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This work presents a thermodynamic evaluation of an operating geothermal ORC power plant. The model is realized by using measured data of AFJET geothermal power plant which has 3MWe net power output capacity. Thermodynamic assessment of the system is conducted to see the energy and exergy efficiencies of each component, and the whole plant. Additionally, a parametric study is conducted to understand the effects of various operating conditions on the system performance. Different from previous studies, daily and annual net power output profile of the plant was investigated with considering ambient temperature fluctuations. Results revealed that net power output can drop as significant as 36% from winter to summer months. Also, between nighttime to daytime, the net power expectation may decrease by 5%. The exergy destruction rate of re-injection process constitutes the most significant part (38.1%) of the total exergy destruction of the plant. The conversion and exergy efficiencies of the system are calculated as 11.24% and 39.03%, respectively. Also, to enhance the performance of the plant, an internal heat recovery system is recommended. The analyses show that the implementation of an internal heat recovery system improves the energy and exergy efficiencies of the plant by 15%.

This paper introduces a new hybrid optimization algorithm (HWOANM) based on the Nelder-Mead local search algorithm (NM) and whale optimization algorithm (WOA). The aim of hybridization is to accelerate global convergence speed of the whale algorithm for solving manufacturing optimization problems. The main objective of our study on hybridization is to accelerate the global convergence rate of the whale algorithm to solve production optimization problems. This paper is the first research study of both the whale algorithm and HWOANM for the optimization of processing parameters in manufacturing processes. The HWOANM is evaluated using the well-known benchmark problems such as cantilever beam problem, welded beam problem, and three-bar truss problem. Finally, a grinding manufacturing optimization problem is solved to investigate the performance of the HWOANM. The results of the HWOANM for both the design and manufacturing problems solved in this paper are compared with other optimization algorithms presented in the literature such as the ant colony algorithm, genetic algorithm, scatter search algorithm, differential evolution algorithm, particle swarm optimization algorithm, simulated annealing algorithm, artificial bee colony algorithm, improved differential evolution algorithm, harmony search algorithm, hybrid particle swarm algorithm, teaching-learning-based optimization algorithm, cuckoo search algorithm, grasshopper optimization algorithm, salp swarm optimization algorithm, mine blast algorithm, gravitational search algorithm, ant lion optimizer, multi-verse optimizer, whale optimization algorithm, and the Harris hawks optimization algorithm. The results show that the HWOANM provides better exploration and exploitation properties, and can be considered as a promising new algorithm for optimizing both design and manufacturing optimization problems.

Gears are one of the most important power transmission elements in every area of the industry. Because of its importance, the gear design must be carefully performed. Unfortunately, due to the changing of the boundary conditions, gears are exposed to failures such as cracks, pitting, tooth missing etc. during the operation. Thus the gear diagnostic and monitoring become a very critical phenomenon for the gearboxes. A dynamic transmission error (DTE) based numerical fault detection model is proposed. Firstly, numerical finite element model is created to calculate single tooth stiffness with different crack levels. Furthermore, the model is used for the asymmetric gear profile which has a great importance nowadays for different areas. After that, the time-varying mesh stiffness is calculated by using single tooth stiffness with different crack levels for both symmetric and asymmetric types of the gears. To understand the effects of the gear cracks along the tooth thickness on dynamic transmission error of the gear system and to detect the gear crack faults for symmetric and asymmetric gear profiles, a four-degree of freedom dynamic model is created. The results show that with the increment of the crack level, the mesh stiffness of the gears is decreased.

Gear dynamics is one of the most critical subjects in gear design because of its remarkable effect on vibration levels, load-carrying capacity, and noise. The tip relief modification is known as a simple method to decrease dynamic loads in the industry. The primary goal of this study is to understand the influence of tip relief modification on the dynamic performance of the spurs gears. In this paper, the meshing process and gear mesh stiffness calculation method are defined. A dynamic model with two- degree-of-freedom is created to find the dynamic response of the spur gear pair. The simulations are carried out with standard and different tip modified spur gear pairs. It is observed that the tip relief modification has an excellent effect on the gear dynamic response. However, this effect is restricted until a certain amount of tip relief modification. After the optimum amount of tip relief modification, the dynamic loads are increased considerably. Thus, a computer program is developed to find the optimum amount of tip relief modification in MATLAB® for the gear designers. The program outputs are given for two different case studies. As a result of the study, the dynamic factor behaves like a “V form” according to the tip relief modification, and the dynamic force decreased approximately 25% for optimum profile modification. Dişli dinamiği; titreşim seviyeleri, yük taşıma kapasitesi ve gürültü üzerindeki dikkat çekici etkileri sebebi ile dişli çark tasarımındaki en kritik unsurlardan bir tanesidir. Dişli çark uç modifikasyonu endüstride dişli çarklar üzerindeki dinamik kuvvetleri azaltmak için kullanılan bir yöntem olarak bilinmektedir. Bu çalışmanın amacı; dişli uç modifikasyonunun düz dişli çarkların dinamik performansı üzerindeki etkilerinin anlaşılmasıdır. Bu kapsamda, düz dişli çarkların kavrama sürecine ve kavrama rijitliğinin hesaplamasına yönelik bir yöntem tanımlanmıştır. Dişli çark çiftinin dinamik cevabının bulunması için iki serbestlik dereceli bir dinamik model geliştirilmiştir. Dişli uç modifikasyonun dişli çarkların dinamik performansı üzerindeki etkilerinin incelenmesi için nümerik simülasyonlar hem standart hem de uç modifikasyonu uygulanmış dişli çark çiftleri için gerçekleştirilmiştir. Uç modifikasyonu uygulamasının dişli çarkların dinamik cevabı üzerinde mükemmel bir etkisi olduğu tespit edilmiştir. Ancak, belirtilen bu pozitif etkinin de belirli bir optimum değer ile sınırlı olduğu görülmüştür. Optimum dişli uç modifikasyonu miktarı aşıldıktan sonra dişli çark üzerindeki dinamik yükler ciddi bir şekilde artmaktadır. Bu çalışmada, MATLAB® ortamında dişli çark tasarımcılarının optimum uç modifikasyonu miktarını hesaplamasına olanak sağlayacak bir bilgisayar programı geliştirilmiştir. Program çıktıları iki farklı vaka çalışması için değerlendirilerek sunulmuştur. Sonuç olarak, dinamik faktörün profil modifikasyonu ile birlikte V formda değiştiği ve optimum modifikasyon değerinde yaklaşık olarak %25 azaldığı tespit edilmiştir.

