Prediction of burr height formation in blanking processes using neural network

Productivity and quality in sheet metal blanking processes part can be assessed by the burr height of the sheared edge after blanking. This paper combines predictive finite element approach with neural network modelling of the leading blanking parameters in order to predict the burr height of the parts for a variety of blanking conditions.Experiments on circular blanking operation has been performed to verify the validity of the proposed approach.The numerical results obtained by finite element computation including damage and fracture modelling and tool wear effects were utilized to train the developed simulation environment based on back propagation neural network modelling.A trained neural network system was used in predicting burr height of the blanked parts versus tool wear state and punch-die clearance.The comparative study between the results obtained by neural network computation and the experimental ones gives good results.     

Finite element prediction of blanking tool cost caused by wear

The total cost of a blanked part is determined by a large number of factors, including the material cost, manufacturing costs. Predicting the manufacturing costs of a blanked part requires accurate estimation of tool cost caused by wear. The aim of this paper is to develop a finite element model allowing for the numerical prediction of the blanking tool life which allows for the evaluation of the cost rate of blanking tool caused by wear needed to assess the total cost of a blanked part. A wear prediction model has been implemented in the finite element code Abaqus in which the tool wear is a function of the normal pressure and some material parameters. In the present work, the tool is modeled as rigid body hypothesis, and the wear variables are computed in the contacting elements. The altered tool contact surface and contact pressure tool shapes are updated iteratively to simulate wear over a long period of time of about 100,000 cycles. A damage model is used in order to describe crack initiation and propagation into the sheet. The distribution of the tool wear on the tool profile is obtained and compared to industrial observations.     

冷轧硅钢产品品质对冲片性影响的研究分析

通过对冷轧硅钢片冲片加工过程及冲切模具磨损的研究分析，结合本厂实际情况，提出了如何通过改进产品品质以进一步减小模具损耗、改进冷轧硅钢冲片性的建议。     

Wear Transition as a Means of Fracture Toughness Evaluation of Hardmetals

The main objective of this investigation was to define operating parameters for a novel method for the simultaneous evaluation of abrasion wear resistance and fracture toughness of hardmetals. The optimal design of a tribotester and a testing procedure from the operational cost and time criteria point of view was another target of the investigation. The method of testing is based on the finding that the wear transition stage, typical for the early and unsteady stage of the wearing process, is controlled by brittle fracture of hardmetal specimens while the following steady-state is controlled by abrasion processes. The brittle fracture of edges will control the wearing-in process only if the edges are initially sharp, the material is fairly brittle (e.g., hardmetal, cermetal), and material is tested on the edge as in the presented tribotester. Precise identification of the tribological transition for every hardmetal grade was possible thanks to the particular specimen shape (with three distinct edges) and to periodic monitoring of specimen mass loss. The fracture-mechanics-based model developed during the course of this investigation was used in the calculation of fracture-toughness values for the hardmetal grades tested. The rating of hardmetals according to their fracture toughness as well as their resistance to abrasive wear in rubbing contact with particulate alumina are presented. The effect of additional hot isostatic pressing (HIPing) on mechanical properties of the hardmetals tested is also illustrated.     

An experimental analysis of effects of various material tool’s wear on burr during generator sheets blanking

Blanking is one of the most frequently used processes in sheet metal forming. Unlike other forming processes, such as stamping, blanking not only deforms the metal plastically to give the appropriate size and shape, but also ruptures the sheet metal in the desired zones. Among the others, blanking enables manufacturing of electric motor components, such as rotor or stator parts. The parts of the low power commutator motor of rotor and stator are made of generator sheets, which are really difficult to do from the machining point of view. The shock loads and high reaction of the sheet metal of separation surface to the punch surface are presented during the blanking process. In this paper, an investigation has been made to study the effects of punch–die clearance, tool materials, and tool coatings on the wear of blanking tools. In the paper, the feasibility analysis for various materials used for production of the tools for punching the generator sheets is presented.     

