Friction Analysis on Scratch Deformation Modes of Visco-Elastic-Plastic Materials

Understanding of abrasion resistance and associated surfaces deformation mechanisms is of primary importance in materials engineering and design. Instrumented scratch testing has proven to be a useful tool for characterizing the abrasion resistance of materials. Using a conical indenter in a scratch test may result in different deformation modes, like as elastic deformation, ironing, ductile ploughing and cutting. This paper presents the friction analysis of some deformation modes of visco-elastic-plastic behaving polymer materials, especially PEEK (poly etheretherketone). In general, it is accepted that the friction consist of an adhesion and a deformation component, which can be assumed to be independent to each others. During a scratch test, the friction coefficient is influenced by some parameters, such as the sharpness of indenter, the deformation modes and the degree of elastic recovery. Results show that the adhesion component strongly influences the friction in the elastic and ironing deformation mode (scratching with a blunt cone), friction for the cutting deformation mode (scratching with a sharp cone) is dominantly influenced by the deformation component. From the analysis, it can be concluded that the adhesion friction model is suitable for ironing - elastic deformation mode and the deformation friction model with elastic recovery is good for cutting mode. Moreover, the ductile ploughing mode is combination of the adhesion and plastic deformation friction model

Stick-slip behaviour of a viscoelastic flat sliding along a rigid indenter

The sliding contact of soft material surface due to a rigid indenter is different from metal and some other polymers. A stick-slip motion is more frequently obtained than a smooth motion. By modeling the soft material as low damping viscoelastic material, this study proposes an analytical model to identify the stick-slip behavior of sliding system. The sliding system is a fixed rigid indenter that slides against on a moving soft material surface. A stick-slip model is developed and the motion of the sliding system is assumed to be in a solely tangential direction. By implementing the simple coulomb friction law, an exact solution is presented in the case of no damping of the sliding system. Results show that the periodic displacement of the stick-slip model is strongly depending on the friction force, sliding velocity and material stiffness. Furthermore, the effect of a viscous damping and velocity-dependent friction on the behaviour of the sliding system are discussed

Analisis Alat Uji Getaran Mekanis Dengan Variasi Konstanta Pegas Tanpa Peredam Viskos

Jurusan Teknik Mesin Universitas Wahid Hasyim Semarang memiliki sebuah alat pengujian getaran mekanis yang belum pernah dilakukan pengujian. Untuk itu perlu dilakukan analisis terhadap alat tersebut dengan tujuan untuk mengetahui pengaruh dari ketiga pegas terhadap nilai konstanta pegas (k), nilai faktor peredaman (x), nilai frekuensi pribadi (wn) dengan cara pengukuran dan perhitungan serta mengetahui besarnya nilai simpangan maksimum (Xmak) pada getaran paksa terhadap tiga pegas yang digunakan. Metode penelitian ini dilakukan dengan membandingkan hasil pengukuran dengan teori. Dari hasil penelitian tersebut didapatkan bahwa nilai konstanta pegas (k) pada pegas A adalah sebesar 646,67 N/m, nilai konstanta pegas (k) pada pegas B adalah sebesar 2517,71 N/m sedangkan nilai konstanta pegas (k) pada pegas C adalah sebesar 3538,96 N/m. Untuk faktor peredaman (x) pada pegas A sebesar , pada pegas B sebesar dan pada pegas C sebesar . Dari hasil antara pengukuran dan perhitungan besar prosentasi nilai frekuensi pribadi ( ) pada pegas A sebesar 11,93 %, pada pegas B sebesar [25,95%] dan pada pegas C sebesar 0,164 %. Untuk hasil simpangan maksimum (Xmak) pada pegas A sebesar 36,48 mm pada putaran motor sebesar 125 rpm, pegas B sebesar 40,49 mm pada putaran motor sebesar 149 rpm dan pegas C sebesar 42,28 mm pada putaran motor sebesar 226 rpm

Analysis of the effect of ventilation hole angle and material variation on thermal behavior for car disc brakes using the finite element method

Brakes are used to slow down or stop a moving object. The temperature of the disc brake will rise as a result of the conversion of kinetic energy from vehicle speed into thermal energy during the braking operation. To prevent harm to the disc brake or other components, the heat generated by this disc brake must then be released into the environment. Therefore, it is crucial to provide effective heat dissipation to the environment. Increasing the surface area where heat is dissipated into the environment is one potential solution. In this study, the variation of the drill hole angles and groove hole angles is proposed as a geometry modification to encourage greater heat dissipation in disc brakes. In addition, the thermal performance of disc brakes made from various types of materials is assessed using finite element analysis. The materials employed are carbon ceramic, stainless steel, and gray cast iron. The numerical findings show that the groove-type disc brake with a ventilation hole angle of 0° angle has the lowest maximum temperature. In addition, it is revealed that the disc brake made of gray cast iron material results in the lowest peak temperature. The numerical results also indicate that due to the thinning of the geometry, the addition of the ventilation hole angle contributes to the phenomena of temperature concentration in specific areas of the disc brake. This study demonstrates that disc brake material and ventilation hole play a significant effect in altering the thermal characteristics.</p

