bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Application of Metering Instrument for Well-Head Metering in Block 75 of Sulige Gas Field
Authors: Wang Li Na , Liu Li Jun , Wang Wan Xun , Qin Shan Yang
Published: June 2013

Along with large scale application of cluster wells in Sulige gas field, the common low pressure flow meter can not be used in metering single well production with connecting wells in series. For this reason, we have developed a flow metering instrument of natural gas, which has the features of high static pressure, low differential pressure and high precision. Installed at the high pressure end of gas production wellhead, the instrument can bear 40Mpa static high pressure and has the features such as low pressure loss, broad measuring range, small temperature drift, high precision, long service life, solid, low cost and so on. With required measurement accuracy and resistance to pressure, which have been verified by the wide application, the instrument gave a solution to metering single well production of cluster wells.
Development of Synchronized Biomechanics Sensors Detection Software
Authors: Taha Zahari , Deboucha Abdelhakim
Published: June 2013

Biomechanics is a relatively new discipline where engineering and mechanics principles are applied to the understanding of biological organism. Biomechanics simply taking place to study the mechanics of tissues, joints, human movements, circulatory system and digestive tract. One of the most challenging applications of biomechanics is in the field of sports and sports medicine in which the prevention of sports injuries is highly required. To understand and to diagnosis tissues abnormalities, mechanics of neuromuscular control, mechanics of cardiovascular function, a synchronizing interface with multi biomechanics sensors is developed in this effort. The interface shows different data recorded from several sensors during a physical activity made by the subject. These synchronized and combined data will help the user to make a specific diagnosis of the subject health. Moreover, these data will give an insight understanding on the correlation between variety aspects of biomechanics.
Fast Algorithm with Improved Circular Correlation Method for GPS Signal Acquisition
Authors: Li Yan Min , Yi Qing Ming , Shi Min
Published: June 2013

In order to improve acquisition speed and carrier frequency accuracy, a fast algorithm to acquire GPS signal is proposed. Signal-to-Noise Ratio is improved by coherent integration and non-coherent integration. The advantages of serial sliding algorithm and circular correlation algorithm are combined to achieve high carrier frequency accuracy. Removing the information of C/A code makes serial search from two-dimensional to one-dimensional to achieve less computation. Simulation shows weak signal of-30dB S/N is successfully acquired. The error of carrier frequency is controlled within 50Hz. So the data processing efficiency for the tracking loop is greatly increased.
Gait Planning and Simulation of the JQRI00 Quadruped Robot
Authors: Bian Xin Gao , Lu Wei Li , Zhu Deng Lin
Published: June 2013

More and more research works have been focused on the quadruped walking robot because of its flexibility for the dangerous and complex environment. The Straight and turning gaits of a quadruped robot (JQRI00) were planned by the principle of stability margin. The virtual prototype model of the JQRI00 was constructed, and the results of the simulation and analysis of the designed gaits using ADAMS simulation software indicate that the straight and turning gaits are feasible. Moreover, the S-curve used as displacement control makes the robot more stable.
High Performance Drive Design for Hybrid Stepper Motors
Authors: Cao Fa Hai , Lv Jian Ping
Published: June 2013

A new frequency-voltage modulation drive technique is proposed and analyzed for the use of stepping motor. Hardware circuit and the current compensation control method are given in the article. STM32 MCU control the PWM switch power, and combine L6384 to drive the MOSFET tube which consisting of H-bridge driver circuit. It simplifies the power drive electronic circuit. A high performance drive design about the best of drive curve is used through the analysis and study of the current closed-loop control. It will significantly improve the stability in low frequency and the torque frequency characteristic in high frequency, and the design can be used for high-power automation equipment.
Influence of Silicon Controlled Rectifier Voltage Regulation Device under DDC-Temperature Control
Authors: Lu Ya Ping , Song Tian Lin , Liu Hai Qing
Published: June 2013

In the boiler heating control device of combining DDC and the silicon controlled rectifier voltage regulation device, there are phase shift trigger, pulse width modulation (PWM) and cycle wave cross zero trigger (CYC). Under the different silicon controlled rectifier voltage regulation devices, there are different influences for DDC. It makes the best of the cycle characteristics of the alternating current (AC) for the cycle wave cross zero trigger (CYC). For DDC - temperature control system, there are advantages of high control accuracy, less interference and power source pollution.
Multiobjective Topology Optimization of Multi-Input and Multi-Output Compliant Mechanisms with Geometrically Nonlinearity
Authors: Li Zhao Kun , Zhang Xian Min , Bian Hua Mei , Niu Xiao Tie
Published: June 2013

