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About this book

This book presents the proceedings of the first INCASE conference, organised by ARTC at A*STAR, Singapore. It provides a comprehensive review of recent advances in surface enhancement processes and strategies employed to assess their impact on materials properties and performance. As cyber-physical systems are becoming more and more relevant in manufacturing, it focuses on assessing the readiness of current technologies for future transformations, such as Industry 4.0, identifying the opportunities and challenges, and exploring ways to address them.

Written by researchers, practising engineering and industry experts, the book bridges the gap between research and manufacturing, promoting technology adoption in industry and innovative ideas to prepare it for the future.

Table of Contents

Frontmatter

Fatigue Life Enhancement

Frontmatter

Optimization of Shot Peening for Titanium Alloys Ti 10-2-3 in CONDOR Project

CONDOR is an R&D project lead by IRT-M2P with different industrial partnership to increase knowledge and simulation models of shot peening. This surface hardening process aims to perform different shots with high velocity on metallic surfaces to introduce compressive stresses on it. Fatigue behavior of shot peened parts is significantly improved. During this research project a DOE has been carried out to optimize shot peening parameters on titanium alloys (surface roughness before shot peening, size and shot’s hardness, covering and intensity). The DOE is composed by more than 300 fatigue specimens. All this data allows us to define specifically each shot peening parameter influence on shot penned parts efficiency. CONDOR project allows simulation development of models to simulate shot peening effect by taking into account the parameters introduced above. Those models are used to evaluate residual stress level and fatigue lifetime after shot peening and to confirm models readiness level. This study has defined optimized machining and shot peening conditions in order to increase parts fatigue lifetime.

Corentin Dides, Thomas Billot, Nicolas Guillemot

Mechanical Investigations on Composite Peened Aluminium

Composite peening describes a novel approach based on the micro peening process. By composite peening, particles can be introduced into near-surface regions of metallic base materials. The proportion of the reinforcement phase decreases gradually with increasing distance to the surface. These so-called Functionally Graded Metal Matrix Composites (FGMMC) are characterised by a multitude of different characteristics, such as material combination, particle density, particle gradient and particle size, and a resulting broad range of properties. The composite material produced by this method promises a high application potential for lightweight, wear resistant and cyclically stressed structural components.EN AW–1050 was selected as matrix material and alumina as abrasive respectively reinforcement material. Additional abrasives such as silicon carbide and tungsten carbide were also investigated. By varying the process parameters, such as temperature and pressure, the influence on the particle density and the particle gradient was evaluated. Penetration depths up to 30 µm could be observed at high homologous temperatures. The peening process might cause open structures near the surface, the sample were subsequently deep rolled. In addition, this process reduces the surface roughness.Ensuing mechanical characterisation focused on bending tests. An increase in the flexural strength of the composite material compared to the base material could be observed.

Michael Seitz, Kay André Weidenmann

Influence of Wetblast Treatment on Fatigue Strength of Magnesium Alloy AZ31

From the viewpoint of weight reduction in transportation equipment such as automobiles, the use of light metals is being promoted. Magnesium alloy is the lightest in practical metals, but it has the property that its strength is low. For improvement of fatigue strength, surface modification treatment such as shot peening is generally applied. Since the magnesium alloy has high reactivity with oxygen and may ignite, surface treatment in a dry environment like shot peening is difficult. In this study, we focused on wet blasting process with low probability of ignition and examined the influence of it on fatigue strength. The fatigue strength of wet blasting AZ31 showed higher results than untreated material. As this factor, improvement of hardness near the surface and application of compressive residual stress are conceivable. Also, the particles used in the wet blasting process are smaller than the particles used in the general shot peening process. Therefore, the fact that the surface roughness did not change significantly was also considered to be one factor. From the above results, we clarified that the wet blasting treatment can safely improve the fatigue strength of the magnesium alloy.

Koichiro Nambu, Kenta Takashima, Isao Kumagai, Masahiro Okumiya

Process Model for Evaluating the Peen Velocity in Shot Peening Machine

Peening velocity (shot velocity) is one of the key parameters in shot peening process, which directly relates to intensity and coverage area. A desired intensity and/or coverage area can be attained by controlling the peening velocity to the right value. However, this is a challenging task as the peening velocity is the function of many different variables (peening system, nozzle design, air pressure, media (shot) flow rate, shot size, etc.). In this study, we develop a process model that links the input/operating parameters of the peening machine to the average shot stream velocity upon impact. In particular, the formulation of shot stream velocity is derived as the function of input air pressure and media flow rate, which also accounted for the peening system and nature of the flow inside (e.g., nozzle shape, pressure loss, energy transfer, and turbulence, etc.). The model is validated against the experimental data for different inlet pressure as well as the media flow rates. The calculated results are in good agreement with experimental data. Furthermore, the model validity and reliability are examined for the wide range of input parameters and the system parameter. The results also indicated that the developed process model can be applied for different peening machines with different nozzle design by defining relevant model constants. There are a few key applications for the process model; which are (1) the model can support the operators to rapidly estimate and setup the working conditions of the machine to attain the desired peening intensity and coverage area to avoid the cost and time in doing experiments based on trials and errors, and (2) The model also can be used in model predictive control (MPC) to develop the controller for the peening machine.

