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Article
Publication date: 8 October 2018

Clinton B. Morris, John M. Cormack, Mark F. Hamilton, Michael R. Haberman and Carolyn C. Seepersad

Microstereolithography is capable of producing millimeter-scale polymer parts having micron-scale features. Material properties of the cured polymers can vary depending on…

Abstract

Purpose

Microstereolithography is capable of producing millimeter-scale polymer parts having micron-scale features. Material properties of the cured polymers can vary depending on build parameters such as exposure. Current techniques for determining the material properties of these polymers are limited to static measurements via micro/nanoindentation, leaving the dynamic response undetermined. The purpose of this paper is to demonstrate a method to measure the dynamic response of additively manufactured parts to infer the dynamic modulus of the material in the ultrasonic range.

Design/methodology/approach

Frequency-dependent material parameters, such as the complex Young’s modulus, have been determined for other relaxing materials by measuring the wave speed and attenuation of an ultrasonic pulse traveling through the materials. This work uses laser Doppler velocimetry to measure propagating ultrasonic waves in a solid cylindrical waveguide produced using microstereolithography to determine the frequency-dependent material parameters of the polymer. Because the ultrasonic wavelength is comparable with the part size, a model that accounts for both geometric and viscoelastic dispersive effects is used to determine the material properties using experimental data.

Findings

The dynamic modulus in the ultrasonic range of 0.4-1.3 MHz was determined for a microstereolithography part. Results were corroborated by using the same experimental method for an acrylic part with known properties and by evaluating the natural frequency and storage modulus of the same microstereolithography part with a shaker table experiment.

Originality/value

The paper demonstrates a method for determining the dynamic modulus of additively manufactured parts, including relatively small parts fabricated with microstereolithography.

Details

Rapid Prototyping Journal, vol. 24 no. 7
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 9 July 2018

Nicholas Alexander Meisel, David A. Dillard and Christopher B. Williams

Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to…

Abstract

Purpose

Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to macroscale property changes, which must be understood to appropriately design for this additive manufacturing (AM) process. This paper aims to identify impacts on these composites’ viscoelastic properties due to changes in base material composition and distribution caused by incomplete dithering in small features.

Design/methodology/approach

Dynamic mechanical analysis (DMA) is used to measure viscoelastic properties of two base PolyJet materials and seven “digital materials”. This establishes the material design space enabled by voxel-by-voxel control. Specimens of decreasing width are tested to explore effects of feature width on dithering’s ability to approximate macroscale material properties; observed changes are correlated to multi-material distribution via an analysis of ingoing layers.

Findings

DMA shows storage and loss moduli of preset composites trending toward the iso-strain boundary as composition changes. An added iso-stress boundary defines the property space achievable with voxel-by-voxel control. Digital materials exhibit statistically significant changes in material properties when specimen width is under 2 mm. A quantified change in same-material droplet groupings in each composite’s voxel pattern shows that dithering requires a certain geometric size to accurately approximate macroscale properties.

Originality/value

This paper offers the first quantification of viscoelastic properties for digital materials with respect to material composition and identification of the composite design space enabled through voxel-by-voxel control. Additionally, it identifies a significant shift in material properties with respect to feature width due to dithering pattern changes. This establishes critical design for AM guidelines for engineers designing with digital materials.

Details

Rapid Prototyping Journal, vol. 24 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 13 June 2016

Mica Grujicic, Jennifer Snipes, S Ramaswami and Chian-Fong Yen

The weld region obtained during friction stir welding (FSW) of metallic materials (including aluminum alloys) contains typically well-defined zones, each characterized by…

Abstract

Purpose

The weld region obtained during friction stir welding (FSW) of metallic materials (including aluminum alloys) contains typically well-defined zones, each characterized by fairly unique microstructure and properties. The purpose of this paper is to carry out combined experimental and numerical investigations of the mechanical properties of materials residing in different weld zones of FSW joints of thick AA2139-T8 plates.

Design/methodology/approach

Within the experimental investigation, the following has been conducted: first, optical-microscopy characterization of the transverse sections of the FSW joints, in order to help identify and delineate weld zones; second, micro hardness field generation over the same transverse section in order to reconfirm the location and the extent of various weld zones; third, extraction of miniature tensile specimens from different weld zones and their experimental testing; and finally, extraction of a larger size tensile specimen spanning transversely the FSW weld and its testing. Within the computational investigation, an effort was made to: first, validate the mechanical properties obtained using the miniature tensile specimens; and second, demonstrate the need for the use of the miniature tensile specimens.

Findings

It is argued that the availability of weld-zone material mechanical properties is critical since: first, these properties are often inferior relative to their base-metal counterparts; second, the width of the weld in thick metallic-armor is often comparable to the armor thickness, and therefore may represent a significant portion of the armor exposed-surface area; and finally, modeling of the weld-material structural response under loading requires the availability of high-fidelity/validated material constitutive models, and the development of such models requires knowledge of the weld-material mechanical properties.

