bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Heat Treatment on Impact Toughness of Selective Laser Melted Stainless Steel Parts
Authors: Sarkar Sagar , Dubey Soumya , Nath Ashish Kumar
Published: September 2018

One of the versatile additive manufacturing processes is laser based Selective Laser Melting (SLM) which allows to build complex intricate shapes directly from its three dimensional digital images. Layer by layer deposition and depending upon build orientations, SLM parts tends to be anisotropic in nature. Also non-uniformity in thermal loading across the part leads to inhomogeneous microstructure which may have detrimental effect on various mechanical properties. Heat treatment of as-built SLM parts could be used as a post processing technique to reduce the anisotropy and produce homogenous microstructure to ensure reproducible mechanical properties. Application oriented mechanical properties can be obtained for precipitation hardened stainless steel by suitable heat treatment process. Present study is based on effect of heat treatments namely solution annealing, ageing and overaging on impact toughness of SLM 15-5 PH stainless steel. In order to support experimental observations, various metallurgical techniques have been applied. Effect of notch orientations causes anisotropy in impact toughness but this anisotropy is reduced with application of suitable heat treatment. In case of ageing, Transmission Electron Microscopy (TEM) analysis shows formation of fine spherical Cu precipitates which solution strengthens but makes the specimen brittle. As a result relatively lower impact toughness is obtained as compared to overaged condition where combined effect of coarsening of Cu precipitates and increased retained austenite makes the specimen ductile. Increased ageing temperature and soaking time does not have significant effect on impact toughness. However, solution annealing before ageing is recommended for homogenous precipitation throughout the specimen and statistically less scattered data. In all the cases SLM specimens have lower impact toughness to that of cold rolled 15-5 PH stainless steel. Present study could be used as a guideline to get application oriented mechanical properties mainly impact toughness.
Influence of Heat Input on Mechanical Properties and Microstructure of Laser Welded Dissimilar Galvanized Steel-Aluminum Joints
Authors: Yuce Celalettin , Karpat Fatih , Yavuz Nurettin
Published: September 2018

The hybrid structures of aluminum-steel have been increasingly used for body-in-white constructions in order to reduce weight and green gas emissions. Obtaining acceptable joints between steel and aluminum required a better understanding of welding metallurgy and their effects on the resultant mechanical properties as well as the microstructure of the joints. In this research, the fiber laser welding of zero-gap galvanized steel and aluminum alloy in an overlapped configuration was carried out. The influence of heat input on the weld bead dimension, microstructural and mechanical properties of the joints was studied. A detailed study was conducted on the effects of the heat input on the penetration depth, weld width and microstructure of the laser welded dissimilar joints by means of an optical microscopy. A scanning electron microscopy with energy dispersive spectroscopy was carried out to determine the atomic percent of the elements for intermetallic compounds (IMC) occurred at the interface of the aluminum and steel. Microhardness measurement and tensile shear tests were conducted to evaluate the mechanical properties of the galvanized steel to aluminum lap joints. The experimental results showed that the penetration depth and weld width increased with the increase of heat input level. However, in order to limit IMC layer thickness and hardness at the surface of the weld seam and aluminum alloy, iron to aluminum dilution should be restricted by limiting the penetration depth. At lower heat input levels, less brittle IMC formation was formed. Consequently, with limited penetration depths at low heat input levels, up to 520 N tensile shear load achieved, with failures located in the interface of the joints.
A Study on Effect of Different Process Parameters on the Quality of Overhang Surface Produced by Selective Laser Melting
Authors: Sarkar Sagar , Porwal Ankit , Yaswanth Nuthalapati , Nath Ashish Kumar
Published: September 2018

Selective Laser Melting process enables production of geometrically complex parts directly from CAD model by melting metal powders layer by layer. For successful building of parts, some auxiliary structures namely support structures are also built to ensure proper heat conduction from actual parts to be built to the base plate. Support structures are needed if there are overhang surfaces in the design of the part. If the design of the part is very complex and features many overhang surfaces, then too many supports get generated. After building the part, these support structures need to be removed properly to get desired geometrical features and it may deteriorate the surface quality from where supports are removed. Sometimes removal of support structures becomes very difficult specially for parts having internal features. In this study, first effect of inclined angle, aspect ratio and different scanning strategies on the quality of overhang surfaces produced without any support structure under constant laser power and scan speed has been investigated. Scanning Electron Microscopy (SEM) images of overhang surfaces have been analyzed to investigate the presence of warping and uneven fused edges if any. It was found that with increase in inclined angles and aspect ratio, warping and presence of uneven fused edges increases. Rotational scanning strategy found to be better than linear alternate scanning strategy for reduced uneven fused edges formation and warping. Results show an overhang without any support structure can be built successfully with a single laser process parameters upto 25.343 degree which is less than theoretical critical angle of 26.565 degree. Further, it has been shown, using a novel strategy of building overhang with multiple laser process parameters, it is possible to build overhang even upto 24.132 degree.
Edge Profiling of Titanium Alloys and Attainable Surface Quality
Authors: Kannan Sathish , Kui Liu , Pervaiz Salman , Shantha Kumar Vincent , Karthikeyan Ram
Published: September 2018