Nguyen Van Bo, Ba Te, Augustine Teo, Kunal Ahluwalia, Ampara Aramcharoen, Kang Chang Wei

Experimental Study of Single Shot Process: Toward a Surface State Predictive Tool

The present study aims at enhancing the comprehension of the interactions between shot and target during shot-peening process, with focus on the energy transmitted and roughness generation. A single impact approach was developed in order to establish relations between the process parameters, media and target properties, and the generated surface state. Al-6061-T6 plates were peened with only one shot made of different materials (ceramic, metals) under controlled process conditions (pressure, distance and angle). Process parameters such as incident and rebound velocities were determined by coupled fast-cam.This approach allows identifying key criteria combining media properties and shot peening process parameters, initial step, to monitor and optimize the surface topography of the peened sample.

Benjamin Levy, El Mansori Mohamed, Sabeur Mezghani, M. El Hadrouz, Julien Cabrero, Anne-Laure Beaudonnet

Microstructural Changes in Electroplated Chromium Coating–Substrate Interfaces Induced by Shot Peening

Shot peening has been widely used for industrial field because of its attractive effects to increase strength of treated material. In addition, microstructural changes induced by shot peening have been recent interest since they possibly promise adding surface functions and enhancing the surface characteristics. In this study, shot peening was conducted on electroplated chromium coatings deposited on carbon steel substrate in order to create mechanically-mixed microstructure which was composed of iron and chromium. Microstructural changes induced by shot peening was carefully analyzed under ranging peening time. Results indicated that shot peening using steel grit particles created specific microstructure where fragments of chromium plating were dispersed into steel matrix whereas shot peening using spherical shot insufficiently induced the microstructural changes. It was implied that fragments of chromium plating were transported from top surface to steel substrate interior and simultaneously pulverized due to continuous impact of the particles during shot peening process. Severe plastic deformation induced at the shot-peened surface played as a driving force to induce material transportation and resulting “composite” microstructure formation.

Yutaka Kameyama, Tatsuya Ohta, Keita Sasaki, Hideaki Sato, Ryokichi Shimpo

Investigation on Theoretical Analysis of Residual Stress Distribution Induced by Shot Peening in 2397 Aluminum-Lithium Alloy

In order to investigate the effect of shot peening (SP) on residual stress distribution, an amendatory theoretical model considering the effects of friction between shots and treated component has been proposed based on Hertz contact theory. The residual stress field induced by shot peening in 2397 Aluminum-Lithium alloy was considered as an example. To verify the theory, the residual stresses field along the depth in 2397 Aluminum-Lithium alloy was measured by means of X-ray diffraction method, accompanied by layer removal technique. The distributions of residual stresses derived from experimental results were in good accordance with theoretical model, while the minor errors still existed among them. The slight errors are mainly ascribed to surface roughness, ideal elastoplastic constitutive model and crystallographic textures. As a result, the theoretical model and corresponding algorithm can be applied to predict residual stresses fields under various shot peening conditions for Aluminum-Lithium alloys and other metallic materials, as well.

Yukui Gao, Xuefei Tao

Effect of Shakedown on the Fatigue Limit of Ultrasonic Shot Peened Steel

We performed in-plane bending fatigue tests under controlled load conditions on ASTM 309 stainless steel specimens with surface compressive residual stress. The results provide a fatigue limit of 415 MPa, which agrees with the value of 404 MPa calculated based on a modified Goodman line considering shakedown. Therefore, the surface layer was clearly restricted by the internal bulk and was relieved under controlled displacement, after which shakedown occurred. Then, the fatigue limit of the metal material with surface compressive residual stress should be estimated by using a modified Goodman line considering shakedown to avoid unexpected fractures that could occur by following a modified Goodman line that does not consider shakedown.

Jinta Arakawa, Yoshiichirou Hayashi, Hiroyuki Akebono, Atsushi Sugeta

Fundamentals and Applications of Cavitation Peening Comparing with Shot Peening and Laser Peening

Although impact induced by cavitation bubble collapse causes severe damage in hydraulic machineries, the impact can be utilized for the mechanical surface treatment of metallic materials in the same way as shot peening. The peening using cavitation impact is named as “cavitation peening”. In the paper, the concepts and key factors on cavitation peening are presented including mechanism of generation of cavitation by using a submerged water jet. The difference between cavitation peening and water jet peening was also demonstrated by measuring peening intensity such as arc height of metallic plate. In order to discuss the difference between improvement of fatigue strength of stainless steel by cavitation peening, water jet peening, shot peening and submerged laser peening, a plane bending fatigue test was carried out. The specimens were treated at various processing time by each peening method, and the optimum processing time at each peening methods was revealed, then the fatigue strength of stainless steel treated at the optimum processing time was evaluated. It was concluded that the fatigue strength at N = 107 of cavitation peening was highest followed by shot peening, submerged laser peening and finally water jet peening.

Hitoshi Soyama

Effect of Mechanical Properties on Fatigue Life Enhancement of Additive Manufactured Titanium Alloy Treated by Various Peening Methods

Additive manufacturing (AM) of metallic materials is attractive processing for biomedical implants and aviation components. However, fatigue life of AM parts are remarkably weak. Mechanical surface treatment such as cavitation peening, shot peening and laser peening can improve the fatigue life of AM parts. In the present paper, in order to demonstrate the fatigue life enhancement of AM parts by various peening methods, titanium alloy Ti6Al4V manufactured by electron beam melting EBM was treated by cavitation peening, shot peening and laser peening, and then tested by a plane bending fatigue test. And also, in order to make clear mechanism on the fatigue life enhancement of AM parts, mechanical properties such as residual stress, yield stress and hardness were evaluated, and the correlation between the mechanical properties and the fatigue life was investigated. Note that the yield stress was evaluated by an inverse analysis using an indentation test. It was concluded that the fatigue life of Ti6Al4V manufactured by EBM was proportional to a parameter defined by residual stress, yield stress, surface roughness and hardness.

