A comparative experiment for the analysis of microwave and thermal process induced strains of carbon fiber/bismaleimide composite materials

Carbon fiber reinforced bismaleimide composites provide many outstanding properties and are widely used in aerospace applications. However, cure-induced strains are present in virtually all composites that severely impact on the whole service lifecycle of composite components. This paper will demonstrate that the cure-induced strains can be drastically reduced in fiber/ bismaleimide composites using the microwave curing process. Nearly 95% reduction of cure-induced strains has been achieved compared with the conventional thermal heating process. The microwave manufacturing cycle for composites was only 36% of the thermal processing cycle. When using the microwave process, the spring-in angle of an L-shaped part was reduced by about 1.2°Compared by using thermal heating

Kuorma-autojen ja kauhakuormaajien toimintojen yhteensovittaminen avokaivoksissa käyttäen tilastollista dataa - ajojärjestysstrategiat, yhteensovituskerroin ja kaluston ikäperusteiset huollot

Economics today force mining companies to maximize profit over the life time of a mine. Especially in the context of open-pit mines, it is essential to acquire production with minimum cost. The ability to reduce operation costs can be directly achieved by utilizing trucks and shovels in an efficient manner. Dispatching approaches in the literature have considered different objectives in varying degrees of sophisticated assignments ranging from simple heuristic rules to complex mathematical programming. However, most approaches assume that all trucks and shovels have the same operating performance or ignore the stochastic nature of the truck-and-shovel operations. This thesis investigates one of the primary problems in an open-pit mine: efficient matching trucks and shovels. In other words, the aim is to determine the required number of trucks and shovels and their types to make the best match in order to satisfy the production target. This problem is investigated using different simulation and optimization models, which contain the behaviours of dispatching strategy, match factor, and age-based maintenance under an ideal operation and breakdown event. The results of this thesis show that the match factor ratio is able to determine limits for an appropriate fleet size selection, and can be used to estimate the relative efficiency of existing fleets. However, it cannot be used alone for fleet optimization. The choice of truck dispatching strategies and heuristic truck dispatching methods plays a crucial role to minimize the queuing time. Maintenance schedules are necessary to reduce breakdown, directly influencing equipment availability. Optimal preventive and corrective maintenance schedules are proposed for different truck age levels, providing cost savings. These proposed models offer potential applications to any situations in which truck fleets are used to transport material. Tiukka taloudellinen tilanne pakottaa teollisen kaivostoiminnan maksimoimaan tuottonsa koko kaivoksen elinkaaren ajalta. Tuotantotavoitteiden saavuttaminen mahdollisimman pienillä kustannuksilla on keskeistä erityisesti avokaivoksissa. Operatiivisten kustannusten alentamisessa on onnistuttu suoraan nostamalla kuorma-autojen ja kauhakuormaajien käyttöastetta. Eri tavoitteita palvelemaan on laadittu erilaisia ajojärjestysstrategioita, joiden kompleksisuus vaihtelee yksinkertaisista heuristisista säännöistä monimutkaisiin matemaattisiin malleihin. Suurin osa aiemmista lähestymistavoista lähtee kuitenkin oletuksesta, että kaikilla kuorma-autoilla ja kauhakuormaajilla on samanlainen suorituskyky, tai ne jättävät huomioimatta toimintaan liittyvät satunnaistekijät. Tässä työssä tarkastellaan yhtä avokaivosten pääongelmista: kuinka päättää kuorma-autojen ja kauhakuormaajien tarvittava määrä ja niiden tyypit, niin että ne toimisivat parhaalla mahdollisella tavalla toteuttaakseen tuotantotavoitteet. Ongelmaan esitetään ratkaisuksi eri simulointi- ja optimointimalleja, jotka ottavat huomioon ajojärjestysstrategian, kaluston ikäperusteiset huollot sekä kuorma-autojen ja kauhakuormaajien välisen yhteensovituskertoimen (match factor). Tulokset osoittavat, että yhteensovituskertoimen avulla voidaan määrittää rajat sopivan kuorma-auto-ja kauhakuormaajalaivueen koolle. Yhteensovituskerrointa voi käyttää myös käytössä olevan laivueen suhteellisen tehokkuuden estimoimiseen, mutta sitä ei voi käyttää ainoana kriteerinä laivueen koostumuksen optimoinnissa, vaan ajojärjestysstrategialla ja -menetelmällä on keskeinen rooli. Myös huoltojen aikatauluttaminen on välttämätöntä laiterikkojen vähentämiseksi, ja se vaikuttaa suoraan laitteiden käytettävyyteen. Työssä ehdotetut kuorma-autojen ikäjakaumien perusteella määritellyt optimaaliset ennakoivat huolto- ja korjausaikataulut alentavat kustannuksia. Tarkastellut mallit ovat yleistettävissä moniin muihinkin ympäristöihin, joissa kuljetukseen käytetään kuorma-autolaivueita.

Effects of curing techniques and silane treatment on mechanical and morphological properties of fly ash/epoxy composites

In this research, the effect of curing techniques and silane treatment on mechanical and morphological properties of fly ash (20 and 80 phr) filled epoxy composites were studied. The addition of N-2(amino-ethyl)-3 aminopropyltrimethoxysilane (KBM603) coupling agent was varied 0.0, 0.5, 1.0 and 1.5 %wt of the fly ash, for surface treatment of fly ash particles. The optimum curing conditions of conventional thermal and microwavecuring system were determined using a differential scanning calorimetry (DSC). The conventional hermal curing was performed at 70OC for 80 min while microwave curing was carried out at 240 wattfor 18 minutes in order to achieve the optimum curing conditions of the composites. The silane concentration of 0.5 wt% was recommended for the optimum mechanical properties of the fly ash, epoxy composites.Beyond these recommended contents, the mechanical properties greatly reduced, except for the flexural moduli. By comparing microwave cured composites with conventional thermal cured composites, it was foundthat microwave cured composites consumed shorter cure time and had higher ultimate strengths and elongation at break than those by the conventional thermal cure. The composites with higher tensile and flexuralmoduli could be obtained by the conventional thermal cure. The comparative results of composites cured using different microwave powers showed that the ultimate strengths and elongation at break decreased withincreasing microwave power while the effect was opposite for the tensile and flexural moduli

Digitalization of mine operations

One of the key factors in a profitable open-pit mine is the efficiency of the waste disposal system. Using GPS-technology, the truck-dispatching decisions can be made in real-time but the chosen strategy has a crucial role. Therefore, finding the optimal dispatching strategy for truck-shovel operations is extremely important. Dispatching strategies have been reported in the literature, but the comparison of these strategies is still missing. This paper illustrates the differences between the strategies by conducting a stochastic simulation study based on the data gathered from an actual mine. The findings underline the importance of the global vision in dispatching decisions.Peer reviewe