Machining operations such as reaming, boring or milling create undesirable extruded sharp edges at the entry and exit side of the machined holes. These sharp burrs / extruded edges act as stress concentration regions for fatigue crack propagation in safety critical aerospace components. In this paper, results of an experimental investigation carried out on surface integrity of titanium based alloy during mechanized edge profiling process are presented. In the Mechanized Edge Profiling (MEP) process the primary sharp edges created as result of hole machining are removed using a hard point countersink tool and the secondary sharp edges produced due to countersinking/chamfering the hole entry and exit side edges are radiused using nylon impregnated silicon carbide brushes. On-machine edge profiling experiments were conducted using compliant Flexhone™ and Novoflex™ globular abrasive brushes on highly stressed bolt/flange holes. Brushing speed and feed rate were identified as key process variables. Nylon impregnated with silicon carbide 320 grit brush showed good performance when brushing at a speed of 5000rpm and 5000mm/min feed rate which produced a very consistent and controlled secondary edge radius of 0.3±0.2mm up to 30 holes. An acceptable surface roughness (Ra) of less than 0.5μm on the chamfer and bore surfaces were achieved.
Effects of Process Parameters on Crack Inhibition and Mechanical Interlocking in Friction Self-Piercing Riveting Aluminum Alloy and Magnesium Alloy
Authors: Ma YunWu , He GuanZhong , Lou Ming , Li YongBing , Lin ZhongQin
Published: September 2018

Friction self-piercing riveting (F-SPR) process has been proposed to join low ductility lightweight materials, and has shown advantages over fusion welding, solid state welding and traditional mechanical joining processes in joining dissimilar as well as low ductility materials. Because of the thermo-mechanical nature of F-SPR process, the formation of the joint is determined by riveting force and softening degree of the materials. However, it is still not clear that how exactly the riveting force and generated frictional heat jointly influence the mechanical interlocking formation and inhibit cracks during F-SPR process. To address these issues, in current study, F-SPR process was applied to join 2.2 mm-thick AA6061-T6 aluminum alloy to 2.0 mm-thick AZ31B magnesium alloy. The correlation of riveting force, torque responses as well as energy input with joint quality were investigated systematically under a wide range of process parameter combinations. It was found that a relatively greater final peak force and higher energy input were favorable to produce sound joints. Based on that, a two-stage method was proposed to better control the energy input and riveting force. It was found that the joints produced by the two-stage method exhibited significantly improved lap-shear strength, i.e., 70% higher than traditional SPR joints and 30% higher than one-stage F-SPR joints. This research provides a valuable reference for further understanding the F-SPR joint formation and process optimization.
Analysis of Production System Real-Time Dynamics and Downtime Transient Impact on System Future Production
Authors: Zou Jing , Arinez Jorge , Chang Qing , Ou Xinyan
Published: September 2018

Downtime has been considered as the most significant contributor to system inefficiency in manufacturing industry. During a downtime, the stoppage at the downtime machine will lead to impact on system production. In addition, it will also change system buffer levels, and thus alter system future behavior, which may lead to impact on system production in future time. For each downtime, a complete evaluation of its production impact during and after the downtime is important for deciding where to allocate limited resources for improving system production. However, the evaluation of downtime impact on system future production has not been studied. Motivated by this need, we investigate how each downtime would change the buffer levels and impact system production in the future. The concept of downtime settling time is proposed to reflect such impact. Given the downtime list, an analytical method is developed to estimate this impact of each downtime. Case studies are conducted to demonstrate the accuracy and effectiveness of the proposed methods.
Modeling of Tool-Workpiece Interaction in a Voxelized Framework
Authors: Miers John C. , Tucker Tommy , Kurfess Thomas , Saldana Christopher
Published: September 2018

In the present study, a voxel based model for the interaction between cutting teeth of an arbitrary end mill geometry and a workpiece is presented. In this framework, the workpiece geometry is modeled using a voxelized representation that is dynamically updated as material is locally removed by each tooth of the cutting tool. A ray casting approach is used to mimic the process of the rake face of a tool moving through the workpiece material and to calculate the undeformed chip thickness and its variation in time. The resulting voxel based model framework was validated by comparison of predictions with experimentally measured milling forces. The results demonstrate the model’s ability to accurately simulate the interaction of cutting teeth with the bulk material of the workpiece. Implications of this new voxel based model framework are briefly discussed in terms of utility for predicting local surface finish and computational scalability of complex cutting configurations.
In-Process Monitoring of Material Cross-Contamination in Laser Powder Bed Fusion
Authors: Montazeri Mohammad , Yavari Reza , Rao Prahalada , Boulware Paul
Published: September 2018