Yuya Okura, Hirotoshi Sasaki, Hitoshi Soyama

Influence of Burnishing Process on Microstructure and Corrosion Properties of Mg Alloy AZ31

Magnesium (Mg) alloy is an attractive biodegradable implant material in orthopedic fixation applications. Compared with the permanent metallic implant material, such as titanium alloy and stainless, the Young’s modulus of Mg alloys is close to human bone, and it can be gradually absorbed in the human organism. The problems such as stress shielding and secondary surgery operation can be avoided by using Mg alloy. However, the corrosion speed of Mg alloys is too fast for actual medical application. In order to solve this problem burnishing process, which is a kind of surface finishing process, was tried to improve corrosion resistance of Mg alloys in this research. Burnishing experiments were done using a newly developed ball burnishing tool on annealed Mg-Al-Zn alloy AZ31 plates. In order to determine how the parameters of burnishing process affect the microstructure and corrosion properties, the experiments were designed based on Taguchi orthogonal array L9, in which three parameters (burnishing force, tool path interval, and feed speed) are varied at three different levels. For each processing condition, the microstructure near the surface and thickness of layer affected by burnishing process were evaluated by microscope. The experimental results indicated that after the burnishing process the grain size is refined. In addition, corrosion test was carried out and the mass loss of each sample was evaluated. The result shows that burnishing process is effective to improve the corrosion resistance.

Chenyao Cao, Jiang Zhu, Tomohisa Tanaka

Effects of Machine Hammer Peened Surface Textures on the Tribological Behavior of Stamping Tools

Machine hammer peening (MHP) is a dynamic process to smoothen tool surfaces, increase hardness and introduce residual compressive stresses into the surface layer. Additionally, MHP can be used to apply surface textures that act as lubricant pockets onto tools with specifically shaped hammer heads. These surface textures have proven to minimize friction and decrease wear and tear of sheet metal forming tools. As of now, the wear behavior of these surface textures has not yet been investigated sufficiently in stamping processes.This paper focuses on the application of surface textures by MHP onto stamping tools used for shear cutting operations on a mechanical press. Within the experimental investigations, different textures are applied on the shell area of the stamping tools. During the cutting process, the resulting cutting force is monitored. Based on the force monitoring of the tools the forces are compared after 10000 and 20000 strokes and a correlation analysis between the stroke count as well as wear of the stamping tool, characterized by their functional volumes is conducted.It is shown that MHP induced surface textures are not only capable of reducing wear and tear, but also that the process condition can be monitored by characteristic process values and inline measurements. This allows for an improved tool construction with adapted surface textures and, taking the correlation of the process monitoring data and the wear of the tools into consideration, longer and more plannable maintenance intervals and higher process reliability can be achieved.

Peter Sticht, Johannes Hohmann, Peter Groche

Mechanical Properties Enhancement of Additive Manufactured Ti-6Al-4V by Machine Hammer Peening

Wire + Arc Additive Manufacturing (WAAM) is a technology potentially offering reduction of material wastage, costs and shorter lead-times. It is being considered as a technology that could replace conventional manufacturing processes of Ti-6Al-4V, such as machining from wrought or forged materials. However, WAAM Ti-6Al-4V is characterized by coarse β-grains, which can extend through several deposited layers resulting in strong texture and anisotropy. As a solution, inter-pass cold rolling has been proven to promote grain refinement, texture modification and improvement of material strength by plastically deforming the material between each deposited layer. Nevertheless, with the increased interest in the WAAM technology, the complexity and size of the deposited parts has increased, and its application can be hindered by the low speed and complex/costly equipment required to perform rolling at this scale. Therefore, Machine Hammer Peening (MHP) has been studied as an alternative cold work process. MHP can be used robotically, offering greater flexibility and speed, and it can be applied easily to any large-scale geometry. Similarly to rolling, MHP is applied between each deposited layer with the new ECOROLL peening machine and, consequently, it is possible to eliminate texturing and reduce the β-grains size from centimeters long to approximately 1 to 2 mm. This effect is studied for thin and thick walls and no considerable change in grain size is observed, proving the applicability of MHP to large components. The yield strength and ultimate tensile strength increases to 907 MPa and 993 MPa, respectively, while still having excellent ductility. This grain refinement may also improve fatigue life and induce a decrease in crack propagation rate. In this study, it has been shown that MHP is a suitable process for WAAM Ti-6Al-4V applications, can be applied robotically and the grain refinement induced by very small plastic deformations can increase mechanical properties.

