Residual stresses after orthogonal machining of AlSl 304: numerical calculation of the thermal component and comparison with experimental results

1992 ◽  
Vol 23 (3) ◽  
pp. 989-996 ◽  
Author(s):  
Christoph Wiesner
Keyword(s):  
Numerical Calculation ◽  
Residual Stresses ◽  
Experimental Results ◽  
Thermal Component ◽  
Orthogonal Machining

Fracture Morphology and Residual Stresses of TiAl-Based Alloys Sheet Fabricated by EB-PVD

2006 ◽  
Vol 324-325 ◽  
pp. 307-310
Author(s):  
De Ming Zhang ◽  
Gui Qing Chen ◽  
Chun Mei Zhang ◽  
Jie Cai Han
Keyword(s):  
Free Surface ◽  
Numerical Calculation ◽  
Tensile Stress ◽  
Residual Stresses ◽  
Intergranular Fracture ◽  
Cleavage Fracture ◽  
Vacuum Annealing ◽  
Fracture Morphology ◽  
Columnar Crystal ◽  
X Ray

The TiAl-based alloys sheet with 150 mm × 100 mm × 0.4 mm was fabricated successfully by using EB-PVD method. The fracture morphology and residual stresses of the sheet were analyzed by SEM, numerical calculation and X-ray stress analyzer. The results indicate that before stripping, the depositional layers have a higher compressive stress, and the substrate has a very lower tensile stress. For the isolated TiAl-based alloys sheet, the microstructure of as-deposited sheet is columnar crystal, and the residual stresses distribution on the free surface has a trend that its magnitude decreased gradually from center to edges. After vacuum annealing at 1273 K for 16 h, the columnar crystal transforms into the equiaxed, the residual stresses on the free surface are eliminated ultimately, and the fracture of the material is diverted from the manner of intergranular fracture to the mixed manner of intergranular fracture with cleavage fracture.

Finite Element Modeling for Prediction of Residual Stresses in Fiber Reinforced Metal Matrix Composites

1993 ◽  
Author(s):  
Partha Rangaswamy ◽  
N. Jayaraman
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Matrix Material ◽  
Unit Cell ◽  
Experimental Results ◽  
Matrix Composites ◽  
Layer Removal

Abstract In metal matrix composites residual stresses developing during the cool-down process after consolidation due to mismatch in thermal expansion coefficients between the ceramic fibers and metal matrix have been predicted using finite element analysis. Conventionally, unit cell models consisting of a quarter fiber surrounded by the matrix material have been developed for analyzing this problem. Such models have successfully predicted the stresses at the fiber-matrix interface. However, experimental work to measure residual stresses have always been on surfaces far away from the interface region. In this paper, models based on the conventional unit cell (one quarter fiber), one fiber, two fibers have been analyzed. In addition, using the element birth/death options available in the FEM code, the surface layer removal process that is conventionally used in the residual stress measuring technique has been simulated in the model. Such layer removal technique allows us to determine the average surface residual stress after each layer is removed and a direct comparison with experimental results are therefore possible. The predictions are compared with experimental results of an eight-ply unidirectional composite with Ti-24Al-11 Nb as matrix material reinforced with SCS-6 fibers.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

2021 ◽  
pp. 1-50
Author(s):  
Nejah Tounsi ◽  
Tahany El-Wardany
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Chip Morphology ◽  
Milling Process ◽  
Uncut Chip Thickness ◽  
Orthogonal Machining ◽  
Cutting Length ◽  
Sequential Cuts

Abstract Part I of these two-part papers will investigate the effect of three FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS), when down-milling small uncut chips with thickness in the micrometer range and finite cutting edge radius. They are: i) orthogonal cutting with the mean uncut chip thickness t, obtained by averaging the uncut chip thickness over the cutting length, ii) orthogonal cutting with variable t, which characterizes the down-milling process and which is imposed on a flat surface of the final workpiece, and iii) modelling the true kinematics of the down milling process. The appropriate constitutive model is identified through 2D FEM investigation of the effects of selected constitutive equations and failure models on the prediction of RS and chip morphology in the dry orthogonal machining of Ti6Al4V and comparison to experimental measurements. The chip morphology and RS prediction capability of these representations is assessed using the available set of experimental data. Models featuring variable chip thickness have revealed the transition from continuous chip formation to the rubbing mode and have improved the predictions of residual stresses. The use of sequential cuts is necessary to converge toward experimental data.

The Improvement of the Micro Torsional Mirror by a Reinforced Folded Frame

2000 ◽  
Author(s):  
Hung-Yi Lin ◽  
Weileun Fang
Keyword(s):  
Thin Film ◽  
Residual Stresses ◽  
Film Thickness ◽  
Experimental Results ◽  
Dynamic Loads ◽  
Inertia Force ◽  
Optical Performance ◽  
Thin Film Thickness ◽  
Static Loads ◽  
Dynamic Inertia

Abstract Stiffness of micromachined structures is limited by thin film thickness. Hence, static loads such as thin film residual stresses, or dynamic loads such as the inertia force could significantly deform the thinness micromachined torsional mirror. This work aims to stiffen the thin film micromachinined torsional mirror. The proposed torsional mirror exploits a reinforced frame to improve the stiffness of the mirror plate. Consequently, the mirror plate has less deformation no matter subject to the residual stresses or to the dynamic inertia force. In addition the reinforced frame stiffen the mirror without increasing the mass significantly. In application of this technique, the micro torsional mirror was fabricated through the integration of DRIE, conventional bulk and surface micromachining processes. The experimental results demonstrated that the proposed design significantly improves the flatness of the mirror plate in both static and dynamic conditions. Consequently, the optical performance of the micro torsional mirror was improved.

