Ductile Iron Research Articles

Stress Evaluation Using Finite Elements in a Manual Agricultural Tool

This study addresses the imperative need for efficient hand-held agricultural tools, particularly in challenging contexts like hillside agriculture, by focusing on the redesign and evaluation of a manual tillage tool. The objective is to comprehensively assess the stress and fatigue life of a redesigned tool, considering different manufacturing materials such as steels (AISI/SAE 4140, 4130, 1060), A356 aluminum, and nodular cast irons. Employing finite element method simulations and the Von Mises equation, this research confirms an optimal performance within elastic limits for all materials, mitigating the risks of plastic deformation or breakage during normal operation, with Von Mises stresses ranging from 8.39 to 16.30 MPa. All the tools yielded optimal results, meeting the critical requirements for soil penetration resistance, reporting no fatigue failures, and exhibiting useful life values over 1.75 x 1013 years. In terms of ergonomics, A356 aluminum stands out, as it is less heavy and implies a lower effort by the operator, promoting efficient tillage without compromising comfort. This research provides nuanced insights for the design of agricultural tools, emphasizing the harmonious balance between efficiency, longevity, and operator comfort in sustainable practices.

Investigation of the Quality of Flywheel SG Iron Sand Casting Using the Optimized Riser Dimensions: Numerical Simulation and Experimental Validation

Investigation of the Quality of Flywheel SG Iron Sand Casting Using the Optimized Riser Dimensions: Numerical Simulation and Experimental Validation

Modelling of phase transformations occurring in the process of austempered ductile iron manufacturing

The paper presents mathematical models and their implementation in C # language describing the phase transformations occurring in the process of austempered ductile iron (ADI) manufacture. The research includes two main stages: austenitization and isothermal holding at the bainitic range. The influence of free energy of austenite and ferrite on transformations was taken into account. Parameters of models were identified based on inverse analysis and experimental research. As part of the research, verification and validation of the developed models was carried out based on the results of experimental research. The tool developed and implemented enables the analysis of phase transformations occurring during heat treatment with isothermal holding of ductile iron with Ni addition.

Extension of Flow Behaviour and Damage Models for Cast Iron Alloys with Strain Rate Effect

Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry. To study the mechanical behavior of a typical ductile cast iron (GJS-450) with nodular graphite, uni-axial quasi-static and dynamic tensile tests at strain rates of 10−4, 1, 10, 100, and 250 s−1 were carried out. In order to investigate the influence of stress state on the deformation and fracture parameters, specimens with various geometries were used in the experiments. Stress strain curves and fracture strains of the GJS-450 alloy in the strain rate range of 10−4 to 250 s−1 were obtained. A strain rate-dependent plastic flow model was proposed to describe the mechanical behavior in the corresponding strain-rate range. The available damage model was extended to take the strain rate into account and calibrated based on the analysis of local fracture strains. Simulations with the proposed plastic flow model and the damage model were conducted to observe the deformation and fracture process. The results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 alloys. The predictions with the proposed plastic flow and damage models at various strain rates agree well with the experimental results, which illustrates that the rate-dependent plastic flow and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain rates. The proposed plastic flow and damage models can be used to describe the deformation and fracture analysis of materials with similar properties.

Effects of Static Strain Aging on Mechanical Performance of Ductile Cast Iron

EN-GJS-400-15U nodular cast iron intended to be used as load-bearing element in long-term geological disposal canisters containing spent nuclear fuel in Finland and Sweden was studied for static strain aging (SSA). Tensile test specimens manufactured from the nodular cast iron were pre-strained to 1%, 2% and 3% nominal plastic strains. The pre-strained specimens were aged at different temperatures ranging from room temperature to 400 °C for varying times. The aged specimens were tested with conventional tensile testing using constant cross-head speed of 0.016 mm/s. Additionally, four specimens were studied with digital image correlation (DIC) during the tensile testing to obtain full-field strain measurements. SSA resulted in elevated pronounced yield point in all the conditions, while the as-received material showed continuous yielding behavior. SSA reduced the elongation to fracture. DIC tests showed more localized yielding behavior in the SSA specimens. Over-aging effect was observed at 400 °C where increasing pre-strain did not increase the yield stress more. For 1-day aging time, the highest yield stress increment was found after aging at 200°C. The yield stress of the material was almost identical after aging in 100°C and 200°C.

