Hardening Process Research Articles

A Rapid and Cost Effective Hardening Method for Tissue Culture Derived Banana Plantlets

The present study was aimed to develop a cost effective method for the hardening of tissue culture derived plants of banana var. Robusta. Two approaches were investigated to reduce cost. First, the shoots inoculated in rooting medium were incubated in (i) growth room under controlled temperature and light conditions for four weeks (RL) (ii) shadehouse exposed to natural light and ambient temperature (RP). The plants obtained from these treatments were given five hardening treatments (a) direct planting in polybags (filled with 1 : 1 Soil and leaf mould) (DP), (b) DP plants covered individually with transparent polybags (DPC), (c) DPC plants placed in tray of water (up to 3 cm height)-DPCW (d) DP plants kept in polytunnel (DPP) (e) DP plants placed in tray of water and kept in polytunnel DPWP, (f) control plants (CN)-primary hardened in potrays kept in polytunnel for four weeks followed by transplantation to polybags (filled with3:1 Soil and leaf mould). RP Plants were greener and sturdier with less hyperhydricity. Rooting outside the lab (RP) reduced the cost as the growth room space during rooting could be saved and so there is saving in electricity of lighting and climate control. 80% of plants in control and 50% plants in direct planting (DP) survived. In all other treatments 100% survival was observed. RP-DPCW and RP-DPWP plants showed the best performance in terms of visible appearance and accumulation of biomass. The method employed could reduce the hardening period from 12 weeks (CN) to 8 weeks. The cost reduction occurs in this process by a) omitting primary hardening process which requires costly potting media, manpower and climate controlled greenhouse, b) Lab space could be saved as incubation for rooting can be done in shade house thereby saving electricity c) As there is 4 weeks saving in hardening, shade house space could be utilized for hardening more plants. The method could be adopted for hardening in small nurseries to large industries and can result in cost reduction of plantlets. Saving of 4 weeks for hardening will be highly beneficial to the micropropagation industries for delivering plants to farmers in time during peak planting seasons. Plant Tissue Cult. & Biotech. 34(1): 11-24, 2024 (June)

Development and Performance Analysis of Commercial Vehicle Axle Shaft

Axle shafts, which are an important part of the vehicle's powertrain system, transfer the torque to the wheels and enable the vehicle to move. In this respect, the design of the axle shaft to be used in a new vehicle is of great importance for vehicle manufacturers. When a cylindrical shaft is torsionally loaded, the shear stress is highest at the surface of component and zero at the center. Therefore, these axle shafts are exposed to an induction hardening process that enables only this superficial case to have its properties changed, remaining the core zone with its material original characteristics. Current study presents the results of a project aimed at developing and evaluating the fatigue life of axle shaft that belongs to a commercial vehicle. Developments were made on the existing axle and the results were examined using experimental tests and finite element analysis method. In line with the improvements made, the developed axle shaft has 331.7% more fatigue life than the existing axle, while the cost is 24% lower. According to these results, more attention must be paid to material selection, induction hardening process, stress concentration and surface condition of axle shaft in the design. This study involves many disciplines such as design, manufacturing, analysis, testing, etc. It is very important to ensure communication between all these disciplines in the production of the product. The output obtained from one discipline becomes the input of another discipline. In the cumulative sum of all these inputs, the optimum level of parts is obtained. For this reason, this study, which processes all these disciplines together, is very valuable.

Влияние параметров плазменного упрочнения на качество поверхностного слоя тяжелонагруженных изделий

There has been studied the effect of the hardening current, the distance between the nozzle and the hardened surface of the product, the flow rate of the plasma-forming gas, the dependence of the cooling rate during plasma hardening on the speed of the plasma torch movement (treatment speed), and the diameter of the nozzle. Based on the theory of thermal processes, the cooling rates have been calculated for various values of the current strength. It has been shown that the ratings characterizing the significance of the main technological parameters of the plasma hardening mode for the depth and width of the hardened zone are practically the same. While the effect of the current strength on the dimensions (depth and width) of the plasma hardening zone significantly exceeds the effect of the other parameters of the hardening mode. This indicates that the arc current is the main controlled parameter of the plasma hardening process. There has been shown the possibility of regulating the mechanical properties of the hardened surface of the solid-rolled railway wheel rim depending on the required level of mechanical characteristics by means of controlling the speed of the wheelset.

