CGP and cross-CGP routes. The ability to sustain the maximum strain has been increased in the cross-CGP process due to uniform strain distribution. The tensile strength and hardness in the sheet processed through cross-CGP are higher than that of conventional CGP, especially at higher pass numbers. Tensile behavior and hardness in two different orientations (parallel and perpendicular to the groove direction) have been found to be almost the same in the cross-CGP processed sheet.
Evaluation of hole expansion ratio of ultra-high strength martensitic steels produced with various processing routes
Authors: Hannula J. , Plosila P. , Kaijalainen A. , Suikkanen P. , Kömi J.
Published: June 2023

Hole expansion ratio of hot rolled ultra-high strength martensitic steels with tensile strength around 1000 MPa was evaluated. Steels were produced with direct quenching and traditional reheat and quenching processes with final thickness of 3 mm. Achieved yield strength values (Rp0.2) varied between 918 – 1068 MPa depending on the processing route. Mean hole expansion ratios (HER) in direct-quenched (DQ) and direct-quenched and tempered (DQT) conditions were between 22 – 36 %, and no clear improvement was seen after tempering treatment compared to quenched variant. HER values for reheat and quenched (RQ) and reheat, quenched and tempered (RQT) variants were between 31 – 49 %, and the highest values were achieved with RQT steels, which were tempered at 600 °C. Based on the field emission scanning electron microscope with electron backscatter scanning diffraction (FESEM-EBSD) analysis/characterization of martensite grain size, more uniform grain structure was discovered in RQ steels, which could be the reason for improved HER properties. HER values were also compared to tensile test results (uniform elongation, true thickness strain), and formability maps were constructed. However, only minor correlation was found between HER and true thickness strain values.
Development of a novel in-situ measurement method for thermo-mechanically coupled material characterization of high-strength aluminum alloys
Authors: Rigas N , Garcin T , Kuball C-M , Merklein M
Published: June 2023

High-strength aluminum alloys are more and more used for safety and crash-relevant components due to their advantageous density-to-strength ratio. By using thermal-supported forming strategies, failure-free deep drawing is possible for these materials. In this context, the hot form quench process (HFQ®) has shown to be a promising thermally-assisted forming strategy. By using locally tempered forming tools, the production of tailored components with different mechanical properties is possible. However, material characterization and process design with conventional characterization methods are quite challenging in this context. A new approach is the use of ultrasound-assisted material characterization in combination with a thermo-mechanical simulator. Thereby it is possible to perform an in-situ material characterization. So far, this technology is mainly used for steel materials. In this contribution, the potential of an adapted measurement strategy for high-strength aluminum alloys is presented. For this purpose, the influence of different measurement parameters on modified samples and the resulting measurement signal is investigated. With the help of this study, new standards are set for time-bound material characterization under thermo-mechanical stress. As a result, thermally-assisted forming methods can be designed more efficiently and faster in the future.
Characterization of the Mechanical Properties of Selectively Embossed Sheet Metal Materials Under Multi-Axial Loads
Authors: Heinzelmann Pascal , Briesenick David , Liewald Mathias
Published: June 2023

The application of embossed structures close to the sheet surface allows for work hardening to be introduced into sheet metal materials, leading to an improvement in their mechanical properties. So far, this was demonstrated in previous research work via tensile tests with differently embossed dual-phase steel specimens. Since tensile tests only reproduce uniaxial loading of the sheet metal material, no conclusions can yet be drawn about the property modification that can be achieved by near-surface embossing concerning real-life, multi-axial loading scenarios. To get deeper knowledge about the deformation behaviour of embossed components, it is important to consider multi-axial load cases. In the investigations reported in this paper, a multi-axial load case was realized by testing embossed bending specimens of DP600 and DP800 using a three-point bending device. The tests showed an overall improvement in the maximum bending force needed for the three-point bending test due to embossing of the materials investigated. Further, the tests indicated that lower-strength materials get more influenced by embossing than higher-strength materials. By simulating the process of embossing the bending specimens and the subsequent three-point bending test, an even deeper understanding of the material property modification could be generated.
Micro incremental forming of thin SS304 foils and its microstructural study
Authors: Mahajan Peeyush , Patil Jeet , Mishra Sushil
Published: June 2023

