This paper presents a model of scheduling of multi unit construction project based on an NP-hard permutation flow shop problem, in which the considered criterion is the sum of the costs of the works' execution of the project considering the time of the project as a constraint. It is also assumed that each job in the units constituting the project may be realized in up to three different ways with specific time and cost of execution. The optimization task relies on solving the problem with two different decision variables: the order of execution of units (permutation) and a set of ways to carry out the works in units. The task presented in the paper is performed with the use of a created algorithm which searches the space of solutions in which metaheuristic simulated annealing algorithm is used. The paper presents a calculation example showing the applicability of the model in the optimization of sub-contractors' work in the construction project.
In modern microelectronics progress has been made towards low power ultra large-scale integration (ULSI), and nano-structure devices such as single electron transistors and quantum dots. In this technology application of new materials, which includes high-κ dielectrics for the MOSFET transistors, with extraordinary purity and uniformity is required. Failure analysis and reliability investigations of such films very often requires highresolution local measurements of electrical surface parameters. This kind of experiments can be performed using conductive atomic force microscopy, which provides simultaneous measurement of surface topography and current ?owing through the investigated layer. In order to acquire reliable data, there was designed a precise measurement and control system, which included a low-noise current-to-voltage converter of picoampere resolution, a scanning stage with control electronics and a data acquisition system. In the paper we describe the architecture of the designed and applied experimental set-up. We also present results of simultaneous measurements of topography and current on gold and highly oriented pyrolytic graphite (HOPG).
The article presents results of heat treatment on the high chromium cast iron. The study was carrying out on samples cut from the casting
made from chromium cast iron. Those were hardened at different temperatures, then tempered and soft annealed. The heat treatment was
performed in a laboratory chamber furnace in the Department of Engineering Alloys and Composites at Faculty of Foundry Engineering
AGH. At each stage of the heat treatment the hardness was measured by Vickers and Rockwell methods, and the microscope images were
done. Additionally based on images from the optical microscope the microstructure was assessed. Based on these results, the effect of
hardening, tempering and soft annealing on the microstructure and hardness of high chromium cast iron was studied. Next the effects of
different hardening temperatures on the properties of high chromium cast iron were compared. The study led to systemize the literature
data of the parameters of heat treatment of high chromium cast iron, and optimal conditions for heat treatment was proposed for casts of
similar properties and parameters.
The paper presents research on the effects of soft annealing parameters on a change of the impact strength KC and Brinell hardness (HB)
of the EN AC-AlSi11 alloy. The research has been performed according to the trivalent testing plan for two input parameters –
temperature in the range between 280°C and 370°C and time in the range between 2 and 8 hours. The application of such heat treatment
improves the plasticity of the investigated alloy. The improvement of the impact strength KC by 71% and the decrease of the hardness HB
by 20% was achieved for the soft annealing treatment conducted at a temperature 370°C for 8 hours, compared to the alloy without the
heat treatment. A change of the form of eutectic silicon precipitations which underwent refinement, coagulation and partial rounding, had
a direct effect on the hardness HB and impact strength KC. The results obtained were used to prepare space plots enabling the temperature
and time for soft annealing treatment to be selected with reference to the obtained impact strength KC and hardness HB of the alloy with
the heat treatment.
Microstructures and mechanical properties of as-cast Al-6.5Mg-1.5Zn-0.5Fe alloys newly alloy-designed for the parts of automobile were investigated in detail. The aluminum (Al) sheets of 4 mm thickness, 30 mm width and 100 mm length were reduced to a thickness of 1mm by multi-pass rolling at ambient temperature and subsequently annealed for 1h at 200~500°C. The as-cast Al sheet was deformed without a formation of so large cracks even at huge rolling reduction of 75%. The recrystallization begun to occur at 250°C, it finished at 350°C. The as-rolled material showed tensile strength of 430 MPa and tensile elongation of 4.7%, however the specimen after annealing at 500°C showed the strength of 305 MPa and the elongation of 32%. The fraction of high angle grain boundaries above 15 degree increased greatly after annealing at high temperatures. These characteristics of the specimens after annealing were discussed in detail.
This paper shows results of researches of a structure and mechanical properties of metal sheets of IF steels subjected torecrystallization
annealing. The annealing was held in the scope of the temperature of 600-900°C over 25 min time. The impact of heat treatment on changes of properties and structure of the researches steel has been analysed. During annealing typical processes of rebuilding of the structure deformed as a result of cold deformation in the form of forming new recrystallized grains and their growth were observed. As the temperature of annealing increases the hardness of the material gradually decreases.
An analysis has been carried out of the influence of annealing time at the preheating temperature of 650 °C on the change in hardness and alloy structure of lamellar graphite cast iron in the working as well as in the laboratory conditions. This preheat temperature is common during reclaiming welding of castings with complex shapes. The changes in unalloyed cast iron EN-GJL 200 to EN-GJL 300 according to ISO 1690 standard and cast iron with low amount of elements such as Sn, Cu, Cr, and Mo and their combinations were assessed. It was found that the cast iron of higher strength grades has better hardness and structural stability. Cast iron alloyed with chromium or its combinations has the highest stability. In unalloyed cast iron, a partial degradation of pearlite occurs; in alloyed cast iron the structural changes are not conclusive.
