Machining Damage Research Articles

Scratching of SiC ceramics at two dimensional pre-stressing

A stress field model was built to study the effects of pre-stressing value, normal and tangential load on the three principal stresses and maximum shear stress when the silicon carbide (SiC) ceramics were scratched under two dimensional pre-stressing, and the scratching tests of SiC ceramic were conducted by using a Rockwell diamond indenter at different pre-stress values and normal loads. Scratching induced damage was assessed and characterised via destructive inspection techniques and progressive lapping techniques combined with the digital microscope. Acoustic emission (AE) technology was also used for the online monitoring of the damage. The results showed that, for a given scratching load, the amplitude of AE signals was reduced as the pre-stress values increasing, and surface/subsurface damage of SiC ceramics induced by two dimensional pre-stress scratching was less than that by conventional scratching. So one can believe that the two dimensional pre-stress method can contribute to decreasing the machining damage of brittle materials.

Character and mechanism of surface micromachining for C/SiC composites by ultrashort plus laser

ABSTRACTA new surface micromachining way of ultrashort plus laser for C/SiC composites with high quality and efficiency was demonstrated, including picosecond and femtosecond laser. Surface morphologies, element content and bonding states of C/SiC composites were analysed in detail after machined by picosecond and femtosecond laser power respectively. For femtosecond laser machining, the amount of nanoparticles increased with increasing laser power. At 20 and 50 mW, Si–C, C–C and Si–O bonds existed in nanoparticles, while Si–C bonds disappeared at 70 mW. For picosecond laser machining, cauliflower-like particles and periodic ripple with certain depth were formed distinctly. Furthermore, thermal ablation phenomenon occurred, and only Si–O bonds existed in particles due to the oxidation of the carbon fibres and SiC matrix. The results showed that femtosecond laser with low power was more suitable to the surface machining due to better machining quality and less machining damage compared with high power picosecond laser.

Keandalan Sistem Lintasan Produksi Pembuatan Pipa

Production process of power pole involves connected production process flow between machines. Thus, the company must ensure the machine availability during production runs. PT Kunango Jantan as a company that produces pole power also considers machine availability. The level of machine availability can be seen from the high level of machine reliability. However, the company is still not been able to guarantee the availability of the machine so it is necessary to study the reliability of the system to help to take the right policy in handling pipe production machinery maintenance. The first step is to determine the distribution of machine damage. Minitab 16 software was used determine the type of distribution and distribution parameters of each machine damage. In addition, mean time between failure ( MTBF) was calculated to the pipe manufacturing machine. The machine reliability was obtained based on a formula and parameters. The determination of the system reliability was derived from the block diagram in accordance with the condition of machines in the field. The analysis was performed using fishbone diagram to propose an attempt to increase the machine reliability. The results of this study indicate that the machine reliability in good level since the reliability value is between 0.901 to 1.000. The machine reliability in a series circuit is smaller than the machine reliability in a parallel circuit. Rs and R values of the system were 0.980 and 0.998. R system shows that the system has a good performance with a chance of machine damage during production <0.002 (0.2%).

Mitigation of Fatigue Damage and Vibration Severity of Electric Drivetrains by Systematic Selection of Motion Profiles

The offshore drilling industry is among the most demanding markets for electrical equipment. Heave motion, irregular cyclic loads, harsh weather conditions, and vibrations are causing accelerated deterioration of drilling equipment. One of the most common solutions to these problems is to design actuation systems of such machinery overly conservative to gain additional safety, which results in too high initial investment and maintenance costs. To mitigate the fatigue damage and vibration severity of rotating elements of electric drivetrains operating offshore, this paper presents a comparative analysis of four popular input functions used in motion control of industrial systems. We evaluate them not only by using well-known performance indicators, such as maximum load or velocity, but also by assessing their influence on fatigue life and vibration severity of electric drivetrains. The rainflow counting algorithm is used to assign amplitudes and mean values of distinguished cycles from random loading history. Then, the Palmgren–Miner rule together with S–N curves are applied to determine the total damage for cycles with varying amplitudes. In addition, we quantify the cumulative effect of vibrations and jerk on machine damage by using the metric based on the jerk energy. The importance of this study is illustrated on a full-scale offshore pipe handling machine by benchmarking simulation results with the field data. The outcomes demonstrate not only a serious decrease in damage caused by vibrations for smooth motion profiles, but also provide a basis to formulate rules of thumb for selection of the most suitable motion profile for certain applications.