STRENGTHENING OF THE SURFACE BY FRICTION

The study is devoted to the application of the method of surface hardening by friction Object of study - the process of surface hardening by friction.Subject of study - samples of 65G steel the method allows achieving high values of hardness, strength and wear resistance of materials in a short time and at much lower cost compared to other processing methods. The aim and objectives of the study are to investigate the nature of surface hardening of steel samples by friction. To achieve this goal, the following tasks are envisaged: manufacturing samples from 65G steel in the form of plates, preliminary heat treatment of samples for their maximum thermal hardening, hardening of the surface of samples by friction, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness and depth of hardening of these samples, conclusions on the influence of processing factors on the hardening result. Based on the experimental data obtained, we constructed graphs of microhardness changes in the cross-section of the samples and studied the microstructures. It can be seen that after friction treatment, a layer with a modified structure is formed in the surface of the samples. The microhardness of the surface is significantly higher (approximately 2 times) than the microhardness of the main part in the samples. Metallographic analysis has shown that the layer formed in the samples has a martensitic structure characterized by a higher degree of dispersion and microhardness compared to the martensitic structure obtained during the previous heat treatment. Changes in the microstructure and microhardness of the samples that were surface hardened using different processing modes were compared. Certain differences in the characteristics of their hardened «white» layers were found. It is also shown that the hardened «white» layer is located along the entire length of the surface in the samples and is continuous and homogeneous.

Tissue-Specific Quantification of Radiation-Induced Cervical Fibrosis and Correlation with Cervical Range of Motion.

Cervical fibrosis (CF) as a late consequence in patients after radiotherapy significantly impacts the long-term symptoms, functionality, and quality of life of these cancer patients due to a hardening process of different histological tissues. Modern Shear Wave Ultrasound Elastography now enables a differentiated analysis of the changes in various tissue types. In this study, tissue-specific changes in CF induced by radiation therapy in head and neck (ENT) cancer patients were quantified and correlated with cervical range of motion (CROM). 16 patients after radiation of the cervical lymphatic drainage were selected as the observation group (OG). Further, 16 people without radiation in the head and neck region were matched by gender, age, and BMI as the control group (CG). Stiffness measurements in kilopascal (kPa; 1 Pa = 1 N m-2) were performed using shear wave elastography (SWE) to assess the elasticity of muscle, fascia, and subcutaneous tissue within and surrounding the sternocleidomastoid muscle (SCM). Specific parameters of the OG were compared to the CG and correlated with functional parameters and quality of life (QoL). The OG exhibited significantly higher stiffness values (Emean, Emax, Emin) across all tissue types than the CG, suggesting a tangible effect of radiation therapy on tissue stiffness. Muscle compartment analysis revealed the most significant stiffness differences. Thickness measurements indicated changes in the muscle and skin but not in the subcutaneous tissue. CROM measurements within the OG fell within normal ranges, suggesting a possible homogenizing effect of radiation treatment on CROM variability. Strong correlations were observed between age and specific stiffness measures, particularly in the OG group, indicating a broader impact of aging or radiation therapy on physiological measures. Significant correlations between tissue stiffness and CROM were found. CF after radiotherapy occurs primarily in the muscle tissue and its fascia, with the hardening being about twice as pronounced as in the average population and becoming more pronounced with increasing age and correlates with CROM.

