Experimental study of burn classification and prediction using indirect method in surface grinding of AISI 1045 steel

Grinding burn is a discoloration phenomenon according to the thickness of oxide layer on the ground surface. This study tries to establish an automatic grinding burn detection system with robust burn features that are caused by burn and not by the design parameters. To address this issue, a method based on acoustic emission sensor, accelerator, electric current transducers, and voltage transducers was proposed in an attempt to extract burn signatures. A trial-and-error experimental procedure was presented to find out burn threshold. Vitrified aluminum oxide grinding wheel and AISI 1045 steel workpiece were used in the grinding test, as they were the most commonly used wheel–workpiece combinations in conventional grinding process. With the help of fast Fourier transform and discrete wavelet transform, the spectral centroid of AE signal, the maximum value of power signal, and the RMS of the AE wavelet decomposition transform from wavelet decomposition levels d1 to d5 were extracted as burn features. The spectral centroid of AE signal was believed not to be affected by grinding parameters. A classification and prediction system based on support vector machine was established in order to identify grinding burn automatically. Results indicate that the classification system performs quite well on grinding burn classification and prediction.     

Weldability and joining characteristics of AISI 430/AISI 1040 steels using keyhole plasma arc welding

AISI 430 and AISI 1040 steel couples were welded using the keyhole plasma-transferred arc (KPTA) welding process. Welded joints were manufactured using three different traverse speeds (0.01, 0.02 and 0.03?m/min) under three different welding currents (130, 135 and 140 A) at a constant plasma gas flow rate (1.1?l/min) and a shielding gas rate (25?l/min). In order to determine the microstructural changes that occurred, the interface regions of the welded specimens were examined by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive Spectrometry (EDS) after KPTA welding. Microhardness, V-notch Charpy and tensile tests were conducted to determine the mechanical properties of the welded specimens.     

Microstructural studies and impact toughness of dissimilar weldments between AISI 316 L and AH36 steels by FCAW

In this study, AISI 316 L austenitic stainless steel and AH36 low-alloy ship building steel pair were joined with flux-cored arc welding method by using E309LT1-1/4 filler metal under four different shielding gas compositions containing CO₂ at different ratios. Microstructure, impact toughness of welded materials, and their microhardness distribution throughout joining were determined. In macro- and microstructure examinations, stereo optical microscope, scanning electron microscope (SEM), SEM/energy dispersive spectroscopy, and SEM/mapping analysis techniques were used. After notched impact toughness, fracture surfaces were examined using the scanning electron microscope. This study investigated effects of shielding gas composition on microstructure, impact toughness, and microhardness distribution of transition zone between AH36 steel and weld metal of joined material. It is observed that based on an increase in amount of CO₂ in shielding gas, impact toughness values of the weldment decreased. Microhardness values change throughout weld metal depended on shielding gas composition. Moreover, an increase in amount of CO₂ within shielding gas decreased δ-ferrite amount in weld metal. The increase in amount of CO₂ within shielding gas leads to expanded transition zone in interface between AH36 and weld metal and also affects notched impact toughness values negatively due to the inclusion amounts occurring in weld metal and hence caused it to decrease.     

Assessment of white layer in hardened AISI 52100 steel and its prediction using grinding power

In the present work, the effect of various grinding mechanisms on white layer (WL) formation in AISI 52100 steel is studied using two types of alumina grains, one produced by sol–gel process and the other by conventional fusion. Further, a novel approach is proposed on predicting the WL formation using grinding power. This study correlates the power variation with the change in the metallurgical aspects of the work material. WL of about 56 µm thickness is observed in the material ground by worn out sol–gel alumina wheel. However, no WL is present in the material ground by fused alumina wheel. High toughness in sol–gel alumina led to generation of wear flats with increasing grinding passes and transformed the dominant grinding mechanism from shearing to plowing and sliding. This increases the temperature in the grinding zone, which was the reason for WL formation. Change in the dominant grinding mechanisms from shearing is found to increase the grinding power. Since the change in dominant grinding mechanisms is the cause for WL formation, the increase in grinding power is found to be a good measure in predicting the WL formation. The predictability of WL formation by grinding power is further validated by comparing the power variation in grinding process by both the grinding wheels.     

Wear resistance of steels and suction-tube dredger members hardened by surface electrolysis borating during abrasive wear

Findings of comparative bench tests for six grades of carbon and alloyed structural steels hardened by surface electrolysis borating and data of the reliability for borated members under field conditions within a heterogeneous abrasive environment and for borated scoop pins in hinged joints of a scoop chain of a suction-tube dredger are presented.     

