A New Experimental Technique for Dynamic Material Properties

2013 ◽  
Vol 690-693 ◽  
pp. 1872-1877
Author(s):  
Min Zu Liang ◽  
Xiang Yu Li ◽  
Fang Yun Lu ◽  
Jin Gui Qin
Keyword(s):  
High Strain Rate ◽  
Material Properties ◽  
High Intensity ◽  
High Strain ◽  
Tensile Loading ◽  
Low Density ◽  
Effective Technique ◽  
One Dimensional ◽  
Dynamic Material Properties ◽  
Properties Of Materials

An improved experimental method has been described to determine dynamic material properties under conditions approximating uniform one-dimensional tensile loading. A lateral efficiency loading is produced when the projectile, which is made of low-density material, impacts high-intensity target. The lateral efficiency loading technique is a convenient and effective technique to study the dynamic fracture and fragmentation properties of materials under high strain rate tensile loading.

High Strain Rate Compressive Properties of Soft Tissue

2003 ◽  
Author(s):  
Caleb R. Van Sligtenhorst ◽  
Duane S. Cronin ◽  
G. Wayne Brodland
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Fiber Orientation ◽  
Soft Tissues ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Post Mortem ◽  
Fresh Tissue

High strain rate material properties and constitutive equations are essential for the development of numerical and physical models to assess the performance of soft materials subject to high rate deformation, with potential applications including protective equipment and vehicle crashworthiness. However, these properties are not available for many soft tissues. This is because specialized testing methods must be employed to obtain the necessary data. Fresh bovine tissue from the semimembranosis muscle was obtained and tested using a polymeric Split Hopkinson Pressure Bar. Samples were tested from 1.4 to 200 hours post mortem to observe the effect of rigor and other possible temporal effects on the material properties. Since this muscle had relatively uniform fiber orientation, it was possible to obtain specimens with fiber directions parallel, perpendicular, and at 45 degrees to the compression axis. The stress-strain curves for the muscle were concave upwards, as is typical of soft tissues at high strain rates. Fiber orientation was determined to have negligible effect at the tested strain rates. The testing revealed that the stiffness of the tissue increased with post mortem time until approximately 6 hours. At times greater than 200 hours post mortem, the tissue properties were found to be very similar to the properties of fresh tissue. These findings suggest that properties of fresh tissue might be estimated using more easily obtained post-rigor tissue.

High Strain Rate Constitutive Modeling of Pure Titanium Using the Taylor Impact Test

2014 ◽  
Author(s):  
Mark E. Barkey ◽  
Haleigh Ball ◽  
Stanley E. Jones ◽  
Pingsha Dong
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Compressive Stress ◽  
High Strain ◽  
Rolling Direction ◽  
Pure Titanium ◽  
Element Analysis ◽  
One Dimensional ◽  
Specimen Diameter ◽  
Taylor Impact

High strain rate mechanical properties of this material are required for the structural design of ship components for advanced naval applications. Taylor cylinder specimens were machined from pure titanium plate stock proposed for use in ship building. Since the specimens were machined from plate stock, it was assumed that the processing of the plate induced anisotropic behavior. To assure that all the effects would be captured by the tests, specimens were machined in the rolling direction, transverse direction, and 45° to the rolling direction in the plane of the plate. Indeed, distinct differences were observed in the rolling and transverse directions. Specimens in the 45° direction also showed the unsymmetrical deformation field that is associated with anisotropy. There was modest anisotropy in the thickness direction. However, the analysis of the data from the tests required corrections to accommodate this effect. Data from these tests can be reduced using two distinct methods; a one-dimensional theory and a finite element analysis with a conventional constitutive model adjusting the free parameters until the specimen geometry is matched. While the second method usually produces excellent results, we will employ a one-dimensional analysis that was proposed several years ago by one of the authors in this paper. In order to effectively apply such a theory, very low scale specimens, in this case 0.164-inch diameter, are required. The use of such low diameter specimens demands accurate measurement of the specimen profile. The recovered specimens were measured with a laser micrometer and the results were used to find estimates of quasi-static compressive stress and compressive stress at strain rates exceeding 104/sec. Some scatter in the data from these tests was observed. This was mostly due to some variations in the initial specimen diameter. Pure titanium presents a machining challenge for conventional equipment, when a tolerance of a thousandth of an inch is required. The scatter in Taylor cylinder data can be mitigated by conducting a large number of tests. However, in this case, many of the specimens that did not meet the criteria for success were discarded. Nevertheless, the results are very convincing.

