Comparison of non-traditional technologies for material cutting from the point of view of surface roughness

The contribution deals with comparing non-traditional cutting technologies from the point of view of generated surface roughness. The comparison is carried out for technologies of abrasive waterjet cutting, oxygen cutting, laser and plasma cutting. As an experimental material, EN S355J0 structural steel and titanium CP-Ti Grade 2 was used. Surface topography measurement was done using a Mitutoyo Surftest SJ-401 instrument, and an optical profilometer MicroProf FRT was used for comparison and verification of acquired surface data. The aim of the contribution is to clarify, on the basis of experimental measurements, the behaviour of a topographic function after various ways of cutting; the knowledge of the function is necessary for solving both theoretical and practical technological tasks. The topographic function, which is a basis for the prediction of quality and control of the cutting processes, was derived in an original way. The use of individual technologies depends on technical and economical possibilities and on environmental influences. The results of measurement of cut surface roughness are in good accordance with the results of theoretical analysis.     

Raspberry wine fermentation with suspended and immobilized yeast cells of two strains of Saccharomyces cerevisiae

The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212. Copyright © 2014 John Wiley & Sons, Ltd.     

Modeling of the Effect of Path Planning on Thermokinetic Evolutions in Laser Powder Deposition Process

A thermokinetic model coupling finite-element heat transfer with transformation kinetics is developed to determine the effect of deposition patterns on the phase-transformation kinetics of laser powder deposition (LPD) process of a hot-work tool steel. The finite-element model is used to define the temperature history of the process used in an empirical-based kinetic model to analyze the tempering effect of the heating and cooling cycles of the deposition process. An area is defined to be covered by AISI H13 on a substrate of AISI 1018 with three different deposition patterns: one section, two section, and three section. The two-section pattern divides the area of the one-section pattern into two sections, and the three-section pattern divides that area into three sections. The results show that dividing the area under deposition into smaller areas can influence the phase transformation kinetics of the process and, consequently, change the final hardness of the deposited material. The two-section pattern shows a higher average hardness than the one-section pattern, and the three-section pattern shows a fully hardened surface without significant tempered zones of low hardness. To verify the results, a microhardness test and scanning electron microscope were used.     

An Experimental Study on Slurry Erosion Resistance of Single and Multilayered Deposits of Ni-WC Produced by Laser-Based Powder Deposition Process

Single and multilayered deposits containing different mass fractions of tungsten carbide (WC) in nickel (Ni)-matrix (NT-20, NT-60, NT-80) are deposited on a AISI 4140 steel substrate using a laser-based powder deposition process. The transverse cross section of the coupons reveals that the higher the mass fraction of WC in Ni-matrix leads to a more uniform distribution through Ni-matrix. The slurry erosion resistance of the fabricated coupons is tested at three different impingement angles using an abrasive water jet cutting machine, which is quantified based on the erosion rate. The top layer of a multilayered deposit (i.e., NT-60 in a two-layer NT-60 over NT-20 deposit) exhibits better erosion resistance at all three tested impingement angles when compared to a single-layer (NT-60) deposit. A definite increase in the erosion resistance is noted with an addition of nano-size WC particles. The relationship between the different mass fractions of reinforcement (WC) in the deposited composite material (Ni-WC) and their corresponding matrix (Ni) hardness on the erosion rate is studied. The eroded surface is analyzed in the light of a three-dimensional (3-D) profilometer and a scanning electron microscope (SEM). The results show that a volume fraction of approximately 62% of WC with a Ni-matrix hardness of 540 HV resulting in the gouging out of WC from the Ni-matrix by the action of slurry. It is concluded that the slurry erosion resistance of the AISI 4140 steel can be significantly enhanced by introducing single and multilayered deposits of Ni-WC composite material fabricated by the laser-based powder deposition process.     

An approach to instruction set compiled simulator development based on a target processor C compiler back-end design

Many instruction set simulation approaches place the retargetability and/or cycle-accuracy as the key features for easier architectural exploration and performance estimation early in the hardware development phase. This paper describes an approach in which importance of speed and controllability is placed above the cycle-accuracy and retargetability, thus providing a better platform for software development. The main idea behind this work is to associate the compiled simulator effort with the development of the C language compiler for the target embedded processor, using the knowledge related to compilers and reusing some common software elements. Through the prototype design of a compiled simulator for the Cirrus Logic Coyote DSP architecture, many implementation aspects are presented showing that this approach has great potential.     

Hardness prediction in multi-pass direct diode laser heat treatment by on-line surface temperature monitoring

This study was attempted to develop a process model, using the temperature values measured by the coupled infrared temperature measurement system (pyrometer and camera) correlated with the measured values of case depth hardness of the tool steel AISI S7 (hypo-eutectoid steel) for the specified multi-pass laser heat treatment conditions (1000–2500 J). A number of heat treatment experiments by changing the laser power (1400–1800 W), scanning speed (15–25 mm/s), size of overlap (1–6 mm), and the length of scan (10–30 mm) on the tool steel AISI S7 were carried out by using a 2-kW direct diode laser. The results indicated that the loss of case depth hardness uniformity was highly influenced by the tempering temperature and the change of cooling rate. The combination of higher laser power, lower scanning speed, smaller size of overlap, and the longer length of scan were influenced the formation of mixture of phases (martensite, bainite, ferrite, and pearlite) which in turn affected the case depth hardness uniformity. The process model can be used as a handy tool for the process engineers to configure the processing conditions in order to obtain the desired case depth hardness for the hypo-eutectoid steels.     

Assessing Well Drilling Disturbance Effects on Offshore Foundation Piles in Clay

It is widely recognized that hydrocarbon well drilling from offshore platforms affects the surrounding ground. In clays, the level of disturbance can be severe when sections of open well collapse during drilling, impeding fluid return to the seabed (termed “packing-off”), and drilling fluid pressure is increased in order to obtain a breakthrough return path for the fluid. Significant swelling and hydraulic fracturing can take place in the surrounding soil mass. With time the excess pore pressures will dissipate and could cause increases in pore pressures far from the wells, potentially affecting areas occupied by the platform’s foundation piles. There is no established procedure to quantify the impact of such processes on foundation performance. This paper presents a numerical approach that involves a series of finite-element analyses in which drilling disturbance is treated as an idealized fluid injection process. The entry of pressurized drilling water into progressively enlarging fractured disturbed zones, and hence into the surrounding soil mass, is simulated with two- and three-dimensional nonlinear finite-element (FE) models, without modeling the actual hydraulic fracturing processes. The analyses make use of key observations made in the field at a piled offshore platform. The FE analyses predict marginal foundation capacity reductions, as well as significant global vertical and horizontal movements developing around the piles. It is demonstrated that the ground movement predictions are heavily influenced by the degree of geometric idealization.     

Optimization of peripheral non-round cylindrical grinding via an adaptable constant-temperature process

This paper introduces two new concepts in peripheral cylindrical grinding of non-round workpieces: (1) choosing process parameters based on a thermal model for achieving a constant temperature; and (2) optimizing the grinding process for shorter cycle times while applying the concept of constant temperature. The modeling of geometry, kinematics and thermal aspects accounts for large variations in specific material-removal rate, contact length and workpiece velocity as the workpiece rotates. Optimization is validated both in simulation and with grinding experiments, including measurements of Barkhausen noise. Significantly reduced cycle times are obtained along with a better ability to avoid thermal damage.