Muslim Mahardika

Effect of cold working and sandblasting on the microhardness, tensile strength and corrosion resistance of AISI 316L stainless steel

The aim of this work is to investigate the effect of cold working and sandblasting on the microhardness, tensile strength and corrosion rate of AISI 316L stainless steel. The specimens were deformed from 17% to 47% and sandblasted for 20 min using SiC particles with a diameter of 500–700 μm and an air flow with 0.6–0.7 MPa pressure. The microhardness distribution and tensile test were conducted and a measurement on the corrosion current density was done to determine the corrosion rate of the specimens. The result shows that the cold working enhances the bulk microhardness, tensile and yield strength of the specimen by the degree of deformation applied in the treatment. The sandblasting treatment increases the microhardness only at the surface of the specimen without or with a low degree of deformation. In addition, the sandblasting enhances the surface roughness. The corrosion resistance is improved by cold working, especially for the highly deformed specimen. However the follow-up sandblasting treatment reduces the corrosion resistance. In conclusion, the cold working is prominent to be used for improving the mechanical properties and corrosion resistance of AISI 316L stainless steel. Meanwhile, the sandblasting subjected to the cold worked steel is only useful for surface texturing instead of improving the mechanical properties and corrosion resistance.

Effect of Sandblasting and Surface Mechanical Attrition Treatment on Surface Roughness, Wettability, and Microhardness Distribution of AISI 316L

Surface roughness and wettability determines the stability of bone-implant integration. Stable implants can be found in those with a rough and hydrophilic surface. Sandblasting and surface mechanical attrition treatment (SMAT) are among the current techniques to obtain surface with such typical properties. In addition, both treatments increase mechanical strength of metal through surface grains refinement. In this paper, the effect of sandblasting and SMAT on surface roughness, wettability, and microhardness distribution of AISI 316L is discussed. All treatments were conducted for 0-20 minutes. The result shows a rougher and a more hydrophilic surface on the sandblasted samples rather than on those with SMAT. A harder surface is yielded by both treatments, but the SMAT produces a thicker hardened layer.

Surface modification of titanium using steel slag ball and shot blasting treatment for biomedical implant applications

Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the surface and subsurface of titanium were studied in this paper. The treatments were conducted for 60–300 s using 2–5 mm steel slag balls and 3.18 mm spherical shots. The surface morphology, roughness, and elemental composition of titanium specimens were examined prior to and after the treatments. Irregular and rough titanium surfaces were formed after the treatment with the steel slag balls instead of the spherical shots. The former treatment also introduced some bioactive elements on the titanium surface, but the latter one yielded a harder surface layer. In conclusion, both steel slag ball and shot blasting treatment have their own specialization in modifying the surface of metallic biomaterials. Steel slag ball blasting is potential for improving the osseointegration quality of implants; but the shot blasting is more appropriate for improving the mechanical properties of temporary and load bearing implants, such as osteosynthesis plates.

Acoustic Emission Signals in the Micro-EDM of PCD

The mechanism of fracture in micro-electrical discharge machining (-EDM) processes is related to the discharge pulses energy. This paper investigates the correlation of fractures and discharge pulses energy in the -EDM of polycrystalline diamond (PCD) to the acoustic emission (AE) signals. The evaluation of fracture mechanism was done by measuring the generation and propagation of elastic wave in single discharge pulse by using AE sensor. The results show a strong correlation between fractures and discharge pulses energy to the AE signals and mechanism of material removal in the -EDM processes.

Material Removal and Fracture Detection in Micro-EDM Processes

The important thing in micro-machining is its accuracy. The Micro-Electrical Discharge Machining (micro-EDM) is a promising method in micro-machining, because (1) the process is independent on the hardness of the workpiece but only depends on its thermal conductivity and melting point and (2) it can be used to machine materials with highly complex geometrical shapes using a simple-shaped tool electrode. However, the process in micro-EDM is not totally well-known, especially related to the formation of discharge pulse energy and the fracture phenomena. In the micro-EDM processes, the formation of discharge pulse energy is a complex phenomenon, since it is related to many parameters such as discharge gap, charge voltage, capacitance, and tool electrode wear. In this paper, the Acoustic Emission (AE) sensor is used to detect the changes of discharge pulse energy during machining of brass using micro-EDM. The results shows that the AE signals can detect and explain the fracture phenomena during the micro-EDM processes.

