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Composite is a combination of materials consisting of 2 or more materials lead to the composite material has different mechanical properties and characteristics as desired. Composite materials are divided into two types, synthetic fibers and natural fibers. Most of the natural fiber types use jute fiber, as it is a candidate as a reinforce material to produce lightweight, strong and environmentally friendly composite materials as mixing polyester composites. Although composites can be made according to the desired shape, the final work, such as the machining process, is also needed for making several shapes such as making holes with the drill process. Furthermore, twist drilling, can induce damage due to the imperfections of the holes that are produced, resulting asymmetrical holes. This allows complicate assembly and reduce its strength. The parameters use are spindle speed 100 rpm, 700 rpm and 1400 rpm and feeding 0,1 mm/rev, 0,2 mm/rev, 0,3 mm/rev, 0,5 mm/rev and 0,7 mm/rev. The results obtained that using 100 rpm and feeding 0.5 to 0.7 can make imprecise and resulted delamination of the hole. Increased spindle speed such as 700 and 1400 rpm and higher feed rate, resulted increase the accuracy of the hole

The obstacle faced during the fatigue test is the waiting time which is quite long and inefficient, especially for test specimens made of ductile metal with waiting times of up to several days. The research method includes reducing the specimen radius to obtain a flexural stress approaching 400 MPa which was originally 229 MPa from a radius of 254 mm to 240 mm with the results of turning the original specimen obtained a minimum diameter of 8.6 mm is reduced to 7.3 mm at a maximum loading of 10 kg. Results of the research are brass specimens C3604BD type with a minimum diameter of 8.6 mm at a flexural stress of 298 MPa showing a fatigue life of 2455546 cycles with a test duration of 1754 minutes and a minimum specimen diameter of 7.3 mm at a flexural stress of 299 MPa showing a fatigue life of 684311 cycles with a test duration of 489 minutes which means that with a minimum specimen diameter of 7.3 mm the fatigue life is 3.59 times shorter than a minimum specimen diameter of 8.6 mm. Meanwhile, for aluminium AA1101 type with a minimum specimen diameter of 7.3 mm at a flexural stress of 182 MPa, the fatigue life is 422117 cycles with a test duration of 278 minutes and with a minimum specimen diameter of 8.6 mm at a flexural stress of 183 MPa, the fatigue life is 389232 cycles with a test duration of 302 minutes which means that with a minimum specimen diameter of 7.3 mm the fatigue life is 1.05 times shorter than the minimum specimen diameter of 8.6 mm or almost the same.

A kinetic model was proposed for the synthesis of methane to be dimethyl ether (DME) in one reaction step from (CH 4 + O 2 ) and (CH 3 OH) to dimethyl ether using kinetic CuO-ZnO /gAl 2 O 3 catalyst parameters. The bifunctional catalyst of the series kinetic reaction model according to the experimental results obtained under isothermal conditions in a pipe flow reactor under various operating conditions: 225-325 ° C; 10 bar gauge; Residence time, 16-57.0 (g Catalyst) hour (mole CH 4 ) -1 . An important step for modeling is the synthesis of methanol from (CH 4 + O 2 ) and the synthesis of (CH 3 OH to DME) is methanol dehydration (very fast), and water-shifting and CO 2 (equilibrium) reactions. The effects of water inhibition and CO 2 were also taken into account in the synthesis of methanol and the formation of hydrocarbons. The dehydration advantage of methanol can achieve higher yields above 60 % methanol that was converted to DME and the remaining 5% methanol if (CH 4 + O 2 ) comes in at 10 bar gauge and 375 ° C. At higher temperatures produces CO 2 and H 2 O. Methane-methanol-DME series reaction model follows single-order gas phase reaction to methane and methanol with k 1 = 0.195 minutes -1 and k 2 = 0.115 minutes -1 The time and maximum concentration occurs in the formation of methanol constituents 9.5 minutes and 0.44 mole

This paper presents flexural properties related to vibration behavior of jute reinforced polyester composite. The goal of the research is to seek green composite material that exhibits good strength and flexural properties along with good damping property designed for wind turbine blades. The material for reinforcement in the present study is jute fiber. The material for matrix is polyester resin. Glass and carbon fiber are used for hybridization. Specimens were fabricated by vacuum infusion technique. Laminates were constructed by stacking jute fiber clothes. Hybrid laminates were fabricated by stacking jute clothes covered by one ply glass cloth and jute clothes covered by one ply carbon cloth. Static flexural and free vibration tests were carried out to obtain the elastic modulus and vibration behavior of specimens, respectively. The result shows that the configuration of jute fiber cloth and glass fiber hybridized laminates possesses compromised properties between flexural properties and damping ratio.