WOS:000543104900020 This paper investigates the factors affecting the optimum insulation thickness and its pay-back period, such as heating and cooling energy requirements of building, lifetime, present worth factor, costs of insulation material and installation, costs of energy sources for heating and cooling, heating and cooling system efficiencies, and solar radiation. For this purpose, by considering two cities characterizing the hot and cold climatic conditions, the optimum insulation thickness and its payback period have been calculated and a detailed parametric analysis has been carried out. To achieve practical results, the ranges of the parameters considered in the study include the values typically reported in the literature. The variations in the optimum insulation thickness and the pay-back period with all parameters are presented in graphical form. Finally, order of importance and contribution ratios of the examined parameters on the optimum insulation thickness are determined with the help of Taguchi method. It is found that heating degree-days is the most efficient parameter on the optimum insulation thickness with an impact ratio of 27.33% of the total effect while the least efficient parameter is the efficiency of heating system with an impact ratio of 3.21%.

In recent years, there has been a great deal of interest in lightweight vehicle design due to regulations about reducing fuel consumption and emissions. Lightweight design of vehicle components is one of the most important research topics in vehicle design. Developing the optimum structure in the early stages of design process is very important for minimizing the vehicle weight and production costs. In this paper, an automobile hinge component has been developed using PA66 GF60 glass fiber-reinforced polyamide composite materials instead of conventional steel. The automobile hinge component has been conceived using computer aided design software. Topology optimization was made under specific loadings subject to the constraints of finite element method analysis. As a result of this study, optimum dimensions of the component have been obtained and the weight of the component has been reduced via structural topology optimization techniques while satisfying displacement and stress conditions. The results show that composite materials are an important alterative in lightweight vehicle design.

In this paper, an evaluation of the static and dynamic behavior of bimetallic spur gears with different gear parameters is performed numerically. Bimetallic lightweight spur gears working without a decrease in the performance of the gear mechanisms have many potential benefits in automotive and aerospace applications. A bimetallic spur gear consists of two metals which are steel on the gear teeth and aluminum on the hub region. The dynamic performance of these gears is evaluated by using a two degree of freedom (2-DOF) dynamic model. The finite element method is used to calculate maximum root stress for varying ring thicknesses and other gear parameters for gears with symmetric and asymmetric teeth. These stress values and the weight reduction ratios are taken into consideration to optimize the ring thickness. Tooth deflection is also calculated to determine tooth stiffness by finite element analysis (FEA). Dynamic simulations are carried out to investigate the effects of gear parameters on the dynamic force and static transmission error (STE). Sample simulation results are illustrated with numerical examples. The results indicate that, if properly designed, bimetallic gears can provide a high potential to reduce the weight in power transmission systems without adverse effects on stress and dynamic behavior. (C) 2019 Elsevier Ltd. All rights reserved.

There are various factors having an impact on the energetic and exergetic performance (i.e., COP and eCOP) of an absorption refrigeration systems (ARS) such as the temperatures of the generator, condenser, evaporator and absorber, effectiveness of solution, refrigerant and solution-refrigerant heat exchangers and isentropic efficiency of the solution pump. Many studies have focused on these process parameters, but the importance order and contribution ratios of the parameters due to thermodynamic performance have not been determined by using statistical methods. Firstly, in this study, cycles’ thermodynamic model is established and the variation of the COP and eCOP are calculated for different working conditions with different parameters ranges. The effects of these parameters on the COP and eCOP are examined separately on a statistical basis. The importance order of the parameters are determined by using Taguchi and ANOVA methods and the results are compared. Optimum operating conditions are determined by means of statistical analysis for the COP and eCOP. Under these operating conditions, the COP and eCOP of the system are calculated as 0.697 and 0.2829, respectively. Furthermore, for the simultaneous maximization of these two performance indicators, Taguchi-Grey Relational Analysis (GRA) is used. By using this analysis, importance order of the examined parameters on multiple performance characteristics are determined. The absorber and evaporator temperatures are the most efficient parameters on multiple performance characteristics with a contribution ratio of 29.66% and 26.34% of the total effect while the least efficient parameters are the pump efficiency and effectiveness of solution-refrigerant heat exchanger with a contribution ratio of 0.48% and 2.41%, respectively. For the best condition considering the multiple performance characteristics, COP and eCOP of the system are found as 0.6255 and 0.2829, respectively.

In the present study, the fatigue behaviour of a clutch diaphragm spring is investigated experimentally and numerically. Differential evolution optimisation algorithm and response surface methodology are used to define optimal variables of the diaphragm springs under constraints both minimum stress and required clamp load. The required clamp load is checked by the chi-square theorem vs. to target clamp load curve. Ten design variables are considered for creating a design of experiment with two steps, including finger shape optimisation with eight variables, load, and stress optimisation with two variables as the aim of maximum fatigue definition. One hundred seventy-five different designs are analysed numerically. As a result of the optimisation study, the optimum design is provided an endless lifetime subject to the required load, minimum stress, and minimum weight. The optimum design is manufactured and tested experimentally. Valeo

In this paper, nine recent meta-heuristics have been employed to search for optimal design of an automatic planetary gear train. The function of the designed system is to automatically transmit power and motion in automobiles. Nine mixed decision parameters are considered in the optimisation procedure. The geometric conditions such as the undercutting, the maximum overall diameter of the transmission, as well as the spacing of multiple planets are taken into account to ensure an optimum design. All the above algorithms are tested both quantitatively and qualitatively for solution quality, robustness, and their time complexity is determined. Results obtained illustrate that the utilised approaches can effectively solve the planetary gearbox problem. Besides this, the comparative study indicates that roulette wheel selection-elitist differential evolution (ReDE) outperforms the other algorithms in terms of the statistical results, and FA has the best convergence behaviour. Meanwhile, multi-verse optimisation (MVO) and butterfly optimisation algorithm (BOA) performed better than the other used algorithms when computation time was considered. King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia

Continuously variable transmissions (CVT) have been widely used in many different areas such as automotive, robotics, manufacturing and aerospace industry. In CVT drives, a properly designed control strategy is needed to ensure the precise control of the speed ratio, and a deep knowledge of the steady-state and transient behavior of the drive is necessary to this purpose. In the framework of belt and chain CVT drives, model-based approaches developed for this purpose are mainly of two types: continuous models and multibody models. Continuous models are much less costly from a computation point of view, while multibody models are usually believed to be more accurate. The aim of this paper is twofold: first the CMM continuum model [Carbone G., Mangialardi L., Mantriota G., ASME Journal of Mechanical Design, 127, 103-113 (2005)] is compared with a multibody model of the chain-CVT variator. Secondly, the CMM model is proposed for a fast and enhanced characterization of the shifting dynamics of chain CVT. The analysis shows that, except for dynamical effects due to the intermittent contact of the chain pins with the pulleys and caused by the polygonal action of the chain, the CMM and multibody models provide very similar results. Moreover, this study shows, by exploiting the CMM model, that the overall dynamics of the CVT can be described by a relatively simple first order nonlinear differential equation, which can be very easily implemented for CVT real-time control applications. The accuracy of such a simplified approach is then tested against some preliminary shifting experiments under torque load conditions. Results show a very good agreement between theoretical predictions and experimental outcomes, thus making this simplified approach a promising tool to develop advanced real-time control of CVT transmissions for automotive applications. (C) 2016 Elsevier Ltd. All rights reserved.

We present a systematic numerical study on temperature dependent fracture mode change in small punch tests. Following Needleman and Tvergaard (2000), we model the material as thermo-inelastic, where the ductile fracture mode, by void nucleation, growth and coalescence is accounted for by Gurson׳s porous metal plasticity (Gurson, 1977). The brittle fracture mode by cleavage is accounted for by Ritchie–Knott–Rice׳s deterministic maximum principal stress criterion (Ritchie et al., 1973). The well-known problem of mesh dependence associated with softening material behavior is remedied by using an integral type nonlocal formulation similar to that presented in Tvergaard and Needleman (1995). Two length scales are incorporated into the constitutive relations: the ductile fracture length scale is based on the average inclusion distance and associated with the nonlocal evolution equation for the porosity. The brittle fracture length scale is based on the average grain size and associated with the material region at which the maximum principal stress is averaged out. The material model is used to simulate small punch tests at View the MathML source−196°C, View the MathML source−158°C and View the MathML source25°C of notched and unnotched specimens of P91 steel representative for small- and large-scale yielding conditions, respectively. The simulated fracture modes and patterns show a very good agreement with experiments: for View the MathML source−196°C brittle fracture propagating normal to the maximum (tensile) principal stress prevails. For View the MathML source25°C ductile fracture is governed by shear localization with voidage. The simulations also show that the deformation energy is considerably higher for the upper shelf tests compared to the lower shelf tests.

In metal cutting, the magnitude of the temperature at the tool-chip interface is a function of the cutting parameters. This temperature directly affects production, therefore, increased research on the role of cutting temperatures can lead to improved machining operations. In this study, tool temperature was estimated by simultaneous temperature measurement employing both a K-type thermocouple and an infrared radiation (IR) pyrometer to measure the tool-chip interface temperature. Due to the complexity of the machining processes, the integration of different measuring techniques was necessary in order to obtain consistent temperature data. The thermal analysis results were compared via the ANSYS finite element method. Experiments were carried out in dry machining using workpiece material of AISI 4140 alloy steel that was heat treated by an induction process to a hardness of 50 HRC. A PVD TiAlN-TiN-coated WNVG 080404-IC907 carbide insert was used during the turning process. The results showed that with increasing cutting speed, feed rate and depth of cut, the tool temperature increased, the cutting speed was found to be the most effective parameter in assessing the temperature rise. The heat distribution of the cutting tool, tool-chip interface and workpiece provided effective and useful data for the optimization of selected cutting parameters during orthogonal machining.

The continuously variable transmission (CVT) system represents one of the best solutions to minimize the fuel consumption for vehicles that are driven by an internal combustion engine or an electrical motor. Hence, the theoretical analysis of a chain CVT is crucial in the optimization of the design and control strategy. This paper is concerned with the transient dynamics of a chain CVT with a speed ratio controller adopted from the Carbone-Mangialardi-Mantriota model and its experimental verification. To this end, a theoretical model is developed with a PI speed ratio controller, considering the momentary solution of a first order differential equation governing the shifting speed, which represents the whole dynamics of the CVT. To verify the developed model, the experiments are carried out on a chain CVT test rig. It is observed that the numerical and experimental results are in good agreement, which implies that the developed model embedded in a speed ratio controller is appropriate to predict the shifting dynamics of the chain CVT. Afterwards, the developed model is used to design the appropriate PI gains by numerical experiments in order to obtain the same slope of the time response of speed ratio for different input angular velocities. Therefore, the same shifting speed can be secured for the different working conditions in this manner. This paper contains very important results for manufacturers about the control parameter and gain effect on the shifting dynamics of chain CVT, and the developed model can be used for different control algorithms in automotive applications. Brezstopenjski menjalniki (CVT) so ena najboljših rešitev za zmanjšanje porabe goriva pri vozilih, ki jih poganja motor z notranjim zgorevanjem ali elektromotor. Teoretična analiza verižnih menjalnikov CVT je zato ključna za izbiro optimalne konstrukcije in strategije regulacije. Članek obravnava prehodno dinamiko verižnega menjalnika CVT z regulatorjem razmerja hitrosti po modelu Carbone-Mangialardi-Mantriota in eksperimentalno potrditev. Razvit je bil teoretični model s PI-regulatorjem razmerja hitrosti na podlagi trenutne rešitve vodilne diferencialne enačbe prvega reda za hitrost prestavljanja, ki predstavlja celotno dinamiko sistema CVT. Razviti model za regulacijo razmerja hitrosti je bil preverjen v več eksperimentih pri različnih začetnih pogojih razmerja hitrosti, kot je prikazano na slikah. Meritve so bile opravljene na preizkuševališču za verižne menjalnike CVT. Vhodno moč zagotavlja trifazni asinhronski 4-polni motor Siemens z močjo 30 kW, kotno hitrost motorja nadzoruje inverter, zavorni moment pa daje elektromagnetna zavora, ki je povezana z izhodno jermenico menjalnika CVT. Potrebni podatki so bili zabeleženi s pomočjo zaznaval tlaka, navora in odmika. Rezultati numerične in eksperimentalne analize pritezne sile v stacionarnem stanju se dobro ujemajo pri razmerju hitrosti 1. Rezultati za stacionarno stanje, pridobljeni iz teoretičnega modela, so bili nato shranjeni v tabelo za uporabo v simulacijah. Model regulacije razmerja hitrosti je bil eksperimentalno preverjen v prehodnih pogojih za različne začetne pogoje. Rezultati eksperimentov tudi v tem primeru izkazujejo dobro ujemanje, iz česar sledi sklep, da je razviti model, ki je vdelan v regulator razmerja hitrosti, primeren za napovedovanje dinamike prestavljanja verižnega menjalnika CVT. Razviti in potrjeni teoretični model je bil nato uporabljen v numerični analizi za izbiro ustreznih vrednosti členov PI-regulatorja in doseganje enakega naklona časovnega odgovora razmerja hitrosti pri različnih vhodnih kotnih hitrostih. Z drugimi besedami % parametri PI-regulatorja so bili numerično določeni za enak časovni odziv pri različnih vhodnih hitrostih. V numerični analizi je bil integralni člen Ti konstanten, proporcionalni člen Kp spremenljiv, čas umiritve razmerja hitrosti pa je bil določen za primer brez prevzpona. Enak postopek je bil uporabljen za povečanje integralnega člena pri določenih proporcionalnih členih, vsi podatki pa so bili zabeleženi v matriko. Isti izračuni so bili opravljeni za različne vhodne hitrosti, pri čemer so bile pridobljene podobne matrike. Točke minimuma na teh površinah matrik določajo najboljše člene PI z ozirom na čas umiritve brez prevzpona. Na ta način je bil določen nabor členov PI-regulatorja za različne vhodne kotne hitrosti menjalnika CVT. Kriterij za določitev časa umiritve je razlika med želenim in trenutnim razmerjem hitrosti, ki ne presega 0,001. Rezultati, predstavljeni v tem članku, bodo zelo pomembni za proizvajalce in inženirje pri izbiri ustreznih parametrov PI-regulatorja za želeno dinamiko prestavljanja verižnih menjalnikov CVT. Razviti model je mogoče uporabiti v različnih regulacijskih algoritmih v avtomobilski industriji.