Originality/value

The importance of determining the mechanical properties of the material in different parts of the weld zone with sufficient accuracy is demonstrated.

Details

International Journal of Structural Integrity, vol. 7 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 28 August 2007

K.H. Low and Yuqi Wang

The paper aims to present a modeling method for multi‐layer, multi‐material printed circuit boards (PCBs) in both micro‐structure and board levels.

Abstract

Purpose

The paper aims to present a modeling method for multi‐layer, multi‐material printed circuit boards (PCBs) in both micro‐structure and board levels.

Design/methodology/approach

The method incorporates a multilayer finite element model that is established in two parts: the first part is an elasto‐plastic damaging model, which is presented to model metallic plies in the multi‐layer PCBs, while the second is a bi‐phase model for glass‐fiber/epoxy‐resin composite ply with fiber/matrix structure.

Findings

Numerous composite parts and complex material properties of multi‐layer PCBs complicate the reliability of the simulation. Therefore, the board level simulation and the micro‐structure modeling cannot be performed at the same time. A multi‐layer FEM code can solve this problem: with the use of bi‐phase and elasto‐plastic plies in this code, the micro‐structure and board‐level modeling for multi‐layer PCBs can be incorporated.

Research limitations/implications

With the implementation of a virtual boundary method, the current multi‐layer model can be combined with the unit‐cell modeling method to perform detailed analysis at the micro‐structure level.

Originality/value

This paper presents a method for multi‐layer PCB modeling at both the micro‐structure and board levels. It provides a way to individually design the fabric types and the properties of glass fibers, epoxy resin, and copper foil in PCBs, to meet specific reliability requirements. With the proposed modeling, the static and shock responses of optimized PCBs can be analyzed with less computation.

Details

Circuit World, vol. 33 no. 3
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 8 May 2007

Chung Hyuk Park and Bum‐Hee Lee

To propose a new haptic modeling and contact analysis algorithm (modified long element method (MLEM)) to efficiently model deformation, to estimate elasticity, and to…

Abstract

Purpose

To propose a new haptic modeling and contact analysis algorithm (modified long element method (MLEM)) to efficiently model deformation, to estimate elasticity, and to provide the characterization of contact with deformable objects, which is important in teleoperation and haptic system.

Design/methodology/approach

Widely used finite element method for haptic rendering and visualization of deformable objects has limitations in real‐time applications because of its massive calculations and the absence of physical modeling. Using long elements method (LEM), the authors propose the MLEM which is capable of real‐time deformation rendering and elasticity estimation with reliable physical modeling. The authors applied MLEM to a simple haptic system composed of the three‐link SNU DD‐robot and a force‐feedback joystick.

Findings

An efficient, real‐time haptic modeling for deformable objects has been developed. MLEM provides physically accurate deformation modeling in real time, and estimates the elasticity of objects at contact, providing contact characterization based on material properties.

Research limitations/implications

MLEM has been applied to SNU DD‐robot, and displayed real‐time haptic visualization in 2D space. It can be applied easily to any haptic system with force sensors, and may have impacts on the applications of teleoperation, robot‐aided surgery and human‐robot interaction.

Originality/value

This paper offers a practical tool to the engineers in the haptics field for visualization of deformation. The efficient algorithm of MLEM can be placed on any haptic system with force sensors, and will improve the efficiency and accuracy of teleoperated haptic systems with real‐time analysis of haptic contact.

Details

Industrial Robot: An International Journal, vol. 34 no. 3
Type: Research Article
ISSN: 0143-991X

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Article
Publication date: 1 April 1999

M.G. Firmstone, P.M. Bartholomew, D.J.J. Lowrie, S.H. Mannan and D.A. Hutt

The benefits of a “no flow” process have been well documented in the recent past. The limitations of the previously reported materials in current use have been overcome…

Abstract

The benefits of a “no flow” process have been well documented in the recent past. The limitations of the previously reported materials in current use have been overcome via a unique chemistry which can be tailored to the application. Room temperature storage, effective fluxing, coupled with minimal outgassing, and a choice of reworkability after reflow or, if rework is not required, a full cure, can now be achieved within a single materials technology. This paper describes the properties of the new family of materials compared to conventional post‐deposited underfills. The development sequence and the procedure for characterisation of material properties, including the evaluation of the effectiveness of the fluxing action on a range of solder alloys, is documented. A typical application is described, outlining how a minimum of two process steps can be eliminated and how improvements in materials handling, process robustness, and ultimate yield, have been realised. A simple rework regime is also proposed, and the almost “drop in replacement” aspect of the new material is discussed.

Details

Soldering & Surface Mount Technology, vol. 11 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 5 January 2015

Jae B. Kwak and Seungbae Park

The purpose of this paper was to study the combined effect of hygro and thermo-mechanical behavior on a plastic encapsulated micro-electro-mechanical systems (MEMS…

Abstract

Purpose

The purpose of this paper was to study the combined effect of hygro and thermo-mechanical behavior on a plastic encapsulated micro-electro-mechanical systems (MEMS) package during the reflow process after exposed to a humid environment for a prolonged time. Plastic encapsulated electronic packages absorb moisture when they are subjected to humid ambient conditions.

