Carl D. Sorensen

Overview of transient liquid phase and partial transient liquid phase bonding

Transient liquid phase (TLP) bonding is a relatively new bonding process that joins materials using an interlayer. On heating, the interlayer melts and the interlayer element (or a constituent of an alloy interlayer) diffuses into the substrate materials, causing isothermal solidification. The result of this process is a bond that has a higher melting point than the bonding temperature. This bonding process has found many applications, most notably the joining and repair of Ni-based superalloy components. This article reviews important aspects of TLP bonding, such as kinetics of the process, experimental details (bonding time, interlayer thickness and format, and optimal bonding temperature), and advantages and disadvantages of the process. A wide range of materials that TLP bonding has been applied to is also presented. Partial transient liquid phase (PTLP) bonding is a variant of TLP bonding that is typically used to join ceramics. PTLP bonding requires an interlayer composed of multiple layers; the most common bond setup consists of a thick refractory core sandwiched by thin, lower-melting layers on each side. This article explains how the experimental details and bonding kinetics of PTLP bonding differ from TLP bonding. Also, a range of materials that have been joined by PTLP bonding is presented.

Including Geometric Feature Variations in Tolerance Analysis of Mechanical Assemblies

Geometric feature variations are the result of variations in the shape, orientation or location of part features as defined in ANSI Y14.5M-1982 tolerance standard. When such feature variations occur on the mating surfaces between components of an assembly, they affect the variation of the completed assembly. The geometric feature variations accumulate statistically and propagate kinematically in a similar manner to the dimensional variations of the components in the assembly.The direct linearization method (DLM) for assembly tolerance analysis provides a means of estimating variations and assembly rejects, caused by the dimensional variations of the components in an assembly. So far no generalized approach has been developed to include all geometric feature variations in a computer-aided tolerance analysis system.This paper introduces a new, generalized approach for including all the geometric feature variations in the tolerance analysis of mechanical assemblies. It focuses on how to characterize geometri...

Transformation and Deformation Texture Study in Friction Stir Processed API X80 Pipeline Steel

The nature of deformation in friction stir welding/processing (FSW/P) is complex which is further complicated when allotropic phase transformations are present. Electron backscattered diffraction (EBSD) is used as a means to reconstruct prior austenite texture and grain structure to study deformation and recrystallization in austenite and ferrite in FSW/P of high strength low alloy (HSLA) steels. Analyses show evidence of shear deformation textures such as A1* (111)[−1−12], B (1−12)[110], and −B (−11−2)[−1−10], as well as rotated-cube recrystallization texture in the reconstructed prior austenite. Existence of rotated-cube texture as well as polygonal grain structure of the prior austenite implies that recrystallization is partially occurring in elevated temperatures. Room temperature ferrite exhibits well-defined shear deformation texture components. The observed shear deformation texture in the room temperature microstructure implies that FSW/P imposes deformation during the phase transformation. The evolution of both elevated and room temperature textures in friction stir processed API X80 steel are presented.

Integrated product and process design: a capstone course in mechanical and manufacturing engineering

A senior capstone design course entitled Integrated Product and Process Design has been jointly developed and taught at Brigham Young University by faculty from the departments of both mechanical and manufacturing engineering. The course features a structured approach to product and process design based on the Quality Function Deployment system. Teams of four to five students from both mechanical and manufacturing engineering work on selected, industrially sponsored design projects. These projects require both design and manufacturing solutions. The students are required to develop both functional prototypes and manufacturable production samples. An industrial environment is fostered in the course. The content of the course and an evaluation of its effectiveness are discussed.<<ETX>>

Analysis of variant selection in friction‐stir‐processed high‐strength low‐alloy steels

Variant selection in friction-stir-welded high-strength low-alloy steels has been studied using the electron backscatter diffraction and prior austenite (PA) reconstruction techniques described in previous papers. A hypothesis for variant selection has been proposed based on grain-boundary interfacial energy and misorientation. This study focuses on austenite 〈111〉 boundaries with a two-dimensional approach. Results indicate that variant selection is strongly dependent on misorientation. Certain PA misorientations produce combinations of variants that minimize the interfacial energies between a ferrite nucleus and a neighboring austenite grain, and between adjoining ferrite nuclei along the boundary between two PA grains. PA grains that exhibit a 60° 〈111〉 misorientation between them satisfy both these conditions for a combination of variants. These PA boundaries exhibit strong variant selection. As a result, the density of these boundary types influences the overall variant selection. Additionally, variant selection is more prevalent in small PA grains (<150 µm), which is probably a result of limited intragranular nucleation. Nearly all variants are present in larger PA grains.