Abrasive wear of WC-FeAl composites

The abrasive wear behavior of tungsten-carbide iron-aluminide composite materials was investigated using a pin-on-drum wear-testing machine. Samples were prepared by uniaxially hot pressing blended powders. The wear rates of specimens containing 40 vol.% matrix of atomic composition, Fe₆₀Al₄₀, were measured and results compared with those of conventional WC-10 vol.% Co hardmetal. They were found to be comparable to those of WC-10% Co hardmetal, when abraded by 120 μm SiC papers under identical conditions. The wear resistance of WC-Fe₆₀Al₄₀ composites increased with reduction in WC-grain size and associated with increase in composite hardness. Scanning electron microscopy revealed that the wear surfaces of WC-40% Fe₆₀Al₄₀ composites and WC-Co hardmetal were similar in appearance. The higher hardness and work hardening ability of Fe₆₀Al₄₀ binder, as compared to Co metal, are believed to be responsible for the excellent abrasive wear resistance of WC composites containing iron aluminide binder.     

精密下料中圆形锤头棒料摩擦副的摩擦学性能分析

针对精密下料中存在的圆形锤头棒料摩擦副磨损严重问题，借助WTM-2E型可控气氛摩擦磨损试验仪，研究了不同转速和不同质量分数纳米MoS2添加剂下的GCr15钢块45钢柱摩擦副的摩擦磨损性能。结果表明：随着上摩擦副(45钢柱)的转速增加，磨损行程变长，摩擦因数和磨损量呈减小趋势，磨损表面形态由黏着磨损转变为磨粒磨损。采用声发射技术对摩擦副表面磨损状态进行实时监测，定量确定出质量分数为0.5%的纳米MoS2添加剂的减摩抗磨效果最佳。     

Prediction of optimum clearance in sheet metal blanking processes

The blanking process and structure of the blanked surface are influenced by both the tooling (clearance and tool geometry) and properties of the workpiece material (blank thickness, mechanical properties, microstructure, etc.). Therefore, for a given material, the clearance and tool geometry are the most important parameters. The objective of the present work is to develop a methodology to obtain the optimum punch-die clearance for a given sheet material by simulation of the blanking process. A damage model of the Lemaitre type is used in order to describe crack initiation and propagation into the sheet. A comparative study between numerical and experimental results shows good agreement.     

Numerical and experimental analyses of punch wear in the blanking of copper alloy thin sheet

This research on punch wear resulting from the blanking of copper alloy thin sheet has been conducted by means of experimental and numerical analyses. Firstly, the experimental method has consisted in measuring punch worn profiles from replicas, and secondly in obtaining the wear coefficient by using a specific tribometer. The numerical modelling of blanking process has been developed with the finite element method to compute the mechanical fields necessary to calculate wear. Thus, the Archard formulation for abrasive wear has been programmed to compute the wear depth and the resulting punch geometry. Finally the simulation results of wear prediction have been compared to experimental ones.     

Design of Experiment Based Analysis for Sheet Metal Blanking Processes Optimisation

The blanking of metal parts for electronic components is subjected to a variety of process parameters. In this paper, an experimental investigation into the blanking process was carried out using tools with four different wear states and four different clearances. The aim was to study the effects of the interaction between the clearance, the wear state of the tool and the sheet metal thickness on the evolution of the blanking force and the geometry of the sheared profile. Designed experiments are an efficient and cost-effective way to model and analyse the relationships that describe process variations. The results of the proposed experimental investigation show the strong dependence between the geometrical quality of the blanked part and the magnitude of the force applied on the tool as well as the variations in the process factors .     

The relationship of tangential stress to wear particle formation mechanisms

Experimental results and observations by scanning electron microscopy have demonstrated that the process of wear particle formation under lubricated sliding conditions is greatly affected by the tangential stress. In these experiments, the normal load was kept constant and the tangential stress was varied by changing the friction coefficient using different friction-reducing additives in the base oil. The predominant wear mechanism is related to the magnitude of friction coefficient attained by the friction modifier. The wear rate and the level of surface damage are greatly reduced if the friction coefficient is lower than a specific threshold value. Under these conditions wear particles are formed from deformation of surface asperities. At higher friction coefficients more wear was observed to occur by the process of plowing and delamination (i.e. subsurface microvoid and crack formation). Under severe wear conditions and lubrication failure, extremely large amounts of wear and severe surface damage result from the adhesive wear mechanism (i.e. material transfer across the contact surface).     