Leonor Neto, Stewart Williams, Jialuo Ding, Jan Hönnige, Filomeno Martina

An Automated Deposition Procedure for Cold Spray Additive Manufacturing Process Modeling Based on Finite Element Simulation

The present paper presents modeling of the Cold Spraying Process using a progressive build-up technique. This technique is based on the modeling features dedicated to the Additive Manufacturing Process. It has the major advantage in saving computational cost while maintaining reasonable numerical accuracy compared to other finite element solutions that involve realistic impact simulations for thousands of particles. The new approach uses the database obtained from one-time finite element simulations performed with the Eulerian scheme by computing the corresponding thermomechanical fields averaged over a gauge length. This is inserted into the progressive build-up model with a pair of subroutines for the definition of initial stresses and equivalent plastic strains. The material addition has been performed in the finite element analysis by progressively activating the elements that take the values of the averaged thermomechanical fields at the moment of activation. To undergo element activation, another pair of subroutines are used to locate the elements that are within a sphere of a fixed radius and belonging to the deposition toolpath or segment. The deposition segments considered in the modeling are an event series presenting the element status with respect to the tool coordinates and time. The deposition input parameters have been specified using a table collection. The progressive build-up procedure has been used to determine the thermomechanical fields such as temperature in the coating and residual stress in the structure.

Sabeur Msolli, Zhi-Qian Zhang, Junyan Guo, Sridhar Narayanaswamy, Reddy Chilla Damodara, Zheng Zhang, Jisheng Pan, Boon Hee Tan, Qizhong Loi

Bonding Strength Improvement Through Numerical Simulation of Particle Impact Process During Metal Cold Spray

Cold spray is an emerging additive manufacturing technique with potential applications in surface functionalization, bulk component production and restoration/repair. During the cold spray process, metallic powders are accelerated to supersonic velocities by the carrier gas of high pressure and temperature and impact on the substrate to form layers of coating through deformation-induced bonding. However, the coating fabricated by this process suffers from low cohesive strength and weak interfacial bonding. Therefore, process optimization through numerical simulation is much needed. Here we employ finite element simulation with Johnson-Cook plasticity and dynamic failure model to numerically predict the temperature distribution within single particle, and they show good agreement with experimental observation using SEM. This provides a validated description of microscopic phenomena using numerical simulation, hence it can be employed further to study the bonding strength of the metal cold spray coating. Through microstructural analysis, we propose a semi-empirical relationship between the nodal temperature profile and local bonding strength, hence identified that the increase of the localized bonding area in a single splat is the determining factor for the increase of the bonding strength.

X. Song, X. Z. Jin, J. Everaerts, W. Y. Tan, W. Sun, I. Marinescu, W. Zhai, F. Li, E. J. Liu, A. M. Korsunsky

Product Verification and Material Characterisation

Frontmatter

Surface Texture Evaluation on Mirror Finish Surface Using Patterned Area Illumination Method

Mirror finish surface products are widely used in many industries such as aerospace, optics, semiconductor and biomedical device manufacturing. The surface texture of mirror finish products is usually measured by off-line instruments such as coherence scanning or phase shifting interferometers. However, most commercial interferometers are expensive and must be operated in a clean and vibration-free laboratory environment. In order to achieve both in-situ surface quality control and automated tool changing for the polishing process, fast and non-contact surface texture measurement are required. To address these in-situ measurement challenges, a surface texture measuring system based on fringe pattern illumination method is proposed in this paper. By analyzing the luminance contrast ratio of the fringe pattern reflection image and comparing to the measurement results from the referenced coherence scanning interferometer, the experimental results showed that the proposed system was able to measure different mirror finish surfaces with Sa and Sq values in the range of 15 nm to 120 nm and 30 nm to 160 nm respectively. In addition, the luminance contrast ratio was also correlated with directions of the machining marks and the projected fringes at different measurement angles. The surface texture aspect ratio parameter Str which provides information about the strength of the machining marks was experimentally evaluated and compared with luminance contrast change. In conclusion, the proposed measuring system was able to measure surface texture with a relative error less than 10% at measurement angle between 20° to 160°, and indicate machining pattern effects on the mirror finish surface.

Shaowei Fu, Fang Cheng, Tegoeh Tjahjowidodo

Sliding Behavior of Secondary Phase SiC Embedded Alloyed Layer Doped Ti6Al4V Surfaces Ensuing Electro Discharge Machining

The enhancement in process efficiency achievable by additive mixed electrical discharge machining during the processing of metal/alloy surfaces is a known facet. Nonetheless, its influence on the surface characteristics of the material remains scarcely evaluated. Hence, the evolution in tribological behavior of electrical discharge machined Ti6Al4V surfaces become the focal point of the present investigation. The process got assisted by silicon carbide powder (SiC, green, 1–10 μm) dispersed dielectric (de-ionized water) used as an insulator and the discharge medium. A computerized pin-on-disk tribometer (PoDT) was used to quantify the wear behavior of the developed surfaces. The experimentations varied based on distinction in the chosen speed (1.256 ms−1 (V1) and 1.884 ms−1 (V2)) and load (50 N and 100 N) conditions, respectively. The results depict that the tribological characteristics of the base material were enhanced by the surface doped heavily alloyed recast layer with secondary hard phases (SiC). At increased load (100 N), a catastrophic shift in wear mechanism caused by galling, led to the resultant delamination. The aftermath situation of implementing hard abrasives for surface modification is that at severe conditions (load/speed), the spalling of layers can have destructive effects on the mating surfaces.