An Analysis of the Ultimate Strength of Deck Structures Under In-Plane Loads

1983 ◽  
Vol 20 (03) ◽  
pp. 230-251
Author(s):  
Ygal Shapir ◽  
Gregory J. White
Keyword(s):  
Residual Stresses ◽  
Ultimate Strength ◽  
Experimental Results ◽  
Correction Factors ◽  
Buckling Strength ◽  
Step Procedure ◽  
Simple Program ◽  
Mode Of Failure ◽  
Compressive Loads ◽  
Simple Flow

A step-by-step procedure for determining the mode of failure and the ultimate strength of ship deck structures under in-plane compressive loads is developed. A comparison of several analytical theories for the buckling strength of deck structures in the elastic and inelastic zones is presented and the reason for the approach taken at each step is explained. The final result is a simple flow chart for this procedure and an algorithm which is easily adapted to most computer systems. The procedure is compared with experimental results and a method for determining reasonable size factors of safety (or correction factors) to account for initial deflections, residual stresses, etc., is presented. An example coding in FORTRAN IV for use as a subroutine in larger programs, or as a simple program itself, is given. An example structure is solved to explain each of the steps of the procedure.

scholarly journals A Semianalytical Model for the Determination of Bistability and Curvature of Metallic Cylindrical Shells

2019 ◽  
Vol 3 (1) ◽  
pp. 22
Author(s):  
Pavlo Pavliuchenko ◽  
Marco Teller ◽  
Markus Grüber ◽  
Gerhard Hirt
Keyword(s):  
Residual Stresses ◽  
Shell Thickness ◽  
Cylindrical Shells ◽  
Model Verification ◽  
Experimental Results ◽  
Steel Shell ◽  
Diffraction Measurement ◽  
Stable States ◽  
Forming Process ◽  
Specific Distribution

Bistable metal shells with a fully closed unfolded geometry are of great interest as lightweight construction parts which could be transported without housing and unfolded at the construction place. In order to achieve the effect of bistability in metallic shells, residual stresses with a specific distribution along the shell thickness are necessary. These residual stresses can be introduced in bending processes. The tools with specific bending radii are used to influence the curvature of the shell in the different stable states and thus determine whether a completely closed profile can be achieved. In addition to the forming process, the shell thickness and the shell material have an effect on the achievable geometries and stability. In order to manufacture bistable metallic cylindrical shells from different materials and shell thicknesses, it is necessary to be able to determine a promising process sequence and corresponding bending radii in advance. For this reason, this article presents a semianalytical model for the calculation of bistability and final curvatures. This model is applied to an incremental die-bending process using two bending operations with bending radii of 6 to 12 mm and a 0.2 mm thick steel shell of grade 1.1274 (AISI 1095). The calculation results show that bistability cannot be reached for all combinations of the two bending radii. Moreover, the model indicates that a bistable and fully closed shell is only achieved for a bending radii combination of R1 = 6 mm and R2 = 6 mm. With the aim of model verification, experiments with a closed-die incremental bending tool were performed. Calculated and experimental results show good correlation regarding bistability and curvature. In addition, X-ray diffraction measurement of the residual stresses shows a good qualitative agreement regarding the calculated and experimental results.

A Further Study of Residual Stresses in Circumferential Welds

1973 ◽  
Vol 95 (4) ◽  
pp. 238-242 ◽  
Author(s):  
S. Vaidyanathan ◽  
H. Weiss ◽  
I. Finnie
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Base Metal ◽  
Filler Metal ◽  
Residual Stress Distribution ◽  
Experimental Results ◽  
Circumferential Welds ◽  
Single Pass ◽  
Full Penetration

The residual stress distribution for a circumferential weld between cylinders was obtained in a prior publication for a full penetration, single pass weld with no variation of alloy content across the weld. In the present work the approach is extended to cover a wider variety of weld conditions. It is shown that the effects of multipass welds, partial penetration welds, and welds with filler metal differing greatly in properties from the base metal can approximately be taken into account. Experimental results are presented to support the proposed method of analysis.

Effects of Scale and Configuration of Air Chamber of OWC Type WECs on Air Chamber Characteristics

2020 ◽  
Author(s):  
Tomoki Ikoma ◽  
Shota Hirai ◽  
Yasuhiro Aida ◽  
Koichi Masuda ◽  
Hiroaki Eto
Keyword(s):  
Numerical Calculation ◽  
Water Column ◽  
Wave Energy ◽  
Experimental Models ◽  
Experimental Results ◽  
Oscillating Water Column ◽  
Wave Energy Converters ◽  
Air Chamber ◽  
The Difference ◽  
Energy Converters

Abstract This paper describes scale effects and influence of configurations of oscillating water column type wave energy converters from model tests and theoretical calculations. Many researches regarding wave energy converters (WECs) have been conducted. The behavior of an oscillating water column of an OWC type WEC is complicated because of including wave-air-turbine interaction, and thus several issues remain. One of the issues is that influence of difference in scale between small scale experimental models and full scale models is unclear. It is important to understand its characteristics accurately to improve design technologies for such as complicated systems. In this study, we carried out forced oscillation tests using multiple scales and shapes of OWC models in still water, and measured the pressure inside the air chamber and the internal mean water level with a multi-line wave probe. The experimental models used have a box like air chamber or manifold type air chamber, and which scales were 1/1, 1/2 and 1/4.The difference of the two air chambers is an orifice or a duct to be inlet-outlet of air. As a result, the difference in scale and configuration of the air chamber affected the characteristics of the air chamber. In addition, as a result of numerical calculation using the linear potential theory and comparison with experimental results, the experimental results could be reproduced by numerical calculation. Besides, we could discuss the effects and the influences of the air chamber basically.

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