비만아 부모의 돌봄 경험: q 방법론

Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

Wire Arc Additive Manufacturing (WAAM) is attracting significant attention in industry and academia due to its ability to capture the benefits of additive manufacturing for production of large components of medium geometric complexity. Uniquely, WAAM combines the use of wire and electric arc as a fusion source to build components in a layer-by-layer approach, both of which can offer significant cost savings compared to powder and alternative fusion sources, such as laser and electron beam, respectively. Meanwhile, a high deposition rate, key for producing such components, is provided, whilst also allowing significant material savings compared to conventional manufacturing processes. However, high quality production in a wide range of materials is limited by the elevated levels of heat input which causes a number of materials processing challenges in WAAM. The materials processing challenges are fully identified in this paper to include the development of high residual stresses, undesirable microstructures, and solute segregation and phase transformations at solidification. The thermal profile during the build poses another challenge leading to heterogeneous and anisotropic material properties. This paper outlines how the materials processing challenges may be addressed in WAAM by implementation of quality improving ancillary processes. The primary WAAM process selections and ancillary processes are classified by the authors and a comprehensive review of their application conducted. Strategies by which the ancillary processes can enhance the quality of WAAM parts are presented. The efficacy and suitability of these strategies for versatile and cost effective WAAM production are discussed and a future vision of WAAM process developments provided.

https://purehost.bath.ac.uk/ws/files/183236429/StrategiesAndProcessesForHighQualityWireArcAdditiveManufacturing_Manuscript.pdf

Invited review article: Strategies and processes for high quality wire arc additive manufacturing

Pb-free solders have replaced Pb-containing SnPb solders in the electronic packaging industry due to environmental concerns. Both electromigration (EM) and thermomigration (TM) have serious reliability issues for fine-pitch Pb-free solder bumps in the flip-chip technology used in consumer electronic products. We review the unique features of EM and TM in flip-chip solder bumps, emphasizing the effects of current crowding and Joule heating. In addition, the challenges to a better understanding of EM and TM in Pb-free solders are discussed. For example, the anisotropic nature of Sn microstructure in Pb-free solders can enhance the dissolution rates of Ni and Cu in solders driven by EM and TM.

https://ir.nctu.edu.tw:443/bitstream/11536/6094/1/000280818700021.pdf

Electromigration and Thermomigration in Pb-Free Flip-Chip Solder Joints

The objective of this review is to study the interfacial intermatallic compounds (IMCs) between Sn–Ag–Cu based solders and common substrates, which play a crucial role in solder joints typically present in Pb-free electronics manufacturing. The microstructural evolution of IMCs at the solder/substrate interfaces is analyzed, while the models and theories describing the formation/growth mechanism of interfacial IMCs are also introduced. We focus on the influence of a variety of factors that have been reported recently, including substrates, minor alloying, mechanical stress, electromigration and thermomigration etc., as full understanding of the mechanisms that determine the formation and growth of interfacial IMCs is important to reach for developing high reliability solder joints. In the end of this review, the characteristics of the IMCs are compared and illustrated, which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints.

A review on the interfacial intermetallic compounds between Sn–Ag–Cu based solders and substrates

Reduction of ductility-dip cracking susceptibility by ultrasonic-assisted GTAW

Comparison of residual stress induced by TIG and LBW in girth weld of AISI 304 stainless steel pipes

Prediction of welding deformation in stiffened structure by introducing thermo-mechanical interface element

Effect of Zn addition on the formation and growth of intermetallic compound at Sn–3.5 wt% Ag/Cu interface

Multi-scale simulation of nanoindentation on cast Inconel 718 superalloy and its NbC precipitate were performed with combined first principle study and crystal plasticity finite element method (CPFEM). The concerned parameters were calibrated through a representative volume element (RVE) model compared with the stress–strain curves obtained from tensile tests. Nanoindentation was carried out on the matrix. First principle calculations were applied to estimate the mechanical properties of precipitate NbC, including elastic modulus and hardness. The simulated force–displacement curves match well with the experimental results. The simulated results indicate that the local pile-up pattern in the indentation zone depends significantly on the crystallographic orientations. In addition, large precipitate NbC inserted in the matrix was also indented and simulated. The elastic modulus calculated by first principle is quite accurate while the yield stress is determined using inversion calculations. It appears that the proposed CPFE analysis approach combined with first principle calculation do help estimate the mechanical behavior of large precipitates on the Ni-based superalloy.

Hao Lu

Papers

Reduction of ductility-dip cracking susceptibility by ultrasonic-assisted GTAW

Comparison of residual stress induced by TIG and LBW in girth weld of AISI 304 stainless steel pipes

Prediction of welding deformation in stiffened structure by introducing thermo-mechanical interface element

Effect of Zn addition on the formation and growth of intermetallic compound at Sn–3.5 wt% Ag/Cu interface

Multi-scale simulation of nanoindentation on cast Inconel 718 and NbC precipitate for mechanical properties prediction