Unraveling the Age Hardening Response in U-Nb Alloys

Complicating factors that have stymied understanding of uranium-niobium’s aging response are briefly reviewed, including (1) niobium inhomogeneity, (2) machining damage effects on tensile properties, (3) early-time transients of ductility increase, and (4) the variety of phase transformations. A simple Logistic-Arrhenius model was applied to predict yield and ultimate tensile strengths and tensile elongation of U-4Nb as a function of thermal age. Fits to each model yielded an apparent activation energy that was compared with phase transformation mechanisms.

Monitoring for damage in two-dimensional pre-stress scratching of SiC ceramics

This paper reports an approach to use the acoustic emission (AE) technology for monitoring the surface/subsurface damage in twodimensional pre-stress scratching of SiC ceramics, in which the two-dimensional pre-stress is used to decrease the scratch-induced damage. Experiments in this study were conducted on a UMT-2 machine (CETR USA) utilizing a designed pre-stressing device under pressures of 0 MPa, 300 MPa and 500 MPa. The experimental results demonstrate that average frequency and magnitude of AE signals have a good correlation with the scratching tangential force and the scratch-induced surface /subsurface damage of materials. For a given normal load, the average frequency and magnitude of AE signals are observed to decrease with the increase in pre-stress, which indicates that surface/subsurface damage of SiC ceramics induced by two-dimensional pre-stress scratching is less than that induced by conventional scratching. The findings provide fundamental information for developing a practical on-line AE monitoring system that is effective in detecting surface/subsurface damage in scratching or grinding of ceramics. These results also demonstrate that two-dimensional pre-stress method contributes to decreasing the machining damage of brittle materials.

Yield, Fruit Damage, Yield Loss, and Juice Quality Characteristics of Machine- and Hand-harvested ‘Brown Snout’ Specialty Cider Apples Stored at Ambient Conditions in Northwest Washington

In this 2-year study, ‘Brown Snout’ specialty cider apples (Malus ×domestica) that had been hand harvested or machine harvested with an over-the-row shake-and-catch small fruit harvester were ambient stored (56 °F mean temperature) for 0, 2, and 4 weeks to evaluate yield, fruit damage, yield loss, and juice quality characteristics. The average yield (pounds per acre) of fruit picked and retained by the mechanical harvester was 74% that of the hand-harvest yield and 81% that of the hand-harvest yield when fruit that fell out of the harvester was included in the machine-harvest yield. Percent fruit bruised and cut were greater for machine harvest (97.5% and 25.5%, respectively) than for hand harvest (47% and 0.5%, respectively), on average for 2014 and 2015. Yield loss to rot was greater for machine harvest than for hand harvest, and increased for both methods over time; percent rot doubled from 2 to 4 weeks storage for machine harvest (22% to 41%), and while negligible, tripled from 2 to 4 weeks storage for hand harvest (0.7% to 2.1%). Juice quality characteristics did not differ due to harvest method, but did differ due to year and storage time. Soluble solids concentration [SSC (%)] and specific gravity (SG) did not change due to storage in 2014, but in 2015, SSC and SG were greater on average for 2 and 4 weeks storage duration (15% and 1.062, respectively) than at harvest (13.31% and 1.056, respectively). Titratable acidity (grams per liter malic acid) decreased in 2014 from 2.98 g·L−1 at harvest to 2.70 g·L−1 on average for 2 and 4 weeks storage duration, but did not differ due to storage in 2015. Tannin [tannic acid equivalent (%)] was unchanged in 2014 from harvest to 4 weeks storage, but increased in 2015 from 0.16% at harvest to 0.19% by 4 weeks storage. These results indicate that harvest efficiency could be improved with some engineering modifications of the over-the-row mechanical harvester and training modifications for the trees. A comparison of the aromatic and phenolic contents of mechanically harvested and hand-harvested ‘Brown Snout’ would be a valuable next step in evaluating shake-and-catch mechanical harvest technology for cider apple production.