Analisis konstruksi pipa pompa suction 112-JB

The 101-JTC condenser tank has excess steam condensate due to the addition of admission steam from 101-JT. Therefore, it is necessary to design a piping system that connects 101-JTC condenser tank with the 112-JB pump to drain the condensed excess steam. The designed piping system will encounter a dynamic response caused by fluid flow fluctuation over the time. This dynamic response causes the pipe to experience stress. To find out the resulting voltage which will not cause damage or failure, it is necessary to estimate the safety factor in a piping system that has been given static and dynamic loading. This research uses the fluid structure interaction or FSI method with the help of ANSYS software as a simulation tool. The results of this study are, the flow in the pipe causes an impact load which makes the structure vibrate freely damped. The resulting dynamic response describes, the structure displacement amplitude decreases with increasing time. This indicates a stable vibration. Finally, when viewed from the value of stress against time, the fatigue that occurs in the pipe structure induce a stress below the stress limit on Goodman diagram. It can be estimated that the structure has no service life limit. The fatigue safety factor is 7.1

Thermo-hydrodynamic Analysis of Multistep Journal Bearing using Computational Fluid Dynamics Simulation

Journal bearing is a machine element that is used to maintain the continuous rotation of the shaft on its axis. The rising demand for efficient and economical journal bearing applications has resulted in increased demand for high-speed machines. An increase in engine speed raises the distribution of pressure, temperature, and vapor volume fraction. Most of the research still only focuses on increasing pressure distribution and load-carrying capacity. However, the value of friction force, temperature distribution, and vapor volume fraction must also be considered such that the lubrication of the journal bearing is close to the real situation. Therefore, the research was conducted by varying the geometry modelling through multistep textures using viscous boundaries and thermo-hydrodynamic lubrication. Owing to the high load and speed usage on multistep journal bearings, research on the effect of eccentricity ratio and inlet and outlet temperatures on the tribological performance of multistep journal bearings was conducted. The analysis has been performed using a multistep journal bearing modelling 3D computational fluid dynamics considering the effect of cavitation on temperature. The results of this study indicate that the use of multistep textures on journal bearings can reduce friction force, temperature, and vapor volume fraction. The variation of the eccentricity ratio shows that a high eccentricity ratio leads to a high three parameters (i.e., friction force, temperature, and vapor volume fraction). Finally, for variations of inlet and outlet temperatures, such parameters are high when the inlet and outlet temperatures are high.</p

Sliding Wear Modeling of Artificial Rough Surfaces

Surface roughness plays an important role in machine design. In the micro-scale when two engineering surfaces are brought into contact, the real contact area occurs at isolated point of asperity. Wear is one of some effects of contacting surfaces. This paper presents a modeling of sliding wear at asperity level on the artificial rough surfaces. The surface roughness is represented by spherical asperities at the hemispherical pin that is developed from the existing model. The wear model is based on the simple analytical solution. The combination of Archard's wear equation and finite element simulation is performed to predict the wear. Results show that the increasing of sliding distance give the increasing of wear depth, wear scar diameter and wear volume of the asperity. Wear at the center of the contacting rough surface is higher than the its surrounding.

Numerical Study of Comparison of Thrust Bearing Slip-No Slip Condition on Acoustic Performance

The acoustic power level (APL) produced by a thrust bearing during operation has a major effect on its performance. Therefore, this research aimed to investigate the impact of slip engineered on the noise generated by thrust bearings. A numerical approach was used to simulate open pocket bearings with varying film thickness depths. At the initial location of the slip area, three bearing models were analyzed: pocket slip, pocket no slip, and smooth slip. The results show that implementing slip can reduce noise levels, turbulence kinetic energy (TKE), and turbulence eddy dissipation (TED) rate. The average APL, TKE, and TED values were the lowest at the high film thickness.</p

Chemical composition and antibacterial activity of coconut-shell liquid smoke to maintain the texture of fresh meat

This research focused on the evaluation of raw broiler chicken meat texture and pathogenic antibacterial effect under the treatment of grade 2 coconut-shell liquid smoke (CSLS) as a food preservative. Compound identification of grade 2 CSLS was conducted using the GC-MS method. The main chemical compounds of CSLS were polyunsaturated fatty acid derivates, fatty acid and phenol. The evaluation of texture was conducted on raw broiler chicken meat under the treatment of grade 2 CSLS during storage at 25 ℃ for 7 days. The effect of antibacterial activity of grade 2 CSLS with different concentration (i.e., 5%, 25%, 50%, and 75%) were tested using Gram-positive bacteria on several pathogenic bacteria such as L. monocytogenes, S. aureus, P. Aeruginosa, and E. coli. The results indicated that grade 2 CSLS influenced the inhibited zone of L. monocytogenes, S. aureus, P. Aeruginosa, and E. coli respectively with linear correlation. The optimal concentration of grade 2 CSLS resulted in a concentration of 50%, which was the most optimal against L. monocytogenes, S. aureus, P. Aeruginosa, and E. coli as pathogenic bacteria strains