An advanced numerical model of friction stir welding of DH36 steel

A numerical model of Friction Stir Welding (FSW) of DH36 steel plate (6mm thickness) has been developed using a CFD technique. Two welding speed conditions were used, a low welding speed of 200 RPM - 100mm/min, and a high welding speed of 550RPM- 400 mm/min. The heat generation, material flow and strain rate were calculated based on plastic deformation and frictional contact between the tool and workpiece. A CFD-based model has been produced to represent the asymmetry in temperature distribution between the advancing and retreating side, the material flow and the strain rate. The geometry of the model includes the tool plunged into the plate. The cooling system was also included in the simulation by calculating the heat flux lost for each part of the tool. The heat generated by viscous dissipation away from the tool was also taken into account. The total heat generated was divided into the individual tool parts (shoulder, probe side and probe end) and was found to be in good agreement with the experimental results for the areas affected by these parts. The maximum temperature obtained for the slow welding speed was 1012oC and for the high welding speed was 1250oC. Experimental metallographic examination has also been carried out on DH36 FSW steel plates to validate the CFD model. SEM analysis showed the formation of a fine microstructure of bainite, acicular ferrite and ferrite/cementite aggregate in the welded zone as compared to the ferrite/pearlite morphology in the base metal. It is found from the CFD and experimental results that the high speed welding conditions can produce defects such as wormholes and cracks in the welds associated with the probe side and probe end due to the lack of material flow especially on the advancing side. Tensile and fatigue testing were carried out for both slow and high welding speed samples, which broke outside the welded region in the tensile test, however, slow welding speed samples show more resistance to fatigue test and survived 644128 cycles, the high speed welding samples failed after 111,736 cycles under the same load

PENGARUH VARIASI BOBOT ROLLER WEIGHT CVT TERHADAP AKSELERASI SEPEDA MOTOR HONDA VARIO 150

Based on the experience of automatic motorcycle users Honda Vario 150, the motorcycle has several weaknesses, but one of the weaknesses that often occurs is the slow acceleration of the motorcycle from low to medium speed. CVT transmission system ( Continuously Variable Transmission ) affects the slow acceleration of a motorcycle from low to medium speed. The purpose of this study is to analyze the results of testing the use of roller weights with standard weights (18 g), 16 mix standard, and 16 g to get the value of the best acceleration on a dead motorcycle c Honda Vario 150. The research method used is an experimental research method using two research methods, namely testing with a dynamometer and testing with acceleration measurements with logger pro software. The use of a standard roller weight (18 g) is the roller weight with the fastest acceleration on a Honda Vario 150 motorcycle. This is evidenced by an average acceleration of 2.98 m/s2 . While the roller weight of 16 mix standard and 16 g experienced a decrease in acceleration. For roller weight 16 mix standard, there was a decrease in acceleration of 15.44% with an average acceleration of 2.52 m/s2 . And on the 16 g roller weight, there is a decrease in acceleration of 28.86 % with an average acceleration of 2.12 m/s2

3D Microwave printing temperature control of continuous carbon fiber reinforced polymer composites

Continuous carbon fibers show dramatic promise as reinforcement materials to improve the stiffness, strength properties and design ability of 3D printed polymer parts. Current 3D printing methods have a low printing speed because the intrinsic slow and contact needed heat transfer disadvantages of the traditional resistive heating approach. We present a 3D microwave printing method by using the microwave for instantaneous and volumetric heating the continuous carbon fiber reinforced polymer (CCFRP) filament. This allows fabricating CCFRP components with much higher speed compared to traditional 3D printing technologies. To utilize the benefit of high printing speed, the speed-variation 3D microwave printing is applied to adapt the diverse printing path and reduce the printing period. In this paper, a new 3D microwave printing temperature control method by combining the prediction-model and step-proportional-integral-derivative control is researched to reduce the printing temperature difference of the CCFRP filaments during the speed-variation printing process. Three different CCFRP specimens with variation printing speed are tested, including a spanner, an aircraft and a spider from Nazca lines. The experimental results indicate that the new printing temperature control method for 3D microwave printing process dramatically reduces the temperature deviation. Further mechanical testing results indicate that the CCFRP printed with this method has a high tensile strength up to 358 MPa. This technology solved a key problem of 3D microwave printing of continuous carbon fiber reinforced polymer composites and can be used to manufacture complex polymer-matrix composite material