The Impact of Thermal Degradation on Properties of Electrical Machine Winding Insulation Material

Interturn stator short circuits can develop quickly leading to serious damage of an electric machine. However, degradation mechanisms of winding insulation material are not yet fully understood. Therefore, the main contribution of this paper is the analysis of the impact of thermal ageing on the electrical properties of the thin-film winding insulation. The insulation samples have been aged thermally at 200 °C–275 °C and for 100–1600 h. After ageing, impedance spectroscopy measurements were undertaken on the samples and equivalent-circuit model (ECM) parameters fitted for each measurement. This allows the impact of thermal ageing on ECM parameters to be analyzed, giving insight into the changes in the electrical properties of the insulation. Finally, high voltage was applied to the samples aiming to identify the breakdown-voltage (BV) characteristics of the insulation material.

NC simulation for adaptive look-ahead interpolator with on-line collision detection

ABSTRACTThis paper proposes a numerical control (NC) machining simulation system with adaptive look-ahead interpolator and on-line collision detection function. Adaptive collision detection between tool and machine can be executed synchronously to avoid interference during the machining process. Traditional multi-axis machines are used to process free-form surfaces. However, determining how to check whether or not the machining path is correct remains a challenge. In path planning, determining how to avoid the wrong path resulting in the waste of materials and machine damage has become an important issue in the industry. Currently, most of planning use pre- processing simulation prior to actual machining aims to eliminate the wrong path that may result in collision. In this study, the efficiency of a developed multi-axis collision detection system is based on the computational complexity of possible collision parts. Hence, during simulation, the number of collision detections is variable and depends on th...

구멍들을 가진 표준 CT 시험편 내에서의 크랙 거동에 대한 해석적 연구

기계 혹은 구조물의 파손 및 파괴는 소재의 내부에 존재하는 결함에서 발생하는 크랙에 의한 것이다. 이러한 크랙들은 밀집하여 존재하는 경우가 많기 때문에 크랙의 진전 및 성장특성들을 고려하지 않으면 안 된다. 이에 따라 본 연구에서는 표준 CT 시험편 내부의 크랙 및 구멍의 위치에 따른 파괴특성을 고찰하였으며, 표준CT 시험편에 편심된 집중하중을 가하였을 때, 시험편 내 크랙 주변의 구멍의 존재유무 및 위치에 따른 파괴역학적 거동에 대하여 규명하였다. 연구 결과로서 Model 3(크랙 주변에 구멍이 한 개 존재하는 시험편 모델로서 크랙의 끝부분과 구멍 간의 거리 가로방향으로 2mm의 경우)가 최대 변형량, 최대 응력 및 최대 변형 에너지, 모두 가장 크게 나타났으며, 모든 시험편 모델들이 시험편 내부의 크랙과 구멍의 거리가 가까울수록 최대 응력이 커지는 경향을 보였다. 또한 구멍의 개수와는 별개로 시험편 내부의 크랙 가까이에 구멍이 존재할 때 크랙 가까이에서 최대 응력은 커지는 경향이 나타나는 것을 알 수 있었으며, 이러한 본 연구 결과를 토대로 기계 혹은 기계 구조물 내부에 구멍을 뚫는다면, 시험편에 발생하는 파괴 응력의 값을 줄임으로써 파손이나 고장이 일어나는 것을 방지할 수 있을 것으로 사료된다.

Study of high-tech process furnace using inherently safer design strategies (III) advanced thin film process and reduction of power consumption

Semiconductor manufacturing is the economic backbone of Taiwan. Although efforts have been made to improve production capacity and achieve full load production, manufacturers are still unable to effectively control the power consumption situation during the failure of full load production due to special circumstances. Those processes do not conform to the characteristics of inherently safer design, which increases process risks. The objective of this research was to investigate the effects of power consumption reduction on the process furnace, maintaining the same production capacity in the existing 22 nm advanced semiconductor process. In this study, TEOS was used as the raw material for LPCVD process simulation, experimentation, and exploration. The adopted LPCVD reactor was of the commercial batch type; the process experiments simulated the IPD process applied on the 22 nm MOSFET, with a thickness of 5000 Å and process time of 60 min. The simulation results of different batches were compared with the experimental values, and the simulation values were consistent with the experimental values by adjusting the different ka values. The reactor contained processes for 125 wafers and 100 wafers. According to the simulation and experimental results, the thin film deposition results were acceptable. Finally, the heating zone output current was explored specifically for two batches of wafers in the 12″ furnace tube process. In the process of the first batch, as there were only 100 wafers, 18.05 A was reduced by shutting off the 5th heating zone. The machine had a voltage of 220 V and converted power output up to 3971 W, accounting for 26% (15265.8 W) of the entire machine. This significantly reduced power supply of the entire machine and hazard potential, which is consistent with the characteristics of inherently safer design. Moreover, there were fifteen 12″ tube furnace machines in the experimental workshop of this study, and shutting off unnecessary heating zones could reduce 59565 W/H of the power supply and hazard potential. Finally, the 12″ tube film process machine electrical hazards and damage control measures were analyzed by using FMEA method, and confirmed that the research results were in line with the expected attenuation strategy of ISD. This approach has increased the safety level, but also reduced operating costs, which is an important achievement of this study.

