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Vibration in many industries commonly generated by the operation mechanical equipment such as extruder, mixer, blower, compressor, turbine, generator etc. Vibration propagates into the floor and attacks the pipe around those mechanical equipment. In this paper, the influence of vibration in a pipe on the CaSO4 scale formation was investigated to understand the effect of vibration on the kinetics, mass of scale, crystal phases and crystal polymorph. To generate vibration force, mechanical equipment was prepared consisted of electrical motor, crankshaft, connecting rod and a vibration table at where test pipe section mounted. Deposition rate increased significantly when the vibration affected to the system i.e. 0.5997 and 1.6705 gr/hr for vibration frequency 4.00 and 8.00 Hz. The addition 10.00 ppm of citric acid declined the deposition rate of 8 Hz experiment from 3.4599 gr/hr to 2.2865 gr/hr.

Due to degenarative disorder of articular cartilage, hip joint need to be replaced with an artificial hip joint. Currently, the modular design of artificial hip joint become popular in the procedure because the modular type’s provide flexibility for the surgeon. But, there were several report about the failure of modular version, and the failure was likely to happen on the neck part. The main focus of this research was to ensure the design safety of present artificial hip joint using FEM (Finite Element Method). The present artificial hip joint was loaded with force that occurred due to jump activity, and there were 3 type of materials that used in this research (Titanium Alloy (Ti-6Al-4V), Cobalt - Chrome alloy, and stainless steel (SS) 316L). The result is maximum stress that occurred on Ti-6Al-4V, Co-Cr alloy, and SS316L were 296.13 MPa, 294.02 MPa, and 294.51 MPa, respectively. The Ti-6Al-4V perform the best among the others with the safety factor of 2.7.

Failure of cement mantle of bond loosening between liner and cement mantle is an important issue in total hip replacement. Two factors that commonly cause cement mantle failure are initial crack and stress. A solution for reducing stress on the cement mantle has been proposed by adding insertion material between liner and cement mantle. Nevertheless, further study is needed to optimize the proposed solution. A possible option is to vary the thickness of the insertion material. If the thickness of the PMMA material is constant, then the variation of the insertion thickness will be followed by the variation of the thickness of the liner. Consequently, the stress value on the liner will follow the variation of liner thickness. The objective of this study is to examine the effect of the thickness variation of the insertion material to stress on cement mantle and liner using finite element simulation. Results revealed that the magnitude of stress and deflection decreased in the cement mantle and the liner along with the increasing thickness of the insertion material.

The indentation technique has been practically proven to be useful in determining mechanical properties of materials, such as hardness and elastic modulus for rubber-like materials (elastomers). However, tensile test method is often conducted because of obtaining the mechanical strength in addition to the elastic modulus of the elastomer. In this paper, a numerical study is proposed to investigate the elastic modulus of the elastomer by applying Finite Element Analysis (FEA). With the availability of Strain Energy Function (SEF) data from the material testing, the investigation is carried out by indentation technique for Natural Rubber (NR) and Styrene Butadiene Rubber (SBR). On the rubber surface, a rigid ball indenter is pressed under specified indentation force and the contact depth resulted is observed. Based on the ASTM (American Society for Testing and Materials) formulation, the elastic modulus from the indentation technique can be estimated. In general, results show that the elastic modulus obtained from the indentation technique agree with the tensile test results. Thus, the proposed numerical method is validly applied in determining the elastic modulus.

Ultra High Molecular Weight Polyethylene called UHMWPE is a unique polymer material that has excellent physical and mechanical properties. UHMWPE material is frequently used in prosthesis. One example of UHMWPE uses in prosthesis is acetabular liner which is one component for Total Hip Joint Replacement (THR) and can also be found for bearing surfaces on the knee, ankle, shoulder, and connective tissue of the joint. UHMWPE material is made by compression molding process. However, UHMWPE wear often causes the failure of artificial hip joints. Therefore, a treatment to reduce the crosslink method is performed. The purpose of this study was to determine the crosslink effect in UHMWPE material. The method used for this analysis is ABAQUS 6-13 software. On bipolar model, the 3000 N load is applied in the FEM model. The crosslink dose used in this analysis was 50kgy, 75kgy, and 100kgy. The results obtained are that UHMWPE that has received by gamma irradiation treatment can receive a smaller stress distribution. The results of the simulation for UHMWPE without irradiation produced 0.759 stress distributions; 50kgy crosslink dose has 0.666 stress distributions; 75kgy crosslink dose has 0.662 stress distributions; and 100kgy crosslink dose has 0.660 stress distributions. This result proved that UHMWPE which has received crosslink can receive a better stress distribution. For the result crosslink with 100kgy dose received the best number of stress distributionss.