The goal of this work is to detect the onset of material cross-contamination in laser powder bed fusion (L-PBF) additive manufacturing (AM) process using data from in-situ sensors. Material cross-contamination refers to trace foreign materials that may be introduced in the powder feedstock used in the process due to reasons, such as poor cleaning of the AM machine after previous builds, or inadequate quality control during production and storage of the feedstock powder material. Material cross-contamination may lead to deleterious changes in the microstructure of the AM part and consequently affect its functional properties. Accordingly, the objective of this work is to develop and apply a spectral graph theoretic approach to detect the occurrence of material cross-contamination in real-time during the build using in-process sensor signatures, such as those acquired from a photodetector. To realize this objective Inconel alloy 625 test parts were made on a custom-built L-PBF apparatus integrated with multiple sensors, including a photodetector (300 nm to 1100 nm). During the process the powder bed was contaminated with two types of foreign materials, namely, tungsten and aluminum powders under varying degrees of severity. Offline X-ray Computed Tomography (XCT) and metallurgical analyses indicated that contaminant particles may cascade to over eight subsequent layers of the build, and enter up to three previously deposited layers. This research takes the first-step towards detecting cross-contamination in AM by tracking the process signatures from the photodetector sensor hatch-by-hatch invoking spectral graph transform coefficients. These coefficients are subsequently traced on a Hoteling T2 statistical control chart. Using this approach, instances of Type II statistical error in detecting the onset of material cross-contamination was 5% in the case of aluminum, in contrast, traditional stochastic time series modeling approaches, e.g., ARMA had corresponding error exceeding 15%.
Numerical Investigation of the Damage Evolution in Vibration Assisted Nano Impact Machining by Loose Abrasives With Different Operating Parameters
Authors: Duong Nick H. , Ma J. , Lei Shuting
Published: September 2018

In this paper, the commercial FEM software package Abaqus is employed to model a novel nanomachining process, in which an atomic force microscope (AFM) is used as a platform and the nano abrasives injected in slurry between the workpiece and the vibrating AFM probe impact the workpiece and result in nanoscale material removal. Diamond particles are used as loose abrasives. The ductile material model is used to describe the behavior of the silicon workpiece. The effects of impact speed, impact angle, and the frictional coefficient between the workpiece and abrasives on material removal mechanism are investigated. It is found that the impact speed, impact angle, and frictional coefficient between the silicon workpiece and nanoabrasives have big influence on material removal volume in this novel nanomachining process.
Study on Improving Accuracy in Robotic Milling of Aluminum Alloy
Authors: Sui Shaochun , Guo Kai , Sun Jie , Zang Yiran
Published: September 2018

Nowadays, the application of using industrial robots in manufacture is a diminutive due to its own low rigidity and low stiffness. This leads to high level of vibrations that limits the quality and the precision of the workpiece. So they are usually used for welding, grinding and paint shop. However, the potential of industrial robot applications in machining has be realized. The volume of monolithic components is large and there are many issues in machining process such as geometric tolerance and quality of machined surface. In such cases the traditional CNC machine is replaced by industrial robots, which will reduce the production cost, reduce labor and increase the efficiency. In this paper, the milling experiment of 7050-T7451 aeronautical aluminum alloy was carried out by using industrial robot KR210 R2700. In addition, the experiment was employed to study the influence of milling speed, feed-rate, cutting depth and cutting width on vibrations, surface roughness was also measured to evaluate the machining quality. Besides, the axis of angle was changed which led to the different industrial robot’s postures. The vibration signal of different postures was acquired, which was used to analysis the optimal workspace of industrial robot. The best process parameters were obtained, which will play a guiding significance on the actual production.
Development of a Multi-Step Exposure Method for Projection-Based Printing System
Authors: Xue Dai , Wang Yancheng , Mei Deqing , Wang Yue
Published: September 2018

Projection-based printing has been proven to be an effective way to fabricate user defined complex structures in biomedical applications. Large-scale printing of this process remains a challenge due to the lack of light source with large irradiation area and long transmitting distances. This paper presents a novel method by using multi-step exposure for large-scale parts printing in projection-based printing system. The multi-step exposure method takes the advantage of using a serial of digital masks for exposure incrementally, thus can compensate the printing differences induced by unevenly distributed ultraviolet (UV) intensity. The system setup and printing characterization of the projection-based printing system are studied. The distribution of the UV light power density is measured and the relationship between the printed height and printing parameters are investigated. Then, a multi-step exposure method is proposed and followed by experimental validation. Results showed that the developed printing system with five-step exposure can be used for a relatively large-scale parts printing, and a relatively flat profile can be achieved. Thus, this method provides the potential ability to print large-scale objects for biomedical applications.
Dieless Water Jet Incremental Micro-Forming
Authors: Shi Yi , Cao Jian , Ehmann Kornel F.
Published: September 2018