Optimized Compound Layer Design for Highly Loaded Nitrided Gears

AbstractNitriding is a thermochemical surface hardening process, which can be used to improve the performance properties of gears. In particular, the tooth flank and tooth root load-carrying capacity can be significantly increased by nitriding. Previous work has shown that tribological dominated failure modes and limits, such as the micro-pitting and wear load-carrying capacity of gears, can be significantly increased by a suitable compound layer structure. In this work, the relationship between compound layer design and macro-pitting load-carrying capacity of nitrided gears is explored based on experimental investigations. For this purpose, the materials EN31CrMoV9 and EN42CrMo4 were nitrided under varying nitriding conditions to produce compound layers with different structures and properties. The characteristics of the compound layer such as phase composition, compound layer thickness and pore seam were extensively characterized by means of metallographic techniques, XRD, GDOES, and EBSD. Experimental investigations of the macro-pitting load-carrying capacity were carried out on an FZG back-to-back gear test rig with center distance a = 52 mm. It was shown that the pitting load-carrying capacity depends to a large extent on the characteristics of the compound layer, in particular on the formation of the pore seam. A minimum pore seam thickness of CLTP ≥ 1.8 µm has a positive effect on the pitting load-carrying capacity. The test results for the pitting load-carrying capacity are above (σH lim ≥ 1690 N/mm2) or, in some cases, significantly above (σH lim = 1979 N/mm2) the strength values specified in ISO 6336-5:2016 for nitrided nitriding steels (σH lim = 1450 N/mm2; material quality ME) and case-hardened alloy steels (σH lim = 1650 N/mm2; material quality ME).

Effect of pulse current density on creep ageing behavior of 2195 Al-Li alloy

Electrical pulse-assisted creep ageing forming can effectively improve the mechanical properties and forming efficiency of large aluminum components. However, it is difficult to achieve uniform and consistent current density at different positions in complex components. Thus, the creep behavior, mechanical properties, and microstructure evolution of 2195 Al-Li alloy under three pulse current densities (0A/mm2, 3A/mm2 and 8A/mm2) was systematically studied. The experimental results showed that the creep deformation increases with increasing current density during the 1st hour stage of electric pulse-assisted creep ageing process. However, the total creep strain of 8 h shows a trend of decreasing and then increasing. Low density pulsed currents (non-thermal effect) can promote the precipitation of the T1 phases and θ′ phases, and narrow the precipitates free zone compared to conventional creep aged sample (0A/mm2). High density (Both of non-thermal effect and Joule heating effect) pulsed currents can promote the precipitation of T1 phases, inhibit θ′ phases and form the precipitated phase penetrate the grain boundaries. A gratifying finding is that an increase in current density accelerates the aging hardening process, but the peak strength after creep ageing is the same for different current densities. This indicates that high pulse current density can improve creep ageing forming efficiency and ageing hardening process, and can use non-uniform current densities to solve the problem of significant differences in overall structural component formability while maintaining final performance consistency.

Tribological and Mechanical Behavior of Automotive Crankshaft Steel Superficially Modified Using the Boriding Hardening Process

One of the primary challenges in the automotive industry is the wear of engine components, such as the crankshaft and camshaft, which is the most pronounced during the engine’s startup phase, when the amount of lubricant fluid is at its lowest. This study aims to enhance the surface wear resistance of automotive crankshaft steel by applying a boriding thermochemical process. This process forms a hard surface layer on the steel, improving its mechanical properties and bolstering its wear resistance, especially under dry conditions. Boride layers were achieved using the powder-pack boriding process in a conventional furnace, with meticulous treatment times of 2, 4, and 6 h at a constant temperature of 950 °C. The nature of the layers was analyzed using X-ray diffraction, and their tribological behavior was evaluated using the pin-on-disk test. The growth of the layers was directly proportional to the treatment time and was estimated at 145 µm and 48 µm for the 6 and 2 h of treatment, respectively. The surface hardness increased from 320 HV for the non-treated steel to 2034 HV for the sample exposed to 950 °C for 6 h. The results indicate a significant reduction in the coefficient of friction from 0.43 for the non-treated steel to 0.12 for the samples exposed to 950 °C for 6 h, suggesting potential wear protection during the engine starting period.

Orthologs of NOX5 and EC-SOD/SOD3: dNox and dSod3 Impact Egg Hardening Process and Egg Laying in Reproductive Function of Drosophila melanogaster.

The occurrence of ovarian dysfunction is often due to the imbalance between the formation of reactive oxygen species (ROS) and the ineffectiveness of the antioxidative defense mechanisms. Primary sources of ROS are respiratory electron transfer and the activity of NADPH oxidases (NOX) while superoxide dismutases (SOD) are the main key regulators that control the levels of ROS and reactive nitrogen species intra- and extracellularly. Because of their central role SODs are the subject of research on human ovarian dysfunction but sample acquisition is low. The high degree of cellular and molecular similarity between Drosophila melanogaster ovaries and human ovaries provides this model organism with the best conditions for analyzing the role of ROS during ovarian function. In this study we clarify the localization of the ROS-producing enzyme dNox within the ovaries of Drosophila melanogaster and by a tissue-specific knockdown we show that dNox-derived ROS are involved in the chorion hardening process. Furthermore, we analyze the dSod3 localization and show that reduced activity of dSod3 impacts egg-laying behavior but not the chorion hardening process.