A lot of Hip Joint Simulator have been made nowadays, most of them use different structure and method. This research reports a pin-on-ring tribometer design that is used to became hip joint simulator based on the movement of the salat (salat gait). Modified femoral head and acetabular cup holder are performed, to design a reciprocating motion for simulation of artificial hip movement. An interesting finding from this study is a new linked-bar mechanism that leads to the ability to move femoral head against the acetabular cup and measure wear volume of an THR patients during normal salat gait. The designed motion angle is 121.5° in the flexion direction and 15.5° in the direction of abduction. Linked bar for sensor dial indicator have enough adjustment, but there is still a movement that is not rigid upon running hip joint process simulator. This research concentrates on the bar is already linked in accordance or not when compared with the data in the simulate on a computer. Estimation error and deviations that occur between numerical and experimental is going forward to improve hip joint simulator Undip to be more precise and relevant research to use THR Undip.

Decision making a concept the optimal inside a concept engineering design (CED) is a job repeated. Decision matrix based method is the most popular concept selection approach used in engineering design. A matrix is an array that presents an axis of the alternate list being evaluated. The list of weighted criteria depends upon the importance of each of the final decisions to be taken. The decision matrix in this determined some weights and the rank as attributes to evaluate a total scores. Upon the weighting sometimes make the designer confusedly in determine variety. This paper described a decision making computer based, where a logic matrix decisions on a basis in the selection and evaluation. This model presents a logical procedure for concept evaluation considering the specified attribute. In decision-making this model is integrated and intended to improve the ability of beginners in designing.

In this paper, an investigation of hydrodynamic performance for journal bearing lubricated by thin film is performed by three-dimensional CFD (computational fluid dynamic). Two regimes, i.e. laminar and turbulent regimes are of main interest. The sliding velocity was varied from 3000, 5000 and 10000. The numerical simulation shows that the velocity magnitude of the journal has a strong effect on the hydrodynamic pressure. In addition, it is found that an appropriate modelling of flow regime affects the predicted lubrication performance. From the overall analysis, both using laminar and turbulent regimes, the distribution of static hydrodynamic pressure shows a similar trend. It is also found that at the beginning of the contact, the static pressure is low, and then, it gradually increases to the highest point, and finally drops significantly.

This paper analyzes the contact area of the contact between a deformable rough surface (smooth and rough) and a hard smooth sphere indenter using finite element method. A method was introduced to generate a three dimensional rough surfaces using Computer Aided Design (CAD) software. The rough surface model was developed based on the surface measurement data, while the smooth surface model was generated from the CAD software. Contact area and contact deformation were analyzed. Results showed that the contact area between rough surface versus sphere and smooth surface versus sphere is different.

Carbonate scale is a common problem found in a piping system of industrial process. The presence of mechanical equipment such as turbine, compressor, blower, mixer and extruder produce a mechanical vibration on the piping system which is placed near these equipments. The influence of vibration on the CaCO3 scale formation in the piping system was experimentally investigated in the present study. The aim of the research was to understand the effect of vibration on the kinetics, deposition rates and the crystals formation in the synthetic solution. The solution was prepared using CaCl2 and Na2CO3 for concentration of calcium of 3.500 ppm, while the induction time, deposition rate, crystal growth were investigated at temperature of 25°C. In generating the vibration force, the mechanical equipment consisting of electrical motor, crankshaft, connecting rod and a vibration table were employed, including four coupons inside the pipe for investigating the scale formed. Frequency of the vibration was set at 0.00, 1.00 Hz and 2.00 Hz, respectively. A dosing pump with two inlets and two outlets was used to circulate the solutions at flowrate of 30 ml/min from each vessel to the coupons. After running for three hours, the induction time was recorded at 17; 10 and 8 minute with vibration frequency of 0.00; 1.00 and 2.00 Hz, respectively. The scale formed was then characterized using SEM/EDX for crystal morphology and elemental analysis. The results show that the deposition rates were 0.9457 and 3.3441 gram/h for the frequency of 1.00 and 2.00 Hz. The carbonate crystals found in coupon and filter were vaterite.