Jibin T. Philip, Deepak Kumar, Jose Mathew, Basil Kuriachen

Measurement of Residual Stresses on Deep Rolled Round Aluminum Samples Using Hole Drilling Strain Gage Method

Deep rolling is an established process to induce plastic deformation on the surface of engineering parts. As a result, a cold worked surface and a compressive layer of residual stresses are generated in subsurface regions. Thus, strength can be increased. Although deep rolling is mostly applied to axisymmetric parts with comparatively low diameters, effect of process parameters on induced stresses are usually investigated on flat surfaces. However, different residual stress profiles are expected in depth direction in flat and cylindrical parts. In the current study, residual stresses induced in deep rolled round EN AW-6082 aluminum samples with a diameter of 14 mm were measured using hole-drilling strain-gage method. Hole drilling calibration matrices were derived using finite element simulations. These matrices were compared with the ones used for flat specimens. Evaluated residual stress profiles by using these matrices were compared for both a flat workpiece and cylindrical workpiece.

Mehmet Okan Görtan, Berkay Yüksel, Bilsay Sümer

Mechanical Stress Relaxation of a Laser Peened and Shot Peened Ni-Based Superalloy

Nickel based superalloy IN718 specimens were subjected to laser peening and shot peening. The residual stress and work hardening introduced by laser peening and shot peening were characterized using neutron diffraction method and electron backscattered diffraction (EBSD). A modified set up in reflective mode was utilized during neutron diffraction to optimize the spatial and temporal resolution to perform in-situ residual stress measurements at pre-determined cycle. Residual stress relaxation was only observed in the direction of loading while the residual stress in the transverse direction remained at a similar magnitude. Residual stress relaxation was observed to be most prominent in the first cycle of fatigue at R ratio = 0.1 with little stress relaxation in subsequent fatigue load cycles. Under tensile-tensile loading, stress relaxation occurs when the superposition of tensile residual stress and applied loading exceeds the localized yield strength of the material. Stress relaxation was found to be well correlated with the magnitude of work hardening. Residual stress relaxation as a function of depth and number of cycles were also recorded to illustrate the changes in residual stress during the cyclic loading.

Kai Siang Chin, Sridhar Idapalapati, Anna Paradowska, Mark Reid, Shashwat Shukla, Dennise Tanoko Ardi

Incorporation of Evaluation Technology into Shot Peening Equipment

Shot peening is one of surface enhance method and is used in the automotive industries and aerospace industries. The compressive residual stress induced by shot peening greatly improves the fatigue strength. Also, it is been important to induce compressive residual stress from the surface to the inside in order to improve the fatigue strength. Therefore, it is important to understand the residual stress distribution of the products. In general, product evaluation in the shot peening process is destructive inspection by sampling.From the viewpoint of quality control, product evaluation of shot peened products should be 100% inspection. Furthermore, it is best to be able to evaluate from the surface to the inside. Therefore, we propose the inspection system for shot peening in production site. We report the features of inspection method in this system and the examination results assuming inspection of production line.

Kan Aoki, Yuji Kobayashi, Yoshiyasu Makino

Influence of the Feed Rate in the Single-Lip Deep Hole Drilling Process on the Surface Integrity of Steel Components

High strength steels like AISI 4140 are commonly used in many technical areas in which the mechanical properties of materials have to meet special requirements, for example, in the case of dynamically loaded parts. In the automotive industry increasing requirements due to lightweight design or energy efficiency lead to increasing demands on the mechanical and dynamic material strength. In response to this development, optimized machining processes are capable of improving the mechanical properties like fatigue performance by influencing the surface integrity of the machined components. In this paper, the influence of the single-lip deep hole drilling process on the surface integrity of quenched and tempered AISI 4140 specimens is analyzed in detail. Under variation of one of the main process parameters, the feed rate, the process output parameters such as cutting forces and the resulting condition of the machined surface and subsurface are determined. In combination with the analysis of the resulting hardness, microstructure and surface conditions of the machined surface, a magnetic Barkhausen noise (MBN) analysis with a custom-built sensor is applied and further developed. With this non-destructive technique, the surface integrity of the bore wall and the fatigue damage over the lifecycle of the part can be analyzed. The correlation of the surface integrity produced by the single-lip deep hole drilling process with the results from the micro-magnetic measurements are used to improve the possibility of predicting a components fatigue performance.

Jan Nickel, Nikolas Baak, Frank Walther, Dirk Biermann

Surface Finishing and Machining

Frontmatter

Improvement of Chipping Phenomena for Crustaceous Materials Rounding by Centrifugal Barrel Finishing

Barrel finishing is a surface finishing treatment method used for various parts. In particular, the centrifugal barrel finishing is used for rounding electronic components made of crustaceous materials such as MLCC, because it is high productivity and small-volume production in great varieties. However, because the finishing method has the highest finishing power among barrel finishing, a chipping occurs at the ridges of MLCC made of crustaceous materials. The chipping causes product defects. In this study, in order to reduce the chipping, we investigated the causes of the chipping by observing the contents’s (Mass) behavior in the finishing tank by using a high-speed camera. From the observation result, we found that the phenomena which the Mass was thrown out and collided against finishing walls in the processing. For this reason, the chipping occurred. In order to prevent from the phenomena, we considered flowing the Mass is always touching some wall surfaces of the tank by changing the angle of the tank rotation axis. Commonly, the angle of the tank rotation axis is θ = 0°. However, the Mass did not be thrown out by changing the angle of θ = 45°. This reason is the Mass always touching some wall surfaces of the tank. As a result of this test, it is possible to reduce chipping’s volume by 80% in comparison with the conventional method.