The interaction between the cutting force and induced sub-surface damage in machining of carbon fiber-reinforced plastics

Carbon fiber-reinforced plastics (CFRPs) have the characteristics of non-homogeneity and anisotropy. Damage occurs frequently in machining of CFRPs, and it can seriously influence the performance of work piece. This study builds a finite element model for machining of CFRPs based on the constitutive relation with damage, the Hashin failure criterion, and the damage evolution. The continuous cutting processes of unidirectional CFRPs with various fiber orientations are simulated. Cutting forces and sub-surface damage are determined from simulations. Furthermore, machining experiments on unidirectional-CFRPs are performed. Cutting processes are monitored, and cutting forces are measured. An artificial neural network (ANN) force model is proposed by using the experimental data, and then simulation results of the cutting forces are validated by these of the ANN model. Cutting force increases when the fiber orientation varies from 0° to 135°. Fiber orientation is the critical factor affecting the cutting force and the sub-surface damage. More sub-surface damage occurs in a fiber orientation range of 90–135°. The primary reasons for the induced sub-surface damage include the damage evolution and the crack propagation of matrix caused by the cutting force. In addition, the effects of cutting parameters and tool geometries on the cutting force and the damage are discussed by simulations. The cutting force thus can be reasonably controlled to reduce the damage.

Finite element analysis of surface milling of carbon fiber-reinforced composites

Despite increased applications of carbon fiber-reinforced plastic (CFRP) materials in many industries, such as aerospace, their machining is still a challenge due to their heterogeneity and anisotropic nature. In this research, a finite element model is used to investigate the cutting forces, chip formation mechanism, and machining damage present during the flat end milling of unidirectional CFRP. The material is modeled as an equivalent orthotropic homogeneous material, and Hashin’s theory is used to characterize failure in plane stress conditions. The friction coefficient between the tool and the composite material was assumed to be dependent on the carbon fiber orientation. A comparison of modeling and experimental results indicates that the model successfully predicts the cutting forces. The numerical model predictions of machining damage around the cutting area due to fiber compression damage and matrix cracking and the relation between damage extension and fiber orientation are confirmed through a comparison with SEM images of machined edges and surfaces.

Prediction of critical thrust force for exit-ply delamination during drilling composite laminates: thermo-mechanical analysis

Drilling damage, such as delamination at the hole exit, is known to adversely affect the load carrying capability of a structure resulting in reduced endurance limits and overall reduction in structural integrity. In this context, the present work studies the influence of temperature of machining on the critical thrust force responsible for delamiantion at the hole exit. An analytical model considering thermo-elastic field equations has been established with the aim of predicting the critical thrust force. The validation of this model has been conducted at room temperature via punching tests carried out on carbon fibre epoxy multi-directional composite laminates. Some difference in predictions exists which are mainly attributed to the variability in ply thicknesses due to the manufacturing process. Such an analysis underscores the need to explicitly account for machining temperature effects on machining damage characterisation.

Industry Monitoring Robot using Arduino Uno with Matlab Interface

In industries, measuring the parameters of machines is still a tedious process which is carried out by some human personnel. This paper mainly focuses on the remedial measures made to reduce human interaction with machines by using Industrial monitoring robot. This robot is hanged over the ropes to measure the parameters of machines in aerial mode. During its travel, the robot collects the parameters from the machines and transmits to control room using ZIG-BEE protocol. The control room interface with the robot is designed using MATLAB GUI model. MATLAB GUI interface shows the parameter readings from the robot and plotted in graph. The robot mainly observes temperature, smoke, toxic gases, Light intensity, defect in manufacturing machines, security purposes using cameras. Any abnormal change in the parameters can be viewed in the graph and remedial measures can be made immediately without any delay, this prevents machine damage to a greater extent. This robot is also used to indicate hazardous conditions like fire, leakage of pipes etc. to the control room using buzzers.