This work proposes a multi-surrogate-assisted optimisation and performance investigation of several newly developed metaheuristics (MHs) for the optimisation of vehicle crashworthiness. The optimisation problem for car crashworthiness is posed to find the shape and size of a crash box while the objective function is to maximise the total energy absorption subject to a mass constraint. Two main numerical experiments are conducted. Firstly, the performance of different surrogate models along with the proposed multi-surrogate model is investigated. Secondly, several MHs are applied to tackle the proposed crashworthiness optimisation problem by employing the best obtained surrogate model. The results reveal that the proposed multi-surrogate model is the best performer. Among the several MHs used in this study, sine cosine algorithm is the best algorithm for the proposed multi-surrogate model. Based on this study, the application of the proposed multi-surrogate model is better than using one particular traditional surrogate model, especially for constrained optimisation. Thailand Research Fund (TRF)

This paper introduces a new adaptive mixed differential evolution (NAMDE) algorithm for mechanical design optimisation problems. The algorithm uses a self-adaptive mechanism to update the values of mutation and crossover factors. Moreover, elitism is used where the best-found individual in each generation is retained. The performance of NAMDE is evaluated by solving 11 well-known constrained mechanical design problems and two industrial applications. Further, comparison results between NAMDE and other recently published methods, for the first problems, clearly illustrate that the proposed approach is an important alternative to solve current real-world optimisation problems. Besides this, new optimal solutions for some engineering problems are obtained and reported in this paper. For the coupling with a bolted rim problem, the objective function improved by 10%. Whereas for the spur minimisation problem, the final design provides a reduction in gearing mass by 7.5% compared to those published in previous works.

In this contribution, performances of well-known population based algorithms, the artificial bee colony (ABC), contemporary particle swarm optimization (CPSO), genetic algorithm (GA), and differential evolution (DE) are compared in a basic model for damage identification (DI). DI is modeled as an inverse problem with the objective function based on the difference of the frequency response functions (FRF) computed by the finite element model of the structure and the reference data measured from damaged structure. Damage parameters are determined solving the problem with the aforementioned algorithms. It was observed that DE is the best one of a given number of function evaluations and gives the most accurate results in spite of noise interference to the reference data. According to the relevant literature, this is the first study including a comparison of these algorithms in an FRF based DI study.

The life of a tool is affected by many factors such as cutting speed, depth of cut, chip thickness, tool geometry, workpiece material, cutting fluid and the rigidity of the machine tool. This paper introduces the innovative turning strategy of variable feed turning. The workpiece material was AISI 1050, and two types of TiN-coated insert (CNMG-120408 (NC3020) and DNMG 150608-NM4 WPP20) were used as cutting tools in the machining tests. A thorough investigation was carried out on the effect on tool life of a gradual feed rate at a constant depth of cut and cutting speed with no cooling fluid. The feed rate was gradually increased twice every millimetre at the beginning of turning and kept constant for the rest of the cut. Turning experiments were conducted with both constant and variable feed rates. Brand new inserts were deployed in the experiments related with constant feed rate for each time period. Comparisons showed the significant influence of the variable feed rate. Apart from the reduction in initial wear, the new turning strategy produced very positive results regarding tool wear in the moderate wear zone, and a considerable increase of 32 % in tool life was achieved. Moreover, with the new strategy, total tool life was prolonged by up to 35 %. Balıkesir Üniversitesi Bilimsel Araştırma Projesi Birimi - 2012/101

This paper presents a methodology for re-designing a failed tractor transmission component subjected to cyclic loading. Unlike other vehicles, tractors cope with tough working conditions. Thus, it is necessary to re-design components by using modern optimization techniques. To extend their service life, we present a design methodology for a failed tractor clutch power take-off finger. The finger was completely re-designed using topology and shape optimization approach. Stress-life based fatigue analyses were performed. Shape optimization and response surface methodology were conducted to obtain optimum dimensions of the finger. Two design parameters were selected for the design of experiment method and 15 cases were analyzed. By using design of the experiment method, three responses were obtained: Maximum stresses, mass, and displacement depending on the selected the design parameters. After solving the optimization problem, we achieved a maximum stress and mass reduction of 14% and 6%, respectively. The stiffness was improved up to 31.6% compared to the initial design. Türkiye Teknoloji ve Bilim Bakanlığı- 0456-2013-2 Türkiye VALEO Şirketi

Bu çalışma, 26–27 Mayıs 2014 tarihlerinde Bursa[Türkiye]’düzenlenen Otomotiv Teknolojileri Kongresi‘nde bildiri olarak sunulmuştur. The main functions of a rubber bushing are to join the rigid elements in the vehicles and isolate vibration and noise. Owing to the increasing interest of multi-body simulations of vehicles, it is important to develop validated models to calculate the static stiffness. Mechanical behaviour of rubber products depends on many parameters, therefore their modelling is quite complex. In this study, a hyperelastic finite element model of rubber bushing was developed, analysed and compared with test results. Optimum design parameters of bushing model were determined by shape optimisation using differential evolution algorithm.