Hiroki Mizuno, Hiroaki Suesuga

In Situ Measurement of Granular Pressure and Velocity on Component Surfaces in Stream Finishing

Stream finishing, one of the fast mass finishing processes that enables a material removal rate up to 500 μm/h, is a candidate for the post processing method for external surfaces of additively manufactured (AM) components. The problem here is non-uniform material removal (MR), which is probably caused by a conventional method of rotating target components 360o in a stream finishing bowl. Our plan is to control the component orientations and toolpath depending on each geometry. In order to consider the optimized toolpath, MR simulation is a promising tool. This study focuses on in situ measurement of process values around the target components, which are essential for modelling the granular flow. We measured the pressure and velocity on components surfaces using prototyped tools submerged in the stream finishing media. As a result, the measured pressure increased with the submersion depth, and reached 0.05 MPa at a depth of 250 mm. Regarding the contact angle, the pressure reached maximum in the normal direction toward media flow. The media motion on the surface was successfully tracked using a transparent container. The measured velocity reached maximum when the surface is parallel to media flow. Using these acquired pressure and velocity, a simple estimation of MR was conducted using Preston’s law, and agreed with the experimental result. The measured values will enable the calibration and validation of the simulation model, which can be used for the future toolpath prediction.

Sho Itoh, Jeremy Ho, Cary Turangan, Stephen Wan

Development of Rheology and Computational Flow Model for Robotized External Finishing on Additively Manufactured Components

Stream finishing is accepted as one of the post processing operations. It is not only capable of grinding but also offers polishing of additive manufactured components, having advantages of larger material removal rates and controllable toolpath. We have developed a stream finishing model through semi quantitative prediction via computational fluid dynamics (CFD) simulations. The scheme couples the granular flow field with the material removal scheme by solving the granular flow using a continuum-based method. For the rheology, the media viscosity is determined to resolve the flow field so the pressure induced by the media and the material removal rate can be predicted. The model calibration involves developing a tribometer and using it to measure the media pressure for several scenarios based on the rotational speed of the drum (30 rpm), radial distances of the tribometer (100, 250, 400 mm), submerged depths (100, 200, 250 mm) and its glancing angles (0, 15°, 30°, 45°, 60°, 75°, 90°). The work is extended to study the media flow for a simplified square work piece. The results indicate that the particle velocities on the surface of the work piece predicted by simulations are comparable to those of experiments. They show similar patterns and magnitudes for the parameters tested, which demonstrate the capability of the model to correctly predict the granular flow field.

Cary Kenny Turangan, Stephen Wan Yee Ming, Sho Itoh, Jeremy Ho

Effects of Combined Wear Mechanisms in Internal Surface Finishing Using Controlled Hydrodynamic Cavitation Abrasive Finishing Process

Controlled hydrodynamic cavitation abrasive finishing (HCAF) process is presented as a new approach for surface finishing the internal surfaces of mechanical components. A recirculating hydrodynamic apparatus is designed and developed to generate controlled cavitation. Experiments are conducted on the internal channels fabricated using electric discharge machining (EDM). Firstly, the surface wear arising from the combined effects of controlled hydrodynamic cavitation and abrasive particles are investigated at (a) non-cavitating condition without abrasive particle, (b) cavitating condition without abrasive particles (c) abrasion condition without cavitation and (d) combined cavitation and abrasion condition. The effect of various operating conditions on the material removal are discussed. Lastly, the improvements in profile surface roughness (Ra) of the internal channels is characterized using optical profilometer. The results obtained (Ra < 1 µm) clearly shows that the combined effect of controlled cavitation and abrasive particles has a significant effect on the surface roughness reduction of internal surfaces.

Arun Prasanth Nagalingam, Swee Hock Yeo

Surface Integrity Characteristics of NiTiHf High Temperature Shape Memory Alloys

This present study focuses on the surface integrity characteristics of the machined NiTiHf high temperature shape memory alloys. The NiTiHf specimens were machined under dry, minimum quantity lubrication (MQL) and cryogenic cooling at two different cutting speeds. Experimental data on microhardness, latent heat and phase transformation temperature is presented and analyzed to evaluate the surface and subsurface characteristics of the machined NiTiHf specimens. It is found that machining process particularly cryogenic machining alters microhardness, latent heat and phase transformation temperature of Ni-rich NiTiHf alloy. This study demonstrates that cryogenic machining process leads to occurring strain hardened layer on the surface and subsurface of machined workpiece. Phase transformation response including transformation temperature and latent heat for transformation of this affected layer shows significant difference comparing with the bulk of the workpiece. This difference is evidently observed from the cryogenically machined specimens than the specimens machined under dry and MQL conditions.

Yusuf Kaynak, Emre Tascioglu, Othmane Benafan

The Effect of Finish-Milling Operation on Surface Quality and Wear Resistance of Inconel 625 Produced by Selective Laser Melting Additive Manufacturing

Additive Manufacturing (AM) has been recognized as a promising manufacturing technology for the industries including aerospace and biomedical; however, the surface finish requirement for the components used in such industries imposes a severe constraint. Thus, finishing process for any manufacturing operation including additive manufacturing needs to be investigated to provide insights into the finish processing-surface property relationship. In this study, finishing operation in milling process is considered as a post-processing to improve the surface, mechanical and wear properties of the specimens fabricated by selective laser melting (SLM). This study demonstrates that surface and subsurface characteristic such as surface topography, surface roughness, microhardness, and wear resistance is substantially affected from milling parameters. Finish-milling operation with the high feed rate results in 50% reduction in wear rate of the specimen fabricated by SLM process.