Comparative Analysis of Wear Behavior of High Entropy Alloy (TiVNbCrAl) and Ti-based Conventional Alloy (TiNbCrCoAl)

This research examined the relationships between processing, structure, and property at both room temperature and increased temperature for two BCC high entropy alloy (TiVNbCrAl) and Ti-based conventional alloy (TiNbCrCoAl) prepared using standard arc melting. Both alloys have been determined to have the BCC single-phase solid solution structure. To investigate the hardness and tribological behavior and processes at room temperature and above, microindentation and sliding wear experiments were undertaken. Both alloys display comparable friction behavior when sliding at room temperature, with an average steady-state coefficient of friction (COF) of 0.6. When sliding temperatures rise to 302 °C, the average COF for HEA (TiVNbCrAl) has decreased to a lowest value of ~0.4 due to the creation of a persistent tribochemical layer made of Nb and Cr oxides amid the sliding surfaces, which lowers COF. Whereas, COF for Ti-based conventional alloy remains at higher values of ~0.65. Mechanistic wear analyses revealed that the formation of tribofilms with low interfacial shear strength inside the wear tracks was the cause of this. The tribofilms were identified to be mostly constituted by multi-element solid solution oxides, such as Ni2O5, Cr2O3, and NiO2, according to Raman spectroscopy. The Vickers microharness values for Ti-based conventional alloy is about 365±4 HV. Whereas, for high entropy alloy is about 572±12 HV due to the solid solution strengthening.

Optimization of Al2O3 nanoparticle concentration and cutting parameters in hard milling under nanofluid MQL environment

The high cutting heat and cutting forces are still the big obstacles in hard machining technology, which puts more pressure to find out the alternative solution for these problems. The work content presents an experimental study on the effect of nanoparticle concentration and cutting parameters on surface roughness and cutting force during hard milling under MQL environment using Al2O3 nano-cutting oil. The Box-Behnken experimental designs for response surface methodology was used to evaluate the influence of the input parameters and determine the optimal values. The obtained results show that the nanoparticle concentration, cutting speed, and feed rate all have the great influences on surface roughness R z and resultant cutting force F, so the study of the influence of these parameters on the efficiency of the hard milling process is very significant. The proposed reasonable value ranges will help technicians quickly choose to meet their demands for specific objective functions. Furthermore, the optimal parameter set of nanoparticle concentration of 1.27 wt%, cutting speed V c = 103 m/min, and feed rate [Formula: see text] = 0.09 mm/tooth was determined. It revealed that the use of MQL with nano-cutting oils contributed to improve the lubrication and cooling performance in the cutting zone.

An Experimental Investigation of Cutting Condition Influences on Hard Milling of AISI D2 Tool Steel

The presented work aims to study the effects of cutting speed, feed rate and depth of cut on surface roughness Ra in hard milling of AISI D2 steel (58 ÷ 60 HRC) using carbide inserts. A factorial experimental design was used to evaluate the influence of input variables. The obtained results indicated that feed rate causes the most significant effect on surface roughness, whereas cutting speed and depth of cut have little influence. The interaction effects between cutting speed and depth of cut as well as between feed rate and depth of cut have the significant influences on surface roughness Ra. Moreover, the cutting speed of 92 ÷ 100 m/min, feed rate of 0.1 ÷ 0.11 mm/tooth, and cutting depth of 0.1 ÷ 0.12 mm should be recommended for reaching the smaller surface roughness Ra values, which play an important role for further studies on hard milling process.