Bu çalışma, 26–27 Mayıs 2014 tarihlerinde Bursa[Türkiye]’da düzenlenen Yedinci Otomotiv Teknolojileri Konferansı – OTEKON’2014 Kongresi‘nde bildiri olarak sunulmuştur. Hot stamping is an alternative production method for forming of ultra-high strength sheet metals. It consists of heating the sheet metal and directly transfers to the die through the forming and cooling steps. Today, there is an increasing trend to use the hot stamping process to manufacture vehicle parts owing to body structure regarding vehicle safety and emission requirements. The aim of this study is to present a numerical simulation approach, which is FE-based die design for hot stamping with a thermo-mechanical-metallurgical coupled model. The results and validity of this approach are illustrated through an industrial application for an automotive part. The results are also evaluated by considering hot stamping applications research in literature, and 2D and 3D results show a good agreement with results known from literature. Türkiye Bilim, Sanayi ve Teknoloji Bakanlığı Beyçelik-GESTAMP, Bursa, Turkiye - SANTEZ 01529.STZ.2012-2

Today's robots are able to perform very limited locomotion tasks by consuming high energy although animals are able to carry out very complicated but stable locomotion tasks using less control inputs and energy. Therefore, it is important to understand the principles of animal locomotion in order to develop efficient legged robots. This paper presents a U-shape visco-elastic beam mechanism that is able to run like a bounding animal when it is actuated by a simple pendulum at the torsional resonance frequency of the elastic body. A simple physical model has been developed to investigate the dynamics of the mechanism and the natural body dynamics of quadrupeds. In the mechanism, a small rotating mass was attached to a DC motor which was mounted on the center of the spine. When this motor is actuated at around the torsional resonance frequency of the elastic body, the robot starts to move and it exhibits a self-organized locomotion behavior. The self-organized locomotion process of the robot does not require any central authority, sensory feedback or external element imposing a planned motion. Comparing the bounding locomotion of the beam mechanism with those of well-known quadrupeds such as a horse, greyhound and cheetah, it can be concluded that the pendulum-driven U-shaped visco-elastic beam displays kinematic behavior similar to a horse, in terms of both experimental and simulation results. Interestingly, this bounding locomotion occurs only if the shape ratio and the actuation frequencies of the beam are close to those of the fastest quadrupeds. Swiss National Science Foundation (SNSF) - European Commission

The effective thermal conductivity (ETC) of multilayer thermal insulation materials was experimentally investigated as a function of temperature (0-25 A degrees C). The materials consisted of binary/ternary glass wools or ternary expanded polystyrene foams reinforced with aluminium foil. The experimental measurements were performed using a guarded hot plate with temperature differences of 5, 10 and 15 A degrees C. The results indicated that significant correlations exist between ETC and the characteristics of the materials with decreasing temperature. The ETC decreases with reinforcement with aluminium foil at the same temperature or with temperature differences of 5 and 15 A degrees C. In addition, it was clearly observed that the ETC decreases sharply with decreased temperature. Consequently, reflective materials may reduce the ETC at low temperatures.

Numerous studies have estimated the optimum thickness of thermal insulation materials used in building walls for different climate conditions. The economic parameters (inflation rate, discount rate, lifetime and energy costs), the heating/cooling loads of the building, the wall structure and the properties of the insulation material all affect the optimum insulation thickness. This study focused on the investigation of these parameters that affect the optimum thermal insulation thickness for building walls. To determine the optimum thickness and payback period, an economic model based on life-cycle cost analysis was used. As a result, the optimum thermal insulation thickness increased with increasing the heating and cooling energy requirements, the lifetime of the building, the inflation rate, energy costs and thermal conductivity of insulation. However, the thickness decreased with increasing the discount rate, the insulation material cost, the total wall resistance, the coefficient of performance ( COP ) of the cooling system and the solar radiation incident on a wall. In addition, the effects of these parameters on the total life-cycle cost, payback periods and energy savings were also investigated.

Determining the thermal conditions in an automobile and their effects on the driver is an important issue from both thermal comfort and driving safety points of view. Especially in hot summer season, the interior thermal conditions in automobile change rapidly when the air conditioning unit runs. In this study, standard air conditioning system is switched in an automobile parked in the sun and then the interior thermal conditions of the automobile are determined in detail during the 1-h cooling period. During the period, relative humidity, air velocity, air and surface temperature measurements are taken at numerous locations in the automobile. Moreover, in order to evaluate the effects of transient interior thermal conditions on the occupant, the skin temperatures of human body are measured at nine points. In addition to this, the thermal sensation of the human subject is also questioned during the cooling period. Subjective thermal comfort data is recorded using a questionnaire. The series of tests are conducted on two different automobiles, and the experimental results for both automobiles are presented and scrutinized. FIAT TOFAS Automobile Company

This paper presents a new hybrid optimization approach based on immune algorithm and hill climbing local search algorithm. The put-pose of the present research is to develop a new optimization approach for solving design and manufacturing optimization problems. This research is the first application of immune algorithm to the optimization of machining parameters in the literature. In order to evaluate the proposed optimization approach, single objective test problem, multi-objective 1-beam and machine-tool optimization problems taken from the literature are solved. Finally, the hybrid approach is applied to a case study for milling operations to show its effectiveness in machining operations. The results of the hybrid approach for the case Study are compared with those of genetic algorithm, the feasible direction method and handbook recommendation.