Study on the Effect of Nano and Micro MoS2 Powder in Micro-Electrical Discharge Machining

The application of powder mixed dielectric to improve the efficiency of electrical discharge machining (EDM) has been acknowledged extensively. However, the study of micro-size powder suspension in micro-EDM field is still limited. In this research, nano and micro size powder of MoS2 were used as catalyst agent. Powder suspension in different size was able to provide significant improvement in material removal rate and surface quality to increase the efficiency in μ- EDM processes.

Increasing Yield Strength of AISI 316L Plastically Deformed by Expanded Hole Techniques

AISI 316L has been used to produce implant plates such as dynamic copmresion plates (DCP). The implant plates might experienced failure due to either suffer higher stresses exceeding the allowable maximum strenght or presents small crack growing through fatigue mechanism. Most of DCP fractures occured at the gliding holes region. This study conducted improving strength of DCP locally on the gliding holes. Strengthening on the gliding holes of DCP was performed by cold working method involving plastically deformation using an expanded hole technique. This study was conducted by both experimental and numerical simulation. Increasing strength locally on the gliding hole region was evaluated by measuring some parameters incorporated with strain hardening mechanism such as hardness and residual stresses. Increasing yields strength locally on the hole region was estimated by Takakuwa’s formulas. By this method, yields strength of the gliding hole of DCP made of AISI 316L increased from 325 MPa to be 600−1050 MPa.

Development of the Gliding Hole of the Dynamics Compression Plate

The gliding hole of the dynamics compression plate is designed to facilitate relative movement of pedicle screw during surgery application. The gliding hole shape is then geometrically complex. The gliding hole manufactured using machining processes used to employ ball-nose cutting tool. Then, production cost is expensive due to long production time. This study proposed to increase productivity of DCP products by introducing forming process (cold forming). The forming process used to involve any press tool devices. In the closed die forming press tool is designed with little allowance, then work-pieces is trapped in the mould after forming. Therefore, it is very important to determine hole geometry and dimensions of raw material in order to success on forming process. This study optimized the hole sizes with both geometry analytics and experiments. The success of the forming process was performed by increasing the holes size on the raw materials. The holes size need to be prepared is diameter of 5.5 mm with a length of 11.4 mm for the plate thickness 3 mm and diameter of 6 mm with a length of 12.5 mm for the plate thickness 4 mm.

UAV long range surveillance system based on BiQuad antenna for the Ground Control Station

Unmanned Aerial Vehicle (UAV) that used in long-range surveillance missions need an optimal performance of signal communication. The goal of this system is to communicate between the UAV and ground station in real time. The maximal performances characteristics of antenna such as gain, Standing Wave Ratio (SWR), impedance, polarization, and frequency are important for the UAV communication. Nowadays, antennas are easy to find, but many of them are not appropriate because the characteristic and mission of antenna are not compatible. In this research, to optimize the communications between UAV and Ground Control System (GCS), we use BiQuad antenna for telemetry. Our BiQuad antenna has a vertical polarization which is made by two loops that work in the frequency of 433 MHz and it is the best performance. For higher performance, this antenna component is made by unusual BiQuad material such as Printed Circuit Board (PCB) for the reflector, Teflon cable to connect the element with RP-SMA connector, and without using RG-8 cable. BiQuad antenna simulated by using the MMANA-GAL software to analysis and simulation characteristic of antenna. The characteristic of these antenna based on the research SWR= 1.2, F/B = -0.14 dB, Impedance = 50.9 ohm, Gain = 11.24 dBi, and frequency 433 Mhz. Based on these data result, this antenna is very appropriate for UAV long-range surveillance missions.

Influence of Clearance and Punch Velocity on the Quality of Pure Thin Copper Sheets Blanked Parts

Research on the influence of clearance and punch velocity to determine the quality of the punched edge were conducted. This study uses pure copper sheet material with the clearance variation of 2.5, 5, 7.5 and 10%. Punch velocity is based on the ability of about Micro Punch CNC machine which is 100 and 2600 mm/min. At highest speed with a clearance of 2.5%, sheared zone is of about 395 pm or 79% of the material thickness. It can be concluded that the punch velocity gives positive influence on the sheared zone in copper. Basically the ideal outcome of the sheared edge of punching result is having rollover and small burr and contain at least 75% of the shear zone. This can be achieved with a clearance of 2.5%.