The effect of silicon on the critical resolved shear stress of solid solution strengthened ferritic ductile iron

Solid solution strengthened ferritic ductile iron (SSFDI) exhibits improved mechanical properties compared to conventional ductile cast iron (DCI) grades, however, its potential widespread application is hindered by unpredictable brittle fracture which might be attributed to microstructural silicon segregation and associated superstructure formation. The aim of the present study is therefore to deepen the understanding on the effect of local silicon segregation on the mechanical properties of SSFDI, which is crucial especially for the common applications of DCI in cyclically loaded structures. Micropillar compression tests were carried out on three different casts to investigate the solution strengthening effect of silicon in the ferritic matrix. An almost perfect linear relationship between critical resolved shear stress (CRSS) and global silicon content was found. It was also found that the variation of CRSS with silicon content corresponds well to the variation of the macroscopic yield limits (under tension and compression) with global silicon content of different SSFDI alloys. This indicates that the ferritic matrix dominates the yield limit of the DCI alloys investigated in this study, while the morphology of the graphite nodules plays a minor role under monotonic loading conditions.

A study on optimal parameter combinations for austempered ductile iron

Nodular cast iron possesses a spherical graphite shape and exhibits mechanical properties closely resembling those of steel after heat treatment. The austempering method provides a means of enhancing the mechanical properties of nodular cast iron. This study aimed to investigate the optimal parameter combinations for Austempered Ductile Iron (ADI). The experiments involved varying the austenitization temperature and austempering time. Multiple tests were conducted to analyze the effects of austenitization temperature and tempering time on the microstructure, hardness, and impact toughness. The experimental samples were obtained from Y-block nodular cast iron austenitized at 850, 900, and 950°C for 90 min in an electric furnace. Subsequently, they were quenched in a salt bath at a temperature of 350°C and held for 60, 90, and 120 minutes before being cooled to room temperature. Mechanical tests and microstructure observations were performed on both the as-cast sample and after austempering. The microstructure was observed using an optical microscope before and after the etching. The research findings indicated that austempering increases the hardness and impact toughness of nodular cast iron. The highest hardness (46.8 HRC) was achieved from a parameter combination of an austenitization temperature of 850°C and an austempering time of 90 minutes. This particular sample also exhibited a relatively higher impact energy (3.8 J) compared to the others. The results of this study suggest that the austenitization temperature and tempering time exert an influence on the mechanical properties.

On how S-N curves for nonproportional loading can be determined from S-N curves for proportional loading – An exemplary evaluation of numerous fatigue tests using scaled normal stresses

The fatigue design of safety–critical components necessitates a delicate balance between sustainability and safety. This study explores the challenge of achieving a balanced design for components subjected to multiaxial loads, focusing on nonproportional loading effects such as an increasing or decreasing fatigue life compared to proportional loading. Existing studies present divergent views on the correlation between nonproportional hardening and fatigue life shift, with some proposing a connection while others treat them independently. It is still unclear which of the research groups may be right. In this article, the effects are considered separately as independent effects, with the focus on the shift in fatigue life.This paper compares various methods of representing fatigue test results under proportional and nonproportional loading. An attempt is made to establish comparability of the tests from different references. One challenge here is, on the one hand, to establish comparability with different stresses on individual material groups and, on the other hand, to consider the second material effect, namely nonproportional hardening.For this purpose, a strength hypothesis is used on the one hand and a plastic correction in combination with a damage parameter is applied on the other. The procedure described in this paper can also be used with other suitable strength hypotheses and damage parameters. In the following, the scaled normal stress hypothesis in combination with the damage parameter according to Smith, Watson and Topper is used as an example.The aim of this paper is to quantitatively describe the shift in fatigue life to be able to include this material effect in a fatigue assessment depending on the material group. A comprehensive database comprising steel, wrought aluminum, cast aluminum, and spheroidal graphite cast iron is utilized to evaluate the shift in fatigue life under nonproportional loading. The database covers various control types, specimen geometries, and amplitude ratios, extending from low cycle to very high cycle fatigue regime.Based on the evaluation, material group-dependent properties can be derived, which can finally be used in a fatigue assessment as an averaged correction of the calculated fatigue life or to predict S-N curves for nonproportional loading based on these for proportional loading.