MQL平面磨削参数的分析与优化

在最小量润滑(minimum quantity lubricant)方式下,通过磨削区的有效流体流量及磨削区产生的流体动压力对加工参数、砂轮及工件都会产生影响,很多参数需要校正优化.为了获得较高的加工质量、优化的参数和较低的成本,应用了正交设计法、信噪比分析法和方差分析法.     

Some metallurgical factors controlling the adhesive and abrasive wear resistance of steels. A review

Many operating difficulties and loss of production in industry arise through wear. When it occurs, it does so to a degree that is somewhat unpredictable in purely quantitative terms. Presenting the problem from the practical metallurgical point of view suggests a basis on which to specify the wear resistance of steel, both constitution and metallurgical structure appearing as fundamental factors in the determination of wear properties. The known metallurgical parameters which influence the performance of steels in adhesive and abrasive wear situations are presented. Hardness, as a criterion of wear resistance is also discussed. The influence of metallurgical structure on wear resistance is covered in some detail, in particular interstitial compounds, size shape and distribution, chemical composition and the effect of alloy additions, nature of the matrix and the effect of different heat treatments.     

Optimization of drilling parameters on surface roughness in drilling of AISI 1045 using response surface methodology and genetic algorithm

Modeling and optimization of cutting parameters are one of the most important elements in machining processes. The present study focused on the influence machining parameters on the surface roughness obtained in drilling of AISI 1045. The matrices of test conditions consisted of cutting speed, feed rate, and cutting environment. A mathematical prediction model of the surface roughness was developed using response surface methodology (RSM). The effects of drilling parameters on the surface roughness were evaluated and optimum machining conditions for minimizing the surface roughness were determined using RSM and genetic algorithm. As a result, the predicted and measured values were quite close, which indicates that the developed model can be effectively used to predict the surface roughness. The given model could be utilized to select the level of drilling parameters. A noticeable saving in machining time and product cost can be obtained by using this model.     

The effect of the severity of the grinding mode on the wear characteristics of grade 36 Al2O3- and Al2O3-ZeO2-coated abrasive belts

With the trend toward increased production rates, demands on coated abrasive belts are becoming increasingly severe. A study was made of the wear and performance characteristics of two abrasive minerals used in two very different modes of grinding, a low pressure constant-load grinding test (to represent relatively mild grinding and finishing applications) and a high pressure constant-rate test (to represent severe machining applications). Al₂O₃ and Al₂O₃-ZrO₂ minerals in a resin-bonded cloth-backed construction generally used for most metal-working applications were studied.A variety of techniques were used to analyze and to define wear and grinding performance. These included the measurement of the caliper, energy consumption, mineral utilization and surface profiles of the belts, together with scanning electron microscopy (SEM) observations of belts at various stages of wear. Substantial differences were found in many areas, both for the two mineral types used in the same grinding mode and for the same mineral used in different grinding modes. Interesting data showing mineral consumption during the grinding process and SEM visual identification of key differences in coated abrasive wear are presented. The study indicates that, although a coated abrasive belt can function effectively over a wide range of applications, its wear characteristics will vary with the severity of the application.     

Ultra-precision grinding of optical glasses using mono-layer nickel electroplated coarse-grained diamond wheels. Part 2: Investigation of profile and surface grinding

After finishing the precision conditioning of mono-layer nickel electroplated coarse-grained diamond wheels with 151 μm (D151), 91 μm (D91) and 46 μm (D46) grain size, resp., profile and surface grinding experiments were carried out on a five-axis ultra-precision grinding machine with BK7, SF6 optical glasses and Zerodur glass ceramic. A piezoelectric dynamometer was used to measure the grinding forces, while an atomic force microscopy (AFM), white-light interferometer (WLI)) and scanning electron microscope (SEM) were used to characterize the ground surface quality in terms of micro-topography and subsurface damage. Moreover, the wear mechanics of the coarse-grained diamond wheels were analyzed and the grinding ratio was determined as well, in aiming to evaluate the grinding performance with the conditioned coarse-grained diamond wheels. Finally, the grinding results were compared with that of the fine-grained diamond wheels with regard to the ground specimen surface quality, process forces and wheel wear as a function of stock removal. The experimental results show that the precision conditioned coarse-grained diamond wheels can be applied in ductile mode grinding of optical glasses with high material removal rates, low wheel wear rates and no dressing requirement yielding excellent surface finishes with surface roughness in the nanometer range and subsurface damage in the micrometer range, demonstrating the feasibility and applicability of the newly developed diamond grinding technique for optical glasses.     

A study of abrasive wear mechanisms using diamond and alumina scratch tests

Scratch tests using alumina (Al₂O₃) abrasive particles and Vickers diamond pyramids were employed to study material removal mechanisms in the abrasion of cobalt-base powder metallurgy alloys 6 and 19. The alloys were specially prepared to produce either fine or coarse carbides in order to study the effects of carbide size. Scanning electron microscopy was used to analyze the scratch grooves, the scratch tools and the wear debris particles.