Evaluation of machining damage around drilled holes in a CFRP by fiber residual stresses measured using micro-Raman spectroscopy

Evaluation of machining damage around drilled holes in a CFRP by fiber residual stresses measured using micro-Raman spectroscopy

設備の余寿命診断技術

Crack occurs on machine equipment by the unexpected load, finally machine is damaged. In order to prevent machine damage, there is an effective means to assume remaining life assessment by using the crack information that contains the load history information. In this paper, we propose for the remaining life assessment methods by the crack length information, to report a case study to the spindle of the rolling mill.

Machining damage in FRPs: Laser versus conventional drilling

Comparison of the performance of conventional drilling (CD) and fiber laser machining (FLM) of unidirectional (UD) and multidirectional (MD) glass (G) and carbon (C) fiber reinforced plastics (FRPs) has been presented with an emphasis on machining damage characterization. FLM induced damages are heat affected zone (HAZ), matrix recession, kerf width, and tapered cut whereas CD induced damage include fiber pull-outs, fuzzing, spalling, matrix cracking and delamination. Scanning Acoustic Microscopy (SAM) proved a useful technique to quantify machining damage by providing a ply-by-ply damage analysis. In addition, Scanning Electron Microscopy (SEM) provided detailed views of inherent damage mechanisms during FLM and CD. Machining damage investigation reveals a strong dependence on anisotropy of the composite laminate with greatest matrix recession occurring for UD-CFRP laminates. FLM was found to be efficient with decreased machining times and less set-up requirements. However, surface characteristics of CD specimens were found to be superior to FLM specimens.

Ultra‐High Temperature Mechanical Properties of a Zirconium Diboride–Zirconium Carbide Ceramic

The mechanical properties of a ZrB2‐10 vol% ZrC ceramic were measured up to 2300°C in an argon atmosphere. Dense billets of ZrB2‐9.5 vol% ZrC‐0.1 vol% C were produced by hot‐pressing at 1900°C. The ZrB2 grain size was 4.9 μm and ZrC cluster size was 1.8 μm. Flexure strength was 695 MPa at ambient, decreasing to 300 MPa at 1600°C, increasing to 345 MPa at 1800°C and 2000°C, and then decreasing to 290 MPa at 2200°C and 2300°C. Fracture toughness was 4.8 MPa·m½ at room temperature, decreasing to 3.4 MPa·m½ at 1400°C, increasing to 4.5 MPa·m½ at 1800°C, and decreasing to 3.6 MPa·m½ at 2300°C. Elastic modulus calculated from the crosshead displacement was estimated to be 505 GPa at ambient, relatively unchanging to 1200°C, then decreasing linearly to 385 GPa at 1600°C, more slowly to 345 GPa at 2000°C, and then more rapidly to 260 GPa at 2300°C. Surface flaws resulting from machining damage were the critical flaw up to 1400°C. Above 1400°C, plasticity reduced the stress at the crack tip and the surface flaws experienced subcritical crack growth. Above 2000°C, microvoid coalescence ahead of the crack tip caused failure.

An Investigation of Cutting Mechanisms and Strain Fields during Orthogonal Cutting in CFRPs

Fiber-reinforced plastics (FRPs) are typically difficult to machine due to their highly heterogeneous and anisotropic nature and the presence of two phases (fiber and matrix) with vastly different strengths and stiffnesses. Typical machining damage mechanisms in FRPs include series of brittle fractures (especially for thermosets) due to shearing and cracking of matrix material, fiber pull-outs, burring, fuzzing, fiber-matrix debonding, etc. With the aim of understanding the influence of the pronounced heterogeneity and anisotropy observed in FRPs, “Idealized” Carbon FRP (I-CFRP) plates were prepared using epoxy resin with embedded equispaced tows of carbon fibers. Orthogonal cutting of these I-CFRPs was carried out, and the chip formation characteristics, cutting force signals and strain distributions obtained during machining were analyzed using the Digital Image Correlation (DIC) technique. In addition, the same procedure was repeated on Uni-Directional CFRPs (UD-CFRPs). Chip formation mechanisms in FRPs were found to depend on the depth of cut and fiber orientation with pure epoxy showing a pronounced “size effect.” Experimental results indicate that in-situ full field strain measurements from DIC coupled with force measurements using dynamometry provide an adequate measure of anisotropy and heterogeneity during orthogonal cutting.