Shrinkage Investigation of Ductile Iron Castings

Shrinkage Investigation of Ductile Iron Castings

A comparative study of laser fluence effect on surface modification and hardness profile of austempered ductile iron

The impact of laser transformation hardening (LSH) and Laser surface melting (LSM) on an austempered ductile iron (ADI) alloy was investigated. Various laser fluences (J mm−2) were irradiated on the ADI specimens, obtained by different beam powers and scanning speeds to reach the optimum parameters to attain a surface with a good combination of high hardness and deep hardened depth, together with obtaining minimal distortion and crack-free surface. ADI surfaces were treated by means of high-power Nd:YAG laser in continuous wave mode. A detailed investigation of the obtained microstructure was characterized via optical and scanning electron microscopy attached to an EDX analyzer as well as X-ray diffraction analysis. Such a wide laser fluence range has a considerable effect on the achieved microstructure. A process parameter map was established which indicated that three different laser treatments were induced under such values of laser fluences: a laser transformation hardening, a partial laser melting, and a complete laser melting. The results revealed that to produce a hardened microstructure, specimens have to be operated within a very small range of laser fluence from 9.6 up to 29 J mm−2, achieving surface hardness values around 900 HV0.1 and depths of approximately 184–700 μm, respectively. Meanwhile, partial melting of the treated layer took place at a medium energy density range from 37 to 112 J mm−2, by a further increase in laser fluence (120–360 J mm−2), complete melting occurred which resulted in a deeper treated layer that reached 3.5 mm with an increase in microhardness value to almost 1100 HV0.1 at 360 J mm−2. The obtained microstructure in case of low laser fluence consisted of an austenite dendritic structure with undissolved graphite nodules, however, at medium and high laser fluence, the microstructure contains large cementite plates, iron-silicon carbides, a small area of ledeburite structure, and some retained austenite. The quantitative amounts of such phases directly depend on the applied laser fluence. Such phases were identified by means of EDX analysis.

Підвищення тріщиностійкості чавунів з кулястим графітом та їх термічна обробка при виготовленні зносостійких виробів

Methods of achieving the maximum values of crack resistance of Spheroidal graphite cast irons (SGCI) due to the combination of strength of bainite with high plasticity of residual austenite (in the amount of 30-35%) are considered. The results of such studies are suitable for use, in particular, in the manufacture of teeth or crowns of buckets of excavators and other working bodies of mining, earthmoving or earth-moving machinery, as well as parts that function in extreme conditions. These data are comparable to the known results of work on increasing the wear resistance of SGCI for variable parts of agricultural machinery and transport. In addition to crack and wear resistance, the long-term performance and efficiency of the working organs depends on maintaining their pointed part or blade in a sharp condition. The creation of functional-gradient materials, which are characterized by the effect of self-sharpening during their operation and wear, is considered. This effect is proposed to be implemented through the use of gradient heat dissipation in the material of the sand mold, increasing these values by introducing a refrigerant near a specific surface of the casting to accelerate its cooling. For this, casting molds made of loose sand were used in the Lost Foam casting (LFC) process. The method of manufacturing metal working bodies is described on the example of casting by the LFC method of an excavator bucket tooth, it is proposed to obtain its gradient structure according to the regime of heat treatment of castings in a foundry mold due to intensive cooling of its given surface to increase its hardness. At the same time, such conditions were used for the construction and formation of the pattern cluster in the sand, which cause the cooling of the opposite surface to slow down with its lower hardness, which corresponds to the conditions of self-sharpening of the tooth under its operating conditions. Keywords: Spheroidal graphite cast iron, austempering, heat treatment, castings, austenite, Lost Foam casting, bainite.