Pengembangan desain kontrol kinematic sangatlah penting dalam pengembangan kontrol untuk robot beroda. Hal ini sangat dibutuhkan mengingat bahwa robot beroda memiliki banyak parameter yang mampu merubah persamaan kontrol kinematiknya terutama pada kontrol kinematik untuk robot beroda dengan jenis roda omnidirectional, baik dari segi jenis roda yang digunakan hingga jumlah roda penggerak yang digunakan. Dengan berbagai macam hal yang dapat merubah persamaan kontrol kinematiknya, maka pada makalah ini dibuat sebuah persamaan kontrol kinematik yang general, yang dapat diaplikasikan untuk berbagai macam roda omnidirectional, serta berbagai jumlah roda yang digunakan. Selain itu persamaan general yang telah dibuat, diaplikasikan untuk menguji respon robot beroda dengan menggunakan 6 buah omni-wheels untuk menguji hasil respon dari persamaan general kontrol yang telah dibuat. Pengujian dilakukan dengan menggunakan simulasi program dengan menggunakan pemrograman dengan menggunakan Bahasa pemrograman python. Hasil yang didapatkan menunjukkan robot mampu bergerak sesuai dengan arah gerak target yang ditentukan, yaitu membentuk pola jalur yang linier serta mampu bergerak membentuk pola lingkaran dan pola setengah gelombang sinus. Hal ini menunjukkan bahwa kontrol kinematik yang dirancang mampu membuat robot bergerak sesuai dengan yang direncanakan. Hasil dari respon robot berupa sinyal kontrol, pola yang dibentuk serta nilai perubahan error disajikan dalam bentuk grafik. Development of the kinematics control is very important for the development of kinematics control for mobile robots. This is very necessary because mobile robots have a lot of factors that can manipulate the equation of its kinematic control, such as the type of wheels, the number of wheels, etc. With this kind of problem, it necessary to generate a general equation for the robot’s kinematic control, which in this journal we purpose the general equation for the mobile robot control, and we evaluate the outcome by applying the general equation into the 6 omnidirectional robot control. To make a valid statement, we simulate the control to understanding the control outcome by using a python program. The results of the simulation show us that the robot can move as planned, that the robot produces a linear trajectory, circular trajectory, and half sine wave trajectory. Depends on the results, it can be concluded that the proposed kinematics control equation can make the robot moves well as we planned. The results of the respons, the trajectory, and the changes in error values ​​are presented in graphical form

Wild flow of water below the surface of the land toward the road and the foundation of houses, road damage due to land subsidence, damage to the houses foundations, mosquito larvae lodged due to standing water, and the emergence of foul odors as a problem faced. The purpose of service is to help the community to expedite the flow of water from the rice-fields, rain and household waste, drain the gutter as a source of disease (dengue fever) through the gutter, restore the flow of wild water into the gutter, and maintain a healthy hygiene environment. The method applied was consultation with residents to determine the construction design of the channel, dismantling the broken gutters and there was a wild flow of water to the street/house yard, casting with a high-strength concrete until strength enough, repairing the cracked gutter walls with cement paste, and submitting the results of normalization to the Chairman of the local Neighborhoods Association/RT. Normalization results in the form of clean gutters, rice-fields-rain-discharged water from houses flowing through the gutters smoothly without leaking and no puddles, there is a synergy between State Polytechnic of Malang and the community in obtaining a smooth flow of water from rice-fields/rain/discharged houses into the house sewer in RW 06 Tasikmadu-Lowokwaru-Malang which implies awareness of citizens of a clean, healthy and orderly environment. Conclusions of the results of normalization as a flow of water from various origins through a structured sewer smooth water flow, prevention of disease, and providing beauty environmental.

Fatigue life prediction for engineering material is important for predictive maintenance to support accident prevention in a high-risk equipment. The study aims to determine the ability of the machine prototype of rotating bending type fatigue test and to find out the fatigue life of Nylon and cast iron specimens. By knowing the fatigue life of a plastic and ferrous metal material, the prediction of fatigue life can be applied to a maintenance plan. The design and manufacture of rotating bending fatigue testing machines equipped with copy turning devices can be used to prepare specimens from plastic/soft metal materials, thus becoming an integrated fatigue test machine. The method used includes determining the standard size of fatigue test specimens, turning various fatigue test specimens, carrying out fatigue test specimens of nylon and cast iron materials, and analyzing the results of fatigue tests. The test results of the fatigue test machine prototype showed the ability to turn plastic and soft metal materials, and the fatigue life for Nylon 6.6 ranging from 659 to 13216 rotation for breaking the specimens at 229 to 26 MPa stresses, and for cast iron from 142 to 22863 rotation at 229 to 147 MPa stresses.