Denoising Ambulatory Electrocardiogram Signal Using Interval Dedependent Thresholds based Stationary Wavelet Transform

Noise contamination in electrocardiogram (ECG) monitoring systems can lead to errors in analysis and diagnosis, resulting in a high false alarm rate (FAR). Various studies have been conducted to reduce or eliminate noise in ECG signals. However, some noise characteristics overlap with the frequency range of ECG signals, which occur randomly and are transient. This results in shape alteration and amplitude reduction in P and R waves. The author proposed a framework for eliminating noise in ECG signals using the stationary wavelet transform method and interval-dependent thresholds (IDT) based on the change point detection method to address these challenges. The proposed framework decomposes the input electrocardiogram (ECG) signal at a specific level using the Stationary Wavelet Transform method, resulting in detail and approximation coefficients. Interval detection focuses on the initial detailed coefficient, d1, chosen due to its significant content of noise coefficients, especially high-frequency noise. Subsequently, threshold values are computed for each interval. Hard and soft thresholding processes are then applied individually to each interval. Finally, reconstruction occurs using the inverse stationary wavelet transform method on the threshold coefficient outcomes. Two measurement matrices, root mean square error (RMSE) and percentage root mean squared difference (PRD), were used to measure the performance of the proposed framework. In addition, the proposed framework was compared to stationary wavelet transform (SWT) and discrete wavelet transform (DWT). The test results showed that the proposed method outperforms DWT and SWT. The proposed framework obtained an average increase in RMSE scores of 18% and 45% compared to the SWT and DWT methods, respectively, and PRD values of 17% and 37% compared to the SWT and DWT methods, respectively. So, using IDT in the stationary wavelet transform method can improve the denoising performance. With the development of this new framework for denoising ECG signals, we hope it can become an alternative method for other researchers to utilize in denoising ECG signals.

EPB-TBM cutterhead torque and thrust modelling in rock tunnels through an analytical method and TSFS model

The analysis of cutterhead torque and thrust force is of utmost importance in the selection of a proper tunnel boring machine (TBM) and in achieving optimal operation of the earth pressure balance (EPB) machine for a specific project. This study focuses on the analysis of cutterhead torque and thrust force using data collected from the recent metro project of Tehran, specifically the southern extension of Tehran metro line 6, (TML6-SE). To assess the impact of geotechnical and operational parameters on the measured torque and thrust, a database consisting of 457 data points was established. The excavation of a significant portion of the project took place in a dense and robust limestone using a refurbished EPB machine with a diameter of 9.19 m, initially designed for soft ground excavation. To complete this section of the tunnel, the cutterhead was equipped with disc cutters instead of rippers. Consequently, existing theoretical models for estimating torque and thrust of an EPB machine were modified to accommodate the hard rock boring process. Additionally, the Takagi-Sugeno fuzzy system (TSFS) was utilized in this study. The results of the models yielded quantitative conclusions, and the comparison between the measured and predicted target parameters demonstrated high accuracy. This study contributes to the understanding of the influence of various parameters on the performance of EPB machines in hard rock boring conditions, as well as providing insight into the potential adjustments needed in theoretical models for predicting cutterhead torque and thrust force. The proposed models showed satisfactory and reliable accuracy, with all models having an R2 value above 0.7 and loss function values nearing zero.

Austenitizing Temperature and Quenching Media Effects on Hardness and Microstructure in Hardening of AISI 1040 Steel

Hardening process is an important to make materials have harder properties related to wear resistance. This research determined the effects of austenitizing temperature and quenching media on the hardness and microstructure of AISI 1040. The austenitizing temperatures varies at 850°C, 900°C, and 950°C with PVA 10%, SAE 20W-50 oil, and salt water as quenching media. The method to measure hardness was the Brinell hardness test. The results showed changes in the microstructure from untreated steel with the structures of ferrite and pearlite to bainite and martensite. The highest hardness value of 416.22 kgf/mm2 was obtained in specimens with salt water media at an austenitizing temperature of 850°C.

AN ENHANCEMENT IN THE COPPER ELECTRODE WEAR CHARACTERISTIC ELECTRICAL DISCHARGE MACHINED INCONEL 718 THROUGH ION NITRIDING, LASER SURFACE HARDENING AND HYBRID PROCESS