Multiple degree-of-freedom compliant mechanisms are widely used in the fields of micro-positioning and micro-manipulation. This paper deals with multiobjective topology optimization of multi-input and multi-output compliant mechanisms undergoing large deformation. The objective function is defined by the minimum compliance and maximum geometric advantage to meet both stiffness and flexibility requirements. The suppression strategy of input and output coupling terms is studied and the expression of the output coupling terms is further developed. The weighted sum of the conflicting objectives resulting from the norm method is used to generate the optimal compromise solutions, and the decision function is set to select the preferred solution. Geometrically nonlinear mechanism response is calculated using the Total-Lagrange finite element formulation and the equilibrium is found using an incremental scheme combined with Newton-Raphson iterations. The solid isotropic material with penalization approach is used in design of compliant mechanisms. The sensitivities of the objective functions are found with the adjoint method and the optimization problem is solved using the Method of Moving Asymptotes. Numerical examples of multiple inputs and outputs are presented to show the validity of the new method. Simulation results show that the compliant mechanisms can be deformed in the desirable manner and the coupling output displacements are suppressed significantly by using the presented method.
Performance Assessment Model for Highway Electromechanical System
Authors: Cui Han Jing , Zhu Chuan Zheng , Wang Lei
Published: June 2013

Based on the research of the law of performance of electrical and mechanical equipments, the characteristics of highway electromechanical system is studied. According to current quality inspection and evaluation standards, the hierarchy criteria system is deduced, and the importance degree of each criterion is calculated according to the responses on the question form by Delphi method. By membership functions, each criterion is given the weight which is normalized as the importance degree for the hierarchy level. Then, the fuzzy comprehensive assessment model is established with judgment matrix.
PID Control Strategy of Vehicle Active Suspension Based on Considering Time-Delay and Stability
Authors: Yan Guang Hui , Wang Shao Hua , Guan Zhi Wei , Liu Chen Fu
Published: June 2013

The stability conditions of 1/4 vehicle active suspension with time-delay were deduced by the theory of Routh-Hurwitz stability criterion and the critical instability time-delay was discussed and calculated. Compared with PID control method of without time-delay the simulation results show that when the critical time-delay is 0.153s, the amplitude range and its root mean square value of spring load quality vertical acceleration were increased 1.2 times or so and the system was being on the critical stability. The calculation and simulation results proved that the theory of Routh-Hurwitz stability criterion laid a foundation for the design and instability mechanism of active suspension.
Research and Application of Weighing Low Temperature and Mobile Metering Device
Authors: Zhang Sheng Li , Luo Yi , Wang Li Na , Li Chun Yan , Sun Hao , Xie Wei , Liu Wen Sheng , Wang Jin Xiu
Published: June 2013

The accuracy and stability of dynamometer diagram measurement are key assessment index for this technology. At present, separator measurement data is mostly taken as comparison benchmark for evaluation of dynamometer diagram measurement in Huabei Oilfield, resulting in large error in comparison. In view of existence of gas, water and pressure, gas/liquid separation of produced fluid is followed by separating measurement of gas and liquid. Gas and liquid mixture are measured by flow meter and weighing method, respectively. Higher precision measurement data is obtained. In combination with PLC programming control, this technology can realize fully automatic and continuous measurement. This device has been applied in 126 wells in Huabei Oilfield. Assisted by dynamometer diagram measurement software, point-to-point calibration and correction method of yield measurement is improved[.
Research of Large Excavator Multidimensional Intelligent Vibration Monitoring and Fault Diagnosis System
Authors: Li Ying , Ru Zheng Hua , Ru Yi
Published: June 2013

Excavator vibration speed not only directly affects the life length of excavator, but also contains security risks which even relate to the life safety. This article focuses on the Large Excavator Multidimensional Intelligent Vibration Monitoring and Fault Diagnosis System, which allows the excavator to perform vibration detection and warning of the key components under normal using state, and realizes online monitoring as well as remote consultation.
Research of the Control Method for the Uniformity of Insulation Layer on Communication Cable
Authors: Lv Yan , Wang Hui Hui , Tao Xue Heng
Published: June 2013

The uniformity of thickness of insulation layer on communication cable is an important technique index to guarantee the communication cable has good mechanical and physical properties. Therefore the control method for uniformity of insulation layer on communication cable is desiderated to be researched. In this paper, a control system which took two laser displacement sensors as a detection unit, a CS1G-H PLC of OMRON as a central control unit, two servo drivers and two servo motors of the SMARTSTEP-A series of OMRON as a servo system, a touch screen as a man-machine interface and applied PID and PDFF control algorithms was designed. The system was proved that the operation was reliable and the desired requirements could be achieved based on laboratory simulation and debugging.
Research on Automatic Packing Machine’s Manipulator of Amorphous Silicon
Authors: Wu Zhuo , Liu Jin Tao
Published: June 2013

