Failure Studies on Flow Formed High Strength Pressure Vessel: A Case Study

2003 ◽  
Vol 125 (3) ◽  
pp. 253-259 ◽  
Author(s):  
K. M. Rajan ◽  
K. Narasimhan
Keyword(s):  
Tensile Strength ◽  
High Stress ◽  
High Strength ◽  
Thickness Reduction ◽  
Flow Forming ◽  
High Stress Concentration ◽  
Micro Cracks ◽  
Aisi 4130 ◽  
As Stress ◽  
Stress Raisers

High strength thin walled flow formed tubes are manufactured from AISI 4130 medium carbon low alloy steel. Starting with an ultimate tensile strength of 650 MPa, the material has recorded a tensile strength of 1250–1300 MPa corresponding to a percentage thickness reduction of 88. It has been observed that material with higher impurity levels and inclusion ratings are more vulnerable to development of micro cracks at higher percentage thickness reduction. Deformed inclusions like MnS act as stress raisers leading to initiation of micro cracks. Hard to deform inclusions like silicates create high stress concentration at inclusion-matrix interface, leading to de-cohesion and finally cracking. The presence of dissolved gas contents, particularly hydrogen, are harmful in flow forming. Hydrogen embrittlement is a serious problem which is likely to lead to cracking of the flow formed tube. It could be concluded from this study that clean steel (electro slag refined) processed through hardening and tempering route with a maximum percentage reduction in thickness of 88 or less can give consistently very high strength of the order of 1250–1300 MPa for AISI 4130 steel.

INLAND DURASPRING

Alloy Digest ◽  
1998 ◽  
Vol 47 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Tensile Properties ◽  
High Stress ◽  
High Strength ◽  
Spring Steel ◽  
Fatigue Properties ◽  
Light Truck ◽  
Suspension Systems ◽  
Spring Steels

Abstract Inland DuraSpring is a high-strength microalloyed spring steel for use in high stress coil springs for automobile and light truck suspension systems. This bar product offers significant improvements in tensile strength, fatigue properties, and fracture toughness compared to conventional spring steels. This datasheet provides information on composition, hardness, and tensile properties as well asfracture toughness and fatigue. Filing Code: SA-496. Producer or source: Ispat Inland Inc.

An Experimental Study of Cavity Nucleation During Superplastic Deformation

1990 ◽  
Vol 196 ◽  
Author(s):  
Jiang Xinggang ◽  
Cui Jianzhong ◽  
Ma Longxiang
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Thermomechanical Processing ◽  
High Stress ◽  
High Strength ◽  
Optical Microscope ◽  
Grain Boundary Sliding ◽  
Cavity Nucleation ◽  
High Stress Concentration ◽  
Voltage Electron

ABSTRACTCavity nucleation during superplastic deformation of a high strength aluminium alloy has been studied using a high voltage electron microscope and an optical microscope. The results show that cavities nucleation is due only to superplastic deformation and not to pre-existing microvoids which may be introduced during thermomechanical processing. The main reason for cavity nucleation is the high stress concentration at discontinuties in the plane of the grain boundary due to grain boundary sliding.

Underfill Design for Low-k Dielectrics and Lead Free Applications

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001465-001485
Author(s):  
Brian Schmaltz ◽  
Yukinari Abe ◽  
Kazuyuki Kohara
Keyword(s):  
Stress Concentration ◽  
Dielectric Layer ◽  
Failure Modes ◽  
High Stress ◽  
High Strength ◽  
Lead Free ◽  
Typical Result ◽  
High Stress Concentration ◽  
Technology Nodes ◽  
Low K

As technology nodes progress to 32/28nm and beyond underfill materials are presented with the significantly challenging task of maintaining bump protection while ensuring ultra low-K dielectric (ULK/ELK) integrity. This challenge is further complicated by the trend toward RoHS compliancy(lead-free) and a ever increasing die size. Through extensive research and testing, several specifically formulated underfill materials were determined acceptable solutions for these complex issues. As technology nodes progress to smaller process generations a high stress concentration is seen at the dielectric layer during thermal cycling. This stress is a typical result of a high glass transition temperature (Tg) / high strength material that often leads to a cracking failure mode of the thin dielectric layer. Too low of a Tg presents a high stress concentration on the bumps which once again constitutes failure, this time however the crack is typically seen at the bump location. This high stress concentration seen at the bumps is more significant when lead free bumps are considered due to their inherent fragile nature. Underfill materials must now be specifically formulated and optimized to solve these failure modes for a large variable of package types. This paper will discuss solutions to typical failure modes currently seen with reliability testing of present and future technologies.

