High gold (Au) alloys have many advantages, such as good mechanical properties and stable chemical properties for dental restoration. The purpose of this investigation was to investigate the effect ...of zirconia (ZrO2)-magnesia (MgO)-based investment combined with an argon arc vacuum pressure (Ar-arc VP) casting process on the recasting of high Au alloys.
The recasting Au alloys were compared between the control group of conventional SiO2-based investment/horizontal centrifugal (HC) casting and the experimental group of ZrO2–MgO-based investment/Ar-arc VP die casting. The first-generation castings were defined as being made from purchased Au alloys and the second-generation castings were made from 50 wt% of the original Au alloys before casting, plus the balance of the remaining 50 wt% from the previous castings. The third-generation was made from all old surplus from the previous castings. The ingots were measured for the marginal gap, surface roughness, interface oxidation, hardness, and phase identification.
The results showed that the recasting success rate reached 100%. The ZrO2–MgO-based investment/Ar-arc VP group had better edge precision, smaller oxide layer thickness, and lower hardness than the SiO2-based investment/HC group. However, surface roughness analysis indicated little difference between the two groups. Phase analysis showed that the recasting alloys of the second and third-generation groups contained higher Au contents than those of the first-generation.
Overall, the Au alloy can be better recasted and retain good mechanical properties under the clinically used 5 wt% ZrO2–MgO-based investment/Ar-arc VP casting method.
In precision casting, many model materials can be used to make complex, accurately sized molds. Model material is an important key for successful production. Wax models are widely used in model ...manufacturing because they allow economical production. In the wax injection method, some undesirable situations occur during the production of the model such as shrinkage, collapse, warpage, weld marks, surface defects, air marks, and burr formation that the manufacturer does not want. In this study, it is aimed to examine the effect of temperature and pressure parameters on shrinkage of the wax model in injection molding. The study was carried out at wax temperatures of 65 °C, 70 °C, and 75 °C and injection pressures of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa. In the experiments, the flow of the parts was observed during the filling of the plexiglass mold, and the shrinkage ratio of the obtained wax model was determined and evaluated. It is assigned that some of factors which affect quality of the final product produced by investment casting method are product shrinkage and surface quality of wax model.
In the present study, a superalloy round tube specimen prepared by directional precision casting without mechanical turning is experimentally investigated under the thermomechanical fatigue ...conditions of the in‐phase and out‐of‐phase thermomechanical angels from 500°C to 1000°C. The deformation behavior and damage mechanism of the round tube specimens under TMF load are discussed. It was confirmed that the tension–compression asymmetry under TMF cycling is affected by temperature–load phasing and mechanical strain range. Moreover, the damage to round tube specimens includes creep, fatigue and oxidation. Due to the concentrated stress, the rough surface of the specimen provides suitable locations for crack initiation. A novel life prediction approach that combines the Neu–Sehitoglu model and modified Manson–Coffin model was proposed in response to the traditional life model's insufficient prediction performance. This method may explain the TMF life of precision cast specimens.
Highlights
TMF of precision casted round tube specimens was investigated.
Crack initiation at the notches of rough surface due to stress concentration.
A new life prediction method was proposed for precision casted specimens.
To study the coupling mechanism of shrinkage distribution and complex structures in the precision casting process of hollow turbine blades, the blade structure was simplified to a hollow thin-walled ...structure with resistance and non-resistance. Four different structures of casting and a casting system were designed. Based on the combination of numerical simulation and experimental measurement, the shrinkage distribution and shrinkage model of castings were established. The results show that the simulated and measured shrinkages have the same trend. Then, the structural parameters affecting shrinkage, including wall thickness, outer diameter, and unobstructed structure, were discussed. A mapping model based on a backpropagation (BP) neural network reflecting the relationship between structural parameters and shrinkage rate was constructed. According to the BP neural-network-based mapping model, the average deviations between the predicted and measured values of the transitional and normal sections are 5.8% and 2.4%, respectively, which improves the accuracy compared with existing research, indicating that the shrinkage model has a good performance in predicting shrinkage of the typical structure in hollow thin-walled castings.
Nb, Ta and Zr are the favorable non-toxic alloying elements for titanium alloys for biomedical applications. Low rigidity titanium alloys composed of non-toxic elements are getting much attention. ...The advantage of low rigidity titanium alloy for the healing of bone fracture and the remodeling of bone is successfully proved by fracture model made in tibia of rabbit. Ni-free super elastic and shape memory titanium alloys for biomedical applications are energetically developed. Titanium alloys for not only implants, but also dental products like crowns, dentures, etc. are also getting much attention in dentistry. Development of investment materials suitable for titanium alloys with high melting point is desired in dental precision castings. Bioactive surface modifications of titanium alloys for biomedical applications are very important for achieving further developed biocompatibility. Low cost titanium alloys for healthcare goods, like general wheel chairs, etc. has been recently proposed.