Automation of the domestic existing amorphous silicon solar cell production lines has been already realized but packing is still achieved by artificial. So labor intensity is serious and the cost is high. In order to overcome these problems, through the analysis of the packing process, a kind of automatic packing machine is designed. As the most important part of automatic packing machine, automatic packing manipulator, driven by servo motor and cylinder and controlled by PLC, uses electromechanical integration technology to complete cell steering and into the box so as to save manpower and reduce the production cost.
Research on Electronic Differential Control Method of Electric Vehicle with Motorized Wheels Based on Adhesion Coefficient
Authors: Long Ying Chun , Li Li Fu
Published: June 2013

This paper presents an electronic differential control strategy based on equal adhesion coefficient, it makes electric vehicle (EV) with two dual-motorized-wheels achieve differential by distributing and controlling the driving torque. First, six degree-of-freedom (6-DOF) vehicle dynamic model was set up and electronic differential system based on permanent magnet synchronous motor (PMSM) vector control was designed, then the simulation of differential control method with Matlab/Simulink was performed. The results show that when the high-speed vehicle steering in the low road adhesion coefficient, the electronic differential control method based on the principle of equal adhesion coefficient can keep two driving wheels’ adhesion coefficient utilization ratio the same, avoiding single wheel skid and improving the steering stability.
Research on Fault Analysis and Fault Diagnostics Technology for Large-Size Equipments in Stopes
Authors: Zhang Bao Cai , Shao Meng , Du Guo Ming
Published: June 2013

At present,the main equipments is electric shovels of Dagushan Iron Ore Mine, Due to a variety of factors, inevitably, there are many faults, overcurrent, overvoltage and overload are the ones with highest incidence. at the same time, the lifting system, push-press system, rotation system on the electric shovel and the overcurrent protection system of the main transformer will make appropriate actions and instantaneously shut down the electric shovel. In this article, microcomputer as its control core, It can comprehensively take use of equipment status monitoring technology, test analysis technology, signal processing technology, embedded technology, etc., carry out analytical reasoning for the equipment status information during operation process of electric shovel such as current, voltage, etc., according to the simulation experiment and operation inspection and test, the large-size equipment diagnosis & analysis device is completed for stopes has the advantages such as full-featured functions, convenient and reliable operation, considerable economic benefits.
Interactive Buckling Tests of Externally Pressurized Stiffened Bent Pipelines
Authors: Hoseinzadeh V. , Showkati H.
Published: June 2013

The paper reports an experimental study on the collapse of long uniformly pressurized ring-stiffened bent pipelines. Bending in the presence of external pressure is experienced by pipelines during their installation and operation. The buckling aptitude of shells is dependent on two leading geometric ratios, i.e. the length to radius and radius to thickness. In this paper, four different ring-stiffened steel pipeline specimens were tested to collapse. The evolution of the specimens behavior that has been recorded in the presence of a uniform external pressure is outlined. A thin-walled pipeline is sensitive to buckling phenomena when it experiences locally a compressive stress. It is often considered that its behavior under bending is rather similar to pure compression, but very few are the experimental investigations that precise the real behavior of it. A comparison of experimental data to empirical formulae and design recommendations is finally achieved. Consequently, it has been found that with using ring stiffeners the structure behavior against the combination of loads is improved in all loading paths. Also it has been found that buckle propagation in all manners occurs suddenly and dynamically and the amount of initial bending moment is not serious in defining the number of buckling modes. Also, the considerable effects of a longitudinal spot weld line on the buckling strength and mode shapes are verified.
Finite Difference Approximations of Elasto-Plastic Bending Problems: Layered Approach and Error Estimates
Authors: Davoudi Mohammad Mahdi , Öchsner Andreas
Published: June 2013

The finite difference method is applied to derive approximate solutions for the elasto-plastic bending of Euler-Bernoulli beam problems. The investigations are restricted to a simple exemplary configuration, i.e. a straight cantilevered beam with constant rectangular cross-section and linear-elastic/ideal-plastic material properties, loaded by a constant distributed load. Only finite difference approximations of second-order accuracy are considered and special emphasis is given to the influence of the load step, the number of layers, and the number of nodes. Based on comparisons with the analytical solution, clear recommendations can be given on the required parameters to obtain a certain accuracy in the numerical approach.
Modelling of Steel Creep at High Temperatures Using an Implicit Creep Model
Authors: Torić Neno , Harapin Alen , Boko Ivica
Published: June 2013