Variation Analysis of Tooth Engagement and Loads in Involute Splines

Involute spline couplings are used to transmit torque from a shaft to a hub or other rotating component. In theory, all teeth of the spline share the load equally. In practice, due to manufacturing variations, the teeth are unequally loaded. A new model for tooth engagement, based on statistics, predicts that the teeth engage in a sequence, determined by the individual clearances. As the shaft load is applied, the tooth pair with the smallest clearance engages first, then deflects as the load increases, until the second pair engage. The two engaged pairs deflect together until the third pair engage, and so on, until the full load is reached. The statistical model predicts the average number of teeth which will engage for a specified load, plus or minus the expected variation. It also quantitatively predicts the load and stress in each engaged pair. Critical factors in the model are the stiffness and deflection of a single tooth pair and the characterization of the clearance. Detailed finite element analyses were conducted to verify the tooth deflections and engagement sequence. This model has led to a simple closed-form solution that has been implemented in a spreadsheet to allow designers to predict the load in spline teeth based upon the characteristics of the spline.

Advances in Temperature Control for FSP

A temperature control algorithm has been developed that contains an inner loop to control power and an outer loop to command power based on temperature feedback. The foundation of the control algorithm used in this work is the fact that spindle power leads tool temperature. This fact will be proven through analytical models and experimental data. Commanding spindle power to control temperature is a significant paradigm shift for some members of the friction stir processing (FSP) community.

System Parameter Identification for Friction Stir Processing

Temperature control has been implemented in Friction Stir Processing and has demonstrated the ability to give improved process control. In order to have optimal control of the process, the parameters of the system must be accurately identified. The system parameters change with tool geometry and materials, workpiece materials, and workpiece holding system. This paper presents the use of the relay feedback test to determine the thermal parameters of the F SP system. The relay feedback test is easy to use and promotes system stability during its use. The results from the relay feedback test can be used to establish tuning constants for a feedback temperature control. The use of this method, as well as the quality of the resulting control is demonstrated in this paper.

A new technique for modelling production control schemes in manufacturing systems

This paper presents a new modelling technique to model continuous manufacturing systems. The new dynamic model is based on analogies with electrical systems, and it has the capability to explicitly specify production control schemes including control points, material and information flow paths, and logical operations. The electrical analogues provide an excellent tool to model control signals and logical operations. This is especially important for pull control schemes where qualitative descriptions often found in the literature can be ambiguous. The model provides standard graphical representations and governing equations to describe both the steady state and transient responses of continuous manufacturing systems. For deterministic systems, these equations can be solved to obtain closed-form solutions. For stochastic systems, numerical solutions can be obtained for any probabilistic distribution. The proposed technique is demonstrated by modelling push and a variety of pull systems.

Strategies for developing robust teamsmanship in the context of design education for product development: A progress report

A conceptual model that provides a framework for developing strategies to improve the performance of student teams has been developed. The model is dynamic and covers the time-dependent states that are essential for the proposed criterial of successful team-based design project experience for students. The states of design progress, team development, and knowledge acquisition can be moved to desired values at project conclusion by measurement and comparison with desired values. The main energy for moving the states is derived from the team efforts that are internally directed through the primary, single-loop feedback structure. Secondary energy is derived from coaches and instructors through interventions that are directed as part of an external secondary, or double-loop structure. Interventions include instruction in the whole process and specification of a design activity schedule. This aggressive activity schedule sets up an environment that provides tension for the team to move the states toward improved values.<<ETX>>