Compared to the conventional single-point incremental forming (SPIF) processes, water jet incremental micro-forming (WJIMF) utilizes a high-speed and high-pressure water jet as a tool instead of a rigid round-tipped tool to fabricate thin shell micro objects. Thin foils were incrementally formed with micro-scale water jets on a specially designed testbed. In this paper, the effects on the water jet incremental micro-forming process with respect to several key process parameters, including water jet pressure, relative water jet diameter, sheet thickness, and feed rate, were experimentally studied using stainless steel foils. Experimental results indicate that feature geometry, especially depth, can be controlled by adjusting the processes parameters. The presented results and conclusions provide a foundation for future modeling work and the selection of process parameters to achieve high quality thin shell micro products.
Numerical Investigation of the Slot Up Milling of Ti-6Al-4V
Authors: Chen Xingbang , Khatri Ashutosh , Ma J. , Jahan Muhammad P.
Published: September 2018

In this paper, numerical investigation of the effects of cutting conditions in slot up milling of Ti-6Al-4V is conducted using Finite Element Method (FEM). Experiments are conducted to validate the FEM models. The validated models are then used to predict the cutting force components when different cutting conditions are applied. It is found that cutting speed, feed rate, and depth of cut have strong influence on cutting force components and tool temperature. This research provides insightful guidance for selecting optimal cutting conditions for slot milling of Ti-6Al-4V.
Sensor Fusion and On-Line Monitoring of Friction Stir Blind Riveting for Lightweight Materials Manufacturing
Authors: Gao Zhe , Guo Weihong , Li Jingjing
Published: September 2018

Friction stir blind riveting (FSBR) is a recently developed manufacturing process for joining dissimilar lightweight materials. The objective of this study is to gain a better understanding of FSBR in joining carbon fiber-reinforced polymer composite and aluminum alloy sheets by developing a sensor fusion and process monitoring method. The proposed method establishes the relationship between the FSBR process and the quality of the joints by integrating feature extraction, feature selection, and classifier fusion. This study investigates the effectiveness of lower rank tensor decomposition methods in extracting features from multi-sensor, high-dimensional, heterogeneous profile data. The extracted features are combined with process parameters, material stack-up sequence, and engineering-driven features such as the peak force to provide rich information about the FSBR process. Sparse group lasso regression is adopted to select the optimal monitoring features. The selected features are fed into weighted classification fusion to estimate the quality of the joints. The fusion method integrates five individual classifiers with optimal weights. The correct classification rates resulted from various feature extraction and selection methods are assessed and compared. The proposed method can also be applied to other manufacturing processes with online sensing capabilities for the purpose of process monitoring and quality prediction.
An Automated System for Design for Manufacturability Analysis for Die-Casting
Authors: Kumar Sunil , Madan Jatinder
Published: September 2018

Design for manufacturing (DFM) is an important concept that helps to incorporate manufacturability considerations at early design stage. Development of automated DFM tools has become important especially when design and manufacturing are being done by different teams often distantly located. An automated system for design for manufacturability analysis for die-cast parts has been presented in this paper. The paper discusses: (i) knowledgebase of DFM guidelines (ii) die casting feature extraction from part CAD model, and (iii) automated system for DFM analysis and model updation of the die-cast part CAD model. The capabilities of the system are demonstrated by applying it on die cast part CAD models. The results have been validated with the industrial experts. The present system works with CAD models having features such as boss, rib, hole and draft, created using feature based modeling.
Investigation of the Electroplastic Effect Through Nominally Equal Energy Deformation
Authors: Ruszkiewicz Brandt J. , Mears Laine
Published: September 2018

To increase the fuel economy of their fleets, automotive OEMs are turning to lightweighting their vehicles through multi-material bodies. This involves forming and joining of materials with high strength to weight ratios such as aluminum and advanced high strength steels. These metals come with the downside of decreased formability and increased springback compared to conventional automotive steels. Electrical augmentation has been shown to decrease springback and increase formability in sheet forming and represents a potential solution to the use of new lightweight metals. Applied electricity is traditionally measured as a current density, however this measure struggles to represent elevated strain rate manufacturing processes. This paper examines other predictors of electrically assisted process performance such as electrical energy and power through comparison of nominally equivalent waveforms. It is found that energy is a better predictor of process performance than current density, but is dependent on the ability to predict process temperature. The leading predictive electrically assisted temperature model is examined in depth through testing of 13 different parameter sets. It is found that the model is unable to predict the correct temperature at a high current density and that the transient stress drop cannot predicted for any of the electrical cases.
Single-Degree-of-Freedom Dynamic Vibration Absorber for Unknown System
Authors: Pandeng Zhang , Zhao Liu , Tianfei Zhang , Yutian Zhu , Changlong Zheng , Weiqiang Chen , Yanbin Lin , Ying Lin , Zhengzhong Zheng
Published: September 2018