The paper presents the numerical procedure for modelling the behaviour of steel structures at high temperatures using a newly developed implicit creep model. This implicit creep model uses the calculated creep strains to modify the material stress-strain curves, thus implicitly taking into account the effect of the developed creep strain. The newly calculated stress-strain curves are modified by stretching the initial temperature-dependent stress-strain curves using the calculated values of the creep strain which depend on the level of temperature and stress that the section of structure is being exposed to during fire. The implicit numerical procedure has been implemented in a previously developed numerical model for predicting the behaviour of structures under fire. In order to test the validity of the newly developed implicit creep model, an in-house fire experiment was performed. Results of the experiment have shown a good agreement with the model predictions indicating the validity of the developed implicit numerical procedure.
Selection of ILs for Separation of Benzene from n-Hexane Using COSMO-RS. A Quantum Chemical Approach
Authors: Kurnia Kiki A. , Abdul Mutalib Mohamed Ibrahim , Man Zakaria , Bustam Mohammad Azmi
Published: June 2013

onic Liquids (ILs) provide an alternative green solvent for separating aromatic from its mixture with aliphatic hydrocarbon. The present work demonstrates the screening of potential IL for separation of benzene (aromatic) from n-hexane (aliphatic) using COSMO-RS. A total of 10 imidazolium based cations and 52 different anions resulting in 520 possible combinations of ILs were studied. The COSMO-RS was used to theoretically calculate the activity coefficient at infinite dilution (γ) for benzene and n-hexane in each of the ILs. Consequently, from the activity coefficient (γ) value, the capacity (C) and selectivity (S) at infinite dilution for each ILs with regards to the benzene/n-heptane separation were calculated. The Performance Index (PI) which is the product of the capacity (C) and selectivity (S) is then determined and compared against sulfolane as the benchmarking solvent, used widely by industry for the separation of benzene and aliphatic hydrocarbon. The result showed 20 ILs with C, S, and PI value higher than sulfolane thus making them as potential candidate for the separation application.
A Comparison of Tensile Strength and Impact Energy of Austempered versus Step Quenched 4340 Ultra High Strength Steel
Authors: Safi Seyed Majid , Brooghani Seyed Yousef Ahmadi , Amirabadi Hossein , Khalili Khalil , Givi Mohamad Kazem Besharati
Published: June 2013

This study was conducted to determine if austempered 4340 steel had different mechanical properties compared to step quenched 4340 steel. Tensile strength and impact energy was determined at room temperature under identical test conditions. The specimens were cut from a bar with 25 mm diameter and austenitized at 800°C for 60 min and followed by quenching at 430°C for the high austempering temperature to achieve the upper bainite morphology and at 360°C for the lower austempering temperature to achieve the lower bainite morphology. In the case of step quenched, the specimens were first austempered at 430°C and then austempered at 360°C to achieve the mixed structure of upper bainite and lower bainite morphology. The another set of specimens for step quenching, after austenitization were quenched to below Ms (martensite start temperature), followed by heating at 400°C to achieve the mixed structure of tempered martensite and lower bainite and 500°C to achieve the mixed structure of tempered martensite and upper bainite. It is also shown that the best combination of strength and ductility can be achieved by the mixed structure of tempered martensite and lower bainite that has been suggested in this investigation.
Effect of the Shear Force on the Failure of Spatial Concrete Framework Structures
Authors: Radnić J. , Harapin A. , Markić R. , Grgić N. , Sunara M. , Buzov A.
Published: June 2013

Firstly, the previously developed numerical model for static analysis of spatial concrete frame structures is briefly described. In this model, cross-sections of structural elements can be of arbitrary shape and formed by various materials, with arbitrary normal stress normal strain relations. This model only includes the effect of normal stresses on the structure failure. Here, it was improved by including the effect of shear forces on the failure of reinforced concrete beam elements. Shear bearing capacity of reinforced concrete section includes the concrete capacity, as well as the shear bearing capacity of longitudinal, transversal and inclined reinforcement bars. The developed numerical model and appropriate software were verified on experimental shear test of a concrete beams. Good agreement was obtained between the experimental and the numerical results. However, further verifications of the presented numerical model are needed.
Similar and Dissimilar FSWed Joints in Lightweight Alloys: Heating Distribution Assessment and IR Thermography Monitoring for On-Line Quality Control
Authors: Forcellese Archimede , Martarelli Milena , Pandarese Giuseppe , Simoncini Michela
Published: June 2013

The heating distribution assessment on similar and dissimilar friction stir welded joints in AA6082 and AA5754 aluminium alloy sheets was investigated. The FSW experiments were carried out using constant rotational and welding speeds of 1500 rpm and 60 mm/min, respectively. Temperature was locally measured by means of K-type thermocouples inserted into thin grooves located on the bottom side of the sheets, in fixed positions, very close to the welding line. It was observed that the mechanical properties of joints are related to the heat distribution. In order to obtain a completely non intrusive temperature monitoring, that was able to follow the process dynamic, a non-contact measurement system based on infrared thermography was also developed. Such system, used for the experimental evaluation of temperature on the upper surface of the joints, is also able to detect the presence of flow defects with a non-destructive method, demonstrating its effectiveness as a diagnostic instrument for the on-line quality control of welded joints.
The Friction Stir Welding of Cylindrical Components
Authors: Bruni Carlo , Zitti Saverio
Published: June 2013