Emre Tascioglu, Yusuf Kaynak, Özgur Poyraz, Akın Orhangül, Soner Ören

Toolpath Generation for Robot Filleting

Filleting is a finishing process of rounding off the edge to blunt the sharpness as well as to improve the component’s durability by distributing the stress concentration over a larger area, thus enabling the filleted component to last long. Though the filleting process is widespread in manufacturing industry due to its effectiveness, the operation requires subtle changes in position and orientation of the tool when machining the work-piece which is very difficult to capture ‘algorithmically’ and thus predominantly carried out by skilled manual workers as the generation of the toolpath for the process is a major challenge. In this paper, we propose a novel strategy based on Lissajous curves to generate the required toolpath for filleting. Based on the starting and ending location of the fillet, we conceptualize a Lissajous pattern in 2D space. Through a mathematical relationship between the 2D space and the 3D real-world, a toolpath comprising both position and orientation is determined. Trials on Wooden and Aluminium work coupons using KUKA iiwa R800 robot validate our strategy to obtain the desired geometrical profile.

Srinivasan Lakshminarayanan, Omey Mohan Manyar, Domenico Campolo

Laser Processes

Frontmatter

Effect of Bubble Radius on Ability of Submerged Laser Peening

In submerged laser peening, it has been experimentally clarified that the collapse impact of the bubble which occurs after laser ablation is stronger than the impact of laser ablation itself. Moreover, the experimental results showed the arc height increased in proportion to the cube of the bubble development time with various material. Here, the arc height shows the processing capacity of peening, and the bubble development time is proportional to the bubble radius. Therefore, it was shown that the processing capacity of peening by the bubble collapse increased in proportion to the cube of the bubble radius. In order to clarify the effect of bubble radius on submerged laser peening capacity, the fluid/material two-way coupled numerical analysis of a hemispherical bubble on the wall surface with changing the bubble radius was performed. From the analysis results, the relationship between the bubble radius and the maximum pressure in the fluid and maximum equivalent stress in the material was clarified. If the ratio of internal and external pressure of a bubble was the same, the bubble radius had little effect on the bubble collapse pressure and the maximum equivalent stress in the material. However, the material volume of which the maximum equivalent stress exceeded the threshold of yield stress of the materials increased in proportional to the cube of bubble radius. Therefore, also in the numerical analysis, it was shown that the effect of bubble collapse on materials is proportion to the cube of bubble radius.

Hirotoshi Sasaki, Yuka Iga, Hitoshi Soyama

Crack Retardation of Damage Through Enhanced Crack Closure Effect Induced by Laser Peening

The effect of laser peening (LP) on damage is of great significance to recover the service life of damaged material. However, it is still unclear for the reason behind to introduce this effect by high-dynamic loading of LP. In this study, experiments are conducted to investigate the retardation of pre-crack growth by LP treatment. Pre-cracks fabricated by cyclic loading are introduced on CT specimens of aluminum alloy 2024-T351 to act as initial fatigue crack damage. LP treatment is performed to cover the specimen surface with pre-crack. Fatigue crack propagation (FCP) experiments are conducted to demonstrate the crack retardation effect following LP treatment. Digital image correlation (DIC) method is also employed to obtain the full field displacement around the crack tip to evaluate the enhancement of crack closure level behind pre-crack tip. The results show that crack arrest and retardation and hence a significant fatigue life promotion are observed for the pre-cracked specimen with LP treatment. It even sustains more loading cycles than the undamaged specimen with LP treatment. DIC analysis reveals that the immediate enhancement of crack closure level is introduced behind the crack tip due to high-dynamic loading of LP treatment. Plastic deformation produced by the high dynamic loading of LP, is possibly dominant to introduce crack retardation behind the pre-crack tip.

Yongxiang Hu, Han Cheng

Application of Laser Peening for Cold Work Steel

Forming technology using dies is utilized by various industries because of its reasonable price and high productivity. Cold forging technology is used in the automotive industry because it can make high precision products. However, die lifespan is a major concern because dies make up the largest proportion of manufacturing costs in cold forging. To improve die life, one can ensure the die’s exact physical properties through fundamental material development, or improve the die’s fatigue life through surface reforming. Laser peening technology mainly progressed as a technology for fatigue life improvement of aerospace parts. As a result, there is much literature about special materials (ex. Titanium, Inconel alloy). On the other hand, there is little literature about tool steel, which is used for cold forging and die-casting. In this study, basic research was conducted to determine the possibilities of laser peening as technology to improve the fatigue life of cold forging dies. As a result, fatigue strength improvement of JIS-SKD11 needs post-polishing because of Roughening of surface, besides, irregular position of chromium carbide inner material occur large variation of fatigue life.

Norihito Shibuya, Fumiaki Kumeno, Yuki Nakamura, Ryo Yoshinouchi

Influence of Laser Shock Peening (LSP) on the Material Properties of Additive Manufactured IN718

Surface treatments such as laser shock peening (LSP) have been attempted to increase the usability of additive manufactured (AM) IN718. This paper investigates the influence of industrial LSP on IN718 manufactured by both the traditional wrought and AM process. The result of the mechanical properties and microstructure of the produced specimens, directly after the manufacturing process and after AMS 5663 heat treatment are presented. The LSP treated AM component has around 25% less compressive residual stress throughout the depth as compared to its wrought counterpart despite using the same LSP energy densities. Microstructural characterisation technique (EBSD) suggested that the AM IN718 has a higher stored strain energy as compared to the wrought components.