Vibration causes problems, and the technology of dynamic vibration absorber is always used to control it. So far, the technology is mature, but based on the known of modes, mass, stiffness, damping and other parameters of the vibration system. For an unknown system or complicated system, how to use this technology is what the paper mainly discusses. The dynamic vibration absorber of this paper is a single-degree-of-freedom, and only one direction is to be controlled. The evaluation function is the ratio between the system vibration response after adding dynamic vibration absorber and the original exciting force, which can reflect the effect of dynamic vibration absorber. After separating the unknown system and the dynamic vibration absorber, based on force analysis, we analyze them separately and deduce the calculating formula of the evaluation function. The order of parameters to be determined is mass, stiffness, and damping. Flow chart is presented on how to use the method. The method is validated by a known system of two degree-of-freedom vibration system. The main innovation of this paper is to propose a method of predicting the effect of adding a single-degree-of-freedom dynamic vibration absorber to an unknown system to control a certain direction. This method doesn’t need to consider the system damping factor. This paper extends the scope of technology application of dynamic vibration absorber.
A Model for Hyper-Elastic Material Behavior Under Thermal Aging With an Application to Natural Rubber
Authors: Korba Ahmed G. , Kumar Abhishek , Barkey Mark E.
Published: September 2018

Numerous hyper-elastic theoretical material models have been proposed over the past 60 years to capture the stress-strain behavior of large deformation incompressible isotropic materials. Among them, however, only few models have considered the thermal aging effect on model parameters. Having a simple, closed-form equation that includes the effect of aging temperature and time in describing the stress-strain behavior could facilitate fatigue analysis and life time prediction of rubber-like materials. In this vein, this paper defines a new and simple Weight Function Based (WFB) model that describes hyper-elastic materials’ behavior as a function of aging time and temperature variations. More than 130 natural rubber specimens were thermally aged in an oven and tested under uni-axial loading to observe their stress-strain behavior at various temperatures and aging times. The temperature ranged from 76.7 °C to 115.5 °C, and the aging time from zero to 600 hours. The proposed WFB model is based on the Yeoh model and basic continuum mechanics assumptions, and it was applied to the tested natural rubber materials. Moreover, it was verified against Treloar’s historic tensile test data for uni-axial tension of vulcanized natural rubber material, and also compared to the Ogden and the Yeoh models. A non-linear least square optimization tool in Matlab was used to determine all hyper-elastic material model parameters and all other fitting purposes. The proposed model has better accuracy in fitting Treloar’s data compared to the Ogden and the Yeoh models using the same fitting tool under the same initial numerical conditions.
Investigating the Effect of Wire Feed Rate and Wire Tension on the Corner and Profile Accuracies During Wire-EDM of Ti-6Al-4V
Authors: Kirwin Roan M. , Mahbub MD Rashef , Jahan Muhammad P.
Published: September 2018

Ti-6Al-4V (grade 5 titanium alloy) is one of the most widely used materials in aerospace applications including turbine blades for aerospace engines. Due to the difficulty of machining titanium alloys using conventional machining processes, wire-electro-discharge machining (wire-EDM) is used extensively for cutting titanium parts with complex geometries and profiles. The objective of this study is to investigate the effect of two important non-electrical parameters in wire-EDM, i.e. wire feed rate and wire tension, on the geometric corner and profile accuracies of the Ti-6Al-4V parts machined by wire EDM. A complex profile was designed for machining in two different thicknesses of titanium alloy using each set of experimental parameters. The complex part includes corners with 45°, 90° and 112.5°, as well as thin wall section for measuring the kerf accuracy. It was found that with the increase of wire tension, the corner accuracies at almost all the angles improved. however, too high wire tension caused inaccuracies by providing larger angles than the target values. The effect of wire tension was dependent on the thickness of the machined part. For thinner workpiece the results of the angles generated barely followed a trend, whereas for thicker part, the measured angles followed an excellent trend. The kerf accuracies were found to improve with the increase of wire tension for thin part, whereas for thick part the results of kerf width accuracies were inconsistent. In case of wire feed rate, it was found that comparatively lower settings of wire feed rates were favorable for machining thinner parts with enhanced corner accuracies. On the other hand, slightly higher wire feed rates provided better corner accuracies for thick part. Besides corner inaccuracy, profile undercuts and deviations from the machining paths were observed for lower wire tensions. Finally, it can be concluded that comparatively lower wire feed rate and higher wire tension provides improved corner and profile accuracies. however, for machining thinner sections using wire-EDM, the trends are not obvious.
A Real-Time Analysis of Condition-Based Maintenance in a Multistage Production System
Authors: Li Yang , Jia Deng
Published: September 2018