The present research activity aims at studying different conditions for the circumferential friction stir welding of cylindrical components in aluminium alloy. Different parameters have been considered, such as the rotational velocity of the tool, the tangential velocity of the cylindrical elements and the number of welding passes. The obtained data have been analysed and the strength of each joint modelled. It has been observed a relevant effect of the combination between the rotational velocity of the tool and the tangential velocity of the cylindrical components on the strength of the joint.
Analysis of Metallic Materials Behavior during Severe Loadings Using a FE Modeling of the SHPB Test Based on a Numerical Calibration of Elastic Strains with Respect to the Raw Measurements and on the Inverse Analysis Principle
Authors: Gavrus Adinel , Bucur Florina , Rotariu Adrian , Cănănău Sorin
Published: June 2013

The complex loading paths of non-conventional or rapid forging processes, especially as regards the important gradients of the plastic strain and strain rate characterizing the material deformation, require a reliable knowledge of the rheological constitutive equations. Some recent studies propose adequate phenomenological formulations taking into account the corresponding local physical mechanisms and the sensitivity of the true stress with respect to all mechanical variables. At the same time important scientific efforts have been focused in order to identify correctly all the constitutive law parameters, using adequate mechanical tests and robust numerical tools based generally on the inverse analysis principle. It is known that this new method requires building of a rigorous and adequate experimental space, using data obtained from loading conditions close to the industrial forming process. Then to explore high variations of plastic strain and strain rate, one of the most suitable tests are based on high speed hydraulically press and on the Split Hopkinson Pressure Bars test (SHPB). Consequently this paper propose to improve the experimental data accuracy obtained from the SHPB device by using finite element simulations of the entire high speed mechanical experiment together with the description of the inverse analysis strategy applied in order to analyze the thermo-mechanical constitutive behavior of metallic materials behavior and to identify the corresponding rheological parameters. The first part of this study will be dedicated to a short description of the experimental SHPB test analysis and to the analysis of the measurement data which can be used to describe the real mechanical loadings of the specimen. A new experimental calibration method of the acquisition signals, based on the finite element modeling of the elastic bars deformation during an impact without specimen, will be detailed. Using ABAQUS and CAST3M software, this method is validated from the comparison of the elastic strains variation obtained by the numerical simulations. In a second part will be detailed the inverse analysis strategy together with a real application concerning the rheological behavior of an aluminum alloy using a “dumbbell” specimen during a high speed upsetting test starting from a proposed constitutive relationship. Finally, special “cap” geometries of the material sample will be analyzed during a SHPB compression test in order to understand the feasibility of the proposed method to expand the material constitutive behavior identification to severe loadings. It is then shown the capacity to describe deformation path close to the rapid manufacturing processes and high speed machining.
On the Selection of Active Slip Systems in Rate Independent Crystal Plasticity
Authors: Orthaber Markus , Antretter Thomas , Gänser Hans Peter
Published: June 2013

Non-uniqueness of the set of active slip systems is a crucial issue in crystal plasticity. To avoid this problem one may perform viscoplastic regularization. This introduces a certain rate dependency, while many crystals are known to behave rate independently. One would require very low viscosity parameters in the regularized model to resemble the experimental behavior of rate independent crystals, which in turn entails numerical difficulties. Furthermore, no direct approach is known to model deformation banding using viscoplastically regularized models. Hence, to adequately treat rate independent crystal plasticity an alternative method is needed. The proposed method, Maximum Dissipation Crystal Plasticity (MDCP), achieves uniqueness by selecting the set of active slip systems according to its dissipation. In a finite element calculation, a system of coupled quadratic equations is solved at every integration point to define the material behaviour. This approach is formally equal to the method of incremental energy minimization recently proposed by Petryk et al. It can be shown that a viscoplastically regularized model is a limiting case of MDCP, giving similar results when cross hardening becomes negligible. Nevertheless, recent 3D dislocation dynamics calculations by Devrince et al. show that cross hardening in fcc crystals is far more important than self hardening. In such cases MDCP gives results distinctly different from its rate dependent counterpart. Fewer slip systems are selected by MDCP, resulting in more slip on the individual active systems. The proposed method is numerically implemented as an Abaqus user material subroutine within the large deformation framework, such that the simulation of arbitrary load cases is possible.
How to Combine the Parameters of the Yield Criteria and the Hardening Law
Authors: Prates Pedro , Oliveira Marta C. , Sakharova Nataliya A. , Fernandes José Valdemar
Published: June 2013