The response of a simply supported finite beam, which is subjected to viscous damping and carries a moving force by transforming singular moving force and singular damping force to distributed force field is investigated. This is done by transforming singular moving force and singular damping force to a continuously distributed force field by means of the property of Dirac delta distribution function. The uniform beam is simply supported,moving velocity V and moving load F are constants. The effect of moving loads on the damped beams was checked by Fourier sinus series approach. Some equations have been provided to satisfy the experiment. This method can be used in case of several damping and linear springs.

The focus of this research is on a hybrid method combining immune algorithm with a hill climbing local search algorithm for solving complex real-world optimization problems. The objective is to contribute to the development of more efficient optimization approaches with the help of immune algorithm and hill climbing algorithm. The hybrid algorithm combines the exploration speed of immune algorithm with the powerful ability to avoid being trapped in local minimum of hill climbing. This hybridization results in a solution that leads to better parameter values. This research is the first application of immune algorithm to the optimization of machining parameters in turning and also shape design optimization problems in the literature. The results of single-objective benchmark problem, multi-objective disc-brake problem, an automobile shape design optimization problem taken from the literature and case studies for multi-pass turning operation have demonstrated the superiority of the proposed hybrid over the other techniques in terms of solution quality and convergence rates.

New gear designs are needed because of the increasing performance requirements, such as high load capacity, high endurance, low cost, long life, and high speed. In some applications, such as in wind turbines, the gears experience only uni-directional loading. In these instances, the geometry of the drive side does not have to be symmetric to the coast side. This allows for the designing of gears with asymmetric teeth. In previous studies related to bending stress and load capacity, high performance has been achieved for gears with asymmetric teeth. These gears provide flexibility to designers due to their non-standard design. If they are correctly designed, they can make important contributions to the improvement of designs in aerospace industry, automobile industry, and wind turbine industry. At high operation speeds, there is always a concern of dynamic loads and vibrations of equipment. Therefore, there is a need to fully understand the dynamic behavior of gears with asymmetric teeth. Thus, the primary objective of this paper is to use dynamic analysis to compare conventional spur gears with symmetric teeth and spur gears with asymmetric teeth. The secondary objective is to optimize the asymmetric tooth design in order to minimize dynamic loads. This study offers preliminary results to designers for understanding dynamic behavior of spur gears with asymmetric teeth. For this study, a dynamic model was developed, using MATLAB, and used for the prediction of the instantaneous dynamic loads of spur gears with symmetric and asymmetric teeth. Furthermore, a 2-D three-tooth model was developed for finite element analysis. Fast Fourier transform was used for the frequency analysis of the static transmission errors. It is shown that generally, the dynamic factor, for spur gears with asymmetric teeth, increases with increasing pressure angles on the drive side. For asymmetric teeth, increasing the addendum leads to a significant decrease in the dynamic factor. The static transmission error, at the center of the single tooth contact zone, decreases with increasing pressure angle. The first two harmonics slightly increase with increasing pressure angle. It is further shown that the amplitudes of harmonics of the static transmission errors are significantly reduced when asymmetric teeth with long addendum providing high gear contact ratio close to 2.0 are used.

This paper presents a novel optimization approach that is a new hybrid optimization approach based on the particle swarm optimization algorithm and receptor editing property of immune system. The aim of the present research is to develop a new optimization approach and then to apply it in the solution of optimization problems in both the design and manufacturing areas. A single-objective test problem, tension spring problem, pressure vessel design optimization problem taken from the literature and two case studies for multi-pass turning operations are solved by the proposed new hybrid approach to evaluate performance of the approach. The results obtained by the proposed approach for the case studies are compared with a hybrid genetic algorithm, scatter search algorithm, genetic algorithm, and integration of simulated annealing and Hooke-Jeeves pattern search.

In order to meet today's vehicle design requirements and to improve the cost and fuel efficiency, there is an increasing interest to design light-weight and cost-effective vehicle components. In this study, a topology design approach, which aims at defining of an optimum model at design stage, is used to decrease product cost and lead time to markets. An example of a vehicle component design is presented to illustrate the application of the topology optimisation approach for the optimal design of vehicle components.

Bu çalışma, 14-20 Kasım 2014 tarihlerinde Montreal[Kanada]'da düzenlenen ASME International Mechanical Engineering Congress and Exposition (IMECE)'de bildiri olarak sunulmuştur. Recently, there have been a number of research activities on spur gears with asymmetric teeth. The benefits of asymmetric gears are: higher load capacity, reduced bending and contact stress, lower weight, lower dynamic loads, reduced wear depths on tooth flank, higher reliability, and higher efficiency. Each of the benefits can be obtained through asymmetric teeth designed correctly. Gears operate in several conditions, such as inappropriate lubrication, excessive loads and installation problems. In working conditions, damage can occur in tooth surfaces due to excessive loads and unsuitable operating conditions. One of the important parameters of the tooth is stiffness, which is found to be reduced proportionally to the severity of the defect by asymmetric tooth design as described in this paper. The estimation of gear stiffness is an important parameter for determining loads between the gear teeth when two sets of teeth are in contact. In this paper, a 2-D tooth model is developed for finite elements analysis. A novel formula is derived from finite element results in order to estimate tooth stiffness depending on the tooth number and pressure angle on the drive side. Tooth stiffness for spur gears with asymmetric teeth is calculated and the results were compared with well known equations in literature.

Slider bearings are widely applied in mechanical systems, where the design needs cover increased load capacity, lowered friction and power consumption and creative designs. This work is governed to perform a parametric characterization, by generating a novel structure on the upper slider surface, which can formally be expressed in micro-machined wavy-form, where the individual and combined influences of various structural design parameters and boundary conditions, on the performance records, are also evaluated. Computations put forward that the contribution of the wave amplitude on power loss values is highly dependent on the level of inlet pressure ; higher amplitudes are determined to increase power loss in the lowest inlet pressure case of 1.01, whereas the contrary outcome is determined in the higher inlet pressure cases of 3.01 & 5.01. Designing the slider bearing system, based on optimal load capacity, produced the optimum wave number ranges as 10-45, 7-11 and 5-8 for the pad inclinations of 5°, 4° and 3° respectively.