Condition-based maintenance (CBM) is important to improve production system performance because it is capable to effectively prevent costly equipment failures. However, CBM usually has to stop machines for maintenance during operation and this may severely impede the normal production. This paper establishes a real-time CBM decision making method to minimize the negative impact of CBM stoppage events in a multistage manufacturing system. The method utilizes an event-based analysis method to estimate the permanent production loss resulted from a CBM event. An online control algorithm is introduced to effectively explore the optimal CBM control options. Simulation case studies are performed to validate the event-based CBM decision making method.
Tool Wear of Superhard Ceramic Coated Tools in Drilling of CFRP
Authors: Swan Samuel , Jones Jacob , Kim Dae-wook , Nguyen Dinh , Kwon Patrick
Published: September 2018

This paper aims to investigate the effectiveness of super-hard ceramic coatings by evaluating tool wear when drilling carbon fiber reinforced plastics (CFRP) composite. The drilling experiments of CFRP are conducted with diamond-like coating (DLC) coated, AlMgB14 (BAM) coated, AlCrSiN coated, and uncoated tungsten carbide drills. Tool wear evolution is measured qualitatively as well as quantitatively using the scanning electron and confocal laser scanning microscopes. Both DLC and BAM coatings failed when drilling CFRP only within 10 holes while AlCrSiN coating did not fail. Failure mechanisms of each coating when drilling CFRP are discussed.
Enhancement of Motion Accuracy for Cone-Frustum Cutting Motion by Modified NC Program
Authors: Morishita Kiichi , Sato Ryuta , Shirase Keiichi , Nishida Isamu
Published: September 2018

Motion accuracy of NC machine tools is directory copied onto the machined shape. However, it is known that the motion accuracy is deteriorated by several error courses; geometric and dynamic motion errors of feed axes. In this study, in order to enhance the motion accuracy of NC machine tools, a method that modifies the NC program based on the normal direction error at each command point on the designed path is developed. In the method, the error vector between the commanded and estimated machined shape is obtained. The NC program for the motion is modified by adding the obtained error vector with the opposite sign. In order to confirm the effectiveness of the proposed method, 5-axis motion tests for cone-frustum cutting which is widely applied to the accuracy evaluation of 5-axis machining centers are carried out. At the first, it is confirmed that the proposed method can compensate the dynamic synchronous errors based on the feedback positions and angles of the axes. In addition, it is also confirmed that the proposed method can compensate both of dynamic and geometric errors based on the tool center point trajectory measured by a ball-bar system. As the results, it is clarified that the proposed method can effectively enhance the motion accuracy of the 5-axis machining center.
3D Additive Manufacturing and Micro-Assembly for Transfection of 3D-Cultured Cells and Tissues
Authors: Zhu Qingfu , Zhu Ziyu , He Mei
Published: September 2018

3D additive manufacturing, namely 3D printing, has been increasingly needed in the fabrication of biological materials and devices. Compared to traditional fabrication, direct 3D digital transformation simplifies the manufacturing process and enhances capability in geometric fabrication. In this paper, we demonstrated a rapid and low-cost 3D printing approach for “lego” assembly of micro-structured parts as an electro-transfection device. Electro-transfection is an essential equipment for engineering and regulating cell biological functions. Nevertheless, existing platforms are mainly employed to monolayer cell suspensions in vitro, which showed more failures for translating into tissues and in vivo systems constituted by 3D cells. The knowledge regarding the three-dimensional electric transport and distribution in a tissue microenvironment is lacking. In order to bridge the gap, we assembled PDMS parts molded from 3D-printed molds as the 3D-cell culture chamber, which connects arrays of perfusion channels and electrodes. Such design allows spatial and temporal control of electric field uniformly across a large volume of 3D cells (105∼106 cells). Most importantly, multi-dimensional electric frequency scanning creates local oscillation, which can enhance mass transport and electroporation for improving transfection efficiency. The COMSOL electrostatic simulation was employed for proof of concept of 3D electric field distribution and transport in this “lego” assembled electro-transfection device, which builds the foundation for engineering 3D-cultured cells and tissues.
Experimental Study of Machining of Shape Memory Alloys Using Dry Micro Electrical Discharge Machining Process
Authors: James Sagil , Kakadiya Sharadkumar
Published: September 2018

