Steven D. Grossman and Richard Lindhe
Decisions on capital investments at both the progam level and the specific asset level should be made in the context of the objectives of an organization as a whole. The addition…
Abstract
Decisions on capital investments at both the progam level and the specific asset level should be made in the context of the objectives of an organization as a whole. The addition of a new product line or the acquisition of a machine should not be decided simply on the basis of a direct cost/benefit analysis that is related to the program or the asset alone. Instead, the investment decision should be considered on the basis of the long‐term plans of the organization.
This chapter looks at the development of the original contribution “Toward a Theory of Entrepreneurial Competency” in the 1995 volume of the Advances series. The reflection…
Abstract
This chapter looks at the development of the original contribution “Toward a Theory of Entrepreneurial Competency” in the 1995 volume of the Advances series. The reflection discusses the conceptual and career issues underlying that original work. What follows is a reflection on the impact of the original chapter and on the key concept of the competency of learning itself. Among major ideas that emerge from this analysis is that entrepreneurship education helps individuals develop self-concepts and the social roles of entrepreneurs, that the intersection of personality, learning style, and learning effectiveness could be a useful focus of future work, that reflection is an under-developed competency, that success-related competencies need to be the focus going forward, that the atemporality of entrepreneurship and competencies should be tested, that critical entrepreneurship competencies may be industry-specific, and that the relative weights of competencies also need to be considered.
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Jie Han, Jingjing Yang, Hanchen Yu, Jie Yin, Ming Gao, Zemin Wang and Xiaoyan Zeng
This paper aims to investigate the influence of laser energy density on microstructure and mechanical properties of the selective laser melted (SLMed) Ti6Al4V to complement the…
Abstract
Purpose
This paper aims to investigate the influence of laser energy density on microstructure and mechanical properties of the selective laser melted (SLMed) Ti6Al4V to complement the existing knowledge in additive manufacturing of Ti6Al4V for future application of selective laser melting (SLM) in fabricating Ti6Al4V parts.
Design/methodology/approach
Ti6Al4V alloy is fabricated by SLM by adopting various energy densities. Microstructures and mechanical properties of the Ti6Al4V deposited using different energy densities are characterized.
Findings
Both high relative densities and microhardness can be obtained in the optimized processing window. The decrease of martensite width and spacing can improve the microhardness on both XOY and XOZ sections when the applied EV (defined as the laser energy per unit volume) increases. The width of the columnar grain increases with EV, resulting in a stronger anisotropy in microhardness between XOY and XOZ sections. Residual tensile stresses exist in the SLMed Ti6Al4V and increase with an increasing EV. A tensile strength of 1,268 MPa, a yield strength of 1,030 MPa, and an elongation of 4% can be obtained by using the optimized range of EV.
Originality/value
The microstructure of SLMed Ti6Al4V is quantitatively analysed by measuring the size of columnar grains and the martensites. The anisotropy of microstructures and properties in SLMed Ti6Al4V is characterized and its dependence on laser energy density is established. The residual stress in SLMed Ti6Al4V is characterized and its dependence on laser energy density is established. An optimized processing window to deposit Ti6Al4V alloy by SLM is proposed.
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Dana H. Abdeen and Bruce R. Palmer
This paper aims to study the effect of processing parameters of an electron beam melting (EBM) machine on the surface roughness, critical pitting temperature and density of…
Abstract
Purpose
This paper aims to study the effect of processing parameters of an electron beam melting (EBM) machine on the surface roughness, critical pitting temperature and density of Ti-6Al-4V parts produced from the EBM machine.
Design/methodology/approach
In this study, statistically designed experiments were used to manufacture Ti-6Al-4V samples in the EBM machine under different process parameters of beam current, beam speed and offset focus. Surface roughness was measured for as-built samples using a 3D profilometer. Then, a potentiostatic test was conducted under 2.40 V vs saturated calomel electrode to determine the critical pitting temperature (CPT) in 3.5 per cent mass NaCl solution for the samples of different processing parameters. Next, density was measured for these samples. Finally, model equations were established to relate EBM’s process parameters to measured properties of surface roughness, CPT and density.
Findings
Results showed that offset focus had the main influence on surface roughness more than the beam current and the beam speed. Changing processing parameters did not affect corrosion behavior of EBM Ti-6Al-4V as CPT did not vary widely, although a slight effect on CPT values obtained from the beam current and the beam speed. Density was greatly affected by the offset focus more than the other parameters. It can be concluded that uniform and precise measurements of roughness and density are not achievable through this machine; only a range of these properties can be attained.
Originality/value
EBM machine produces 3D parts in a layer-based building process under high temperature and vacuum atmosphere. Due to the manufacturing technique and conditions, the resulting object has irregularities on the exterior surface and voids that are formed within the part, both of which affect samples’ properties like surface roughness, CPT and density. This study established model equations that can relate parts’ properties to processing parameters so that parts of specific properties are obtained to fit the application they are used for. For each property, ANOVA fits vs linear energy were also obtained.