Comparison of scratch tests with Al₂O₃ and diamond pyramids shows that many features produced by the extremely hard regularly shaped diamond tools are different from those produced by irregular Al₂O₃ particles. Except for differences produced by tool wear, multiple-pass Al₂O₃ scratch tests provide excellent reproduction of the material removal processes which occur in low stress Al₂O₃ abrasion. Al₂O₃ scratches produced both chip-like and fine irregular debris particles similar to those extracted from spent abrasive used in wear testing.

Material removal in the fine carbide alloys is facilitated by the direct removal of entire carbides within the volume of micromachining chips removed from the scratch groove. In coarse carbide alloys, machining chips from large carbides are observed, but the depth of cut in the carbide phase is less than that in the f.c.c. matrix and this leads to a decrease in the volume of material removed. Direct comparison of chips removed from fine and coarse carbide alloys by the same Al₂O₃ particle shows larger chips from the fine carbide material.

The effects of subsurface deformation and surface irregularities on material removal were studied by carrying out scratch tests on specimens subjected to prior abrasion and by investigating multiple-pass scratches in the same scratch groove.     

Predicting surface roughness of hardened AISI 1040 based on cutting parameters using neural networks and multiple regression

In this study, models for predicting the surface roughness of AISI 1040 steel material using artificial neural networks (ANN) and multiple regression (MRM) are developed. The models are optimized using cutting parameters as input and corresponding surface roughness values as output. Cutting parameters considered in this study include cutting speed, feed rate, depth of cut, and nose radius. Surface roughness is characterized by the mean (R _a) and total (R _t) of the recorded roughness values at different locations on the surface. A total of 81 different experiments were performed, each with a different setting of the cutting parameters, and the corresponding R _a and R _t values for each case are measured. Input–output pairs obtained through these 81 experiments are used to train an ANN is achieved at the 200,00th epoch. Mean squared error of 0.002917120% achieved using the developed ANN outperforms error rates reported in earlier studies and can also be considered admissible for real-time deployment of the developed ANN algorithm for robust prediction of the surface roughness in industrial settings.     

外锥面砂轮实现内锥面刃磨钻头的方法

提出了利用外锥面砂轮实现内锥面刃磨钻头的方法,设计了实现该方法的连杆齿轮组合机构。克服了用成型砂轮实现麻花钻的内锥面刃磨时,小直径尺寸的麻花钻无法磨削的缺点,同时又能提高麻花钻的刃磨效率和刃磨质量。     

Application of Taguchi coupled Fuzzy Multi Attribute Decision Making (FMADM) for optimizing surface quality in turning austenitic and duplex stainless steels

In the present study, Taguchi approach is coupled with fuzzy-multiple attribute decision making methods for achieving better surface quality in constant cutting speed face turning of EN 1.4404 austenitic, EN 1.4462 standard duplex and EN 1.4410 super duplex stainless steels. Two typical multiple attribute decision making techniques were simultaneously adopted to determine multi-surface quality characteristics indices. The differences in rankings among derived indices are solved through converting each crisp values into trapezoidal fuzzy number and unifying them using fuzzy simple additive weight method. The fuzzy numbers are then deffuzified into crisp values employing techniques like; the spread, mode and area between centroid of centroids. Through this procedure, the decision maker is provided with necessary decision tools to optimize the cutting conditions with less sensitivity to the change of weights and no difference in ranking among the deffuzification techniques. Additionally, results of analyses of means and the validation experiments confirm that the optimum cutting conditions derived by this method produce far better surface finish than the best finish obtained during the course of experimentation. Analyses of variance results have shown the predominant effect of feed rate on surface quality. Finally, the collected chip at constant cutting speed and varying feed rates and depth of cuts has shown that friendlier-to-machine chips are obtained when machining austenitic stainless steels than duplex stainless steel grades.     

Improvement in dynamic characteristics of surface grinding machines with a horizontal spindle and a reciprocating work-table by means of a new type of dynamic damper

A number of types of dynamic damper for surface grinding machines with a horizontal spindle and a reciprocating work-table are developed and their effectiveness is investigated experimentally. In all cases, the amplitudes of the tuning-fork mode vibrations of the machines were reduced to about one-fifth of the values in the original states, and chatter marks due to these vibrations have been suppressed completely. In particular, a multi-degrees-of-freedom two-directional type dynamic damper has excellent adaptability to the variation in the dynamic characteristics of the surface grinding machines during machining operations and is also effective in suppressing the horizontal vibration of the wheel-head.