Shape Memory Alloys are smart materials that tend to remember and return to its original shape when subjected to deformation. These materials find numerous applications in robotics, automotive and biomedical industries. Micromachining of SMAs is often a considerable challenge using conventional machining processes. Micro-Electrical Discharge Machining is a combination of thermal and electrical processes, which can machine any electrically conductive material at micron scale independent of its hardness. It employs dielectric medium such as hydrocarbon oils, deionized water, and kerosene. Using liquid dielectrics has adverse effects on the machined surface causing cracking, white layer deposition, and irregular surface finish. These limitations can be minimized by using a dry dielectric medium such as air or nitrogen gas. This research involves the experimental study of micromachining of Shape Memory Alloys using dry Micro-Electrical Discharge Machining process. The study considers the effect of critical process parameters including discharge voltage and discharge current on the material removal rate and the tool wear rate. A comparison study is performed between the Micro-Electrical Discharge Machining process with using the liquid as well as air as the dielectric medium. In this study, microcavities are successfully machined on shape memory alloys using dry Micro-Electrical Discharge Machining process. The study found that the dry Micro-Electrical Discharge Machining produces a comparatively better surface finish, has lower tool wear and lesser material removal rate compared to the process using the liquid as the dielectric medium. The results of this research could extend the industrial applications of Micro Electrical Discharge Machining processes.
Multi-Scale Characterization of Deformation in Aluminum
Authors: Güler Baran , Efe Mert
Published: September 2018

Materials with deformation behavior sensitive to their microstructure may need deformation analysis at multiple scales to establish the relationship between the microstructure and response to deformation processing. In this work, we use in-plane biaxial test (cruciform) to measure the macro- and microstructure-scale mechanical behavior of a 6061-T6 aluminum alloy at various strain paths. We report flow curves, forming and fracture limits as examples to the macromechanical behavior. As an alternative to the tensile test, it is possible to plot flow curves up to larger strains with the cruciform test. Samples also deform uniformly during the cruciform test and do not develop instabilities in the form of local necks. This allows accurate measurements of forming, and especially fracture limits, under a preset and constant strain ratio. The micromechanical behavior, on the other hand, is quite heterogeneous and microstructure sensitive. Strain localizations at the microstructure scale cause large deviations from the global deformation strains and control the ultimate sample failure at the global scale.
Repeatability Assessment and Sensitivity Analysis of Needle Insertion Physical Experiment
Authors: Li Murong , Lei Yong
Published: September 2018

Needle insertion physical experiments are used as the ground truth for model validation and parameter estimation by measuring the needle defection and tissue deformation during the needle-tissue interactions. Hence parameter uncertainties can contribute experiment errors. To improve the repeatability and accuracy of such experiments, one-at-a-time (OAT) sensitivity analysis is used to study the impacts of the factors, such as stirring temperature, frozen time, thawing time during the process of making hydrogels as well as repeated path insertion and different puncture plane in the planer needle insertion experiments. The results show that the puncture plane has the greatest effect on the repeatability of needle insertion physic experiments, followed by repeated path insertion, while other factors have the least effect. The results serve to guide future experiment design for greater repeatability and accuracy.
Effect of Welding Parameters on Temperature Distribution During Friction Stir Spot Welding of Commercial Pure Copper Lap Joint
Authors: Mahgoub Ahmed , Bazoune Abdelaziz , Al-Badour Fadi , Merah Necar , Shuaib Abdelrahman
Published: September 2018

In this paper, a Coupled Eulerian Lagrangian (CEL) finite element model (FEM) was developed to simulate the friction stir spot welding (FSSW) of commercial pure copper. Through simulations results, the paper presents and discusses the effect of FSSW process parameters; namely rotational speed, plunging rate and dwell time, on the developed temperatures and their distribution within the workpiece as well as material flow and deformation. Model validation showed a good agreement between predicted temperature history and the experiment one, with a maximum error of 6%. Furthermore, the predicted formation of flash was also found in good agreement with the experiment with an error of only 7%. Simulation results predicted peak temperature and plastic strain among all studied welding conditions were 920 K and 3.5 respectively at 1200 rpm rotational speed, 20 mm/min plunging rate and 4 seconds dwell time, which is approximately 70% of the melting point of pure copper.
Failure Analysis and Quality Assessment of 3D Printed ABS Parts
Authors: Seif Mohamed
Published: September 2018

The work aims to study the performance of 3D-printed parts under In-Plane and Out-of-Plane shear stresses. The test articles are made from Acrylonitrile Butadiene Styrene (ABS) by the 3D printing process (Fused Deposition Modeling - FDM). The testing procedures have been performed according to the ASTM D3846–02 method for defining the In-Plane shear strength while the ASTM D5379 method has been used for determining the Out-of-Plane shear properties. The statistical distribution functions were determined for both test data. Failure analysis has been performed for determining the Probability Density Function, the Survival Function, and the Hazard Function. The probability of failure at a certain stress level has been determined. A comparison between parts manufactured using the 3D printer and the commercially manufacturing process has been performed using the nonparametric two-sample Kolmogorov-Smirnov normality test of the underlying distributions and also supported by Mann-Whitney test.
A Study on Laser Welding of Titanium and Stainless Steel
Authors: Chattopadhyay Angshuman , Muvvala Gopinath , Racherla Vikranth , Nath Ashish Kumar
Published: September 2018

