Finite Element Modeling of Residual Stress at Joint Interface of Titanium Alloy and 17-4PH Stainless Steel

Residual stress is a crucial element in determining the integrity of parts and lifetime of additively manufactured structures. In stainless steel and Ti-6Al-4V fabricated joints, residual stress causes cracking and delamination of the brittle intermetallic joint interface. Knowledge of the degree of residual stress at the joint interface is, therefore, important; however, the available information is limited owing to the joint’s brittle nature and its high failure susceptibility. In this study, the residual stress distribution during the deposition of 17-4PH stainless steel on Ti-6Al-4V alloy was predicted using Simufact additive software based on the finite element modeling technique. A sharp stress gradient was revealed at the joint interface, with compressive stress on the Ti-6Al-4V side and tensile stress on the 17-4PH side. This distribution is attributed to the large difference in the coefficients of thermal expansion of the two metals. The 17-4PH side exhibited maximum equivalent stress of 500 MPa, which was twice that of the Ti-6Al-4V side (240 MPa). This showed good correlation with the thermal residual stress calculations of the alloys. The thermal history predicted via simulation at the joint interface was within the temperature range of 368–477 °C and was highly congruent with that obtained in the actual experiment, approximately 300–450 °C. In the actual experiment, joint delamination occurred, ascribable to the residual stress accumulation and multiple additive manufacturing (AM) thermal cycles on the brittle FeTi and Fe2Ti intermetallic joint interface. The build deflected to the side at an angle of 0.708° after the simulation. This study could serve as a valid reference for engineers to understand the residual stress development in 17-4PH and Ti-6Al-4V joints fabricated with AM.

Proposal of quantitative and qualitative metrics to assess affective user-centered design of video games

The experience which emerges from digital games has, above all, an emotional nature, so evaluating the user experience only through objective factors does not seem to be sufficient for the analysis of a game as it is an entertainment product. This article intends to propose a set of metrics that allow evaluating affective, or roughly speaking, emotional aspects of the user experience from digital games. The metrics are applied to a list, found in a related work, of relevant game design components that affect the subjective experience of gaming. The intended experiment in the future is a gameplay session of a game especially designed to include a system that measures in background, through the proposed metrics, players’ actions in the gaming experience. The result in this paper is a set of quantitative and qualitative metrics that will assess players’ choices in the actual experiment and that yield numerical outcomes, even though the analyzed factors are subjective.

Data processing method for constitutive relation of the rubber core material in spherical blowout preventer

A data processing method for constitutive relation of large deformation rubber core in spherical blowout preventer is put forward in this article. Based on the Yeoh constitutive model and the large-deformation theory of rubber material, this article studied the constitutive relation of core material in blowout preventer. The constitutive relation experiments, the uniaxial tensile experiment, the uniaxial compression experiment, the plane tensile experiments, and the volume compression experiment were conducted and the corresponding experiment data were fitted, respectively, on basis of which the uniaxial compression data were selected for further study. For comparison, the data were, respectively, processed with a novel method and the method in GB/7757, and accordingly, two different constitutive relations were obtained and introduced into ABAQUS to simulate the experiment process. Research results show that the relative error of maximum axial deformation between the simulation using GB/7757 and the actual experiment is 34.7%, while that between the novel method and the actual experiment is 20.4%, having improved the accuracy by 14.3%, proving that the data processing method in this article can effectively improve the accuracy of finite element simulation for the core material and will contribute to the research on the performance of spherical blowout preventer.

Test First Model for Application in the Academic Setting

This research elaborates the selection of the Test First and Test Last model for a pilot experiment that was executed as a feasibility study to validate the suitability of the existing Test First model for its implementation in the series of actual experiment. The series of actual experiment is designed to investigate the quality of the project developed by the students in higher educational institution with the Test First over Test Last model. The findings gathered from the pilot experiment demonstrate that there were misunderstandings on the user stories among the participants that have led to the development of an enhanced Test First model.

Experimental Study of Stochastic Processes, Determining their Characteristics and Conducting Real Experiments on the Operated Bridge

The paper describes the process of actual experiment for practical confirmation of the effectiveness of new technologies. New software is proposed for investigating a real stochastic process. Technology and software are designed for fast calculation, analysis of adequate estimates of statistical characteristics, confirming the effectiveness of suggested technology, with high accuracy.

Estimating Neighborhood Choice Models: Lessons from a Housing Assistance Experiment

We use data from a housing-assistance experiment to estimate a model of neighborhood choice. The experimental variation effectively randomizes the rents which households face and helps identify a key structural parameter. Access to two randomly selected treatment groups and a control group allows for out-of-sample validation of the model. We simulate the effects of changing the subsidy-use constraints implemented in the actual experiment. We find that restricting subsidies to even lower poverty neighborhoods would substantially reduce take-up and actually increase average exposure to poverty. Furthermore, adding restrictions based on neighborhood racial composition would not change average exposure to either race or poverty. (JEL I32, I38, R23, R38)

Casting Process and Simulation of K19 Cylinder Block

Cylinder blocks are the most important parts of engine, and their qualities will fundamentally determine the efficiency of engine. In this work, the casting process of K19 engine cylinder block was studied. A casting process was designed and assessed by the numerical software MAGMA to produce cylinder block castings. An actual experiment of casting was carried out and the mechanical properties of the casting were examined. The simulation results show the liquid metal smoothly fills the casting mold and no shrinkage cavity and porosity are formed in the castings. The cylinder block produced by the actual experiment exhibits superior mechanical properties to common ones, which proves the casting process designed is suitable for producing high quality cylinder block castings. The research shows that numerical simulation can provide very useful guidance for the production of castings

Dynamic Analysis of a 3-DOF Parallel Mechanism Based on Kane Equations

The Kane equations were applied in the dynamic analysis of a 3-DOF parallel mechanism, whose sub-chains consisted of three pairs of parallel legs. According to the characteristic of the parallel mechanism, it was simplified to 3PSS structure. Dynamics equations were derived based on the kinematical analysis. Computing simulation example was presented through MATLAB programming and verified by ADAMS simulation. The results showed that the approach was correct. It provides theoretical reference for the actual experiment and the choice of subsequent control method.