Technological advances allow researchers to develop advanced arm robots and can safely work side by side with humans Therefore, a robot arm controller can be designed in such way that the robot arm can move along the desired trajectories and act upon external influences, in this last case, the torque sensor plays an important rule. Currently torque sensors are available in the market has a high price. In this work, an inexpensive robot joint torque sensor is presented. Most parts of this sensor are made using 3D printers. While the other components are easily can be found in the market and with a relatively low-costs. The development of this sensor is intended to facilitate the prototyping of the robot arm for educational and research purposes. The basic idea of the sensor mechanism is to convert torque into a force absorbed by a spring. Then, the encoder senses the direction and the value of the input torque. This torque sensor can be easily too customized. Thus this sensor can be tailored to the needs by replacing some parts such as encoder and spring. The mechanism of this sensor can also be adjusted with the actuator to be paired. Experiments have been conducted to verify the accuracy and the performance of the proposed torque sensor.

The fatigue limit of a plain specimen of a tool steel JIS SK85 was investigated. The initial crack length in the fatigue process is related to the size of a single crystal in the case of low carbon steel. However, that is independent of the crystal size in the case of pure aluminum, a lamellar pearlitic steel, etc. In this study, the relationship between the initial crack length and the fatigue limit was investigated. The original microstructure of this material includes a spherical microstructure. However, after heat treatment under some conditions, that microstructure changed to a lamellar microstructure. The fatigue limit of heat-treated SK85 could be evaluated by an equation in which the parameters are the hardness and initial crack length. Finally, this result was discussed based on the observations of crack growth behavior and fracture surface.

Tensile and fatigue failure behavior of C/C composite with fine woven fiber-cloth laminates was investigated in several configurations of specimens. A 3.2mm thick plate, which has the quality of machine-ability, was used for testing material. During the machining process of specimens, care was taken that the fiber directions of 0°/90° and -45°/45° orientation were set against the loading direction. Tensile and fatigue tests were performed under load control techniques. Notches were made on some specimens, and their fracture behavior was observed. Some different notch shapes were used to investigate the effect of fiber orientation on the fracture behavior of the material. The result showed that the critical fracture stresses of the specimen were affected by fiber orientation and notch shape. In addition, the shear stress conditions affected the fracture behavior.

Fatigue and fracture behavior of C/C composite with fine-woven carbon fiber laminates was investigated in several schemes of notched specimens. Slits and holes were cut in the specimens as notches, and the effect of fiber orientation and notch configuration on the fatigue behavior was examined. The fatigue limit was defined by a simple method that used incremental applied stress and number of cycles. The fatigue limit was dependent on fiber orientation, notch configuration and stress ratio (ratio of minimum cyclic stress to maximum cyclic stress). It was found that the fatigue limit was determined by the true stress rather than by the stress concentration in the present material and was not affected by variations in slit depth. Also, the fracture behavior was controlled by shear deformation.

A technical method for arresting further crack growth from cracks by drilling holes in the vicinity of the crack tips was investigated. A series of fatigue-crack-growth tests was performed using double-edge-pre-cracked specimens. In some specimens, holes were drilled in the vicinity of the crack tips. Also, pins were inserted into the holes in some cases. The crack growth lives of some specimens were longer than those of specimens without holes. The longest fatigue life was observed in the case of a specimen with the pins. Drilling holes and inserting pins could change the growth direction of the cracks, and then the coalescence of cracks, which grow from both edges of a specimen, could be prevented. Also, it was found that compressive residual stress, which occurred by inserting pins, was more effective to retard the crack growth than reducing the stress concentration around initial crack tips, which occurred by drilling holes. Therefore, it is concluded that inserting pins into holes drilled in the vicinity of the crack tips is the most effective method for retarding crack growth and for preventing cracks from coalescing.