3D microwave printing temperature control of continuous carbon fiber reinforced composites

Continuous carbon fibers show dramatic promise as reinforcement materials to improve the stiffness, strength properties and design ability of 3D printed polymer parts. Current 3D printing methods have a low printing speed because the intrinsic slow and contact needed heat transfer disadvantages of the traditional resistive heating approach. We present a 3D microwave printing method by using the microwave for instantaneous and volumetric heating the continuous carbon fiber reinforced polymer (CCFRP) filament. This allows fabricating CCFRP components with much higher speed compared to traditional 3D printing technologies. To utilize the benefit of high printing speed, the speed-variation 3D microwave printing is applied to adapt the diverse printing path and reduce the printing period. In this paper, a new 3D microwave printing temperature control method by combining the prediction-model and step-proportional-integral-derivative control is researched to reduce the printing temperature difference of the CCFRP filaments during the speed-variation printing process. Three different CCFRP specimens with variation printing speed are tested, including a spanner, an aircraft and a spider from Nazca lines. The experimental results indicate that the new printing temperature control method for 3D microwave printing process dramatically reduces the temperature deviation. Further mechanical testing results indicate that the CCFRP printed with this method has a high tensile strength up to 358 MPa. This technology solved a key problem of 3D microwave printing of continuous carbon fiber reinforced polymer composites and can be used to manufacture complex polymer-matrix composite material

Continuous slow dynamic slope approach for stationary base internal combustion engine mapping

Engine control optimization, with its always growing complexity, is in permanent focus of engine researchers and developers all over the world. Automotive engines are dominantly used in dynamic conditions, but generally, steady-state operating points are used for building up mathematical models which are later subject to the numerical optimization. For this purpose, a large amount of steady-state regimes needs to be evaluated through experimental work at the engine test stand, which is an extremely time and funds consuming process. Consequently, the methodology for data gathering during engine dynamic excitation could lead to significant savings at the expense of acceptable data accuracy loss. The slow dynamic slope method starting from a stationary operating point was evaluated by several authors in the past. In this paper, slow dynamic slope method with exclusively transient excitation will be presented drawing attention to some of its advantages and drawbacks. The rate of change of engine load as a main control parameter during dynamic test is of great importance for the quality of the final data and for total test duration. In this regard, several tests of different duration were applied for fixed engine speed values to cover engine speed-load usage domain. An approximation of stationary testing results obtained in this way could be used for evaluation of the map gradients and thus as a guideline for additional stationary tests based on design of experiment method

Continuous slow dynamic slope approach for stationary base internal combustion engine mapping

Engine control optimization, with its always growing complexity, is in permanent focus of engine researchers and developers all over the world. Automotive engines are dominantly used in dynamic conditions, but generally, steady-state operating points are used for building up mathematical models which are later subject to the numerical optimization. For this purpose, a large amount of steady-state regimes needs to be evaluated through experimental work at the engine test stand, which is an extremely time and funds consuming process. Consequently, the methodology for data gathering during engine dynamic excitation could lead to significant savings at the expense of acceptable data accuracy loss. The slow dynamic slope method starting from a stationary operating point was evaluated by several authors in the past. In this paper, slow dynamic slope method with exclusively transient excitation will be presented drawing attention to some of its advantages and drawbacks. The rate of change of engine load as a main control parameter during dynamic test is of great importance for the quality of the final data and for total test duration. In this regard, several tests of different duration were applied for fixed engine speed values to cover engine speed-load usage domain. An approximation of stationary testing results obtained in this way could be used for evaluation of the map gradients and thus as a guideline for additional stationary tests based on design of experiment method