Struvite (NH4MgPO4•6H2O) is a mineral often found as a scale deposit in an industrial process and piping. The common occurrence of struvite formation is a wide variety of environments. pH solution and environmental temperature are important parameters that control precipitation and subsequent decomposition of struvite. The study aims to characterise the struvite precipitated out the solution through chemical and mineralogical analysis. In this work, struvite solution was prepared by mixing NH4OH , MgCl2 and H3PO4 with the different purity grade (A and B) in the mol ratio of 1 : 1 : 1 in the stirred glass vessel tank with volume of 500 ml, and then stirred at 200 rpm for 70 minutes. Temperature of 3°C and an initial pH of 10 were selected. The precipitated deposit was dried at room temperature for 48 hours of being analyzed. Material characterization of the deposits was conducted using XRPD Rietveld method of qualitative and quantitative mineralogical phase analysis. XRF was employed for bulk chemical elemental analysis of the scale obtained. The sample A using analytical grade powder provided the major phases of struvite-(K) and struvite. In constrast, the major phase of newberyite and minor phases of lepidocrocite (FeOOH) and niter (KNO3) was observed by following changes in the lowest purity of powder (Sample B). Analysis of the experimental data suggests a solution mediated transformation process as a possible mechanism of struvite transformation.

Crystallization of struvite [MgNH4PO4.6H2O] may lead to the deposition of scale which may create significant problems in the process pipes, pumps and other industrial equipment. However, struvite precipitation can be benefited for phosphate recovery for use of fertilizer. The aim at the present work was to investigate calcium additive on struvite precipitation. The experiment was carried out in a batch mode using a 1-liter Pyrex glass vessel mechanically agitated for 200 rpm. The scale-forming solution was prepared for mixing solutions to MgCl2 and NH4H2PO4 with Mg+2 , NH4+ and PO4-3 in a molar ratio of 1: 1:1. The crystallization temperature of 30 and 40 °C was selected. Ca was added into the crystallizing solution to chloride dihydrate 0.4M (CaCl2•2H2O). Then each solution was pH adjusted to 9 by addition of KOH. The crystals obtained were characterized using SEM for morphology, EDS for elemental analysis as well as XRPD Rietveld analysis for crystaline phases. The induction periods varied from 10 to 90 min, which means that the struvite crystals began forming 10 to 90 min after mixing of the solution. It was observed that the Ca additive may inhibit the struvite crystallization. SEM analysis revealed that the struvite crystals obtained were predominantly of irregular prismatic morphology. Furthermore, the EDS pattern revealed that the elemental composition of the crystals consisted of Ca, Cl, S Mg, N, and P, providing that many crystalline phase found in the crystals such as Gypsum, CaCl2, struvite, struvite-(K) and sylvite. It was observed that the Ca additive appeared to inhibit the struvite crystallization.

Struvite (MgNH4PO4.6H2O) is one of phosphate minerals, commonly forms into aqueous solutions. It can be precipitated as mineral deposits for optimization of phosphate recovery based on the pH optimum, molar ratio and temperature levels. This paper presents results of a study on the struvite precipitation under the influence of pH variation, at optimized molar ratio and temperature, which were calculated from an experimental design methodology. Based on the methodology, a laboratory prepared struvite, made by mixing solutions to NH4OH, MgCl2 and H3PO4 for a molar ratio of 1: 2: 1 in a 500 mL volume of batch stirred crystallizer at room temperature. The crystallization was done at 200 rpm and the pH variation was adjusted to 8, 9 and 10 with KOH for a time of 70 minutes. The resulting crystals were filtered and dried at room temperature for 48 h and subsequently stored for further analysis. Material characterisasion of the crystals was conducted using XRPD Rietveld method of mineralogical composition. SEM equipped by EDX was employed for investigation of morphology and elemental composition of the crystals obtained. During the experiment, struvite crystals were firstly nucleated and subsequently developed at major value. The increase in pH is assumed to convert some of the struvite phase into struvite (K) and minor sylvite (KCl). It demonstrates that Visual MINTEQ can be employed to estimate the mineral formation out the synthetic solutions.

In this paper, a theoretical and experimental investigation is presented to study the contact behavior of the plastic contact of deterministic rough surfaces. Analyses exclude bulk deformation of the rough surface and concentrate to the contact on asperity level. Surface asperities are modeled by an array of elliptic paraboloids where the unit event of a single contact is analyzed using an elastic-plastic elliptical contact model. A new method to determine the surface topography change due to plastic deformation is presented. Results show that the theoretical model developed predicts the contact area and the deformed geometry of the rough surface very well. [DOI: 10.1115/1.2768618] Keywords: contact mechanics, plastic deformation, deterministic contact, rough surface, asperity