Production processes of hot forging most often look similar [1-3]. Forging in several operations, usually in three or four. Most often the first operation is upsetting or flattening (sometimes rolling). The last operation is finishing forging. This applies to the production of steel forgings for the automotive, agricultural and other similar industries. Typical production proceeds as follows: the forgings are cleaned (shot-blasted) and then heat treatment is performed. It can be normalization, hardening and tempering, etc. After the heat treatment, forgings are checked and subjected to strength and microscopic tests, hardness tests, impact tests. The type of tests depends on the recipient. The process described in the work takes place in three operations. The heat treatment used so far is hardening and tempering. An attempt was made to change the heat treatment technology for a selected product made of 42CrMo4 steel (1.7225) (4140). An isothermal annealing test was carried out at different temperatures and for different times. The possibility of using heat from the forging process in heat treatment processes for the described product has been confirmed.
This paper presents the influence of annealing time 30, 60 and 120 min at 1000°C for quenching CuAl7Fe5Ni5W2Si2 bronze in 10% water solution of NaCl, on the microstructure and mechanical properties. The presented results concern the species newly developed aluminum-iron-nickel bronze, with additions W and Si. In order to determine changes in the microstructure of the hardened bronze metallographic studies were performed on cylindrical samples of diameter 10 mm, on the metallographic microscope with digital image analysis, X-ray phase analysis, EDX point with the digital recording on the computer. Specified percentage of the microstructure of martensite and bainite, participation of proeutectoid α phase in the microstructure, grain size of former β phase, the amount of dissolved κ phase. It was found that in the microstructure of bronze in the cast state, there are a number of intermetallic phases of κ type. At interphase boundaries of primary intermetallic faceted precipitates, especially rich in tungsten (IM_W), nucleate and grow dendritic primary intermetallic κI phases, with chemical composition similar to the type of Fe3Si iron silicide. Dissolved, during the heating, in the β phase are all the intermediate phase included in the microstructure, with the exception of primary intermetallic phases of tungsten and κI. Prolongation of the isothermal annealing causes coagulation and coalescence of primary phases. In microstructure of the bronze after quenching obtained the α phase precipitation on the grain boundary of secondary β phase, coarse bainite and martensite, for all annealing times. With the change of annealing time are changed the relative proportions of individual phases or their systems, in the microstructure. In the microstructure of bronze, hold at temperature of 1000°C for 60 min, after quenching martensitic microstructure was obtained with the primary phases, and the least amount of bainite
The paper presents the microstructure and selected properties of ausferritic nodular cast iron annealed at the temperature 520 and 550°C.
This choice was dictated by the temperatures used in the practice of nitriding. Nodular graphite in cast iron was obtained with use of
Inmold process. Cast iron containing molybdenum and copper ensuring obtaining an ausferrite in the cast iron matrix without the use of
heat treatment of castings was tested. The effect of annealing temperature on the microstructure and the kind of fracture of the ausferritic
nodular cast iron was presented. The effect of an annealing temperature on hardness, impact strength and the microhardness of ausferritic
nodular cast iron matrix was shown too. The lamellar structure of phases in the cast iron matrix after annealing has been ascertained. There
has been an increase in hardness of an annealed cast iron and microhardness of its matrix. The reduction in the impact strength of the cast
iron annealed at 520 and 550°C was approximately 10-30%. Both an increase in the hardness of cast iron as well as an decrease in its
impact strength is probably due to the separation of secondary carbides during the heat treatment.
In the calculations presented in the article, an artificial immune system (AIS) was used to plan the routes of the fleet of delivery vehicles supplying food products to customers waiting for the delivery within a specified, short time, in such a manner so as to avoid delays and minimize the number of delivery vehicles. This type of task is classified as an open vehicle routing problem with time windows (OVRPWT). It comes down to the task of a traveling salesman, which belongs to NP-hard problems. The use of the AIS to solve this problem proved effective. The paper compares the results of AIS with two other varieties of artificial intelligence: genetic algorithms (GA) and simulated annealing (SA). The presented methods are controlled by sets of parameters, which were adjusted using the Taguchi method. Finally, the results were compared, which allowed for the evaluation of all these methods. The results obtained using AIS proved to be the best.
This paper presents methods for optimal test frequencies search with the use of heuristic approaches. It includes a short summary of the analogue circuits fault diagnosis and brief introductions to the soft computing techniques like evolutionary computation and the fuzzy set theory. The reduction of both, test time and signal complexity are the main goals of developed methods. At the before test stage, a heuristic engine is applied for the principal frequency search. The methods produce a frequency set which can be used in the SBT diagnosis procedure. At the after test stage, only a few frequencies can be assembled instead of full amplitude response characteristic. There are ambiguity sets provided to avoid a fault tolerance masking effect.
Multilayered composites based on light metals are promising materials in many applications. In the present work the 15-layered clad, composed of alternately stacked of Ti(Gr.1) and AA1050-H24 alloy sheets of 1 mm thick has been investigated with respect to determination of the kinetic of the Al3Ti phase growth. The defect-free multilayered composite was successfully formed by explosive welding technology. Then EXW samples were modified via annealing at the temperature of 600oC in closed die under pressure of 44 MPa for various times ranged between 1 and 10 h. Transmission and Scanning Electron Microscopy examinations were conducted in order to study the kinetic of the elements migration across the interfaces between the layers of the Al/Ti composite. The macro-scale observations of samples after EXW revealed that wavy interfaces were always formed in layers near the explosive charge. The increase of the distance from the top surface leads to flattening of the interface with very thin reaction layer between Al and Ti sheets. During annealing the kinetic of the Al3Ti phase growth is similar near all interfaces and coincides with data from other works. It was found that despite the loading after 10 h of annealing still only small part of Al-sheets undergoes dissolution and the width of the reaction layer does not exceed 5-8 µm.