Micro-forming of thin foils is challenging due to the size effect, friction effect, and tool design. The conventional macro-forming techniques cannot be directly applied to the thin foils. The incremental forming process (ISF) can be used for thin foils since it possesses higher formability compared to the conventional process. Hence, µ-ISF (micro incremental forming process) experiments were conducted on thin foils of SS304 stainless steel having 50, 100, and 200 µm thickness. As-received foils were further annealed at 950°C with a holding time of 20 mins to achieve strain-free microstructure. The Taguchi L18 orthogonal was applied to optimize the initial processing parameters for, µ-ISF experiments. Using the initial optimized parameters µ-ISF experiments were performed for all the thickness sheets up to the maximum wall angle. It was observed that the higher tool diameter and the lower step depth give the minimum roughness value in the deformed sheet. The tearing mode of failure was observed due to the formation of strain-induced martensite in the deformed sheet. The microstructure and bulk texture analysis relate the orientation and twin fraction with the deformation behaviour. From the texture evolution, it was observed that the brass {110} <112>, Cube {100} <001>, and goss {110} <001> texture component has a greater influence on the formability of SS304 stainless steel thin foils.
Simulation of deep drawing of dual phase steel sheets incorporating tribological behaviour predicted by advanced friction modelling
Authors: Shrivastava Archit , Ravi Kumar D
Published: June 2023

In a deep drawing process, friction at the sheet metal-die contact interface affects the material flow in the flange as well as at the die entry affecting product quality significantly. The accuracy of predicted drawing force and thinning in deep drawing simulation strongly depends on friction modelling. The Coulomb friction model with a constant coefficient of friction is generally assumed in simulations. In reality, the actual friction coefficient depends on process variables such as local contact pressure, relative sliding velocity, and strain in the sheet material. In this work, an approach is presented for deep drawing simulation of dual phase (DP600) steel sheets incorporating the effect of these variables on the friction coefficient. Strip drawing tests under conditions similar to that exist in the flange area during deep drawing have been carried out. Deep drawing simulations have been performed using two friction models taking into consideration the variation of friction coefficient with respect to pressure and velocity. The predicted punch force and thickness variation are validated using deep drawing experiments. A considerable improvement in the accuracy of predicted results has been observed when compared to a constant coefficient of friction.
Three Industrial Cases of Sheet Metal Forming Simulations with Elastic Dies
Authors: Pilthammar J , Sigvant M , Islam M S , Schill M , Sjöblom S , Sjöblom V , Lind M
Published: June 2023

Previous research and experience points to many advantages if sheet metal forming is simulated with elastic dies. Some areas that are enabled by simulations with elastic dies are virtual spotting, improved digital twins, and improved production support. A promising method was selected from the literature, and after important modifications it is deemed to be fast and robust for simulating industrial sized dies. The method consists of meshing die solids with a coarse mesh to represent the structural behaviour of the die. The forming surfaces are then represented by a fine shell mesh connected to the solid mesh by tied contacts with an offset. With additional modifications to reduce solver time this yields a robust and flexible way of modelling sheet metal forming with elastic dies. There is an increase in preprocessing and simulation time compared to using rigid tools, but industrial dies can now be modeled within an hour and solved within a working day. It is also easy to update the model by replacing separate parts such as die solids or forming surfaces. One of the main criteria in favor of the selected approach is the realistic modeling of blankholder and cushion systems. In this paper simulations of three industrial cases are demonstrated: one case of virtual die spotting and two cases of production support. The three cases demonstrate the importance and potential of using elastic dies during virtual die tryout, production support, and for cases like digital twins and production control.