In metal cutting, the problems need to be well analyzed in order to take precautions before any unexpected results are encountered. This process plays a significant role in achieving consistent quality and in controlling the overall cost of manufacturing. However, it is a difficult task that needs an expert who has a great deal of information and experience in metal cutting. In the present paper, a knowledge-based expert system (COROSolve) that investigates problems that are encountered in three main metal cutting areas: turning, milling and drilling is developed. A great deal of metal cutting operations such as external/internal turning with negative/positive inserts, aluminum turning, parting bars/tubes, grooving, profiling, recessing and threading operations in turning; face milling, square shoulder milling, end milling, multi-purpose milling and side and face milling operations in milling; and drilling operations that use solid drills or drills with indexable inserts in drilling are taken into consideration. COROSolve gives recommendations for the cutting data (i.e., cutting speed, depth of cut, and feed) and updates the problem, cause and remedy database, thus the number of problems that the system can handle is increased.

In this paper, the coupled flexural–torsional free and forced vibrations of a beam with tip and/or in-span attachments are studied. First, a mathematical model is established, which consists of a beam with several tip attachments, i.e, a tip mass of non-negligible dimensions, a linear spring grounding the tip mass, and a torsional spring connected at the end of the beam. The modal functions of this model and the orthogonality condition among them are derived. For the purpose of verification the properties of the tip attachments are changed, and the numerical results obtained are compared with those given in the relevant literature. Effects of tip mass and distributed mass in-span on natural frequencies and modes are investigated for two cantilever beams with different cross sections. An application of the orthogonality condition in the case of a beam with tip mass is also presented for a forced vibration example.

In this work cutting FEA of cutting tools prior to fracture is investigated. Fracture is the catastrophic end of the cutting edge that should be avoided for the cutting tool in order to have a longer tool life. This paper presents finite element modelling of a cutting tool just before its fracture. The data used in FEA are gathered from a tool breakage system that detects the fracture according to the variations of the cutting forces measured by a three-dimensional force dynamometer. The workpiece material used in the experiments is cold work tool steel, AISI O1 (60 HRC) and the cutting tool material is uncoated tungsten carbide (DNMG 150608). In order to investigate the cutting tool conditions in longitudinal external turning operations prior to fracture, static and dynamic finite element analyses are conducted. After the static finite element analysis, the modal and harmonic response analyses are carried on and the dynamic behaviours of the cutting tool structure are investigated. All FE analyses were performed using a commercial finite element package ANSYS.

Tool life and condition monitoring systems can be used effectively in cutting processes. Since no exact and reliable mathematical models exist for the cutting process which are able to predict tool wear, tool breakage, cutting temperature and forces, the development of tool condition monitoring systems are highly requested by industry, especially in recent years. The purpose of this research is to develop a tool condition monitoring and a real-time tool life detection system in turning processes. The software and hardware generated for this research is based on the characteristic variations of the cutting forces. When a tool wears or breaks, cutting forces increase slightly right after the tool breakage and then decrease sharply. The change of cutting forces can itself be a good indicator to detect the tool failure. The experimental set-up developed in this research consists of a dynamometer, a pre-amplifier, an A/D converter, and a personal computer. The workpiece material is AISI 1050 steel and the tool material is coated and uncoated tungsten carbide (ISO P25). The type of insert that is used is DNMG 150608. No cutting fluid was used during the turning operations. The performance of the system has been tested experimentally for certain machining conditions and the experimental results showed that the system was being successful in tool breakage detection.

Most vehicles have a heating, ventilation and air conditioning (HVAC) device to control the thermal environments of interior of the vehicle. But, under hot summer season or cold winter conditions, it is difficult to achieve and maintain thermal comfort in an automobile from the start up to the steady-state conditions. During these transition periods, an understanding of human thermoregulatory processes facilitates the design and development of improved heating and cooling systems. This study presents a model of thermal interactions between a human body and the interior environment of an automobile. The model is based on the heat balance equation for human body, combined with empirical equations defining the sweat rate and mean skin temperature. Simulation has been performed by the use of transient conditions. The effects of both heating and cooling processes on the thermal comfort inside the automobile are investigated. Results are compared with the present measurements and available experimental data in the literature. It is shown that the agreement between the experimental data and the model is very good.

With developing technology and the rapid increase in world population, the demand for energy is ever increasing. Conventional energy will not be enough to meet the continuously increasing need for energy in the future. In this case, renewable energy sources will become important. Solar energy is a very important energy source because of its advantages. Instead of a compressor system, which uses electricity, an absorption cooling system, using renewable energy and kinds of waste heat energy, may be used for cooling. In this study, a solar-powered, single stage, absorption cooling system, using a water–lithium bromide solution, is simulated. A modular computer program has been developed for the absorption system to simulate various cycle configurations and solar energy parameters for Antalya, Turkey. So, the effects of hot water inlet temperatures on the coefficient of performance (COP) and the surface area of the absorption cooling components are studied. In addition, reference temperatures which are the minimum allowable hot water inlet temperatures are determined and their effect on the fraction of the total load met by non–purchased energy (FNP) and the coefficient of performance are researched. Also, the effects of the collector type and storage tank mass are investigated in detail.

A single air jet or an array of air jets, impinging normally on a surface, may be used to achieve enhanced heat and mass transfer coefficients for convective heating, cooling and drying. To provide data for designers of industrial equipment, a programme of research has been implemented to study the heat and mass transfer processes. An original optimization of nozzle arrays under impinging air jets has been given for both academic and industrial users. Also optimum parameters presented here are simple and have a wide applicability.

In this paper, a workpiece-fixture layout verification approach with the application of frictional contact and chip removal effects using a finite-element technique, is presented. The objective of the proposed system is to overcome the deficiencies of existing fixture design approaches. Workpiece-fixture. layout verification analysis is carried out for time varying machining forces to ensure that the workpiece will be held against the cutting and clamping forces. The chip removal effect and frictional contact between the workpiece and the fixture elements are taken into account using a material removal approach based on element death technique and nonlinear finite-element analysis. A case study illustrates the application of the proposed approach.

It is important to provide a regular unidirectional air distribution in an operating room to reduce the number of particles. Measurements were taken in the one of the operating rooms at Uludag University Medical School, with laminar air flow unit and two-cornered outlet which was thought to have some airflow problems. Moreover, a three-dimensional computational fluid dynamics model has been developed where the measurements were taken in. The distributions of air velocity, temperature, and relative humidity have been examined and compared with the measurements to validate the computational fluid dynamics analyses. In addition to present model, four-cornered outlet operating room has been analyzed and compared with the results of two-cornered one. It is concluded that the case of four-cornered outlet provides more suitable thermal distribution, which results in a reduction of the particle numbers in the interior. Although there is no significant change in temperature and relative humidity in the operating room, air distribution changes dramatically.