To retard crack growth, a stop hole is drilled at the crack tip. Reducing the stress concentration factor is the main reason for that. Also, it was investigated whether fatigue crack reinitiation and growth from a stop-drilled hole can more effectively be retarded by providing additional holes. In the present study, stresses at the periphery of holes were analyzed using software for two-dimensional elastic problems based on body-force method. The stress concentration factors for the stop-drilled holes and additional holes were investigated. The stress concentration tendencies can be used to estimate the site where a fatigue crack will initiate from a hole. The calculation results showed that the additional holes had positive or negative effects on lowering stress concentrations at the stop-drilled holes which depended on a combination of the arrangement and size of the two kinds of holes. The effectiveness of the arrangement of a stop-drilled hole and an additional hole on retarding crack growth can be evaluated by stress concentration analysis.

The purpose of the present study is to propose a new technical method for arresting crack initiation at stop-drilled holes by drilling ancillary holes following the making of the stop-drilled holes. The main idea of the method is to reduce the stress concentration at the edges of stop-drilled holes. To confirm the effectiveness of the method, analyses were performed by using software for two-dimensional elastic problems based on the body-force method, and some experiments were carried out. The calculation results show that the existence of ancillary holes effectively reduced the stress concentration at the edges of the stop-drilled holes. A close distance between the stop-drilled hole and the ancillary holes resulted in lower stress concentration at the edge of the stop-drilled hole. Also, a considerable reduction of stress concentration was obtained by arranging for the diameter of the ancillary holes to be larger than that of the stop-drilled holes. Consecutively, the experimental results showed that the fatigue initiation life was in good agreement with the calculation results.

A technical method for retarding crack growth from pre-cracks by drilling holes in the vicinity of the crack tips was investigated. A series of fatigue crack growth tests were performed using double edge cracked specimen. In some specimens, holes were drilled in the vicinity of tips of precracks. Also, calking pins were inserted into holes in some cases. The crack growth lives of drilled specimens were longer than those of specimens without holes. The longest fatigue life was observed in a case of specimen with the pins. Drilling holes and calking pins could change the growth direction of cracks, and then the coalescence of cracks, which grew from both edges, could be prevented. Also, it was considered that the compressive residual stress, which occurred by calking pins, was more effective to retard the crack growth than the reducing stress concentration around initial crack tips, which occurred by drilling holes. Therefore, it is concluded that calking pins into holes, which drilled in the vicinity of crack tips, is the effective method for retarding crack growth and for preventing coalescences of cracks.

The purpose of present study is to propose a new technical method for retarding fatigue crack reinitiation and growth from the crack tip introduced-stop-drilled hole by providing additional holes. To demonstrate the validity of the proposal, analyses using software for two-dimensional elastic problems based on body-force method were done. Furthermore, a series of experiments was carried out for comparison. The calculated results showed that the additional holes give positive or negative effects on lowering stress concentration at the stop-drilled hole, which varies depending on combination of arrangement and size of both holes. Calking pin into the additional holes which yields internal pressure on the periphery, was found also advantageous for reducing stress concentration at the drilled hole. Finally, the calculated results showed relatively good agreement with the experimental results.

The formation behavior of factory-roof in circumferential notched specimen was examined. To achieve an observation of cracks in internal of material, two plastics were used for testing. One was acryl and the other was polycarbonate. Cyclic torsional tests were performed with and without application of static tension. With the polycarbonate, a factory-roof was not formed in fracture surface. However, using acryl, that was observed when cyclic torsion tests were conducted with static tension. Therefore, the discussion was focused at the results in acryl. When the factory-roof was formed, many small cracks were initiated and grew by shear mode, followed by coalescence and branching of them. After that, the crack growth mode was changed from shear mode to mode I. During mode I crack growth, the formation of the factory-roof was observed.

The fatigue crack initiation life and growth rate are affected by experimental conditions. A corrosive environment can be created in a laboratory by means of dropping salt water onto the specimen surface, spraying chloride mist into the experimental chamber, etc. In the case of smooth specimens of some metals, fatigue life is shortened and the fatigue limit disappears under such corrosive experimental conditions. In this study, the effects of intermittent spraying of 3% NaCl solution-mist on corrosion fatigue behavior were investigated. The material used was 0.37% carbon steel. This is called JIS S35C in Japan. Spraying of 3% NaCl solution-mist attacked the surface layer of the specimen. It is well known that the pitting, oxidation–reduction reaction, etc. affect the fatigue strength of metals in a corrosive environment. We carried out corrosion fatigue tests with smooth specimens, holed specimens and slit specimens. Then the effects of such specimen geometry on the fatigue strength were investigated when the NaCl solution-mist was sprayed onto the specimen surface. In the case of lower stress amplitude application in slit specimens, the fatigue life in a corrosive atmosphere was longer than that in the open air. It is discussed that the behavior is related to the crack closure which happens when the oxide builds up and clogs the crack or slit.