The virgin copper electrode has limited application due to its wear and mechanical properties using Electrical Discharge Machined (EDMed) on Inconel 718 superalloys. In order to enhance the performance of copper electrodes, in this work, Ion Nitriding (IN), Surface Hardening by Laser (LSH) and Hybrid Process ([Formula: see text]) are performed on copper electrodes to reduce the electrode wear in frontal and lateral. The electrode wear in the frontal and lateral of virgin copper electrode is processed and studied using EDM with varying pulse durations, current and Silicon Carbide (SiC) mixed EDM oil. The surface hardness in virgin and processed electrodes is also investigated. Overall analysis found that the hybrid technique produced a 59% higher hardness than that of virgin copper. The hardness in the EDMed surface was higher than that of the processed copper surface. A 1000[Formula: see text][Formula: see text]s pulse duration, 2 A current and 15 g/l SiC powder mixing EDM oil produced a low frontal wear in both virgin and processed copper electrodes. The electrode wear was reduced by 30% for frontal and 76% for lateral using a hybrid method.

Preparation of asymmetrical cutting edge geometries on micro end mills using pressurized wet abrasive jet machining for hard micromachining of AISI M3:2

Cutting edge preparation is an established approach in the field of machining technology for optimizing the performance of cutting tools. However, the potential of asymmetric geometries has not yet been sufficiently utilized for filigree micromilling tools. In this regard, the study presents investigations on the adjustment of asymmetric microgeometries through the design of the pressurized air wet abrasive jet machining (PAWAJM). The study features results regarding the design of the preparation process as well as subsequent application tests in a hard micromilling process of the hardened high-speed steel AISI M3:2. The application tests focus on the effect of the conditioned cutting edge on the process forces and the surface quality as well as the tool life. The results show that asymmetrical microgeometries with small average cutting edge rounding and a form-factor of K > 1.2 can be achieved by PAWAJM. Machining tests revealed a potential reduction of the wear development and process forces for modified tools with low cutting edge rounding and asymmetrical microgeometry.

Machine learning models for enhanced cutting temperature prediction in hard milling process

Machine learning models for enhanced cutting temperature prediction in hard milling process

Comparative analysis of mechanical conditions in bone union following first metatarsophalangeal joint arthrodesis with varied locking plate positions: A finite element analysis.

First metatarsophalangeal joint arthrodesis is a typical medical treatment performed in cases of arthritis or joint deformity. The gold standard for this procedure is arthrodesis stabilisation with the dorsally positioned plate. However, according to the authors' previous studies, medially positioned plate provides greater bending stiffness. It is worth to compare the mechanical conditions for bone formation in the fracture callus for both placements of the locking plate. Two finite element models of the first metatarsophalangeal joint with the dorsally and medially positioned plate were defined in the Abaqus software to simulate differentiation of the fracture callus. A simplified load application, i.e. one single step per each day and the diffusion of the mesenchymal stem cells into the fracture region were assumed in an iterative hardening process. The changes of the mesenchymal stem cells into different phenotypes during the callus stiffening were governed by the octahedral shear strain and interstitial fluid velocity according to Prendergast mechanoregulation theory. Basing on the obtained results the progress of the cartilage and bone tissues formation and their distribution within the callus were compared between two models. The obtained results suggest that after 6 weeks of simulation the healing progress is in general comparable for both plates. However, earlier closing of external callus was observed for the medially positioned plate which had greater vertical bending stiffness. This process enables faster internal callus hardening and promotes symmetrical bridging.

Pasta Drying Defects as a Novel Ingredient for Hard Dough Biscuits: Effect of Drying Temperature and Granulation on Its Functionality.

Various drying temperatures impact the texture of pasta and cause different drying defects. These by-products could reflect techno-functional characteristics which are suitable for cereal products. This research addresses the influence of low (LT) and high (HT) drying pasta defects with two granulations on the theoretical and functional characteristics of hard dough biscuits. By shifting from a LT to HT drying temperature, a higher onset and peak temperature was found due to the higher mobility of starch molecules with increasing crystalline stability. The lowest transition enthalpy of biscuit formulation was also observed for higher incorporation of fine HT pasta regrinds. The algebraic model of dough with consistography determined the poor-extensible gluten and a high resistance with a greater value of P/L and P indices for LT regrinds. Scanning electron microscopy revealed a heavy and dense texture with immersed starch granules for additional fine regrinds while coarse samples caused swell granules with greater diameter. Moreover, fine HT regrinds reflected the lowest L* value for biscuit due to heat gradient tension with the hard milling process which leads to protein denaturation with decreasing nitrogenous.