Effect of technological parameters on microstructure and accuracy of B1500HS steel parts in the hot blanking

Hot blanking process could be used for producing diverse fine blanking parts with comprehensive mechanical properties and to solve the problems in the piercing and trimming of press-hardened parts. To explore the optimal hot blanking process and evaluate the effects of some technological parameters on the phase transformation, fracture quality, and dimensional accuracy of the parts, several different blanking temperatures (450–800 °C) and die clearances (8–25%) were used in the hot blanking of B1500HS steel. The experimental results show that as the blanking temperature increases at a certain die clearance, the dimensional accuracy shows a trend of “negative growth–positive growth–negative growth,” and a higher dimensional accuracy of blanked parts can be attained at blanking temperatures 450–500, 600–650, or 750–800 °C. Besides, the burnish zone width increases, and the burnish and rollover zone widths account for ~?80% of the steel sheet thickness at 800 °C. At blanking temperatures 650–800 °C, the microstructure of blanked parts is completely martensite, the microhardness of parts is ~?550 HV, and the perpendicularity of fracture increases as the blanking temperature increases. Parts with a high-dimensional accuracy, better fracture perpendicularity, wide burnish zone, better mechanical properties, and wear resistance can be obtained at blanking temperatures 750–800 °C.     

Abrasive erosive wear of powder steels and cermets

Composite materials produced by powder metallurgy provide solutions to many engineering applications that require materials with high abrasive wear resistance. The actual wear behaviour of a material is associated with many external factors (abrasive particle size, velocity and angularity) and intrinsic material properties of wear (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of wear resistant materials are highly dependent on the content of the reinforcing phase, its size and on the mechanical properties of the constituent phase. This study is focused on the analysis of the (AEW) abrasive erosive wear (solid particle erosion) using different wear devices and abrasives. Powder materials (steels, cermets and hardmetals) were studied. Wear resistance of materials and wear mechanisms were studied and compared with those of commercial steels. Based on the results of wear studies, surface degradation mechanisms are proposed. The following parameters characterizing the materials were found necessary in materials creation and selection: hardness (preferably in scale comparable with impact), type of structure (preferably hardmetal type) and wear parameters characterizing material removal at plastic deformation.     

Comparative Study of Thermally Sprayed Coatings Under Different Types of Wear Conditions for Hard Chromium Replacement

The tribological properties of part surfaces, namely their wear resistance and friction properties, are decisive in many cases for their proper function. To improve surface properties, it is possible to create hard, wear-resistant coatings by thermal spray technologies. With these versatile coating preparation technologies, part lifetime, reliability, and safety can be improved. In this study, the tribological properties of the HVOF-sprayed coatings WC–17%Co, WC–10%Co4%Cr, WC–15% NiMoCrFeCo, Cr₃C₂–25%NiCr, (Ti,Mo)(C,N)–37%NiCo, NiCrSiB, and AISI 316L and the plasma-sprayed Cr₂O₃ coating were compared with the properties of electrolytic hard chrome and surface-hardened steel. Four different wear behavior tests were performed; the abrasive wear performance of the coatings was assessed using a dry sand/rubber wheel test according to ASTM G-65 and a wet slurry abrasion test according to ASTM G-75, the sliding wear behavior was evaluated by pin-on-disk testing according to ASTM G-99, and the erosion wear resistance was measured for three impact angles. In all tests, the HVOF-sprayed hardmetal coatings exhibited superior properties and can be recommended as a replacement for traditional surface treatments. Due to its tendency to exhibit brittle cracking, the plasma-sprayed ceramic coating Cr₂O₃ can only be recommended for purely abrasive wear conditions. The tested HVOF-sprayed metallic coatings, NiCrSiB and AISI 316L, did not have sufficient wear resistance compared with that of traditional surface treatment and should not be used under more demanding conditions. Based on the obtained data, the application possibilities and limitations of the reported coatings were determined.     