다이캐스팅 공정은 다양한 산업군의 인프라 역할을 수행하는 중요한 공정이지만, 높은 불량률로 인하여 관련 기업들의 수익성 및 생산성의 한계가 있는 상황이다. 이를 타개하기 위하여, 본 연구에서는 다이캐스팅 공정의 불량 검출을 위한 산업인공지능 기반모듈을 구성하였다. 개발된 불량 검출 모듈은 제공되는 데이터의 특징에 따라서 3단계로 동작되는 모델로 구성된다. ...1단계 모델은 비지도학습 기반 이상 검출을 진행하며, 레이블이 없는 데이터셋을 대상으로 작동한다. 2단계 모델은 반지도학습 기반으로 이상 검출을 진행하며, 양품 데이터의 레이블만 존재하는 데이터셋을 대상으로 작동하며, 3단계 모델은 소수의 불량 데이터가 제공된 상황의 지도학습 모델을 기반으로 작동한다. 개발된 모델은 실제 다이캐스팅 양품 데이터를 바탕으로 96% 이상의 우수한 양품 검출성능을 보였다.
The die-casting process is an important process for various industries, but there are limitations in the profitability and productivity of related companies due to the high defect rate. In order to overcome this, this study has developed die-casting fault detection modules based on industrial AI technologies. The developed module is constructed from three-stage models depending on the characteristics of the dataset. The first-stage model conducts fault detection based on supervised learning from the dataset without labels. The second-stage model realizes one-class classification based on semi-supervised learning, where the dataset only has production success labels. The third-stage model corresponds to fault detection based on supervised learning, where the dataset includes a small amount of production failure cases. The developed fault detection module exhibited outstanding performance with roughly 96% accuracy for actual process data.
The purpose of this study was to combine simulations and experiments in order to present the first stage of construction in product lifecycle management. Based on the simplification of casting ...models, the relationship between the filling and solidification characteristics, casting methods, and geometrical classifications of aluminum alloy precision casting products was investigated. By rearranging and summarizing the data, the casting models could be digitally managed; moreover, the digitized data could be used as the basis for intelligent processes in further developments. The simulations calculated and analyzed the casting speeds, defect locations, material densities, and critical fraction of a solid A356 aluminum–silicon alloy; the actual casting was carried out and samples were taken for metallographic observation to confirm the simulation results. The part model was simplified with four basic geometric shapes: solid cylinder, tubular, block rectangle, and thin-shell rectangle. The 150 casting models were summarized using 37 combinations, which were further classified into five main categories to match the casting method: solid cylindrical, tubular, and thin-shell rectangular for side casting, and discoidal and plate rectangular for bottom casting. File-compression rates of up to 75% were achieved after classification and archiving, and data integrity was maintained. Finally, model training using random forest classification resulted in an 88.8% accuracy when predicting the casting method. This research is based on the practical issues raised by business owners and R&D engineers, and a solution was obtained. From the perspective of product lifecycle management, the results of this study show the consistency and uniformity of product design rules, as well as the reusability of product process planning, which can be integrated with carbon emissions trading and carbon taxes to save energy and achieve corporate sustainability.
CoCrMo alloys are known for their biocompatible properties, which, together with their favorable mechanical properties, mean they can be efficiently used in dentistry. With the development of ...selective laser melting for the fabrication of 3D printed objects, interest in the corrosion properties of this alloy has risen in the field of prosthodontics. In the study, CoCrMoW dental alloys were studied in artificial saliva at body temperature i.e. 37 °C. Different forms of CoCrMoW alloy were selected: a reference sample, i.e. original material as-received from the supplier, a casted sample acquired from an ordinary procedure in a dental laboratory, and two 3D printed samples made from CoCrMoW powder using the selective laser melting method (SLM). Electrochemical, spectroscopic and hardness measurements were conducted. It was shown that the reference and cast samples have similar microstructural and electrochemical properties, while the electrochemical properties of the 3D printed samples differ, most probably due to the effect of the higher micro porosity and chemical composition of the alloys.
The main commercial method of preparing precision metal parts with a high surface finish, for example, the blades of a turbo-ram jet engine, is lost waste casting. On preparing a wax model, a ceramic ...immuring element (rod) is placed in side the model in order to form cavities of complex shape, intended to reduce the mass of the casting and for forming channel of the cooling system of the blades cooled by the secondary air flow after a rod is removed. The main technological problems on removal of the inner rods are their strength and high chemical inertness, as a result of which their removal time and labor costs are quite large. This article investigates a method of preparing ceramic rods whose strength is not uniform along depth, which makes it possible, first of all, to remove (quite easily) the soft center and then to dissolve the stronger periphery.
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