A study of the deformation and fracture of single-crystal gold films of high strength inside an electron microscope

1960 ◽  
Vol 255 (1281) ◽  
pp. 218-231 ◽  
Keyword(s):  
Plastic Deformation ◽  
Tensile Strength ◽  
Electron Microscope ◽  
Single Crystal ◽  
High Stress ◽  
High Strength ◽  
Gold Wire ◽  
Detailed Examination ◽  
Stress Concentrations ◽  
High Stress Level

Single-crystal films of gold in (111) orientation, and 500 to 2000 Å in thickness, have been prepared by an evaporation technique. A device has been constructed to allow these films to be strained in a controlled manner while under observation inside the electron microscope (Siemens Elmiskop I). It is shown, by the absence of observable plastic deformation, that the films deform elastically up to abnormally high strain values. This is confirmed, in the case of 500 Å films, by precision electron diffraction measurements, which indicate elastic strains as high as 1 to 1·5%. This represents a tensile strength several times that of hard-drawn gold wire. The high tensile strength occurs despite the presence of a high density of dislocations. Failure occurs once the elastic limit is exceeded. Detailed examination of the fractured specimens reveals that highly localized plastic deformation occurs immediately before fracture. The nature of the fracture process has been deduced from the micrographs, and it is shown that the catastrophic failure occurs as a result of the high stress level which exists when plastic deformation occurs, coupled with the stress concentrations which occur as localized thinning takes place.

Fracture of Amorphous Polymeric Solids: Time to Break

1965 ◽  
Vol 38 (2) ◽  
pp. 263-277
Author(s):  
J. C. Halpin
Keyword(s):  
Tensile Strength ◽  
Stress Concentration ◽  
Nonlinear Response ◽  
Failure Process ◽  
High Stress ◽  
Viscoelastic Body ◽  
Simple Process ◽  
High Stress Concentration ◽  
Failure Theory ◽  
Fracture Theory

Abstract The failure theory of Bueche and Halpin is generalized and expanded to obtain a prediction of the time dependence of tensile strength and ultimate elongation. The model pictures rupture as propagation of tears or cracks within the material. The growth of a tear or crack is viewed as an ideally simple process in which the molecular chains at the tear tip stretch viscoelastically under the influence of a high stress concentration until they rupture. As a consequence, the failure process is a nonequilibrium one, developing with time and involving the consecutive rupture of the molecular chains. Substantial support for the theory is found by comparing the theoretical prediction with experimental results obtained for SBR and EPT. In addition, it is experimentally demonstrated that delayed and forced rupture experiments can yield qualitatively identical data for viscoelastic bodies. Also discussed is the basis for the approach to the nonlinear response of a viscoelastic body required here in the development of a fracture theory.

scholarly journals Nanoscale precipitates as sustainable dislocation sources for enhanced ductility and high strength

2020 ◽  
Vol 117 (10) ◽  
pp. 5204-5209 ◽  
Author(s):  
Shenyou Peng ◽  
Yujie Wei ◽  
Huajian Gao
Keyword(s):  
Lattice Mismatch ◽  
High Stress ◽  
High Strength ◽  
Material Design ◽  
Dislocation Nucleation ◽  
Precipitate Size ◽  
Unique Type ◽  
Dislocation Glide ◽  
High Stress Concentration ◽  
Dislocation Sources

Traditionally, precipitates in a material are thought to serve as obstacles to dislocation glide and cause hardening of the material. This conventional wisdom, however, fails to explain recent discoveries of ultrahigh-strength and large-ductility materials with a high density of nanoscale precipitates, as obstacles to dislocation glide often lead to high stress concentration and even microcracks, a cause of progressive strain localization and the origin of the strength–ductility conflict. Here we reveal that nanoprecipitates provide a unique type of sustainable dislocation sources at sufficiently high stress, and that a dense dispersion of nanoprecipitates simultaneously serve as dislocation sources and obstacles, leading to a sustainable and self-hardening deformation mechanism for enhanced ductility and high strength. The condition to achieve sustainable dislocation nucleation from a nanoprecipitate is governed by the lattice mismatch between the precipitate and matrix, with stress comparable to the recently reported high strength in metals with large amount of nanoscale precipitates. It is also shown that the combination of Orowan’s precipitate hardening model and our critical condition for dislocation nucleation at a nanoprecipitate immediately provides a criterion to select precipitate size and spacing in material design. The findings reported here thus may help establish a foundation for strength–ductility optimization through densely dispersed nanoprecipitates in multiple-element alloy systems.