Joining of dissimilar metals and alloys has been envisioned since a long time with specific high end applications in various fields. One such combination is austenitic stainless steel grade SS304 and commercial grade titanium, which is very difficult to join under conventional fusion process due to extensive cracking and failure caused by mismatch in structural and thermal properties as well as formation of the extremely brittle and hard intermetallic compounds. One of the methods proposed in literature to control the formation of intermetallics is by fast cooling fusion process like laser beam welding. The present study has been done on laser welding of titanium and stainless steel AISI 304 to understand the interaction of these materials during laser welding at different laser power and welding speed which could yield different cooling rates. Two types of cracks were observed in the weld joint, namely longitudinal cracks and transverse cracks with respect to the weld direction. Longitudinal cracks could be completely eliminated at faster welding speeds, but transverse cracks were found little influenced by the welding speed. The thermal history, i.e. melt pool lifetime and cooling rate of the molten pool during laser welding was monitored and a relation between thermo-cycle with occurrence of cracks was established. It is inferred that the longitudinal cracks are mainly due to the formation of various brittle intermetallic phases of Fe and Ti, which could be minimized by providing relatively less melt pool lifetime at high welding speeds. The reason of the transverse cracks could be the generation of longitudinal stress in weld joint due to the large difference in the thermal expansion coefficient of steel and titanium. In order to mitigate the longitudinal stress laser welding was carried out with a novel experimental arrangement which ensured different cooling rates of these two metals during laser welding. With this the tendency of transverse cracks also could be minimized significantly.
Performance Evaluation of Minimum Quantity Lubrication With Exfoliated Graphite Nanoplatelets in Turning Titanium Alloy
Authors: Nguyen Dinh , Lee Pil-Ho , Guo Yang , Kwon Patrick , Park Kyung-Hee
Published: September 2018

This paper evaluates the performances of dry, minimum quantity lubrication (MQL) and MQL with nanofluid in turning the most common titanium (Ti) alloy, Ti-6Al-4V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable oil (rapeseed) mixed with small concentrations of exfoliated graphite nanoplatelets (xGnP). The focus of this paper is on turning process because it poses a challenging condition to apply oil droplets directly onto the tribological surfaces of a cutting tool due to the continuous engagement of tool and work material. A series of turning experiments was conducted with uncoated carbide inserts while measuring the cutting forces with the dynamometer under various conditions to determine its effectiveness and optimal MQL condition in turning. The worn inserts are retrieved to measure flank and crater wear using confocal microscopy. This preliminary experimental result shows that the use of MQL and nanofluid is effective in improving the machinability of Ti alloys in turning processes.
Monitoring, Diagnostics, and Prognostics for Robot Tool Center Accuracy Degradation
Authors: Qiao Guixiu , Weiss Brian A.
Published: September 2018

Over time, robots degrade because of age and wear, leading to decreased reliability and increasing potential for faults and failures; this negatively impacts robot availability. Economic factors motivate facilities and factories to improve maintenance operations to monitor robot degradation and detect faults and failures, especially to eliminate unexpected shutdowns. Since robot systems are complex, with sub-systems and components, it is challenging to determine these constituent elements’ specific influence on the overall system performance. The development of monitoring, diagnostic, and prognostic technologies (collectively known as Prognostics and Health Management (PHM)), can aid manufacturers in maintaining the performance of robot systems by providing intelligence to enhance maintenance and control strategies. This paper presents the strategy of integrating top level and component level PHM to detect robot performance degradation (including robot tool center accuracy degradation), supported by the development of a four-layer sensing and analysis structure. The top level PHM can quickly detect robot tool center accuracy degradation through advanced sensing and test methods developed at the National Institute of Standards and Technology (NIST). The component level PHM supports deep data analysis for root cause diagnostics and prognostics. A reference data set is collected and analyzed using the integration of top level PHM and component level PHM to understand the influence of temperature, speed, and payload on robot’s accuracy degradation.
Comparison of Two Damage Models for Prediction of Failure in Stress Corrosion Cracking
Authors: Singhal Sorabh , Jasra Yogeshwar , Saxena Ravindra K.
Published: September 2018

In the present work, Stress corrosion cracking (SCC) and its mechanical behavior are presented. SCC represents complex behavior due to electrochemical and mechanical interaction. Damage models are proposed to predict crack initiation time for stainless steel under constant load using the concept of continuum damage mechanics to show incremental damage accumulation which finally leads to failure of the material. Two damage models applicable to prediction of damage in SCC, Lemaitre damage model and damage driving force model proposed by Kamaya are compared. The comparative study of the results obtained by these damage models shows that in Lemaitre damage law cracks initiate randomly while in damage driving force model the stress concentration occurs around the periphery of damaged element results in increased damage force. The study can be used to estimate the crack initiation time in SCC under corrosive atmosphere.