Investigation of The Effect of Molding Material Difference on Design in GGG70 Ductile Cast Iron Production

The casting process involves filling a prepared mould cavity with molten metal, which takes the shape of the container. While the liquid metal takes the shape of the container it is in, the method is attractive, while the volumetric changes during the liquid-solid transformation reveal the importance of moulding design for the manufacture of solid parts. Especially in cast irons, moulds with the same design may produce different results depending on the changing casting and foundry conditions because the volumetric change that occurs during the solidification of ductile cast irons is affected by many parameters and develops differently than in steel and aluminium castings. This study used model wet and resin molding materials to create single and double-riser moulding and castings with different section thicknesses. The importance of the type of mold material used in castings and the number of feeders for the robust production of the cast part was evaluated using experimental and modeling techniques. When the results were examined, it was seen that the shrinkage risk was lower with resin mould than with green sand moulding. In addition, depending on the riser connection point, the importance of the riser neck has emerged.

Fatigue Analysis of Prosthetic Osseointegration with a Novel Protection System

Recent advancements in osseointegration technology offer a promising alternative to traditional prosthetic limbs, leading to improved comfort and functionality for amputees. However, the primary concern lies in the risk of catastrophic failure and falling due to fractures within the osseointegration system. To address this challenge, a protective system has been designed. The new design includes an internally rod part with a notch at the bottom to ensure failure at that point, made of ductile cast iron. A cover made of Ti6Al4V alloy is placed to ensure fracture isolation within the protection nail during sudden loading, preventing unexpected falls. After conducting tensile tests for the mentioned alloys and materials, and then relying on the ground reaction force in the numerical analysis using SolidWorks software, Finite Element Analysis (FEA) simulations confirmed the effectiveness of this design, with the expected fracture point occurring in the protection nail after exceeding 54973 walking cycles, surpassing the expected maintenance lifespan of the prosthetic limb. This design represents a significant step forward in enhancing the safety and reliability of integrated prosthetic limbs, ultimately leading to improved mobility and peace of mind for amputees.Recent advancements in osseointegration technology offer a promising alternative to traditional prosthetic limbs, leading to improved comfort and functionality for amputees. However, the primary concern lies in the risk of catastrophic failure and falling due to fractures within the osseointegration system. To address this challenge, a protective system has been designed. The new design includes an internally rod part with a notch at the bottom to ensure failure at that point, made of ductile cast iron. A cover made of Ti6Al4V alloy is placed to ensure fracture isolation within the protection nail during sudden loading, preventing unexpected falls. After conducting tensile tests for the mentioned alloys and materials, and then relying on the ground reaction force in the numerical analysis using SolidWorks software, Finite Element Analysis (FEA) simulations confirmed the effectiveness of this design, with the expected fracture point occurring in the protection nail after exceeding 54973 walking cycles, surpassing the expected maintenance lifespan of the prosthetic limb. This design represents a significant step forward in enhancing the safety and reliability of integrated prosthetic limbs, ultimately leading to improved mobility and peace of mind for amputees.

Effect of Cu Addition Above the Solubility Limit on Microstructure Formation and Cu Segregation in 800 MPa Grade Ductile Cast Iron During Solidification

In this study, the effect of 3 mass%Cu additions on microstructure formation and Cu segregation in 800 MPa grade ductile cast iron during solidification was investigated. The calculated phase diagram showed that after the addition of 3 mass%Cu, the Cu phase with a negligible amount appeared below 1000°C, and most Cu was included in the matrix. Based on optical microstructure, after the addition of 3 mass%Cu, the size of graphite nodules became finer, and the microstructure rarely had an area with α-ferrite. Image analysis showed that the fraction of pearlite increased significantly, indicating that Cu greatly promoted the formation of pearlite. Compositional analysis by scanning electron microscopy indicated that the pearlitic area also contained approximately 3 mass%Cu, which corresponds to those of primary and secondary austenite calculated. A small and bright phase particle containing a large amount of Cu was observed at the interface of graphite and matrix.