A TEM microscopical investigation of the magnetic domain structure of a metastable austenitic stainless steel

1994 ◽  
Vol 52 ◽  
pp. 696-697
Author(s):  
G. Fourlaris ◽  
T. Gladman
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Cold Rolling ◽  
Solution Treatment ◽  
Magnetic Domain ◽  
High Strength ◽  
Medium Carbon Steel ◽  
Magnetic Characteristics ◽  
Metastable Austenitic Stainless Steel

Stainless steels have widespread applications due to their good corrosion resistance, but for certain types of large naval constructions, other requirements are imposed such as high strength and toughness , and modified magnetic characteristics.The magnetic characteristics of a 302 type metastable austenitic stainless steel has been assessed after various cold rolling treatments designed to increase strength by strain inducement of martensite. A grade 817M40 low alloy medium carbon steel was used as a reference material.The metastable austenitic stainless steel after solution treatment possesses a fully austenitic microstructure. However its tensile strength , in the solution treated condition , is low.Cold rolling results in the strain induced transformation to α’- martensite in austenitic matrix and enhances the tensile strength. However , α’-martensite is ferromagnetic , and its introduction to an otherwise fully paramagnetic matrix alters the magnetic response of the material. An example of the mixed martensitic-retained austenitic microstructure obtained after the cold rolling experiment is provided in the SEM micrograph of Figure 1.

DOGAL 600 and 800 DP

Alloy Digest ◽  
2010 ◽  
Vol 59 (12) ◽  
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
High Strength Steels ◽  
High Strength

Abstract Dogal 600 and 800 DP are high-strength steels with a microstructure that contains ferrite, which is soft and formable, and martensite, which is hard and contributes to the strength of the steel. The designation relates to the lowest tensile strength. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on forming, joining, and surface treatment. Filing Code: CS-160. Producer or source: SSAB Swedish Steel Inc. and SSAB Swedish Steel.

MEEHANITE GB300

Alloy Digest ◽  
2020 ◽  
Vol 69 (11) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Gray Cast Iron ◽  
High Strength ◽  
Heat Treating ◽  
Spheroidal Graphite ◽  
Cast Irons ◽  
Test Pieces ◽  
Temperature Performance

Abstract Meehanite GB300 is a pearlitic gray cast iron that has a minimum tensile strength of 300 MPa (44 ksi), when determined on test pieces machined from separately cast, 30 mm (1.2 in.) diameter test bars. This grade exhibits high strength while still maintaining good thermal conductivity and good machinability. It is generally used for applications where the thermal conductivity requirements preclude the use of other higher-strength materials, such as spheroidal graphite cast irons, which have inferior thermal properties. This datasheet provides information on physical properties, hardness, tensile properties, and compressive strength as well as fatigue. It also includes information on low and high temperature performance as well as heat treating, machining, and joining. Filing Code: CI-75. Producer or source: Meehanite Metal Corporation.

LESCALLOY 300M VAC ARC

Alloy Digest ◽  
1993 ◽  
Vol 42 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
High Strength ◽  
Melting Process ◽  
Heat Treating ◽  
Pressure Vessels ◽  
Low Alloy Steel ◽  
Steel Company ◽  
High Hardenability ◽  
Ingot Structure

Abstract LESCALLOY 300M VAC ARC is a low-alloy steel with an excellent combination of high hardenability and high strength coupled with good ductility and good toughness. Its tensile strength ranges from 280,000 to 300,000 psi. It is produced by the vacuum consumable electrode melting process to provide optimum cleanliness and preferred ingot structure. Its applications include aircraft components, pressure vessels and fasteners. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-321. Producer or source: Latrobe Steel Company. Originally published March 1976, revised February 1993.

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