Fluency in dialogue: Turn‐taking behavior shapes perceived fluency in native and nonnative speech

Fluency is an important part of research on second language learning, but most research on language proficiency typically has not included oral fluency as part of interaction, even though natural communication usually occurs in conversations. The present study considered aspects of turn-taking behavior as part of the construct of fluency and investigated whether these aspects differentially influence perceived fluency ratings of native and non-native speech. Results from two experiments using acoustically manipulated speech showed that, in native speech, too ‘eager’ (interrupting a question with a fast answer) and too ‘reluctant’ answers (answering slowly after a long turn gap) negatively affected fluency ratings. However, in non-native speech, only too ‘reluctant’ answers led to lower fluency ratings. Thus, we demonstrate that acoustic properties of dialogue are perceived as part of fluency. By adding to our current understanding of dialogue fluency, these lab-based findings carry implications for language teaching and assessmen

Advances in friction stir welding of steel : Project HILDA

A microstructure and property evaluation of friction stir welded DH36 6mm plate has been undertaken. The study examined a wide range of process parameters and, from this, a process parameter envelope has been developed and an initial process parameter set established that gives good welding properties. Thermo-mechanical deformation studies were developed to generate flow stress regimes over a range of stain rates and temperatures and these data will support the on-going local numerical modelling development. A preliminary thermo-fluid model has been developed to predict temperature and material flow during the FSW of steel grade DH36. In this model, materials are considered as highly viscous incompressible fluid. The welded material is flowing around the rotating tool thanks to the modelling of the friction at tool/workpiece interface. In parallel, a global numerical model is being developed to predict the inherent residual stresses and distortion of FSW butt welded assemblies often in excess of 6m long plate

The Effect of Limited Attention and Delay on Negative Arousing False Memories

Previous research has shown that, in comparison to neutral stimuli, false memories for high arousing negative stimuli are greater after very fast presentation and limited attention at study. However, full compared to limited attention conditions still produce comparably more false memories for all stimuli types. Research has also shown that emotional stimuli benefit from a period of consolidation. What effect would such consolidation have on false memory formation even when attention is limited at study? The aim of the present study was to investigate the effect of fast presentation on false memory production for negatively-arousing and neutral items over time using the DRM paradigm. Sixty-Eight participants studied Negative and neutral DRM lists with fast or slow presentation conditions. Half completed a recognition test immediately and half completed a recognition test after one-week. Results revealed that, for fast presentation, negative critical lures increased after one week and were comparable to negative critical lures in the slow presentation encoding conditions. Neutral critical lures in the fast presentation condition did not change and remained lower compared to the slow presentation condition. These findings are the first demonstration that arousing negative false memories can increase over time when attention at encoding is limited

Dynamic Response of Textile Material under Transverse Impact

Textile materials, such as Dyneema and Kevlar, are the major raw materials for state of the art military or personal security armor vests. However, in impact experiments, actual observed penetration speed is much lower than theoretically predicted penetration speed. Each armor vest is composed of high performance yarns which are woven together to form fabrics, which when stacked together form a vest. Understanding penetration behavior of yarns is essential to evaluate the performance of fabric, which will be useful for the design of better vests. The project is composed of three parts: static experiments, dynamic yarn experiments and dynamic fabric experiments. In the static experiments, several types of textile materials will be loaded onto MTS testing machine under slow and constant speed by different projectiles, such as Fragment Simulating Projectile, Hemispherical Nose Projectile and Blade Projectile. Secondly, a powder gun will be used to provide high speed impact conditions. Several yarns will be impacted at high velocities and imaged simultaneously using a high speed camera. Finally, aforementioned experimental conditions will be utilized for fabrics experiments. At this preliminary phase of the investigation, only expected results are being reviewed. In the yarn experiments, impact angle, between impacted region (shear wave propagation region) and impacting region (transvers wave propagation region), is expected to be approximately constant. In the fabric experiments, the goal is to acquire the range of the penetration speeds for different types of textile materials with different number of layers. The acquired data will yield a strong background database for further improvement and adjustment in personal vest design