Effect of Cold Rolling on the Fretting Wear Behavior and Mechanism in Inconel 690 Alloy

The influence of cold rolling on the fretting wear behavior and mechanism of Inconel 690 alloy at 320?°C in air was studied. The wear volume and worn surface were obtained and analyzed using laser scanning confocal microscopy, electron back-scattering diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The grinding surface and strain distribution were also studied by electron back-scattering diffraction to analyze the mechanism of fretting damage. The results indicated that with an increase in cold rolling reduction, the microhardness was increased. However, the friction coefficient and wear volume first increased and then decreased. The characteristics of fretting areas changed from a gross slip regime to a partial slip regime. Accordingly, the damage mechanism in the gross slip regime was a combination of oxidative wear, abrasive wear, and delamination, whereas the damage mechanism in the partial slip regime was mainly adhesive wear.     

TC4合金微动疲劳损伤研究

研究了TC4合金在柱面-平面接触务件下的微动疲劳行为，分析了其微动疲劳损伤机制。结果表明：在试验务件下，微动区边缘的损伤特征以粘着磨损为主，而微动区中部则以磨粒磨损和接触疲劳为主。疲劳裂纹易于在微动区．特别是在蚀坑处萌生和扩展。促使微动疲劳裂纹萌生的因素：一是法向应力和切向摩擦力引起的材料表层塑性变形，二是微动磨损破坏了材料的表面完整性，造成了缺口应力集中效应。     

Investigation of the viscous and thermal effects on ductile fracture in sheet metal blanking process

In this paper, a methodology is proposed to predict the ductile damage in the sheet metal blanking process using a coupled thermomechanical finite-element method. A constitutive material model combined with the ductile fracture criteria was used. The effect of material softening due to the heat generated during plastic work in a specimen was considered in blanking simulations. To verify the validity of the proposed model, several blanking simulations are performed and the results compared with those obtained from an experimental study. The interaction of fracture initiation and temperature distribution in the sheet metal during the process was studied. The effect of velocity and the clearance on the product shape were examined. It was seen that at high punch speeds the viscous and thermal effects have significant effects on product quality.     

硬质合金圆盘刀分切硅钢片的磨损形态及机理研究

分析了圆盘剪分切加工过程中圆盘刀的受力,利用硬质合金圆盘刀进行了硅钢片的分切加工试验,研究了硬质合金圆盘刀的磨损,对比分析了圆盘刀刃口磨损前后的表面形貌、微观结构和钴元素含量的变化,探讨了其磨损形式及机理。结果表明,硬质合金圆盘刀磨损主要在刃口两侧形成磨损带,随着磨损的发生,圆盘刀切削刃过渡圆弧半径增大、刃口变钝,刀具的磨损形式主要表现为WC硬质颗粒裸露脱落及材料的黏结撕裂,磨损机理主要为硬质合金黏结相钴元素的流失、疲劳磨损和黏结磨损。     

Tribological behavior of aluminum alloys surface layer implanted with nitrogen ions by plasma immersion ion implantation

Some 2014 and 2024 aluminum alloys were implanted with nitrogen ions (N⁺) by Plasma Immersion Ion Implantation (PIII), and dose range was from 2×10¹⁷ to 1×10¹⁸ N⁺ cm⁻². The microstructure of surface layer was studied by Transmission Electron Microscopy (TEM). The depth profile of the implanted layer was investigated by Auger Electron Spectrometry (AES). The wear test was carried on a pin-on-disk wear tester. The micro-morphology of wear was observed by Scanning Electron Microscopy (SEM). The results reveal that: after implanted with nitrogen ions, the friction coefficient of surface layer decreased, and the relative wear resistance increased with the increase of the nitrogen dose. The tribological mechanism was mainly adhesive, and the adhesive wear tended to become weaker gradually with the increase of nitrogen dose. The upper two effects were mainly attributed to the formation of hard AlN precipitation and supersaturated solid solution of nitrogen in the surface layer.