Design/methodology/approach

Thus, a comprehensive stress model is established for a three-axis accelerometer MEMS package, with detailed considerations of fundamentals of mechanics such as heat transfer, moisture diffusion and hygro-thermo-mechanical stress. In this study, the mold compound is considered to be the most critical plastic material in MEMS package. Other plastic components of thin film materials can be disregarded due to their small sizes such as die attach and Bismaleimide Triazine (BT) core, even though they are also susceptible to moisture. Thus, only the moisture-induced properties of mold compound were obtained from the proposed experiments. From the desorption measurement after preconditioning at 85°C/85 per cent relative humidity (RH), the saturated moisture content and diffusivity were obtained by curve fitting the data to Fick’s equation. In addition, a new experimental setup was devised using the digital image correlation system together with a precision weight scale to obtain the coefficient of hygroscopic swelling (CHS) at different temperatures.

Findings

The experimental results show that the diffusion coefficient of mold compound material follows Arrhenius equation well. Also, it is shown that the CHS of mold compound increases as temperature increases. Experimentally obtained moisture properties were then used to analyze the combined behavior (thermo-hygro-mechanical) of fully saturated MEMS package during the reflow process using a finite element analysis (FEA) with the classical analogy method. Finally, the warpage and stresses inside the MEMS package were analyzed to compare the effects of hygroscopic, thermal and hygro-thermo-mechancal behaviors.

Originality/value

In this study, unlike the other researches, the moisture effects are investigated specifically for MEMS package which is relatively smaller in scale than conventional electronic packages. Also, as a conjugated situation, MEMS package experiences both humid and temperature during the moisture resistance test. Thus, major objective of this study is to verify stress state inside MEMS package during the reflow process which follows the preconditioning at 85°C/85 per cent RH. To quantify the stresses in the package, accurate information of material properties is experimentally obtained and used to improve modeling accuracy.

Details

Microelectronics International, vol. 32 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Content available
Article
Publication date: 1 June 2003

Abstract

Details

Circuit World, vol. 29 no. 2
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 11 July 2019

Dilek Bulut, Tatjana Krups, Gerhard Poll and Ulrich Giese

Elastomer seals are used in many applications. They are exposed to lubricants and additives at elevated temperatures, as well as mechanical stresses. They can only provide…

Abstract

Purpose

Elastomer seals are used in many applications. They are exposed to lubricants and additives at elevated temperatures, as well as mechanical stresses. They can only provide good sealing function when they have resistance to those factors. There are many elastomer-lubricant compatibility tests based on DIN ISO 1817 in industry. However, they are insufficient and costly. Correlations between the tests and the applications are inadequate. The purpose of this study is investigating lubricant compatibility of fluoroelastomers (FKM) seals in polyethylene-glycol (PG)- and polyalphaolefin (PAO)- based synthetic oils and developing a methodology to predict seal service life.

Design/methodology/approach

A new compatibility test which is more sufficient in terms of time and cost was developed and compared with a standard test, currently used in industry. Compatibility of FKM radial lip seals with PG- and PAO-based synthetic oils with different additives was investigated chemically and dynamically. Failure mechanisms were examined.

Findings

The new method and the Freudenberg Flender Test FB 73 11 008 showed similar results concerning damages and similar tendencies regarding wear. The additive imidazole derivative was the most critical. Static tests give indications of possible chemically active additives, but alone they are insufficient to simulate the dynamic applications.

Originality/value

The paper describes a new method to investigate elastomer-lubricant compatibility and gives first results with a variety of lubricants.

Details

Industrial Lubrication and Tribology, vol. 72 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 8 August 2016

Sohrab Astaraki

The purpose of this paper is to quantify uncertainty design parameters of long service usage material and including their effects explicitly in analysis of fracture…

Abstract

Purpose

The purpose of this paper is to quantify uncertainty design parameters of long service usage material and including their effects explicitly in analysis of fracture toughness for evaluation of reliability indexes.

Design/methodology/approach

In this paper structural reliability algorithm was incorporated into comprehensive finite element software. In this algorithm, the limit state function and relative gradient of uncertainty parameters has been determined using finite element model.

Findings

Results from this paper show that the effect of material degradation due to long service usage on the Young’s modulus for corroded samples and non-corroded samples are approximately 5 and 2.5 percent below the handbook value, respectively. The uncertainty in Young’s modulus is small, the randomness is unsymmetrical, and the dispersion is more above the mean than below the mean. The failure probability increases with the increasing uncertainty of Young’s modulus, and can be much larger than the probabilities calculated for a deterministic elasticity.

Originality/value

Reliable structural analysis of aging aircraft is crucial of safe operation.

Details

International Journal of Structural Integrity, vol. 7 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

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