The numerical simulation of sheet metal forming processes needs the accurate identification of the material parameters, for a given constitutive model. This identification can follow different methodologies and different sets of experimental data can be used, which lead to distinct sets of material parameters. In order to accurately compare the results of several methodologies, it is necessary to guarantee uniformity of their presentation. In this work, the correspondence between sets of parameters of the Hill’48 criterion is explored. The meaning of the “isotropic values” of the parameters associated with the out-of-plane stresses components is discussed and a required condition is proposed, in order to properly compare numerical simulation results obtained by using different input sets of constitutive parameters, identified by different procedures. Finite element simulations of complex shaped forming process, involving strain-path changes, are carried out in order to support the analysis.
Forming of Automotive Aluminum Body Panels by Sheet Hydroforming
Authors: Maki Trent
Published: June 2013

This paper discusses the application of sheet hydroforming technology to the forming of deep draw aluminum automotive body panels. Currently, the amount of aluminum in vehicle architectures is somewhat limited due to cost and also the inability to incorporate common body panel design to aluminum sheet due to lower formability. Typical aluminum sheet has approximately about 30~40% of the formability of comparative steel grades. Automotive designers have been hampered by this fact and have not been able to successfully introduce aluminum sheet for wide range of panels. Sheet hydroforming, however, has a formability advantage over many types of forming methods. This paper will discuss those advantages and show some successful applications to the automotive industry.
Force Prediction for Correction of Robot Tool Path in Single Point Incremental Forming
Authors: Belchior Jérémy , Guines Dominique , Leotoing Lionel , Ragneau Eric
Published: June 2013

In this work, an off-line compensation procedure, based on an elastic modelling of the machine structure coupled with a Finite Element Analysis (FEA) of the process is applied to Robotized Single Point Incremental Forming (RSPIF). Assuming an ideal stiff robot, the FEA evaluates the Tool Center Point (TCP) forces during the forming stage. These forces are then defined as an input data of the elastic robot model to predict and correct the tool path deviations. In order to make efficient the tool path correction, the weight of three numerical and material parameters of the FEA on the predicted forces is investigated. Finally, the efficiency of the proposed method is validated by the comparison between numerical and experimental geometries obtained with or without correction of the tool path.
Material Property Evolution in Incremental Sheet Forming - A Review and Comparison
Authors: Katajarinne Tuomas , Kivivuori Seppo
Published: June 2013

The last decade has shown an expanding interest towards incremental sheet forming (ISF). The present paper focuses on a wide variety of materials used in ISF with emphasis on material behavior and post forming properties. Material behavior knowledge is essential for improving process control and accuracy, post forming properties are essential for introducing ISF for wider industrial use. Included in the study are: a ferritic and four austenitic stainless steel grades, a deep drawing steel, as well as copper and silver. The two latter materials have been widely used for crafted products trough centuries and still have their place in high-end products. The suitability of the different materials for ISF is studied and compared. A comprehensive testing procedure is performed to gain information about behavior during and properties after deformation. The material property evolution is also compared to other forming methods to further enhance understanding of the process. The materials can be divided into stable and metastable materials. Stainless steels are an increasingly important class of alloys that are widely used in industry today. The structure of austenitic stainless steels is metastable which may lead to phase transformation. Strain induced martensite phases can form during plastic deformation of these steels. The formation of martensite affects significantly their mechanical behavior by enhancing the work hardening. Transformation impedes the property prediction as it is linked to the process conditions which may vary during forming. The stable materials lack phase transformation but show both diverse and similar material property evolution as a result of ISF.
Incremental Sheet Metal Forming with Direct Resistance Heating Using Two Moving Tools
Authors: Meier Horst , Magnus Christian
Published: June 2013

This paper describes new developments in an incremental, robot-based sheet metal forming process (‘Roboforming’) for the production of sheet metal components in small batch sizes. The dieless kinematic-based generation of a shape is implemented by means of two industrial robots which are interconnected to a cooperating robot system. Compared to other incremental sheet metal forming machines, this system offers high geometrical form flexibility without the need of any part-dependent tools. The industrial application of incremental sheet metal forming is still limited by certain constraints, e.g. the low geometrical accuracy and number of formable alloys. One approach to overcome the stated constraints is to use the advantages of metal forming at elevated temperatures. For the temperature input into the sheet metal, there are different approaches like heating with warm fluids, a laser beam or using direct resistance heating. This paper presents results of the research project ‘Local heating in robot-based incremental forming’, funded by the German Research Foundation (DFG), where the heating of the current forming zone by means of direct resistance heating is examined as a variation of the Roboforming process. In order to achieve a local limitation of the heating on the current forming zone, the electric current flows into the sheet at the electric contact of the forming tool and the sheet metal. Thus the forming tool is part of the electric circuit. In current literature Authors report about results from experiments using single-point incremental forming, where the forming tool and the clamping frame of the sheet are connected to the power source. In order to further limit the heating on the forming zone, a new approach will be presented in this paper, where a second tool is used to support the forming and heating process, as both tools can be connected to the power source, making a current flow through the rest of the sheet and the clamping frame unnecessary. With the use of two tools the current flow and thus the heated zone of the sheet can be manipulated. Additionally the advantages of the supporting tool, already shown in forming at room temperature, such as increased geometrical accuracy and maximum draw angle can be used. Starting with a description of the new process setup for steel forming at about 600 °C, results of experiments evaluating the influence of the supporting tool on the forming process at elevated temperatures and the resulting geometrical accuracy will be presented in this paper. Therefore, different process parameters as forming temperature, cooling and relative positioning of the both tools have been varied.
Single Point Incremental Forming of a Medical Implant
Authors: Araújo Rogério , Teixeira Pedro , Silva M. Beatriz , Reis Ana , Martins Paulo A.F.
Published: June 2013