This paper explores a design strategy of hopping robots, which makes use of free vibration of an elastic curved beam. In this strategy, the leg structure consists of a specifically shaped elastic curved beam and a small rotating mass that induces free vibration of the entire robot body. Although we expect to improve energy efficiency of locomotion by exploiting the mechanical dynamics, it is not trivial to take advantage of the coupled dynamics between actuation and mechanical structures for the purpose of locomotion. From this perspective, this paper explains the basic design principles through modeling, simulation, and experiments of a minimalistic hopping robot platform. More specifically, we show how to design elastic curved beams for stable hopping locomotion and the control method by using unconventional actuation. In addition, we also analyze the proposed design strategy in terms of energy efficiency and discuss how it can be applied to the other forms of legged robot locomotion. Swiss National Science Foundation (SNSF) European Commission (PP00P2123387/1)

Today, companies are faced with fierce competition which is characterized by the necessity to bring the higher quality prod ucts and lower priced products to the market in shorter times than their competitors. The key to the success of organizations is the effec tive integration of design and applications following design such as machining, process planning, analysis, assembly, inspection etc. It was seen that effectiveness of the traditional CIM systems is not satisfactory to ensure competitiveness and high productivity. Recently, the concept of CE has been proposed to overcome the problems exist in integration. However, it has been recognized by both academic and industrial environments that efficient application of CE is still not achieved. In this research, STEP based feature recognition using neural networks is presented to develop feature based model and to enhance the integration of production activities in CE.

This paper describes a procedure to calculate the machining conditions, such as the cutting speed, feed rate and depth of cut for turning operations with minimum production cost or the maximum production rate as the objective function. The optimum number of machining passes and the depth of cut for each pass is obtained through the dynamic programming technique and optimum values of machining conditions for each pass are determined based on the objective function criteria by search method application to the feasible region. Production cost and production time values are determined for different workpiece and tool material for the same input data. In the optimization procedure, the objective functions are subject to constraints of maximum and minimum feed rates and speeds available, cutting power, tool life, deflection of work piece, axial pre-load and surface roughness. By graphical representation of the objective function and the constraints in the developed software, the effects of constraints on the objective function can be evaluated. The parameters that are assumed to be most effective in determining the optimum point can easily be changed and the revised graph can be inspected for possible improvements in the optimum value.

Elasto-plastic stress analysis is an important solution for a used ductile adhesive in single or double lap solutions. After loading, the joint strength can be increased by residual stresses. In this study, an elasto-plastic stress analyses of the shear and peel stresses are carried out in a double-lap joint. The adhesive material is chosen as a ductile material which is DP460. Elasto-plastic solution of the shear stress is obtained in a simple and accurate form in one dimensional case. Then, the solution of the peel stress is performed by considering the shear stress in the elasto-plastic form. In this solution, the boundary conditions are satisfied by the Newton-Raphson method. A good agreement is obtained between these analytical and numerical (ANSYS 10) solutions. The values are calculated highest at the ends of the adhesive. (c) 2012 Elsevier Ltd. All rights reserved.

Local creep properties of a P91 weldment consisting of distinct zones, namely base metal, weld metal, as well as the fine-grained and the coarse-grained parts of the heat-affected zone were examined by Small Punch creep tests. Deflection vs. time graphs showed the zones' different creep resistances with that of the Heat Affected Zone-Fine Grained being lowest. Norton and Monkman–Grant type relations were established from Small Punch deflection curves for all zones. The evaluation of the Small Punch results was performed according to a new approach originating from the membrane stretching theory, as well as the method associated with the European Code of Practice for Small Punch Testing. The stress–rupture time results calculated by the new method were found to be very close to the Code of Practice's results with a similar amount of scatter, noting that with the new method, each Small Punch creep test is analyzed individually according to its observed deflection curve contrary to the Code of Practice method which disregards the actual deflection behaviour., JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Management

Currently, renewable energy resources are becoming more important to reduce greenhouse gas emissions and increase energy efficiency. Researchers have focused on all components of wind turbines to increase reliability and minimize cost. In this paper, a procedure including a cost analysis method and a particle swarm optimization algorithm has been presented to efficiently design low cost steel wind turbine towers. A virtual tool is developed in MATLAB for the cost optimization of wind turbine steel towers with ring stiffeners using a particle swarm optimization algorithm. A wind turbine tower optimization problem in the literature is solved using the developed computer program. In the optimization procedure the optimization results match very well with the optimization results obtained previously. The wall thickness of the shell segments and the dimensions of the ring stiffeners are selected as the design variables, and the limits of the local buckling for the flat ring stiffeners, the local shell buckling limit, the panel ring buckling limit and the limitation of the frequency are considered the design constraints. Numerical examples are presented to understand the impacts of the design variables on the total cost of the wind turbine tower. Texas Tech University, Mechanical Engineering Department (DE-FG36-06GO86092)

In this study, internal stresses of an elliptical ring sector with the cross section of a multi connected region composed of two confocal ellipses, subjected to pure bending are analyzed. Gohner's method is used for analysis and therefore, some difficulties caused by elliptical coordinates are eliminated. The analysis is limited to determining the first correction to the initial stress state for pure bending of an elliptical ring sector with the cross section of two confocal ellipses.

In this paper, design and analysis of improved energy absorbing pads, which are widely used for reducing occupants' injury in case of side impact, are presented to minimise the side impact effects on occupants. This research is part of an ongoing vehicle design and development project to reduce the vehicle development time and cost by using energy absorbing pads to improve the passive safety for side collisions and to reduce the injuries without further increasing weight of the vehicle. The use of energy absorbing pads, especially in side impact, has been increasing significantly for the last decades. The energy absorption capacity and lightweight material specifications of expanded polypropylene (EPP) and polypropylene (PP) are major characteristics that make the use of these pads in automotive industry. The present approach is employed to design improved energy absorbing pads using different materials and introducing material model selection, modelling, simulation and validity studies. TOFAŞ-FIAT Otomotiv Fabrikası, Bursa, Türkiye