Multi Response Modelling and Optimisation of Copper Content and Heat Treatment Parameters of ADI Alloys by Combined Regression Grey-Fuzzy Approach

This paper deals with the austempering of ductile iron (ADI) and clarifies the influential austempering parameters during the production of ADI. During the austempering process, the heat treatment parameters can be varied, thus influencing the final microstructure and, of course, the mechanical properties of ADI. To appropriately conduct experiments and obtain good results, an experimental plan was developed using the Design Expert 13 software. Along with the heat treatment parameters, the influence of the copper content on the ADI toughness, tensile strength, and elongation was determined. The obtained results from this experiment were used to develop unique mathematical models which describe the influences of heat treatment and copper content on the observed mechanical properties of ADI samples. These mathematical models can be applied to predict the analysed mechanical properties of ADI in the dependence of heat treatment parameters and copper content in base ductile iron. For the multi response optimisation of toughness, tensile strength, and elongation, a hybrid grey-fuzzy technique was presented as a significant contribution to the enhancement of the analysed mechanical properties. Consequently, the copper content and heat treatment parameter levels that resulted in the maximal mechanical properties’ functions were defined.

Effects of Manganese and Heat Treatment on Mechanical Properties in Spheroidal Graphite Cast Iron

Effects of Manganese and Heat Treatment on Mechanical Properties in Spheroidal Graphite Cast Iron

Cement-mortar lining failure and metal release caused by electrochemical corrosion of ductile iron pipes in drinking water distribution systems

The electrochemical corrosion of ductile pipes (DPs) in drinking water distribution systems (DWDS) has a crucial impact on cement-mortar lining (CML) failure and metal release, potentially leading to drinking water quality deterioration and posing a risk to public health. An in-situ scanning vibrating electrode technique (SVET) with micron-scale resolution, microscopic scale detection and water quality analysis were used to investigate the corrosion behavior and metal release from DPs throughout the whole CML failure process. Metal pollutants release occurred at three different stages of CML failure process, and there are potential risks of water quality deterioration exceeding the maximum allowable levels set by national standards in the partial failure stage and lining peeling stage. Furthermore, the effects of water chemistry (Cl−, SO42−, NO3−, and Ca2+) on corrosion scale growth and iron release activity, were investigated during the CML partial failure stage. Results showed that the CML failure process in DPs was accelerated by the autocatalysis of localized corrosion. Cl− was found to damage the uncorroded metal surface, while SO42− mainly dissolved the corrosion scale surface, increasing iron release. Both the oxidation of NO3− and selective sedimentation of Ca2+ were found to enhance the stability of corrosion scales and inhibit iron release.

Microstructures, Compressive Residual Stress, Friction Behavior, and Wear Mechanism of Intensive Quenched Ductile Iron

Microstructures, Compressive Residual Stress, Friction Behavior, and Wear Mechanism of Intensive Quenched Ductile Iron

The pressure treatment effect on the high‑strength austempered ductile iron structure

This paper presents the results of a study on the effect of pressure treatment (direct hot extrusion) on the structure of graphite inclusions and the metallic matrix of high‑strength austempered ductile iron. Comparative analysis of the cooling processes of the cast high‑strength ductile iron billet without deformation and after deformation was carried out using simulation modeling methods. The results of the study on the effect of hot deformation (up to 950–970 ℃) on the fracture structure and mechanical properties of austempered high‑strength ductile iron billets are presented.

Sprecific of distribution of chemical elements in graphite inclusions in as‑cast and deformed ductile cast iron

Sprecific of distribution of chemical elements in graphite inclusions in as‑cast and deformed ductile cast iron