Single point incremental forming (SPIF) belongs to the branch of incremental sheet forming processes that enables plastic deformation of blanks without resorting to any specific die or punch. The main characteristics of SPIF determine its appropriateness for producing small batches or single products, being the medical implants one of the key potential fields of application, due to the need of product customization to each patient. Customization is particularly important for obtaining preoperative implants because it allows a significant decrease in the overall surgery time in conjunction with a higher level of flexibility to ensure the required shapes. This results in an improved final product either in aesthetic as well as in functional terms.
A Study on the Nose Radius Influence in Press Brake Bending Operations by Finite Element Analysis
Authors: Bessa Pacheco J. , dos Santos Abel
Published: June 2013

The sheet metal bending is one of the metal forming processes with the simplest geometric interpretation and usually a 2D analysis is considered. The bend over a sheet metal blank consists of a V shape forming by using a punch, with a certain nose radius, forcing the plate against an open die, with a V section. The forming result is a part with an angle obtained between the V legs, flanges, which is known as bending angle. The operation to get the required V angle is called air bending, or free bending. The most common used machines for this forming process are press brakes, special long presses, where the tools, punch and die, are attached to. With the spread use of CNC machines, and their computer control capabilities, most of them using graphical user interface (GUI), became important to get the required shape at first trial. Beyond the required bending angle obtained with just one hit, it is also important to position the gauge system in order to get the successive flange lengths to complete the programmed shape. The main variables controlled by the CNC are the punch penetration inside the die and the position of the back gauge, which is determined by the bend allowance. However this penetration is not the only responsible for the resulting bending angle and the gauging position is not the only responsible for the flange length. Additionally, the radius inside the V shape edge, known as bending radius, influences the geometry and correspondingly the bend allowance. Some authors believe that the punch nose radius has direct influence, both in the bending angle and bend allowance. In this paper, results are presented describing the use of finite element analysis as an aid in the prediction of the inside bending radius, that influences both punch penetration for the final bending angle and the bend allowance for the final flange length. From the air bending analysis, a natural inside bending radius is presented as an important variable in these kind of processes, as well as its minor dependence on the punch nose radius.
On the Geometric Accuracy in Shallow Sloped Parts in Single Point Incremental Forming
Authors: Mohammadi Amirahmad , Vanhove Hans , van Bael Albert , Duflou Joost R.
Published: June 2013

Incremental sheet forming is a versatile manufacturing technology for small series production. This technique is, however, still challenged by limited accuracy. In incremental forming, each shape comes with its unique complexity and typical geometrical deviations. In this work, the applicability of FE modeling for the prediction of geometric inaccuracies in a shallow wall angle cone has been studied. Typical geometric inaccuracies for shallow sloped parts have been investigated both experimentally and by means of simulation. The evolution of underforming of the cone base as well as overforming of the cone wall during SPIF forming of truncated cone have been analysed. Based on the evaluation of the contact zone between the tool and the sheet, it has been concluded that an extended deformation of the sheet outside the tool contact zone is responsible for the overforming of the wall.
Stress Relaxation for Formability Improvement
Authors: Hariharan Krishnaswamy , Majidi Omid , Kim Chong Min , Lee Myoung Gyu , Barlat Frédéric
Published: June 2013

Improved formability has been reported due to stress relaxation when the continuous forming cycle is interrupted with steps by adjusting the punch motion. The contribution of stress relaxation and its parameters on the ductility of materials has not been established so far. In the present work, the stress relaxation behavior of three materials, low carbon steel, DP and TRIP steels are studied. The influence of strain rate and strain on the ductility enhancement due to stress relaxation is analyzed. It is observed that stress relaxation improved the ductility of materials in all the cases and therefore can be used as a potential method to improve formability in sheet metal forming.
Development of a Friction Law Respecting Plastic Surface Smoothing
Authors: Hauer Franz , Willner Kai
Published: June 2013

