Yield strength offset

Elements that can dissolve in copper, such as zinc, tin, and nickel for example, increase annealed strength by varying amounts depending on the element and the quantity in solution. The effect of selected solution hardening elements on tensile properties of annealed copper aUoys is iUustrated by the data in Table 4, where the yield strength is the stress at 0.2% offset strain in a tensile test. 

UNS designation Ahoy type" Product forms Electrical conductivity, %IACS Modulus of elasticity, CPa" Temper Tenshe strength, MPa Yield strength (0.2% offset), MPa Elongation, %... 

ANSI/ADA specification no. 38 requires a minimum yield strength (0.2% offset) of 250 MPa (36,000 psi) and a minimum elongation of 2% for ceramo—metallic alloys. 

AISI type Tensile strength, 1,000 lh /in Yield strength (0.2% offset), 1000 Ihf/in Elongation (in 2 in), % Reduction of area, % Hard- ness, Brinell Impact strength (Izod), ft-lhf... 

No. Material Nominal compo.sitioii Form and condition Yield. strength (0.2% offset), 1000 Ih/.sq in. Tensile strength, 1000 Ib/.sq m. EUongation, in 2 in., % Hardness, Brinell Comments... 

Mechanical Properties. The mechanical properties used for design shall be the minimum values allowed by the applicable material specification or shall be the minimum values determined by the manufacturer in accordance with the test procedures specified in ASTM A370 Methods and Definitions for Mechanical Testing of Steel Products, or by mill certification for mill products. The yield point shall be used in lieu of yield strength for those materials exhibiting a yield point. Yield strength shall be determined at 0.2% offset. 

For many polymers and metals the yield point is not clearly defined. In these cases the offset yield strength is used. To obtain this value, a line parallel to the linear portion of the curve is drawn such that... 

Temper Yield strength 0.2% offset, MPa" Ultimate tensile strength, MPa Elongation % in 50.8 mm Rockwell hardness Electrical conductivity, IACS %... 

The yield strength is the stress at which the stress-strain curve deviates from the initial straight line by a specified increment of strain. The yield strength corresponding to the load at B is based on the specified strain deviation or offset e. The value of e may be as low as 0,0001 inch (0.0025... 

The strain energy density (SED) method of determining the yield strength of materials described in this paper has two distinct advantages over, for example, the offset method. First, it is more reliable, and secondly, it is more related to the atomic/molecular mechanisms associated with the actual damage. 

Considering that the stress-strain curves for most metallic materials are not significantly affected by temperature and strain rate, the common choice of the 0.2 % offset yield strength may be acceptable. But stress-strain curves for adhesives vary greatly with relative humidity (RH), ambient temperature, strain rate, and adhesive type. Thus, an alternative method is needed for determining the yield strength of adhesives and other materials that exhibit a continuous transition from the elastic to the inelastic regions. The method should be based on the fundamental principles of mechanics of materials. 

Given the yield strength from step 6 and the elastic modulus from step 7, calculated with Eq 2 the v ue of the SED offset strain, 0.06 % (Table 3). 

Tables 2-4 show the effect of the dry/cold. moderate, and humid/hot environments on the tensile properties of the adhesive FM 300K tested at the 10 "/s. lO /s. and lO Vs strain rates, respectively. The values of the yield strength, the yield strain, and the offset obtained with the SED method and the corresponding values from the 0.2 % offset method are shown. The tensile strength, rupture strain, and elastic modulus are provided for information. On average, the time to rupture of the specimens tested at the lO /s, lO /s, and lO Vs strain rates were 4 seconds. 6 minutes, and 15 hours, respectively. The data are listed in ascending order of yield strength. The tensile properties listed in parentheses at the bottom of each cell are averages for replicate specimens. For ease of comparison, these averages are summarized in Table 5.

All but four of the fifty specimens have yield strengths and offset strains calculated with the SED method that are equal to or lower than the values from the 0.2 % offset method. In the three environments (dry/cold, moderate, and humid/hot) the average yield strengths are ... 

Specimen ID. Yield Strength (MPa) Yield Strain Offset (%) Yield Strength (MPa) Yield Strain Tensile Strength (MPa) Rupture Strain Elastic Modulus (MPa)... 

---