Ching Kiat Yong, Geoff D. West, Greg J. Gibbons, Chow Cher Wong

A Comparison of Surface and Sub-surface Features Induced by Shot Peening vs. Laser Peening on a Duplex Aged Beta Ti Alloy

The paper presents a study of the surface and subsurface characteristics induced by laser peening without coating (LPwC) and dual shot peening (DSP) on the duplex aged Ti-15 V-3Al-3Cr-3Sn alloy. In 3D-optical topography analysis, DSP resulted in a six-fold enhancement in the surface roughness (Sa). Whereas, LPwC resulted in unaltered surface roughness (Sa) compared to the polished/unpeened sample. In cross-sectional microstructure studies, deformed grains and heat affected zones were observed in the near surface region of shot peened, and laser peened samples respectively. Moreover, compared to bulk hardness, shot peening and laser peening has resulted in maximum increment of ~28% and ~12% in microhardness of the near peened surface region respectively.

S. Sudhagara Rajan, Geetha Manivasagam, Sathya Swaroop, Nageswara Rao Muktinutalapati

Effect of Laser-Induced Microstructure in Cavitation Erosion Performance of Martensitic Stainless Steel

Cavitation erosion causes material removal from the surface of metal components submerged under swift flowing fluid due to implosions of gas bubbles on their surface. Since erosion is a surface degradation phenomenon, laser surface hardening can be a promising solution to tackle this problem without affecting the bulk properties of material. Laser acts as a localized surface heater which induces rapid non-equilibrium phase transformation and produces hard microstructure near the surface. In this paper, the effect of laser-induced microstructure on cavitation erosion performance of AISI 420 martensitic stainless steel is systematically investigated. Surface hardness as high as 700 HV is recorded after laser hardening and the microstructure consisted of fine carbides and retained austenite in a martensitic matrix. Such microstructure is attributed to result in high cavitation erosion resistance. The cavitation erosion resistance of laser hardened surface was found to be 18 times higher than that of untreated surface. The results indicate the significance of microstructural transformation induced by laser treatment on erosion performance of stainless steels.

Niroj Maharjan, Dennise Tanoko Ardi

Effect of In-Situ Laser Remelting on the Microstructure of SS316L Fabricated by Micro Selective Laser Melting

Due to the increasing attention on additive manufacturing of micro components, an in-house micro-selective laser melting (SLM) system using a fine laser spot size and a small layer thickness with an ability to handle fine powders has been developed recently. In this research work, in-situ laser remelting effects on the part density and microstructure of the SS316L parts fabricated using micro SLM have been studied. After every layer of micro SLM, laser remelting was performed using the same laser source. Remelting effects have been investigated at different process conditions with varying laser power and scanning speeds. The effects of remelting on the part porosity and microstructure of the micro SLM parts have been studied. Experimental results revealed that in-situ laser remelting significantly influences the part density and microstructure of the 316L micro SLM parts. The study highlights that in addition to the purpose of improving the surface finish, laser remelting can be used to tailor the microstructure and hence mechanical properties of the micro SLM parts.

Balasubramanian Nagarajan, Zhiheng Hu, Shubo Gao, Xu Song, Rui Huang, Matteo Seita, Jun Wei

Tailoring Surface Roughness of Micro Selective Laser Melted SS316L by In-Situ Laser Remelting

Micro selective laser melting (SLM) has been developed for the fabrication of complex parts with a fine resolution and smooth finish. Although the fine laser spot size, fine powder size and thin layer thickness can result in a relatively smooth surface compared with the conventional SLM, the surface quality still needs to be improved. In this work, in-situ laser remelting was chosen for the improvement of the surface quality. The effects of in-situ laser remelting process parameters on the surface roughness were investigated using various remelting process parameters. The surface roughness of the top and side surfaces of the samples was characterized using an optical surface profiler. Surface morphology of the parts was characterized using scanning electron microscope. It was observed that the surface texture was evidently different after in-situ laser remelting. Overall, the obtained results indicate that tailoring the top surface roughness of the parts fabricated by micro SLM can be achieved through in-situ laser melting.

Zhiheng Hu, Balasubramanian Nagarajan, Xu Song, Rui Huang, Wei Zhai, Jun Wei

Surface Structuring of Multilayer Coated Cutting Tool Using Nd: YVO4 Nanosecond Laser

Micro-structuring of cutting tools surfaces using laser technology is an important technology for modifying tool chip contact phenomenon. While lasers are becoming popular for surface structuring and texturing of cutting tool surfaces, the size and the shapes that can be obtained has not been fully explored for multilayer coated cutting tools using Nd: YVO4 nanosecond laser. In this study, the micromachining of TiCN/Al2O3/Cr multilayer coated tungsten carbide tools using Nd: YVO4 nanosecond laser at 532 nm wavelength and 7 ns pulse width was undertaken. The impact of the variation of laser travel speed, power, and the number of passes on the structured grooves width and depth is described. The study shows that various grooves’ cross-section profiles can be produced. The performance of a structured cutting tools was also evaluated using orthogonal cutting of steel AISI4140.

Ahmed Alghamdi, Paul Mativenga

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