Friction has an essential influence on metal forming processes and affects the mould filling strongly. Numerical simulation is widely used because they allow for a efficient product design without the time and cost intensive production of prototype moulds. The quality of the simulation results and thus their reliability is determined by the accuracy of the modelling. For this purpose the applied friction law is of great importance. Characteristic of sheet-bulk metal forming is the coexistence of moderate contact pressures like in sheet metal forming and high contact pressures like in bulk metal forming. The Coulomb friction law is suitable for the sheet metal forming process but it predicts too high friction forces for high contact pressures. On the other hand the Tresca friction law is suitable for bulk metal forming but overestimates the friction for low contact pressures. A smooth transition between the Coulomb and Tresca friction law is described by the Shaw friction law and the Wanheim-Bay friction law. An unresolved problem remains the influence of plastic surface smoothing of structured workpiece surfaces. The tribological properties of the surface are altered by the plastic deformation of the surface roughness. As a consequence the real area of contact and thus the friction are larger in unloading and reloading than in the first loading at the same surface pressure. This plays a role in forming processes with multiple stages, where the surface is smoothed by prior forming operations like for example the forming of tailored blanks. Therefore efforts have been made in the numerical modelling of elasto-plastic surface deformation with a halfspace model. This model allows for the efficient modelling of large rough surfaces because it uses only a surface mesh and not an numerically expensive volume mesh like a Finite-Element model. This halfspace model is calibrated and verified with experimental investigations. A friction law taking into account the plastic surface deformation has been developed based on the halfspace simulations. It distinguishes between first loading, where the current surface pressure is higher than all surface pressures which occurred previously, and unloading or reloading, where the friction is higher because the surface is smoothed plastically in a previous load step, where the surface pressure was higher than currently.
Estimation of the Heat Transfer Conditions in a die Radius during Hot Stamping
Authors: Blaise Alexandre , Bourouga Brahim , Abdulhay B. , Dessain Christine
Published: June 2013

Established process in the automotive industry, the hot stamping process consists in heating a blank until complete austenitization in a furnace before transferring it to a press where it is formed at high temperature before being quenched by contact with the cold tools. During the forming step the hot blank slides on the die radius. Locally, the contact pressure can reach very high values. Due to this contact, heat transfer between the hot blank and the die can be significant. Using an omega die instrumented with eight thermocouples localized in the die radius, a 2D inverse method is used to estimate the heat flux that crosses the Blank/Die interface and the temperature field in the die radius and on the die surface. Four thermocouples are located in the blank thickness and a FE analysis is performed to estimate their positions as function of the time. The temperature in the thickness of the blank is considered as uniform according to Biot number value. This assumption is checked afterward. Thus, it is possible to estimate the sliding thermal contact resistance between the blank and the die as a function of time in front of each thermocouple of the blank. The estimation of the temperature field in the die can be useful for investigating the fatigue that occurs in the die. On the other hand, the knowledge of the interface condition in the die radius can present a high interest for improving the numerical simulations of this process.
Induction Heat Treatment for an Automotive Crankshaft: Large Scale Modelling with Moving Inductors
Authors: Klonk Steffen , Bay François
Published: June 2013

A numerical model for a multiphysics problem is presented. It includes the movement of subdomains, which are embedded in a global air domain. The description of the movement is based on a discrete level set representation of the moving boundaries. It is based on the original geometry of the moving tools, such that the mesh quality is not reduced in subsequent time steps.
Digital Image Correlation for On-Line Wall Thickness Measurements in Thick Gauge Thermoforming
Authors: van Mieghem Bart , Lava Pascal , Debruyne Dimitri , van Bael Albert , Ivens Jan
Published: June 2013

The homogeneity of the wall thickness (distribution) is considered to be the most critical parameter in the quality assessment of a thermoformed product. Numerous previous studies have characterized the thickness distribution by means of manual discrete tactile measurements. Such approach is slow, operator dependent and only gives results on specific points of the final product, resulting in complicated judgements on the causes of the thinning of the polymer sheet. This work presents a methodology to use digital image correlation (DIC) for on-line, full field wall thickness measurements of thick gauge thermoformed parts during and after thermoforming. Such technique offers the following advantages. Firstly, it provides the user with thickness results over a complete area instead of a discrete measuring point. Secondly, it allows on-line measurements so that a better insight can be obtained in the deformation mechanisms during the forming process. Finally, a correlation is made between each undeformed point in the base image and the same point in the deformed images during thermoforming, resulting in a full-field strain image where intermediate sheet thinning can be calculated. This makes it easier to determine a causal relation between thermoforming parameters and final thickness distribution of the product.