Material Properties as Indicators of Machining Behavior

1999 ◽  
Author(s):  
Robin Stevenson
Keyword(s):  
High Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Material Properties ◽  
High Strain ◽  
Temperature Data ◽  
Test Procedures ◽  
High Temperature Data ◽  
Conventional Material

Abstract This paper demonstrates that the material properties developed using conventional material test procedures can be consistent with those developed during machining. However if extensive extrapolation is required to develop the high strain/high strain rate/high temperature data characteristic of machining, it is important to ensure that no change in deformation mechanism occurs over the extrapolation range. If such a mechanism change does occur the extrapolated data will be invalid.

Effect of Isothermal Aging and High Strain Rate on Material Properties of Innolot

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Isothermal Aging ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Strain Rates ◽  
Full Field

Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Tin-Silver-Copper (Sn-Ag-Cu or SAC) family of alloys like SAC105, SAC305 etc. Recent studies have highlighted the detrimental effects of isothermal aging on the material properties of these alloys. SAC alloys have shown up to 50% reduction in their initial elastic modulus and ultimate tensile strength within a few months of elevated temperature aging. This phenomenon has posed a severe design challenge across the industry and remains a road-block in the migration to Pb-free. Multiple compositions with additives to SAC have been proposed to minimize the effect of aging and creep while maintaining the melting temperatures, strength and cost at par with SAC. Innolot is a newly developed high-temperature, high-performance lead-free substitute by InnoRel™ targeting the automotive electronics segment. Innolot contains Nickel (Ni), Antimony (Sb) and Bismuth (Bi) in small proportions in addition to Sn, Ag and Cu. The alloy has demonstrated enhanced reliability under thermal cycling as compared to SAC alloys. In this paper, the high strain rate material properties of Innolot have been evaluated as the alloy ages at an elevated temperature of 50°C. The strain rates chosen are in the range of 1–100 per-second which are typical at second level interconnects subjected to drop-shock environments. The strain rates and elevated aging temperature have been chosen also to correspond to prior tests conducted on SAC105 and SAC305 alloys at this research center. This paper presents a comparison of material properties and their degradation in the three alloys — SAC105, SAC305 and Innolot. Full field strain measurements have been accomplished with the use of high speed imaging in conjunction with Digital Image Correlation (DIC). Ramberg-Osgood non-linear model parameters have been determined to curve-fit through the experimental data. The parameters have been implemented in Abaqus FE model to obtain full-field stresses which correlates with contours obtained experimentally by DIC.

scholarly journals Variations in Hardness with Position In One Dimensionally Recovered Shock Loaded Metals

2018 ◽  
Vol 183 ◽  
pp. 02013 ◽  
Author(s):  
G. Whiteman ◽  
D.L. Higgins ◽  
B. Pang ◽  
J.C.F. Millett ◽  
Y-L. Chiu ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Shock Loading ◽  
Mechanical Response ◽  
High Strain ◽  
Cold Work ◽  
Constitutive Models ◽  
Target Assembly ◽  
One Dimensional ◽  
The Impact

The microstructural and mechanical response of materials to shock loading is of the utmost importance in the development of constitutive models for high strain-rate applications. However, unlike a purely mechanical response, to ensure that the microstructure has been generated under conditions of pure one dimensional strain, the target assembly requires both a complex array of momentum traps to prevent lateral releases entering the specimen location from the edges and spall plates to prevent tensile interactions (spall) affecting the microstructure. In this paper, we examine these effects by performing microhardness profiles of shock loaded copper and tantalum samples. In general, variations in hardness both parallel and perpendicular to the shock direction were small indicating successful momentum trapping. Variations in hardness at different locations relative to the impact face are discussed in terms of the initial degree of cold work and the ability to generate and move dislocations in the samples.

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